Applied Surface Science (v.263, #C)
Editorial Board (ii).
Effects of surface acidities of MCM-41 modified with MoO3 on adsorptive desulfurization of gasoline by Xinchao Shao; Xiaotong Zhang; Wenguang Yu; Yuye Wu; Yucai Qin; Zhaolin Sun; Lijuan Song (1-7).
► The MoO3-MCM-41 samples prepared by spontaneous monolayer dispersion and impregnation with a different MoO3 filling have been studied. ► The relative concentration of hydroxyl groups present on before and after containing MoO3 samples was monitored by in situ FTIR to speculate the bonding style of MoO3 and MCM-41. ► The surface acidities of the MoO3-MCM-41 adsorbents were investigated systematically and correlated with the desulfurization performance.A series of MCM-41 samples containing molybdenum oxide as active species in the mesoporous channels loaded by spontaneous monolayer dispersion (SMD) and impregnation (IM) have been prepared and characterized using XRD, N2 adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR) and intelligent gravimetric analyzer (IGA). The relative number of hydroxy on the adsorbents was investigated by in situ FTIR. Surface acidities of the adsorbents were studied by infrared spectroscopy of adsorbed pyridine and correlated with reactivity for adsorptive desulfurization. The IGA technique was employed to investigate adsorption behavior of thiophene and benzene on the adsorbents at 303 K. It is shown that MoO3 can be highly dispersed up to 0.2 g g−1 in the MCM-41 channels by the SMD strategy with the ordered mesoporous structure of the MoMM samples remaining intact. The ordered mesostructure of MCM-41 is, however, destroyed at higher MoO3 contents of 0.26 and 0.32 g g−1 with particle sizes of 1.2 nm and 3.6 nm, respectively, observed. For the MoMI(0.2) sample prepared by the IM method, the aggregation of the MoO3 particles takes place with a particle size of 6.5 nm obtained. The results are also revealed that the dispersion extent of the MoO3 species is related to the abundant surface hydroxy of MCM-41. The host species and guest species undergo solid-state reaction to form Si―O―Mo bonds in the mixtures which enhance both the Lewis acid and Brönsted acid of the samples. It has been concluded that the surface acidities of the sorbents contributes to the desulfurization performance which has also been investigated in this study. The octahedral coordinated species (Mo7O24 6−) are the adsorptive active species for desulfurization compared with the tetrahedral coordinated ones (MoO4 2−).
Keywords: MoO3; MCM-41; Adsorptive desulfurization; Spontaneous monolayer dispersion in situ FTIR; Pyridine;
Water-based preparation of highly oleophobic thin films through aggregation of nanoparticles using layer-by-layer treatment by Shingo Nishizawa; Seimei Shiratori (8-13).
► The layer-by-layer process was applied to the surface of TiO2 nano particles. ► This method can control the particle's aggregation and can generate micro-scale rough structure. ► Micro–nano scale rough structure using LBL process shows the high oleophobicity. ► This method may have industrial advantages because it is aqueous based.The layer-by-layer (LBL) adsorption technique has potential for controlling the surface wettability. In this study, we controlled surface wettability between “superhydrophobic and oleophobic” and “hydrophobic and oleophilic” by LBL process on TiO2 nanoparticle with hydrophobic polymer and hydrophilic polymer. From the cast coating with LBL process on TiO2 nanoparticle, the surface showed “superhydophobic and oleophobic” when the top surface was hydrophobic polymer, on the other hand, the surface showed “hydrophobic and oleophilic” when the top surface was hydrophilic polymer. The LBL process also affected to the structure of TiO2 nanoparticle/polymer composite, and TiO2 nanoparticle were aggregated with polymers in LBL process. In the condition of the aggregated diameter of TiO2 nanoparticle/polymer composite around 10 μm in solution, the oleohobicity of spray coated film was enhanced with its hierarchical structure (static contact angles of rapeseed oil of 150° and hexadecane of 145°) “Superhydrophobic and high oleophobic” surfaces generated from all water-based dispersions are expected for application in technologies that need to avoid organic solvents.
Keywords: Superhydrophobic; Oleophobic; Amphiphobic; Surface wettability; Layer-by-layer; Nanoparticles; Copolymer; Fluoropolymer; Spray; Hierarchical structure;
The growth and photocatalytic property of ZnO nanofibers synthesized by atom layer deposition using PVP nanofibers as templates by Xuan Fang; Shuang Li; Xiaohua Wang; Fang Fang; Xueying Chu; Zhipeng Wei; Jinhua Li; Xinying Chen; Fei Wang (14-17).
► PVP nanofibers were synthesized by electrospinning and used as templates. ► ZnO nanofibers were synthesized on PVP by ALD method. ► By annealing treatment, the different morphologies of ZnO nanofibers could be formed. ► ZnO nanofibers show higher photocatalytic activity due to more surface-to-volume ratio.Zinc oxide (ZnO) nanofibers were synthesized by atom layer deposition (ALD) using polyvinylpyrrolidone (PVP) fibers as template. It was found that the morphologies of ZnO nanofibers were the same as PVP nanofibers. By annealing treatment, the different morphologies of ZnO nanofibers could be formed with the decomposition of PVP nanofibers which were characterized by means of transmission electron microscopy (TEM) and room temperature Raman spectra. The crystal and the optical properties can be also improved. The photocatalytic activities of the as-growth ZnO samples were evaluated in the photocatalytic degradations of aqueous solutions of methyl orange at room temperature. ZnO nanofibers showed higher photocatalytic activity due to more surface-to-volume ratio.
Keywords: ZnO; PVP; Nanofibers; Template; ALD;
Electrodeposition of diamond-like carbon films on titanium alloy using organic liquids: Corrosion and wear resistance by Tiago Falcade; Tobias Eduardo Shmitzhaus; Otávio Gomes dos Reis; André Luis Marin Vargas; Roberto Hübler; Iduvirges Lourdes Müller; Célia de Fraga Malfatti (18-24).
► The electrodeposition may be conducted at room temperature. ► The DLC films have good resistance to corrosion in saline environments. ► The films have lower coefficient of friction than the uncoated substrate. ► The abrasive wear protection is evident in coated systems.Diamond-like carbon (DLC) films have been studied as coatings for corrosion protection and wear resistance because they have excellent chemical inertness in traditional corrosive environments, besides presenting a significant reduction in coefficient of friction. Diamond-like carbon (DLC) films obtained by electrochemical deposition techniques have attracted a lot of interest, regarding their potential in relation to the vapor phase deposition techniques. The electrochemical deposition techniques are carried out at room temperature and do not need vacuum system, making easier this way the technological transfer. At high electric fields, the organic molecules polarize and react on the electrode surface, forming carbon films. The aim of this work was to obtain DLC films onto Ti6Al4V substrate using as electrolyte: acetonitrile (ACN) and N,N-dimethylformamide (DMF). The films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, potentiodynamic polarization and wear tests. The results show that these films can improve, significantly, the corrosion resistance of titanium and its alloys and their wear resistance.
Keywords: DLC; Electrodeposition; Ti6Al4V; Corrosion; Wear;
Observation of pitting due to field enhanced surface absorption during laser assisted cleaning of translucent particulates off metal surfaces by J. Padma Nilaya; M.B. Sai Prasad; Dhruba J. Biswas (25-28).
► Laser assisted cleaning. ► Field enhanced surface absorption. ► Experimental evidence of surface pitting.The field enhanced surface absorption that occurs as a result of focusing of the incident radiation through transparent/semi-transparent contaminant particulates, in addition to their removal, can also leave its signature on the surface in the form of pitting. This has been experimentally verified in case of removal of CsNO3 particulates off stainless steel surface with sub-nanosecond to nanosecond pulses of 1064 nm, 532 nm, and 355 nm wavelengths for which the particulates are semi-transparent. The threshold fluence for such pit formation has been studied as a function of both wavelength and pulse duration of the coherent radiation and was always found to be much higher than the cleaning threshold. Qualitative explanations have been offered to the observed experimental results.
Keywords: Laser cleaning; Field enhanced surface absorption; Surface pitting;
Electrochemical investigation of passive film in pre-deformation AISI 304 stainless steels by Lv Jinlong; Luo Hongyun (29-37).
► With the increasing of the strain α′-martensite was gradually increasing. ► The acceptor density of all the specimens was always more than donor density in borate buffer solution. ► ɛ-Martensite had a detrimental effect on passive properties in borate buffer solution. ► The detrimental effect of α′-martensite was more prominent in borate buffer solution with Cl−.The electrochemical measures in deformed AISI 304 stainless steels ranged from 0% to 24% were investigated. With the increasing of the strain α′-martensite was gradually increasing. Moreover, the morphologies and densities of dislocations changed with increasing strain. The Mott–Schottky plots showed that the maximum total of donor and acceptor densities in passive film occurred in borate buffer solution when ɛ-martensite was most, while in borate buffer solution with 5000 ppm Cl− the maximum total of donor and acceptor densities occurred when the content of α-martensite was most. These results were proven by further impedance spectroscopy experiments.
Keywords: Stainless steel; TEM; Passive film; Corrosion;
Study on synthesis of ultrafine Cu–Ag core–shell powders with high electrical conductivity by Yu-hsien Peng; Chih-hao Yang; Kuan-ting Chen; Srinivasa R. Popuri; Ching-Hwa Lee; Bo-Shin Tang (38-44).
► This synthesis method is relatively facile, novel and eco-friendly. ► Toxic agents were not used for chelating agent, reductant or dispersant in our method. ► The reaction can under room temperature for energy saving purpose. ► Cu–Ag core–shell powders with homogeneous cover-silver layer. ► The resistivity of Cu–Ag core–shell powders has the same value as the pure silver.Cu–Ag composite powders with high electrical conductivity were synthesized by electroless plating of silver sulfate, copper powders with eco-friendly sodium citrate as reducing agent, dispersant and chelating agent in an aqueous system. The influences of sodium citrate/Ag ratio on Ag coatings of Cu powders were investigated. Ag was formed a dense coating on the surface of Cu powders at a molar ratio of sodium citrate/Ag = 0.07/1. SEM showed an uniformity of Ag coatings on Cu powders. SEM-EDX also revealed that Cu cores were covered by Ag shells on the whole. The surface composition analysis by XPS indicated that without Cu or Ag atoms in the surface were oxidized. The resistivity measurements of Cu–Ag paste shows that they have closer resistivity as the pure silver paste's after 250 °C for 30 min heat-treatment (2.55 × 10−4 Ω cm) and 350 °C for 30 min heat-treatment (1.425 × 10−4 Ω cm).
Keywords: Composite materials; Fourier transform infrared spectroscopy; X-ray diffraction topography; Electrical conductivity;
Comparison of structures and hydrophobicity of femtosecond and nanosecond laser-etched surfaces on silicon by Bao-jia Li; Ming Zhou; Wei Zhang; George Amoako; Chuan-yu Gao (45-49).
► Gratings with induced structures on silicon surfaces were etched by fs and ns laser. ► The fs laser etched structures are smoother and with smaller top widths of grooves. ► Etching by fs laser can result in better micro-nanoscale hierarchical structures. ► The hierarchical structures contribute a lot to the enhancement of hydrophobicity. ► This work provides a basis for fabricating silicon-based superhydrophobic surfaces.The rough micro- and nano- scale hierarchical structures on surfaces of materials render the surfaces superhydrophobic. In this context, we obtain both microscale grating structures and nanoscale induced structures (with some splashes) on silicon-based surfaces by means of laser etching and inducing. Our research focuses on the differences of morphology and hydrophobicity for silicon-based microstructured surfaces fabricated by femtosecond laser and nanosecond laser. The results indicated that the grating microstructures fabricated by femtosecond laser are smoother and with smaller top width of groove. Moreover, better micro-nanoscale hierarchical structures can be obtained by femtosecond laser overlapped etching for many times. On the surface with such structures, the water droplet is at Cassie–Baxter state and the contact angle (CA) is 144.6°, which indicates that the surface is middle hydrophobic. This work may provide an effective approach for fabrication of self-cleaning functional surfaces and devices.
Keywords: Laser; Silicon; Grating microstructures; Hydrophobicity;
High-quality GaN nanowires grown on Si and porous silicon by thermal evaporation by L. Shekari; A. Ramizy; K. Omar; H. Abu Hassan; Z. Hassan (50-53).
► A new kind of substrate (porous silicon) was used. ► Also this research introduces an easy and safe method to grow high quality GaN NWs. ► This is a new growth process to decrease the cost, complexity of growth of GaN NWs. ► It is a controllable method to synthesize GaN NWs by thermal evaporation.Nanowires (NWs) of GaN thin films were prepared on as-grown Si (1 1 1) and porous silicon (PS) substrates using thermal evaporation method. The film growth produced high-quality wurtzite GaN NWs. The size, morphology, and nanostructures of the crystals were investigated through scanning electron microscopy, high-resolution X-ray diffraction and photoluminescence spectroscopy. The NWs grown on porous silicon were thinner, longer and denser compared with those on as-grown Si. The energy band gap of the NWs grown on PS was larger than that of NWs on as-grown Si. This is due to the greater quantum confinement effects of the crystalline structure of the NWs grown on PS.
Keywords: Thermal evaporation growth; GaN nanowires; Porous silicon;
Flexible free-standing TiO2/graphene/PVdF films as anode materials for lithium-ion batteries by H.M. Ren; Y.H. Ding; F.H. Chang; X. He; J.Q. Feng; C.F. Wang; Y. Jiang; P. Zhang (54-57).
► Flexible TiO2/graphene electrode was prepared by a solvent evaporation technique. ► PVdF was used as substance to support the TiO2/graphene active materials. ► The flexible films can be employed as anode materials for Li-ion battery.Graphene composites were prepared by hydrothermal method using titanium dioxide (TiO2) adsorbed graphene oxide (GO) sheets as precursors. Free-standing hybrid films for lithium-ion batteries were prepared by adding TiO2/graphene composites to the polyvinylidene fluoride (PVdF)/N-methyl-2-pyrrolidone (NMP) solution, followed by a solvent evaporation technique. These films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and various electrochemical techniques. Flexible films show an excellent cycling performance, which was attributed to the interconnected graphene conducting network, which depressed the increasing of electric resistance during the cycling.
Keywords: TiO2/graphene composites; Flexible electrodes; Lithium-ion batteries;
Synthesis and characterization of multi-element oxynitride semiconductor film prepared by reactive sputtering deposition by Ruei-Sung Yu; Rong-Hsin Huang; Chih-Ming Lee; Fuh-Sheng Shieu (58-61).
► The structural and semiconductor properties of multi-element oxide and oxynitride films were examined. ► The results revealed that (TiVCrZrTa)1−x O x and (TiVCrZrTa)1−x−y N y O x are amorphous. ► In the three-dimensional structure, anions act as cores surrounded by cations in a random and homogeneous dispersion. ► The (TiVCrZrTa)1−x−y N y O x film is an n-type semiconductor with a conductivity of 2.75 × 10−2 (Ω cm)−1. ► The indirect band gap of the (TiVCrZrTa)1−x−y N y O x film was 1.95 eV.This study concerns the use of reactive magnetron sputtering to prepare (TiVCrZrTa)-based oxide and oxynitride films. (TiVCrZrTa)1−x O x and (TiVCrZrTa)1−x−y N y O x films were prepared, and were found to be amorphous and free of multi-phase structure. Cations and anions in such structures were arranged in a random homogeneous dispersion. The introduction of nitrogen atoms into (TiVCrZrTa)1−x O x yields (TiVCrZrTa)1−x−y N y O x , which has a reduced oxidation state and thus, an increased number of the valence electrons. The (TiVCrZrTa)1−x−y N y O x film is an n-type semiconductor, with an indirect band gap of 1.95 eV, and a carrier concentration (N) and conductivity (σ) of 1.01 × 1019 cm−3 and 2.75 × 10−2 (Ω cm)−1, respectively.
Keywords: Semiconductor; Structure; Multi-element; Thin film; Oxynitride;
AlN films prepared on 6H–SiC substrates under various sputtering pressures by RF reactive magnetron sputtering by Xu-Ping Kuang; Hua-Yu Zhang; Gui-Gen Wang; Lin Cui; Can Zhu; Lei Jin; Rui Sun; Jie-Cai Han (62-68).
► High purity AlN films were prepared on 6H–SiC substrates by RF reactive magnetron sputtering. ► Highly c-axis oriented AlN films (single crystal like) were grown on SiC at 300 °C. ► The crystalline structure of the films are strongly influenced by the sputtering pressures. ► The deposited AlN films have a smooth surface (R a ≤ 2.0 nm).In this paper, we studied the growth of AlN films on 6H–SiC substrates under various sputtering pressures by RF reactive magnetron sputtering at low deposition temperature (300 °C). The composition, chemical structure and oxygen impurity of the deposited films were investigated by X-ray photoelectron spectroscopy (XPS). It is suggested that the Al/N ratio of the high purity film is 1.13:1 which is very close to the stoichiometric value (1:1), and a few oxygen impurities exist in the grain boundaries in the form of Al―O bonding. The two-dimensional X-ray diffraction (2D-XRD) was used to study the crystal structure of the deposited films. 2D-XRD patterns indicate that a low sputtering pressure favor the growth of AlN film with c-axis oriented, and a highly c-axis oriented AlN film resemble single crystal structure was prepared at the sputtering pressure of 0.3 Pa. Surface morphology of the deposited films were investigated by SEM and AFM. The images show that the surface morphology of the films with (0 0 0 2) preferred orientation present a pebble-like structure, and the grain size and surface roughness of the films decrease with increasing the sputtering pressure.
Keywords: AlN film; c-Axis oriented; Reactive magnetron sputtering; X-ray photoelectron spectroscopy; Two-dimensional X-ray diffraction;
Fabrication of TiO2/SiO2 multilayer film structure by the sol–gel process with efficient thermal treatment methods by Koohee Han; Jung Hyeun Kim (69-72).
► TiO2 films morphologies on the hydrophobic SiO2 films. ► The TiO2/SiO2 multilayer structure formation on the hydrophilic SiO2 film. ► Heating-up period included in the sintering process. ► Residual alkoxy groups removed effectively with the gradual-sintering method. ► The TiO2/SiO2 multilayer fabricated at 300 °C with the heating-up period.Multilayer structure of thin films by the sol–gel process attracts great attention for versatile applications. However, the multilayer structure often shows undesirable morphologies such as cracks or delaminations resulted from non-wettability of the coating solution with the pre-deposited hydrophobic layer, especially in the case of SiO2 layers. The hydrophobic surface is originated from residual alkoxy groups in the layer after sintering step. For the sintering process, introducing the heating-up period from the room temperature to the target temperature is very effective in removing residual alkoxy groups from the SiO2 film by hydrolysis with remaining water molecules. The well-defined TiO2/SiO2 multilayer structure is successfully fabricated at a sintering temperature of 300 °C by forming a hydrophilic SiO2 layer with the heating-up period.
Keywords: Thin films; Multilayer structure; Sol–gel preparation; Hydrophobic; Hydrophilic; Thermal treatment;
Self-assembly of dendronized non-planar conjugated molecules on a HOPG surface by Yang Yang; Xinrui Miao; Gang Liu; Li Xu; Tingting Wu; Wenli Deng (73-78).
Display Omitted► The conjugated moiety in dendronized non-planer molecules tends to arrange edge-on on the surface, revealing the importance of π–π stacking. ► Different substitution of the molecules leads to structural changes in the arrangement due to the different intermolecular interactions. ► It could contribute to an understanding in issues related to the intermolecular interactions and the performance of photovoltaic devices.Two-dimensional self-assembly of a series of dendronized molecules with different functional groups were observed on the highly oriented pyrolitic graphite (HOPG) surface by scanning tunneling microscopy (STM). The solution evaporation of these molecules on HOPG surfaces under ambient conditions results in the formation of self-organized monolayers. STM images demonstrate that the dendronized conjugated moiety in these molecules all adopt an edge-on arrangement on the HOPG surface, revealing the importance of π–π stacking interactions. The molecules with a hydroxyl as the substituent group adsorb on the HOPG surface with an ordered lamellar nanopattern resulting from the intermolecular hydrogen bonding. The molecules without alkyl chain are perpendicular to the HOPG surface, in a face-to-face card-stack fashion by π–π stacking. Alkyl chain assisted molecules adsorb on the HOPG surface with one side chain arrangement by tail-to-tail fashion. Our results demonstrate that the balance between different molecule–molecule and molecule–substrate interactions can be easily influenced by a small structural change in one of the components of the supramolecular assemblies resulting in different organized patterns on the solid surface.
Keywords: Self-assembly; Scanning tunneling microscopy; Edge-on;
The adsorption of acrolein on a Pt (1 1 1): A study of chemical bonding and electronic structure by S. Pirillo; I. López-Corral; E. Germán; A. Juan (79-85).
► Study of acrolein/Pt (1 1 1) adsorption using ab-initio and semiempirical methods. ► Geometry optimization and DOS curves were carried out using VASP code. ► Study of chemical bonding evolution using COOP and OP analysis. ► After adsorption Pt―Pt, C＝O and C＝C bonds are weakened. ► η 3-cis and η 4-trans most stable adsorption modes, η 1-trans less favored one.The adsorption of acrolein on a Pt (1 1 1) surface was studied using ab-initio and semiempirical calculations. Geometry optimization and densities of states (DOS) curves were carried out using the Vienna Ab-initio Simulation Package (VASP) code. We started our study with the preferential geometries corresponding to the different acrolein/Pt (1 1 1) adsorption modes previously reported. Then, we examined the evolution of the chemical bonding in these geometries, using the crystal orbital overlap population (COOP) and overlap population (OP) analysis of selected pairs of atoms. We analyzed the acrolein intramolecular bonds, Pt (1 1 1) superficial bonds and new molecule―surface formed bonds after adsorption. We found that Pt―Pt bonds interacting with the molecule and acrolein C＝O and C＝C bonds are weakened after adsorption; this last bond is significantly linked to the surface. The obtained C―Pt and O―Pt OP values suggest that the most stable adsorption modes are η 3-cis and η 4-trans, while the η 1-trans is the less favored configuration. We also found that C p z orbital and Pt p z and d z 2 orbitals participate strongly in the adsorption process.
Keywords: Bonding; Acrolein; DFT; Pt (1 1 1); Adsorption;
Factors affecting the wettability of different surface materials with vegetable oil at high temperatures and its relation to cleanability by Saranya Ashokkumar; Jens Adler-Nissen; Per Møller (86-94).
Plot of cos θ versus temperature for metal and ceramic surfaces where cos θ rises linearly with increase in temperature.Display Omitted► cos θ of olive oil on different surface materials rises linearly with increase in temperature. ► Slopes are much higher for quasicrystalline and polymers than for ceramics. ► Increase in surface roughness and surface flaws increases surface wettability. ► Contact angle values gave information for grouping easy-clean polymers from other materials. ► Contact angle measurements cannot directly estimate the cleanability of a surface.The main aim of the work was to investigate the wettability of different surface materials with vegetable oil (olive oil) over the temperature range of 25–200 °C to understand the differences in cleanability of different surfaces exposed to high temperatures in food processes. The different surface materials investigated include stainless steel (reference), PTFE (polytetrafluoroethylene), silicone, quasicrystalline (Al, Fe, Cr) and ceramic coatings: zirconium oxide (ZrO2), zirconium nitride (ZrN) and titanium aluminum nitride (TiAlN). The ceramic coatings were deposited on stainless steel with two different levels of roughness. The cosine of the contact angle of olive oil on different surface materials rises linearly with increasing temperature. Among the materials analyzed, polymers (PTFE, silicone) gave the lowest cos θ values. Studies of the effect of roughness and surface flaws on wettability revealed that the cos θ values increases with increasing roughness and surface flaws. Correlation analysis indicates that the measured contact angle values gave useful information for grouping easy-clean polymer materials from the other materials; for the latter group, there is no direct relation between contact angle and cleanability. In addition to surface wettability with oil many other factors such as roughness and surface defects play an essential role in determining their cleanability.
