Applied Surface Science (v.257, #21)
Optical and hydrophobic properties of co-sputtered chromium and titanium oxynitride films by Sushant K. Rawal; Amit Kumar Chawla; R. Jayaganthan; Ramesh Chandra (8755-8761).
► Ti-doped chromium oxynitride and Cr-doped titanium oxynitride films at Cr and Ti targets powers. ► Such co-sputtering studies using helium as inert gas is rare in literature. ► This article deals with a systematic study on structural, optical and hydrophobic properties of films. ► The chromium oxynitride films changes from hydrophilic to hydrophobic. ► The surface energy is sensitive to the contact angle and optical properties like n, E g, %T are tailored.The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF magnetron sputtering in the present work. The structural and optical properties of the chromium and titanium oxynitride films as a function of power variations are investigated. The chromium oxynitride films are crystalline even at low power of Cr target (≥60 W) but the titanium oxynitride films are amorphous at low target power of Ti target (≤90 W) as observed from glancing incidence X-ray diffraction (GIXRD) patterns. The residual stress and strain of the chromium oxynitride films are calculated by sin2 ψ method, as the average crystallite size decreases with the increase in sputtering power of the Cr target, higher stress and strain values are observed. The chromium oxynitride films changes from hydrophilic to hydrophobic with the increase of contact angle value from 86.4° to 94.1°, but the deposited titanium oxynitride films are hydrophilic as observed from contact angle measurements. The changes in surface energy were calculated using contact angle measurements to substantiate the hydrophobic properties of the films. UV–vis and NIR spectrophotometer were used to obtain the transmission and absorption spectra, and the later was used for determining band gap values of the films, respectively. The refractive index of chromium and titanium oxynitride films increases with film packing density due to formation of crystalline chromium and titanium oxynitride films with the gradual rise in deposition rate as a result of increase in target powers.
Keywords: Chromium oxynitride; Titanium oxynitride; Co-sputtering; Stress; Strain; Contact angle; Optical properties;
Photoluminescence and magnetic properties of Fe-doped ZnS nano-particles synthesized by chemical co-precipitation by Nie Eryong; Liu Donglai; Zhang Yunsen; Bai Xue; Yi Liang; Jin Yong; Jiao Zhifeng; Sun Xiaosong (8762-8766).
► Zn1−x Fe x S nano-particles are synthesized by chemical co-deposition procedure. ► The Zn1−x Fe x S nano-particles are of single cubic zinc blende phase. ► The size of Zn1−x Fe x S nano-particles is about 3.3–5.5 nm. ► PL emissions of 425 nm and 470 nm have been found. ► Zn1−x Fe x S (x = 0.1) nano-particles present superparamagnetic performance.This paper is focusing on the synthesis of Zn1−x Fe x S nano-particles with x = 0, 0.1 and 0.2 by chemical co-precipitation method, the prepared of which are characterized by XRD, EDS, TEM, PL, magnetization versus field behavior and M–T curve. In the XRD patterns, Zn1−x Fe x S nano-particles are shown of cubic zinc blende structure, and the broadening diffraction peaks consistent with the small-size characteristic of nano-materials. The diameter of nano-particles is between 3.3 and 5.5 nm according to the HR-TEM images. The EDS data confirm the existence of Fe ions in Fe-doped ZnS nanoparticles. There we found that Fe-doping did not import new energy bands or defect states, but reduced the intensity of PL peaks. The magnetization versus field behaviors were illustrated by the M–H curves at both 5 K and 300 K, respectively, where no remanence or coercive force was observed. This phenomenon indicates that the Zn1−x Fe x S (x = 0.1) nano-particles are superparamagnetic. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves further reveal that the blocking temperature (T B) of the superparamagnetic behavior might be below 5 K.
Keywords: TM-doped II-VI semiconductors; DMS; Superparamagnetic behavior;
First principles study of Si etching by CHF3 plasma source by Weichao Wang; Pil-Ryung Cha; Sang ho Lee; Gyoodong Kim; Moon J. Kim; Kyeongjae Cho (8767-8771).
A model of CF3 etching Si (2 × 4) surface has been developed based on density functional theory. We find that the reconstruction Si surface tends to be fully F-terminated. Meanwhile, C–C chain forms spontaneously on the top of the surface to resist further F–Si interacting. Over-saturated Si bonds could still be stable as well due to the strong F–Si bonding, however, it needs to overcome an energy barrier of 1.85 eV to achieve this doubly saturated bonding. Two reaction paths are found to investigate chemical reaction of CF3 with the full F-terminated Si surface. The first path displays that all fully saturated F–Si bonds could be over-saturated and thus produce F–Si–F bonds with an energy barrier of ∼1.85 eV. For this path, there is no product of SiF4; the second path indicates a formation of SiF4 with a much lower surface energy than the first path. The formation of SiF4 shows the possible etching mechanism.
Keywords: Etching rate; Si surface etching; Density functional theory; Nudge-elastic-band (NEB);
In vitro degradation of AZ31 magnesium alloy coated with nano TiO2 film by sol–gel method by Junhua Hu; Caili Zhang; Baohong Cui; Kuifeng Bai; Shaokang Guan; Liguo Wang; Shijie Zhu (8772-8777).
► Nano-TiO2 films were fabricated on AZ31 alloys as protective layers by sol–gel method. ► The inhibition effects were evaluated. ► The formation of defect structures on the films was analyzed and related with the degradation of coated alloys.A nano TiO2 film was coated on AZ31 alloy substrate by sol–gel method. The TiO2 film was characterized by X-ray diffractometry (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TG), field emission scanning electron microscopy (FE-SEM) and energy dispersion spectroscopy (EDS). The degradation of the nano-TiO2 coated alloy was evaluated by immersion test and electrochemical measurement. An attempt was made to relate corrosion of coated alloys with the annealing treatment and resultant structural evolution.
Keywords: In vitro degradation; Sol–gel; Nano TiO2; Mg alloy;
Synthesis and characterization of TiO2/Fe2O3 core–shell nanocomposition film and their photoelectrochemical property by Hui Zhao; Wuyou Fu; Haibin Yang; Yang Xu; Wenyan Zhao; Yanyan Zhang; Hui Chen; Qiang Jing; Xuefeng Qi; Jing Cao; Xiaoming Zhou; Yixing Li (8778-8783).
► TiO2/Fe2O3 core–shell nanocomposition film has been fabricated via two-steps method. Such 1D nanostructured materials with better property have been uncommonly previously. ► UV–vis absorption property is induces the shift of the absorption edge into the visible-light range. ► The TiO2 NRs modified by Fe2O3 show higher photocurrent value than those of unmodified TiO2 NRs and other conditions.TiO2/Fe2O3 core–shell nanocomposition film has been fabricated via two-step method. TiO2 nanorod arrays are synthesized by a facile hydrothermal method, and followed by Fe2O3 nanoparticles deposited on TiO2 nanorod arrays through an ordinary chemical bath deposition. The phase structures, morphologies, particle size, chemical compositions of the composites have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and ultraviolet–visible (UV–vis) spectrophotometer. The results confirm that Fe2O3 nanoparticles of mean size ca. 10 nm coated on the surface of TiO2 NRs. After depositing Fe2O3, UV–vis absorption property is induces the shift to the visible-light range, the annealing temperature of 600 °C is the best condition for UV–vis absorption property of TiO2/Fe2O3 nanocomposite film, and increasing Fe content, optical activity are enhanced one by one. The photoelectrochemical (PEC) performances of the as-prepared composite nanorods are determined by measuring the photo-generated currents under illumination of UV–vis light. The TiO2 NRs modified by Fe2O3 show the photocurrent value of 1.36 mA/cm2 at 0 V vs Ag/AgCl, which is higher than those of unmodified TiO2 NRs.
Keywords: TiO2 nanorod array; Fe2O3; Nanocomposition film; Photoelectrochemical property;
Improving the photoluminescence properties of self-assembled InAs surface quantum dots by incorporation of antimony by C.H. Chiang; Y.H. Wu; M.C. Hsieh; C.H. Yang; J.F. Wang; Ross C.C. Chen; L. Chang; J.F. Chen (8784-8787).
► This study investigates the surfactant effect and segregation effect from InAs surface quantum dots (SQDs) by incorporating antimony (Sb) into the QD layers. ► The Sb surfactant effect can extend planar growth and suppress dot formation. ► Photoluminescence reveals an enhancement in the optical properties of InAs SQDs as the Sb BEPs increase. ► Transmission electron microscopy images demonstrate that Sb segregates close to the surface of the SQD.This study investigates the effects of surfactant and segregation from InAs surface quantum dots (SQDs) by incorporating antimony (Sb) into the QD layers. The Sb surfactant effect extends planar growth and suppresses dot formation. Incorporating Sb can reduce the density of SQDs by more than two orders of magnitude. Photoluminescence (PL) reveals enhancement in the optical properties of InAs SQDs as the Sb beam equivalent pressure (BEP) increases. This improvement is caused by the segregation of Sb on the surface of SQDs, which reduces non-radiative recombination and suppresses carrier loss. The dark line at the SQDs surface in the transmission electron microscopic image suggests that the incorporated Sb probably segregates close to the surface of the SQDs. These results indicate a marked Sb segregation effect that can be exploited to improve the surface-sensitive properties of SQDs for biological sensing.
Keywords: InAs; Surface quantum dot; Antimony; Surfactant; Segregation;
Enhancement of the ultraviolet emission of ZnO nanorods by terphenyl liquid-crystalline ligands modification by Wei Chen; Fan Li; Yiwang Chen; Kai Yuan; Lie Chen (8788-8793).
► A simple method is developed to greatly enhance the ZnO NRs band-edge emission and effectively suppress deep-band emission by surface modified with liquid crystal ligands. ► The dispersion and band-edge emission can be further improved by annealing treatment at liquid crystalline state temperature of HTph-OH.We have developed a novel method to modifying the surface of ZnO nanorods (ZnO NRs) using p-hexoxyterphenylol (HTph-OH) as liquid crystal ligands. The structure and morphology of the modified ZnO NRs were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and atomic force microscopy (AFM). AFM measurement showed that the dispersion of ZnO NRs could be dramatically improved by the surface modification of HTph-OH and further annealing treatment at its liquid crystal state temperature (150 °C). The remarkable decrease of the annealed composite film roughness is because the HTph-OH chains self-organize into more ordered structure induced by mesogens after annealing treatment, which may push the ZnO NRs to form oriented nano-dispersing structure. The optical properties of the modified ZnO NRs were investigated by UV–vis absorption spectroscopy and photoluminescence spectroscopy (PL). Markedly enhanced band-edge ultraviolet photoluminescence and significantly reduced defect-related emission were observed. We attribute this observation to the nearly perfect surface passivation of the ZnO NRs by the HTph-OH molecules. Meanwhile, UV emission of modified ZnO NRs could be further enhanced by increasing the concentration of HTph-OH and annealing treatment at its liquid crystal state temperature.
Keywords: ZnO nanorods; Photoluminescence; Liquid crystals;
Resistless patterning of a chlorine monolayer on a Si(0 0 1) surface with an electron beam by C. Jeon; H.-N. Hwang; H.-J. Shin; C.-Y. Park; C.-C. Hwang (8794-8797).
We achieved electron beam (e-beam) patterning without a photoresist on a Cl-terminated Si(0 0 1) surface. The Cl–Si bonds were easily broken by the irradiation with an e-beam of 1 keV. We demonstrated the selective adsorption of desired molecules on the surface by e-beam irradiation in environments consisting of different gases, such as oxygen, ammonia, and 1-butanethiol.We achieved electron beam (e-beam) patterning without a photoresist on a Cl-terminated Si(0 0 1) surface. Synchrotron radiation photoemission spectroscopy and scanning photoelectron microscopy were employed to investigate the surface chemical state and pattern formation. The Cl–Si bonds were easily broken by the irradiation with an e-beam of 1 keV, leading to a pattern formation through the adsorption of residual molecules of water and hydrocarbon at the exposed Si dangling bond sites. In addition, we demonstrated the selective adsorption of desired molecules on the surface by e-beam irradiation in environments consisting of different gases, such as oxygen, ammonia, and 1-butanethiol.
Keywords: Synchrotron radiation photoelectron spectroscopy; Electron stimulated desorption; Silicon; Chlorine;
Wettability and osteoblast cell response modulation through UV laser processing of nylon 6,6 by D.G. Waugh; J. Lawrence (8798-8812).
► Surface modifications brought about variations in surface oxygen and topography. ► Laser-modified surface properties modulated wettability. ► Wettability differed between samples indicating a mixed-state wetting regime. ► The bioactivities of the samples were modulated with evidence of differentiation. ► Correlations have been identified between surface properties and cell response.With an ageing population the demand for cheap, efficient implants is ever increasing. Laser surface treatment offers a unique means of varying biomimetic properties to determine generic parameters to predict cell responses. This paper details how a KrF excimer laser can be employed for both laser-induced patterning and whole area irradiative processing to modulate the wettability characteristics and osteoblast cell response following 24 h and 4 day incubation. Through white light interferometry (WLI) it was found that the surface roughness had considerably increased by up to 1.5 μm for the laser-induced patterned samples and remained somewhat constant at around 0.1 μm for the whole area irradiative processed samples. A sessile drop device determined that the wettability characteristics differed between the surface treatments. For the patterned samples the contact angle, θ, increased by up to 25° which can be attributed to a mixed-state wetting regime. For the whole area irradiative processed samples θ decreased owed to an increase in polar component, γ P. For all samples θ was a decreasing function of the surface energy. The laser whole area irradiative processed samples gave rise to a distinct correlative trend between the cell response, θ and γ P. However, no strong relationship was determined for the laser-induced patterned samples due to the mixed-state wetting regime. As a result, owed to the relationships and evidence of cell differentiation one can deduce that laser whole area irradiative processing is an attractive technology for employment within regenerative medicine to meet the demands of an ageing population.
Keywords: Excimer laser; Nylon 6,6; Wettability; Osteoblast cells; Bioactivity; Regenerative medicine;
The effect of laser patterning parameters on fluorine-doped tin oxide films deposited on glass substrates by Shih-Feng Tseng; Wen-Tse Hsiao; Kuo-Cheng Huang; Donyau Chiang (8813-8819).
