Applied Surface Science (v.258, #16)
Immobilization of Chlorosulfonyl-Calixarene onto the surface of silica gel through the directly estrification by Saeed Taghvaei-Ganjali; Reza Zadmard; Mandana Saber-Tehrani (5925-5932).
► Chemically bonded 25,26,27,28-tetrakis[chlorosulfonyl]calixarene to silica gel through the directly estrification. ► Sample characterization with elemental analysis, FTIR-spectroscopy, SEM, EDAX, XRD, TGA, 29Si CP/MAS spectroscopy and acid–base titration. ► Successful incorporation of organic group via covalent bond.For the first time Chlorosulfonyl-Calixarene has been chemically bonded to silica gel through the directly estrification without silane coupling agent to prepare Chlorosulfonyl-Calixarene-bonded silica gel. Sample characterization was performed by various techniques such as elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), powder X-ray diffraction (XRD), N2 adsorption–desorption, thermal gravimetric analysis (TGA), 29Si CP/MAS spectroscopy and acid–base titration. All data approve the successful incorporation of organic group via covalent bond. From the comparison between sulfur content determined by elemental analysis and the number of H+ determined by acid–base titration, it was shown that two ester units took place onto the new synthesized sample and two acidic sites exist on the surface.
Keywords: Silica gel; Immobilization; Chlorosulfonyl-Calixarene; Estrification;
Fabrication of nano-structured super-hydrophobic film on aluminum by controllable immersing method by Ruomei Wu; Shuquan Liang; Anqiang Pan; Zhiqing Yuan; Yan Tang; Xiaoping Tan; Dikai Guan; Ya Yu (5933-5937).
► Acetic acid, hydrochloric acid and oxalic acid as etching solution. ► Aluminum alloy plates were immersing in four different formula acid solutions for some hours at ambient temperature respectively. ► The surfaces were configured in a labyrinth structure with convexity and caves of micro-nanostructure. ► The surface had better faces and process stability by disposal of two acids immersing.Aluminum alloy surface can be etched easily in acid environment, but the microstructure of alloy surface hardly meets the customers’ demand. In this work, a facile acidic-assistant surface oxidation technique has been employed to form reproducible super-hydrophobic surfaces on aluminum alloy plates. The samples immersed in three different acid solutions at ambient temperatures are studied and the results demonstrated that the aqueous mixture solution of oxalic acid and hydrochloric is easier to produce better faces and better stability. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectrometer, X-ray photoelectron spectroscopy (XPS) and water contact angle measurement are used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on aluminum substrates. The surfaces, configured of a labyrinth structure with convexity and concavity, are in different roughness and gloss because of the different recipe acid solutions used. Better roughness of the surface can be obtained by adjusting the concentration of Clˉ and oxalate ions in acid solutions. The present research work provides a new strategy for the controllable preparation super-hydrophobic films of general materials on aluminum alloy for practical industrial applications.
Keywords: Super-hydrophobic; Aluminum alloy; Sanding; Chemical etching; Contact angle;
Li4Ti5O12-coated graphite as an anode material for lithium-ion batteries by Meng-Lun Lee; Yu-Han Li; Shih-Chieh Liao; Jing-Ming Chen; Jien-Wei Yeh; Han C. Shih (5938-5942).
► The Li4Ti5O12 coated carbon (MCMB–LTO) is successfully prepared via sol–gel process. ► The core-shelled MCMB–LTO works as anode in Li-ion batteries. ► MCMB–LTO shows good C-rate tolerance and cycle life capability in the batteries. ► LTO coated carbon shows smaller resistance than controlled one after cycling.In this study, we have synthesized and characterized Li4Ti5O12 (LTO)-coated meso-carbon micro beads (MCMB) as an anode material for Li-batteries. The surface of MCMB powders was uniformly coated by the LTO nanoparticles to form a core–shell structure via a sol–gel process, followed by calcination. The average size of MCMB core was 20 μm while the thickness of LTO shell was 80–120 nm. We found that LTO-coated MCMB has better rate-capability and cycle life, compared with the pristine MCMB. Electrochemical impedance spectroscopy (EIS) results showed that after 40 cycles, the cell resistance of the LTO-coated MCMB electrode increased slightly, while that of the pristine MCMB electrode increased significantly. The enhanced performance of the LTO-coated MCMB electrode is attributed to the LTO coating, which suppresses the increase in the charge-transfer resistance during prolonged cycle.
Keywords: Lithium-ion battery; Graphite; MCMB; Li4Ti5O12;
Deposition Ga-doped ZnO films on PEN substrate at room temperature for thin film silicon solar cells by Ke Tao; Yun Sun; Hongkun Cai; Dexian Zhang; Ke Xie; Yuan Wang (5943-5946).
► The stress of ZnO:Ga films prepared on PEN was smaller than that of samples on glass. ► The transmittance of sample on PEN was larger than that of samples on glass. ► The best electrical property of ZnO:Ga was obtained with DBSP at 14 mm. ► The efficiency of flexible a-Si:H solar cells prepared at 150 °C was 5.91%.ZnO:Ga thin films were deposited by DC magnetron sputtering using two facing Ga-doped ZnO ceramic targets at room temperature. Polyethylene naphthalate (PEN) and Eagle2000 glass were used as substrates. The influence of PEN and glass substrates on the properties of ZnO:Ga thin films has been investigated. The distance between substrate and plasma dependence of micro-structure and electrical properties was also studied. The lowest resistivity obtained was 6.65 × 10−4 Ω cm with a Hall mobility of 17.1 cm2 V−1 s−1 and a carrier concentration of 5.5 × 1020 cm−3. When those ZnO:Ga thin films were applied to low-temperature flexible a-Si:H solar cells, an initial conversion efficiency of 5.91% was achieved.
Keywords: Ga-doped zinc oxide; Transparent conducting oxides; Magnetron sputtering; PEN; Solar cells;
Construction of heparinylated multilayer films on Ti―O via streptavidin/biotin interaction by Y.J. Weng; F.J. Jing; J.Y. Chen; N. Huang (5947-5954).
. Schematic figures of layer-by-layer assembling of streptavidin and biotinylated heparin.Display Omitted► Heparinylated multilayer films was constructed on Ti―O. ► A desired heparinylated multilayer can be obtained through layer-by-layer driven by streptavidin/biotin interaction. ► The heparinylated multilayer coated Ti―O has improved anticoagulation properties.Construction of heparinylated multilayer films on Ti―O via streptavidin/biotin interaction was conducted in the present study. An organic layer of 3-aminopropylphosphonic acid (APP) was first introduced on Ti―O by self-assembling, and then biotin was immobilized by photochemical methods. So streptavidin and biotinylated heparin were assembling through biorecognition, and a desired 6-layer heparinylated multilayer was obtained through layer-by-layer driven by streptavidin/biotin interaction. The in vitro platelet adhesion and activation were investigated by a static platelet adhesion test. The clotting time was examined by activated partial thromboplastin time (APTT). Results show that the heparinylated multilayer coated Ti―O can significantly decrease platelet adhesion and activation, and prolong clotting time of APTT compared to untreated Ti―O, which indicates the heparinylated multilayer coated Ti―O displays more excellent anticoagulation performance than that of the bare Ti―O.
Keywords: Heparinylated multilayer; Streptavidin/biotin interaction; Ti―O; Hemocompatibility;
Synthesize of Cu2O-CuO/Sr3BiO5.4 and its photocatalytic activity by Wei Zhao; Kin-Hang Wong; Chun Hu; Jimmy C. Yu; Chiu-Yeung Chan; Tao Qi; Po-Keung Wong (5955-5959).
