Small Amount Of TiO2 Research Articles

A Novel Nano-Structured Sn-SnO2-TiO2/Cu5Sn5 Composite Film Electrodeposited on Cu As High Capacity Anode Materials for Lithium Ion Batteries

Introduction. Lithium-ion batteries (LIB) have been widely used as power sources in many electric/electronic products such as cellular phones, digital cameras, portable computers, etc. Recently, considering on the applications in automobile industry for electric vehicles (EVs) and plug-in hybrid vehicles (PHVs), it is highly desirable to explore new electrode materials with higher power density and satisfied lifetime cycles to meet expanding needs for lithium-ion battery industry. Among various anode materials, Sn-based materials have attracted great attention as promising candidate materials for the replacement of the conventional carbonaceous anode materials of Li-ion batteries, owing to that the Sn materials, with good electrical conductivity, possess higher theoretical capacitance (Li4.4Sn: 994 mAh g-1) than graphite (LiC6: 372 mAh g-1). However, it is known that pure Sn material delivers substantial volume changes during alloying/de-alloying process with Li. During the charge-discharge cycles, volume change of Sn will cause the deterioration and peeling of the film electrode from the Cu electric collectors, thus resulting in rapid capacity fade and significantly affecting the cyclic lifetime of the batteries. In this study, we propose a novel nanoporous, bi-layered Sn-SnO2-TiO2/Cu6Sn5 (SSTC) composite film that directly electrodeposited on Cu sheets as binder-free and conductor-free anode material for Li-ion rechargeable batteries. Here, the nanoporous structure can provide space for the volume change of Sn material, and the TiO2 and Cu6Sn5 alloy can meditate the volume change inside the Sn-based composite film and at the film/Cu interface during the lithium insertion/extraction. Experimental. Various Sn-SnO2-based composite films were fabricated on Cu sheets by a hybrid electroplating method, i.e., combining electro-deposition with electrophoric deposition, using a mixed EtOH-H2O bath mainly containing SnCl2 and TiCl3, followed by annealing at 473 K for 2 h. The effects of ratios of [Sn2+]/[Ti3+] and EtOH/H2O, and operating conditions on the formation and microstructures of the plating films were investigated. The morphology, chemical composition, chemical state, and crystalline structure of the electrodeposited films before and after heat treatment were investigated by FE-SEM, EDX, TEM (FIB), XRD, and XPS. Moreover, electrochemical charge-discharge performances of the SSTC composite films on Cu were investigated with home-made pouch cells which assembled in an Ar-filled glove box. The cathode was utilized with a lithium metal foil, and the electrolyte solution was made of 1M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) with a volumetric ratio of 1:1:1, respectively. The cells were charged and discharged at 0.1 A g-1 by a battery test system, and the cut-off voltage range was 0.01 – 2.0 V or 0.01 – 3.0 V (vs. Li+/Li) at 50 – 100 mA g-1 and 303 K. Results and Discussion. Figs. 1a-b show the surface FESEM images of as-deposited Sn-TiO2 composite films on Cu sheets, which were fabricated in plating baths with different [Sn2+]/[Ti3+] ratios. It can be seen that the films composed of nano-flakes or nano-needles, thus making a networked nanoporous structure. The morphologies of the electrodeposited films were depended predominantly on ratios of [Sn2+]/[Ti3+] and EtOH/H2O in electroplating baths, while only slightly affected by operating conditions. According to EDX and XPS analysis, the electrodeposited films consisted of Sn, SnO2, and a small amount of TiO2 in 1–10 at%, in proportional to the [Sn2+]/[Ti3+] ratio. A representative cross-sectional TEM image in Fig.1c disclosed that the electrodeposited specimen after annealing at 473 K for 2h consisted in a nanoporous top-layer with scaly Sn nano-crystals and a dense under-layer of Cu-Sn alloy on Cu substrate. The corresponding XRD pattern of a SSTC composite film on Cu after annealed was illustrated in Fig.1d. The Sn electrodeposits had a polycrystalline structure with a preferential in Sn (200) facet. In addition, an intermetallic compound of Sn and Cu in form of h-Cu6Sn5 was also detected, which can be attributed to the alloying reaction at the interface between the Sn-TiO2 deposited film and Cu substrate during annealing. Moreover, galvanostatic charge/discharge tests revealed that the SSTC composite films delivered a high initial specific discharge capacities of 1042 mAh g-1, with a maximum value of 1227 mAh g-1, and a high Coulombic efficiency of more than 90%, indicating a promising future as binder-free and conductor-free anode materials for LIBs. Figure 1