► We fabricate FTO film electrodes by a UV laser processing system. ► The patterned structures provide the electrical isolation for various touch screens. ► Increasing overlapping rate of laser spot can obtain an excellent machined quality. ► All sheet resistance near the isolated line edge are larger than the original ones. ► The sheet resistance increases with increasing laser spot overlapping area.The purpose of this study is to pattern the fluorine-doped tin oxide thin film deposited on the soda-lime glass substrates for touch screen applications by ultraviolet laser. The patterned film structures provide the electrical isolation and prevent the electrical contact from each region for various touch screens. The surface morphology, edge quality, three-dimensional topography, and profile of isolated lines and electrode structures after laser patterning were measured by a confocal laser scanning microscope. Moreover, a four-point probe instrument was used to measure the sheet resistance before and after laser patterning on film surfaces and also to discuss the electrical property at different laser spot overlaps. After laser patterning, a high overlapping area of laser spot was used to pattern the electrode layer on film surfaces that could obtain an excellent machined quality of edge profile. All sheet resistance values of film surfaces near the isolated line edge were larger than the original ones. Moreover, the sheet resistance values increased with increasing laser spot overlapping area.
Keywords: Fluorine-doped tin oxide; Ultraviolet laser; Electrode structure; Laser spot overlaps; Sheet resistance;
Nanoembossing and piezoelectricity of ferroelectric Pb(Zr0.3,Ti0.7)O3 nanowire arrays by Z.K. Shen; Z.H. Chen; H. Li; X.P. Qu; Y. Chen; R. Liu (8820-8823).
► Ferroelectric nanowires have been fabricated by nanoembossing process. ► Multidomain state in a single nanowire was investigated. ► Piezoelectric hysteresis and polarization switching of a single nanowire was manifested.Arrays of ferroelectric PZT nanowires with lateral size down to 200 nm were fabricated by nanoembossing technology. Structural characterization of the embossed PZT film was studied by Raman spectroscopy. Multidomain configurations of a single nanowire have been explored by vertical mode piezoresponse force microscopy (VPFM). The local electric polarization of the individual ferroelectric nanowire has also been investigated. Excellent ferroelectric and piezoelectric characteristics observed in the embossed PZT nanowires suggest nanoembossing technique proposed in this work is promising to become a useful method for ferroelectric nanowires fabrication.
Keywords: Nanoembossing; Ferroelectric PZT nanowire; Piezoelectric; Domain;
The study of optimal oxidation time and different temperatures for high quality VO2 thin film based on the sputtering oxidation coupling method by Xiaofeng Xu; Xinfeng He; Gang Wang; Xiaolong Yuan; Xingxing Liu; Haiyan Huang; Sheng Yao; Huaizhong Xing; Xiaoshuang Chen; Junhao Chu (8824-8827).
► The VO2 thin film was deposited by a novel sputtering oxidation coupling method. ► The relationship between oxidation time and temperature 1/T is in agreement with Wagner's model. ► The oxidation time as a function temperature 1/T presents a linear relationship among 703 K–783 K.The high quality Vanadium dioxide (VO2) thin films have been fabricated successfully on sapphire by a simple novel sputtering oxidation coupling (SOC) method. All VO2 thin film samples exhibit a good metal–insulator transition (MIT) at about 340 K. The optimal oxidation time at different temperatures has been experimentally investigated. We report on the relationship between optimal oxidation time and different temperatures of metal vanadium thin film samples of 101 nm thickness by oxidation in air. It is found that the optimal oxidation time ln(t) as a function of temperature 1/T shows a significant linear relationship among 703 K–783 K, in good agreement with the Wagner's high-temperature oxidation model.
Keywords: Vanadium dioxide; Sputtering oxidation coupling; Optimal oxidation time; Temperature;
Amphiphobicity of polyvinylidene fluoride porous films after atmospheric pressure plasma intermittent etching by Xuyan Liu; Ho-Suk Choi; Bo-Ryoung Park; Hyung-Keun Lee (8828-8835).
. SEM results indicated that a small amount of hydrophilic solid spines and lots of superamphiphobic uniform micro air pockets occurred in the plasma-modified PVDF films.Display Omitted► An intermittent Ar plasma treatment of PVDF films under atmospheric pressure. ► The optimum treatment conditions of 10 min, 200 W, 10 LPM, and 10 mm/s. ► The plasma-modified PVDF porous film shows amphiphobicity. ► A small amount of hydrophilic solid spines and many superamphiphobic uniform micro air pockets.This study modified the surface of polyvinylidene fluoride (PVDF) films and characterized their surface physicochemical properties. The main aim of this study was to examine how to provide the surface with a specific property, e.g., not only hydrophobic but also oleophobic (amphiphobicity) after argon atmospheric pressure plasma (APP) treatment. The surface free energy calculated using the Owens–Wendt (OW) method decreased significantly while showing a very small value of the polar component. Scanning electron microscopy indicated that a small amount of hydrophilic solid spines and many superamphiphobic uniform micro air pockets formed in the plasma-modified PVDF film, which made it amphiphobic but not superamphiphobic.
Keywords: Amphiphobic surface; Cassie theory; Morphology; XPS; Owens–Wendt method; Contact angle;
A potential green-emitting phosphor Ca8Mg(SiO4)4Cl2:Eu2+ for white light emitting diodes prepared by sol–gel method by Chongfeng Guo; Ming Li; Yan Xu; Ting Li; Zhaoyu Ren; Jintao Bai (8836-8839).
► An intense green emission phosphor Ca8Mg(SiO4)4Cl2:Eu2+ used for near-UV or blue light excited white LEDs is prepared by modified sol–gel method. ► Factors affect the PL intensity of phosphor are investigated, including the dosage of CaCl2, concentration of Eu2+ and heating temperature. ► The PL intensity of phosphor prepared by sol–gel method is stronger than that of phosphor prepared by solid state reaction.A potential green emitting phosphor Ca8Mg(SiO4)4Cl2:Eu2+ was prepared by modified sol–gel method. The factors those affect the photoluminescence intensity including heating temperature, the usage of the chlorine source CaCl2 and the concentration of dopant Eu2+ were also investigated in detail. As comparison, the phosphor prepared by solid-state reaction was also prepared. The phosphors show intense absorption in the range of 375–450 nm, which makes it a potential candidate of green emitting phosphor used for near-UV or blue light excited white LEDs.
Keywords: Phosphor; LEDs; Green emission;
Morphology-control of VO2 (B) nanostructures in hydrothermal synthesis and their field emission properties by Haihong Yin; Ke Yu; Zhengli Zhang; Ziqiang Zhu (8840-8845).
► VO2 (B) nanorods, nanocarambolas and nanobundles were synthesized. ► A continuous changing process of morphology was found. ► Field emission measurement of them was performed, showing good field properties.VO2 (B) nanostructures were synthesized via a facile hydrothermal process using V2O5 as source material and oxalic acid as reductant. Three nanostructures of nanorods, nanocarambolas and nanobundles were found existing in the products, and a continuous changing of morphology was found in the synthesis process, during which the proportion of these three types of nanostructures can be adjusted by altering the concentrations of oxalic acid. The microstructures were evaluated using X-ray diffraction and scanning and transmission electron microscopies, respectively. FE properties measurement of these three types of nanostructures showed that the nanobundles have the best field emission performance with a turn-on field of ∼1.4 V/μm and a threshold field of ∼5.38 V/μm. These characteristics make VO2 (B) nanostructures a competitive cathode material in field emission devices.
Keywords: VO2 (B) nanostructures; Hydrothermal synthesis; Field emission;
The testing of stress-sensitivity in heteroepitaxy GaN/Si by Raman spectroscopy by Jianjun Tang; Ting Liang; Weili Shi; Qianqian Zhang; Yong Wang; Jun Liu; Jijun Xiong (8846-8849).
► We fabricate the crack-free H-GaN epifilms which have been grown on Si (1 1 1) substrates by metal-organic chemical vapor deposition(MOCVD). ► We test the stress-sensitivity of H-GaN up to 93.5 MPa/μm which higher than C-Si which testing is 467.9 MPa/μm. ► Calculate the nonlinear error of stress-sensitivity where GaN films is 0.1639 and Si is 0.0698. ► Research the reason why the E2 (high) Raman peak of H-GaN has a blue shift under increasing displacement-loadings in the C-plane from the configurations of phonon modes in GaN.In this paper the stress-sensitive features of hexagonal-GaN (H-GaN) and cubic-Si (C-Si) were investigeted. The H-GaN films have been grown on Si (1 1 1) substrates by metal-organic chemical vapor deposition (MOCVD). The Raman peaks of GaN E2 (high) and Si (TO) have a blueshift when applying displacement-loadings which parallel the (0 0 0 2) plane of H-GaN. According to the relationship between stress changing and Raman peak shifts, the values of compressive stress in both materials were larger with increasing the displacement-loadings. The stress-sensitivity of H-GaN up to 93.5 MPa/μm which higher than C-Si which testing is 467.9 MPa/μm and the nonlinear error σ of GaN films is 0.1639 and Si is 0.0698. The measurement has a great significance to deeply research the piezoelectric polarization of H-GaN in future. This finding is important for the understanding and application of nitride semiconductors.
Keywords: Raman spectrum; H-GaN; Stress-sensitivity;
The potential use of nanosilver-decorated titanium dioxide nanofibers for toxin decomposition with antimicrobial and self-cleaning properties by Chutima Srisitthiratkul; Voraluck Pongsorrarith; Narupol Intasanta (8850-8856).
TiO2 nanofibers were prepared through sol–gel reaction and electrospinning process. The potential use of these nanofibers as air nanofilters was shown. To further enhance their anti-microbial activity, silver nanoparticles were decorated onto the nanofibers’ surfaces by photoreduction. The nanofibrous membranes prepared from these nanofibers showed superhydrophilicity under UV. The possibility of using these hybrid nanofibers in environmental and hygienic nanofiltration was proposed, where the self-cleaning characteristics was expected to be valuable in maintenance processes.Display Omitted► Nanosilver-decorated TiO2 nanofibers were synthesized. ► Nanofibers were capable of decomposing NOx and VOC. ► Nanofibers showed antimicrobial activity towards Gram positive and negative bacteria. ► Nanofibers showed superhydrophilicity or self-cleaning properties under UV.While chemical and biological attacks pose risk to human health, clean air is of scientific, environmental and physiological concerns. In the present contribution, the potential use of nanosilver-decorated titanium dioxide (TiO2) nanofibers for toxin decomposition with antimicrobial activity and self-cleaning properties was investigated. Titanium dioxide nanofibers were prepared through sol–gel reaction followed by an electrospinning process. Following the Japan Industrial Standard (JIS) protocol, decompositions of nitrogen oxide (NOx) and volatile organic compound (VOC) by the TiO2 nanofibers suggested that these materials were capable of air treatment. To further enhance their anti-microbial activity, silver nanoparticles were decorated onto the TiO2 nanofibers’ surfaces via photoreduction of silver ion in the presence of the nanofibers suspension. Furthermore, tests of photocatalytic activity of the samples were performed by photodegrading methylene blue in water. The nanofibrous membranes prepared from these nanofibers showed superhydrophilicity under UV. Finally, the possibility of using these hybrid nanofibers in environmental and hygienic nanofiltration was proposed, where the self-cleaning characteristics was expected to be valuable in maintenance processes.
Keywords: Titanium dioxide; Nanofibers; Electrospinning; Silver; Nanoparticles; Japan Industrial Standard (JIS); Nitrogen oxide; Volatile organic compound (VOC); Staphylococcus aureus; Escherichia coli; Wetting; Superhydrophilicity; Self cleaning;
A comparative study of droplet impact dynamics on a dual-scaled superhydrophobic surface and lotus leaf by Longquan Chen; Zhiyong Xiao; Philip C.H. Chan; Yi-Kuen Lee; Zhigang Li (8857-8863).
► We study impact dynamics on an artificial superhydrophobic surface and a lotus leaf with V up to 3 m/s. ► Different dynamic behavior was observed and compared on two surfaces with increase V. ► The contact time and restitution coefficient of bouncing droplets on both surfaces were also measured and discussed.The impact dynamics of water droplets on an artificial dual-scaled superhydrophobic surface was studied and compared with that of a lotus leaf with impact velocity V up to 3 m/s. The lower critical impact velocity for the bouncing of droplets was about 0.08 m/s on both surfaces. At relatively low impact velocities, regular rebound of droplets and air bubble trapping and flow jetting on both surfaces were observed as V was increased. For intermediate V, partial pinning and rebound of droplets were found on the artificial dual-scaled surface due to the penetration of the droplets into the micro- and nano-scale roughness. On the lotus leaf, however, the droplets bounced off with intensive vibrations instead of being partially pinned on the surface because of the irregular distribution of microbumps on the leaf. As the impact velocity was sufficiently high, droplet splashing occurred on both surfaces. The contact time and restitution coefficient of the impinging droplets were also measured and discussed.
Keywords: Droplet impact; Superhydrophobic surface; Dual-scale; Rebound; Contact time; Air trapping;
The sputtering properties of artificial polymorphic AB binary compound crystals by M.A. Karolewski (8864-8870).
► The sputtering of polymorphic binary compounds is studied with molecular dynamics. ► Sputtered monomer abundances depend on mass, but not target crystallography. ► Dimer abundance distributions are sensitive to the interatomic potential. ► Nearest-neighbours constitute ∼50% or less of sputtered dimers.Molecular dynamics (MD) simulations of the sputtering of artificial 1:1 binary compound targets, AB, are reported. The simulations explore the sensitivity of monomer and dimer sputter yields to AB target structure and interatomic potentials. The targets have the sphalerite, wurtzite and sodium chloride lattice structures, and their atomic and material properties resemble those of ZnS polymorphs. Two different sets of interatomic potentials were used for the simulations. In the symmetric model, all bonding interactions are equivalent, while in the asymmetric model, the A–B interactions are strengthened at the expense of the A–A and B–B interactions. Both models predict similar material properties for a given target. No systematic variations of sputter yields for individual targets can be discerned between the predictions based on the symmetric and asymmetric interaction models. The relative sputter yields of monomer species A and B are independent of target structure when the A and B atoms occupy surface sites of equivalent symmetry. The relative yields of the AA and BB dimer species are similarly insensitive to the target structure, but target-dependent variations of the relative yields of AB dimers are observed. Sputtering properties other than relative yields (e.g. clustering range, depth of origin) do show structure-dependent variations. In agreement with previous MD studies of sputtering from metals, the nearest-neighbour contribution to AB clusters is found to be typically ∼50%, and may be as low as 30%.