Display Omitted► A visible-light-driven photocatalyst, Cu2O-CuO/Sr3BiO5.4, was synthesized under an acidic system using basic ethylenediamine tetraacetic acid disodium salt. (Na2EDTA) as buffer reagent ► Part of Cu2O was formed on the surface of Sr3BiO5.4 in situ during the calcination. ► 5.4 log inactivation of Escherichia coli K-12 and 27% degradation of naphthalene were achieved in 3 and 2 h, respectively, under the visible light irradiation provided by fluorescent lamps.A visible-light-driven photocatalyst, Cu2O-CuO/Sr3BiO5.4, was synthesized by the precipitation method using a new acidic system with basic ethylenediamine tetraacetic acid disodium salt (Na2EDTA) as the buffer reagent. Part of Cu2O was formed on the surface of Sr3BiO5.4 in situ during the calcination. 5.4 log inactivation of Escherichia coli K-12 and 27% degradation of naphthalene were achieved in 3 and 2 h, respectively, under the visible light irradiation provided by fluorescent lamps. The results of this study suggested that Cu2O-CuO on the surface of Sr3BiO5.4 is stable and can effectively promote the visible light photocatalytic activity of Sr3BiO5.4.
Keywords: Photocatalysts; Visible light; Copper; Disinfection; Degradation;
Preparation and properties of chrome-free colored Ti/Zr based conversion coating on aluminum alloy by AiHua Yi; WenFang Li; Jun Du; SongLin Mu (5960-5964).
Display Omitted► A golden conversion coating has been prepared by adding tannic acid in the treatment solution. ► The conversion coating owns a double-layer structure. ► The outer layer consists of metal–organic complex and the inner layer is mainly made up of Na3AlF6. ► The mechanism of the formation of the golden conversion coating can be deemed as nucleation, growth of Na3AlF6 crystal and formation of metal–organic complex.A golden conversion coating on the surface of aluminum alloy was prepared by adding tannic acid and coating–forming accelerator in the treatment solution containing titanium and zirconium ions. The growth process, main component and corrosion resistance of the conversion coating were characterized by EDS, SEM, XRD, XPS, FIIR and electrochemical workstation. The results showed that the main components of the conversion coating were Na3AlF6 and the conversion coating owns a double-layer structure. The outer layer consists of metal–organic complex and the inner layer is mainly made up of Na3AlF6. The mechanism of the formation of the golden conversion coating can be deemed as nucleation, growth of Na3AlF6 crystal and formation of metal–organic complex. In potentiodynamic polarization test, the corrosion current density decreases to 0.283 μA cm−2 from 5.894 μA cm−2, which indicates an obvious improvement of corrosion resistance.
Keywords: Conversion coating; Aluminum alloy; Tannic acid; Corrosion resistance;
New cleaning strategies based on carbon nanomaterials applied to the deteriorated marble surfaces: A comparative study with enzyme based treatments by Federica Valentini; Alessia Diamanti; M. Carbone; E.M. Bauer; Giuseppe Palleschi (5965-5980).
► Nanotechnologies for cleaning. ► Bio-cleaning. ► Analytical diagnosis. ► Deteriorated marble surfaces. ► Black crust and bio-patina. Pentelic marbles from Basilica Neptuni in Rome-Italy (27–25 b.c.) show the signs of deterioration phenomena, which can be identified as black crust as well as black and grey patina. The present study has the twofold objective of assessing the entity of the deterioration and proposing new cleaning strategies based on nanotechnologies. The former is achieved by performing optical microscopy, differential interference contrast (DIC), stereomicroscopy, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and infrared Fourier transform spectroscopy (FT-IR) analysis. The second objective of this study, involves different treatments based on a new cleaning strategy with carbon nanomaterials and bio-cleaning (used here for comparison) performed with enzymes, as glucose oxidase (GOD) and lipase. Nanomicelles assembled with functionalised carbon nano-fibres (CNF-COOH) and dispersed in Tween 20 medium show the highest cleaning performances in terms of removal of the black crust, compared with the pristine single-wall carbon nanotubes (SWCNTs) and the enzyme-based cleaning treatments. In particular, in these last two cases, the GOD-based biocleaning is efficient in removing the grey and dark patina, but works slow on the black crust. Finally, the lipase based cleaning approach is efficient in the black patina removal, though at the working temperature of 38 °C.
Keywords: Marble samples; Black crust; Dark patina; Grey patina; Bio-deterioration; Cleaning technologies; Nanomicelles; Functionalised carbon nanomaterial; Enzymes;
The influence of annealing atmosphere on the material properties of sol–gel derived SnO2:Sb films before and after annealing by Jiann-Shing Jeng (5981-5986).
Display Omitted► Material properties of the SnO2 films with different Sb contents were investigated before and after annealing under O2 or N2. ► The SnO2 films incorporating Sb can withstand higher temperatures to prevent void formation than SnO2 films without adding Sb. ► After doping with Sb, the resistivity of SnO2 films after annealing in O2 is greater than that of N2-annealed SnO2 films. ► The XRD results indicate that an O2 atmosphere can enhance the precipitation of SnO2 phase in comparison with N2 ambient. ► The main difference between N2-annealed and O2-annealed effects on SnO2 films is the degree of phase transformations.SnO2 films with and without Sb doping were prepared by the sol–gel spin-coating method. Material properties of the SnO2 films with different Sb contents were investigated before and after annealing under O2 or N2. When SnO2 films are annealed under N2 or O2, the resistivity decreases with increasing annealing temperature, which may be related to the increased crystallinity and reduced film defects. The intensity of SnO2 peaks for both O2- and N2-annealed films increases as the annealing temperature increases. Small nodules are revealed on the surface of SnO2 films after annealing in N2 or O2 atmospheres, and some voids are present on the surface of N2-annealed SnO2 films. After doping with Sb, the resistivity of SnO2 films after annealing in O2 is greater than that of N2-annealed SnO2 films. The surface morphology of SnO2 films incorporating different molar ratios of Sb after annealing are similar to that of as-spun SnO2 films with adding Sb. There were no voids found on the surfaces of N2-annealed SnO2:Sb films. In addition, the peak intensity of SnO2:Sb films after O2-annealing is higher than those films after N2-annealing. The chemical binding states and Hall mobility of the high-temperature annealed SnO2 films without and with adding Sb are also related to the annealing atmospheres. This study discusses the connection among the material properties of the SnO2 films with different Sb contents and how these properties are influenced by the Sb-doping concentration and the annealing atmospheres of SnO2 films.
Keywords: Sol–gel; SnO2:Sb; Resistivity; Mobility;
A study of high-quality freestanding diamond films grown by MPCVD by Ming Q. Ding; Lili Li; Jinjun Feng (5987-5991).
The fabrication process of high-quality freestanding diamond films grown by Microwave Plasma Chemical Vapor Deposition (MPCVD) was studied. Under the optimal condition, freestanding diamond films 55 mm in diameter with a thickness up to 1 mm were fabricated, showing an excellent crystalline structure as examined from Raman and X-Ray Diffraction (XRD) spectra. For most processing conditions, including substrate temperatures varied from 800 to 1050 °C, the films were found in a [1 1 1] preferential texture, whereas [2 2 0] and [0 0 1] film textures occurred in some special cases. Optical measurements of one side polished diamond films showed a cutoff wavelength 225 nm, and a transmission ≥70% at λ ≥ 2.5 μm.
Keywords: Microwave Plasma Chemical Vapor Deposition; Freestanding diamond films; Texture; Optical transmission;
Preparation and characterization of ZnS:Fe/MX (M = Cd, Zn; X = S, Se) core–shell nanocrystals by Lihua Li; Ruishi Xie; Yongjun Gu; Jinliang Huang; Jianguo Zhu (5992-5995).