High temperature oxidation behavior of Ni-based superalloy GH202

The isothermal oxidation kinetic and oxidation behavior of Ni-based superalloy GH202 were investigated at temperatures from 800°C to 1100°C. The microstructure of GH202 was characterized by scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD). The composition and morphologies of oxide scales of the surface and cross-section samples were examined by X-ray diffraction (XRD), electron probe microanalysis (EPMA), and SEM combined with energy-dispersive spectroscopy (EDS). The results show that the growth of the oxide scales on GH202 obeyed a parabolic law with an activation energy of 247.8KJ·mol−1 from 800°C to 1100°C. The continuous and dense oxide scales that formed at 800°C and 900°C were composed of Cr2O3, NiCr2O4 and a small amount of TiO2. Beneath the oxide scales, aluminum-rich oxides formed along the grain boundaries due to internal oxidation. After treatment at 1000°C for 150h, the oxide scale was separated into two layers, the outer layer with sparse holes that was mainly composed of Cr2O3 and TiO2 and an inner layer of dense Cr2O3. At 1100°C for 100h the outer layer was spalled, due to the looser oxide scale with large blocks of TiO2 and NiCr2O4 which provided channels for oxygen diffusion.

Photocatalytic properties of fresh and pyrolyzed transparent nanocomposite films layer-by-layer fabricated from alternative layers of graphene and titanate nanotube

Aiming at the efficient utilization of light absorption and controlled contacting of graphene and titania nanoparticles, layer-by-layer (LbL) technique was employed to fabricate composite films of nanosized thickness with alternative layers of graphene oxide and titanate nanotube and the fabrication processes were monitored by the surface charge changes of substrates. By appropriately choosing synthesis conditions, it is possible to build up uniform multicomponent films which are transparent from visible through UV (lower to 200nm) wavelengths up to ≈8 bilayers. The photocatalytic activity of the fresh and pyrolyzed composite films was found dependent on the bilayer number, the reactant concentration, and the pyrolysis temperature. Photodecomposition rate of methyl orange together with mineralization rate by the composite films was enhanced by about two folds at the maximum as compared to the pure titania film. The results demonstrated that thickness control by LbL technique followed by post pyrolysis is an important approach to obtain uniform hybrid films with robustness, transparency, and the close contacting of graphene and titania for achieving enhanced photocatalysis at a small amount of TiO2.

A facile preparation of ceramic coatings on Ti alloys for thermal protection systems

In order to reduce the effects of solar energy on the instruments and the apparatus in the outer space, two different kinds of ceramic coatings were prepared on Ti6Al4V alloys by plasma electrolytic oxidation (PEO) in zirconate electrolytes. The phase composition, microstructure, thickness, and roughness of coatings were examined by XRD, SEM, EDS, thickness measurement gauge, and roughness measuring instrument, respectively. The infrared emissivity and solar absorbance of the ceramic coatings were studied with the UV–vis–NIR spectrophotometer and infrared reflectometer. The results show that ZrO2 coatings are dense and deep gray–green, and mainly composed of m-ZrO2, t-ZrO2. In addition, a small amount of TiO2, ZrTiO4, and the amorphous compound containing P exists in the coating. The intrinsic solar absorbance and emissivity of ZrO2 coatings are 0.92 and 0.76, respectively. The KZr2(PO4)3 coating is rough, thick, and white with the main crystalline of KZr2(PO4)3. The intrinsic solar absorbance and emissivity of the KZr2(PO4)3 coating are 0.62 and 0.91, respectively. For both coatings, the absorbance decreases while the emissivity increases due to an increase in the real surface area of the coatings by increasing thickness and roughness of the coatings as the PEO time progresses. The porous structure of the KZr2(PO4)3 is proved to be ideal for high emissivity and low absorbance materials with the lowest solar absorbance (0.239), the highest infrared emissivity (0.99), and a corresponding balance temperature of the coating of 276K.