Keywords: Molecular dynamics; Sputtering; Clusters;
The effect of Co ion implantation on Ge1−x Mn x films by Weixia Gao; Li Wang; Denglu Hou; Yuchan Hu; Qian Zhang; Li Ma; Congmian Zhen (8871-8875).
► In this paper, Ge1−x Mn x (x = 0, 0.013, 0.0226, 0.0339, 0.0565, 0.0678, 0.0904, 0.113) films prepared by magnetron sputtering at 773 K had a Ge cubic structure except for x = 0.1130. ► Co ion implantation into these films can effectively prevent the formation of a second phase. ► Different from the previous reports, both single-doped and co-doped samples were ferromagnetic at room temperature. ► The results show that the room-temperature ferromagnetism is intrinsic property.Ge1−x Mn x (x = 0, 0.013, 0.0226, 0.0339, 0.0565, 0.0678, 0.0904, 0.113) films prepared by magnetron sputtering at 773 K had a Ge cubic structure except for x = 0.1130. Co ion implantation into these films can effectively prevent the formation of a second phase. Both single-doped and co-doped samples were ferromagnetic at room temperature. The d–d exchange interaction between the interstitial Mn (MnT) and the substituted Mn (MnGe) resulted in ferromagnetism in the sputtered films. Since Co ion implantation destroyed the MnT–MnGe–MnT complex, the saturated magnetization decreased. Hall measurements revealed that the Co ion implanted films were n-type semiconductors, and the anomalous Hall Effect (AHE) suggested the ferromagnetism was carrier-mediated in the implanted films.
Keywords: Doping; Ion implantation; Magnetic material; Semiconducting material;
Effect of Ar+ irradiation on the electrical conductivity of BaCe0.9Y0.1O3−δ by Jae-Hwan Kim; Heekyu Choi; Tatsuo Shikama (8876-8882).
► We suggest a background for method to improve the electrical conductivity using surface modification. ► Increasing the fluence of Ar+ ion beam increases the number of oxygen vacancy. ► With increased fluence, the hydrogen concentration increased due to the increase in the number of oxygen vacancies, which contributed the formation of proton defects. ► Surface modification results in increase of conductivity.The effects of 10 keV Ar+ ion irradiation on the electrical characteristics of BaCe0.9Y0.1O2.95 subject to fluences of 0, 1.0 × 1017, 5.0 × 1017 and 1.0 × 1018 ions/cm2 at room temperature, has been investigated using elastic recoil detection analysis (ERDA), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and alternating current (AC) impedance measurements. It was confirmed from the ERDA results that the hydrogen concentration near the surface increased with increase of Ar+ ion fluence. This increase may be associated with the increasing quantities of hydrogen generated by interaction between oxygen vacancies, formed by irradiation, and H2O from exposure to air. SEM images showed clearly that the number of surface defects due to modification increased with increasing fluence. In addition, the size of the defects showed a tendency to increase with increasing fluence. From the results of XPS analyses, providing information on the electronic states on the surface, it was evident that with increase in the Ar+ ion fluence, the quantity of excess oxygen, such as hydroxide, increased in the oxygen 1s XPS spectrum. In addition, it was indirectly found, from decomposition of the Ce 3d, spectrum that the concentration of oxygen vacancies increased with fluence, since the percentage of Ce3+ also increased. Accordingly, the surface modification led to the formation of more oxygen vacancies and a greater hydrogen concentration on the surface, since the H2O interacted with some of them. From the results of the DC conductivity and AC impedance measurements, the proton conductivity was shown to predominate over the temperature range from 473 K to 823 K. It was concluded that the increase in these protons and vacancies generated from surface modification contributed to the increase of proton conductivity.
Keywords: Ar+ ion fluence; Surface modification; ERDA; Proton conductivity;
Laser-induced swelling of transparent glasses by S. Logunov; J. Dickinson; R. Grzybowski; D. Harvey; A. Streltsov (8883-8886).
► Demonstration of forming raised features on glass with laser at wavelength region where glass does not absorb light. ► Showed dynamics of the absorbing defects formation in different glasses. ► Demonstrated shape control of formed raised structures on transparent glass.We describe the process of forming bumps on the surface of transparent glasses such as display glasses with moderate thermal expansion ∼3.2 × 10−6 K−1 and high coefficient of thermal expansion (CTE) glasses, e.g. soda-lime glasses with CTE ∼9 × 10−6 K−1 using high-power ultra-violet (UV) lasers at a wavelength where glass is transparent. We characterize the effect with optical dynamic measurements. The process relies on increased glass absorption from color-center generation and leads to glass swelling with bumps formation. The bump height may constitute more than 10% of the thickness of the glass sample. The required exposure time is relatively short ∼1 s, and depends on the glass properties, laser power, its repetition rate, and focusing conditions. A brief review of the potential applications for these bumps is provided.
Keywords: Laser; Glass; Glass swelling; Glass bumps;
Nanomechanical characteristics of annealed Si/SiGe superlattices by Ming-Jhang Wu; Hua-Chiang Wen; Shyh-Chi Wu; Ping-Feng Yang; Yi-Shao Lai; Wen-Kuang Hsu; Wen-Fa Wu; Chang-Pin Chou (8887-8893).
► We evaluated the nanomechanical damage of annealed Si/SiGe strained-layer superlattices. ► The measured values of hardness and elastic moduli of the SLSs films were increased respectively. ► Slight oscillations and discontinuous phenomena in each hardness curve may have been due to the relaxed Si/SiGe structure.In this study, the nanomechanical damage was investigated on the annealed Si/SiGe strained-layer superlattices (SLSs) deposited using an ultrahigh-vacuum chemical vapor deposition (UHVCVD). Nanoscratch, nanoindenter, atomic force microscopy (AFM), and transmission electron microscopy (TEM) techniques were used to determine the nanomechanical behavior of the SiGe films. With a constant force applied, greater hardness number and larger coefficients of friction (μ) were observed on the samples that had been annealed at 600 °C, suggesting that annealing of the Si/SiGe SLSs can induce greater shear resistance. AFM morphological studies of the Si/SiGe SLSs revealed that pile-up phenomena occurred on both sides of each scratch, with the formation of some pellets and microparticles. The Si/SiGe SLSs that had been subjected to annealing under various conditions exhibited significantly different features in their indentation results. Indeed, the TEM images reveal slight dislocation propagation in the microstructures. Thus, the hardness and elastic modulus can be increased slightly after annealing treatment because the existence of comparatively unstable microstructures. It is suggested that cracking phenomena dominate the damage cause of Si/SiGe SLSs.
Keywords: Superlattices; Ultrahigh-vacuum chemical vapor deposition; Atomic force microscopy; Transmission electron microscopy;
Experimental investigations and DICTRA simulations on formation of diffusion-controlled fcc-rich surface layers on cemented carbides by José Garcia; Orlando Prat (8894-8900).
► Fcc-rich diffusion-layers produced by nitridation of WC–Ti–Ta–Nb–C–Co alloys. ► Layer formation controlled by thermodynamic coupling between Ti, Ta, Nb and N. ► 15 μm thick fcc-rich layers formed by nitridation at 1400 °C/5 h/200 mbar N2. ► Kinetics of fcc-rich graded layer formation modeled by DICTRA.Wear resistant fcc-rich surface layers were produced on cemented carbides by nitridation of W–Ti–Ta–Nb–Co–C compositions at 1400 °C in nitrogen atmosphere. A 15 ± 3 μm thick (Ti,Ta,Nb,W)(C,N) top-layer formed on the surface of the cemented carbides. The driving force for formation of the fcc-rich layers was the difference in nitrogen activity between the sintering atmosphere and the cemented carbide bulk, which promoted in-diffusion of nitrogen and out-diffusion of Ti, Ta and Nb. The diffusion-controlled process was modeled by DICTRA considering that all diffusion occurred in the liquid binder phase of a dispersed system model with a labyrinth factor of λ(f) = f. Good agreement between experimental and simulations regarding layer thickness, phase fraction distribution and element profiles was obtained for the presented model.
Keywords: Cemented carbides; Nitridation; Diffusion; Fcc-rich surface layers; DICTRA modeling;
Boron-doped nanocrystalline silicon thin films for solar cells by E. Fathi; Y. Vygranenko; M. Vieira; A. Sazonov (8901-8905).
► We report on structural, electronic, and optical properties of boron-doped nc-Si:H thin films deposited by rf-PECVD. ► Growth of thin nanocrystalline films on ZnO:Al-coated glass substrates by seed-layer technique. ► Optical gap widening due to confinement effect. ► Performance of a-Si:H-based p-i-n solar cells with nc-Si:H doped layers. ►This article reports on the structural, electronic, and optical properties of boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films. The films were deposited by plasma-enhanced chemical vapour deposition (PECVD) at a substrate temperature of 150 °C. Crystalline volume fraction and dark conductivity of the films were determined as a function of trimethylboron-to-silane flow ratio. Optical constants of doped and undoped nc-Si:H were obtained from transmission and reflection spectra. By employing p + nc-Si:H as a window layer combined with a p′ a-SiC buffer layer, a-Si:H-based p–p′–i–n solar cells on ZnO:Al-coated glass substrates were fabricated. Device characteristics were obtained from current–voltage and spectral-response measurements.
Keywords: Thin solid films; Nanocrystalline silicon; PECVD; Solar cells;
Surface micro-texturing of metallic cylindrical surface with proximity rolling-exposure lithography and electrochemical micromachining by Xiuqing Hao; Li Wang; Quandai Wang; Fangliang Guo; Yiping Tang; Yucheng Ding; Bingheng Lu (8906-8911).
► A new method is proposed to fabricate large-area 3D microstructures for cylinder. ► A 2D model is established to optimise the parameters of proximity rolling-exposure. ► The exposure time is three to four times longer than that for a planar layer. ► Increasing the number of exposures or feature sizes will decrease relative errors. ► Ordered microstructures with a feature size of 40 μm are obtained on cylinder.In this paper, a new method is developed for fabricating large-scale three-dimensional (3D) microstructures for cylindrical objects with proximity rolling-exposure lithography (PREL) and electrochemical micromachining (EMM). This method is capable of patterning a wide variety of shapes, including shapes that are impossible to fashion with conventional methods over a large area. A cylindrical rod covered with photoresist is subarea-exposed with a collimated ultraviolet source through a mask by rotating the rod through a definite angle to expose each area. To ensure the shape accuracy of the microstructures, a 2D exposure model is built to predict and optimise such parameters as the rod radius, exposure angle and effective light intensity. The experimental results show that the ideal exposure time for a cylindrical layer is three to four times longer than that for a planar layer with the same thickness. The relative errors of the microstructures decrease as the exposure angle decreases or as the microstructures increase in size. Furthermore, EMM is extended to non-planar surfaces and ordered microstructures with feature sizes down to 40 μm are obtained over large areas on the cylinder.
Keywords: Surface texturing; Rolling-exposure lithography; Cylindrical surface; 3D; Electrochemical micromachining;
Analysis of relative pressure range influence on the identification quality during computer identification of adsorption system parameters by employing the new multilayer adsorption models by Mirosław Kwiatkowski (8912-8922).
► The new original methods for microporous structure parameters identification have been explored with special focus on the influence of the analyzed relative pressure range on the reliability of parameters identification. ► The conducted research was to provide for an answer to the question of whether the range of the analyzed relative pressures has any effect on the quality of adsorption system parameters identification. ► The research results presented in this article will provide interesting information for the specialists engaged in porous structure description, and probably the proposed procedure itself will encourage them to apply it in practice.The aim of this work has been to analyze the problems related to the identification of microporous structure parameters of carbonaceous materials. The new methods for microporous structure parameters identification have been explored with special focus on the influence of the analyzed relative pressure range on the reliability of parameters identification. For that purpose, the adsorption isotherm of nitrogen on active carbon for different ranges of relative pressures p/p 0 was analyzed. The conducted research was to provide for an answer to the question of whether the range of the analyzed relative pressures has any effect on the quality of adsorption system parameters identification, as well as what range of the relative pressure permits execution of the reliable identification of microporous structure parameters.
Keywords: Adsorption; Heterogeneity; Micropores; Isotherms; Computer modeling;
Preparation and characterization of nanocrystalline ITO thin films on glass and clay substrates by ion-beam sputter deposition method by S. Venkatachalam; H. Nanjo; K. Kawasaki; Y. Wakui; H. Hayashi; T. Ebina (8923-8928).
Display Omitted► The as-prepared TiO2 thin film by anodization method is amorphous. ► The amorphous TiO2 can be changed into anatase phase after heat treatment in the range of 400–500 °C. ► Polymer substrates cannot withstand heat up to 450 °C, but the clay substrate can withstand heat up to 460 °C. ► The aim of this work is preparation and characterization of nanocrystalline ITO thin films on transparent flexible clay substrates for flexible dye sensitized solar cell application.Nanocrystalline indium tin oxide (ITO) thin films were prepared on clay-1 (Clay-TPP-LP-SA), clay-2 (Clay-TPP-SA) and glass substrates using ion-beam sputter deposition method. X-ray diffraction (XRD) patterns showed that the as-deposited ITO films on both clay-1 and clay-2 substrates were a mixture of amorphous and polycrystalline. But the as-deposited ITO films on glass substrates were polycrystalline. The surface morphologies of as-deposited ITO/glass has smooth surface; in contrast, ITO/clay-1 has rough surface. The surface roughnesses of ITO thin films on glass and clay-1 substrate were calculated as 4.3 and 83 nm, respectively. From the AFM and SEM analyses, the particle sizes of nanocrystalline ITO for a film thickness of 712 nm were calculated as 19.5 and 20 nm, respectively. Optical study showed that the optical transmittance of ITO/clay-2 was higher than that of ITO/clay-1. The sheet resistances of as-deposited ITO/clay-1 and ITO/clay-2 were calculated as 76.0 and 63.0 Ω/□, respectively. The figure of merit value for as-deposited ITO/clay-2 (12.70 × 10−3/Ω) was also higher than that of ITO/clay-1 (9.6 × 10−3/Ω), respectively. The flexibilities of ITO/clay-1 and ITO/clay-2 were evaluated as 13 and 12 mm, respectively. However, the ITO-coated clay-2 substrate showed much better optical and electrical properties as well as flexibility as compared to clay-1.