Keywords: Wettability; Different surface materials; Vegetable oil; Cleanability; High temperatures; Roughness and surface defects;
Effects of TiO x seeding layer upon the growth and light emission properties of ZnO nanowires by Ying Cao; Huidan Zeng; Fan Zhang; Yanglong Chen; Liu Hang; Zhihong Tang; Qi Jiang; Xianying Wang (95-99).
► Vertical ZnO NWs arrays were prepared on TiO x seed layers via hydrothermal method. ► TiO x seeds layers can improve the crystallinity and orientation of ZnO NWs arrays. ► The photoluminescence spectra of ZnO NWs grown on the 1 nm TiO x seed layer exhibit enhanced UV emission. ► The visible emissions are also enhanced, due to the TiO x having great number of structural defects.Oriented ZnO nanowire (NW) arrays were fabricated via hydrothermal method using TiO x films as the seeding layer. Structural and morphological analysis indicates that the TiO x seeding layer can greatly improve the crystallinity and alignments of ZnO NWs. The photoluminescence (PL) spectra of ZnO NWs grown on the 1 nm TiO x seed layer exhibit enhanced UV emission. Improved growth of ZnO NWs on TiO x seed layer may facilitate the fabrication of high performance dye sensitized solar cell devices.
Keywords: ZnO nanowires arrays; TiO x seed layer; Improved growth; Enhanced emission;
Structural, catalytic and magnetic properties of Cu1−X Co X Fe2O4 by Sarah Briceño; Hector Del Castillo; V. Sagredo; Werner Bramer-Escamilla; Pedro Silva (100-103).
► Cu1−X Co X Fe2O4 ferrite synthesized by sol–gel auto-combustion method. ► Structural identification, magnetic and catalytic properties were investigated. ► Characterization by TGA, DTA, XRD, SEM, TEM and VSM techniques. ► Magnetic properties decrease with the increase of Cu2+ doping. ► The selective conversion to N2 is higher for Cu–Co mixed ferrites.Copper substituted cobalt ferrite Cu1−X Co X Fe2O4 (0 ≤x ≤ 1) have been synthesized using sol–gel auto combustion method with citric acid as fuel. Structural identification, magnetic and catalytic properties were investigated using thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and their application in the selective catalytic reduction of NOx were studied. Analysis of structural properties reveals that all samples have cubic spinel structure. Room temperature magnetic hysteresis measurements as a function of magnetic field infer that the magnetic properties decrease with Cu2+ doping which may be due to the difference of the magnetic moment of Cu2+ and Co2+ ions. The higher activity of the samples in NO selective reduction to N2 occurs at 350 °C, reaching a maximum of 38% NO conversion and 95% of selective conversion to N2. The compositions containing both Cu2+ and Co2+ ions are more active to the products selectivity to N2, suggesting a synergistic effect on the active surface of ferrite and the effect of Co2+ is more pronounced than Cu2+ towards NO conversion.
Keywords: Nanostructured materials; Sol–gel; Ferrites; Catalytic activity; Magnetic properties;
Control of the lateral interactions of immobilized proteins using surface nanoporous-patterning by Changhoon Chai; Paul Takhistov (104-110).
► Lateral interactions affect the behavior of proteins during protein immobilization. ► Protein immobilization on planar surface produces heterogeneous protein clusters. ► Lateral interactions can be controlled using surface nanoporous-patterning. ► Protein array on a nanoporous surface are more biochemically functional than array on a planar surface.Protein immobilization on a solid surface is a consequence of complex physical processes at liquid–solid interfaces. Lateral interactions include these physical processes and affect the behavior of proteins at the interfaces. Protein immobilization on planar surfaces frequently produces randomly distributed and irregularly sized protein clusters having large lateral interactions that impair the biochemical functionalities of immobilized proteins. This study discusses control of lateral interactions via nanoporous-patterning of the solid surface. The size of protein clusters and lateral interactions can be controlled via nanoporous-patterning as protein immobilization on a nanoporous surface is confined to the surface that is not occupied by nanopores. Protein clusters on a nanoporous surface are more biochemically functional than clusters on a planar surface.
Keywords: Protein immobilization; Lateral interactions; Protein nanoarrays; Nanoporous structure; Aluminum anodization; Impedance;
Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties by Jean-Christophe Orlianges; Aurelian Crunteanu; Arnaud Pothier; Therese Merle-Mejean; Pierre Blondy; Corinne Champeaux (111-114).
► We have grown TiO2 thin films by PLD on c-sapphire substrate with pre-patterned out-plane capacitor structures. ► Raman and XRD analyses indicate an evolution from “amorphous” to anatase and rutile phase. ► Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements. ► Permittivity measurements reveal high dielectric constant ɛ r = 120 of 600 °C-grown TiO2 thin films.Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30–120, showing the potentialities of the deposited material for capacitive switches applications.
Keywords: Titanium dioxide; Pulsed laser deposition; Surface characterization; Dielectric permittivity; Ellipsometry; Raman;
Surface studies of microcrystalline chitosan/poly(vinyl alcohol) mixtures by Katarzyna Lewandowska (115-123).
► The surface properties were investigated by AFM, SEM and FTIR. ► The AFM images showed the lamellar structure of PVA in the blend. ► SEM microscopy confirmed the existence of microphase separation of components. ► FTIR analysis showed the existence of a weak interaction.In the present study, the surface properties of microcrystalline chitosan (MCCh), poly(vinyl alcohol) (PVA) and MCCh/PVA blends (made from acetic acid solutions with the MCCh concentration ranging from 20% to 80%) have been studied by the tapping-mode atomic force microscopy (AFM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The changes of topography images are considered by determining the root mean square (RMS, R q) deviation in the image data. For PVA samples, the transition between adjacent lamellae occurs through holes, islands, and bicontinuous structures. The AFM images showed also the lamellar structure of PVA in the blend. The crystalline topography of MCCh/PVA film surface suggests the presence of PVA on the top surface. The FTIR spectra of film blends, in the amide I and II region of MCCh and the hydroxyl stretching bands of PVA have been analyzed. FTIR analysis showed the existence of a weak interaction of the hydroxyl or amino groups of microcrystalline chitosan with hydroxyl groups of PVA.
Keywords: Microcrystalline chitosan; Poly(vinyl alcohol); FTIR analysis; AFM and SEM microscopy;
Direct fabrication of organic carbon coated VO2(B) (VO2(B)@C) core–shell structured nanobelts by one step hydrothermal route and its formation mechanism by Yifu Zhang; Juecheng Zhang; Yalan Zhong; Lei Yu; Yuan Deng; Chi Huang; Xinghai Liu (124-131).
Display Omitted► VO2(B)@C core–shell nanobelts were synthesized by a one-step hydrothermal route. ► The effect of glucose and reaction time was briefly discussed. ► Glucose played a dual role, namely as a reductant and as a carbon precursor. ► The possible formation mechanism of VO2(B)@C was proposed.Organic carbon coated vanadium dioxide (VO2(B)@C) core–shell structured nanobelts were successfully synthesized using V2O5 and glucose solution as the starting materials by a facile one-step hydrothermal route. The as-obtained core–shell materials were characterized by scanning electron microscope, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectrometer, elemental analysis, Fourier transform infrared spectroscopy and Raman measurements. Some parameters, such as, the concentration of glucose and the reaction time, were briefly discussed to disclose the formation process of VO2(B)@C core–shell structured nanobelts. Glucose played a dual role in the hydrothermal process, namely as a reductant to reduce V2O5 to VO2(B), and as a carbon precursor for the organic carbon shell. The proper quantity of glucose (i.g.: 0.27 g) was beneficial for the fabrication of VO2(B)@C. Furthermore, the possible formation mechanism of VO2(B)@C core–shell structured nanobelts was proposed.
Keywords: Nanocomposites; Core–shell structures; VO2(B)@C; Amorphous carbon; Chemical synthesis;
Preparation and characterization of lactate-intercalated Co–Fe layered double hydroxides and exfoliated nanosheet film with low infrared emissivity by Yunxia Zhu; Yuming Zhou; Tao Zhang; Man He; Yongjuan Wang; Xiaoming Yang; Yong Yang (132-138).
► We use ferrous, cobalt powders and lactic acid to synthesis lactate-intercalated Co–Fe layered double hydroxides successfully. ► A possible orientation of the intercalated lactate between the layers is carried out. ► The thin nanosheet film is fabricated and the surface is very smooth and flat. ► The infrared emissivity value of Co–Fe LDHs is lower than that of Zn–Al or Mg–Al LDHs, and the value is further reduced after forming a thin film.Lactate-intercalated Co–Fe layered double hydroxides (LDHs) were successfully prepared by coprecipitation and hydrothermal method. In this process, divalent metal ions as precursors can be obtained from the reduction reaction of lactic acid and metal powder (cobalt and ferrous). In order to obtain Fe3+, H2O2 (30%) was used to oxidize Fe2+. Meanwhile, the produced lactate was intercalated into the LDHs interlayers to compensate the positively charged layers. The as-synthesized LDHs were studied by element chemical analysis, powder X-ray diffraction (XRD), FT-IR spectroscopy, thermogravitry (TG) and differential scanning calorimetry (DSC), TEM. The results indicated that the basal spacing value of the LDHs was larger than that of lactate-intercalated Mg–Al or Zn–Al LDHs. It proved that the lactate anions were inserted into the gallery in the form of dimers which made it easy to be delaminated in water. The obtained nanosheets were deposited on the substrates to form the film which was characterized by TEM and AFM, and infrared emissivity value (8–14 μm) was also investigated. The infrared emissivity values of Co–Fe LDHs were lower than that of Zn–Al which took advantage of the special electronic structure in Co and Fe. Besides, the orderly structure and the reduction of the interfacial deficiency of the film made the values further reduced.
Keywords: Lactate; Co–Fe layered double hydroxides; Delamination; Nanosheet film;
Assembling three-dimensional nanostructures on metal surfaces with a reversible vertical single-atom manipulation: A theoretical modeling by Tian-Xing Yang; Xiang Ye; Lei Huang; Yi-Qun Xie; San-Huang Ke (139-142).
► We simulate the reversible vertical single-atom manipulations on several metal surfaces. ► We propose a method to predict whether a reversible vertical single-atom manipulation can be successful on several metal surfaces. ► A 3-dimensional Ni nanocluster is assembled on the Ni(1 1 1) surface using a Ni trimer-apex tip.We propose a theoretical model to show that pulling up an adatom from an atomic step requires a weaker force than from the flat surfaces of Al(0 0 1), Ni(1 1 1), Pt(1 1 0) and Au(1 1 0). Single adatom in the atomic step can be extracted vertically by a trimer-apex tip while can be released to the flat surface. This reversible vertical manipulation can then be used to fabricate a supported three-dimensional (3D) nanostructure on the Ni(1 1 1) surface. The present modeling can be used to predict whether the reversible vertical single-atom manipulation and thus the assembling of 3D nanostructures can be achieved on a metal surface.
Keywords: Vertical atom manipulation; Single crystal surface; Adatom; Computing simulations;
The role of small probability measure in the analysis about desulfurization limestone particles multi-fractal surface structure by Jianyu Shang; Zhongliang Liu; Songling Wang; Chunbo Wang; Yaofei Feng (143-148).
► Singular spectra, quality index spectra, general dimension spectra are equivalent. ► The small probability measure has better performance when q-factor is small. ► The small probability measure makes powders micro-structure clearer to distinguish. ► The limestone sorbent sample particles are in a good desulfurization state at 900 °C.The key of desulfurization is physical measure distribution on the surface of calcinated limestone particle. Temperature is an important factor that can influence the singularity of particles. Limestone samples were calcinated and analyzed by TGA at 800 °C and 900 °C f(α) − α and 1000 °C. The singular τ q − q spectrum and the quality index D q − q spectrum and the general dimension spectrum of particles surface measure distribution at different temperatures can be obtained while adopting multi-fractal theory after gray processing the SEM images of calcinated limestone particles. The change of small probability measure with q-factor was calculated. Experiment shows that those spectrums all can reflect the particle distribution appropriately, in addition, the full calcination at 900 °C has better homogeneity and regularity with more rich small-probability-measure and less sintering while there are insufficiency calcination at 800 °C and serious sintering at 1000 °C, so the phenomenon why the singularity α-index has wider range at the two temperatures is mainly because of the lack of the small probability set. The small probability measure can seriously influence the multi-fractal value on the surface of calcinated limestone particle, especially for a small q-factor.
Keywords: Desulfurization; Limestone particle; Small probability measure; Multi-fractal;
Development of high performance electroless Ni–P–HNT composite coatings by S. Ranganatha; T.V. Venkatesha; K. Vathsala (149-156).
► Novel Ni–P composites were prepared by incorporating Halloysite nanotubes. ► Mild steel specimens surface engineered by nickel using electroless technique. ► Incorporated halloysite nanotubes made nickel matrix highly corrosion resistant. ► HNT composite exhibits high hardness and largely reduces friction.Halloysite nanotubes (HNTs) of the dimension 50 nm × 1–3 μm (diameter × length) are utililized to fabricate the alloy composite by employing electroless/autocatalytic deposition technique. Electroless Ni–P–HNT binary alloy composite coatings are prepared successfully on low carbon steel. These nanotubes were made to get inserted/incorporated into nickel matrix and corresponding composites are examined for their electrochemical, mechanical and tribological performances and compared with that of plain Ni–P. The coatings were characterized using scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDX) techniques to analyze surface nature and composition correspondingly. Small amount of incorporated HNTs made Ni–P deposits appreciable enhancement and betterment in corrosion resistance, hardness and friction resistance. This drastic improvement in the properties reflects the effect of addition of HNTs into Ni–P matrix leading to the development of high performance Ni–P–HNT composite coatings.
Keywords: Electroless Ni–P; Halloysite nanotubes; Composite coating; Corrosion; Microhardness; Friction;
Preparation and water-splitting photocatalytic behavior of S-doped WO3 by Wenzhang Li; Jie Li; Xuan Wang; Qiyuan Chen (157-162).
► S-doped WO3 powders were prepared by solid-state annealing method using thiourea as S precursor. ► The absorbance increases with the sulfur concentration of S-doped WO3 samples. ► S-doped WO3 powders were used for photocatalytic water splitting. ► S-doped samples exhibited higher levels of photocatalytic activity under ultraviolet and visible light irradiation.In the present work, sulfur (S)-doped tungsten oxide (WO3) was studied by photoelectrochemical and photocatalytic methods in order to evaluate the photoactivity and the possibility of its application in water splitting. S-doped WO3 powders were prepared by solid-state annealing method using thiourea as S precursor. The crystal structure, composition and morphology of pure and S-doped WO3 were compared using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The influence of doping concentration and annealing temperature on the properties of S-doped WO3 powders and their photocatalytic activities under both ultraviolet (UV) and visible light (VIS) irradiation compared with WO3 were investigated. The results indicate that sulfur can be doped successfully into WO3 and the S-doped WO3 powder annealed at 500 °C exhibited the highest photocatalytic activity under both UV and visible light irradiation. The highest average oxygen evolution rate of S-doped WO3 under UV (99.9 μmol L−1 g−1 h−1) and visible light (76.7 μmol L−1 g−1 h−1) irradiation is 1.25 and 1.57 times the value of that of undoped WO3, respectively.
Keywords: Sulfur-doping; Photocatalysis; Tungsten oxide; Water-splitting;
Na-doped hydroxyapatite coating on carbon/carbon composites: Preparation, in vitro bioactivity and biocompatibility by Hejun Li; Xueni Zhao; Sheng Cao; Kezhi Li; Mengdi Chen; Zhanwei Xu; Jinhua Lu; Leilei Zhang (163-173).
► Na-HA coating with a thickness of 10 ± 2 μm was directly prepared onto C/C using ECD. ► The shear bonding strength of Na-HA coating on C/C is 5.55 ± 0.77 MPa. ► Na-HA coated C/C can rapidly induce bone-like apatite nucleation and growth on its surface in SBF. ► The Na-HA coating was better to improve the biocompatibility of C/C compared with HA coating.Na-doped hydroxyapatite (Na-HA) coating was directly prepared onto carbon/carbon (C/C) composites using electrochemical deposition (ECD) and the mean thickness of the coating is approximately 10 ± 2 μm. The formed Na-HA crystals which are Ca-deficient, are rod-like with a hexagonal cross section. The Na/P molar ratios of the coating formed on C/C substrate is 0.097. During the deposition, the Na-HA crystals grow in both radial and longitudinal directions, and faster along the longitudinal direction. The pattern formation of crystal growth leads to dense coating which would help to increase the bonding strength of the coating. The average shear bonding strength of Na-HA coating on C/C is 5.55 ± 0.77 MPa. The in vitro bioactivity of the Na-HA coated C/C composites were investigated by soaking the samples in a simulated body fluid (SBF) for 14 days. The results indicate that the Na-HA coated C/C composites can rapidly induce bone-like apatite nucleation and growth on its surface in SBF. The in vitro cellular biocompatibility tests reveal that the Na-HA coating was better to improve the in vitro biocompatibility of C/C composites compared with hydroxyapatite (HA) coating. It was suggested that the Na-HA coating might be an effective method to improve the surface bioactivity and biocompatibility of C/C composites.
Keywords: Hydroxyapatite; Coating; Electrochemical deposition; Carbon/carbon composites; Simulated body fluid;
Verification of surface polarity of O-face ZnO(0 0 0 1 ¯ ) by quantitative modeling analysis of Auger electron spectroscopy by C.W. Su; M.S. Huang; T.H. Tsai; S.C. Chang (174-181).
► Quantitative Auger intensity ratios to predict macroscopic surface type to Zn-face or O-face can be obtained using hard sphere model and considering electron mean free paths. ► Calculation of electron signals from 6-layer depth is the best condition in estimating Auger intensity ratios. ► The ratio deviated from the estimation reference after surface treated by annealing or sputtering is classified to Zn-rich or O-rich surface. ► A Zn-rich surface may exist on an O-face surface. ► Surface type of a composite material can be quickly obtained by quantitative analysis of Auger intensity ratio.Is crystalline ZnO(0 0 0 1 ¯ ) O-face surface believed to be enriched by Zn atoms? This study may get the answer. We proposed a simplified model to simulate surface concentration ratio on (0 0 0 1 ¯ )-O or (0 0 0 1)-Zn surface based on the hard-sphere model. The simulation ratio was performed by integrating electron signals from the assumed Auger emission, in which the electron mean free path and relative atomic layer arrangements inside the different polarity ZnO crystal surface were considered as relevant parameters. After counting more than 100 experimental observations of Zn/O ratios, the high frequency peak ratio was found at around 0.428, which was near the value predicted by the proposed model using the IMFP database. The ratio larger than the peak value corresponds to that observed in the annealed samples. A downward trend of the ratio evaluated on the post-sputtering sample indicates the possibility of a Zn-enriched phase appearing on the annealed O-face surface. This phenomenon can further elucidate the O-deficiency debate on most ZnO materials.
Keywords: Structure of clean surfaces; Polarity surfaces; Quantitative spectra analysis; Auger electron spectroscopy;
First-principles study of hydrogen storage on Ti (Sc)-decorated boron-carbon-nitride sheet by Nahong Song; Yusheng Wang; Qiang Sun; Yu Jia (182-186).
► The gravimetric densities of H2 are 7.6 wt% and 7.8 wt%, respectively. ► The average adsorption energy of hydrogen molecule is in the range of 0.4–0.56 eV/H2 (0.13–0.27 eV/H2). ► It can operate under ambient thermodynamic conditions.Ab initio first-principles calculations are carried out to investigate Ti (Sc)-decorated two-dimensional boron-carbon-nitride (BC2N) sheets for their application as hydrogen storage materials. The results show that with four H2 molecules attached to per metal atom the Ti (Sc)-decorated BC2N can store up to 7.6 wt% (7.8 wt%) of hydrogen in molecular form. The Kubas interaction and the polarization mechanism lead to the adsorption energy within the range of 0.4–0.56 eV/H2 (0.13–0.27 eV/H2), which is suitable for ambient temperature hydrogen storage.
Keywords: Hydrogen storage; Adsorption energy; Nanostructure;
Research of the surface properties of the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene modified with radio-frequency magnetron sputtering for medical application by S.I. Tverdokhlebov; E.N. Bolbasov; E.V. Shesterikov; A.I. Malchikhina; V.A. Novikov; Y.G. Anissimov (187-194).
► A method for surface modification of the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene using radio-frequency magnetron sputtering of hydroxyapatite target is proposed. ► It is demonstrated that the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene surface becomes hydrophilic as the result of the modification. ► It is shown, using atomic force microscopy that the surface potential biases into positive value field and the surface roughness parameters increase as the result of the modification. ► In vitro testing has not found bio-toxicity of investigated surfacesThe properties of thin calcium-phosphate coatings formed by radio-frequency magnetron sputtering of a solid target made from hydroxyapatite on the surface of the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene (VDF–TeFE) were investigated. Atomic force microscopy energy dispersive analysis and optical goniometry showed that deposited calcium-phosphate coatings change significantly the morphological, electrical, chemical, and contact properties of the surface of the initial polymeric substrates. These modified surfaces widen the scope of medical application of the thermoplastic copolymer.
Keywords: Magnetron sputtering; Copolymer of vinilidene fluoride and tetrafluoroethylene; Thin calcium-phosphate coatings, Wettability; Surface roughness; Surface potential;
Antibody immobilization on a nanoporous aluminum surface for immunosensor development by Changhoon Chai; Jooyoung Lee; Jiyong Park; Paul Takhistov (195-201).
► A method of antibody immobilization on nanoporous aluminum surface was established. ► The concentration of APTES and silanization time affected antibody immobilization. ► The optimum concentration of APTES and silanization time were obtained. ► Immunosensor prepared with the method responded functionally to its target antigen.A method of antibody (Ab) immobilization on a nanoporous aluminum surface for an electrochemical immunosensor is presented. To achieve good attachment and stability of Ab on an aluminum surface, aluminum was silanized with 3-aminopropyltryethoxysilane (APTES), and then covalently cross-linked to self-assembled layers (SALs) of APTES. Both the APTES concentration and the silanization time affected the formation of APTES-SALs as Ab immobilization. The formation of APTES-SALs was confirmed using the water contact angle on the APTES-SALs surface. The reactivity of APTES-SALs with Ab was investigated by measuring the fluorescence intensity of fluorescein isothiocyanate-labeled Ab-immobilized on the aluminum surface. Silanization of aluminum in 2% APTES for 4 h resulted in higher water contact angles and greater amounts of immobilized Ab than other APTES concentrations or silanization times. More Ab was immobilized on the nanoporous surface than on a planar aluminum surface. Electrochemical immunosensors developed on the nanoporous aluminum via the Ab immobilization method established in this study responded functionally to the antigen concentration in the diagnostic solution.
Keywords: Immunosensor; Antibody immobilization; Electrochemical impedance spectroscopy; Nanoporous structure; Aluminum anodization; Silanization; 3-Aminopropyltryethoxysilane (APTES);
Substrate effects on formation and hydrogenation of Mg–Ni films by Martynas Lelis; Darius Milcius; Dag Noréus (202-209).
