Self-repairing Al_(2)O_(3)-TiO_(2)coatings fabricated through plasma electrolytic oxidation with various cathodic pulse parameters

The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.

Sol-Gel Spin Coating Synthesis of TiO₂Nanostructure and Its Optical Characterization

This work focuses on the sol-gel spin coating technique of TiO2 nanostructure synthesis and its characterization. Though various methods have been used to fabricate TiO2 nanostructure, much effort has not been exerted to achieve better photoresponsive and narrowly dispersed TiO2 nanostructure using the sol-gel spin coating method. Therefore, it is imperative to realize the synthesis of TiO2 nanostructures, and investigate their properties. In this work, TiO2 is synthesized by sol-gel spin coating technique using titanium tetraisopropoxide, isopropanol, acetic acid and deionized water as starting materials and deposited on borosilicate glass substrates. The effects of annealing temperatures (300˚C, 400˚C and 500˚C) on the structural and optical properties of the films were investigated by different techniques: Scanning Electron Microscopy (SEM), optical microscopy and UV-visible spectrophotometry. The optical characterization showed the direct band gap at 3.7 eV, 3.6 eV and 3.4 eV for 300˚C, 400˚C and 500˚C, respectively, and the optical transmittance and reflectance spectra showed a greater performance at 500˚C. The grain sizes obtained from SEM annealed at 300˚C, 400˚C and 500˚C are found to be about 6.0 nm, 5.0 nm and 4.0 nm respectively. The grain size of TiO2 nanostructure films decreased with increasing annealing temperatures. The results clearly indicated that the sol-gel spin coating synthesis of TiO2 nanostructure and post-thermal treatment at 500˚C cooled naturally at room temperature result in better photoresponsive and narrowly dispersed TiO2 nanostructure films with higher photoresponsive and good optical properties.

Microstructural Characteristics and Wear Performance of Plasma Sprayed Al_2O_3-13 wt. % TiO_2 Coating on the Surface of Extrusion Wheel

The conventional Al2O3-13 wt. % TiO2 composite ceramic coatings are fabricated by plasma spraying on the surface of extrusion wheel. The microstrueture, morphology and phase compositions of the substrate and coat- ing are investigated by using X-ray diffractometry （XRD） , scanning electron microsopy （SEM） and energy dis- persive spectroscopy （EDS）. Moreover, the microhardness of the substrate and the coating are investigated using Vickers mierohardness tester, the friction and wear behaviors of the substrate and the coating are investigated by using a block-on-ring tribometer under dry sliding conditions with the load of 245 N. The results show that both γ-Al2O3 and α-Al2O3 phases are observed in the as-sprayed coatings, the mian phase is γ-Al2O3. There are white particulates Al2O3 on its surface. The Al2O3-13 wt. % TiO2 coating possesses higher mierohardness which is about 1018HV and 1.6 times that of the substrate. The wear performance of coating is better than that of the substrate. In a practical application, the life of the extrusion wheel which is plasma sprayed Al2O3-13 wt. % TiO2 coating on the surface is 1.2 times that of the conventional extrusion wheel, and the life is about 330 h.

Non-UV based germicidal activity of metal-doped TiO_2 coating on solid surfaces

A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity. A Baclight dead/live bacteria viability kit （invitrogen, molecular probes） was used for staining the cell. The screening was carried out following a standard procedure. This included loading cell suspension to solid surface and maintaining contact for 30 min, then staining with a mixture containing dyes. The stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV. Metal-doped TiO2 coatings on AI plates were prepared and tested for non-UV germicidal activity without using UV. It was tested using model microorganisms such as Bakers Yeast （Saccharomyces cerevisiae）, Bacillus subtilis, Pseudomonas putida, and Escherichia coli. On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells, the stained cells may appear green （viable）, green with red or yellow nuclei and yellow （compromised） or red （nonviable）. According to their stained color, cells were counted to calculate the percentage of dead, live, and compromised cells. Compromised cells are cells that grow very slowly after reculturing indicating a degree of reversible cell damage. Screening the germicidal activity using this staining method is accurate and efficient, and requires less time than the culture-based method. A modification to the procedure for measuring germicidal activity of rough surfaces or fibrous coatings was developed. Both TiO2 and metal-doped TiO2 （Ag, Pt, Au, Cu） possess non-UV based germicidal activity. The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation before testing. It is not greatly affected by contact time, indicating a fast acting germicidal activity.