Study of Isothermal Oxidation Behavior of FGH91 Superalloy

Oxidation behavior of FGH91 superalloy in air and the temperature range of 540 to 980 °C for period up to 100h has been studied. The results indicate that oxidation kinetics obeyed parabolic law, and the activation energy of oxidation was calculated to be 98.2 KJ/mol. The scales on the surface were determined by SEM, EDS and XRD, the results show that the oxidation scales were composed of three layers: the outer layer was composed of Cr2O3 layer with a small amount of TiO and NiCr2O4 spinel; the intermediate layer was made up of Al2O3 and matrix alloy; and a small amount of titanium-nitride disperse in the inner layer. Besides, γ’-free layer was formed under the oxidation scales due to the impoverishment of Al in this layer, which was induced by the formations of Al2O3.

Controllable Fabrication of Nanostructured Sn-TiO2 Composite Films on Cu Sheets as Anode Materials for Lithium-Ion Battery

Nanoporous Sn-TiO2 composite films with large surface areas were fabricated on Cu sheets by a hybrid electroplating method, i.e., electrodeposition and electrophoretic deposition, using an ethanol-water mixed bath containing SnCl2 and TiCl3. The Sn-TiO2 composite films, containing a large amount of oxygen and a small amount of TiO2 in 1–4 at%, composed of nano-crystals in forms of dendrites, needles, flakes or scales, which depended predominantly on the mole ratio of [Sn2+]/[Ti3+], the volume ratio of ethanol/water in plating baths, and the current density. The initial specific discharge capacities were 495, 1069, and 772 mAh g-1 for the nanoporous Sn-TiO2 composite films formed in plating baths with EtOH/H2O ratios of 9:1, 6:1, and 3:1, respectively. The enhanced discharge capacity and improved retention of composite films can be attributed to the nanoporous structure and the inclusion of TiO2, which mitigate the volume change during the lithiation and delithiation of Sn nanocrystals.

29pm3-PN-35 酸化チタンナノ粒子含有溶液中でのフェムト秒レーザ金属造形の高速化

Metallic microstructures were effectively precipitated by femtosecond laser irradiation into silver nitrate solution with TiO_2 nanoparticles. Femtosecond laser irradiation can induce nonlinear optical absorption, which enables to photo-reduction via multi-photon process only near the focal volume. The surfaces of the precipitated structures were relatively smooth, and the structurer had hemicircle-like cross-section. It was found that the cross-section area was as large as approximately 25 times compared to that of the solution without the nanoparticles. Additionally, maximum scanning speed was achieved to be 900 μm/s, which corresponds to 15 times higher than that of conventional solution. Such high photosensitivity, achieved even by small amount of TiO_2 nanoparticles, offer opportunities for further integration of hybrid micro-/nanodevices in nanophotonics.

Dose-dependent clearance kinetics of intratracheally administered titanium dioxide nanoparticles in rat lung.