► It was found that the surface state of nanocrystals is an important issue for the luminescent properties of nanocrystals. ► Several core/shell nanocrystals, such as CdSe/ZnS, and CdSe/CdTe/ZnSe have been shown to have much higher quantum efficiencies than that of the unpassivated ones. ► In this work, the ZnS:Fe/MX (M = Cd, Zn; X = S, Se) core–shell nanocrystals were prepared by chemical precipitation method, the structure and photoluminescence properties of ZnS:Fe/MX (M = Cd, Zn; X = S, Se) core/cell nanocrystals were studied.ZnS:Fe/MX (M = Cd, Zn; X = S, Se) nanocrystals were synthesized by chemical precipitation method. Compared to ZnS:Fe nanocrystals, the diffraction peaks intensity of ZnS:Fe/ZnS nanocrystals reduced and the diffraction peaks of ZnS:Fe/ZnSe nanocrystals moved to lower angles. TEM photos show that ZnS:Fe and ZnS:Fe/ZnSe nanocrystals are spheroidal and the average particles size is about 2–4 nm. The selected-area electron diffraction pattern of ZnS:Fe/ZnSe nanocrystals shows the diffraction rings, indicating the ZnS:Fe/ZnSe nanocrystals have a polycrystalline structure. XPS shows that the divalent and trivalent of Fe ion are coexisted in ZnS:Fe nanocrystals. The emission peaks of ZnS:Fe nanocrystals were from S and Zn ions vacancy defects and surface defects for the range of 200–900 nm. The use of ZnS (CdS, ZnSe) as surface modifying reagent inhibited the luminescent intensity of ZnS:Fe nanocrystallines at 420 nm. The PL spectra of ZnS:Fe/CdS nanocrystals show a new peak at 554 nm.
Keywords: ZnS:Fe/MX nanocrystals; Chemical precipitation method; Luminescent properties;
Microstructure and characterization of Al-doped ZnO films prepared by RF power sputtering on Al and ZnO targets by Chun-An Tseng; Jing-Chie Lin; Yu-Fong Chang; San-Der Chyou; Kun-Cheng Peng (5996-6002).
► AZO films were prepared using a RF power applied on the Al-target. ► We estimate the energy gaps of AZO films by subtracting the cut off values from UPS. ► We discuss the dependence of the electrical resistivity on the microstructure by HRTEM. ► The stacking faults induced by Al-doped provide another path for electron transfer. ► Increasing Al-dopant concentration will decrease the electrical resistivity of the films.Al-doped zinc oxide (AZO) transparent conductive films were prepared on a glass substrate using a magnetron sputtering system with a pure zinc oxide (ZnO) target and a pure Al target sputtered using radio frequency (RF) power. The RF power was set at 100 W for the ZnO target and varied from 20 to 150 W for the Al target. The morphology of the thin films was examined by field-emission scanning electron microscope (FE-SEM), and their composition was analyzed by the equipped energy-dispersive X-ray spectroscopy (EDS). The cross section of the films determined through FE-SEM indicated that their thickness was around 650 nm. EDS analysis revealed that the Al-dopant concentration of the AZO films increased in the following order: 0.85 at.% (20 W) < 1.60 at.% (40 W) < 3.52 at.% (100 W) < 4.34 at.% (150 W). Analysis of the films using X-ray diffractometer (XRD) indicated that all films had a wurtzite structure with a texture of (0 0 2). High-resolution transmission electron microscopy (HRTEM) revealed a number of defects in the films, such as stacking faults and dislocations. Ultraviolet photoelectron spectroscopy (UPS) was used to estimate the optical energy gap (E g ) for the AZO thin films. The energy gap increases from 3.39 to 3.58 eV as the RF power applied to the Al target increase. The electrical resistivity of the films decreased from 3.43 × 10−2 Ω cm to 3.29 × 10−3 Ω cm as the RF power increased from 20 to 150 W when a four-point probe was used to investigate. Atomic force microscope (AFM) revealed that the surface roughness of the films increased with increasing RF power. The average optical transmittance of the films was determined by UV–visible spectrometer. The films are suitable for use as transparent conductive oxide films in the optoelectronic industry. A decrease in the electrical resistivity of the film with increasing Al-dopant concentration was ascribed to an increase in the carrier concentration and density of stacking faults in the films.
Keywords: Magnetron sputtering; Radio frequency; AZO films; UPS; HRTEM;
Low-temperature preparation of polycrystalline germanium thin films by Al-induced crystallization by Shanglong Peng; Duokai Hu; Deyan He (6003-6006).
► The Al-induced layer exchange significantly promotes the crystallization of the a-Ge:H thin films at 250 °C. ► The AFM images present a random and uniform distribution of Ge nanocones for annealed samples, which is caused by the introduction of the Al layer. ► The Ge–Ge phonon modes shift to lower frequency and the FWHM of the Ge Raman peaks decreases with increasing the annealing temperature. ► The sheet resistance decreases with increasing the annealing temperature, which is due to a reduction in the amount of dangling bonds and defects in the crystallized Ge films.Low-temperature Al-induced crystallization of hydrogenated amorphous Ge films has been investigated by X-ray diffraction, Raman spectra, scanning electron microscopy, atomic force microscopy and sheet resistance measurements using a four-point probe. By investigation of the influence of the annealing temperature on the microstructures, morphologies and electrical properties of the Ge thin films. It can be seen that the Al-induced layer exchange significantly promotes the crystallization of the amorphous Ge thin films at 250 °C. And there is an enhancement in film crystallinity and grain size with the increasing of the annealing temperature. Also, it can be seen that the crystallized films have the rough surface. The low-frequency shifts of Ge–Ge TO peaks were found with the increasing of the annealing temperature. In addition, the sheet resistance was decreased significantly with the increasing of the grain size. The minimum resistance of 213 Ω/□ in poly-Ge thin film was obtained after annealing at 350 °C for 3 h.
Keywords: Ge films; Al-induced crystallization; Raman spectra;
Lithographically patterned silicon nanostructures on silicon substrates by Nacéra Megouda; Gaëlle Piret; Elisabeth Galopin; Yannick Coffinier; Toufik Hadjersi; Omar Elkechai; Rabah Boukherroub (6007-6012).
► A simple technique to generate silicon patterned nanostructures by the combination of optical lithography and metal-assisted chemical etching was reported. ► A 20 nm-thick gold film was deposited onto silicon substrate on which the patterns were transferred using standard photolithography. ► It was demonstrated that for low resistive (0.01 Ω cm) silicon, nanowires of different heights are formed in Au-coated and uncoated areas after etching in 7 M HF/0.02 M AgNO3. ► For highly resistive silicon (5–10 Ω cm), nanowires are formed only in Au-uncoated regions.The paper reports on controlled formation of silicon nanostructures patterns by the combination of optical lithography and metal-assisted chemical dissolution of crystalline silicon. First, a 20 nm-thick gold film was deposited onto hydrogen-terminated silicon substrate by thermal evaporation. Gold patterns (50 μm × 50 μm spaced by 20 μm) were transferred onto the silicon wafer by means of photolithography. The etching process of crystalline silicon in HF/AgNO3 aqueous solution was studied as a function of the silicon resistivity, etching time and temperature. Controlled formation of silicon nanowire arrays in the unprotected areas was demonstrated for highly resistive silicon substrate, while silicon etching was observed on both gold protected and unprotected areas for moderately doped silicon. The resulting layers were characterized using scanning electron microscopy (SEM).
Keywords: Silicon nanostructures; Silicon nanowires; Electroless etching; Optical lithography; Patterning;
Friction behavior of in situ hydrothermal fabrication of sulfide film on copper by Yong Wan; Yinhu Wang; Zhen Xu; Jibin Pu; Caixia Qi (6013-6017).