Keywords: Ion-beam sputtering; Nanocrystalline; ITO; Flexible clay substrate; XRD; Optical transmittance; SEM; AFM; Electrical conductivity;
Zn–ZrO2 nanocomposite coatings: Elecrodeposition and evaluation of corrosion resistance by Kanagalasara Vathsala; Thimmappa Venkatarangaiah Venkatesha (8929-8936).
Display Omitted► The Zn and Zn–ZrO2 composite coatings were produced by electrodeposition technique using sulphate bath ► The ZrO2 nanoparticles have been selected for generating and investigating the corrosion behavior of Zn–ZrO2 composite coating ► The ZrO2 particle size distribution in the plating bath and Zeta potential and the ZrO2 were measured using dynamic light scattering technique (DLS) ► The corrosion resistance properties of Zn and Zn–ZrO2 composite coatings were compared by examining the experimental data acquired through polarization, open circuit potential (OCP) and Tafel measurements ► The corrosion environment was 3.5 wt% NaCl solution. The results were analyzed to establish the superiority of Zn–ZrO2 composite over Zn coating.The Zn and Zn–ZrO2 composite coatings were produced by electrodeposition technique using sulphate bath. ZrO2 particles were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The ZrO2 particle size distribution in the plating bath and Zeta potential and the ZrO2 were measured using dynamic light scattering technique (DLS). The corrosion resistance properties of Zn and Zn–ZrO2 composite coatings were compared by examining the experimental data acquired through polarization, open circuit potential (OCP) and Tafel measurements. The corrosion environment was 3.5 wt% NaCl solution. The variation of amount of ZrO2 in the solution on their % wt inclusion in the composite and on composite microhardness was investigated. XRD patterns were recorded for Zn and Zn–ZrO2 coatings to compare their grain size. The SEM images of coatings before and after corrosion under chemical and electrochemical conditions were presented. The results were analyzed to establish the superiority of Zn–ZrO2 composite over Zn coating.
Keywords: Zeta potential; Electrodeposition; Composites; Metal matrix; Corrosion; Microstructure;
VO2–WO3 nanocomposite thin films synthesized by pulsed laser deposition technique by Ajay Kaushal; Nitin Choudhary; Navjot Kaur; Davinder Kaur (8937-8944).
► Pure VO2 and VO2–WO3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. ► The influence of varying WO3 molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO2–WO3 nanocomposite thin films has been systematically investigated. ► Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO3 content. ► A remarkable change of the electrical resistance at a very narrow temperature range was observed which corresponds to the semiconductor to metal phase transition temperature. ► An increase in WO3 content results in VO2–WO3 system with increased CV capacity, associated with the modification of the shape of the cyclic voltammogram.Pure VO2 and VO2–WO3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO3 molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO2–WO3 nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO2 phase (m-VO2) up to 10% of WO3 content whereas both m-VO2 as well as h-WO3 (hexagonal WO3) phases were present at higher WO3 content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO3 content. Temperature dependence of resistivity (R–T) measurements indicates significant variation in metal–insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO2–WO3 thin films. A direct correlation between V/W ratio and structure–property relationship was established. The present investigations reveal that doping of WO3 in VO2 is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.
Keywords: VO2–WO3 nanocomposite; Pulsed laser deposition; Metal–insulator transition;
The study on porosity and thermophysical properties of nanostructured La2Zr2O7 coatings by Xueying Wang; Yongping Zhu; Lingzhong Du; Weigang Zhang (8945-8949).
► Nanostructured lanthanum–zirconium coatings were deposited by air plasma spraying. ► The pore size distribution and buck density of coatings were identified by mercury intrusion porosimetry. ► The thermophysical properties of the nanostructured coatings were also examined through laser flash technique and differential scanning calorimetry.Lanthanum–zirconium nano-powders were synthesized by molten salts method. Nanostructured lanthanum–zirconium coatings were deposited by air plasma spraying. Scanning electron microscopy and X-ray diffraction were carried out to analyze the as-sprayed coatings and powders. The pore size distribution and buck density of coatings were identified by mercury intrusion porosimetry. The thermophysical properties of the nanostructured coatings were also examined through laser flash technique and differential scanning calorimetry. The results demonstrate that the as-sprayed nanostructured coatings consist of the pyrochlore-type phase. The as-sprayed nanostructured lanthanum–zirconium coatings have a very low porosity. The thermal conductivity of the as-sprayed nanostructured lanthanum–zirconium coating is lower than that of the conventional coating between 200 °C and 950 °C, but when the temperature between 950 °C and 1300 °C, the result is reverse.
Keywords: Thermophysical properties; La2Zr2O7; Molten salts; Porosity; Nanostructured coatings;
Fabrication and characterization of graphene oxide/zinc oxide nanorods hybrid by Yang Yang; Tianxi Liu (8950-8954).
Display Omitted► A hybrid architecture of graphene oxide (GO)–ZnO nanorods (ZNs) with ZNs attached parallel to GO sheets. ► GO–ZNs hybrid preserves the morphology and crystallinity of initial ZNs. ► Hybrid shows strong stability and reliability of the heterojunction structure. ► Hybrid exhibits electron transfer from excited ZnO to GO sheets.This work presented a hybrid architecture of graphene oxide (GO)/ZnO nanorods (ZNs) with ZNs attached parallel onto GO sheets. ZNs were synthesized by refluxing zinc acetate dehydrate in methanol solution under basic conditions followed by surface modification of 3-aminopropyl triethoxysilane (ATS), and then the preformed ZNs were attached onto GO sheets by reaction of the amino groups on the outer wall of ZNs with the carboxyl groups on the GO surface. Transmission electron microscopy (TEM) image of the as-prepared hybrid reveals the morphology of the architecture of GO/ZNs hybrid. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) ultraviolet–visible (UV–vis) and fluorescence spectroscopy were also performed to characterize the structure and properties of the GO/ZNs hybrid. It was shown that ZNs maintained their initial morphology and crystallinity in the hybrid and the luminescence quenching of yellow-green emission of ZNs confirmed the electron transfer from excited ZnO to GO sheets.
Keywords: Graphene oxide; Zinc oxide; Nanorods; Hybrid;
CH4 dissociation on NiCo (1 1 1) surface: A first-principles study by Hongyan Liu; Riguang Zhang; Ruixia Yan; Baojun Wang; Kechang Xie (8955-8964).
Display Omitted► Build the model of NiCo (1 1 1) slab. ► Obtain the stable adsorption configuration of CH x (x = 0–4). ► Search transition states and calculate the reaction barriers in CH4 dissociation. ► Give the reasons to carbon form on NiCo (1 1 1). ► Dissociation of CH x prefers not to the top of Ni, but to the top of Co.A density-functional theory method has been conducted to investigate the adsorption of CH x (x = 0–4) as well as the dissociation of CH x (x = 1–4) on (1 1 1) facets of ordered NiCo alloy. The results have been compared with those obtained on pure Ni (1 1 1) surface. It shows that the adsorption energies of C and CH are decreased while it is increased for CH3 on NiCo (1 1 1) compared to those on pure Ni (1 1 1). Furthermore, on NiCo (1 1 1), dissociation of CH x prefers not to the top of Ni, but to the top of Co. The rate-determining step for CH4 dissociation is considered as the first step of dehydrogenation on NiCo (1 1 1), while it is the fourth step of dehydrogenation on Ni (1 1 1). Furthermore, the activation barrier in rate-determining step is slightly higher by 0.07 eV on Ni (1 1 1) than that on NiCo (1 1 1). From above results, it is important to point out that carbon is easy to form on NiCo (1 1 1) although the adsorption energy of C atom is slightly decreased compared to that on Ni (1 1 1).
Keywords: Alloy; Dissociation; Adsorption; Reaction barrier; Density functional calculation;
Synthesis, characterization and degradation of Bisphenol A using Pr, N co-doped TiO2 with highly visible light activity by Juan Yang; Jun Dai; Jiantong Li (8965-8973).
. Nitrogen atoms were locally incorporated into the crystal lattice of TiO2, resulting in the response to visible light. Praseodymium ions improved the electron–hole separation process. The enhanced visible photoactivity was attributed to the cooperative effect between praseodymium and nitrogen.Display Omitted► Nitrogen atoms are locally incorporated into the crystal lattice of TiO2, resulting in the band gap narrowing and the response to visible light. ► The praseodymium doping inhibits the anatase-to-rutile phase transformation and retards the growth of crystallite. ► Pr, N-codoped TiO2 exhibits enhanced visible-light photocatalytic activity compared to undoped TiO2, commercial P25 and N-TiO2. ► The synergistic effects of praseodymium and nitrogen lead to high photo-degradation of Bisphenol A under visible light irradiation.Praseodymium and nitrogen co-doped titania (Pr/N-TiO2) photocatalysts, which could degrade Bisphenol A (BPA) under visible light irradiation, were prepared by the modified sol–gel process. Tetrabutyl titanate, urea and praseodymium nitrate were used as the sources of titanium, nitrogen and praseodymium, respectively. The resulting materials were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption isotherm and Fourier transform infrared spectra (FTIR). It was found that Pr doping inhibited the growth of crystalline size and the transformation from anatase to rutile. The degradation of BPA under visible light illumination was taken as probe reaction to evaluate the photo-activity of the co-doped photocatalyst. In our experiments, the optimal dopant amount of Pr was 1.2 mol% and the calcination temperature was 500 °C for the best photocatalytic activity. Pr/N-TiO2 samples exhibited enhanced visible-light photocatalytic activity compared to N-TiO2, undoped TiO2 and commercial P25. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. Pr doping could slow the radiative recombination of photogenerated electrons and holes in TiO2. The improvement of photocatalytic activity was ascribed to the synergistic effects of nitrogen and Pr co-doping.
Keywords: Praseodymium; Nitrogen; Co-doped; Titania photocatalyst; Bisphenol A;
Synthesis and magnetic properties of ordered barium ferrite nanowire arrays in AAO template by Yuqing Li; Ying Huang; Li Yan; Shuhua Qi; Lu Miao; Yan Wang; Qiufen Wang (8974-8980).
► Synthesizing BaFe12O19 nanowire arrays by sol–gel and SHS techniques. ► Obvious magnetic anisotropy with the easy magnetizing axis parallel to the arrays. ► One dimension nanostructure in the nanochannels of the AAO template. ► Near by 11.6 GHz the electromagnetic properties of the arrays are excellent.BaFe12O19 nanowire arrays having single magnetic domain size (≤460 nm) in anodic aluminum oxide (AAO) templates were prepared by sol–gel and self-propagating high-temperature synthesis techniques. The diameter of the nanowire arrays is approximately 70 nm and the length is about 2–4 μm. The specimens were characterized using X-ray diffraction, vibrating sample magnetometer, field emission scan electron microscope, atomic force microscopy and microwave vector network analyzer. The magnetic properties of BaFe12O19 nanowire arrays embedded in AAO templates were measured by VSM with a field up to 1274 KA/m at room temperature. The results indicate that the nanowire arrays exhibit large saturation magnetization and high coercivity in the range of 6000 Oe and an obvious magnetic anisotropy with the easy magnetizing axis along the length of the nanowire arrays, probably due to the shape anisotropy and magneto-crystalline anisotropy. Finally the microwave absorption properties of the nanowires were discussed.
Keywords: Sol–gel; BaFe12O19; Nanowire arrays; AAO template; Magnetic properties;
Effect of precursors on the growth of carbon filaments onto clay surface by Huakang Fu; Miao Du; Qiang Zheng (8981-8984).
Display Omitted► The pristine sodium-montmorillonite only undergoing reflux was acted as a precursor. ► Chemical vapor deposition hardly generated carbon nanotubes with a clear hollow structure on the precursor, but that those with a carbon fiber structure instead. ► The iron species in r-MMT possess higher catalytic activity for the deposition of carbon.The successful growth of carbon filaments on two different precursors, i.e., the pristine sodium-montmorillonite (Na+MMT), which undergoes reflux at 100 °C (r-MMT), and the Na+MMT exchanged with Fe3+ ions (MMT(Fe)), was attained through chemical vapor deposition (CVD). The products obtained were characterized by X-ray diffraction, thermogravimetry, scanning electron microscopy, and transmission electron microscopy. Refluxing can make the Fe3+ ions in the octahedral layer of Na+MMT migrate to the interlayer and exchange with Na+ ions. Furthermore, through calcination at 500 °C, the Fe3+ ions migrate again to the surface of the clay layer and form iron oxides, which can serve as precursors for the deposition of carbon. Although r-MMT contained less iron than the MMT(Fe), the ultimate yield of carbon components grown was almost the same, indicating that the iron species in r-MMT possess higher catalytic activity. However, on the surface of r-MMT, CVD hardly generated carbon nanotubes with a clear hollow structure but that those with a carbon fiber structure instead.
Keywords: Carbon filaments; Montmorillonite; Composites;
Experimental and theoretical evaluation of wettability on micro/nano hierarchically engineered surfaces based on robust micro-post-arrayed- and highly ordered nano-rippled-structures by Dae-Ho Kim; Yongsung Kim; Sung-Hyun Hwang; Yong-Seung Bang; Chae-Ryong Cho; Yong-Kweon Kim; Jong-Man Kim (8985-8992).
► A geometrically regular and stable micro/nano hierarchical surface was proposed. ► The hierarchical surface was demonstrated simply using AAO and MEMS technologies. ► The proposed approach can improve wettability of high-density micro-roughened surface. ► Superhydrophobic robustness of low-density micro-roughened surface was also enhanced.This paper reports a simple approach for demonstrating a micro/nano hierarchical surface, ensuring both geometrical regularity and mechanical stability, for improving the hydrophobicity. The proposed dual-scale hierarchical surfaces were realized simply by combining the highly self-ordered ripple-like nano patterns with the robust micro-post arrays, based on the cost-effective nonlithographic chemical oxidation process and well-established microfabrication technologies. The wettability of the proposed nano-scale mono- and micro/nano dual-roughened surfaces was evaluated by measuring the apparent contact angles (ACAs), and analyzed theoretically with analytic models based on the Wenzel, Cassie, and combined wetting theories. Through experimental and theoretical observations, it was found that the proposed micro/nano hierarchical structures can improve the wetting property and the superhydrophobic robustness of high- and low-density micro-post arrayed surfaces, respectively.