► We investigate hydrogenation property dependence on film–substrate interface. ► Mg–Ni film were co-sputtered on Si and expanded PTFE substrates. ► Two different plasma modes were used to modify surface of Si and expanded PTFE. ► Significant influence of interface changes to hydrogenation properties was measured.Usually metallic films for metal hydrides research applications are deposited on hard and flat substrates such as silicon, magnesium oxide, fused silica or quartz glass. With the film thickness increases all films during hydrogenation deals with typical problems such as film brittleness and cracking. In this paper we demonstrate that metal Mg–Ni films for hydrogen storage can be successfully deposited on to the flexible low surface energy expanded PTFE substrates. The received results for soft substrates (expanded PTFE) are compared to films being deposited on crystalline silicon substrate with and without plasma pretreatment. It is observed that different interface zone between substrate and film has great affect on both film crystallinity and its reaction with hydrogen. It is also demonstrated that modifying surface of the substrate might have affect on film microstructure before and after hydrogenation.
Keywords: Hydrogen energy; Hydrogen storage; Mg2NiH4; Metal hydride; Film; Substrate modification; Plasma;
Tailoring the refractive index of aluminum doped zinc oxide thin films by co-doping with titanium by Tiefeng Wei; Pinjun Lan; Ye Yang; Xianpeng Zhang; Ruiqin Tan; Yong Li; Weijie Song (210-214).
► The Al–Ti co-doped zinc oxide (ATZO) thin films with different Ti doping concentration were deposited on glass substrates by radio frequency magnetron sputtering. ► The refractive index of aluminum doped zinc oxide was modulated through titanium co-doping. ► The refractive index of the thin films (at λ 0 = 550 nm) increased from 1.91 to 2.05 as the TiO2 content increased from 0 wt% to 3 wt%. ► Tailoring the refractive index of aluminum doped zinc oxide thin films was important for applications in designing the integrated optoelectronic devices such as a-Si thin film solar cells.The refractive index of transparent conductive oxides has a direct effect on the transmission of lights into thin film solar cells. Here we report the study of improving the refractive index of aluminum doped zinc oxide through titanium co-doping. The Al–Ti co-doped zinc oxide (ATZO) thin films with different Ti doping concentration were deposited on glass substrates by radio frequency magnetron sputtering with ATZO targets in an argon atmosphere. The structural, optical and electrical properties of the thin films were investigated using X-ray diffraction, ultraviolet–visible-near-infrared spectroscopy and hall measurements, respectively. The results showed that the as-deposited thin films were all textured along c-axis and perpendicular to the surface of substrate. The average transmittance in the visible region were more than 80% for all the ATZO thin films. The minimum resistivity of the obtained ATZO (1 wt% TiO2 doping) thin films were 2.6 × 10−3 Ω cm and 1.4 × 10−3 Ω cm before and after annealing in vacuum, respectively. The refractive index of the thin films (at λ 0 = 550 nm) increased from 1.91 to 2.05 as the TiO2 content increased from 0 wt% to 3 wt%.
Keywords: Al–Ti co-doped ZnO thin films; Refractive index; Resistivity;
The effect of thermal cycling by electron-beam surfacing on structure and wear resistance of deposited M2 steel by S.F. Gnyusov; A.A. Ignatov; V.G. Durakov; S.Yu. Tarasov (215-222).
► Thermocycling by multi-pass electron beam assisted deposition of M2 steel powder. ► Multimodal size distribution of reinforcement carbide particles. ► Thermocycling conditions had great effect on retained austenite and martensite. ► Wear resistance improved due to thermocycling and strain-induced martensite.Structural features of coatings obtained by multiple-pass electron beam cladding of M2 steel powder on steel substrates have been investigated. It is established that a multi-modal size distribution (d 1 = 3.8 μm, d 2 = 0.65 μm, d 3 < 0.25 μm) of reinforcement particles was generated in the carbide subsystem of the clad layer. The volume content of secondary carbides M6C and residual austenite of matrix can be changed in the wide range depending on the thermal cycling induced by incident electron beam. The higher is the content of the retained austenite in the coating, the higher is the wear resistance of the coating due to γ → α′ transformation in cooling and precipitation of secondary carbides in the matrix grains.
Keywords: Electron-beam cladding; Structural-phase composition; Wear resistance; High speed steel; Thermal cycling;
Effect of preparation conditions on characteristics of hollow TiO2 fibers fabricated by chemical deposition and template method by Lijun Cheng; Yong Kang; Fei Tong (223-229).
► Hollow TiO2 fibers were prepared by chemical homogeneous deposition method, using synthetic fibers as templates. ► The effect of preparation conditions on the average diameter and length of TiO2 fibers were great. ► The length and cross-section of TiO2 fibers can be controlled by the template's length and morphology. ► The wall thickness of fibers can be controlled by preparation conditions.Hollow TiO2 fibers were successfully prepared by chemical homogeneous deposition method, using synthetic fibers as templates. The experimental results indicated that the average diameter and length of TiO2 fibers could be greatly affected by deposition temperature, concentration of TiOSO4, mass ratio of TiOSO4 and synthetic fiber templates, concentration of precipitator, deposition time, etc. Under the optimal preparation conditions, TiO2 fibers with average outer diameter of 10.2 μm and length of 643 μm were obtained, and the average wall thickness was about 3.5 μm. Besides, the TiO2 fibers were also characterized by XRD and XPS.
Keywords: Hollow TiO2 fiber; Chemical precipitation; Template;
Relationship between the catalytic activity of Pt/alumina and the relaxation process of the photoexcited electrons by Junji Ito; Yasunari Hanaki; Qing Shen; Taro Toyoda (230-235).
► We determined the decay time of photoexcited electrons of Pt/Al2O3. ► Faster decay of excited electrons in Pt/Al2O3 leads to its faster oxidation rate. ► Decreasing excited electron lifetime in Pt/Al2O3 may decrease Pt consumption in catalytic convertors.In order to decrease the consumption of precious metals used in the catalytic converters used in automobiles, we studied the relationship between the catalytic activity of Pt/alumina (Pt/Al2O3) and the relaxation process of photoexcited electrons. Firstly, we studied the relationship between the size of the Pt particles in Pt/Al2O3 and catalytic performance. Secondly, the relationship between the size of the Pt particles in Pt/Al2O3 and the decay time of the excited electrons was studied using an improved transient grating (TG) technique. The results showed that faster decay of the excited electrons leads to greater oxidation rates. The decay time obtained with the improved TG technique gives an indication of the time that the exited electrons take to return to the ground state. According to studies utilizing FT-IR, one of the processes necessary for quickly generating CO2 with Pt is that the electron in the Pt―O bond moves to the Pt side and that the Pt+ becomes Pt metal. Thus, the decay time obtained with the improved TG technique corresponds to the process whereby Pt+ returns to Pt metal. Thus, we found that the consumption of precious metals can be reduced by increasing the speed of the decay of the excited electrons.
Keywords: Platinum; Aluminum oxide; Photoexcited electron; Transient grating technique; Carrier dynamics; Electron transfer;
Microwave synthesized nanostructured TiO2-activated carbon composite electrodes for supercapacitor by M. Selvakumar; D. Krishna Bhat (236-241).
► Nanostructure TiO2 has been prepared by a microwave assisted synthesis method. ► Microwave irradiation was varied with time duration on the formation of nanoparticles. ► TiO2-activate carbon show very good specific capacitance for supercapacitor. ► Electrochemical properties were studied on electroanalytical techniques.Electrochemical properties of a supercapacitor based on nanocomposite electrodes of activated carbon with TiO2 nano particles synthesized by a microwave method have been determined. The TiO2/activated carbon nanocomposite electrode with a composition of 1:3 showed a specific capacitance 92 Fg−1. The specific capacitance of the electrode decreased with increase in titanium dioxide content. The p/p symmetrical supercapacitor fabricated with TiO2/activated carbon composite electrodes showed a specific capacitance of 122 Fg−1. The electrochemical behavior of the neat TiO2 nanoparticles has also been studied for comparison purpose. The galvanostatic charge–discharge test of the fabricated supercapacitor showed that the device has good coulombic efficiency and cycle life. The specific capacitance of the supercapacitor was stable up to 5000 cycles at current densities of 2, 4, 6 and 7 mA cm−2.
Keywords: Titanium oxide; Microwave synthesis; Activated carbon; Supercapacitor; Galvanostatic charge–discharge;
Autocatalytic growth of Co on pure Co surfaces using Co2(CO)8 precursor by R. Córdoba; J. Sesé; M.R. Ibarra; J.M. De Teresa (242-246).
► We investigate the autocatalytic growth of Co using Co2(CO)8 precursor. ► On Si wafers and Co grown by FEBID, no role is played by autocatalytic growth. ► On Co films grown by sputtering, Co grows autocatalytically. ► Implications of the results on Co by FEBID are discussed.The autocatalytic growth of Co on different surfaces using the Co2(CO)8 precursor is investigated. It is observed that Co2(CO)8 molecules dissociate spontaneously on pure Co surfaces grown by sputtering, forming a pure Co film. The microstructure of this film consists of Co nanocrystals with size below 100 nm. However, when the same type of experiment is done on a Co surface grown by focused-electron-beam induced deposition there is no autocatalytic growth of Co. On other surfaces such as Si substrates and Al films grown by sputtering, the spontaneous dissociation of the Co2(CO)8 molecules does not occur. The origin and implications of these results are discussed.
Keywords: Co2(CO)8; Autocatalytic growth; Focused-electron-beam induced deposition;
Effects of pretreatment on the surface chemistry and pore size properties of nitrogen functionalized and alkylated granular activated carbon by Jiajun Chen; Yunbo Zhai; Hongmei Chen; Caiting Li; Guangming Zeng; Daoxiong Pang; Pei Lu (247-253).
► The effects of pretreatment on the surface chemistry and pore sizes were studied. ► Treated GAC was nitrogen functionalized and alkylated GAC also called modified GAC. ► HNO3 pretreatment caused a slight decrease in surface area and microporosity. ► The nitrogen percentage of modified GAC which pretreated by H2O2 was 4.07%. ► The pyridine of modified GAC which pretreated by urea-formaldehyde resin was 45.88%.In this paper, granular activated carbon (GAC) from coconut shell was pretreated by HNO3, H2O2 and urea-formaldehyde resin, respectively. Then the obtained materials were functionalized in the same way for nitrogen group, and then alkylated. Effects of pretreatment on the surface chemistry and pore size of modified GACs were studied. Surface area and micropore volume of modified GAC which pretreated by HNO3 were 723.88 m2/g and 0.229 cm3/g, respectively, while virgin GAC were 742.34 m2/g and 0.276 cm3/g. Surface area and micropore volume decrease of the modified GACs which pretreated by the others two methods were more drastically. The types of groups presented were analyzed by electrophoresis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). N―CH3 group and C＝N group were detected on the surfaces of these three kinds of modified GACs. Results of XPS showed that the nitrogen functions of modified GAC which pretreated by H2O2 was 4.07%, it was more than that of the others two pretreatment methods. However, the modified GAC which pretreated by urea-formaldehyde resin was fixed more pyridine structure, which structure percentage was 45.88%, in addition, there were more basic groups or charge on the surface than the others.
Keywords: Granular activated carbon; Pretreatment; Pore structure; Surface chemistry; Functional group;
Synthesis and photocatalytic properties of visible light responsive La/TiO2-graphene composites by N.R. Khalid; E. Ahmed; Zhanglian Hong; M. Ahmad (254-259).
Display Omitted► Synthesis of La/TiO2-graphene composites by two-step hydrothermal method. ► Efficient charge separation due to La doping and graphene incorporation. ► Enhanced photocatalytic activity of composite catalyst for MB degradation under visible-light.La/TiO2-graphene composites used as photocatalyst were prepared by two-step hydrothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The results of optical properties of La/TiO2-graphene composites exhibit extended light absorption in visible-light region and possess better charge separation capability as compared to pure TiO2. The photocatalytic activity measurement demonstrate that La/TiO2-graphene composites exhibited an enhanced photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation compared to pure TiO2, which was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of graphene and the large surface contact between graphene and La/TiO2 nanoparticles.
Keywords: La/TiO2; Graphene; Composites; Visible-light; Photocatalysis;
Photocatalytic property of Fe doped anatase and rutile TiO2 nanocrystal particles prepared by sol–gel technique by S. Wang; J.S. Lian; W.T. Zheng; Q. Jiang (260-265).
► Fe-doped dual-phase TiO2 powders were prepared by sol–gel route. ► The dual-phase TiO2 with 28.76 wt% rutile phase shows better photocatalytic activity. ► Fe doped dual-phase TiO2 exhibits the best photocatalytic activity among the tested TiO2. ► Fe doped dual-phase TiO2 powders show evident red-shift or decrease in band gap. ► A cooperated mechanism was proposed for the improved photocatalytic process.Anatase and rutile TiO2 composite nanopowders with different Fe-doped concentrations were synthesized by sol–gel technique. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to detect the crystalline structure and chemical state of the nanopowders. The photocatalytic activity was estimated by the degradation of 20 mg/L methyl orange under an irradiation of 350–450 nm light source. TiO2 powder with 28.76 wt% rutile showed the highest degradation among the TiO2 composite powders, but the 1.0 at% Fe-doping TiO2 with 20.64 wt% rutile phase exhibited an even higher degradation than that without Fe doping. Doping of Fe in TiO2 composite powder induced an evident increase in absorption peak and a significant red-shift in absorption edge from 420 nm to 460 nm in UV–vis absorption spectrum, and these characteristics are responsible for the improvement of photocatalytic activity.
Keywords: Anatase; Rutile; Fe-doping; Sol–gel; Photocatalysis; Optical spectroscopy;
A stable single-crystal Bi3NbO7 nanoplates superstructure for effective visible-light-driven photocatalytic removal of nitric oxide by Zhihui Ai; Wingkei Ho; Shuncheng Lee (266-272).
► Bi3NbO7 single-crystal nanoplates superstructure (BNS) was prepared via a facile hydrothermal route without adding any surfactants and templates. ► The BNS exhibited high visible-light-driven photocatalytic performances for the removal of gaseous NO. ► The BNS exhibited high stability during multiple runs of photocatalytic removal of NO due to their special superstructures.In this study, bismuth niobate (Bi3NbO7) single-crystal nanoplates superstructure (BNS) was prepared via a facile hydrothermal route without adding any surfactants and templates by using bismuth citric and niobium pentoxide as precursors. The as-prepared products were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectrum (DRS). The characterization results revealed that the BNS nanostructures were self-assembled of single crystalline nanoplates under hydrothermal environment. These BNS exhibited excellent visible-light-driven (λ > 420 nm) photocatalytic performances for the removal of gaseous nitrogen monoxide (NO), the removal of NO reached 42.3% in 40 min at the presence of BNS, which was much higher than those of C-doped TiO2 (25% of NO removal), the InVO4 hollow microspheres (25% of NO removal), as well as the BiOBr nanoplates microspheres (30% of NO removal). Close investigation indicated that plenty of pores existed in the aggregation of BNS superstructures, which could serve as efficient transport paths for NO molecules and harvesting of more light. Moreover, the BNS exhibited high stability during multiple runs of photocatalytic removal of NO due to their special superstructures. The study provides a facile method to synthesize BNS with high efficiency and high stability in the visible-light spectral range.
Keywords: Nanostructures; Semiconductors; Chemical synthesis; Crystal structure;
Carbon doped TiO2 nanowire arrays with improved photoelectrochemical water splitting performance by Chuanwei Cheng; Yan Sun (273-276).
Display Omitted► Carbon doped TiO2 nanowire arrays were fabricated by a combined hydrothermal and subsequent calcination process. ► Carbon doping enhanced the photoelectrochemical water splitting performance. ► The enhanced performances were mainly arise from improved charge transportation and separation.In the present study, we demonstrate a facile route to fabricate vertical-aligned carbon doped TiO2 nanowire arrays on FTO substrate by combining of a simple hydrothermal growth and a subsequent calcination process in air. The photoelectrochemical measurements indicate that the carbon doped TiO2 photoanode yields a ∼70% enhancement in the photocurrent density in comparison to that of the pristine TiO2. Further IPCE, diffuse reflectance spectra and electrochemical impedance characterizations confirm that the photocurrent improvement is mainly in the UV light region, which is arise from the increased charge carrier densities as well as improved charge transfer and separation induced by carbon doping.
Keywords: TiO2; Carbon doping; Nanowires; Semiconductors; Photoelectrochemical water splitting;
One-pot synthesis and electrochemical reactivity of carbon coated LiFePO4 spindles by Juanjuan Yu; Juncheng Hu; Jinlin Li (277-283).
Display Omitted► Carbon coated LiFePO4 spindles have been successfully synthesized via a novel supercritical method. ► The concentrations of lithium have an effect on the morphology of carbon coated LiFePO4. ► Amorphous carbon layer formed on the surface of LiFePO4 by adding glucose. ► The carbon coating is responsible for the enhanced electrochemical performance.Spindle-like carbon coated LiFePO4 (LiFePO4/C) composites have been successfully synthesized via a novel one-pot supercritical methanol method. The products were characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The particle size, morphology and electrochemical reactivity changed with the concentration of lithium and carbon source. A possible morphology evolution process was also proposed. The glucose not only facilitates the formation of single crystalline LiFePO4, but also gives an amorphous carbon layer on the surface LiFePO4 spindles.
Keywords: Spindle; LiFePO4; Supercritical methanol; Carbon;
Effect of the oxygen partial pressure on the toughness of tetragonal zirconia thin films for optical applications by M. Andrieux; P. Ribot; C. Gasquères; B. Servet; G. Garry (284-290).
► Dopant free tetragonal zirconia phase was obtained at 900 °C by MOCVD at various oxygen partial pressures. ► Tetragonal phase is stable during peculiar annealing. ► A high toughness (4 MPa m1/2) could be achieved for this ceramic film. ► ZrO2 film is a good candidate to protect mirror from water erosion. ► ZrO2 minimum reflectance could be obtained depending on experimental conditions.The zirconia thin films (80–120 nm thick) were deposited on (1 0 0) silicon substrate using metal organic chemical vapor deposition. The effect of oxygen partial pressure during the process and post annealing step on the structure, microstructure and mechanical properties were investigated. Under peculiar experimental conditions, nano-crystallized tetragonal thin films were obtained. The film structure was stable when annealed and some of the films exhibited large toughness values, up to 3.9 MPa m1/2. This high toughness value is interesting to use this material as a protect layer for optical applications as this zirconia layer displays a minimum reflectance in the near infrared window. This minimum reflectance could be shifted depending on the thickness of the films.
Keywords: Zirconia thin films; Tetragonal and monoclinic phases; Phase transformation; Oxygen partial pressure; Indentation; Toughness; Optical properties;
Fabrication of protein-resistant blend based on PVDF-HFP and amphiphilic brush copolymer made from PMMA and PEGMA by Kyung-Hee Hwangbo; Yu-Jeong Kim; Kuk Young Cho (291-296).
► The miscibility of PVDF-HFP with amphiphilic brush copolymer poly(MMA-co-PEGMA) were evaluated by DSC. ► The surface hydrophilicity of PVDF-HFP was improved by blending with polymer brush. ► Protein adsorption resistance was enhanced by both of PMMA and PEG of polymer brush.Polymeric blends provide a facile route to obtaining materials with various synergistic properties arising from the individual components. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), a hydrophobic polymer, is finding new applications in polymer electrolytes, membranes, and heat-resistant structural materials owing to its high thermal stability, mechanical strength, and weatherability. In this report, blends of PVDF-HFP and polymer brush were prepared with enhanced water uptake and protein resistance, which are important requirements for membranes used in food and biological applications. Polymer brush is composed of poly(methyl methacrylate) main chains, which are miscible with PVDF-HFP, and hydrophilic poly(ethylene glycol) (PEG) brush chains. Incorporation of PEG chains through the polymer brush structure not only enhanced water uptake and protein adsorption resistance but also produced a well-distributed morphology of the blending components through the matrix as evidenced by observation of the morphology after selective extraction of polymer brush from the matrix.
Keywords: Polymer blends; Membrane; Polymer brush; Miscibility; Protein adsorption resistance;
Preparation of superhydrophobic titanium surfaces via electrochemical etching and fluorosilane modification by Yao Lu; Wenji Xu; Jinlong Song; Xin Liu; Yingjie Xing; Jing Sun (297-301).
► We prepare superhydrophobic titanium surfaces via electrochemical etching and fluorosilane modification that have stability and abrasion resistance. ► Ion activities take place in neutral solution can drive Ti dissolution without affecting the pH. ► Analysis of the electrolyte, reaction process, and products indicates that the electrochemical processing is harmless and environment-friendly.The preparation of superhydrophobic surfaces on hydrophilic metal substrates depends on both surface microstructures and low surface energy modification. In this study, a simple and inexpensive electrochemical method for preparing robust superhydrophobic titanium surfaces is reported. The neutral sodium chloride solution is used as electrolyte. Fluoroalkylsilane (FAS) was used to reduce the surface energy of the electrochemically etched surface. Scanning electron microscopy (SEM) images, energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) spectra, and contact angle measurement are performed to characterize the morphological features, chemical composition, and wettability of the titanium surfaces. Stability and friction tests indicate that the prepared titanium surfaces are robust. The analysis of electrolyte, reaction process, and products demonstrates that the electrochemical processing is very inexpensive and environment-friendly. This method is believed to be easily adaptable for use in large-scale industry productions to promote the application of superhydrophobic titanium surfaces in aviation, aerospace, shipbuilding, and the military industry.
Keywords: Superhydrophobic surfaces; Electrochemical; Microstructure; Robust; Environment-friendly;
Microstructure changes of polyimide/MMT-AlN composite hybrid films under corona aging by M.H. Chen; J.H. Yin; W.B. Bu; X.X. Liu; B. Su; Q.Q. Lei (302-306).
► Polyimide/MMT-AlN films were achieved by in situ polymerization process. ► Microstructure of films was greatly affected by the lamellar and globular structure of particles. ► The PI/MMT-AlN film with dense block layer appeared enhanced electrical properties.A novel method using montmorillonite-AlN (MMT-AlN) composite particles as dopants in polyimide (PI) has been proposed and tested. We choose MMT-AlN as dopants in PI for lamellar structure of MMT and globular structure of AlN and hope such mixed micro- and nano-particles can enhance PI's resistance to corona aging. Our corona aging test result has confirmed our method and a 7% doped PI/MMT-AlN film has corona aging time extended more than 40 times compared with pure PI film. The microstructure changes of PI/MMT-AlN films due to corona aging have been analyzed by multiple surface analysis techniques. The analysis result shows coexistence of mass fractal and surface fractal in the sample films of PI/MMT-AlN. A dense inorganic block layer of MMT-AlN formed on the surface of doped PI films during corona aging is believed to be the mechanism of providing the protection against further corona aging.
Keywords: Polymer; Microstructure; Nanocomposites; Corona aging; Fractal characteristics;
Sputtering characteristics, crystal structures, and transparent conductive properties of TiO x N y films deposited on α-Al2O3(0 0 0 1) and glass substrates by Housei Akazawa (307-313).