Influence of TiCl_4 treatment on performance of dye-sensitized solar cell assembled with nano-TiO_2 coating deposited by vacuum cold spraying

Titanium tetrachloride (TiCl4) treatment was employed to TiO2 coating deposited on fluoride-doped tin oxide (FTO) conducting glass and indium oxide doped tin oxide (ITO) conducting glass, respectively. The nano-crystalline TiO2 coating was deposited using a composite powder composed of polyethylene glycol (PEG) and 25 nm TiO2 particles by vacuum cold spraying (VCS) process. A commercial N-719 dye was used to adsorb on the surface of TiO2 coating to prepare TiO2 electrode, which was applied to assemble dye-sensitized solar cell (DSC). The cell performance was measured under simulated solar light at an intensity of 100 mW·cm-2. Results show that with an FTO substrate the DSC composed of a VCS TiO2 electrode untreated by TiCl4 gives a short-circuit current density of 13.1 mA·cm-2 and an open circuit voltage of 0.60 V corresponding to an overall conversion efficiency of 4.4%. It is found that after TiCl4 treatment to the VCS TiO2 electrode with an FTO substrate, the short circuit current density of the cell increases by 31%, the open-circuit voltage increases by 60 mV and a higher conversion yield of 6.5% was obtained. However, when an ITO substrate is used to deposit TiO2 coating by VCS, after TiCl4 treatment, the conversion efficiency of the assembled cell reduces slightly due to corrosion of the conducting layer on the ITO glass by TiCl4.

Sol-gel Derived TiO_2-Bioactive glass-Hydroxyapatite Bioactive Coating on Titanium Alloy Substrate

Coating the hydroxyapatite （HA） on the titanium alloy surface can obtain a bioactive implant with high mechanical properties However, the bonding force between the titanium alloy and the HA was low due to their different coefficient of thermal expansion （CET）. Preparing the multi-layer coating with alleviated thermal stress on titanium alloy substrate is few reported. Fabrication of a TiO2-bioactive glass （BG）-HA bioactive coating was proposed to solve this problem. A particular TiO2 surface was prepared on the titanium alloy substrate by micro-arc oxidation treatment. The BG and HA coating were coated onto the TiO2 surface in turn by using a sol-gel method. The microstructure, surface morphology and phase composition of the coatings were analyzed. The bonding force of coatings was investigated by the nick apparatus. In vitro dissolution was performed by soaking the TiO2-BG-HA coated samples into the simulated body fluid for various periods. Micro-structural observations indicated that no delamination and crack occurred at the interface of HA/BG and BG/TiO2. The bonding between the substrate and coating consists of the mechanical interaction and the chemical bonding. The bonding force could reach about 45 N. The TiO2-BG-HA coating displayed the excellent forming ability of bone-like apatite when it was soaked into the simulated body fluid. This work suggests an innovative way to reduce the internal stress among coatings through varying BG composition to adjust its CTE, so as to enhance the bonding force.

Comparison of electrochemical properties of atmospheric pressure plasma coatings for Al_2O_3-3TiO_2 and CoNiCrAlY in sea water

To improve the durability of underwater rotating products,the corrosion characteristics in harsh marine environment were evaluated through various electrochemical experiments on the Al2O3-3TiO2 and CoNiCrAlY coating layers by atmospheric pressure plasma spray coating process.By evaluating the corrosion resistance of these materials,their applicability to environmentally friendly power generation equipment such as blades of tidal current turbines was examined.According to the Tafel analysis for micro-areas including the coating layer,the coating/metal interlayer and the base metal,the Al2O3-3TiO2 coating layer and the CoNiCrAlY coating layer show markedly lower corrosion current density than the base metal.The corrosion current density of the CoNiCrAlY coating layer (9.75316×10-8A/cm2) is about 1.6 times more than that of the Al2O3-3TiO2 coating layer (6.13139×10-8A/cm2).

Self Assembly of Honeycomb TiO₂Coatings by Tea-Leaf Extracts as the Dispersoids

Photo catalytic TiO2 coatings with well defined honeycomb structure were successfully self-assembled on glass substrates by a simple “dip and burn solgel method“. The crux of this new method is that the starting material for the sol-gel coating (the water solution of ammonium titanium citrate) was “doped” with “tea-leaf extracts”. Tea-leaf extracts were completely dissolved in the water solution of ammonium titanium citrate and nucleate uniformly during the drying procedure of the coating precursor formation. This uniformly dispersed nucleation of the “tea-leaf extracts (tannin, catechin…)” were extracted during calcinations and leaving honeycomb-cell like nano-structure in the TiO2 coatings. Self-assembled cells were uniformly distributed in the TiO2 coatings and the diameter of the cells was in the range of 200 - 1000 nm. Fine honeycomb structures were clearly observed with microscopic observations.