Keywords: Highly self-ordered nano-rippled surface; Micro-post arrays; Micro/nano hierarchical surface; Mechanical stability; Structural regularity; Hydrophobicity; Superhydrophobic robustness;
Impedance spectroscopy of undoped and Cr-doped ZnO gas sensors under different oxygen concentrations by N. Al-Hardan; M.J. Abdullah; A. Abdul Aziz (8993-8997).
► Cr doped ZnO is tested for gas sensing applications and for the best of our knowledge have not been studied previously. ► Cr doped ZnO can detect different oxygen concentration at low operating temperature. The operating temperature of the Cr doped ZnO gas sensor was shifted to 250 °C, and showed an enhancement towards oxygen gas. ► From impedance spectroscopy analysis, it showed that the resistance due to grain boundaries contributed significantly to the response behavior of the gas sensor.Thin films of undoped and chromium (Cr)-doped zinc oxide (ZnO) were synthesized by RF reactive co-sputtering for oxygen gas sensing applications. The prepared films showed a highly c-axis oriented phase with a dominant (0 0 2) peak appeared at a Bragg angle of around 34.13 °, which was lower than that of the standard reference of ZnO powder (34.42 °). The peak shifted to a slightly higher angle with Cr doping. The operating temperature of the ZnO gas sensor was around 350 °C, which shifted to around 250 °C with Cr-doping. The response of the sensor to oxygen gas was enhanced by doping ZnO with 1 at.% Cr. Impedance spectroscopy analysis showed that the resistance due to grain boundaries significantly contributed to the characteristics of the gas sensor.
Keywords: Impedance spectroscopy; Metal oxide sensors; Oxygen gas sensor; RF sputtering; Zinc oxide;
Resistive hysteresis and capacitance effect in NiFe2O4/SrTiO3: Nb(1 wt%) junctions by C. Jin; E.Y. Jiang; H.L. Bai (8998-9001).
► Epitaxial ferrite-based NFO/STON junctions were fabricated by reactive cosputtering. ► Current–voltage curves show rectifying and asymmetrical hysteresis characteristics. ► The hysteretic loops are considered to stem from the capacitance effect. ► The interface of the junction has a large areal capacitance of ∼100 nF/mm2.Epitaxial ultrathin NiFe2O4 films were deposited on 1 wt% Nb-doped SrTiO3 (0 0 1) substrates by reactive cosputtering to form junctions with an area of ∼2 mm2, and current–voltage curves show rectifying and asymmetrical hysteresis characteristics. The resistance calculated from the current–voltage curves is strongly voltage dependent, and the hysteretic loops with high and low resistive states were observed. The hysteretic loops are considered to stem from the capacitance effect of the highly resistive NiFe2O4 layer, which leads to charge accumulation at the interfaces. The results show that the interfaces of the junctions have a large areal capacitance of ∼100 nF/mm2 from 300 to 120 K.
Keywords: Epitaxial NiFe2O4 ultrathin films; Resistive switching; Capacitance effect;
Surface modification of calcium fluoro and hydroxyapatite by 1-octylphosphonic dichloride by Abdallah Aissa; Hassen Agougui; Mongi Debbabi (9002-9007).
► Surface reactivity of hydroxy and fluoroapatite toward 1-octylphosphonic dichloride is tested. ► Chemical analysis shows that hydroxyapatitite is more reactive. ► 31P MAS-NMR spectra show the formation of Ca–O–P bond on the apatitic surface.The reactivity of the surface of calcium hydroxyapatite (CaHAp) and fluorapatite (CaFAp) was tested and compared by grafting the 1-octylphosphonic dichloride (C8H17OPCl2) using a molar ratio x = 2 or 4, x = n(organic)/n(apatite). Successful synthesis was confirmed by different characterisation techniques such as X-ray powder diffraction patterns, IR spectroscopy, MAS-NMR (1H and 31P) and chemical analysis.The difference between their specific surface area (SSA: 57.46 for HAp and 12.09 m2/g for FAp), the percentage of carbon measured after treatment with (C8H17OPCl2) and the intensities of IR bands attributed to the grafted moiety suggests that the surface of hydroxyapatite is more reactive than that of fluorapatite.The 31P CP-MAS-NMR spectra of treated fluorapatite show a significant change in isotropic signal due to the protonation and deprotonation of superficial phosphate group. This can be explained by the difference in the nature of inorganic material.
Keywords: Hydroxyapatite; Fluorapatite; Surface reactivity; 1-Octylphosphonic dichloride;
A general sonochemical approach to rapid synthesis of 1D single-crystalline MSn(OH)6 (M = Ba, Ca, Sr) nanostructures by Xiaoyan Hu; Gang Lv; Zhiyong Jia; Jian Jiang; Ting Xiao; Min Yuan; Yiwen Tang (9008-9013).
. The representative TEM images of BaSn(OH)6 nanowires, CaSn(OH)6 nanotubes, and SrSn(OH)6 nanowires clearly demonstrate that all of them have a good crystallinity and a uniform structure.Display Omitted► We used a facile and quick method-sonochemistry without using any surfactant to rapid synthesize a series of 1D MSn(OH)6 (M = Ba, Ca, Sr) nano-materials. ► We investigated the influences of ultrasound irradiation and the presence of Na2CO3 in the synthetic procedure in detail. ► This approach represents a successful example for the fast construction of inorganic nanostructures in the absence of any surfactant.A general sonochemical approach that allows for a facile, rapid synthesis of MSn(OH)6 (M = Ba, Ca, Sr) one-dimension (1D) nanostructures has been developed. The resulting CaSn(OH)6 products possessed a nanotubular structure while SrSn(OH)6 and BaSn(OH)6 showed nanowire-like structures. The as-synthesized MSn(OH)6 products were characterized by XRD, SEM and TEM techniques. Owing that BaSn(OH)6 nanowires, CaSn(OH)6 nanotubes, and SrSn(OH)6 nanowires takes different crystal structures respectively, they share different growth mechanisms. However, we found that in all three growing processes, both ultrasound irradiation and the presence of Na2CO3 in the synthetic procedure had an significant impact on the homogeneous nucleation and fast growth of 1D MSn(OH)6 nanostructures. This approach represents a successful example for the fast construction of innovative inorganic nanostructures in the absence of any surfactants.
Keywords: 1D MSn(OH)6 nanostructures; Na2CO3; Ultrasound irradiation; Homogeneous nucleation; Fast growth;
Synthesis of α-Fe2O3 nanobelts and nanoflakes by thermal oxidation and study to their magnetic properties by Xinghua Su; Chengshou Yu; Chengwen Qiang (9014-9018).
► The uniform α-Fe2O3 nanobelts and nanoflakes were synthesized by annealing the iron-coated ITO glass in air. ► The shape-dependent magnetic property is investigated. ► The mechanism of the growth of α-Fe2O3 nanobelts and nanoflakes were discussed.α-Fe2O3 nanobelts and nanoflakes have been successfully synthesized by oxidation of iron-coated ITO glass in air. The X-ray diffraction, Raman spectrum and scanning electron microscopy are carried out to characterize the nanobelts and nanoflakes. The formation mechanism has been presented. Significantly, the magnetic investigations show that the magnetic properties are strongly shape-dependent. The magnetization measurements of belt-like and flake-like α-Fe2O3 in perpendicular exhibit ferromagnetic feature with the coercivity (H c) and saturation magnetization (M s) of 334.5 Oe and 1.35 emu/g, 239.5 Oe and 0.12 emu/g, respectively. For the parallel, belt-like and flake-like α-Fe2O3 also exhibit ferromagnetic feature with the H c and M s of 205.5 Oe and 1.44 emu/g, 159.6 Oe and 0.15 emu/g, respectively.
Keywords: Hematite; Nanobelts; Nanoflakes; Magnetic property;
Effects of cooling rate and post-heat treatment on properties of ZnO thin films deposited by sol–gel method by Min Su Kim; Kwang Gug Yim; Dong-Yul Lee; Jin Soo Kim; Jong Su Kim; Jeong-Sik Son; Jae-Young Leem (9019-9023).
► Deposition of precursor solution on Si substrate for the growth of ZnO thin films by sol–gel spin-coating method. ► The solution was cooled with different rates after pre-heat treatment. ► The surface morphology, the residual stress, and the optical properties are affected by the cooling rate. ► The rapid cooling is more suitable than the slow cooling.Sol–gel spin-coated ZnO thin films are cooled with different rates after the pre-heat treatment. Atomic force microscopy (AFM), X-ray diffraction (XRD), Raman, and photoluminescence (PL) were carried out to investigate the effects of the cooling rate during pre-heat treatment on structural and optical properties of the ZnO thin films. The ZnO thin films cooled slowly exhibit mountain chain structure while the ones cooled rapidly have smooth surface. The ZnO thin films cooled rapidly have higher c-axis orientation compared to the ones cooled slowly. The narrower and the higher near-band-edge emission (NBE) peaks are observed in the ZnO thin films cooled rapidly.
Keywords: Zinc oxide; Sol–gel method; Atomic force microscopy; X-ray diffraction; Raman; Photoluminescence;
Mechanochemically conjugated PMHS/nano-SiO2 hybrid and subsequent optimum grafting density study by Jinbin Lin; Hongling Chen; Yongbing Yuan; Yan Ji (9024-9032).
. An appropriate grafting density optimizes the dispersion of nanoparticles in poly(dimethylsiloxane) (PDMS) matrix, too high or too low grafting density may only achieve suboptimal and poor dispersion.Display Omitted► We prepared (PMHS)/SiO2 hybrid particles by mechanochemical method (HEBM). ► Optimum grafting density of PMHS molecules on nano-SiO2 had been also estimated. ► High energy ball milling served as effective mixing device and a special reactor.In this paper, we reported the preparation of poly(methylhydrosiloxane) (PMHS)/SiO2 hybrid particles by mechanochemical method based on high energy ball milling (HEBM). The obtained hybrid particles were characterized by Fourier transform infrared (FT-IR) spectroscopy, 29Si CP (cross-polarization) MAS NMR, viscosity measurement, particle size distribution, thermal analysis (TGA, DSC and DTG), static contact angle (CA), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR and 29Si CP MAS NMR spectra indicate that PMHS is chemically anchored onto the surface of nano-SiO2. Viscosity measurement, particle size distribution, FE-SEM and TEM demonstrate that an appropriate grafting density optimizes the dispersion of nanoparticles in poly(dimethylsiloxane) (PDMS) matrix, so lower viscosity can be achieved. Too high or too low grafting density may only achieve suboptimal and poor dispersions. The optimum grafting density of PMHS on nano-SiO2 was determined by thermal analysis, with approximately 0.0531 PMHS/nm2. Static contact angle measurement indicates that the water contact angle of hybrid particles is modulated by changing the grafting density of PMHS on nano-SiO2. The CA value of PMHS/SiO2 hybrid with optimum grafting density is 139.4°, and the highest CA value of PMHS/SiO2 hybrid is approximately 158.2°.
Keywords: Nano-SiO2; Hybrid particles; Surface modification; Mechanochemical;
Microstructural characterization of Ti–C–N thin films prepared by reactive crossed beam pulsed laser deposition by L. Escobar-Alarcon; V. Medina; Enrique Camps; S. Romero; M. Fernandez; D. Solis-Casados (9033-9037).
► Raman spectroscopy analysis showed a strong dependence of the microstructure on the carbon content in the Ti–C–N films grown by RCBPLD. ► Thin films with a carbon content less than approximately 14 at% form a multiphase solid solution of TiN–TiCN. ► Increasing carbon content in the films promotes the formation of a nanocomposite of TiCN and TiC nanocrystals in an amorphous carbon matrix. ► The Raman features of the Ti–C–N films are very sensitive to carbon content suggesting that the observed Raman shifts could be used to estimate the carbon content in the films.In this work, Raman spectroscopy has been used to characterize Ti–C–N thin films in order to obtain information about the microstructure of the deposited materials, and in particular to study the effects due to the carbon incorporation into the TiN lattice. Ti–C–N thin films were prepared using a crossed plasma configuration in which the ablation of two different targets, titanium and carbon, in a reactive atmosphere was performed. With this configuration, the carbon content in the films was varied in an easy way from 5.0 at% to 40.0 at%. Thin film composition was determined from Non-Rutherford Backscattering Spectroscopy (NRBS) measurements. X-ray photoelectron spectroscopy and X-Ray diffraction measurements were also carried out in order to characterize the films in more detail, with this being used to give support to the interpretation of the Raman spectra. The Raman results revealed that at lower carbon concentrations a solid solution Ti(C, N) is formed, whilst at higher carbon concentrations a nanocomposite, consisting of nanocrystalline TiCN and TiC immersed in an amorphous carbon matrix is obtained.
Keywords: Raman spectroscopy; Titanium nitride; Laser ablation;
Growth and annealing of zinc-blende CdSe thin films on GaAs (0 0 1) by molecular beam epitaxy by Qiumin Yang; Jie Zhao; Min Guan; Chao Liu; Lijie Cui; Dejun Han; Yiping Zeng (9038-9043).
► Zinc-blende CdSe (0 0 1) epilayers were fabricated on GaAs (0 0 1) by MBE. ► The crystalline quality and surface morphology are improved as the substrate temperature increases. ► The epilayer grown at 340 ̊C has the best crystallinity and the smoothest surface. ► The CdSe samples annealed in air maintain the zinc-blende structure below 460 ̊C.CdSe thin films have been grown on GaAs (0 0 1) substrates by molecular beam epitaxy (MBE). The effects of substrate temperature and annealing treatment on the structural properties of CdSe layers were investigated. The growth rate slightly decreases due to the accelerated desorption of Cd from CdSe surface with an increase in the temperature. The sample grown at 260 °C shows a polycrystalline structure with rough surface. As the temperature increases over 300 °C, crystalline CdSe (0 0 1) epilayers with zinc-blende structure are achieved and the structural quality is improved remarkably. The epilayer grown at 340 °C displays the narrowest full-width at half-maximum (FWHM) from (0 0 4) reflection in double-crystal X-ray rocking curve (DCXRC) and the smallest root-mean-square (RMS) roughness of 0.816 nm. Additionally, samples fabricated at 320 °C were annealed in air for 30 min to study the films’ thermal stability. X-ray diffraction (XRD) results indicate that the zinc-blende structure remains unchanged when the annealing temperature is elevated to 460 °C, meaning a good thermal stability of the cubic CdSe epilayers.