► Cu2S films on copper are prepared through the hydrothermal reaction. ► Cu2S films have the water contact angle of 140° without any chemical modification. ► Cu2S films possess low friction with extremely long duration.Cu2S films on the copper substrate are successfully prepared through the in-situ hydrothermal reaction between sulfur powder and copper foil. The morphological and chemical structures of films were investigated by using scanning electron microscopy and X-ray photoelectron spectroscopy. The friction-reducing performance of Cu2S film obtained was evaluated in dry sliding contact with steel ball. It is observed that as-obtained Cu2S films have the water contact angle as high as 140° without any chemical modification, possessing low friction with extremely long duration.
Keywords: Thin films; Copper sulfide; Hydrothermal; Friction;
Study of thermal stability of ZnO:B films grown by LPCVD technique by H. Zhu; H. Jia; D. Liu; Y. Feng; L. Zhang; B. Lai; T. He; Y. Ma; Y. Wang; J. Yin; Y. Huang; Y. Mai (6018-6023).
► Thermal stability of ZnO:B films with different doping level and thickness grown by LPCVD technique are investigated. ► Total transmission of the films at near infrared wavelength range increases with the enhanced thermal treating intensity. ► Morphology of the ZnO:B films does not change after the thermal treatment. ► Film resistivity increases with increasing treating duration for the ZnO:B films. ► Chemisorption of oxygen into ZnO films is responsible for the decrease of carrier concentration after the heat treatment.Zinc oxide thin films with different boron doping levels (ZnO:B) are prepared by low pressure chemical vapor deposition (LPCVD) technique. All films here exhibit a pyramid-like surface texture. Stability of the ZnO:B films is systematically investigated through a post heat treatment at ambient temperatures of 300 °C and 250 °C for different durations. It is found that total transmission (TT) of these films at near infrared (NIR) wavelength range increases with the enhanced thermal treating intensity, which could be attributed to decrease of free carrier concentration inside the films. Moreover, light absorption in NIR wavelength range decreases profoundly with the increasing carrier concentration after a post thermal treatment in particular for highly doped ZnO:B films. However, morphology of these ZnO:B films does not vary after the thermal treatment and thus the corresponding light scattering properties do not change as well. Therefore, the thermally treated ZnO:B films may lead to an increase in light-generated current and resulting a higher cell efficiency due to the enhancement of TT when they work as front contact in silicon thin film solar cells.
Keywords: ZnO:B; LPCVD; Light trapping; Near infrared;
Spray-gun deposition of catalyst for large area and versatile synthesis of carbon nanotubes by A. Gohier; K.-H. Kim; E.D. Norman; L. Gorintin; P. Bondavalli; C.S. Cojocaru (6024-6028).
► Iron chloride deposited as catalyst precursor by spray gun technique. ► Large area synthesis of carbon nanotubes arrays from as sprayed catalyst. ► Synthesis of single walled carbon nanotubes network from as sprayed catalyst. ► Thin-film transistor s obtained using as grown carbon nanotube network.Spray gun deposition technique was investigated for large area deposition of nano-catalysts. In particular, we studied iron chloride salts solutions as catalyst precursor for the synthesis of carbon nanotubes (CNTs). Iron chloride salts are shown to decompose upon thermal annealing into Fe(III) oxide based species that make it suitable for further growth of various carbon nanotube structures. Depending on the spraying process, versatile synthesis of 2-D single-walled carbon nanotube network as well as vertically aligned carbon nanotubes arrays on functional substrates can be achieved. Such simple process for the preparation of CNT-based architecture opens new perspectives in the field of thin-film transistor and nanostructured electrodes.
Keywords: Vertically aligned carbon nanotubes; Single walled carbon nanotube network; Spray gun deposition; Iron chloride; Thin film transistor;
Composite photocatalyst containing Eosin Y and multiwalled carbon nanotubes loaded with CuO/NiO: Mixed metal oxide as an active center of H2 evolution from water by Shi-Zhao Kang; Lili Chen; Xiangqing Li; Jin Mu (6029-6033).
► CuO/NiO mixed metal oxide is an active center of H2 evolution from water. ► High photocatalytic activity may be from the synergistic effect between CuO and NiO. ► The interface between CuO particles and NiO particles plays an important role.A composite photocatalyst containing Eosin Y as a sensitizer, multiwalled carbon nanotubes as a supporter material or electron transfer channel, and CuO/NiO as an active center of H2 evolution from water was fabricated and characterized with X-ray photoelectron spectroscopy and transmission electron microscope. Meanwhile, photocatalytic hydrogen evolution from water over this catalyst was explored using triethanolamine as a sacrificial reagent under visible irradiation. A rate of H2 evolution of approximately 1.0 mmol g−1 h−1 was achieved under optimal conditions. Furthermore, for practical purposes, the photocatalytic hydrogen evolution was studied as a function of content of CuO/NiO, mass ratio of CuO to NiO, pH of solution, concentration of triethanolamine and dosage of Eosin Y, respectively. The results show that mixed metal oxides are a kind of promising active centers of H2 evolution from water in the photocatalytic system studied.
Keywords: Composite photocatalyst; Mixed metal oxide; Carbon nanotubes; Dye; H2 evolution;
Study of the surface modification with oleic acid of nanosized HfO2 synthesized by the polymerized complex derived sol–gel method by R. Ramos-González; L.A. García-Cerda; M.A. Quevedo-López (6034-6039).
Display Omitted► Synthesis and characterization of nanosized HfO2 by the polymerized complex derived sol–gel method. ► The HfO2 nanoparticles were coated with oleic acid. ► The minimum concentration of oleic acid necessary to cover HfO2 particles was determined. ► The oleic acid was chemisorbed as a carboxylate onto the HfO2 nanoparticle surface. ► The surface properties of HfO2 modified with oleic acid changed from hydrophilic to hydrophobic.The synthesis of nanosized hafnium oxide by the polymerized complex derived sol–gel method is reported. The structural and morphological characterization of the HfO2 was carried out by X-ray diffraction and scanning electron microscopy. The surface of hafnium oxide nanoparticles was modified by capping with oleic acid. The nanoparticle surface area was measured by the gas adsorption technique in order to determine the minimal amount of oleic acid needed to obtain a uniform coverage of the hafnium oxide. The existence of organic layer can be confirmed by Fourier transform spectroscopy, solid state nuclear magnetic resonance spectroscopy, thermal gravimetric analysis and transmission electron microscopy. The FTIR and solid state NMR results reveal that oleic acid is chemisorbed as a carboxylate onto the HfO2 nanoparticle surface and confirm the formation of a monomolecular layer of oleic acid surrounding the HfO2. The cover density of oleic acid on the HfO2 increases with the amount of oleic acid used to modify the nanoparticles and the surface properties of HfO2 nanoparticles modified with oleic acid change from hydrophilic to hydrophobic.
Keywords: Hafnium oxide (HfO2); Nanoparticles; Surface modification; Oleic acid; Lipophilic degree;
Immobilization of acetylcholinesterase via biocompatible interface of silk fibroin for detection of organophosphate and carbamate pesticides by Rui Xue; Tian-Fang Kang; Li-Ping Lu; Shui-Yuan Cheng (6040-6045).