AEROSIL(®) P25 titanium dioxide (TiO2) nanoparticles dispersed in 0.2% disodium phosphate solution were intratracheally administered to male F344 rats at doses of 0 (control), 0.375, 0.75, 1.5, 3.0, and 6.0 mg/kg. The rats were sacrificed under anesthesia at 1 day, 3 days, 7 days, 4 weeks, 13 weeks, and 26 weeks after administration. Ti levels in various pulmonary and extrapulmonary organs were determined using sensitive inductively coupled plasma sector field mass spectrometry. One day after administration, the lungs contained 62-83% of TiO2 administered dose. Twenty-six weeks after administration, the lungs retained 6.6-8.9% of the TiO2 administered at the 0.375, 0.75, and 1.5 mg/kg doses, and 13% and 31% of the TiO2 administered at the 3.0 and 6.0 mg/kg doses, respectively. The pulmonary clearance rate constants from compartment 1, k1, were estimated using a 2-compartment model and were found to be higher for the 0.375 and 0.75 mg/kg doses of TiO2 (0.030/day for both) than for TiO2 doses of 1.5-6.0 mg/kg (0.014-0.022/day). The translocation rate constants from compartment 1 to 2, k12, were estimated to be 0.015 and 0.018/day for the 0.375 and 0.75 mg/kg doses, and 0.0025-0.0092/day for doses of 1.5-6.0mg/kg. The pulmonary clearance rate constants from compartment 2, k2, were estimated to be 0.0086 and 0.0093/day for doses of 0.375 and 0.75 mg/kg, and 0-0.00082/day for 1.5-6.0 mg/kg doses. Translocation of TiO2 from the lungs to the thoracic lymph nodes increased in a time- and dose-dependent manner, accounting for 0.10-3.4% of the administered dose at 26 weeks. The measured thoracic lymph node burdens were a much better fit to the thoracic lymph node burdens estimated assuming translocation from compartment 1 to the thoracic lymph nodes, rather than those estimated assuming translocation from compartment 2 to the thoracic lymph nodes. The translocation rate constants from the lungs to the thoracic lymph nodes, kLung→Lym, were 0.000037-0.00081/day, and these also increased with increasing doses of TiO2. Although a small amount of TiO2 had translocated to the liver by 3 days after the administration (0.0023-0.012% of the highest dose administered, 6.0 mg/kg), translocation to the other extrapulmonary organs was not detected.

PHOTOCATALYTIC PROPERTIES OF TiO2/CNTs FILMS WITH DIFFERENT MORPHOLOGY ON STAINLESS STEEL SUBSTRATES

CNTs– TiO 2 films with different morphology were fabricated on stainless steel substrates through chemical vapor hydrolysis deposition (CVHD) process and sol–gel process, respectively. Their morphology was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic properties of the films were tested in the degradation of methyl orange by UV light irradiation. The results revealed that TiO 2 nanoparticles could form a continuous layer on the surface of CNTs through CVHD process. While for sol–gel process, most TiO 2 nanoparticles were isolated and only a small amount of TiO 2 nanoparticles attached on the surface of CNTs. And the photocatalytic property of TiO 2/CNTs film synthesized through CVHD process was better than that of TiO 2/CNTs films synthesized through sol–gel process. Electrochemical impedance spectroscopy (EIS) analysis illuminated that TiO 2/CNTs synthesized through CVHD process displayed a smaller resistance than the sample which was synthesized through sol–gel process and certified that the close combination between TiO 2 and CNTs could minimize recombination of photogenerated electrons and holes, and thus promote the photocatalytic property.

Adsorption and desorption of toluene on nanoporous TiO2/SiO2 prepared by atomic layer deposition (ALD): influence of TiO2 thin film thickness and humidity

Adsorption and desorption of toluene on bare and TiO2-coated silica with a mean pore size of 15 nm under dry and humid conditions were studied using toluene breakthrough curves and temperature programmed desorption (TPD) of toluene and CO2. Two TiO2/silica samples (either partially or fully covered with TiO2) were prepared with 50 and 200 cycles of TiO2 atomic layer deposition (ALD), respectively. The capacity of silica to adsorb toluene improved significantly with TiO2-thin film coating under dry conditions. However, toluene desorption from the surface due to displacement by water was more pronounced for TiO2-coated samples than bare samples under humid conditions. In TPD experiments, silica with a thinner TiO2 film (50-ALD cycled) had the highest reactivity for toluene oxidation to CO2 both in the absence and presence of water. Toluene adsorption and oxidation reactivity of silica can be controlled by modifying the silica surface with small amount of TiO2 using ALD.