电沉积HA/TiO_2复合涂层的结合强度和热稳定性研究

HA/TiO 2 composite coating were fabricated via adding TiO 2 powder in the electrolyte by electrodeposition.The influence of current dens ity and deposition time on the content of TiO 2 in the coating,the influence of the content of TiO 2 in the coating on the bonding strength of coating and the influence of sinte ring temperature on the structure and the bonding strength of coating were inves tigated.The experiment results show that the content of TiO 2 in the coating increase with reducing the current density and prolonging the deposition time,the bonding strength improve with increasing the content of TiO 2 in the coating,which can obtain18.7MPa when the weight percent TiO 2 in the coating attain72.2%.The addition of TiO 2 in the coating reduces the thermal expansion co - efficient of the coating,improves the bonding strength of coating and change s the fracture mechanism of the coat - ing from adhesion failure to cohesive failure.HA in the composite coatings i s decomposed by the catalysis reac - tion of TiO 2 at the temperature of sinter850 ℃ .Differential scanning calorimetry and X - ray diffractometry analy - ses showed that the chemical reaction between HA and TiO 2 lead to the product are α- TCP and CaTiO 3 at the temperature of sinter1200 ℃ .In order to prevent the coating from decomposing and attain hign bonding st rength,the sintering temperature should be less than820 ℃ .

射频磁控溅射TiO_2/HA复合生物膜的制备与表征

将水热合成的羟基磷灰石(HA)粉与20wt%Ti粉混合,冷压烧结成靶材。采用射频磁控溅射方法,在工业纯钛基体上沉积TiO2/HA生物薄膜,通过扫描电镜(SEM)及其能谱(EDS)、X射线衍射(XRD)和差热分析仪(TDA)对膜层进行了表征,探讨了溅射膜的晶化工艺。结果表明:由于选择溅射和OH-损失,溅射膜由TiO2晶体颗粒和非晶钙磷化合物组成,且其Ca/P比降低。经700℃,0.5h水蒸气处理,非晶钙磷化合物结晶度大大提高,并部分转化为HA晶体,且处理后的溅射膜与基体间无裂纹。

具有多孔结构的HA/TiO_2生物材料的制备工艺研究

以聚氨酯为造孔支架模板,采用有机泡沫法与高温烧结法,制备了多孔HA/TiO2陶瓷支架材料。讨论了烧结保温时间、PVB含量、TiO2含量等对材料结构与性能的影响。研究表明:较佳的烧结工艺为1 200℃烧结3 h,烧结后样品主要是HA、TiO2相。多孔HA/TiO2陶瓷拥有大孔径300～1 000μm,也有50～300μm的小孔径,具有较好的孔连通性与孔结构,有利于细胞和组织的生长以及营养输送。TiO2具有增强效应,其含量增加,材料压缩强度提高,但TiO2含量过高会增加其脆性,最佳含量为5%,此时材料力学性能接近于人体松质骨。

Parameter Optimization of Amalgamated Al2O3-40% TiO2 Atmospheric Plasma Spray Coating on SS304 Substrate Using TLBO Algorithm

SS304 is a commercial grade stainless steel which is used for various engineering applications like shafts, guides, jigs, fixtures, etc. Ceramic coating of the wear areas of such parts is a regular practice which significantly enhances the Mean Time Between Failure (MTBF). The final coating quality depends mainly on the coating thickness, surface roughness and hardness which ultimately decides the life. This paper presents an experimental study to effectively optimize the Atmospheric Plasma Spray (APS) process input parameters of Al2O3-40% TiO2 ceramic coatings to get the best quality of coating on commercial SS304 substrate. The experiments are conducted with a three-level L18 Orthogonal Array (OA) Design of Experiments (DoE). Critical input parameters considered are: spray nozzle distance, substrate rotating speed, current of the arc, carrier gas flow and coating powder flow rate. The surface roughness, coating thickness and hardness are considered as the output parameters. Mathematical models are generated using regression analysis for individual output parameters. The Analytic Hierarchy Process (AHP) method is applied to generate weights for the individual objective functions and a combined objective function is generated. An advanced optimization method, Teaching-Learning-Based Optimization algorithm (TLBO), is applied to the combined objective function to optimize the values of input parameters to get the best output parameters and confirmation tests are conducted based on that. The significant effects of spray parameters on surface roughness, coating thickness and coating hardness are studied in detail.

溶胶-凝胶/微弧氧化复合制备种植体表面HA/TiO_2复合涂层的研究

目的:探讨微弧氧化和溶胶-凝胶复合方法对钛种植体进行表面改性研究,在提高耐磨性、耐腐蚀性的同时,改善材料的生物活性。方法:利用微弧氧化和溶胶-凝胶复合方法在钛种植体表面制备羟基磷灰石(hydroxyapatite)HA/TiO2复合涂层,用扫描电镜(SEM)观察陶瓷膜层的表面形貌,用χ射线衍射(XRD)仪和X射线能谱(EDX)分析膜层的成分和元素分布。并对材料表面粗糙度的变化和涂层结合力进行检测。结果:形成的复合涂层由内层表面多孔的TiO2层和外层的HA层构成。HA/TiO2复合涂层与基体的结合强度约为(30±2.5)N,同时复合涂层提高了材料的表面粗糙度。结论:采用微弧氧化和溶胶-凝胶复合的方法可在钛种植体表面制备HA/TiO2复合涂层,初步研究表明该涂层具有较好的结构和生物活性。