An amperometric biosensor for the detection of organophosphate and carbamate pesticides was prepared by regenerated silk fibroin (SF) matrix non-covalent adsorption acetylcholinesteras (AChE) onto glassy carbon electrode modified with multiwall carbon nanotubes. AChE not only can be immobilized steadily on the SF matrix, but also the bioactivity of immobilizing AChE can be preserved effectively.Display Omitted► Silk fibroin was applied as a biocompatible interface to immobilize acetylcholinesterase. ► Silk fibroin and multiwall carbon nanotubes were used to modify glassy carbon electrode. ► Pesticides were detected by this biosensor with a detection limit of 5.0 × 10−7 M and 6.0 × 10−8 M.An amperometric biosensor for the detection of organophosphate and carbamate pesticides was developed based on the immobilization of acetylcholinesterase (AChE) on regenerated silk fibroin (SF) matrix by non-covalent adsorption. SF and AChE were coated sequentially on the surface of the glassy carbon electrode (GCE) which was modified with multiwall carbon nanotube (MWNTs). The obtained biosensor was denoted as AChE–SF/MWNTs/GCE. The atomic force microscopy images showed that the SF matrix provided a more homogeneous interface for the AChE immobilization. The aggregation of immobilizing AChE was therefore avoided. The cyclic voltammogram of thiocholine at this biosensor exhibited a well defined oxidation peak at 0.667 V (vs. SCE). The inhibition rate of methyl parathion to the immobilized AChE was proportional to the logarithm of the concentration of methyl parathion over the range of the concentration of methyl parathion from 3.5 × 10−6 to 2.0 × 10−3 M with a detection limit of 5.0 × 10−7 M. Similarly, the linearly response range of carbaryl was from 1.0 × 10−7 to 3.0 × 10−5 M with a detection limit of 6.0 × 10−8 M. The experimental results indicate that AChE not only can be immobilized steadily on the SF matrix, but also the bioactivity of immobilizing AChE can be preserved effectively.
Keywords: Biosensor; Acetylcholinesterase; Silk fibroin; Multiwall carbon nanotube;
Influence of growth temperature and deposition duration on the structure, surface morphology and optical properties of InN/YSZ (1 0 0) by N.C. Zoita; C.E.A. Grigorescu (6046-6051).
► InN/YSZ (1 0 0) films grown by the reactive RF-magnetron sputtering technique. ► Film texture and surface roughness change with growth time and substrate temperature. ► 3D pyramidal islands developed on top of the films. ► Photoluminescence peak redshift with increasing film thickness and growth temperature.InN films with the wurtzite structure have been grown directly on YSZ (1 0 0) substrate by the RF-magnetron sputtering technique. Strongly (0 0 2) oriented films with smooth surfaces (0.7–2.9 nm surface roughness depending on substrate temperature), were grown within 30 min. Films deposited for 60 min developed three-dimensional (3D) pyramidal islands on top of their surfaces, which diminished the residual elastic strain. The optical absorption edge and PL peak energy around 1.7 eV were found to redshift with increasing film thickness and substrate temperature.
Keywords: Indium nitride; YSZ (1 0 0); Reactive magnetron sputtering; Growth temperature; Deposition duration; Crystalline structure; Surface morphology; Band-gap;
Angle resolved XPS studies on an anodic oxide formed on Ti–Nb–Sn alloy and the photo-induced change in carbon contaminants adsorbed on its surface by Naofumi Ohtsu; Naoya Masahashi; Yoshiteru Mizukoshi (6052-6055).
► Anodic oxide formed on a Ti–Nb–Sn alloy was analyzed by angle-resolved XPS. ► The uppermost surface contained higher concentrations of Nb2O5 and SnO2. ► The hydrocarbon adsorbed on the surface is drastically reduced when UV light is illuminated onto the oxide.Anodic oxide formed on a Ti–Nb–Sn alloy was analyzed by angle-resolved X-ray photoelectron spectroscopy (XPS) to determine the chemical state and composition of the uppermost surface. The anodic oxide formed on the alloy consisted of TiO2, SnO2, and Nb2O. The cationic fractions of Nb2O5 and SnO2 were lower than the atomic fractions of Nb and Sn in the alloy, and the uppermost surface contained higher concentrations of these oxides. The photo-induced change in the amount of carbon contaminants adsorbed on its surface was also analyzed by XPS combined with in situ ultraviolet (UV) light illumination. The variations in the chemical state induced by the UV light illumination were consistent with those on monolithic TiO2.
Keywords: XPS; TiO2; Photocatalysis; Anodic oxidation;
Immobilization of streptavidin on 4H–SiC for biosensor development by Elissa H. Williams; Albert V. Davydov; Abhishek Motayed; Siddarth G. Sundaresan; Peter Bocchini; Lee J. Richter; Gheorghe Stan; Kristen Steffens; Rebecca Zangmeister; John A. Schreifels; Mulpuri V. Rao (6056-6063).
Display Omitted► Demonstrated specific and selective protein attachment on the SiC surface. ► APTES-on-SiC thickness is critical for biotinylation and protein immobilization steps. ► Biotinylation of the SiC surface eliminates non-specific protein attachment.A sequential layer formation chemistry is demonstrated for the functionalization of silicon carbide (SiC) appropriate to biosensing applications. (0 0 0 1) 4H–SiC was functionalized with 3-aminopropyltriethoxysilane (APTES) and subsequently biotinylated for the selective immobilization of streptavidin. Atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, fluorescence microscopy, and contact angle measurements were utilized to determine the structure, thickness, wettability, and reactivity of the resulting surface after each functionalization step. Optimization of the APTES layer was found to be critical to the success of the subsequent steps; multilayer, polymeric films resulted in irreproducible behavior. It was shown that there was significant non-specific (electrostatic) binding of streptavidin to APTES functionalized SiC, thus revealing the importance of a uniform biotinylation step prior to streptavidin attachment. The experimental results demonstrate that the APTES functionalized and biotinylated SiC surface has the potential to be employed as a biosensing platform for the selective detection of streptavidin molecules.
Keywords: 4H–SiC; 3-Aminopropyltriethoxysilane; Biotin; Streptavidin; Bioconjugation; Surface functionalization;
Facile synthesis of Cu31S16 and their photocatalytic property by Xueqin Liu; Zhen Li; Fei Li; Qiang Zhang (6064-6068).
► One-step synthetic route under ultrasound irradiation for the first time. ► Structure and optical properties of octahedral Cu31S16. ► High photocatalytic activity. ► Extend to the preparation of other metal chalcogenides.Octahedral Cu31S16 was synthesized by one-step reaction between Cu2O octahedra and thiourea solution under ultrasonic irradiation. Cu2O octahedra acted as both the precursor and template for the preparation of octahedral Cu31S16. This method has the advantages of the simplicity and low cost. The Cu31S16 nanoparticles exhibit a perfect highly ordered, uniform octahedral structure. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), ultraviolet–visible (UV–vis), Fourier transform infrared spectroscopy (FT-IR) and Brunauer–Emmett–Teller (BET) were used to characterize the products. Additionally, photocatalytic performance of the octahedral Cu31S16 was evaluated. About 99% of the methyl orange was degraded after 60 min.
Keywords: Cu31S16; Octahedra; Nanoparticles; Photocatalytic activity;
Chemical bath deposition of SnO2 and Cd2SnO4 thin films by Hani Khallaf; Chia-Ta Chen; Liann-Be Chang; Oleg Lupan; Aniruddha Dutta; Helge Heinrich; Firoze Haque; Enrique del Barco; Lee Chow (6069-6074).
► A new approach of chemical bath deposition (CBD) of SnO2 thin films is reported. ► The possibility of fabricating a transparent conducting oxide layer of Cd2SnO4 thin films using CBD is investigated. ► Annealed CBD-SnO2 films are orthorhombic, highly stoichiometric, and transparent with an optical band gap of ∼4.42 eV. ► Cd2SnO4 films with a band gap as high as 3.08 eV are obtained. ► Cd2SnO4 films with a carrier density as high as 1.7 × 1020 cm−3; and a resistivity as low as 1.01 × 10−2 Ω-cm are achieved.A new approach of chemical bath deposition (CBD) of SnO2 thin films is reported. Films with a 0.2 μm thickness are obtained using the multi-dip deposition approach with a deposition time as little as 8–10 min for each dip. The possibility of fabricating a transparent conducting oxide layer of Cd2SnO4 thin films using CBD is investigated through successive layer deposition of CBD-SnO2 and CBD-CdO films, followed by annealing at different temperatures. High quality films with transmittance exceeding 80% in the visible region are obtained. Annealed CBD-SnO2 films are orthorhombic, highly stoichiometric, strongly adhesive, and transparent with an optical band gap of ∼4.42 eV. Cd2SnO4 films with a band gap as high as 3.08 eV; a carrier density as high as 1.7 × 1020 cm−3; and a resistivity as low as 1.01 × 10−2 Ω cm are achieved.