► Reactive sputtering of TiO x N y films was achieved under metal-mode conditions. ► Partially substituting O in TiO2 with N formed anatase rather than rutile. ► TiO2−x N x on Al2O3(0 0 0 1) was more transparent and conductive than on glass substrate. ► Nb5+ ions could be doped as donors in TiO2−x N x anatase crystals.Adding N2 gas during reactive sputtering of a Ti target prevented the target surface from being severely poisoned by oxygen atoms and sustained a high deposition rate for titanium oxynitride films under metal-mode-like sputtering conditions. With progress in the degree of oxidization, films deposited onto a glass substrate varied from TiO1−x N x having a face-centered cubic (fcc) structure to TiO2−x N x having an anatase structure. Titanium oxynitride films deposited on an Al2O3(0 0 0 1) substrate were epitaxial with major orientations toward the (1 1 1) and (2 0 0) directions for fcc-TiO1−x N x and (1 1 2) for anatase-TiO2−x N x . Intermediately oxidized films between TiO1−x N x and TiO2−x N x were amorphous on the glass substrate but crystallized into a Magneli phase, Ti n O(N)2n−1, on the Al2O3(0 0 0 1) substrate. Partially substituting oxygen in TiO2 with nitrogen as well as continuously irradiating the growing film surface with a Xe plasma stream preferentially formed anatase rather than rutile. However, the occupation of anion sites with enough oxygen rather than nitrogen was the required condition for anatase crystals to form. The transparent conductive properties of epitaxial TiO2−x N x films on Al2O3(0 0 0 1) were superior to those of microcrystalline films on the glass substrate. Since resistivity and optical transmittance of TiO x N y films vary continuously with changing N2 flow rate, their transparent conductive properties can be controlled more easily than TiO x . Nb5+ ions could be doped as donors in TiO2−x N x anatase crystals.
Keywords: Anatase; TiO x N y ; Sputtering; Transparent conductive film; Nb doping;
Synthesis and tribological behaviour of electroless Ni–P-WS2 composite coatings by I. Sivandipoor; F. Ashrafizadeh (314-319).
► Incorporation of WS2 solid lubricant particles in Ni–P coating reduced the hardness. ► Use of WS2 particles in the coating modified the wear behaviour of Ni–P coating. ► WS2 particles as solid lubricant reduced the friction coefficient significantly. ► The dominant wear mechanisms for the coatings are adhesive and abrasive.WS2 particles, as solid lubricant, were incorporated in electroless nickel–phosphorous to produce a new composite coating with enhanced tribological properties. Coating deposition was carried out in a laboratory electroless bath followed by heat treatment at 400 °C. The process included pretreatment of steel substrate by grinding and polishing to reach an appropriate roughness, surface activation by degreasing and acid cleaning and preparation of WS2 powder before addition to the electroless bath. Evaluation of friction coefficient and wear resistance was performed by a pin-on-disc tribotester at room temperature. Characterization of the surface and interface was achieved by scanning electron microscopy, microhardness measurements, X-ray diffraction and energy dispersive microanalysis to identify the chemical composition and phases in the composite coatings. Experimental results indicated that use of WS2 particles in the coating decreased the hardness and modified the wear behaviour of conventional Ni–P coating; the coefficient of friction was reduced from above 0.6 to about 0.1. The percentage of solid lubricant particles added and their distribution in the coating structure were found to be the key factors in improving the frictional behaviour of this composite coating.
Keywords: Composite coating; Tribology; Electroless nickel; WS2 solid lubricant; Friction;
Magnetic and microwave absorption properties of electrospun Co0.5Ni0.5Fe2O4 nanofibers by Jun Xiang; Yanqiu Chu; Xionghui Zhang; Xiangqian Shen (320-325).
► Co0.5Ni0.5Fe2O4 nanofibers with diameters of 70–100 nm were prepared via an electrospinning technique. ► The microwave absorption performance of Co–Ni ferrite nanofibers was reported for the first time. ► The calcination temperature has significant effects on the surface morphology and magnetic properties of the nanofibers. ► Co0.5Ni0.5Fe2O4 nanofibers have a good microwave absorbing performance in the Ku-band.Co0.5Ni0.5Fe2O4 nanofibers with 70–100 nm in diameter were fabricated by the electrospinning and calcination process. Their saturation magnetization gradually enhances from 37.5 to 66.2 emu/g with increasing calcination temperature from 450 to 800 °C, while the corresponding coercivity increases initially, achieving a maximum value of 78.3 kA/m at 600 °C and then decreases with further increase in calcination temperature due to the transformation of magnetic structure from single-domain to multi-domain. By dispersing the nanofibers into a silicon rubber matrix homogeneously, the electromagnetic parameters of them were measured in the frequency range of 2–18 GHz and the microwave reflection loss was calculated according to the transmission line theory. The reflection loss exceeding −5 dB is obtained between 11 and 18 GHz for the silicon rubber composites containing 15 vol% Co0.5Ni0.5Fe2O4 nanofibers with coating thicknesses of 2.5–3.2 mm. These Co0.5Ni0.5Fe2O4 nanofibers possess a good microwave absorption performance in the Ku band and have a great potential as microwave absorber for practical applications.
Keywords: Co–Ni ferrite; Nanofiber; Electrospinning; Magnetic property; Microwave absorbing performance;
Comparison of sizing effect of T700 grade carbon fiber on interfacial properties of fiber/BMI and fiber/epoxy by Lirui Yao; Min Li; Qing Wu; Zhishuang Dai; Yizhuo Gu; Yanxia Li; Zuoguang Zhang (326-333).
► Carbon fiber sizings can react itself and with resin at high temperature. ► Sizings improve IFSS of carbon fiber/epoxy, but reduce that of BMI matrix. ► IFSS of carbon fiber/epoxy is larger than corresponding carbon fiber/BMI. ► Partially desized carbon fiber shows the effect of polymeric sizing component. ► The results are helpful for optimizing sizing agent of carbon fiber composites.This paper aims to study impact of sizing agents on interfacial properties of two T700 grade high strength carbon fibers with bismaleimide (BMI) and epoxy (EP) resin matrix. The fiber surface roughness and chemical properties are analyzed for sized, desized, and partially desized carbon fibers, using atom force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. FTIR analysis indicates that the sizing agents are chemically reactive, and they can react with BMI and EP at high temperatures. The micro-droplet tests exhibit that the desized carbon fibers have lower interfacial strengths with EP than the sized fibers, however, for BMI matrix, opposite trend is revealed. This is consistent with the chemical reactions of the sizing agents with the EP and BMI resins, in which sufficient reactions are observed for the sizing/EP mixture, while only partial reactions are probed for the sizing/BMI mixture. Interestingly, un-extracted epoxy type sizing particles are observed on partially desized carbon fiber surface, which significantly improves the interfacial adhesion with EP matrix.
Keywords: Carbon fiber; Bismaleimide; Epoxy; Sizing agent; Interfacial adhesion;
Optical characterization of poly(methyl methacrylate) implanted with low energy ions by Renu Gupta; Vijay Kumar; Parveen Kumar Goyal; Shyam Kumar (334-338).
► The study provides the optical behavior of ion-implanted poly(methyl methacrylate). ► Optical energy gap reduces from 3.13 to 0.8 and 2.8 eV for N and Ar implanted PMMA. ► Refractive index increases from 1.54 to 2.71 and 2.02 for N and Ar implanted PMMA. ► The changes after N and Ar implantation are justified by Raman spectroscopy. ► The implanted PMMA may find extensive applications in opto-electronic devices.The samples of poly(methyl methacrylate) (PMMA) were subjected to 100 keV N+ and Ar+ ion implantation up to a maximum fluence of 2 × 1016 ions/cm2. The effect of ion implantation on the optical energy gap and the refractive index has been studied through UV–visible spectroscopy. The results clearly indicate a decrease in the values of optical energy gap and an increase in the values of refractive index as an effect of ion implantation corresponding to both of the ions. It has also been observed that the changes induced by the implanted ions are more pronounced for N+ ions in comparison to Ar+ ions. This variation has been correlated with the calculated ranges of these ions in PMMA polymer using Stopping and Range of Ions in Matter (SRIM) code. Finally, an attempt has been made to correlate all the observed changes with the induced structural changes as revealed through Raman spectroscopy.
Keywords: PMMA; Ion implantation; Optical energy gap; Refractive index;
Molecular dynamics simulation of hydrogenated carbon film growth from CH radicals by W.L. Quan; X.W. Sun; Q. Song; Z.J. Fu; P. Guo; J.H. Tian; J.M. Chen (339-344).
► We simulated the hydrogenated carbon film growth from CH radicals using classical molecular dynamics method. ► Effects of incident energy on the film structure were investigated. ► The contribution of adsorption, reactions, implantation and sputtering to film growth were analyzed. ► The optimized incident energy of CH is suggested in the range from 10 to 70 eV for gaining smooth film.The growth of hydrogenated carbon film from CH radicals is studied by classical molecular dynamics simulation for various incident energies (3.25–130 eV). The impingement of CH radical and its effect on the microstructure of formed film are carefully analyzed. It is found that the sp3-C fraction is almost identical to the H concentration for all films; both of them decrease with increasing incident energy. To deposit hydrogenated carbon film with fine smoothness, the energy of incident CH should be 10–70 eV. At other energies (either lower or higher), deposited films are of roughness and with some chain-like structures at surface. Different growth mechanisms behind these observations are discussed.
Keywords: Hydrogenated carbon film; CH radical; Molecular dynamics simulation; Growth mechanism;
Enhanced photocatalytic decomposition of methylene blue by the heterostructure of PdO nanoflakes and TiO2 nanoparticles by Chien-Jung Huang; Fu-Ming Pan; I-Chun Chang (345-351).
► PdO/TiO2 heterostructure was prepared to study photodegradation of methylene blue. ► The heterostructure enhances methylene blue decomposition under UV illumination. ► The enhancement is due to fast e–h pair separation at the PdO/TiO2 heterojunction.We prepared PdO nanoflakes by reactive sputter deposition to form a heterostructure with TiO2 nanoparticles on the SiO2 substrate for the study of photocatalytic decomposition of methylene blue (MB) molecules. Although the PdO nanoflake has little photocatalytic activity toward MB decomposition, the PdO/TiO2 heterostructure has a photocatalytic activity toward MB decomposition under UV light illumination as large as twice that of bare TiO2 nanoparticles. The enhancement in the photocatalytic activity is ascribed to the fast photogenerated carrier separation resulting from the potential barrier formed at the heterojunction between the two oxide semiconductors. Although PdO nanoflakes can be photoexcited under visible light illumination, the PdO/TiO2 heterostructure exhibits little photocatalytic activity toward the MB decomposition.
Keywords: PdO; TiO2; Heterostructure; Methylene blue; Photocatalysis;
Platinum nanocluster growth on vertically aligned carbon nanofiber arrays: Sputtering experiments and molecular dynamics simulations by Pascal Brault; Amaël Caillard; Christine Charles; Rod W. Boswell; David B. Graves (352-356).
► Molecular dynamics simulation of platinum cluster growth on model carbon nanofibers. ► We compare modeled and experimental cluster growth. ► We determine sticking coefficient evolution among deposition time and type of nanofibers. ► We determine cluster size distribution on various model nanofibers.Sputtered platinum nanocluster growth on previously plasma enhanced chemical vapor deposition – PECVD – grown vertically aligned carbon nanofiber arrays is presented. Experimental cluster size distribution is shown to decrease from the CNF top to bottom, as observed by transmission electron microscopy. Molecular dynamics simulations are carried out for understanding early stages of Pt growth on model CNF arrays. Especially, sticking coefficients, concentration profiles along CNF wall, cluster size distributions are calculated. Simulated cluster size distribution are consistent with experimental finding. Sticking coefficient decreases against deposition time. The shape of the sticking curve reflects the nanocluster growth process.
Keywords: Nanocluster growth; Carbon nanofibers; Sputtering deposition; PECVD; Molecular dynamics simulation; Sticking coefficient;
SEM/EDX and XPS studies of niobium after electropolishing by T. Hryniewicz; K. Rokosz; H.R. Zschommler Sandim (357-361).
► New electrolyte proposed for niobium electropolishing. ► SEM/EDX present general composition of Nb surface after EP. ► Main Nb surface stoichiometries revealed by XPS.The studies of niobium after electrochemical polishing EP in sulfuric–methanesulfonic acid mixture were performed. The NbOx/Nb surface was studied by SEM/EDX and XPS methods to find out the chemical composition of the oxygen-induced structures. Specifically the XPS results obtained after EP treatment indicate prevailing part of oxygen with niobium oxides on the sample surface. In order to correctly interpret these structures the photoelectron spectra of main niobium oxides were analyzed, and the spectra of internal Nb 3d and O 1s electronic states and valence band spectra were measured for them.
Keywords: Electropolishing (EP); Nb surface; SEM/EDX results; XPS results;
Effects of substrate material on carbon films grown by laser molecular beam epitaxy by M. Liu; X.Y. Xu; B.Y. Man; D.M. Kong; S.C. Xu (362-366).
► We prepared tri-layers by laser molecular beam epitaxy (LMBE) on sapphire substrate. ► We found that the formation of the graphene film has a strong relation to the structure and properties of the substrate. ► The different carbon film formation mechanism of the buffer layers can affect the morphology of the film.The carbon thin films were grown on different substrates with different buffer layers by laser molecular beam epitaxy (LMBE) with a high purity graphite carbon target. A UV pulsed KrF excimer laser with a wavelength of 248 nm was used as laser source. The structure, surface morphology and other properties of the carbon thin films were characterized by Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and atomic force microscopy (AFM). The results show that the properties of the carbon thin films and the formation of the graphene film have a strong relation to the structure and properties of the substrate. The substrate with a hexagonal wurtzite structure which is similar to the hexagonal honeycomb structure of the carbon atoms arranged in the graphene is more beneficial for the formation of the graphene thin film. In our experiment conditions, the carbon films grown on sapphire substrates with different buffer layers have an ordered structure and a smooth surface, and form high quality tri-layer graphene films.
Keywords: Carbon thin film; Laser molecular beam epitaxy; Substrate and buffer effects;
Growth of amorphous SiC film on Si by means of ion beam induced mixing by Árpád Barna; Sandor Gurban; László Kotis; János Lábár; Attila Sulyok; Attila L. Tóth; Miklós Menyhárd; Janez Kovac; Peter Panjan (367-372).
► SiC rich layer has been produced by irradiating the C/Si interface by Ga+ ions. ► The amount of SiC produced depends on the square root of fluence of the projectile. ► TRIDYN code can describe the ion mixing process. ► The formation of SiC is explained by defect-mediated reaction.Focused ion beam (FIB)-induced ion mixing was studied in a C/Si/C/Si/C/Si substrate multilayer structure sample by means of Auger electron spectroscopy (AES) depth profiling, and transmission electron microscopy (TEM). The multilayer sample was irradiated with Ga+ ions using focused ion beam (FIB) at room temperature. The ion energy and fluence of the ion irradiation varied in the range of 10–30 keV and 10–120 × 1015 ions/cm2, respectively. The ion irradiation induced a slightly asymmetric intermixing of the top C and Si layers, which could be modeled by the TRIDYN code. During ion mixing, part of the intermixed C and Si atoms reacted, forming amorphous SiC. The amount of SiC depends on the square root of the Ga+ fluence. Thus, amorphous SiC thin film (with Ga contamination) with thickness in the nanometer range can be produced by means of FIB.
Keywords: Amorphous SiC; SiC coating; Ion mixing; Defect mediated compound formation; Ion damage; Compound formation by FIB;
Effect of pyridine on the electrocrystallization and corrosion behavior of Ni–W alloy coated from citrate–ammonia media by W. Sassi; L. Dhouibi; P. Berçot; M. Rezrazi; E. Triki (373-381).
► Ni–W–Pyr coatings were homogeneous with finer grain size with dendrites. ► Ni–W–Pyr contains about 11% of W when it is only 0.1% for Ni–W coatings. ► Ni–W–Pyr deposits improve electrical, mechanical and electrochemical properties of Cu. ► Ni–W films obtained from pyridine bath improved better stability into 3% NaCl. ► Pyridine has been not only adsorbate onto the Ni–W layer but also through it.The effect of pyridine on coatings morphology, composition and crystallographic orientation during electrodeposition of Ni–W layers from citrate–ammonia media onto copper substrate was investigated using SEM/EDS and XRD. The obtained Ni–W–Pyr layers were smoother, more compact and with finer grain size. Furthermore, deposited film gives good crystalline structure with (2 0 0), (1 1 1) and (3 1 1) preferred orientations. Corrosion mechanisms and stability in 5 h of immersion into 3% NaCl of various coatings were discussed in the consideration of electrical conductivity, microhardness, porosity, and inhibition efficiency.
Keywords: Ni–W alloy; Copper; Pyridine; Electrodeposition; Corrosion;
Preparation, characterization and visible-light-driven photocatalytic activity of Fe-incorporated TiO2 microspheres photocatalysts by Jun-Qi Li; De-Fang Wang; Zhan-Yun Guo; Zhen-Feng Zhu (382-388).
► Fe incorporated TiO2 microspheres were prepared by impregnating–calcination method. ► The samples exhibit high photocatalytic activity under visible light irradiation. ► The enhanced photocatalytic properties are attributed to the structure-dependent advantage.Fe incorporated TiO2 microspheres (Fe-TiO2) were prepared by integrating the sol–gel method and impregnating–calcination method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV–vis diffuse reflectance spectroscopy indicated that α-Fe2O3 nanoparticles were deposited onto the TiO2 microspheres, and in the mean time, some Fe3+ ions were doped into TiO2 lattice. The absorption of Fe-TiO2 microspheres in the visible light region increased with the increasing of Fe content. Photoluminescence (PL) analyses further confirmed that Fe-incorporation effectively promoted the separation and transfer of photogenerated charge carriers, which can improve the photocatalytic activity of the samples. The photocatalytic activity of Fe-TiO2 microspheres was evaluated by the degradation of methylene blue aqueous solution under visible light irradiation. The results demonstrated that the Fe-TiO2 microspheres exhibited significantly enhanced photocatalytic activity compared with pure TiO2 microspheres. What is more, the charge-transfer processes in Fe-TiO2 were also discussed.
Keywords: TiO2 microspheres; Fe-incorporation; Impregnating–calcination method; Photocatalytic activity; Visible-light;
Hydrogen peroxide generation and photocatalytic degradation of estrone by microstructural controlled ZnO nanorod arrays by Yangsi Liu; Jie Han; Wei Qiu; Wei Gao (389-396).
Display Omitted► H2O2 generated by ZnO nanorod arrays during UV irradiation was detected. ► ZnO nanorod arrays were synthesized via a facile hydrothermal technique. ► The microstructure can be controlled by varying reactants’ concentration. ► Photocatalytic degradation of estrone by ZnO nanorod arrays was studied. ► Microstructures’ effect on photocatalysis and H2O2 generation was discussed.The strong oxidant, hydrogen peroxide (H2O2), generated by ZnO nanorod arrays under UV light irradiation was monitored by fluorescence analysis. The ZnO nanorod arrays were synthesized via a low temperature hydrothermal method and their dimensions, i.e., diameter and height, can be controlled by adjusting the concentration of zinc nitrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT). The morphology, nanostructure, surface roughness and optical property were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmittance spectra, respectively. The ZnO nanorod arrays were applied in the degradation of estrone, which is an emerging steroid estrogen contaminant. The results revealed that the ZnO nanorod array produced from 25 mM Zn2+ and HMT had the highest aspect ratio, the largest surface roughness and the lowest band gap energy, which was beneficial to the efficiency of UV light utilization, photocatalytic degradation of estrone and H2O2 generation.
Keywords: ZnO nanorod array; Microstructure; H2O2; Fluorescence; Estrone; Photocatalysis;
Self-assembled manganese oxide structures through direct oxidation by Chao Zhao; Qingxiao Wang; Yang Yang; Bei Zhang; X.X. Zhang (397-404).
Display Omitted► We studied the morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation. ► At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. ► As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. ► We gave a clear picture of the evolution of the structures. ► We examined the properties of the structures.The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures.
Keywords: Oxide surfaces; Nucleation and growth; Models of film growth; Micro-oxidation;
Laser-induced hydrophobicity on single crystal zinc oxide surface by Sijing Xie; Yan Zhao; Yijian Jiang (405-409).
► We can change the wettability through KrF excimer laser irradiation and post annealing treatment. ► Highly hydrophobic surface of ZnO crystal substrate is prepared easily and rapidly by KrF excimer laser irradiation. ► After annealing at O2, the surface changed to hydrophilic state because of the adsorption of abundant oxygen atoms.Highly hydrophobic surface of ZnO crystal substrate is prepared easily and rapidly by KrF excimer laser irradiation. The water contact angle is increased from 70° to approximately 120°. Through the XRD, AFM, XPS measurements and the Cassie–Baxter model analysis, it is indicated that the unique micro-nano fluctuant surface structure induced by laser irradiation is the prominent factor to the great increase of the water CA. The annealing treatments for the irradiated sample are carried out both in oxygen and vacuum atmosphere. It is found that the adsorption of oxygen atoms on the roughened surface could make the CA decrease abruptly at the first beginning, and after being stored at ambient atmosphere, the CA would reconvert to the value of the freshly irradiated sample gradually. It probably provides a convenient method for rapid conversion of the wettability through excimer laser irradiation and post annealing treatment.
Keywords: Hydrophobility; Laser irradiation; ZnO single crystal;
Site-controlled synthesis and mechanism of three-dimensional Mo2S3 flowers by Yu Zhong; Yong Zhang; Gaixia Zhang; Ruying Li; Xueliang Sun (410-415).
Display Omitted► Three-dimensional Mo2S3 flowers with steady morphology were synthesized by CVD method. ► Without Au particles, only high S concentration led to dense nanopetals. ► With Au particles, dense nanostructures were obtained at various S concentration. ► Three-dimensional Mo2S3 flowers grew at optimal S concentration with Au particles.High-density three-dimensional Mo2S3 flowers have been facilely synthesized with controlled sites by introducing gold particles as the nucleation sites in a chemical vapor deposition process. The whole size of each flower is in micro scale while individual petal has extremely small thickness of around 10 nm. The role of gold particles and precursor concentration in the growth has been carefully investigated. Without gold particles, dense nanopetals were not able to be obtained unless in a highly concentrated sulfur atmosphere. With Au particles, dense products were steadily achieved in a wide precursor concentration range with S:MoO3 molar ratio from 1:5 to 5:1. The morphology and structure of the as-synthesized nanostructures were characterized using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The growth mechanism was proposed in which gold particles acted as the initial nucleation sites fixing the nucleation position of the flowers following vapor–solid growth mechanism.
Keywords: Mo2S3 flowers; Three-dimensional; CVD; Au particles;
Anisotropic wetting of copper alloys induced by one-step laser micro-patterning by M. Hans; F. Müller; S. Grandthyll; S. Hüfner; F. Mücklich (416-422).
Display Omitted► One-step, contactless micro-patterning of copper alloys has been achieved. ► Anisotropic wetting properties are tailored by line-like structures. ► Both topographical and chemical patterns contribute to the phenomenon. ► The topographic shape and homogeneity are found to be governing factors.Copper alloys (CuSn8, CuZn23Al3Co) have been micro-patterned with line-like geometries by Laser Interference Surface Structuring (LISS). In the presented study two high power pulsed laser beams are recombined to create unique, line-like intensity distributions with a chosen, constant periodicity of 10 μm at varying laser fluencies. Anisotropic wetting properties on these surfaces have been confirmed by drop shape analysis and static contact angle measurements, which were conducted parallel and perpendicular to the structures revealing up to 25% difference in contact angle. The topography and chemistry of the tailored line structures have been characterized and analyzed by white light interferometry, spatial frequency distribution, AFM and X-ray photoelectron spectroscopy. The topographic shape and homogeneity are considered as key parameters for anisotropic wetting design, although it is concluded that both, the geometry as well as the locally varying chemical composition of the surface structures contribute to the phenomenon. Parallel capillarity effects and perpendicular contact line pinning are found to be the governing mechanisms.