W-Ti Alloy Prepared by Hydrogen Reduction of Nanometer WO<sub>3</sub>-TiH<sub>2</sub> Powders

In this study, TiH2 and WO3 powders were co-milled together, then the ultrafine powders were reduced at H2 atmosphere, and W-Ti alloys were prepared by the solid phase sintering. The main purpose of WO3 powder instead of the W powder was to use the transition of the lattice type of WO3, and the lattice distortion and defects in the lattice of W would promote Ti atom diffusing into W. It was easy to form a W-rich solid solution and reduce the effect of Ti-rich phase. The results showed that when the milling time of WO3-TiH2 was 24h, the particle size of mixed powder reached nanoscale, and WO3 particles were coated on the surface of TiH2 particles. The particle size changed unobviously with the increase of the milling time. The XRD analysis showed that the milled WO3 and TiH2 were not decomposed in the milling process. When WO3-TiH2 milled powders were decomposed in the H2 atmosphere at 800, WO3 reduction was not sufficient, and the middle phase of WO2 was existed. When the reduction temperature was 850 for 2h, WO3 was reduced to W, and the phase of WO2 was disappeared. A small amount of TiO2 was formed by the decomposed Ti and decomposed O from WO3. W-10Ti alloys were prepared by the solid-phase sintering with the reduced powders at 850. It was found that the amount of W-rich solid solution in W-10Ti alloy was decreased, because the diffusion of Ti to W was inhibited by a small amount of TiO2 in grain boundaries during the sintering process.

Study on the Microstructure and Properties of Laser Remelted Ceramic Coatings on Low Carbon Steel Surface

The plasma spraying Al2O3-13%TiO2 (abbreviated as AT-13) ceramic coatings on Q235B steel surface were dealed with laser remelting technique. The microstructure and properties before and after laser remelting were studied. Experiment results shown that the microstructure of laser remelted ceramic coatings was dense, no porosity appeared. The main compositions of laser remelted ceramic coatings were α-Al2O3 and a small amount of TiO2 and TiAl2O5. Microhardness of AT-13 plasma spraying coatings and laser remelting coatings were measured with vickers, and the maximum microhardness value of the former was 1000 HV0.2 , while that of the latter was 1700 HV0.2; The average bonding strength value of AT-13 plasma spraying coating was 24.36 Mpa, while the average bonding strength value of laser remelting coating was more than 67.02 Mpa. The wear resistance of laser remelting coatings was higher than that of AT-13 plasma spraying coatings through the pin-dish particle wear test.

Laboratory Evaluation of Environmental Performance of Photocatalytic Titanium Dioxide Warm-Mix Asphalt Pavements

AbstractThe use of titanium dioxide (TiO2) coating for pavements has received considerable attention in recent years to improve air quality near large metropolitan areas. However, the proper method of applying TiO2 to asphalt pavements is still unclear. This study evaluated the benefits of incorporating TiO2 in the preparation of warm-mix asphalt (WMA). Two application methods to integrate TiO2 were evaluated, a water-based TiO2 solution applied as a thin coating and using TiO2 as a modifier to asphalt binder in the preparation of WMA. On the basis of the results of the experimental program, it was determined that the photocatalytic compound was not effective in degrading NOx in the air stream when used as a modifier to the binder in the preparation of WMA. This could be attributed to the fact that only a small amount of TiO2 is present at the surface. When used as part of a surface spray coating, TiO2 was effective in removing nitrogen oxide (NOx-) pollutants from the air stream with an efficiency rangin...