钛表面含银HA／TiO2复合微弧氧化膜的初步制备

本文利用微弧氧化技术，在钛基体表面制备了含银的HA／TiO2膜层，所用电解液由磷酸二氢钠（NaH2PO4·2H2O）、醋酸钙（CH3COO）2Ca·H2O）和氧化银（Ag2O）组成。分别利用扫描电子显微镜（SEM）、能谱仪（EDS）及X射线衍射仪（XRD）对膜层的表面及断面形貌、膜层元素组成及膜层相结构进行了分析。结果显示，所制备的微弧氧化膜主要由Ca、P、Ag、O和Ti几种元素组成，其相组成主要为金红石和锐钛矿型的二氧化钛，并含有羟基磷灰石。膜层中Ag元素的加入，使所得膜层除了可具有羟基磷灰石的生物活性外，还有望具有良好的杀菌作用。

Structural and optical properties of nano-spin coated sol-gel porous TiO_2 films

Three thicknesses of TiO2 films, 174, 195, and 229 nm, were deposited onto quartz substrates by sol–gel spin coating method. The as-deposited thin films were characterized by nano-crystallite with different sizes (19–46 nm) and relatively high porous structure. Optical constants were determined and showed the lowest refractive index of 1.66 for the as-prepared films that ever reported till now. Obtained results were discussed through current theoretical ideas.

离心成型技术制备TiO2/HA复合材料的研究

采用离心成型技术制备TiO2/HA复合材料,研究了固相质量分数、TiO2质量分数对TiO2/HA浆料粘度的影响,分析了离心转速和浆料固相含量对生坯密度均匀性的影响,观察并测试了烧结产物的显微组织、物相组成以及抗弯强度。研究结果表明:低固相含量浆料离心后顶部和底部生坯密度差异较大,随着离心力增加,这种差异变得更加明显。但是当浆料固相含量超过为50wt%时,高粘度的浆料降低了生坯密度梯度。提高烧结温度和TiO2含量都有助于增加TiO2/HA复合材料的抗弯强度。当TiO2含量为7wt%,1150℃烧结2 h后,TiO2/HA复合材料烧结密度98.5%,抗弯强度是82.5 MPa。

Effect of Nano Size TiO₂Particles on Mechanical Properties of AWS E 11018M Type Electrode

Addition of nano size particles of TiO2 in the coating of shielded metal arc welding electrode (E 11018M) partially substituting the conventional micro size TiO2 was studied for possible enhanced electrode characteristics. The results show that the nano size particle of TiO2 improved recovery of elements such as Mn, Ni, Mo, Ti etc. as well as increased all-weld-metal tensile and charpy impact properties at –51℃. Furthermore, the charpy impact properties were found to be very sensitive to variations in Ti content of the weld deposit.

Sensitive and Reproducible Photocatalytic Activity Evaluation Instrument for Transparent Coatings

A new photocatalytic activity (PC) measurement instrument based on the measurement of the photo-induced reduction of Ag ions was proposed. The feature of this system is to perform “ultraviolet irradiation for PC activation” and “Ag film thickness determination for PC evaluation” simultaneously and automatically. Realizing a PC measurement system with high sensitivity, wide dynamic range, easy operation and reproducibility, which is especially suited for the PC measurement of the coatings on transparent substrates.

Carboxylic Acids and Esters as Scaffold for Cavities in Porous Single Layer Anti-Reflective Coatings of Silica-Titania with Excellent Optical and Mechanical Properties

Anti-reflective (AR) single layer of silica-titania (SiO2-TiO2) coatings were obtained from sols containing pyromellitic dianhydride (PMDA) derivatives and Ti and Si precursors on glass substrate by dip-coating method. The coatings showed very high optical quality and the transmission was improved to up to 98.5%. Furthermore, the coatings also presented good mechanical stability.

TiO_2/SnO_2复合光催化剂的制备及光催化降解敌敌畏

以 Sn Cl4· Ti( OBu) 4、氨水、乙醇为原料 ,采用活性层包覆法 ,制备出 Ti O2 / Sn O2 复合光催化剂 ,并用IR、XRD、TEM和 BET等手段对样品进行了表征 .研究其对有机磷农药敌敌畏的光催化降解效果 ,与单一半导体催化剂 Sn O2 、Ti O2 做了简单对比 .结果表明 :所制 Ti O2 / Sn O2 样品为包覆型结构 ,由锐钛矿型 Ti O2 金红石型 Sn O2 组成 ,与 Sn O2 及 Ti O2 晶体粉末相比所制 Ti O2 / Sn O2 包覆粒子光催化活性得到明显提高 .