Keywords: Laser Interference Metallurgy; Surface functionalization; Copper; Wetting; Contact angle;
Two-wavelength Raman study of poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation by M. Veres; A. Tóth; M. Mohai; I. Bertóti; J. Szépvölgyi; S. Tóth; L. Himics; M. Koós (423-429).
► He plasma-based ion implanted PET was studied by Raman using 488 and 785 nm excitations. ► Downshift occurred for C＝C peak at both wavelengths and for C＝O peak at 488 nm. ► Upshift and broadening occurred for C＝O peak at 785 nm excitation. ► New peak appeared at 785 nm excitation, assignable to C＝O on distorted polymer chain. ► C＝C and C＝O peak intensities and C＝O peak width depended on ion acceleration voltage.The surface of poly(ethylene terephthalate) (PET) was modified by helium plasma-based ion implantation (He PBII). The untreated and surface modified samples were characterised with optical absorption spectroscopy and two-wavelength micro-Raman spectroscopy excited with 488 nm and 785 nm light sources, allowing to examine the chemical bonding configuration of the surface layers on different depths and by selective enhancement of vibrations of different structural units. Upon treatment, simultaneously with the development of the broad D and G bands, a gradual decrease of the peaks corresponding to the C＝C stretching and C＝O stretching modes were observed with both excitations. Downshifting and broadening were detected for the C＝C peak with both excitations and also for the C＝O peak with the 488 nm excitation due to formation of condensed aromatic rings. Oppositely, upshifting was found with 785 nm excitation for the C＝O peak and especially for its broad shoulder newly developed at the high wavenumber side. The latter feature was assigned to C＝O groups attached to polymer chains without conjugation and the bands behaviour was interpreted by breaking of the C＝C bonds of the polymer, leading to the formation of a crosslinked, disordered and stressed structure with still intact C＝O groups, due to the increased nuclear damage at the end of the ion track.
Keywords: Poly(ethylene terephthalate); Plasma-based ion implantation; Two-wavelength micro-Raman spectroscopy;
Fabrication of size-tunable, periodic Si nanohole arrays by plasma modified nanosphere lithography and anisotropic wet etching by S.L. Cheng; Y.H. Lin; S.W. Lee; T. Lee; H. Chen; J.C. Hu; L.T. Chen (430-435).
► We propose a new technique to fabricate periodic Si nanohole arrays on (0 0 1)Si. ► The sizes of Si nanoholes could be tuned by adjusting the KOH etching time. ► The nanohole-structured (0 0 1)Si surfaces exhibit strong antireflection properties. ► The combined approach can be extended to the selective-area fabrication of nanohole arrays.In this study, we propose a new, facile and efficient method to define the desired patterns on Si surfaces and to fabricate periodic arrays of size- and position-controllable Si nanoholes on blank- and pre-patterned (0 0 1)Si substrates, which is based on the O2 plasma modified nanosphere lithography with an anisotropic wet etching technique. In contrast to earlier approaches, no additional thin-film deposition equipments and metal film hard masks are needed for this method. The Si nanohole arrays exhibit the same hexagonal arrangement as the initial colloidal nanospheres template. The sizes of the Si nanoholes can be tuned from 150 nm to 480 nm by varying the etching time. The Si substrates with nanohole-textured surfaces exhibit strong antireflection properties. UV–Vis spectroscopic measurements revealed that by increasing the nanohole size, the optical reflectance of the nanohole-structured (0 0 1)Si surfaces was gradually decreased down to less than 8 %. Since the nanohole sizes, shapes and spacings can be readily controlled by adjusting the diameters of the colloidal nanospheres and anisotropic wet etching conditions, the combined approach presented here provides the capability to fabricate a variety of nanohole array structures on various Si-based substrates without complex lithography.
Keywords: Plasma; Nanosphere lithography; Wet etching; Nanohole; Antireflection;
Unclassical ripple patterns in single-crystal silicon produced by femtosecond laser irradiation by Wei Zhang; Guanghua Cheng; Qiang Feng (436-439).
► Transition from classical ripples to unclassical ripples. ► Laser fluence has a significant effect on the unclassical ripple period. ► Relationship between structures and their parametric dependence is established. ► Capillary wave is responsible for the formation of unclassical ripples.Laser-induced periodic surface structures (LIPSS) in single-crystal silicon upon irradiation with multiple linearly polarized femtosecond (fs) laser pulses (120 fs, 800 nm, 1 kHz) were investigated under different laser fluence and pulse number. Unclassical ripples (U-ripples), which were nearly parallel to the polarization of the laser beam, were observed to form gradually on the top of classical ripples with the effective pulse number. Their periods were significantly longer than the laser wavelength, and increased with increasing both the laser fluence and pulse number in the current study. The relationship between the types of ripple patterns and their parametric dependence was established. The mechanism of U-ripple formation was attributed to the capillary wave, arising from the inhomogeneous temperature gradient combined with the electric field of the pulses in the molten surface layer.
Keywords: Femtosecond laser; LIPSS; Unclassical ripples; Capillary wave;
Chemically deposited In2S3–Ag2S layers to obtain AgInS2 thin films by thermal annealing by S. Lugo; Y. Peña; M. Calixto-Rodriguez; C. López-Mata; M.L. Ramón; I. Gómez; A. Acosta (440-444).
► We obtained polycrystalline silver indium sulfide thin films through the annealing of chemically deposited In2S3–Ag2S films. ► According to XRD chalcopyrite structure of AgInS2 was obtained. ► AgInS2 thin film has a band gap of 1.86 eV and a conductivity value of 1.2 × 10−3 (Ω cm)−1.AgInS2 thin films were obtained by the annealing of chemical bath deposited In2S3–Ag2S layers at 400 °C in N2 for 1 h. According to the XRD and EDX results the chalcopyrite structure of AgInS2 has been obtained. These films have an optical band gap, E g, of 1.86 eV and an electrical conductivity value of 1.2 × 10−3 (Ω cm)−1.
Keywords: Silver indium sulfide; Thin films; Chemical bath deposition;
Effect of treatment duration on surface nanocrystallization induced by fast multiple rotation rolling and its thermal stability by Pengfei Chui; Yi Liu; Yanjie Liang; Yang Li; Suhua Fan; Kangning Sun (445-448).
► Effect of treatment time on surface nanocrystallization of a low carbon steel. ► The grain size decreases gradually with the increase of treatment duration. ► The microhardness of FMRR treated sample reaches 284 HV. ► The nanocrystalline layer is stable during annealing treatment up to 400 °C.A nanocrystalline surface layer of low carbon steel induced by fast multiple rotation rolling (FMRR) was determined by optical microscopy and transmission electron microscopy. The results show that the grain size decreases gradually with the increase of treatment duration. Equiaxed nanocrystalline with the average grain size about 20 nm is obtained in the top surface layer after FMRR treatment for 30 min. With the increase of treatment duration (60 min), the average grain size further reduces to about 9 nm. At the same time, the microhardness of surface layer for treated sample is improved correspondingly owing to grain refinement and work-hardening. Compared with original sample, the microhardness of FMRR treated sample is increased by more than 200%. After annealing treatment, the investigation of thermal stability of nanocrystalline layer indicates that the grains begin to grow obviously at annealing for 400 °C, and abnormal grain growth also occurs in individual grains. Due to grain growth and stress relaxation during annealing, the microhardness slightly decreases at 400 °C. In spite of this, the majority of grains are still nanocrystalline, ranging from about 30 to 60 nm. It demonstrates that the nanocrystalline layer has high thermal stability.
Keywords: Surface nanocrystallization; Microhardness; Thermal stability; Treatment duration; Low carbon steel;
Preparation of AgInS2 nanoparticles by a facile microwave heating technique; study of effective parameters, optical and photovoltaic characteristics by Azadeh Tadjarodi; Amir Hossein Cheshmekhavar; Mina Imani (449-456).
Display Omitted► AgInS2 nanoparticles were prepared by a facile microwave heating process. ► The change of reaction conditions led to alter the particle size of the products. ► The uniform thin film of product was provided by screen printing technique. ► The energy conversion efficiency of 1.58% was obtained for optimal product.In this work, AgInS2 (AIS) semiconductor nanoparticles were synthesized by an efficient and facile microwave heating technique using several sulfur sources and solvents in the different reaction times. The SEM images presented the particle morphology for all of the obtained products in the arranged reaction conditions. The particle size of 70 nm was obtained using thioacetamide (TAA), ethylene glycol (EG) as the sulfur source and solvent, respectively at the reaction time of 5 min. It was found that the change of the mentioned parameters lead to alter on the particle size of the resulting products. The average particle size was estimated using a microstructure measurement program and Minitab statistical software. The optical band gap energy of 1.96 eV for the synthesized AIS nanoparticles was determined by the diffuse reflectance spectroscopy (DRS). AgInS2/CdS/CuInSe2 heterojunction solar cell was constructed and photovoltaic parameters, i.e., open-circuit voltage (V oc), short-circuit current (J sc) and fill factor (FF) were estimated by photocurrent–voltage (I–V) curve. The calculated fill factor of 30% and energy conversion efficiency of 1.58% revealed the capability of AIS nanoparticles to use in the solar cell devices.
Keywords: Microwave; Nanoparticles; Optical properties; Solar cell; AgInS2;
Phase formation and microstructure evolution of arc ion deposited Cr2AlC coating after heat treatment by J.J. Li; Y.H. Qian; D. Niu; M.M. Zhang; Z.M. Liu; M.S. Li (457-464).
► Cr2AlC coating was prepared by arc ion plating combined with post annealing. ► The coating deposited by arc ion plating without heating was amorphous. ► Amorphous coating transformed to crystalline Cr2AlC after annealing at 620 °C in Ar.Due to the excellent oxidation and hot corrosion resistance and matched thermal expansion coefficient to normal alloys, Cr2AlC has potential applications as high-temperature protective coating. In the present work, the preparation of Cr2AlC coating has been achieved through cathodic arc deposition method combined with heat post-treatment. It was found that the coating, deposited from Cr2AlC compound target in the unintentional heating condition, was amorphous. After annealing at 620 °C in Ar for 20 h, the amorphous Cr–Al–C coating happened to crystallize and transformed to crystalline Cr2AlC as the major phase. It is obvious that the formation temperature of Cr2AlC was decreased from about 1050 °C for sintered bulk to around 620 °C for the as-deposited coating, resulting from the homogeneous mixture of the Cr, Al and C at atomic level in the Cr–Al–C coating. Apart from crystalline Cr2AlC, the annealed coating also contained AlCr2 and little Cr7C3. AlCr2 formed due to the loss of C during deposition, and little Cr7C3 always existed in the sintered Cr2AlC compound target as impurity phase.
Keywords: Cr2AlC; Coating; Cathodic arc deposition; Microstructure;
A study of photocurrent spectrum of porous ZnO film sensitized by metal chloride solutions by Qicheng Yang; Huayao Li; Changsheng Xie; Qiang Zhu (465-470).
Display Omitted► A platform that can perform the photocurrent spectrum measurement has been designed. ► Porous ZnO Film was sensitized by metal chloride solutions. ► Sensitization improved VZn concentration near the interface of ZnO nanoparticles. ► We observed two peaks in the past photocurrent spectrum of ZnO film sensitized by AlCl3. ► Photoresponse mechanism was investigated.In order to study the ZnO photoresponse mechanism, a platform that can perform the photocurrent spectrum measurement has been designed. By using our platform, the photocurrent spectrum of porous ZnO film sensitized by metal chloride solutions was obtained. We used the screen printing technique to fabricate the material chip. The measurements were performed in dry air (relative humidity 15%) and at room temperature. We observed two peaks in the photocurrent spectrum. The peak at 380 nm is assigned to the exciton transition. The shoulder peak at 480 nm is owed to surface states introduced by sensitization and we find VZn plays an important role on this phenomenon. A model is proposed to explain the phenomenon. Furthermore, it is suggested that our platform is a useful tool for photoresponse research and can offer an effective guidance for further investment of light activated gas sensors.
Keywords: Photocurrent spectrum; ZnO; Sensitization; Surface states; Zinc vacancies;
Gold on amine-functionalized magnetic nanoparticles: A novel and efficient catalyst for hydrogenation reactions by Fengwei Zhang; Na Liu; Ping Zhao; Jian Sun; Peng Wang; Wen Ding; Juntao Liu; Jun Jin; Jiantai Ma (471-475).
The reduction of 4-nitrophenol over Fe3O4@PEI-Au catalyst in the presence of NaBH4 and the color of reaction mixture changed from bright yellow to colorless.Display Omitted► A facile one-pot method was put forward to prepare amine-functionalized magnetite nanoparticles. ► The catalyst Fe3O4@PEI-Au is highly economical and easy-to-prepare. ► The catalyst showed high activity for reduction 4-nitrophenol to 4-aminophenol at the presence of NaBH4. ► The catalyst was easily recovered from the reaction mixture with external magnetic field. ► The catalytic efficiency for reduction 4-nitrophenol remains unaltered even after 10 repeated cycles.A facile method is presented for the immobilization of gold nanoparticles on polyethyleneimine functionalized magnetite. The catalyst was characterized by TEM, XRD, TGA, FT-IR, XPS and VSM. This catalyst afforded a fast conversion of the 4-nitrophenol to 4-aminophenol at the presence of NaBH4, and an excellent yield was still achieved after it was reused ten times.
Keywords: Magnetic nanoparticles; Gold nanoparticles; Polyethyleneimine; 4-Nitrophenol; Hydrogenation reactions;
Microstructural revolution of CIGS thin film using CuInGa ternary target during sputtering process by Kuang-Hsiang Liao; Cherng-Yuh Su; Yu-Ting Ding; Cheng-Tang Pan (476-480).
► CuInGa (CIG) ternary targets were prepared by vacuum arc remelting. ► The sputtering energy has a great influence on microstructure of CIG films. ► Increase in sputtering energy resulted in phase transformation and indium loss. ► The surface roughness of CIGS films is determined by the morphology of precursors. ► Rough surface enriched in In lead to poor crystalline CIGS containing InSe phases.CuInGa (CIG) ternary targets were prepared by vacuum arc remelting and used to deposit CIG thin films through direct current (DC) sputtering. We adjusted the sputtering energy (1–2 kWh) by tuning both the sputtering power and the accumulative sputtering time. The impact of the varying sputtering energy on the microstructure of CIG targets and thin films was subsequently investigated. The experimental results indicated that the compositional uniformity of CIG targets is strongly influenced by this parameter. CIG thin films with a flat topography, low porosity, and dense grain boundaries were obtained when targets were accumulatively sputtered at 1 kWh. These films showed good compositional uniformity while the CIG targets were found to maintain their microstructural characteristics as compared to their as-melted counterparts. On the other hand, Cu(In,Ga)Se2 (CIGS) thin films, obtained by a selenization process, exhibited large faceted grains composed of a single chalcopyrite phase with a preferred orientation along the (1 1 2) plane. Accumulative sputtering of CIG targets at higher energies (e.g., 2 kWh) resulted in phase transformation and loss of In material as a result of an excess of residual heat budget on the surface generated by Ar ions bombardment. The CIG thin films thus showed an In-rich composition ratio, thereby potentially leading to In-rich CIGS thin films containing traces of an InSe compound.
Keywords: CIGS thin films; CuInGa metallic precursors; Sputtering energy; CIG ternary targets;
Synthesis of highly luminescent graphitized carbon dots and the application in the Hg2+ detection by Yun Liu; Chun-yan Liu; Zhi-ying Zhang (481-485).
Water-soluble and graphitized carbon dots with photoluminescent quantum yield of 25% have been synthesized by the carbonization of ethylene glycol in the presence of concentrated sulfuric acid, which could be used successfully as a label-free fluorescent probe to selectively and sensitively detect Hg2+ even in real water.Display Omitted► Graphitized GCDs were prepared by the carbonization of EG in the presence of H2SO4. ► The photoluminescence QY of water-soluble GCDs reached ∼25% without any passivation. ► The GCDs showed good selectivity and sensitivity for the detection of Hg2+ ions. ► The PL of GCDs could be quenched by Hg2+ ions mainly through a static quenching mechanism.Water-soluble graphitized carbon dots (GCDs) were synthesized by the one-step carbonization of ethylene glycol (EG) at 140 °C in the presence of concentrated sulfuric acid (H2SO4). Without any post-passivation, their quantum yield (QY) of photoluminescence (PL) reached 25%. The fluorescence of GCDs was located at about 400 nm with a full width at half maximum (FWHM) as small as ∼59 nm. The nearly invariable PL position in certain range of excitation wavelength concluded that the good PL of GCDs should be assigned to the bandlike transition similar to general semiconductor. Further investigation showed that they could be used as a label-free fluorescent probe in the selective and sensitive detection of Hg2+.
Keywords: Carbon quantum dot; Photoluminescence; Hg2+ detection; Fluorescent probe;
Electrical transport properties of Al-doped ZnO films by Xin Dian Liu; Jing Liu; Si Chen; Zhi Qing Li (486-490).
► High quality Al:ZnO films were deposited by rf magnetron sputtering technique. ► Metal–semiconductor transition was found in Al:ZnO film with big grain size. ► Both 2% and 4% Al-doped ZnO films are intrinsic metal in electrical transport properties. ► The tunneling effect dominates the temperature behavior of resistivity of Al:ZnO film with small grain size.We systematically investigated the electrical transport properties of 2% Al-doped ZnO films deposited at different temperatures by rf magnetron sputtering method. For film deposited at 650 K, the temperature behavior of resistivity obeys the Bloch–Grüneisen law, i.e., it behaves as metal in electrical transport properties. While the tunneling effect across the grain boundaries governs the temperature behaviors of resistivity of the films deposited at 550 and 600 K. In addition, we found that the temperature dependence of resistivity of 4% Al-doped ZnO films deposited at 600 and 650 K also exhibit metallic characteristics. These observations provide strong experimental supports for the validity of the ab initio band structure results of Al-doped ZnO.
Keywords: 71.20.−b, 72.20.−i, 78.20.Bh; Transparent conducting oxide; Al-doped ZnO; Temperature dependence of resistivity; Metal–semiconductor transition;
Novel synthesis of β-cyclodextrin functionalized CdTe quantum dots as luminescent probes by Xiao-Feng Chen; Min Zhou; Yan-Ping Chang; Cui-Ling Ren; Hong-Li Chen; Xing-Guo Chen (491-496).
A novel, inexpensive procedure for the preparation of highly fluorescent and water-soluble CdTe quantum dots (QDs) using β-cyclodextrin (β-CD) as surface-coating agents was fabricated through the substitution reaction at the C-6 position of mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD) by the ―NH2 of (3-aminopropyl)triethoxysilane-coated CdTe QDs (APTES/CdTe QDs) under mild conditions. The results revealed that β-CD/APTES/CdTe QDs simultaneously possessed unique optical properties of QDs and excellent molecules recognition ability of β-CD through combining their individual distinct advantages.Display Omitted► A novel preparation of β-cyclodextrin (β-CD) functionalized CdTe quantum dots has been constructed. ► The chemicals and reagents used are inexpensive and straightforward. ► This nanomaterial shows highly fluorescence and the molecular recognition properties.A novel, inexpensive procedure for the preparation of highly fluorescent and water-soluble CdTe quantum dots (QDs) using β-cyclodextrin (β-CD) as surface-coating agents was fabricated through the substitution reaction at the C-6 position of mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD) by the ―NH2 of (3-aminopropyl)triethoxysilane-coated CdTe QDs (APTES/CdTe QDs) under mild conditions. X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), ultraviolet and visible (UV–vis) spectrophotometer, and fluorescence (FL) spectrophotometer were used to characterize the obtained nanoparticles, which proved that the CdTe QDs have been effectively modified by β-CD. The quantum yields (QYs) of CdTe QDs, APTES/CdTe QDs and β-CD/APTES/CdTe QDs in water comparative to Rhodamine 6G were about 17%, 12%, and 9%, respectively. A pair of isomer o,p′-DDT and p,p′-DDT was chosen as the template molecules to evaluate the molecular recognition properties of β-CD/APTES/CdTe QDs. The results revealed that β-CD/APTES/CdTe QDs simultaneously possessed unique optical properties of QDs and excellent molecules recognition ability of β-CD through combining their individual distinct advantages.
Keywords: CdTe quantum dots; β-cyclodextrin; Fluorescence; Molecular recognition;
The combination self-cleaning effect of trimethylaluminium and tetrakis (dimethyl-amino) hafnium pretreatments on GaAs by Yan-Qiang Cao; Xue-Fei Li; Ai-Dong Li; Hui Li; Di Wu (497-501).
► The TMA/TDMAH pretreatment was performed by injecting the TMA/TDMAH precursor. ► TMA + TDMAH pretreatment can suppress the formation of native oxides effectively. ► TMA + TDMAH pretreated sample has a thinnest interlayer thickness of ∼0.2 nm. ► TMA + TDMAH pretreated sample shows the best electrical properties. ► TMA + TDMAH pretreatment has better self-cleaning effect than TMA pretreatment.The self-cleaning effect of trimethylaluminium (TMA) and tetrakis (dimethyl-amino) hafnium (TDMAH) pretreatments on GaAs substrates was investigated deeply. The chemical states were carefully characterized by the X-ray photoelectron spectroscopy, which demonstrates that the pretreatment before ALD of dielectric films can suppress the formation of native oxides on GaAs substrates effectively. It is found that the combination of TMA and TDMAH pretreatments has better self-cleaning effect than single TMA pretreatment based on a ligand-exchange reaction mechanism between TMA/TDMAH and the native oxide. The transmission electron microscopy images also show a thinnest interlayer thickness of ∼0.2 nm for the TMA + TDMAH pretreated sample. TMA + TDMAH pretreated samples exhibit significantly improved interfacial and electrical properties such as the highest accumulation capacitance, the least stretch-out of capacitance–voltage curves, and the lowest interface trap density. These results indicate that the surface pretreatment by using the combination of TMA and TDMAH pulses may be a promising approach for the realization of high quality GaAs-based transistor devices.
Keywords: Self-cleaning; Interface; Surface pretreatment; GaAs; High-k thin films;
Structure of NO dimer monolayer on Rh(1 1 1) by T.Q. Wu; P. Zhu; Z.W. Jiao; X.Y. Wang; H.L. Luo (502-507).
► In the (NO)2/Rh(1 1 1) system, the monolayer other than the monomer was calculated. ► The structure is stable if the NO dimer on the Rh surface forms the monolayer. ► The structures of NO dimer, the monolayer and (NO)2/Rh(1 1 1) have been proposed. ► There are five possible structures for NO dimer monolayer on Rh(1 1 1).The first-principle technique has been employed to determine the structure of the NO dimer, the NO dimer molecular chain, the NO monolayer, and the (NO)2/Rh(1 1 1) system. Their potential structures have also been proposed. CASTEP calculation shows that the NO dimer and the monolayer are both self-assembly systems. The model of the NO dimer monolayer on Rh(1 1 1) is not unique because five models possibly exist. At this time, NO is a dimer, not two monomers. The best ones are the N―N bond in the NO dimer parallel to the surface in fcc-hollow and hcp-hollow sites.