Effect of TiO2 surface treatment on the mechanical properties of cured epoxy resin

Mechanical properties of epoxy resin toughened with two different submicron particles of TiO2 at different weight fractions (1, 3, and 5%, respectively) were investigated. The first TiO2 particles are surface treated with Al2O3–SiO2, and the second are surface treated with Al2O3–ZrO2. The composites were characterized by tensile, flexural, pull off and abrasion tests, followed by X-ray photoelectron spectroscopy and scanning electron spectroscopy of the fracture surfaces. A small amount of TiO2 (~1%) submicron particles improves the flexural, abrasion and pull-off strengths, while amounts up to 5% significantly enhance tensile properties only. TiO2 particles surface treated with Al2O3–ZrO2 produce an epoxy composite with higher strength and weight loss but lower pull off strength and more brittle than that prepared with Al2O3–SiO2 particles. The TiO2 particles surface treated with Al2O3–SiO2 have a higher adherence to the epoxy composite matrix than the particles treated with Al2O3–ZrO2 as shown by scanning electron spectroscopy.

A new method for deposition of nano sized titanium nitride on steels

Active screen plasma nitriding is a new and common method for deposition of Iron nitride. Since techniques such as Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD) and Plasma Assisted Chemical Vapor Deposition (PACVD) are usually applied in order to deposit the titanium nitride and each of these methods has its own problems, in this research active screen plasma nitriding method was introduced as a novel approach for deposition of nano sized titanium nitride. H11 tool steel samples were coated by plasma nitriding method at 550 °C for 5, 7.5 and 10 h, using three gas mixtures consisted of H 2/N 2 = 3, 1 and 1/3. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) were employed to investigate the coating properties such as grain size, layer thickness and chemical composition. Results showed that the proportion of H 2 in the gas mixture was a crucial point in order to obtain a perfect coating. By increasing the coating time, the grain size and the layer thickness increased. XPS results showed that the coating was mainly consisted of TiN + TiN 0.1 together with a small amount of TiO 4.

Tailoring the microstructure of mechanoactivated Al 2O 3 and SiO 2 mixtures with TiO 2 addition

This paper reports on the effect of TiO 2 on mullitization, anisotropic grain growth and densification of Al 2O 3 and SiO 2 mixtures, which are activated by a high-energy ball milling process using tungsten as milling media. High-energy activation significantly promotes mullitization in the mixture of Al 2O 3 and SiO 2 powders, and is a pre-requisite for the occurrence of anisotropic grain growth of mullite. There is a subtle interplay and competition between anisotropic grain growth and densification, depending on the amount of TiO 2. Small amount of TiO 2 has a positive effect on the phase formation and anisotropic grain growth of mullite, while high concentration of TiO 2 suppresses anisotropic grain growth, and thus is beneficial to densification. As a result, the microstructure and densification of the mullite ceramics can be manipulated by the doping levels of TiO 2.

Oxidation resistance of TiAl 3–Al composite coating on orthorhombic Ti 2AlNb based alloy

The TiAl 3–Al composite coating on orthorhombic Ti 2AlNb based alloy was prepared by cold spray. Oxidation in air at 950 °C indicated that the bare alloy exhibited poor oxidation resistance due to the formation of TiO 2/AlNbO 4 mixture and intended to scale off at the TiO 2 rich zone. A nitride layer about 2 µm was formed under the oxide layer. The oxygen invaded deeply into the alloy and caused severe microhardness enhancement in the near surface region. The TiAl 3–Al composite coating exhibited parabolic oxidation kinetics and showed no sign of degradation after oxidized up to 1098 h at 950 °C in air under quasi-isothermal condition. No scaling of the coating was observed after oxidized at 950 °C up to the tested 150 cycles. The major oxide in the oxidized coating was Al 2O 3. The AlTi 2N, TiAl and small amount of TiO 2 were also observed in the oxidized coating. The EPMA and microhardness tests showed that inward oxygen diffusion was prevented by the interlayer, which was formed between the composite coating and the substrate during heat-treatment. Microstructure analyses demonstrated that the interlayer play a major role in protecting the substrate alloy from high temperature oxidation and interstitial embrittlement.