Keywords: CdSe; Molecular beam epitaxy; Reflection high energy electron diffraction; X-ray diffraction; Atomic force microscopy;
Nano-structural characteristics and optical properties of silver chiral nano-flower sculptured thin films by Hadi Savaloni; Fatemh Haydari-Nasab; Mariam Malmir (9044-9055).
► Silver chiral nano-flowers with 3-, 4-, and 5-fold symmetry thin films are produced. ► TM (TDM and TQM) and LM Plasmon resonance peaks are observed. ► Oscillation ellipses of polarization spectra for TM and LM are normal to each other.Silver chiral nano-flowers with 3-, 4- and 5-fold symmetry were produced using oblique angle deposition method in conjunction with the rotation of sample holder with different speeds at different sectors of each revolution corresponding to symmetry order of the acquired nano-flower. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), were employed to obtain morphology and nano-structure of the films. Optical characteristics of silver chiral nano-flower thin films were obtained using single beam spectrophotometer with both s- and p-polarization incident light at 30° and 70° incidence angles and at different azimuthal angles (φ). Optical spectra showed both TM (TDM (transverse dipole mode) and TQM (transverse quadruple mode)) and LM (longitudinal mode) Plasmon resonance peaks. For 3- and 4-fold symmetry chiral nano-flowers the s-polarization extinction spectra obtained at different azimuthal angles did not show significant change in the Plasmon peak position while 5-fold symmetry chiral nano-flower showed a completely different behavior, which may be the result of increased surface anisotropy, so when the φ angle is changed the s-polarization response from the surface can change more significantly than that for lower symmetries. In general, for 3-, 4- and 5-fold symmetry chiral nano-flowers a sharp peak at lower wavelengths (<450 nm) is observed in the s-polarization spectra, while in addition to this peak a broad peak at longer wavelengths (i.e., LM) observed in the p-polarization spectra, which is more dominant for 70° incidence angle.
Keywords: Silver chiral nano-flowers; Sculptured thin films; Plasmon resonance peaks; s-polarization; p-polarization;
A facile and flexible process of β-cyclodextrin grafted on Fe3O4 magnetic nanoparticles and host–guest inclusion studies by Jie Zhu; Jiang He; Xiaoyan Du; Ruihua Lu; Lizhen Huang; Xia Ge (9056-9062).
► We have synthesized β-Cyclodextrin modified Fe3O4 magnetic nanoparticles, and the nanoparticles were used as a modified electrode for detecting uric acid. ► We verified that uric acid could form stable host-guest inclusion complexes with cyclodextrins and detected by cyclic voltammograms. ► The new material not only shows the good properties of magnetic nanoparticles but also exhibits molecular recognition properties.In this study, a kind of novel surface-functionalized magnetic nanoparticles was fabricated by the Fe3O4 nanoparticles surface modification with mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD), which were employed to interact with uric acid and their behavior was investigated by electrochemical methods. The architecture has been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), which confirmed that cyclodextrins have been effectively functionalized on the surface of Fe3O4 nanoparticles. The analyses of vibration sample magnetometer (VSM) verified that the nanoparticles owned good magnetic property. The grafted β-cyclodextrin on the Fe3O4 nanoparticles contributed to as a modified electrode for detecting uric acid with cyclic voltammograms. Electrochemical results revealed that the new materials could exhibit excellent molecules recognition ability and show high electrochemical response. The new nanoparticles simultaneously had unique properties of magnetic nanoparticles and cyclodextrins through combining their individual distinct advantages.
Keywords: Magnetic nanoparticles; β-Cyclodextrin; Uric acid; Electrochemistry; Host–guest inclusion;
Structural and electrochemical properties of polythiophene by B. Senthilkumar; P. Thenamirtham; R. Kalai Selvan (9063-9067).
► Polythiophenes were synthesized by chemical oxidative polymerization method in presence and absence of three different surfactants. ► The surfactant changes the morphology of the polythiophene ► The higher specific capacitance of 117 F/g was obtained for the polythiophene prepared with TRITRON X-100.Polythiophenes (PTs) were prepared by chemical oxidative polymerization method in presence and absence of three different (cationic – CTAB, anionic – SDS and non-ionic – Triton X-100) surfactants using FeCl3 as oxidant. The prepared PTs were characterized by FT-IR, UV–Vis, XRD, SEM and cyclic voltammetry studies. The FT-IR spectra inferred the polymerization of thiophene and elucidate the corresponding functional groups of PTs. Our results on the UV–Vis spectra demonstrate the n−π* electronic transition of the conjugated molecules. Further the red shift in the absorption peak confirms the longer conjugation length of PTs. The amorphous nature of the PTs was inferred from the XRD pattern. The PTs prepared with surfactant exhibited different morphology compared to PT prepared without surfactant. The specific capacitances (SC) of the prepared PTs were calculated using cyclic voltammetry technique, the PT prepared with TRITRON X-100 exhibited higher SC of 117 F/g compared to SC of surfactant free PT (78 F/g). Hence, the PTs prepared with surfactants were found to be suitable electrode materials for redox supercapacitors.
Keywords: Polythiophene; Chemical oxidative polymerization; Ionic surfactants; Redox supercapacitor; Specific capacitance;
Investigation on the effect of Zr doping in ZnO thin films by spray pyrolysis by V. Gokulakrishnan; S. Parthiban; K. Jeganathan; K. Ramamurthi (9068-9072).
► Zr doped ZnO films were deposited by spray pyrolysis. ► Average transmittance of 5 at.% Zr doped ZnO film is ∼92% in the visible region. ► The crystalline quality was deteriorated with the increase of Zr doping. ► 3 at.% Zr doped ZnO film possesses lowest resistivity of 2 × 10−3 Ω cm. ► RMS and grain size decrease with the increase of Zr doping.Zirconium doped zinc oxide thin films with enhanced optical transparency were prepared on Corning 1737 glass substrates at the substrate temperature of 400 °C by spray pyrolysis method for various doping concentrations of zirconium (IV) chloride in the spray solution. The X-ray diffraction studies reveal that the films exhibit hexagonal crystal structure with polycrystalline grains oriented along (0 0 2) direction. The crystalline quality of the films is found to be deteriorating with the increase of doping concentration and acquires amorphous state for higher concentration of 8 at.% in precursor solution. The average transmittance for 5 at.% (solution) zirconium doped ZnO film is significantly increased to ∼92% in the visible region of 500–800 nm. The room temperature photoluminescence (PL) spectra of films show a band edge between 3.41 and 3.2 eV and strong blue emission at 2.8 eV irrespective of doping concentration and however intensity increases consistently with doping levels. The vacuum annealing at 400 °C reduced the resistivity of the films significantly due to the coalescence of grains and the lowest resistivity of 2 × 10−3 Ω cm is observed for 3 at.% (solution) Zr doped ZnO films which envisages that it is a good candidate for stable TCO material.
Keywords: Thin films; X-ray diffraction; Atomic force microscopy; Optical properties and electrical properties;
Abrasive wear under multiscratching of polystyrene + single-walled carbon nanotube nanocomposites. Effect of sliding direction and modification by ionic liquid by M.D. Bermúdez; F.J. Carrión; C. Espejo; E. Martínez-López; J. Sanes (9073-9081).
► SWCNT and ionic liquid as anti-abrasion PS additives. ► Multiple scratch resistance and strain hardening are a function of additive and sliding direction. ► Modification of carbon nanotubes by ionic liquid provides the lowest friction and surface damage.Single-walled carbon nanotubes (NTs) and single-walled carbon nanotubes modified (NTms) by the room-temperature ionic liquid (IL) 1-octyl, 3-methylimidazolium tetrafluoroborate ([OMIM]BF4) were added in a 1 wt.% to polystyrene (PS) and processed by compression or injection moulding to obtain PS + NT and PS + NTm, respectively. Friction coefficients and abrasive wear from penetration depth, residual depth and viscoelastic recovery were determined under multiple scratching. The effect of the moulding process, the additives and the sliding direction was studied. Compression moulded PS shows a transition to more severe damage after a critical number of successive passes. Addition of NTs or NTms to compression moulded PS induces a strain hardening effect and reduces friction, residual depth and viscoelastic recovery. Strain hardening is also observed in injection moulded PS with sliding in the longitudinal and random directions, but not in the transverse direction. The scratch resistance of PS + NTm depends on sliding direction. The lowest friction coefficient and residual depth values, and the highest viscoelastic recovery were found for injection moulded PS + NTm, in the sliding direction parallel to injection flow. Mechanisms of surface damage are discussed upon scanning electron microscopy (SEM), focused ion beam-field emission scanning electron microscopy (FIB-FESEM), 3D surface topography, surface roughness and profilometry observations.
Keywords: Polymer-matrix composites (PMCs); Single-walled carbon nanotubes (SWCNT); Ionic liquid; Abrasive wear; Multiple scratching; Anisotropy;
Carbon nanosheets by microwave plasma enhanced chemical vapor deposition in CH4–Ar system by Zhipeng Wang; Mao Shoji; Hironori Ogata (9082-9085).
► Catalyst-free CNSs were firstly achieved in Ar–CH4 by MPECVD at 450–500 °C. ► The CNSs possess many shape edges which consist of a few layers of graphene. ► The CNSs have demonstrated a faster electron transfer. ► The results provide the possibility for lower-temperature growth of graphene.We employ a new gas mixture of CH4–Ar to fabricate carbon nanosheets by microwave plasma enhanced chemical vapor deposition at the growth temperature of less than 500 °C. The catalyst-free nanosheets possess flower-like structures with a large amount of sharp edges, which consist of a few layers of graphene sheets according to the observation by transmission electron microscopy. These high-quality carbon nanosheets demonstrated a faster electron transfer between the electrolyte and the nanosheet surface, due to their edge defects and graphene structures.
Keywords: Carbon nanosheets; Graphene; Low temperature; MPECVD;
Enhanced in vitro biocompatibility of ultrafine-grained biomedical NiTi alloy with microporous surface by C.Y. Zheng; F.L. Nie; Y.F. Zheng; Y. Cheng; S.C. Wei; R.Z. Valiev (9086-9093).
A porous surface layer (a) was produced on ultrafine-grained Ni50.8Ti49.2 alloy (UFG NiTi) surface by sandblasting with HF/HNO3 acid etching (AE-NiTi). This surface is bioactive and could yield apatite formation when soaked in simulated body fluid for 14 days (b). Osteoblast-like cells attached well after 4 h incubation (c1) and proliferated significantly after 3 days culture (c2). Such porous surface also presented lower corrosion rate and high pitting corrosion resistance in simulated body fluid compared with untreated coarse-grained NiTi (CG Ti) and UFG NiTi, as well as UFG NiTi with sandblasting (SB-NiTi) and UFG NiTi with combined sandblasting, acid etching and alkali treatment (AEAT-NiTi).Display Omitted► Irregularly rough, microporous and hierarchical porous surfaces were produced by sandblasting, acid etching and alkali treatment. ► Sandblasting with acid etching followed by alkaline treatment severely impaired the corrosion resistance. ► Sandblasting plus HF/HNO3 solution etching increased the apatite forming ability. ► Sandblasting enhanced cell attachment and acid etching increased cell proliferation.Bulk ultrafine-grained Ni50.8Ti49.2 alloy (UFG-NiTi) was successfully fabricated by equal-channel angular pressing (ECAP) technique in the present study, and to further improve its surface biocompatibility, surface modification techniques including sandblasting, acid etching and alkali treatment were employed to produce either irregularly roughened surface or microporous surface or hierarchical porous surface with bioactivity. The effect of the above surface treatments on the surface roughness, wettability, corrosion behavior, ion release, apatite forming ability and cytocompatibility of UFG-NiTi alloy were systematically investigated with the coarse-grained NiTi alloy as control. The pitting corrosion potential (E pit) was increased from 393 mV (SCE) to 704 mV (SCE) with sandblasting and further increased to 1539 mV (SCE) with following acid etching in HF/HNO3 solution. All the above surface treatment increased the apatite forming ability of UFG-NiTi in varying degrees when soaked them in simulated body fluid (SBF). Meanwhile, both sandblasting and acid etching could promote the cytocompatibility for osteoblasts: sandblasting enhanced cell attachment and acid etching increased cell proliferation. The different corrosion behavior, apatite forming ability and cellular response of UFG-NiTi after different surface modifications are attributed to the topography and wettability of the resulting surface oxide layer.
Keywords: Ultrafine-grained alloy; Surface modification; Corrosion resistance; Cytocompatibility;
Tailoring nickel coatings via electrodeposition from a eutectic-based ionic liquid doped with nicotinic acid by Haiyan Yang; Xingwu Guo; Nick Birbilis; Guohua Wu; Wenjiang Ding (9094-9102).
► An additive known to work in aqueous baths is demonstrated to be effective in IL. ► The ability of an acid to ‘tune’ the electrodeposition achieved in IL is apparent. ► Effect of NA on the voltammetric behavior of Ni (II) and nucleation/growth of Ni deposits was revealed. ► Effect of NA on the morphology and microstructure of the Ni was studied. ► It is shown that NA has a profound impact on grain size reduction.Pure nickel (Ni) was electrodeposited onto a copper (Cu) substrate from choline chloride–urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl–urea IL) with 0–1200 mg/L additions of nicotinic acid (NA). The effect of NA on the voltammetric behavior of Ni (II) was investigated by cyclic voltammetry, whilst the nucleation/growth of Ni deposits was studied by chronoamperometry. The resultant surface morphologies and microstructures of the Ni coatings were revealed by SEM/EDXS, XRD and TEM, demonstrating that NA can inhibit, hence tailor, the Ni deposition and serve as a very effective brightener producing highly uniform and smooth Ni deposits. The nucleation/growth process of Ni was not affected by the presence of NA, proceeding via three-dimensional instantaneous nucleation. NA has a profound grain refining effect with a grain size of ∼4.2 nm achievable.