Keywords: NO dimer monolayer; CASTEP; First-principle theory; Molecular self-assembly;
Morphology evolvement of CeO2 cap layer for coated conductors by Yudong Xia; Jie Xiong; Fei Zhang; Yan Xue; Lili Wang; Pei Guo; Pengju Xu; Xiaohui Zhao; Bowan Tao (508-512).
► We investigated the morphology of CeO2 cap layers influence by substrate temperature and deposition rate. ► AFM exhibited the grain shape grown from granule to cluster with the temperature increasing, the grain size decreased as the sputter power increased, and their mechanisms were proposed. ► The root mean square surface roughness of the best sample was 1.8 nm over a 3 μm × 3 μm area. ► The YBCO layer with thickness of 1.36 μm exhibited a J c of 1.72 MA/cm2 at 77 K.The CeO2 cap layer were deposited on yttria-stabilized zirconia (YSZ)/Y2O3 buffered Ni–5 at.%W (Ni–W) substrate by direct-current magnetron reactive sputtering for YBa2Cu3O7−δ (YBCO) coated conductors. Morphology evolvements of CeO2 cap layers on the substrate temperature and deposition rate were investigated. Atomic force microscope exhibited the grain shape grown from granule to cluster with the temperature increasing, the grain size decreased as the sputter power increased, and their mechanisms were proposed. The root mean square surface roughness of the best sample was 1.8 nm over a 3 μm × 3 μm area. Moreover, YBCO films deposited on the CeO2/YSZ/Y2O3 buffered Ni–W substrates using pulsed laser deposition (PLD) achieved the critical current density J c of about 1.72 MA/cm2 at 77 K and self field.
Keywords: YBa2Cu3O7−δ (YBCO) coated conductors; Surface morphology; CeO2 cap layer; Reactive sputtering;
The role of tin-promoted Pd/MWNTs via the management of carbonaceous species in selective hydrogenation of high concentration acetylene by Elaheh Esmaeili; Yadollah Mortazavi; Abbas Ali Khodadadi; Ali Morad Rashidi; Mehdi Rashidzadeh (513-522).
► Synthesis of highly active tin-promoted catalysts by polyol method for selective hydrogenation of high concentration of acetylene. ► A positive change in the catalytic activities of tin-promoted catalysts results from distinct geometric and electronic effects. ► Change in the coverage of acetylenic overlayers for different temperature regions corresponds to the change of the number of isolated adsorption sites. ► The isolated adsorption sites are responsible for the enhancement of selectivity to ethylene with increased temperatures, via the management of the carbonaceous species over the catalyst surface.In the present study, Pd/MWNTs are synthesized using polyol process and modified by tin as a promoter for selective hydrogenation of high concentrated acetylene feedstock. Polyol method results in highly dispersed nanoparticles with a depletion of particle size for tin-promoted Pd catalysts as characterized by TEM. Tin promoter plays a considerable role in hydrogenation of pure acetylene stream. This is attributed to formation of Pd2Sn structural phase, confirmed by XRD and TPR techniques, composed mainly of intermetallic species. Catalytic behavior of tin-promoted Pd catalysts is affected by geometric and electronic factors which are more pronounced in the case of Sn/Pd = 0.25. A discontinuity in Arrhenius plots for the Sn-promoted catalysts is appeared, which seems to be due to a kinetic factor as a result of change in acetylene coverage on Pd metallic ensembles at low and high temperature ranges. Higher selectivity of the catalysts to ethylene is attributed to the presence of more isolated adsorption sites on the catalyst surface originated from both intermetallic compounds confirmed by XPS and the ones formed via the carbonaceous species upon the acetylene hydrogenation reaction.
Keywords: Polyol process technique; Selective acetylene hydrogenation; Geometric and electronic effects; Carbonaceous species; Isolated adsorption sites;
Frequency analysis of micropillar structured surfaces: A characterization and design tool for surface texturing by Laura Vepsäläinen; Pertti Pääkkönen; Mika Suvanto; Tapani A. Pakkanen (523-531).
► Systematically controlled, ordered and randomized, injection-molded micropillar textured polymer surfaces. ► Three-dimensional texture characterization by surface texture analysis which offers structure periodicity and roughness at various spatial frequencies. ► Texture analysis combined with texture design which enables the theoretical inspection of desired structures.Various systematically controlled, ordered and randomized micropillar structures were fabricated onto polypropylene by injection molding. Mold inserts were prepared by a micro-working robot. The advantages of this simple surface texturing application include the rigorous control of the pillar positions and the use of a variety of polymers. The textured surfaces were characterized both in horizontal and vertical directions. Power spectral density (PSD) curves combined with filtered root-mean-square (RMS) values provide structure periodicities and roughness differences between various spatial frequencies, respectively. The developed characterization tool is useful in texture mimicking when substantial periodicities and roughness is obtained and imitated in the input data of the micro-working robot. Hence, injection molded micropillar surfaces can possess similar spatial frequency and roughness features to that of mimicked surfaces.The developed characterization method was also connected to the texture design. The height profiles of structures corresponding to the fabricated surfaces were predicted from the experimental input data of the micro-working robot, and the PSD curves were generated to obtain the connection between experimental and predicted structures. The rigorous correspondence between the experimental and predicted structures and the filtered RMS values indicates that the developed design tool enables the theoretical inspection of desired structures. This can also be used in texture mimicking to expedite experimental work.
Keywords: Texture; Characterization; Micropillar; Injection molding; PSD curve; Fourier filtering;
Synthesis and properties of PANI/SiO2 organic–inorganic hybrid films by Qingjie Yu; Jianming Xu; Jie Liu; Baoxia Li; Yongjun Liu; Yuanyuan Han (532-535).
► PANI/SiO2 hybrid films were prepared directly from polyaniline emulsion solution and tetraethyl orthosilicate. ► Hybrid films prepared have a homogeneous and smooth surface without detectable cracks. ► Low TEOS/ANI molar ratio is prone to obtain a smooth surface and exceptional corrosion protection properties. ► The increase of TEOS content tend to reduce corrosion resistance ability.PANI/SiO2 organic–inorganic hybrid films were prepared directly from polyaniline (PANI) emulsion solution and tetraethyl orthosilicate (TEOS) by sol–gel process. The evolution of phase, morphology and corrosion resistance ability of PANI/SiO2 hybrid materials were characterized by TG, FTIR, SEM and potentiodynamic polarization analysis. It was demonstrated that PANI/SiO2 organic–inorganic hybrid films have a homogeneous and smooth surface without detectable cracks. Potentiodynamic polarization analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. However, the increase of TEOS content in PANI/SiO2 organic–inorganic hybrid materials tends to exhibit brittleness and micro-cracks which will lead to the deterioration of corrosion resistance ability.
Keywords: PANI/SiO2 hybrid films; Emulsion polymerization; Corrosion resistance ability;
Structural refinement and photocatalytic activity of Fe-doped anatase TiO2 nanoparticles by S.D. Delekar; H.M. Yadav; S.N. Achary; S.S. Meena; S.H. Pawar (536-545).
Display Omitted► Facile experimental route to synthesize iron-doped anatase titania nanoparticles. ► Decrease in the band gap energy with increase in the iron-content in titania. ► Refined structural data of undoped/doped TiO2 nanoparticles. ► Proper substitution of Ti+4 sites with Fe3+ ions in titania host lattice.Colloidal iron-doped (0.0–3.0 mol%) TiO2 nanoparticles have been synthesized using sol–gel method and characterized by thermogravimetric analysis, powder XRD, IR spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). The characteristic features of nanocrystalline TiO2 in tetragonal anatase phase were confirmed by powder XRD studies with Rietveld refinement. Rietveld refinement data gave 2.59, 3.21 value of R B for pure TiO2 and 3.0 mol% Fe:TiO2 nanoparticles, respectively. Raman bands at 639 cm−1, 517 cm−1, and 395 cm−1 further confirmed the pure anatase phase in all samples. TEM pictures revealed the non-spherical nanoparticles having sizes in between 7 and 14 nm. Surface area and pore volume for the samples were in the range of 150–87 m2/g and 0.35–0.21 cm3/g, respectively. The magnetic and optical properties of the nanoparticles were investigated by using SQUID magnetometer and UV–vis spectroscopy. The undoped titania nanoparticles were diamagnetic; whereas all doped titania samples were paramagnetic. The optical band gap of titania nanoparticles were found to decrease with the increase in iron content in host lattice. The photocatalytic performance of the iron-doped TiO2 nanoparticles for the conversions of p-nitrobenzaldehyde to p-nitrobenzoic acid as well as photodegradation of Rhodamine 6G was also investigated.
Keywords: Titanium oxide; Sol–gel method; Iron doping; Rietveld refinement; Photochemical transformations;
Investigation of ZnS–SiO2/Ag/ZnS–SiO2 as high stable transparent and conductive multilayer films by Guoyun Long; Yongyou Geng (546-552).
► Novel transparent conductive ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were prepared. ► The structure was theoretically designed using the characteristic matrix theory. ► The sample showed a low R s of 9.7 Ω/sq and a high transmittance of 88.4%. ► The samples were assessed by an accelerated aging test and showed high stability.Novel transparent conductive ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were prepared on K9 glass substrates by magnetron sputtering at room temperature. The structure of ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were theoretically designed and the optimal thickness of each layer was determined (45 nm/11 nm/45 nm). To obtain better optical and electrical properties, the ZnS–SiO2/Ag/ZnS–SiO2 samples were annealed at various temperatures. The optical, electrical, and structural characteristics of the ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were then investigated. The results show that when the annealing temperature was 200 °C, the sample exhibited a low sheet resistance of 9.7 Ω/sq and a high optical transmittance of 88.4%. For the sample annealed at 200 °C, the average transmittance in the visible range (380–780 nm) was calculated and determined as 84.1%. The effects of humidity and temperature on the samples were assessed by an accelerated aging test. The results demonstrate the high damp heat stability of ZnS–SiO2/Ag/ZnS–SiO2 multilayer films.
Keywords: Transparent conductive films; ZnS–SiO2; Annealing; Aging; Stability;
Theoretical investigation of pristine and functionalized AlN and SiC single walled nanotubes as an adsorption candidate for methane by Zabiollah Mahdavifar; Maryam Haghbayan (553-562).
Display Omitted► Potential of pristine and functionalized AlN and SiC single walled nanotubes as an adsorption device for CH4 theoretically were studied. ► Quantum chemical calculations show that the CH4 molecule physisorbed on T n (n = 1 and 2) sites on the surface of pure AlN and SiC nanotubes. ► CH4 molecule tends to be strongly physisorbed to the Ni-doped AlN and SiC nanotubes with appreciable adsorption energy. ► A considerable amount of charge transfer during the adsorption process on Ni-doped AlN and SiC nanotubes may account for the changes of the electronic properties.In order to search for novel nanomaterial to adsorb methane (CH4) molecule, the adsorption of CH4 on the hydrogenated edges of armchair (4,4) aluminum nitride (AlN) and silicon carbide (SiC) nanotubes has been systemically investigated using two different density functional theory (DFT) methods. Two MPW1PW91 and PBEPBE functional are employed in all calculations for the considered structures, adsorption energy, and NBO analysis. The CH4 molecule physisorbed on T n (n = 1 and 2) sites on the surface of pure AlN and SiC nanotubes with an adsorption energy of about −4.42 and −1.43 kJ/mol respectively. The properties of CH4 molecule adsorbed on Ni-doped AlN and SiC nanotubes are also investigated. The adsorption energy rises to about −60.36 and −39.26 kJ/mol for AlN―Ni―CH4 and SiC―Ni―CH4 respectively, when the CH4 adsorbed to Ni-doped nanotubes. Compared with the weak adsorption on pure AlN and SiC nanotubes, CH4 molecule tends to be strongly physisorbed to the Ni-doped AlN and SiC nanotubes with appreciable adsorption energy. The increase in adsorption energy is due to the charge transfer from Ni-doped AlN and SiC nanotubes to the CH4 molecule. A considerable amount of charge transfer during the adsorption process on Ni-doped AlN and SiC nanotubes may account for the changes of the electronic properties. With the adsorption of CH4 molecule on functionalized nanotubes, the band gap of AlN―Ni―CH4 and SiC―Ni―CH4 systems are increased, thus leading to decreased reactivity of the systems, the stability of the systems increased. These observations show that functionalized AlN and SiC nanotubes are highly sensitive toward CH4 molecule. Moreover, the present results may be useful for the design of AlN and SiC nanotubes based nanomaterials candidates such as adsorbent and storage.
Keywords: DFT calculations; AlNNT; SiCNT; Nickel; Functionalized nanotubes; Methane adsorption;
Nd:YVO4 laser removal of graffiti from granite. Influence of paint and rock properties on cleaning efficacy by T. Rivas; S. Pozo; M.P. Fiorucci; A.J. López; A. Ramil (563-572).
► Cleaning using NdYVO4 laser at 355 nm of four different graffiti colours applied on granites. ► Analysis of the influence of paint composition and properties of rocks on the process. ► Composition of the paints and, in turn reflectance, determine the removal effectiveness. ► The laser removal is not conditioned by properties of the stones.This paper presents the cleaning efficiency results for four differently coloured graffiti paints applied to two types of granitic stone by Nd:YVO4 laser at 355 nm. The paints were characterized in terms of mineralogy and chemistry using x-ray fluorescence, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM); paint absorbance in the ultraviolet–visible-infrared range (200–2000 nm) was also assessed. The studied granites had different mineralogy, texture and porosity properties. Cleaning efficiency was evaluated by polarized microscopy, SEM, FTIR spectroscopy and spectrophotometer colour measurements. The results indicate differences in the effectiveness of surface cleaning for the blue, red and black paints as opposed to the silver paint, mainly attributed to chemical composition. No evidence was found that the granite properties had a bearing on laser effectiveness, although the degree, type and spatial distribution of transgranular fissures in the stone affected the overall assessment of cleaning effectiveness. Polarized light microscopy observations and colour measurements showed that the intensity and distribution of fissures affect the depth of paint penetration, ultimately affecting the cleaning efficiency for both granites.
Keywords: Laser cleaning; Granite; Graffiti; Cultural heritage; Ablation threshold;
Synthesis and electrochemical performance of CoO/graphene nanocomposite as anode for lithium ion batteries by Mei Zhang; Mengqiu Jia; Yuhong Jin; Xiangrui Shi (573-578).
► Fabrication of graphene and CoO nanocomposite for lithium ion batteries anode. ► In situ method leads to the small-sized CoO with high dispersion on graphene. ► Such well-designed structure results in fine and strong interfacial interaction. ► The nanocomposite shows high reversible capability and long cycling life.We developed one-spot in situ synthesis method to fabricate CoO/reduced graphene oxide (CoO/RGO) nanocomposite by directly employing C4H6O4·Co·4H2O and hydrophilic graphite oxides as raw materials. The electrochemical performances of the as-prepared CoO/RGO nanocomposite were evaluated in coin-type cells. It delivers a high reversible capacity of 740.7 mAh g−1 at 100 mA g−1, and retains a capacity retention of 95% after 50 cycles. Even after 435 cycles at various rates from 100 to 4000 mA g−1, the capacity still retains 577.9 mAh g−1 when the current density is back to 100 mA g−1. The extraordinary performance is ascribed to the well-designed structure of the CoO/RGO nanocomposite. The small-sized, high crystalline and dense CoO nanoparticles uniformly disperse on conductive graphene substrates, supplying large number of accessible active sites for lithium-ion insertion, short diffusion length for lithium ions, good conductivity and strong interfacial interaction between CoO nanoparticles and RGO nanosheets, which are beneficial for high capacity and long cycling stability.
Keywords: Graphene; CoO nanoparticles; Nanocomposite; Anode; Lithium ion batteries;
Laser-induced novel patterns: As smart strain actuators for new-age dental implant surfaces by Serap Çelen; Hüseyin Özden (579-585).
► It is time for that paradigm shift and for an exploration of novel surfaces. ► We developed novel 3D smart surfaces as strain actuators by nanosecond laser pulse energies. ► We analyzed these smart surface morphologies using FEM. ► We estimated their internal stiffness values which play a great role on stress shielding effect. ► We gave the optimum operation parameters.Surface morphologies of titanium implants are of crucial importance for long-term mechanical adaptation for following implantation. One major problem is the stress shielding effect which originates from the mismatch of the bone and the implant elasticity. It is time for a paradigm shift and for an exploration of novel smart surfaces to prevent this problem. Several surface treatment methods have traditionally been used to modify the surface morphology of titanium dental implants. The laser micro-machining can be considered as a unique and promising, non-contact, no media, contamination free, and flexible treatment method for modifying surface properties of materials in the biomedical industry. The aim of the present study is two folds; to develop novel 3D smart surfaces which can be acted as strain actuators by nanosecond laser pulse energies and irradiation strategies. And analyze these smart surface morphologies using finite element methods in order to estimate their internal stiffness values which play a great role on stress shielding effect. Novel 3D smart strain actuators were prepared using an ytterbium fiber laser (λ = 1060 nm) with 200–250 ns pulse durations on commercial pure titanium dental implant material specimen surfaces and optimum operation parameters were suggested.
Keywords: Laser micro-machining; Dental implant; 3D smart surface patterns; Ytterbium fiber laser;
Swift heavy ion induced topography changes of Tin oxide thin films by Manoj K. Jaiswal; Avesh Kumar; D. Kanjilal; T. Mohanty (586-590).
► In this work the grain size and surface roughness of nanocrystalline SnO2 thin film are presented as a function of ion fluence. ► Swift heavy ion irradiation induces point defects in SnO2 which act as nucleation centers for nanocrystallization. ► The variation of defect concentration with ion fluence is correlated to the observed surface morphology and structural changes in SnO2 thin films.Monodisperse tin oxide nanocrystalline thin films are grown on silicon substrates by electron beam evaporation method followed by 100 MeV silver ion bombardment with varying ion fluence from 5 × 1011 ions cm−2 to 1 × 1013 ions cm−2 at constant ion flux. Enhancement of crystallinity of thin films with fluence is observed from glancing angle X-ray diffraction studies. Morphological studies by atomic force microscopy reveal the changes in grain size from 25 nm to 44 nm with variation in ion fluence. The effect of initial surface roughness and adatom mobility on topography is reported. In this work correlation between ion beam induced defect concentration with topography and grain size distribution is emphasized.
Keywords: Nanostructures; Surface morphology; Roughness exponent; Defects; Ion bombardment; Ion fluence;
Effects of Ti and TiC ceramic powder on laser-cladded Ti–6Al–4V in situ intermetallic composite by O.F. Ochonogor; C. Meacock; M. Abdulwahab; S. Pityana; A.P.I. Popoola (591-596).
► The wear resistance of the laser clad surfaces was enhanced significantly with fifteen-folds wear rate reduction. ► Micro-hardness of the clad zones indicated a significant improvement of over two-folds greater than the substrate. ► Microstructures showed fine crystal grains distribution of ceramic particles that formed interstitial carbides in the titanium matrix composites.Titanium metal matrix composite (MMCs) was developed on titanium alloy (Ti–6Al–4V) substrate with the aim of improving the hardness and wear properties by laser cladding technique using a Rofin Sinar 4 kW Nd: YAG laser. Wear investigations were carried out with the aid of three body abrasion tester. The resultant microstructure show homogeneous distribution of TiC particles free from cracks and pores. Multiple track deposited systems with 50% overlap revealed micro-hardness increase from 357.3 HV0.1for the substrate reaching a peak as high as 922.2 HV0.1 for 60%Ti + 40%TiC and the least 665.3 HV0.1 for 80%Ti + 20%TiC MMCs. The wear resistance of the materials improved significantly, indicating a fifteen-fold wear rate reduction due to the proper distribution of ceramic particles thereby forming interstitial carbides as revealed by the X-ray diffraction spectrum.
Keywords: Interstitial carbides; Metal matrix composites; Ti6Al4V; Titanium carbide;
High temperature oxidation and corrosion behaviour of Ni/Ni–Co–Al composite coatings by Meenu Srivastava; J.N. Balaraju; B. Ravisankar; C. Anandan; V.K. William Grips (597-607).
► Aim is development of high temperature Ni/Ni–Co–Al coating through electrodeposition. ► Coatings characterized extensively for the microstructural changes. ► Evaluated for high temperature oxidation and hot corrosion behaviour. ► Ni―Co aluminide with optimum Co of 30 wt% suitable for high temperature applications.In the present study, Ni/Ni–Co–Al composite coatings were developed by a potentially simple, scalable, non-vacuum technique namely electrodeposition. These coatings were characterized for their microhardness, oxidation and hot corrosion behaviour. An increase in Co content in the matrix from 8 wt% to 70 wt% led to an increase in the Al particle incorporation from 12 wt% to 21 wt%. A change in the surface morphology of the coatings with variation in Co content was seen. The oxidation behaviour of the coatings was studied at temperatures in the range of 400 °C to 1000 °C. The influence of vacuum treatment on the high temperature behaviour of the coatings was also investigated. The intermetallic aluminide phase formation was observed in the temperature range of 600–800 °C and a homogenized structure was seen at 1000 °C. The oxidation rate in terms of weight gain was marginally lower for vacuum pretreated Ni―Al coating annealed at 1000 °C. A significant increase in the oxidation rate was exhibited by Ni–70Co–Al coating beyond 800 °C showing its poor oxidation behaviour. The characterization studies revealed the formation of stable alumina in the case of Ni―Al while, metastable alumina was observed in Ni–Co–Al coatings. The hot corrosion studies showed that Co rich Ni–Co–Al exhibited better resistance compared to Ni rich coatings. An optimum cobalt content of 30 wt% was desirable for high temperature oxidation and corrosion resistance.
Keywords: Ni–Co–Al; Aluminides; High temperature coating; High temperature oxidation; Hot corrosion; Microstructure;
Improved corrosion resistance on biodegradable magnesium by zinc and aluminum ion implantation by Ruizhen Xu; Xiongbo Yang; Kai Wong Suen; Guosong Wu; Penghui Li; Paul K. Chu (608-612).
► Zn and Al ions were implanted into Mg to simulate AZ alloys. ► Initial corrosion resistance of the implanted sample was much larger than Mg, AZ31 and AZ91. ► Ions implantation produces compact oxide film and β-Mg17Al12 phases on the surface.Magnesium and its alloys have promising applications as biodegradable materials, and plasma ion implantation can enhance the corrosion resistance by modifying the surface composition. In this study, suitable amounts of zinc and aluminum are plasma-implanted into pure magnesium. The surface composition, phases, and chemical states are determined, and electrochemical tests and electrochemical impedance spectroscopy (EIS) are conducted to investigate the surface corrosion behavior and elucidate the mechanism. The corrosion resistance enhancement after ion implantation is believed to stem from the more compact oxide film composed of magnesium oxide and aluminum oxide as well as the appearance of the β-Mg17Al12 phase.
Keywords: Biomaterials; Magnesium; Ion implantation; Corrosion;
Study on the effect of surface modifier on self-aggregation behavior of Ag nano-particle by Song Li; Peng Liu; Qisui Wang (613-618).