Keywords: SnO2; Cd2SnO4; Transparent conducting oxides; Thin films; Chemical bath deposition;
Temperature-dependent phase separation during annealing of Ge2Sb2Te5 thin films in vacuum by Zheng Zhang; Jisheng Pan; Lina Wei-Wei Fang; Yee-Chia Yeo; Yong Lim Foo; Rong Zhao; Luping Shi; Eng Soon Tok (6075-6079).
► Thermal stability of 100 nm Ge2Sb2Te5 during annealing in vacuum was studied. ► Ge diffuses more to the surface from 25 to 100 °C. ► Sb and Te diffuse more to surface from 100 to 200 °C, but start desorbing at 220 °C. ► At 240 °C, Sb and Te desorb completely, leaving Ge-rich droplets on the surface. ► Phase separation degrades Ge2Sb2Te5-based phase change memory under thermal stress.Thermal stability of 100 nm Ge2Sb2Te5 thin film during annealing from room temperature to 240 °C inside a UHV chamber was studied in situ by X-ray photoelectron spectroscopy (XPS) and ex situ by X-ray diffraction (XRD) and atomic force microscopy (AFM). Ge species are found to diffuse preferentially to the surface when GST film is annealed from 25 °C to 100 °C. This process is accompanied by a change of phase whereby the amorphous film completely becomes face-center-cubic (FCC) phase at 100 °C. From 100 °C to 200 °C, both Sb and Te species are observed to diffuse more to the surface. The FCC phase is partially changed into hexagonal-close-pack (HCP) phase at 200 °C. At 220 °C, FCC phase is completely transformed into HCP phase. Loss of Sb and Te are also detected from the surface and this is attributed to desorption due to their high vapor pressures. At 240 °C, Sb and Te species are found to have desorbed completely from the surface, and leave behind Ge-rich 3D droplets on the surface. The separation of Ge2Sb2Te5 into Sb,Te-rich phase and Ge-rich phase is thus the main mechanism to account for the failure of Ge2Sb2Te5-based phase change memory devices under thermal stress.
Keywords: Phase separation; Ge2Sb2Te5; X-ray photoelectron spectroscopy;
A local annular contrast based real-time inspection algorithm for steel bar surface defects by Wu-bin Li; Chang-hou Lu; Jian-chuan Zhang (6080-6086).
► A local annular contrast based real-time inspection algorithm for steel bar surface defects. ► A gray-level comparison between the detection point and its surrounding pixels at a certain distance. ► The threshold changes with the gray-level variation of local annular background. ► The algorithm has high detection success rate and need little time.A new inspection algorithm based on local annular contrast (LAC) for steel bar surface defects is presented. Because of little fluctuation of gray value inside the defects, traditional gradient detection methods could not find the defects accurately and often mistake the boundary of the bright region in center for defects. The LAC-based algorithm doesn’t have this disadvantage. Defects in images can be found due to their large contrast with local annular background (LAB). After average filter to steel bar surface image, the noise could be smoothed to a great extent but the contrast between defects and LAB changes very little. Then the LAC-based algorithm is applied to inspect defects. Experimental results show that the proposed algorithm needs only 13 ms to inspect one steel bar surface image and its detection accuracy exceeds 95%.
Keywords: Local annular contrast; Surface defect detection; Vision inspection; Image processing;
Long-term corrosion investigation of AISI 316L, Co–28Cr–6Mo, and Ti–6Al–4V alloys in simulated body solutions by Shima Karimi; Tirdad Nickchi; Akram M. Alfantazi (6087-6096).
► Weight loss of AISI 316L, Co–28Cr–6Mo, and Ti–6Al–4V alloys in PBS solutions at various BSA concentrations was investigated by static immersion experiments for 8, 14, and 22 weeks. ► Immersed solutions were analyzed by ICP-OES test to detect the amount of ion released from the selected bio-materials. ► Surface concentrations of the specimens were measured by XPS analysis. ► Samples gained weight after 14 weeks of immersion ► Weight gain of the samples can be related to precipitation of Fe on 316L, and Co on Co–28Cr–6Mo.The long-term weight loss, ion release and surface composition of AISI 316L, the Co–28Cr–6Mo and Ti–6Al–4V alloys were investigated in phosphate buffered solutions (PBS) with various bovine serum albumin (BSA) concentrations. All the samples lost weight up to 14 weeks and then started to gain weight. This can be explained by precipitation of dissolved ions on the surface after 14 weeks of immersion. The quantities of the dissolved ions were measured in immersed solution for 8, 14 and 22 weeks by induced coupled plasma-optical emission spectrometer (ICP-OES). The amounts of Fe released from 316L, and Co and Mo released from the Co–28Cr–6Mo alloy decreased after 14 weeks of immersion in PBS and BSA solutions. This observation coincides with the weight change of the samples. The oxide layer composition and concentration of the specimens exposed to solutions for 22 weeks were identified by X-ray photoelectron spectroscopy (XPS) analysis. The XPS results revealed that chromium is the main component of the 316L and Co–28Cr–6Mo alloy. The high Cr concentration of the 316L and Co–Cr–Mo oxide layer corresponds with the slow dissolution rate of Cr compared to other alloying elements of the 316L and Co–28Cr–6Mo alloy.
Keywords: Biomaterial; Oxide film; Immersion test; Protein; Ion release; Surface concentration;
Porous carbon with tailored pore size for electric double layer capacitors application by Hao Chen; Fang Wang; Shanshan Tong; Shuangling Guo; Xiumei Pan (6097-6102).
.Display Omitted► Porous carbons with different micro-mesopore architecture have been successfully prepared by a simple and effective method. ► Electrochemical evaluation suggests that the porous carbons have an excellent performance as same as hierarchical porous carbons. ► The relationship between specific energy and the surface area was studied.A series of porous carbon samples as electric double layer capacitor electrode materials were prepared by a pyrolysis process using phenol formaldehyde resin (PF) as precursors and KOH/ZnCl2 as activation agents. Porous carbon samples were characterized by thermogravimetric analysis, X ray diffraction, nitrogen adsorption/desorption isotherms and transmission electron microscopy. The results showed that the KOH/ZnCl2/PF mass mixing ratio and activation temperature had a remarkable effect on the porosity, the specific surface area and the pore size of the carbons. The prepared carbon material PC-6 exhibits a high specific capacitance of 141.56 F/g and a average speciﬁc energy of 74.13 Wh/kg at a current density of 120 mA/g in the electrolyte of 1 M Et3MeNBF4/PC, and the average speciﬁc energy still remained 49.48 Wh/kg even at a high current density of 2000 mA/g. The excellent electrochemical behavior of PC-6 can be attributed to the highly development pore structure.
Keywords: Supercapacitor; Specific capacitance; Electrochemical performance; Porous carbon;
Effect of calcination temperature on the structural and optical properties of ZnO:Fe powders by Weiying Zhang; Zhenzhong Liu; Zhaojun Liu; Jianguo Zhao (6103-6106).
► Fe doped ZnO powders with hexagonal structure prepared by sol–gel. ► With the increase of calcination temperature, the second phase ZnFe2O4 appeared. ► 650 and 750 °C are optimal temperatures to improve the crystal quality and optical property, which making the small strain in samples. ► With the increase of calcination temperature, the stress converts to strain in samples, and strain increased.ZnO:Fe powders have been prepared by sol–gel method with different calcination temperatures (650 °C, 750 °C, 850 °C and 950 °C). The crystal structures and optical properties were investigated by X-ray diffraction (XRD), Raman spectra and Photoluminescence (PL). The XRD results demonstrated that all of the samples were hexagonal wurtzite structure, and with the increase of calcination temperature, the diffraction peak of (0 0 2) slightly shifts to larger degree. Furthermore, the lattice vibrations have been investigated by Raman spectra, with the increase of calcination temperature, the representative peak E 2 high of ZnO shifts from 437.5 to 434 cm−1, corresponding to degradation of crystalline quality. Also, the dependence of PL spectra on calcination temperature has been investigated detailed.