Keywords: Electrodeposition; Ionic liquid; Nickel coating; Brightener; Nanocrystalline; Nucleation/growth;
Sol–gel synthesis, characterization and optical properties of mercury-doped TiO2 thin films deposited on ITO glass substrates by R. Mechiakh; N. Ben Sedrine; R. Chtourou (9103-9109).
► Elaboration and characterization of structural and optical properties. ► Sol–gel. ► Nano materials, nano systems, thin films, surfaces and interfaces, applications.The Hg-doped and undoped nano-crystalline TiO2 films on ITO glass substrates surface and polycrystalline powders were prepared by sol–gel dip coating technique. The crystal structure and surface morphology of TiO2 were characterized by means of X-ray diffractometer (XRD), atomic force microscope (AFM), spectrophotometer, Fourier-transform infrared (FTIR), and spectroscopic ellipsometry (SE). The results indicated that the powder of TiO2, doped with 5% Hg in room temperature was only composed of the anatase phase whereas in the undoped powder exhibits an amorphous phase were present. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 400 °C. The average crystallite size of the undoped TiO2 films was about 8.17 nm and was increased with Hg-doping in the TiO2 films. Moreover, the grains distributed more uniform and the surface roughness was greater in the Hg-doped TiO2 films than in the undoped one. Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range (1.95–2.49) and the porosity is in the range (47–2.8). The coefficient of transmission varies from 60 to 90%. SE study was used to determine the annealing temperature effect on the optical properties in the wavelength range from 0.25 to 2 μm and the optical gap of the Hg-doped TiO2 thin films.
Keywords: Mercury; Titanium oxide; Thin films; Anatase; Sol–gel; Thermal treatment;
XPS, XRD and SEM characterization of a thin ceria layer deposited onto graphite electrode for application in lithium-ion batteries by Jolanta Światowska; Virginie Lair; Catarina Pereira-Nabais; Gérard Cote; Philippe Marcus; Alexandre Chagnes (9110-9119).
► Electro-precipitation of ceria on graphite. ► Graphite modification by ceria thin film for negative electrodes. ► Reversible insertion and deinsertion of lithium in graphite through ceria layer. ► Formation of solid electrolyte interphase (SEI) layer.Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6 nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge–discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1 M LiPF6 show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7 V vs Li/Li+ on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li2CO3, ROCO2Li, R–CH2OLi and LiF, is different than those obtained on the graphite.
Keywords: Lithium ion battery; Ceria; Graphite; SEI layer; Electro-precipitation; XPS;
Preparation and characterization of CrN x O y thin films: The effect of composition and structural features on the electrical behavior by R. Arvinte; J. Borges; R.E. Sousa; D. Munteanu; N.P. Barradas; E. Alves; F. Vaz; L. Marques (9120-9124).
► CrN x O y thin films were deposited by DC reactive magnetron sputtering. ► The thin films structural and electrical properties were investigated. ► Three different types of films were found depending on deposition parameters. ► The electrical resistivity depends strongly on thin film chemical composition.Metallic oxynitrides have attracted the attention of several researchers in the last decade due to their versatile properties. Through the addition of a small amount of oxygen into a transition metal nitride film, the material's bonding states between ionic and covalent types can be tailored, thus opening a wide range of electrical, optical, mechanical and tribological responses. Among the oxynitrides, chromium oxynitride (CrN x O y ) has many interesting applications in different technological fields. In the present work the electrical behavior of CrN x O y thin films, deposited by DC reactive magnetron sputtering, were investigated and correlated with their compositional and structural properties. The reactive gas flow, gas pressure, and target potential were monitored during the deposition in order to control the chemical composition, which depend strongly on reactive sputtering process. Depending on the particular deposition parameters that were selected, it was possible to identify three types of films with different growth conditions and physical properties. The electrical resistivity of the films, measured at room temperature, was found to depend strongly on the chemical composition of the samples.
Keywords: Magnetron sputtering; Electrical resistivity; Chromium oxynitride;
Thermal shock induced nanocrack as high efficiency surface conduction electron emitter by Bangdao Chen; Hongzhong Liu; Hongtao Wang; Fan Fan; Li Wang; Yucheng Ding; Bingheng Lu (9125-9128).
► Significant emission current enhancement has been achieved for surface conduction electron emitter, fabricated by the thermal shock process. ► The three-dimensional configuration strongly changed the electric field distribution and controlled the emission electron trajectory. ► Thermal shock treatment was used to increase the edge roughness of the nanocrack and improved the field emission characteristics. ► This nanocrack structure can be used in some advanced applications, such as molecular devices and chemical sensors.Significant emission current enhancement has been achieved for surface conduction electron emitter, due to the special three-dimensional nanocrack structure fabricated by the thermal shock process. The three-dimensional configuration strongly changed the electric field distribution and controlled the emission electron trajectory. Thermal shock treatment was also used to increase the edge roughness of the nanocrack and thereby dramatically improved the field emission characteristics. Stable and uniform electron emission was observed with turn-on voltage of 150 V. The surface conduction current of 400 μA for 6 cells was obtained with the detector voltage of 1 kV and the gap voltage of 170 V.
Keywords: Thermal shock; Nanocrack; Surface conduction electron emitter;
Morphological and optical properties changes in nanocrystalline Si (nc-Si) deposited on porous aluminum nanostructures by plasma enhanced chemical vapor deposition for Solar energy applications by M. Ghrib; M. Gaidi; T. Ghrib; N. Khedher; M. Ben Salam; H. Ezzaouia (9129-9134).
Photoluminescence (PL) spectroscopy was used to determine the electrical band gap of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous alumina structure by fitting the experimental spectra using a model based on the quantum confinement of electrons in Si nanocrystallites having spherical and cylindrical forms. This model permits to correlate the PL spectra to the microstructure of the porous aluminum silicon layer (PASL) structure. The microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). It was found that the structure of the nanocrystalline silicon layer (NSL) is dependent of the porosity (void) of the porous alumina layer (PAL) substrate. This structure was performed in two steps, namely the PAL substrate was prepared using sulfuric acid solution attack on an Al foil and then the silicon was deposited by plasma enhanced chemical vapor deposition (PECVD) on it. The optical constants (n and k as a function of wavelength) of the deposited films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV–vis–NIR regions. The SE spectrum of the porous aluminum silicon layer (PASL) was modeled as a mixture of void, crystalline silicon and aluminum using the Cauchy model approximation. The specific surface area (SSA) was estimated and was found to decrease linearly when porosity increases. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties.
Keywords: Porous aluminum; Nanocrystalline silicon (nc-Si); Ellipsometry; Photoluminescence (PL);
Corrosion and wear properties of PEO coatings formed on AM60B alloy in NaAlO2 electrolytes by Xijin Li; XingYang Liu; Ben Li Luan (9135-9141).
► The microstructure, phase constituents, corrosion and wear resistance of PEO coatings formed on AM60B alloy in electrolytes with different NaAlO2 concentrations were investigated. ► The main phases in the coating were revealed by X-ray diffraction to be MgAl2O4 and MgO, and the relative amount of MgAl2O4 in the coatings increased with increasing NaAlO2 concentration in the electrolyte. The coatings were relatively compact and provided significantly improved corrosion resistance for magnesium alloy. Pin-on-disk wear tests showed that the PEO treatment reduced the wear volume loss by a factor of 10.Coatings with a thickness of 22–32 μm were formed on an AM60B magnesium alloy by plasma electrolytic oxidation (PEO) in electrolytes containing 12.0–24.0 g/l NaAlO2 and other additives. SEM analyses of the coated samples showed that the coatings were compact with relatively low porosity. X-ray diffraction revealed that the coatings consisted of mainly MgAl2O4 and MgO phases. The relative amount of MgAl2O4 in the coating increased with increasing NaAlO2 concentration. The relatively compact and thick coatings provide good corrosion protection for magnesium, as indicated by the results of potentiodynamic polarization tests. In addition, the PEO treatment also significantly improved the wear resistance of the alloy. Pin-on-disk wear tests showed that the PEO treatment reduced the wear volume loss by a factor of 10.
Keywords: Plasma electrolytic oxidation; Magnesium alloy; Corrosion; Wear; Coating;
Preparation of organic/inorganic hybrid nanocomposites by ultraviolet irradiation and their packaging applications for organic optoelectronic devices by Ming-Hua Chung; Jian-Shian Lin; Tsung-Eong Hsieh; Nien-Po Chen; Fuh-Shyang Juang; Chen-Ming Chen; Lung-Chang Liu (9142-9151).
► Lab-made nanocomposite g was synthesized under UV irradiation. ► Lab-made nanocomposite g was applied for the encapsulation of OLEDs, flexible OLEDs, and organic solar cells. ► With the package of lab-made nanocomposite g, the lifetimes of organic optoelectronic devices have been effectively extended.By ultraviolet (UV)-assisted synthetic procedure, we have successfully prepared several UV curable organic/inorganic hybrid nanocomposites with excellent gas barrier capabilities, moderate hardness, and good adhesive strength. The experimental results reveal that the physical properties of nanocomposites depend on their chemical structures. Therefore, introduction of silicone and polyurethane (PU) into the Acrylics backbone dramatically raises the adhesive strength as well as refractive index and lowers the gas penetration. Furthermore, we have also applied lab-made nanocomposite g for the encapsulation of organic optoelectronic devices such as OLEDs, flexible OLEDs, and organic solar cells. With the package of lab-made nanocomposite g, the organic optoelectronic devices effectively resist the entry of moisture and oxygen in the air, extending the lifetimes.
Keywords: Organic light emitting diode; Lifetime; Package; Organic solar cell; Optoelectronic device;
Tunable wettability of carbon nanotube/poly (ɛ-caprolactone) hybrid films by Chih-Feng Wang; Chih-Siang Liao; Shiao-Wei Kuo; Han-Ching Lin (9152-9157).
► We prepared three kinds of organic/inorganic hybrid film with different wettabilities. ► The wettability of the film can be controlled by its surface morphology and chemistry. ► The water droplet mobilities were reversibly switched on the tunable superhydrophobic surface. ► The wettabilities were reversibly switched on the tunable hydrophobic surface.We have realized a stable superhydrophobic surface, a thermally tunable superhydrophobic surface, and a thermally tunable hydrophobic surface by combining the crystalline/amorphous phase transition of the poly(ɛ-caprolactone) (PCL) with the optimized surface roughness of the carbon nanotube/PCL hybrid films. The water droplet mobilities and wettabilities were reversibly thermally switched on the tunable superhydrophobic and the hydrophobic surfaces, respectively. These responsive surfaces have potential applications in microfluidic devices and microreactors and for liquid transportation.
Keywords: Carbon nanotubes; Superhydrophobic; Reversible; Mobility;
An undercutting model of atomic oxygen for multilayer silica/alumina films fabricated by plasma immersion implantation and deposition on polyimide by Yongxian Huang; Xiubo Tian; Shixiong Lv; Shiqin Yang; R.K.Y. Fu; Paul K. Chu; Jinsong Leng; Yao Li (9158-9163).
► The undercutting model of polymer covered with protective film induced by AO was defined. ► The AO erosion mechanism of polyimide has been investigated using a ground-based AO simulator and Monte Carlo model. ► AO erosion predictions at two neighborhood cracks is first studied by Monte Carlo model. ► Multilayer silica/alumina films were created by plasma immersion implantation and deposition for protection against AO.Multilayer silica/alumina films were created by plasma immersion implantation and deposition to protect against atomic oxygen (AO) in low earth orbit environment. The AO erosion mechanism of polyimide under multilayer silica/alumina films has been investigated using a ground-based AO simulator and Monte Carlo model. The results demonstrate that protective films are detached and plumped due to AO undercutting, and the exterior silica film is partly detached proven by chemical composition depth profile and erosion patterns. The undercutting model involving collision, diffusion, reaction, gas releasing, and retroaction on films is proposed. Based on the model, scattered impingement has serious erosion, although AO does not directly attack interior polymer. AO erosion predictions at two neighborhood cracks are first studied by Monte Carlo model for various incidence angles of AO. The protective film between cracks hinders the escape of AO, and accelerates the erosion.
Keywords: Polymer; Multilayer thin films; Erosion; Plasma immersion; Monte Carlo;
Modifying the TiAlZr biomaterial surface with coating, for a better anticorrosive and antibacterial performance by Daniela Ionita; Mihaela Grecu; Camelia Ungureanu; Ioana Demetrescu (9164-9168).
► A new composite for biomedical applications was elaborated by coating TiAlZr with Ag nanoparticles. ► The morphological and elemental analysis of Ag nanoparticles on the TiAlZr surface were performed with scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). ► The better electrochemical performance of the coating (compared with polished TiAlZr) was evaluated from dynamic polarization tests. ► Antibacterial activity was evaluated on the basis of the inhibition of the growth of Escherichia coli bacteria.The paper investigates the increase of anticorrosive and antimicrobial properties of a composite elaborated by coating TiAlZr with Ag nanoparticles. Silver nanoparticles (AgNPs) were synthesized by reducing silver salts using NaBH4, and were characterized using dynamic light scattering instrument to determine the size distribution. The morphological and elemental analysis of Ag nanoparticles on the TiAlZr surface were performed with scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). Antibacterial activity was evaluated on the basis of the inhibition of the growth of Escherichia coli bacteria, and of the electrochemical parameters from dynamic polarization tests performed in Ringers bioliquid.An empirical model of antibacterial effect of silver nanoparticles at biointerface in the presence of TiAlZr implant was discussed.
Keywords: Antimicrobial effect; Anticorrosive properties; TiAlZr; Silver nanoparticles;
Catalytic performance and characterization of Ni–CaO–ZrO2 catalysts for dry reforming of methane by Nannan Sun; Xia Wen; Feng Wang; Weicai Peng; Ning Zhao; Fukui Xiao; Wei Wei; Yuhan Sun; Jinting Kang (9169-9176).
► Texture properties of catalysts depend significantly on the preparation procedure. ► Better performance was observed over the co-precipitation and refluxed C-NiCaZr. ► Ni–ZrO2 interface is essential for the stability of C-NiCaZr.Ni–CaO–ZrO2 catalysts for CO2 reforming of CH4 were prepared by either co-precipitation or impregnation and characterized by means of N2 adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed (TP) techniques. It was found that the preparation procedure greatly influenced the physicochemical properties of catalysts, such as morphology, phase and surface structure. As a result, their activity in CO2 reforming of CH4 was determined by the dispersion of Ni and the co-precipitated catalysts showed a better stability. Furthermore, CO2-TPD and transient pulse experiments suggested that the carbon formed over two co-precipitated catalysts was eliminated by different mechanisms, and redox properties and strong basicity were believed to be the key factor for the stability, respectively.