The typical TEM images of the silver NPs were close to mono-disperse spherical with diameters about 10 nm. The Ag/PVP NPs are highly crystalline, and the interplanar spacing of 0.235 nm is close to the separation between the (1 1 1) crystallographic planes of cubic Ag/PVP.Display Omitted► Four kinds of the mono-dispersed silver NPs with different capping agent were synthesized with diameters about 7, 3, 10, and 5 nm, respectively. ► HRTEM characterization also revealed the Ag/PVP, Ag/PAN, Ag/OA NPs are highly crystalline and the interplanar spacing was calculated. ► FTIR and TG-DSC were used to characterize the binding group of four molecules on Ag nano-particle's surface. ► The Effect of Surface Modifier on Self-Aggregation of Ag Nano-particle was discussed.In this study, four kinds of Ag nano-particles were synthesized with poly (vinylpyrrolidone) (PVP), polyaniline (PAN), l-cysteine (l-cys), and oleic acid (OA) as modified groups. The properties of these Ag nano-particles were characterized by several techniques. Transmission electron microscopy (TEM) observation show four samples were close to monodisperse spherical with diameters about 7, 3, 10, and 5 nm, respectively. The interplanar spacing was calculated and the crystal was discussed with X-ray diffraction (XRD) results. Both Fourier transform infrared spectra (FTIR) and thermogravimetry (TG)-differential scanning calorimetry (DSC) has revealed the binding group of four molecules on Ag nano-particle's surface. After the Ag nanoparticles (NPs) deposited onto the substrate, surface modifier would collapse on the particle surface. Ag nanoparticles are easier to self-aggregate for the weaker binding of surface modifier. As a result, the conductive film is formed. The effect of modified group and temperature were discussed on the conductivity of the silver films.
Keywords: Silver nanoparticle; Binding; Capping agent; Self-aggregation; Conductivity;
Ab initio investigation of Al- and Ga-doped single-walled boron nitride nanotubes as ammonia sensor by Alireza Soltani; Shima Ghafouri Raz; Vahid Joveini Rezaei; Aliakbar Dehno Khalaji; Mohammad Savar (619-625).
► The electronic properties of NH3 on Al- and Ga-doped (8, 0) and (5, 5) BNNT are studied. ► The adsorption energy for NH3 on Al-doped (8, 0) BNNT is higher than that of Ga-doped (8, 0) BNNT. ► The relation between adsorption energy and charge transfer was investigated.We performed first-principles calculations on the ammonia (NH3) adsorption properties with zigzag and armchair single-walled BN nanotubes (SWBNNTs) using B3LYP/6-31G* basis set implemented in Gaussian 98 program. We considered the ammonia adsorption on structural and electronic properties of Al- and Ga-doped (8, 0), (5, 5) BNNTs. The adsorption energy for the most stable configuration of NH3 on Al-doped (8, 0) BNNT is about −0.182 eV, which is typical for the chemisorptions. We determined that both aluminum and gallium doping can significantly enhance the adsorption energy of NH3/BNNTs complexes. Our electronic results reveal that there is a significant orbital hybridization between two species in adsorption process being an evidence of covalent interaction.
Keywords: BNNT; NH3; DFT; Doping metal; Chemisorption;
Modeling of altered layer formation during reactive ion etching of GaAs by A. Mutzke; A. Rai; R. Schneider; E.J. Angelin; R. Hippler (626-632).
► Experimental result showing the preferential sputtering of GaAs (150 keV Ar+ and thermal O on GaAs) during reactive ion beam etching (RIBE) has been reported. ► A model based on binary collisions (SDTrimSP) is presented to simulate RIBE. ► The model is used to explain the reported experimental data and also the results by Grigonis and co-workers .The binary collision based SDTrimSP model has been used to simulate the reactive ion beam etching (RIBE) of GaAs in the presence of energetic Ar ions and thermal O atoms. It includes the collisional effects, diffusive processes and chemical reactions taking place in the system. The model parameters are fitted using the experimental observations of Grigonis and co-workers  and validated with the experimental results obtained during the GaAs ion etching presented in this paper. A detailed analysis is presented to understand the effect of the diffusive processes and the role of O during RIBE of GaAs. It is shown how the presence of damage caused by the energetic Ar coupled with the presence of thermal O opens up chemical reaction channels which eventually leads to the preferential sputtering of Ga observed at the ion etching facility at University of Greifswald.
Keywords: GaAs; SDTrimSP; Sputtering; Etching;
The role of trivalent cations and interlayer anions on the formation of layered double hydroxides in an oxic-CO2 medium by Susanta Paikaray; M. Jim Hendry (633-639).
► Strong agglomeration of nano particles. ► Atmospheric CO2 easily incorporates as interlayer anion even in presence of dissolved SO4 2−. ► Fe3+ substitution attracts excess anion vs. Al3+, both SO4 2− and CO3 2−, due to high charge deficiency. ► Iron (Fe3+) causes increase in lattice parameters compared to Al3+. ► MgAlCO3/SO4-type LDHs have better cation ordering compared to MgFeCO3/SO4-type LDHs.Most common occurrences of magnesium (Mg2+), aluminum (Al3+), iron (Fe3+), carbonate (CO3 2−), and sulfate (SO4 2−) in environmental settings can lead to formation of layered double hydroxides. This study investigated the role of different trivalent cations and divalent interlayer anions on the physicochemical properties of hydrotalcite-like layered double hydroxides. Hydrotalcite-like compounds (HTLCs) were synthesized at ambient temperature by co-precipitation while maintaining Mg2+ as the primary divalent cation and varying Al3+ and Fe3+ as the trivalent cations and SO4 2− and CO3 2− as the interlayer anions. X-ray diffractograms, Raman and infrared spectra, and scanning electron microscopy images confirmed the precipitation of rounded fibrous HTLCs. BET analyses showed that the MgAlCO3-type HTLC had the greatest surface area (101.7 m2/g), followed by MgAlSO4 (93.9 m2/g), MgFeCO3 (81.3 m2/g), and MgFeSO4 (17.8 m2/g). Substitution of Fe3+ increased lattice parameters compared to Al3+ substitution. Incorporation of SO4 2− as an interlayer anion was favored during Fe3+ substitution but reduced the crystallinity of the HTLC. Carbonate was the preferred interlayer anion, but available SO4 2− occupied the interlayer spaces together with CO3 2− if a high charge deficiency was maintained during HTLC precipitation. Two major stages of mass loss occurred (≤250 and 250–450 °C) for all the samples with better thermal stability for SO4 2− vs. CO3 2− as interlayer anion and Al3+ vs. Fe3+ as trivalent cation.
Keywords: Anionic clays; Hydrotalcite formation; Cation substitution effect; Vibrational spectroscopy; Interlayer anion;
Experimental study on the formation and growth of electroless nickel–boron coatings from borohydride-reduced bath on mild steel by Véronique Vitry; Adeline Sens; Abdoul-Fatah Kanta; Fabienne Delaunois (640-647).
► Initiation mechanism of electroless Ni–B on St-37 steel has been identified. ► Different phases of the plating process were observed and identified. ► Influence of chemical heterogeneity on coating morphology was revealed. ► Batch replenishment of the plating bath induces new germination phase.Quality and homogeneity of electroless nickel–boron coatings are very important for applications in corrosion and electronics and are completely dependent on the formation of the deposit.The growth and formation process of electroless nickel–boron was investigated by immersing mild steel (St-37) samples in an un-replenished bath for various periods of time (from 5 s to 1 h). The coatings obtained at the different stages of the process were then characterized: thickness was measured by SEM, morphology was observed, weight gain was recorded and top composition of the coatings was obtained from XPS.Three main phases were identified during the coating formation and links between plating time, instantaneous deposition rate, chemistry of last formed deposit and morphology were established.The mechanism for initial deposition on steel substrate for borohydride-reduced electroless nickel bath was also observed.Those results were confronted with chemistry evolution in the unreplenished plating bath during the process. This allowed getting insight about phenomena occurring in the plating bath and their influence on coating formation.
Keywords: Electroless plating; Growth; Initiation; Nickel–boron;
Dual-scale artificial lotus leaf fabricated by fully nonlithographic simple approach based on sandblasting and anodic aluminum oxidation techniques by Seung-Jun Kim; Tae-Hyun Kim; Jeong-Ho Kong; Yongsung Kim; Chae-Ryong Cho; Soo-Hyung Kim; Deug-Woo Lee; Jong-Kweon Park; Dongyun Lee; Jong-Man Kim (648-654).
► Fully nonlithographic simple method to realize artificial lotus leaf was proposed. ► The proposed cost-effective way enables to fabricate dual-scale superhydrophobic surface efficiently. ► Superior water-repellency and self-cleaning ability was evaluated by dropping and practical tests.This paper reports a micro/nano dual-scaled artificial lotus leaf that is formed on a silicon substrate by simple and inexpensive fully nonlithographic approach, combining a sandblasting technique and an anodic aluminum oxidation (AAO) process. The proposed dual-scaled surface was demonstrated by covering the sandblasted micro-roughened substrate entirely with nano-scale protuberances, and its surface wettability was characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH). The measurements confirmed that the proposed dual-scaled surface can sufficiently ensure superhydrophobicity in the Cassie wetting regime with a high SCA of 159.4 ± 0.5° and a low CAH of 3.9 ± 0.7°, and the surface wetting properties can be improved greatly compared to those of flat, sandblasted micro-roughened and nano-scale protuberance-arrayed surfaces. Through a dropping test, it was observed that the fabricated dual-scaled surface can ensure its superior water-repellency with various levels of the impact velocity. Finally, a self-cleaning ability of the proposed dual-roughened surface was verified experimentally by observing the dynamic rolling-off behavior of the water droplet on the surface covered with contaminants.
Keywords: Dual-scale artificial lotus leaf; Superhydrophobicity; Sandblasting technique; Anodic aluminum oxidation process; Contact angle; Contact angle hysteresis; Cassie wetting mode; Dropping test; Self-cleaning test;
Preparation and tribological properties of surface-modified nano-Y2O3 as additive in liquid paraffin by Lin Yu; Lin Zhang; Fei Ye; Ming Sun; Xiaoling Cheng; Guiqiang Diao (655-659).
► Nano-Y2O3 was for the first time used as lubricant additive in liquid paraffin. ► The nano-Y2O3 modified by a coupling-grafting method shows good dispersibility in liquid paraffin. ► The surface-modified nano-Y2O3 considerably improves the tribological performances of liquid paraffin.Surface-modified nano-Y2O3 was prepared by a coupling-grafting method with vinyl methylerichlorosilane and methyl methacrylate as the coupling agent and grafting agent, respectively. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron micrograph (TEM) and thermal gravimetric analysis (TGA). The tribological properties of the surface-modified nano-Y2O3 as additive in liquid paraffin were evaluated with a four-ball tester. The results show that the nano-Y2O3 keeps its original crystalline structure after surface modification, and the modified nano-Y2O3 forms a core–shell structure with an average particle size of 24.5 nm. The maximum non-seizure load (P B value) and sintered load (P D value) increase by 25% and 26.9%, respectively, when compared with those of liquid paraffin, and the wear scar diameter (WSD) also decrease by 21% when 0.10% surface-modified nano-Y2O3 was added. The protective inorganic–organic film formed by nano-Y2O3 and organic modifiers plays an important role in the improved tribological properties of liquid paraffin.
Keywords: Nano-Y2O3; Surface modification; Coupling-grafting; Lubricant additive;
Preparation, performance and adsorption activity of TiO2 nanoparticles entrapped PVDF hybrid membranes by Xia Zhang; Yang Wang; Yuting You; Hao Meng; Jianghua Zhang; Xinxin Xu (660-665).
Display Omitted► TiO2 nanoparticles hybrid membranes were prepared through an impregnation process. ► TiO2 were deposited on the surface and inner pores of PVDF membranes. ► The hybrid membranes showed good adsorption–desorption property toward Cu2+ ions. ► TiO2 improved the hydrophilicity, permeability and antifouling ability of membrane.The TiO2 nanoparticles entrapped poly(vinylidenefluoride) (PVDF) hybrid membranes were prepared through impregnating the pre-treated PVDF film in the TiO2 suspension. SEM, XRD, TG and ATR-IR analyses were used to character the hybrid membranes. The results showed that the TiO2 nanoparticles with average size about 44 nm were deposited on the surface and inner pores of PVDF films. The pre-treatment of PVDF with cetyltrimethyl ammonium bromide (CTAB) is benefit for TiO2loading. The ATR-IR spectra revealed that physical interaction played important role in the construction of hybrid membranes. The adsorption behavior of Cu2+ on the hybrid membranes was studied, and a promoted adsorption and elution efficiency of PVDF/TiO2 hybrid membranes were observed compared with that of the pristine PVDF film. Meanwhile, the surface contact angle, pure water flux and static adsorption of bovine serum albumin (BSA) on the hybrid membranes were also measured to study the effects of TiO2 nanoparticles. It was found that the TiO2 nanoparticles improved the surface hydrophilicity and permeability of PVDF membranes, and the decreasing adsorption capacity of BSA indicated the promoted antifouling ability of PVDF membranes. Such the PVDF/TiO2 hybrid membranes exhibit potential applications in the separation and pre-concentration of metal ions.
Keywords: PVDF/TiO2 hybrid membrane; Adsorption behavior of Cu2+; Surface hydrophilicity; Permeability; Antifouling ability;
Interfacial mixing in as-deposited Si/Ni/Si layers analyzed by x-ray and polarized neutron reflectometry by Debarati Bhattacharya; Saibal Basu; Surendra Singh; Sumalay Roy; Bhupendra Nath Dev (666-670).
► Room temperature diffusion in Si/Ni/Si trilayer detected through complementary x-ray and polarized neutron reflectometry. ► Analyses of XPNR data generated the construction of the layered structure in terms of physical parameters along with alloy layers created by diffusion. ► Scattering length density information from XPNR provided quantitative assessment of the stoichiometry of alloys formed at the Si/Ni and Ni/Si interfaces.Interdiffusion occurring across the interfaces in a Si/Ni/Si layered system during deposition at room temperature was probed using x-ray reflectivity (XRR) and polarized neutron reflectivity (PNR). Exploiting the complementarity of these techniques, both structural and magnetic characterization with nanometer depth resolution could be achieved. Suitable model fitting of the reflectivity profiles identified the formation of Ni–Si mixed alloy layers at the Si/Ni and Ni/Si interfaces. The physical parameters of the layered structure, including quantitative assessment of the stoichiometry of interfacial alloys, were obtained from the analyses of XRR and PNR patterns. In addition, PNR provided magnetic moment density profile as a function of depth in the stratified medium.
Keywords: x-ray and neutron reflectometry; Interface structure; Magnetic properties;
Structural; morphological; optical and magnetic properties of Mn doped ferromagnetic ZnO thin film by R. Karmakar; S.K. Neogi; Aritra Banerjee; S. Bandyopadhyay (671-677).
► Zn1−x Mn x O (0 < x < 0.05) films were synthesized by sol–gel technique. ► No trace of formation of any impurity phase has been detected. ► Grain size indicates decreasing trend with increasing Mn concentration. ► The optical properties of the films indicate increase in defect or disorder in the system with increasing Mn doping. ► 5 at% Mn doped ZnO film exhibits defect mediated intrinsic ferromagnetic nature up to room temperature with strong presence of antiferromagnetic interaction.The structural, optical and magnetic properties of the Zn1−x Mn x O (0 < x < 0.05) thin films synthesized by sol–gel technique have been analyzed in the light of modification of the electronic structure and disorder developed in the samples due to Mn doping. The films are of single phase in nature; no formation of any secondary phase has been detected from structural analysis. Absence of magnetic impurity phase in these films has been confirmed from morphological study also. Increasing tendency of lattice parameters and unit cell volume has been observed with increasing Mn doping concentration. The incorporation of Mn2+ ions introduces disorder in the system. That also leads to slight degradation in crystalline quality of the films with increasing doping. The grain size reduces with increase in Mn doping proportion. The band gaps shows red shift with doping and the width of localized states shows an increasing tendency with doping concentration. It is due to the formation of impurity band and trapping of Mn atoms, which leads to the generation of the defect states within the forbidden band. Photoluminescence (PL) spectra show gradual decrease of intensity of exitonic and defect related peaks with increasing Mn doping. Defect mediated intrinsic ferromagnetism has been observed even at room temperature for 5 at% Mn doped ZnO film. The strong presence of antiferromagnetic (AFM) interaction reduces the observed ferromagnetic moments.
Keywords: Mn doped ZnO; Sol–gel; Defect; Ferromagnetism;
Resistive switching in reactive cosputtered MFe2O4 (M = Co, Ni) films by C. Jin; D.X. Zheng; P. Li; W.B. Mi; H.L. Bai (678-681).
► Resistive switching characteristics have been found in the spinel oxides MFe2O4 (M = Co, Ni) films at room temperature. ► The MFe2O4 (M = Co, Ni) films were prepared by reactive cosputtering. ► The resistive switching effect was related to the migration of oxygen vacancies under the voltage bias.Resistive switching (RS) characteristics of the spinel oxides MFe2O4 (M = Co, Ni) have been investigated. The current–voltage curves show hysteresis loops that are suitable for RS devices at room temperature. We have demonstrated that the oxygen vacancies determine the path of electrical conduction in the MFe2O4 films. The drift of the oxygen vacancies from high-density region to low-density one makes the conductive path formed between the electrodes. The RS effect can be attributed to the formation and rupture of the conductive path under the positive and negative bias. Our results provide the evidence that the spinel oxides, MFe2O4, have potential applications in resistive switching random access memories.
Keywords: Resistive switching; Reactive cosputtering; Oxygen vacancy; Conductive path;
Shape-controlled synthesis of GaN microrods by ammonolysis route by Keyan Bao; Wenmin Liu; Aihua Wang; Xiaodi Liu; Ruiting Guo; Yapei Wu (682-687).
Display Omitted► GaOOH microrods were prepared by a solvothermal method at 190 °C for 24 h. ► GaOOH were converted into GaN by calcinations in the flow of NH3 gas at 850 °C. ► GaOOH structural motifs were unaffected by the high transformations process. ► The as-prepared wurtzite GaN microrods showed strong blue-violet emission.It would be interesting to synthesize GaN with various morphologies for different applications. Herein, the synthesis of GaN microrods is demonstrated. The synthesis involved two steps: first, hydrothermal synthesis of GaOOH microrods at 190 °C for 24 h; second, preparation of GaN microrods in the flow of NH3 gas at 850 °C for 90 min. The synthesized GaOOH and GaN microrods were characterized by FESEM, suggesting that the initial GaOOH structural motifs were unaffected by the high temperature chemical transformations process. It was found that a slower heating rate (1 °C min−1) is beneficial to keeping the 1D skeleton of and GaN, while GaN nanoparticles with minor microtubes were obtained with a higher heating rate (10 °C min−1). Raman spectroscopy and PL spectrum of the as-prepared GaN product have been performed. The photoluminescence measurement reveals that the as-prepared wurtzite GaN microrods showed strong blue-violet emission.
Keywords: GaN; Microrods; GaOOH; Ammonolysis; Blue-violet emission;
Microporous TiO2-WO3/TiO2 films with visible-light photocatalytic activity synthesized by micro arc oxidation and DC magnetron sputtering by Kee-Rong Wu; Chung-Hsuang Hung; Chung-Wei Yeh; Jiing-Kae Wu (688-695).
► A simple MAO is used to prepare porous WO3/TiO2 layer on Ti sheet as a visible-light enabled catalyst. ► The photocatalytic activity of the WO3/TiO2 is enhanced by sputtering over an N,C-TiO2 layer. ► This is ascribed to the synergetic effect of hybrid sample prepared by two-step method.This study reports the preparation of microporous TiO2-WO3/TiO2 films with a high surface area using a two-step approach. A porous WO3/TiO2 template was synthesized by oxidizing a titanium sheet using a micro arc oxidation (MAO) process. This sheet was subsequently overlaid with a visible light (Vis)-enabled TiO2 (N,C-TiO2) film, which was deposited by codoping nitrogen (N) and carbon (C) ions into a TiO2 lattice using direct current magnetron sputtering. The resulting microporous TiO2-WO3/TiO2 film with a 0.38-μm-thick N,C-TiO2 top-layer exhibited high photocatalytic activity in methylene blue (MB) degradation among samples under ultraviolet (UV) and Vis irradiation. This is attributable to the synergetic effect of two-step preparation method, which provides a highly porous microstructure and the well-crystallized N,C-TiO2 top-layer. This is because a higher surface area with high crystallinity favors the adsorption of more MB molecules and more photocatalytic active areas. Thus, the microporous TiO2-WO3/TiO2 film has promising applications in the photocatalytic degradation of dye solution under UV and Vis irradiation. These results imply that the microporous WO3/TiO2 can be used as a template of hybrid electrode because it enables rapid fabrication.
Keywords: Microporous; Micro arc oxidation; Magnetron sputtering; Photocatalytic activity;
Improvement of Ag(I) adsorption onto chitosan/triethanolamine composite sorbent by an ion-imprinted technology by Liang Zhang; Shuwei Yang; Tong Han; Lvling Zhong; Cailian Ma; Yuanzhen Zhou; Xuanli Han (696-703).
► Triethanolamine was used to improve the adsorption performance of chitosan gel beads in our work. ► The imprinting technique was used to improve the selectivity for Ag+. ► The Ag-ICTHB and Ag-ICTGB have good durability (over 20 cycles).The chitosan/triethanolamine (CTS/TEA) composites including Ag-imprinted CTS/TEA hydrogel bead (Ag-ICTHB) and Ag-imprinted CTS/TEA gel bead (Ag-ICTGB) were prepared by using ion-imprinted technology, in which TEA solution was used as coagulation bath to obtain the two sorbents. The optimization conditions for preparing the sorbents were listed: molar ratio (CTS:Ag(I)) = 1:0.10, c(CTS) = 1.0 for Ag-ICTHB and 2.0% for Ag-ICTGB, c(TEA) = 14%, and c(Na2S2O3) = 8.0 g L−1 as the elueant. The spectrum of FT-IR implies that bonding are formed between TEA and the primary hydroxyl of CTS, and ―NH and ―OH of CTS have some interactions with Ag(I). The DSC curve shows that two form of acting force for the adsorption of Ag(I) were appeared in the adsorption between the sorbents and Ag(I). The maximum adsorption capacities of Ag-ICTHB and Ag-ICTGB for Ag+ are 510 and 350 mg g−1, respectively. Moreover, the two beads exhibit good selectivity and durability for Ag+.
Keywords: Chitosan; Ion-imprinted technology; Silver; Triethanolamine; Adsorption;
Fabrication and photocatalytic activities of ZnO arrays with different nanostructures by Fazhe Sun; Xueliang Qiao; Fatang Tan; Wei Wang; Xiaolin Qiu (704-711).
► We synthesized large-scale ZnO arrays with a series of morphologies including nest-like, tower-like, and flower-like samples by a simple low temperature hydrothermal method. ► The morphologies of the obtained ZnO crystal arrays can be conveniently tailored by changing seeding conditions. ► The possible growth mechanisms of ZnO structures were clearly discussed. ► The nest-like ZnO crystal arrays exhibit higher photocatalytic activity than tower-like and flower-like ZnO crystal arrays.Large-scale ZnO arrays with a series of morphologies, including nest-like, tower-like, and flower-like samples, have been successfully synthesized by a simple hydrothermal method. The morphologies of the obtained ZnO arrays can be conveniently tailored by changing seeding conditions. The samples were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Their PL spectra depend on their morphologies and defects density. The morphology-dependent photocatalytic performances were studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The nest-like ZnO arrays exhibited higher photocatalytic activity than tower-like and flower-like ZnO arrays.
Keywords: Crystal growth; Nanocrystalline materials; Hydrothermal method; Photocatalytic activity;
Palladium nanoparticles on hierarchical carbon surfaces: A new architecture for robust nano-catalysts by Hema Vijwani; Sharmila M. Mukhopadhyay (712-721).