Keywords: Sol–gel; ZnO:Fe; Structure; Optical property;
Band offsets of epitaxial Tm2O3 high-k dielectric films on Si substrates by X-ray photoelectron spectroscopy by J.J. Wang; Z.B. Fang; T. Ji; W.Y. Ren; Y.Y. Zhu; G. He (6107-6110).
► Single-crystalline Tm2O3 high k films have been deposited on Si (0 0 1) by molecular beam epitaxy (MBE). ► Band alignments of Tm2O3/Si gate stacks were studied by X-ray photoelectron spectroscopy (XPS) for the first time. ► A valence-band offset of −3.1 ± 0.1 eV and a conduction-band offset of 2.3 ± 0.3 eV for the Tm2O3/Si heterojunction have been obtained. ► The energy gap of Tm2O3 is determined to be 6.5 ± 0.3 eV. A relatively thicker interfacial SiO x layer was observed for the as-annealed samples. ► However, no apparent change in band alignment has been observed for Tm2O3/Si heterojunction with the formation of interface layer.Tm2O3 crystalline films have been deposited on Si (0 0 1) by molecular beam epitaxy (MBE). Band alignments of Tm2O3/Si gate stacks were studied by X-ray photoelectron spectroscopy (XPS). According to XPS measurements, it can be noted that a valence-band offset of −3.1 ± 0.1 eV and a conduction-band offset of 2.3 ± 0.3 eV for the Tm2O3/Si heterojunction have been obtained. Based on analysis from O 1s energy-loss spectrum, the energy gap of Tm2O3 is determined to be 6.5 ± 0.3 eV. A relatively thicker interfacial SiO x layer was observed for the as-annealed samples. However, no apparent change in band alignment has been observed for Tm2O3/Si heterojunction with the formation of interface layer, which has been discussed in detail.
Keywords: Tm2O3; High-k dielectric; XPS; Band offsets;
Atomistic simulation of twin boundaries effect on nanoindentation of Ag(1 1 1) films by Lin Yuan; Zhenhai Xu; Debin Shan; Bin Guo (6111-6115).
► Twin boundaries (TBs) effect on nanoindentation of Ag(1 1 1) films was simulated. ► TBs change the dislocation patterns dominating the deformation. ► TBs can act as dislocation sources before losing their coherency. ► TBs are effective obstacles to the motion of dislocations.Atomistic simulations were employed to study the effect of a single twin boundary parallel with the indented surface on nanoindentation of Ag(1 1 1) films. The results show that the twin boundary has little influence on the elastic modulus of films. The load for the initial yield is observably reduced when the twin boundary is very near the indented surface due to the nucleation of the glissile dislocations on the slip plane parallel to the surface, rather than the formation of the tetrahedral sessile lock when nanoindentation on the perfect film. Twin boundaries are effective obstacles to the motion of dislocations, and change the dislocation patterns dominating the deformation, resulting in the hardening of films. In addition, twin boundaries can act as dislocation sources before losing their coherency.
Keywords: Twin boundary; Dislocation; Plastic deformation; Elastic modulus; Nanoindentation; Atomistic simulation;
Corrosion mechanism and model of pulsed DC microarc oxidation treated AZ31 alloy in simulated body fluid by Yanhong Gu; Cheng-fu Chen; Sukumar Bandopadhyay; Chengyun Ning; Yongjun Zhang; Yuanjun Guo (6116-6126).
► Corrosion properties of MAO coated Mg alloys are improved by optimizing frequency. ► The SBF has a significant effect on the corrosion behavior of MAO coated Mg alloy. ► The corrosion damage depends on the MAO coating and the corrosion product layer. ► A corrosion mechanism model for MAO coated AZ31 alloy in the SBF is proposed. ► The corrosion mechanism animation is made to explain the corrosion process..This paper addresses the effect of pulse frequency on the corrosion behavior of microarc oxidation (MAO) coatings on AZ31 Mg alloys in simulated body fluid (SBF). The MAO coatings were deposited by a pulsed DC mode at four different pulse frequencies of 300 Hz, 500 Hz, 1000 Hz and 3000 Hz with a constant pulse ratio. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. The corroded surfaces were examined by X-ray diffraction (XRD), X-ray fluorescence (XRF) and optical microscopy. All the results exhibited that the corrosion resistance of MAO coating produced at 3000 Hz is superior among the four frequencies used. The XRD spectra showed that the corrosion products contain hydroxyapatite, brucite and quintinite. A model for corrosion mechanism and corrosion process of the MAO coating on AZ31 Mg alloy in the SBF is proposed.
Keywords: Microarc oxidation; AZ31 magnesium alloy; Pulse frequency; Simulated body fluid; Hydroxyapatite; Corrosion mechanism; Model;
Preparation and characterization of poly(glycidyl methacrylate) grafted from magnesium hydroxide particles via SI-ATRP by Jianhui Liu; Na Feng; Suqin Chang; Hongliang Kang (6127-6135).
► PGMA grafted from Mg(OH)2 particles were synthesized via SI-ATRP. ► The density of initiator on the surface was significantly increased by introducing more hydroxyl groups via ATRP of HEMA on the surface. ► The percentage of grafting PG (%) of PGMA on Mg(OH)2 particles reached to 116.6%. ► The thickness of the grafted polymer layer increased with the increasing of polymerization time and reached to 197.6 nm after 300 min. ► The initial decomposition temperature of Mg(OH)2-g-PHEMA–PGMA composite particles (253 °C) is much lower than that of untreated magnesium hydroxide (337 °C).In order to improve the compatibility of magnesium hydroxide particles [Mg(OH)2] and polymer matrix, poly(glycidyl methacrylate) (PGMA) grafted from magnesium hydroxide particles were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). In this work, two approaches for the immobilization of ATRP initiator on the magnesium hydroxide particles surface were compared and selected. The density of initiator was significantly increased by the method of introducing more hydroxyl groups via ATRP of 2-hydroxyethyl methacrylate (HEMA) on the surface. The percentage of bromine atom for the initiator-functionalized magnesium hydroxide particles [Mg(OH)2-g-PHEMA–Br] reached to 1.75%, compared to 0.48% for Mg(OH)2–Br determined by XPS analysis. The surface-initiated ATRP of glycidyl methacrylate (GMA) can be conducted in a controlled manner, as revealed by the linear kinetic plot, linear increase of number average molecular weight (M n) with monomer conversions, and the relatively narrow molecular weight distributions (M w/M n ∼ 1.4) of PGMA chains. The percentage of grafting PG (%) and the thickness of the grafted polymer layer increased with the increasing of polymerization time and reached to 116.6% and 197.6 nm after 300 min respectively. As for the polymerization with different initial monomer concentration, the number average molecular weights (M n) and weight average molecular weights (M w) of PGMA increased with the increasing of initial monomer concentration. TGA indicated that the initial decomposition temperature of Mg(OH)2-g-PHEMA–PGMA composite particles (253 °C) was much lower than that of unmodified magnesium hydroxide particles (337 °C).
Keywords: Surface modification; ATRP; Magnesium hydroxide particles; Grafting from; Polymers;
Preparation and photocatalytic properties of N-doped nano-TiO2/muscovite composites by S. Zhou; J. Lv; L.K. Guo; G.Q. Xu; D.M. Wang; Z.X. Zheng; Y.C. Wu (6136-6141).