Keywords: Ni catalyst; ZrO2; Methane; Reforming;
Insight into the thermionic emission regimes under gold film thermal relaxation excited by a femtosecond pulse by Guangqing Du; Qing Yang; Feng Chen; Jinhai Si; Xun Hou (9177-9182).
► We investigated the role of the two temperature relaxation and the thermal diffusion relaxation participating in ultrafast thermionic emission processes. ► The thermionic emission rate profiles would emerge as alternative shapes of single peak or two-part structure, depending on the laser parameters. ► There exists a transition between two thermionic emission regimes under the peculiar laser conditions.We theoretically investigated different thermal relaxation participating in the ultrafast thermionic emission processes on gold film surface with a femtosecond pulse excitation. The thermionic emission regimes under the two temperature relaxation and the thermal diffusion relaxation were demonstrated. The simulations showed that the thermionic emission properties can be defined in the regime under two temperature relaxation by reducing the laser fluence, or widening the pulse duration or increasing the laser wavelength. It was also found that there exists a transition between the two distinct thermionic emission regimes under peculiar laser parameters of laser fluence, pulse duration and laser wavelength. The results were explained as significant intervene of laser irradiation parameters into gold film thermal relaxation processes.
Keywords: Femtosecond laser pulse; Thermionic emission regimes; Two temperature relaxation; Thermal diffusion relaxation;
Microstructural evolution upon annealing in Ar-implanted Si by B.S. Li; C.H. Zhang; Y.T. Yang; L.Q. Zhang; C.L. Xu (9183-9187).
► Microstructural evolution upon annealing in Ar-implanted Si was studied. ► Before and after annealing up to 600 °C, an amorphous layer is formed but Ar bubbles are not observed in the damage layer. ► After annealing at 800 °C, three buried layers of Ar bubbles are found. ► After annealing at 1100 °C, exfoliation occurs on the surface and microtwin lamellas form in the damage layer. ► A strong recrystallization occurs at 600 to 800 °C annealing.The annealing effects of crystalline silicon (Si) implanted with argon (Ar) ions at a dose of 2 × 1016 Ar+/cm2 at room temperature and subsequently annealed at 400–1100 °C for 30 min were investigated. The samples were analyzed by transmission electron microscopy and Raman spectroscopy. Before and after annealing up to 600 °C, an amorphous layer is formed but Ar bubbles are not observed in the damage layer. After annealing at 800 °C, argon bubbles are observed together with extended defects. The damage layer evolves into a polycrystalline structure. After annealing at 1100 °C; exfoliation occurs on the sample surface, and microtwin lamellas form in the damage layer. Raman scattering revealed that a strong recrystallization occurs from 600 °C to 800 °C. The results were compared with the case of helium implantation, with particular focus on bubble formation mechanisms.
Keywords: Ion implantation; Annealing; Bubbles; Defects; Transmission electron microscopy;
Synthesis and analysis of silicon nanowire below Si–Au eutectic temperatures using very high frequency plasma enhanced chemical vapor deposition by Habib Hamidinezhad; Yussof Wahab; Zulkafli Othaman; Abd Khamim Ismail (9188-9192).
► Gold colloid and SiH4 were used as catalytic and precursor gas, respectively, to grow silicon nanowires using the very high frequency plasma enhanced chemical vapor deposition (VHFPECVD) technique. ► The SiNWs have grown at below Au–Si eutectic temperature (as low as 250 °C). ► SiNWs were grown via vapor–solid–solid (VSS) mechanism. ► SiNWs have a crystalline Si core and amorphous sheath.Silicon nanowires (SiNWs) were synthesized from pure silane precursor gas and Au nanoparticles catalyst at below Au–Si eutectic temperature. The SiNWs were grown onto Si (1 1 1) substrates using very high frequency plasma enhanced chemical vapor deposition via a vapor–solid–solid mechanism at temperatures ranging from 363 to 230 °C. The morphology of the synthesized SiNWs was characterized by means of field emission scanning electron microscope equipped with energy dispersive X-ray, high resolution transmission electron microscopy, X-ray diffraction technique and Raman spectroscope. Results demonstrated that the SiNWs can be grown at the temperature as low as 250 °C. In addition, it was revealed that the grown wires were silicon-crystallized.
Keywords: Eutectic temperature; Silicon nanowire; VSS; VHF-PECVD;
Nitrogen doping effects on the structure of graphene by Dongsheng Geng; Songlan Yang; Yong Zhang; Jinli Yang; Jian Liu; Ruying Li; Tsun-Kong Sham; Xueliang Sun; Siyu Ye; Shanna Knights (9193-9198).
► N-graphene was prepared by the heat-treatment of graphene using ammonia. ► N-doping effects on graphene microstructure and bonding were investigated. ► XANES results reveal the unoccupied DOS increases after the N-doping. ► N-doping decreases the surface oxygen-containing groups.Graphene and nitrogen doped graphene have been prepared by modified Hummers’ method and the following ammonia heat-treatment process, respectively. The effects of N-doping on the structure of graphene have been systematically investigated by various characterization techniques. SEM, TEM, BET, Raman and XRD analysis were used to distinguish the difference of the microstructures; and FT-IR, XPS, especially XANES were performed to elucidate the bonding information such as C–N. The effect of nitrogen doping on the structure of graphene has been obtained. More defects are present on nitrogen doped graphene as elucidated by BET, XRD, Raman, and XANES characterizations. XANES analysis also indicates that the N-doping decreases the surface oxygen-containing groups.
Keywords: Graphene; Nitrogen doping; Defects; Structure;
Structural effects of C60 + bombardment on various natural mineral samples—Application to analysis of organic phases in geological samples by S. Siljeström; J. Lausmaa; T. Hode; M. Sundin; P. Sjövall (9199-9206).
► Organic phases trapped inside rocks may be accessed by ToF-SIMS depth profiling. ► To access the phases several micrometers of C60 + sputtering is needed. ► Sputtering induces topography and carbon deposition on the mineral surface. ► The topography is caused by chemical heterogeneities in the sample surface. ► The topography and carbon deposition do not affect the analysis of organic phases.Organic phases trapped inside natural mineral samples are of considerable interest in astrobiology, geochemistry and geobiology. Examples of such organic phases are microfossils, kerogen and oil. Information about these phases is usually retrieved through bulk crushing of the rock which means both a risk of contamination and that the composition and spatial distribution of the organics to its host mineral is lost. An attractive of way to retrieve information about the organics in the rock is depth profiling using a focused ion beam. Recently, it was shown that it is possible to obtain detailed mass spectrometric information from oil-bearing fluid inclusions, i.e. small amounts of oil trapped inside a mineral matrix, using ToF-SIMS. Using a 10 keV C60 + sputter beam and a 25 keV Bi3 + analysis beam, oil-bearing inclusions in different minerals were opened and analysed individually. However, sputtering with a C60 + beam also induced other changes to the mineral surface, such as formation of topographic features and carbon deposition. In this paper, the cause of these changes is explored and the consequences of the sputter-induced features on the analysis of organic phases in natural mineral samples (quartz, calcite and fluorite) in general and fluid inclusions in particular are discussed.The dominating topographical features that were observed when a several micrometers deep crater is sputtered with 10 keV C60 + ions on a natural mineral surface are conical-shaped and ridge-like structures that may rise several micrometers, pointing in the direction of the incident C60 + ion beam, on an otherwise flat crater bottom. The sputter-induced structures were found to appear at places with different chemistry than the host mineral, including other minerals phases and fluid inclusions, while structural defects in the host material, such as polishing marks or scratches, did not necessarily result in sputter-induced structures. The ridge-like structures were often covered by a thick layer of deposited carbon.Despite the appearance of the sputter-induced structures and carbon deposition, most oil-bearing inclusions could successfully be opened and analysed. However, smaller inclusion (<15 μm) could potentially become entirely covered by sputter-resistant structures and therefore difficult to open. Therefore, it might become necessary, to for example increase the ion energy and rotate the stage to successfully open smaller inclusions for analysis.SIMS, C60, carbon deposition, topography, mineral, fluid inclusions, geological samples, depth profiling.
Keywords: SIMS; C60; Carbon deposition; Topography; Mineral; Fluid inclusions; Geological samples; Depth profiling;
Optimum packing density and crystal structure of tin-doped indium oxide thin films for high-temperature annealing processes by Kazuhiro Kato; Hideo Omoto; Takao Tomioka; Atsushi Takamatsu (9207-9212).
► We studied the electrical properties and microstructure of annealed ITO thin films. ► The ITO thin films were deposited by sputtering and annealed after deposition. ► The ITO thin films with high packing density had low-resistivity after annealing. ► The low-resistive ITO thin film came from high Hall mobility. ►The carrier electrons of the films with high packing density can conduct well.The influence of high-temperature annealing on the electrical properties and microstructure of tin-doped indium oxide (ITO) thin films was investigated as a function of oxygen gas flow ratio to argon gas during the sputtering deposition. The ITO thin films were annealed at 500 °C in air after the deposition. It was found that the ITO thin films, which were deposited in relatively low oxygen gas flow ratio, exhibited high Hall mobility and low-resistivity after the annealing. Furthermore, the X-ray reflectivity and diffraction measurement revealed that the ITO thin film with low-resistivity after annealing exhibited high packing density, smooth surface and low crystallization degree. It can be considered that the carrier electron scattering was suppressed with increasing in the packing density of the ITO thin film; as a result, the Hall mobility and resistivity were improved.
Keywords: Annealing; ITO; Packing density; Resistivity; Sputtering; Thin film;
Electrodeposition of high corrosion resistance Cu/Ni–P coating on AZ91D magnesium alloy by Shan Zhang; Fahe Cao; Linrong Chang; JunJun Zheng; Zhao Zhang; Jianqing Zhang; Chunan Cao (9213-9220).
► Ni–P electrodeposition on AZ91D Mg alloy by a Cu pre-plating layer. ► Ni–P electrodeposited AZ91D showed significantly improved corrosion resistance. ► The structure is transformed to amorphous and corrosion resistance increases with P content increasing.High corrosion resistance Cu/Ni–P coatings were electrodeposited on AZ91D magnesium alloy via suitable pretreatments, such as one-step acid pickling-activation, once zinc immersion and environment-friendly electroplated copper as the protective under-layer, which made Ni–P deposit on AZ91D Mg alloy in acid plating baths successfully. The pH value and current density for Ni–P electrodeposition were optimized to obtain high corrosion resistance. With increasing the phosphorous content of the Ni–P coatings, the deposits were found to gradually transform to amorphous structure and the corrosion resistance increased synchronously. The anticorrosion ability of AZ91D Mg alloy was greatly improved by the amorphous Ni–P deposits, which was investigated by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The corrosion current density (I corr ) of the coated Mg alloy substrate is about two orders of magnitude less than that of the uncoated.
Keywords: AZ91D Mg alloy; Electrodeposition; Ni–P; Corrosion resistance;
Characterization and activity of visible-light-driven TiO2 photocatalyst codoped with lanthanum and iodine by Ling Li; Huisheng Zhuang; Dan Bu (9221-9225).
► La/I/TiO2 photocatalyst was synthesized using simple precipitation-dipping method. ► Only diffraction peaks of anatase phase can be discovered from XRD pattern of sample. ► Sample shows drastic and strong photoabsorption in the 400–800 nm wavelength range. ► La/I/TiO2 displays a higher photocatalytic activity than the P25 and monodoped TiO2. ► Work are helpful in treatment dye pollutants under simulated sunlight irradiation.The novel visible-light-activated La/I/TiO2 nanocomposition photocatalyst was successfully synthesized using precipitation-dipping method, and characterized by X-ray powder diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), thermogravimetry-differential scanning calorimetry (TG–DSC) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity of La/I/TiO2 was evaluated by studying photodegradation of reactive blue 19 as a probe reaction under simulated sunlight irradiation. Photocatalytic experiment results showed that the maximum specific photocatalytic activity of the La/I/TiO2 photocatalyst appeared when the molar ratio of La/Ti was 2.0 at%, calcined at 350 °C for 2 h, due to the sample with good crystallization, high BET surface area and small crystal size. Under simulated sunlight irradiation, the degradation of reactive blue 19 aqueous solution reached 98.6% in 80 min, which showed La/I/TiO2 photocatalyst to be much higher photocatalytic activity compared to standard Degussa P25 photocatalyst. The higher visible light activity is due to the codoping of lanthanum and iodine.
Keywords: Photocatalysis; La/I/TiO2; Simulated sunlight; Reactive blue 19;
Preparation and photocatalytic property of CeO2 lamellar by Fengjuan Chen; Yali Cao; Dianzeng Jia (9226-9231).
► A novel one-step solid-state chemical synthesis was used to prepare CeO2 lamellar. ► The photocatalytic results indicated that CeO2 had high photocatalytic activity. ► The effects of important operational parameters were also investigated. ► The results revealed that CeO2 can be used as a potential photocatalyst.A novel room temperature solid-state chemical synthesis was introduced to successfully fabricate CeO2 samples, coupled by a polyethylene glycol 400 (PEG 400)/cetyl trimethylammonium bromide (CTAB)/sodium dodecyl sulfate (SDS). The as-prepared products were characterized by XRD, TEM, SEM, BET and UV. A study of photocatalytic degradation of the methylene blue MB under UV illumination has been carried out. It is indicated that the samples exhibit excellent photocatalytic activity. Besides, the samples assisted with surfactants possess higher photocatalytic activity than the sample without any surfactants, wherein the sample with SDS as an additive shows the highest photocatalytic activity, which is able to reach 89.6% MB degradation ratio within 60 min illumination. Moreover, the effects of important operational parameters such as initial MB concentration, catalyst loading and pH were also investigated. The above sample under the optimum conditions obtained the maximum MB degradation ratio up to 96.5%, which is higher than that of the commercial TiO2 P25 under the same conditions. It can be concluded that CeO2 will be a potential photocatalyst in the application of organic pollutant.
Keywords: CeO2; Photoactivity; Solid-state chemical synthesis;