Crystallization Behavior of Ferroelectric Glass-Ceramics of the Na<sub>2</sub>O-Nb<sub>2</sub>O<sub>5</sub>-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> System Contained TiO<sub>2</sub>

The ferroelectric glass-ceramic of the composition Na2O-Nb2O5-Al2O3-SiO2 was prepared by controlling crystallization of the glass that added with small amount of TiO2. The effect of TiO2 content on crystallization behavior and the dielectric property were determined. X-ray diffraction studied indicated that NaNbO3, NaNbO8 and a compound of alkali alumino silicate composition were readily formed in the as-quenched glass as the product of phase separation. After treatment at 700oC for various times, NaNbO3 volume fraction was found to increase with time. Crystalline size of the NaNbO3 was lower than 300 nm and it was developed with treatment time. Presence of TiO2 had considerably effect on NaNbO3 volume fraction when treatment time shorter than 1.0 h. The dielectric response of the glass-ceramic samples was found to arise from all contributions of crystalline phases and glass matrix responds.

Comparison of Dye Photodegradation and its Coupling with Light-to-Electricity Conversion over TiO2 and ZnO

Through comparing the photocatalytic performance of microscale ZnO, nano ZnO, and Degussa P25 titania (P25), it was found that the microscale ZnO exhibited 2.6-35.7 times higher photocatalytic activity for the photodegradation of various dye pollutants than P25 under both UV-visible and visible irradiation and showed much better photostability than the nano ZnO. The photocatalysts were characterized with XRD, Raman, BET, DRUV-vis, adsorption of dye, photoelectrochemical measurement, and PL. The much higher photocataltyic activity of the microscale ZnO than P25 under UV-visible irradiation is attributed to the higher efficiency of generation, mobility, and separation of photoinduced electrons and holes. The much higher visible photocataltyic activity of the microscale ZnO than P25 is due to the higher photosensitization efficiency of electron transfer from an excited dye to the conduction band of the microscale ZnO than that of P25. The much better photostability of the microscale ZnO than the nano ZnO is due to its better crystallinity and lower defects. The photostability of the microscale ZnO is greatly improved by the surface modification of ZnO with a small amount of TiO(2). On the basis of the excellent photocatalytic performance of the microscale ZnO and TiO(2)-modified ZnO, a novel device of coupling photodegradation with light-to-electricity conversion was developed, which is a promising candidate for the photocatalytic removal of dye pollutants and a renewable energy source.

Microstructure and corrosion behavior of coated AZ91 alloy by microarc oxidation for biomedical application

Magnesium and its alloy currently are considered as the potential biodegradable implant materials, while the accelerated corrosion rate in intro environment leads to implant failure by losing the mechanical integrity before complete restoration. Dense oxide coatings formed in alkaline silicate electrolyte with and without titania sol addition were fabricated on magnesium alloy using microarc oxidation process. The microstructure, composition and degradation behavior in simulated body fluid (SBF) of the coated specimens were evaluated. It reveals that a small amount of TiO 2 is introduced into the as-deposited coating mainly composed of MgO and Mg 2SiO 4 by the addition of titania sol into based alkaline silicate electrolytic bath. With increasing concentration of titania sol from 0 to 10 vol.%, the coating thickness decreases from 22 to 18 μm. Electrochemical tests show that the E corr of Mg substrate positively shifted about 300∼500 mV and i corr lowers more than 100 times after microarc oxidation. However, the TiO 2 modified coatings formed in electrolyte containing 5 and 10 vol.% titania sol indicate an increasing worse corrosion resistance compared with that of the unmodified coating, which is possibly attributed to the increasing amorphous components caused by TiO 2 involvement. The long term immersing test in SBF is consistent with the electrochemical test, with the coated Mg alloy obviously slowing down the biodegradation rate, meanwhile accompanied by the increasing damage trends in the coatings modified by 5 and 10 vol.% titania sol.