► By hydrolysis–precipitation, nano-TiO2 particles successfully sedimentate on muscovite surfaces, and TiO2 coating is very dense and uniform. ► By the doping of nitrogen, N-doped nano-TiO2/muscovite composites show obvious response to visible light and photocatalytic activity. ► Compared with pure TiO2 powders, N-doped nano-TiO2/muscovite composites present better recycle property through the repeated experiments.Using muscovite as the carrier, TiCl4 as the source of titanium, urea as the neutralizer, nano-TiO2/muscovite composites (TiO2/M) were prepared by the method of hydrolysis–precipitation. Then N-doped TiO2/M composites were prepared by using urea as dopant after calcination at 500 °C for 2 h. The samples were characterized by XRD, SEM, EDS, XPS and DUV methods. The photocatalytic activity of samples was evaluated by degradation of methyl orange under visible light irradiation (halogen lamp, 250 W). The results showed that the surfaces of muscovite were uniformly coated by nano-TiO2, which combined with the muscovite surface via the Si―O―Ti and O―Ti―N bonds. The grain growth of TiO2 and the phase transformation from anatase to rutile were restrained by the doping of nitrogen. Meanwhile, the absorption edge of samples after doping exhibited red-shift from 390 nm to 430 nm, showing obvious response to visible light. The degradation rate of methyl orange (20 mg L−1) reached 67.15% after irradiation of 250 W halogen lamp for 1 h (doping ratio was 1:3), while the degradation rate of un-doped sample was just 8%.
Keywords: TiO2/M; Hydrolysis–precipitation; N-doped; Photocatalysis; Visible light;
Effects of CdCl2 heat treatment on the morphological and chemical properties of CdTe/CdS thin films solar cells by Khaled M. AbuEl-Rub; S.-R. Hahn; S. Tari; M.A.K.L. Dissanayake (6142-6147).
► CdTe/CdS/ITO/glass solar cells annealed at 340–420 °C temperatures were studied with and without CdCl2 treatment using SEM and XPS. ► CdCl2 treated CdTe structures exhibited recrystallization and a progressive increase in grain sizes upon annealing. ► XPS spectra for S 2p, Cd 3d and Te 3d peaks were analyzed for the as-grown and for the annealed samples with and without CdCl2 treatment. ► The spectra show the TeO3 peaks are removed upon annealing the CdCl2 treated samples and enhanced upon annealing without CdCl2 treatment.The morphological and chemical changes of CdTe surface in CdTe/CdS/ITO/glass solar cells, due to CdCl2 solution treatment followed by annealing in air from 340 to 420 °C were studied using SEM and XPS. SEM micrographs showed that the supersaturated CdCl2 samples exhibited recrystallization and a progressive increase in grain sizes upon annealing. The grain sizes of the samples increased up to about 3–4 μm when annealed above 410 °C. XPS spectra for the S 2p, Cd 3d and for the Te 3d were recorded and analyzed for the as-grown structures and for structures annealed at different temperatures with and without CdCl2 treatment. The spectra clearly show that annealing the CdCl2 supersaturated samples removes TeO3 peaks, while annealing the structures without CdCl2 treatment enhances the TeO3 peaks. The I–V measurements revealed that V oc higher than 680 mV and J sc close to 20 mA/cm2 were obtained for CdTe/CdS solar cells annealed under optimum conditions of 410 °C for 15 min. The improvement of V oc and J sc after CdCl2 heat treatment can be attributed to dissolving the oxidations at the free surfaces and recrystallizations of CdTe layer.
Keywords: CdTe/CdS/ITO/glass structures; CdCl2 heat treatment; Morphology; Annealing; CBD; SEM; XPS;
Enhancing the surface properties of the immobilized Degussa P-25 TiO2 for the efficient photocatalytic removal of methylene blue from aqueous solution by M.A. Nawi; Salmiah Md. Zain (6148-6157).
Percentage colour removal of 12 mg L−1 of methylene blue dye (MB) by photolysis, P-25 TiO2 slurry system, and immobilized P-25TiO2/ENR/PVC and P-25TiO2/ENR/PVC/5 h catalyst plates using a 45 W fluorescent lamp from PHILIPS ecotone, high lumen model ES E27 as the light source. Immobilized P-25TiO2/ENR/PVC/5 h photocatalyst system was found to perform better than a P-25 TiO2 slurry system for the photocatalytic degradation of MB.Display Omitted► Immobilized Degussa P25 system with enhanced surface properties was fabricated. ► Surface enhancement was achieved via photocatalytic removal of ENR50 binder. ► Immobilized system performed better than Degussa P-25 slurry system. ► The ENR-50 binder photocatalytically degraded while PVC did not. ► The immobilized system was highly efficient, sustainable and reusable.A method has been developed for enhancing the surface properties of immobilized Degussa P-25 TiO2 nanoparticles on glass plate supports with excellent photocatalytic activity. The immobilization technique utilized a dip-coating method involving a coating solution containing Degussa P-25 TiO2 particles, epoxidized natural rubber (ENR-50) and poly vinyl chloride (PVC) in a mixture of toluene and dichloromethane. The optimum ratio of ENR/PVC blend was found to be 1:2. Immobilization process of the composite appeared to reduce the specific surface area by at least half of the pristine P-25 TiO2 particles. However, a systematic removal of ENR-50 additive via a 5 h photocatalytic process enabled the immobilized photocatalyst (P-25TiO2/ENR/PVC/5 h) to regenerate the surface area to within 86% of the pristine P-25 TiO2 particles, produce bigger pore volume and smaller particle size. The enhanced surface properties of the immobilized P-25/ENR/PVC/5 h photocatalyst system generated a photocatalytic performance as good as the slurry method of the P-25 TiO2 nanoparticles for the photocatalytic degradation of MB dye in aqueous solution. The immobilized P-25TiO2/ENR/PVC/5 h catalyst plate was also found to be highly reusable up to at least 10 runs without losing its photocatalytic efficiency. Above all, the system could avoid tedious filtration step of the treated water as normally observed with the aqueous slurry system.
Keywords: P-25 TiO2; Immobilized; Methylene blue; ENR; PVC;
Multifunctional mesoporous materials with acid–base frameworks and ordered channels filled with ionic liquid: Synthesis, characterization and catalytic performance of Ti–Zr-SBA-15-IL by Wenjuan Zhang; Hua Wang; Jinyu Han; Zhiqiang Song (6158-6168).
Display Omitted► A multifunctional Ti–Zr-SBA-15-IL materials were synthesized by post-grafting ionic liquid onto dual-metal doped SBA-15. ► The characterization indicated that the as-synthesized materials have acid–base inorganic frameworks and the ordered channels filling with ionic liquid. ► Weakly basic sites derived from the ionic liquid could co-exist with medium strong acid sites from the framework. ► The cooperative effect of acid–basic framework and ionic liquid enhanced catalytic activity for the cycloaddition of CO2 with epoxides.A series of novel multifunctionalized SBA-15 with titanium and zirconium incorporated frameworks and ionic liquid filled ordered channels were synthesized for the first time, by combining framework doping and post-grafting. The as-prepared materials were extensively characterized to investigate the mesostructural and chemical properties. The results indicated that the products possess the periodically ordered mesoporous structure. Titanium and zirconium were efficiently introduced into the framework of the mesostructure, generating medium strong acid and basic sites. N-methylimidazole ionic liquid was covalently grafted into the channels of mesoporous materials. Moreover, a higher cooperative catalytic performance originated from the dual-metal centers and ionic liquid was shown in catalyzing the cycloaddition of carbon dioxide with epoxides. A plausible reaction mechanism was proposed based on the experimental results.
Keywords: Multifunctional mesoporous material; Ti–Zr-SBA-15-IL; Acid–base framework; Ionic liquid;