Display Omitted► Palladium nanoparticles have been deposited on porous cellular surfaces of carbon. ► Influence of surface modification on catalyst distribution has been compared. ► Acid etching and oxide coating is seen to increase Pd catalyst loading by up-to 3 times. ► In contrast, when the surface morphology is altered by nanotube attachment, catalyst loading can be increased by over three orders of magnitude. ► Nanotubes and nanoparticles appear to be durable, and remain attached to surface after prolonged rotations in water.Surface activity of heterogeneous catalysts can be enhanced if their sizes are reduced to nanometers. However, loose nanomaterials pose potential health and environmental risks. This issue has been addressed by attachment of palladium nanoparticles on multi-scale hierarchical carbon supports that have exceptionally high surface area per volume. The supports consist of porous carbon foam whose surface has been either chemically functionalized, or morphologically altered by grafting of carbon-nanotubes. It is seen that whereas chemical functionalization does provide some increase in nano-catalyst loading, morphological modification is significantly more powerful. It has the potential to create orders of magnitude increase in catalytic activity within the same overall volume. The synthesis techniques have been investigated in sufficient detail to provide significant control over the density and size of nanoparticles. Abundant distribution of nanoparticles is observed even within the deeper pores of the microcellular foam. The nanoparticles are seen to be metallic Pd having face centered cubic structure. Additionally, the nano-particles and nanotubes are durable, and remain attached to the base support after long periods of rapid rotation in water. These robust hybrid structures show promise in future applications such as sensors, water purification systems, fuel cell electrodes and hydrogen storage sponges.
Keywords: Palladium; Metal nanoparticle; Nano-catalyst; Nanotube; Porous carbon; Surface coating; Hierarchical structures;
Wettability and optical properties of O2 and CF4 plasma treated biaxially oriented semicrystalline poly(ethylene terephthalate) films by D. Jucius; V. Grigaliūnas; V. Kopustinskas; A. Lazauskas; A. Guobienė (722-729).
► PET films were treated by low pressure O2 and CF4 plasma. ► Influence of the plasma treatment on optical properties and wettability was examined. ► Aging effects were analyzed by storing the samples at room conditions for 60 days. ► Highly hydrophilic surfaces were made without worsening of optical transmission.Influence of low pressure O2, CF4, and successive O2 and CF4 RF plasma treatment on optical properties and wettability of biaxially oriented semicrystalline poly(ethylene terephthalate) (PET) was examined. Produced by industrial stretch-blow molding PET films of the 300 μm thickness were chosen for the experiments. Influence of the aging was also investigated by storing plasma treated samples at room conditions for 60 days. It was revealed that O2 plasma treated samples suffered from the hydrophobic recovery and long term improvement of hydrophilicity was only a moderate. Energetic CF4 plasma treatment was able to form a large number of surface active sites which in turn was capable to attach the oxygen containing groups and to increase the hydrophilicity. However, aged for 10–60 days CF4 plasma treated PET films have showed a large scattering of the contact angle values measured on the same surface. Successive O2 and CF4 plasma treatment, despite induced hydrophobicity of as treated films, after 3 days of aging have resulted in highly homogeneous hydrophilic (Θ ≈ 20°) surfaces which have retained their hydrophilicity for the entire period of investigation. Moreover, combined plasma treatment of PET films has not influenced significantly the transmission of visible light. So, such a treatment can be considered as beneficial for the production of highly homogeneous hydrophilic surfaces without significant influence on their optical properties.
Keywords: Polyethylene terephthalate; Plasma treatment; Contact angle; Hydrophilicity; Optical properties; Aging;
Formation of nanostructured NiAl coating on carbon steel by using mechanical alloying by M. Mohammadnezhad; M. Shamanian; M.H. Enayati (730-736).
► Mechanical alloying process could be used for the deposition of nanostructured NiAl intermetallic coatings at ambient atmosphere. ► Thicker coatings could be formed on the substrate and produced maximum value of around 470 μm after treatment of 480 min. ► The hardness of the coating on the substrate was more than seven times that of the initial steel substrate. ► The diffraction patterns before heat treatment, suggests the NiAl intermetallic and another phase and after heat treatment, suggests completely a NiAl intermetallic at 480 min.Nanostructured NiAl intermetallics coatings were generated on carbon steel by using mechanical alloying in ambient temperature and pressure. Ni and Al powders were mixed with the composition of Ni–50 at% Al. The process involved powder particles trapped between the ball and cold welding at surface. Coatings were examined using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the phase transmutation during process and subsequent heat treatment are strongly dependent on mechanical alloying time. After 480 min heat treatment of mechanically alloyed sample, only NiAl peaks were viewed. Ball encounters and failures consecutively reduced the coarse grains of the coating to the nanoscale. The size of nanocrystalline grains in the NiAl coating ranged between 28 and 130 nm. The creation of the coatings was studied at milling intervals between 60 and 600 min. The average thickness and hardness of the surface layers at 480 min, were 470 μm and 930 HV, respectively.
Keywords: NiAl; Coating; Mechanical alloying; Intermetallics; Nanostructured materials;
The effects of processing conditions on the surface morphology and hydrophobicity of polyvinylidene fluoride membranes prepared via vapor-induced phase separation by Yuelian Peng; Hongwei Fan; Ju Ge; Shaobin Wang; Ping Chen; Qi Jiang (737-744).
► Hydrophobic PVDF membranes were prepared via a VIPS method. ► Low air temperature and high PVDF content facilitated the crystallization process. ► High air temperature and low PVDF content were favorable for spinodal decomposition. ► Crystallization and spinodal decomposition led to particle and net-like surface respectively. ► Net-like surface was more favorable for superhydrophobicity than particle surface.The present investigation reveals how the surface morphology and the hydrophobicity of polyvinylidene fluoride (PVDF) membranes, which were prepared via a vapor-induced phase separation method, were affected by the initial PVDF content in the casting solution and the air temperature. The surface morphology was characterized with scanning electron microscopy. A ternary phase diagram of PVDF/N, N-dimethylacetamide/water was constructed to explain the formation mechanism of the different morphologies. The results show that different membrane morphologies and hydrophobicities can be obtained by changing the processing conditions. Low air temperature and high PVDF contents facilitate the crystallization process, resulting in the formation of a porous skin and particle morphology, which increases the hydrophobicity of the surface. High air temperature and low PVDF contents are favorable for the formation of a net-like surface morphology via spinodal decomposition and lead to a superhydrophobic surface. Theoretical calculations were performed to testify that the net-like surface was more favorable for superhydrophobicity than the particle-based surface.
Keywords: Surface morphology; Polyvinylidene fluoride membranes; Vapor-induced phase separation; Superhydrophobic surface;
Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles by Seied Mahdi Pourmortazavi; Mehdi Rahimi-Nasrabadi; Morteza Khalilian-Shalamzari; Mir Mahdi Zahedi; Seiedeh Somayyeh Hajimirsadeghi; Ismail Omrani (745-752).
NiWO4 nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically.Display Omitted► NiWO4 spherical nanoparticles were synthesized via direct precipitation method. ► Taguchi robust design was used for optimization of synthesis reaction parameters. ► Composition and structural properties of NiWO4 nanoparticles were characterized. ► EDAX, XRD, SEM, FT-IR, UV–vis and photoluminescence techniques were employed. ► Catalytic activity of the product in a cyclo-addition reaction was investigated.Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV–vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.
Keywords: Nanoparticle; Nickel tungstate; Structure characterization; Catalytic activity; Precipitation synthesis; Statistical optimization;
Tailoring fly ash activated with bentonite as adsorbent for complex wastewater treatment by Maria Visa (753-762).
Display Omitted► The spent adsorbent annealed at 500 °C can be a suggestion for padding in stone blocks. ► The cations can be adsorbent by the silanol group (Si―OH) of the layers from bentonite ► Copper has a higher affinity for the active sites on adsorbent FAw + B than cadmium. ► This substrate can be recommended for simultaneous removal of heavy metals and MB. ► FAw + B is recommended for wastewater treatment resulted in the dyes finishing industry.Used as adsorbent, alkali fly ash represents a low cost solution for advanced wastewater treatment. The alkali treatment raises sustainability issues therefore, in this research we aim to replace alkali fly ash with washed fly ash (FAw). For improving the adsorption capacity of washed fly ash, bentonite powder (B) was added, as a natural adsorbent with a composition almost identical to the fly ash. The new adsorbent was characterized by AFM, XRD, FTIR, SEM, EDS and the surface energy was evaluated by contact angle measurements. For understanding the complex adsorption process on this mixed substrate, preliminary tests were developed on synthetic wastewaters containing a single pollutant system (heavy metal), binary (two-heavy metals) and ternary (dye and two heavy metals) systems. Experiments were done on synthetic wastewaters containing methylene blue, cadmium and copper, using FAw, B and their powder mixtures. The pseudo-second order kinetics could well model all the processes, indicating a good adsorbent material which can be used for the pollutants removal from wastewater. After adsorption the substrates loaded with pollutants, annealed at 500 °C can be reused for padding in stone blocks.
Keywords: Bentonite; Fly ash; Pollutants; Adsorption; Wastewater treatment;
Surface modification of NiTi by plasma based ion implantation for application in harsh environments by R.M. Oliveira; B.B. Fernandes; F.C. Carreri; J.A.N. Gonçalves; M. Ueda; M.M.N.F. Silva; M.M. Silva; L. Pichon; E.N. Camargo; J. Otubo (763-768).
► New nitrogen PBII set up was used to treat samples of NiTi in moderate temperature of 450 °C. ► A very rich nitrogen atomic concentration was achieved on the top surface. ► Nitrogen diffused at least for 11 μm depth. ► Improved tribological and corrosion properties were achieved. ► A concentration dependent diffusion coefficient was calculated.The substitution of conventional components for NiTi in distinct devices such as actuators, valves, connectors, stents, orthodontic arc-wires, e.g., usually demands some kind of treatment to be performed on the surface of the alloy. A typical case is of biomaterials made of NiTi, in which the main drawback is the Ni out-diffusion, an issue that has been satisfactorily addressed by plasma based ion implantation (PBII). Even though PBII can tailor selective surface properties of diverse materials, usually, only thin modified layers are attained. When NiTi alloys are to be used in the harsh space environment, as is the case of devices designed to remotely release the solar panels and antenna arrays of satellites, e.g., superior mechanical and tribological properties are demanded. For this case the thickness of the modified layer must be larger than the one commonly achieved by conventional PBII. In this paper, new nitrogen PBII set up was used to treat samples of NiTi in moderate temperature of 450 °C, with negative voltage pulses of 7 kV/250 Hz/20 μs, in a process lasting 1 h. A rich nitrogen atomic concentration of 85 at.% was achieved on the near surface and nitrogen diffused at least for 11 μm depth. Tribological properties as well as corrosion resistance were evaluated.
Keywords: Plasma; Ion implantation; Wear; Corrosion; Diffusion; NiTi alloy;
Highly uniform CeO2 hierarchical microstructures: Facile synthesis and catalytic activity evaluation by Lei Wang; Lin-Fei Zhang; Sheng-Liang Zhong; An-Wu Xu (769-776).
► Pancake-like CeO2 hierarchical microstructures have been successfully prepared. ► Gold coated ceria microstructures were also prepared. ► The products show excellent catalytic activity in the conversion of carbon monoxide.Highly uniform pancake-like CeOHCO3 hierarchical microstructures have been successfully prepared by a simple gelatin-assisted mixed-solvothermal route. Ceria hierarchical microstructures with similar morphology were obtained after thermal treatment of the CeOHCO3 hierarchical microstructures at 700 °C for 4 h. The CeOHCO3 microstructures can be selectively obtained by varying the composition of solvent, concentration of gelatin and triethylenetetramine (TETA). The as-prepared products were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electronic microscope (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and selected area electron diffraction (SAED). The possible formation process of the CeOHCO3 microstructures was briefly discussed. Gold coated ceria microstructures were also prepared which show excellent catalytic activity in the conversion of carbon monoxide, the T 50 and T 90 are at 240 °C and 300 °C, respectively.
Keywords: Ceria; Mixed-solvothermal; Superstructure; CO oxidization;
Improvement of surface properties of SLM parts by atmospheric plasma spraying coating by Baicheng Zhang; Lin Zhu; Hanlin Liao; Christian Coddet (777-782).
► A dense Al2O3 coating was prepared on the SLM part by APS technology. ► The surface qualities and microhardness of SLM parts are strongly improved by APS Al2O3 coating. ► The adhesive strength of the Al2O3 coating deposited by APS on SLM parts is relatively high. ► The characteristic of original SLM surface can reinforce the adhesions of Al2O3 coating.Although selective laser melting (SLM) provides many advantages compared to conventional forming methods, limited surface quality is one of the major drawbacks restricting its application. As a remedy, the ceramic coating was deposited on the SLM parts surface in order to improve surface quality in this study. Furthermore, the combination of SLM and APS makes a great possibility to obtain special function material for special application. In this work, the bonding condition between ceramic coating and stainless steel parts were observed by optical microscope and SEM. The surface morphology and roughness were measured by a 3D-profilemeter. The microhardness and bonding strength of the ceramic coating were also measured. This paper presents two types of bonding mechanisms between ceramic coating and SLM parts with horizontal/vertical surface. It can be found that the bonding strength of the coating on the vertical surface was approximately 40 MPa, but the bonding strength of coating on the horizontal surface is relatively weaker.
Keywords: Selective laser melting; Atmospheric plasma spraying; Surface quality; Composite material;
Superhydrophobic chitosan-based coatings for textile processing by N.A. Ivanova; A.B. Philipchenko (783-787).
► Chitosan nanoparticles can be used for design of the superhydrophobic anti-bacterial textile. ► Spraying the nanoparticle dispersion allows one to get multiscale textured coating. ► Relative number of fluoroanions per elementary unit of chitosan plays the crucial role in the structure of aggregates and coating wettability.A simple method to design the superhydrophobic anti-bacterial textile for biomedical applications was developed. For the coating formulation the spraying of nanoparticles dispersion over the textile sample was applied, allowing the way to get multiscale textured layer on a top of cotton fabric. The anti-bacterial functionality of coating is supported by using chitosan-based nanoparticles. In our approach the fabrication of nanoparticles was based on electrostatic interaction between amine group of chitosan and negatively charged fluoroanion. It was demonstrated that the relative number of fluoroanions per elementary unit of chitosan plays the crucial role in the structure of aggregates in the coating and its wettability as well as in durability of coatings in contact with aqueous media.
Keywords: Waterproof textile; Superhydrophobicity; Wetting;
Novel BN/Pd composite films for stable liquid petroleum gas sensor by D. Ghosh; B. Ghosh; S. Hussain; Subhajyoti Chaudhuri; R. Bhar; A.K. Pal (788-794).
► Composite films of BN/Pd were synthesized. ► Reproducible liquid petroleum gas (LPG) sensing properties. ► Lower operating temperature ∼463 K. ► High thermal stability would make this material superior to prevalent oxide based sensors.Composite films of BN/Pd were synthesized by depositing thin films of BN by pulsed laser deposition technique and evaporating a thin layer of palladium on top of it to form a bi-layer structure. This bi-layer structure was then subjected to rapid thermal annealing for the incorporation of Pd in BN. The films thus obtained were characterized by SEM, XRD and FTIR studies. Liquid petroleum gas (LPG) sensing properties were also investigated critically. Very stable and reproducible LPG sensing properties and comparatively at lower operating temperature of 460 K would make this material superior to prevalent oxide based sensors.
Keywords: h-BN; Sensor; PLD;
Magnetically recoverable Ni@carbon nanocomposites: Solid-state synthesis and the application as excellent adsorbents for heavy metal ions by Zheng Hui Xiao; Rui Zhang; Xiang Ying Chen; Xue Liang Li; Tao Fa Zhou (795-803).
► The use of solid-state method for Ni@Cs is effective and simple. ► Ni@Cs has higher adsorption capacity and chemical stability. ► Ni@Cs can be separated and reused by an external magnetic field.Various magnetic nanocomposites with carbon-coated nickel structure (Ni@Cs) for selective adsorption of Pb2+ and Cu2+ have been prepared by a simple solid-state method, in which citric acid and nickel nitrate were selected as carbon resource and magnetic substance, respectively. Ni@C-1:5/1:10/1:20 were obtained with various mass ratios (nickel nitrate/citric acid) under the experimental conditions. FESEM and TEM results reveal that the nanocomposite particles exhibit relatively homogeneous distribution in shape/size, possessing mostly carbon-coated structure. Based on the analysis of N2 adsorption–desorption isotherm, the surface areas and pore volumes of the nanocomposites (Ni@C-1:5/1:10/1:20) are (183, 220, 149) m2 g−1 and (0.29, 0.22, 0.08) cm3 g−1, respectively. The saturation magnetization values for the Ni@Cs are as high as (11.82, 5.20 and 3.84) emu g−1 obtained by the VSM. Following, the application of the Ni@Cs for the removal of heavy metal ions (Pb2+ and Cu2+) from wastewater as potential and effective adsorbents was investigated. The results reveal the adsorbents possess more accessible active sites and good dispersibility in water, exhibiting excellent performance for selectivity of Pb2+ than that of Cu2+. The results of adsorption behavior are followed the pseudo-second-order kinetics and Freundlich model between the adsorbents and the heavy metal ions. Furthermore, the adsorbents can be recovered easily with an external magnetic field, having a higher remove efficiency after several times.
Keywords: Solid-state; Ni@carbon nanocomposite; Separable; Heavy metal ions; Adsorption;
Laser surface modification treatment of aluminum bronze with B4C by B.S. Yilbas; A. Matthews; A. Leyland; C. Karatas; S.S. Akhtar; B.J. Abdul Aleem (804-809).
► Fine grains and dense layer were formed in the surface vicinity; in which Cu3N compound was present. ► Due to volume shrinkage of the dense layer, a few locally scattered voids were formed below the surface. ► Formation of Cu3N compound in the surface region enhanced microhardness at the surface. ► In-plane residual stress was compressive at surface and it was on the order of −400 MPa. ► Self-annealing effect of lately formed laser scanning tracks reduced residual stress at the surface.One technique to improve tribological properties of aluminum bronze surfaces is to introduce laser controlled melting at the surface in the presence of a composition-modifying film. In this work, a 40 μm thick organic film, containing B4C particles, was formed at the workpiece surface prior to laser treatment. The organic coating provides enhanced absorption of the incident laser radiation and distributes the B4C particles uniformly across the surface. Morphological and microstructural changes in the laser treated layer were examined using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The microhardness of the laser treated layer was measured and the residual stress formed at the treated surface was evaluated by X-ray diffraction using the sin2 ψ technique. It was found that the laser treated surface produced is relatively free from defects and asperities with a microhardness that is notably higher than that of the as-received bronze substrate. This hardening effect can be attributed to the development of a dense layer consisting of fine grains, partially dissolved B4C particles, and formation of Cu3N compounds. The residual compressive stress obtained from X-ray diffraction peak evaluation is of the order of −400 MPa.
Keywords: Laser; Bronze; B4C; Hardness; Residual stress;
Improving oxidation resistance and thermal insulation of thermal barrier coatings by intense pulsed electron beam irradiation by Xianxiu Mei; Xiaofei Liu; Cunxia Wang; Younian Wang; Chuang Dong (810-815).
► Pulsed electron beam was used for sealing ZrO2 thermal barrier coating prepared by electron beam-physical vapor deposition. ► At irradiation energy densities above 8 J/cm2, ZrO2 ceramic coating surface was fully re-melted and became smooth, dense and shiny. ► The thermal diffusion rate of the irradiated coating was decreased. ► Thermal insulation properties and high temperature oxidation resistance were improved.In this paper, intense pulsed electron beam was used for the irradiation treatment of 6–8% Y2O3-stablized ZrO2 thermal barrier coating prepared by electron beam-physical vapor deposition to achieve the “sealing” of columnar crystals, thus improving their thermal insulation properties and high temperature oxidation resistance. The electron beam parameters used were: pulse duration 200 μs, electron voltage 15 kV, energy density 3, 5, 8, 15, 20 J/cm2, and pulsed numbers 30. 1050 °C cyclic oxidation and static oxidation experiments were used for the research on oxidation resistance of the coatings. When the energy density of the electron beam was larger than 8 J/cm2, ZrO2 ceramic coating surface was fully re-melted and became smooth, dense and shiny. The coating changed into a smooth polycrystalline structure, thus achieving the “sealing” effect of the columnar crystals. After irradiations with the energy density of 8–15 J/cm2, the thermally grown oxide coating thickness decreased significantly in comparison with non-irradiated coatings, showing that the re-melted coating improved the oxidation resistance of the coatings. The results of thermal diffusivity test by laser flash method showed that the thermal diffusion rate of the irradiated coating was lower than that of the coating without irradiation treatment, and the thermal insulation performance of irradiated coating was improved.
Keywords: Yttria-stabilized zirconia thermal barrier coatings; Intense pulsed electron beam irradiation; Oxidation resistance and thermal insulation properties;
Synthesis of hollow spherical TiO2 for dye-sensitized solar cells with enhanced performance by X.P. Lin; D.M. Song; X.Q. Gu; Y.L. Zhao; Y.H. Qiang (816-820).
► Dye-sensitized solar cell (DSSC) assembled using TiO2 double-layered films as photoanodes. ► TiO2 hollow spheres synthesized using colloidal carbon spheres as template are applied to DSSC. ► Influence of light-scattering effect of TiO2 hollow spheres on the DSSC performance is investigated. ► High efficiency of 5.6% achieved in the DSSC through using TiO2 hollow spheres as light-scattering layer.TiO2 hollow spheres (HSs) have been synthesized using colloidal carbon spheres as templates. The photoelectric conversion performances of dye-sensitized solar cells (DSSCs) based on TiO2 nanoparticles (NPs)/NPs, NPs/TiO2 HSs double-layered films were investigated. Owing to the hollow structure, the DSSC using TiO2 HSs as light-scattering layer exhibits an enhanced light harvesting efficiency, therefore leading to a 48% increment of cell efficiency compared to that pure TiO2 NP films.
Keywords: Dye-sensitized solar cells; TiO2 hollow spheres; Light-scattering; Colloidal carbon spheres;
Super-hydrophilicity to super-hydrophobicity transition of a surface with Ni micro–nano cones array by Wenyan Geng; Anmin Hu; Ming Li (821-824).
A surface with Ni micro–nano cones array (MCA) was fabricated with electro-deposition method and exhibited super-hydrophilic nature when freshly prepared. Spontaneous transition from super-hydrophilicity to super-hydrophobicity was observed when the surface was exposed in air at room temperature. The special surface structure of MCA played an important role in amplifying the surface wettability. Since the surface structure remained the same as the freshly prepared Ni MCA films during the storage, the transition was proved to be attributed to the change of surface chemical composition. Such wettability transition property of Ni MCA films might shed light on the high-tech areas of self-cleaners, anti-corrosion materials, anti-contamination materials, etc.
Keywords: Surfaces; Electrodeposition; Micro–nano cones array; Wettability transition; Super-hydrophilicity; Super-hydrophobicity;
Erratum to “Direct monophasic replacement of fatty acid by DMSA on SPION surface” [Appl. Surf. Sci. 258 (2012) 9685] by M. Gogoi; P. Deb; G. Vasan; P. Keil; A. Kostka; A. Erbe (825-826).
RETRACTED: Chemical densification of plasma sprayed yttria stabilized zirconia (YSZ) coatings for high temperature wear and corrosion resistance by Yaping Ye; Karl Thomas Fehr; Martin Faulstich; Gerhard Wolf (827).
This article has been retracted at the request of the Editor-in-Chief and Author.The authors have requested retraction because an incomplete manuscript was submitted without the approval of all authors.