Effect of oxygen concentration and system geometry on the current-voltage relations during reactive sputter deposition of titanium dioxide thin films

Current-voltage relations at different magnetron sputtering systems and gas mixtures were studied during reactive sputter deposition of titanium dioxide thin films. The main goal of this work was to investigate the influence of reactive gas mixture (Ar + O₂) and system geometry on the electrical characteristics of the discharge. The geometries utilized were the conventional magnetron sputtering, hollow cathode magnetron sputtering and triode magnetron sputtering. A change in the system geometry leads to a change in the electric field distribution, which alters the working range of the discharge voltage and magnetron efficiency. It is noticed that the discharge voltage at constant current can be reduced when the geometry is altered from conventional magnetron to hollow cathode magnetron or triode magnetron, at the same time the magnetron efficiency is increased when hollow cathode magnetron or triode magnetron are used instead of conventional magnetron sputtering.     

Preparation of hollow TiC nanoparticles by the two-stage refluxing method

The two-stage refluxing method was applied to prepare hollow TiC nanoparticles. In this method, after refluxing the hydrous TiO₂ and ethanol, the precipitate and n-dedocane were refluxed to obtain the refluxing-derived precursor. The precursor was heat-treated at 1300 °C for 1 h and hollow TiC nanoparticles could be achieved. It is found that the pore size of the hollow TiC nanoparticles ranges from 3 to 76 nm and the mean pore size is 26.776 nm. The formation of the hollow structure is due to that the mesoporous channels of the precursor confine the carbide's growth inside it. In comparison with commercial TiC nanocrystals, the hollow TiC nanoparticles have higher specific surface area and pore volume significantly.     

Preparation of H-bar cross-sectional specimen for in situ TEM straining experiments: A FIB-based method applied to a nitrided Ti-6Al-4V alloy

The in situ tensile straining of cross-sectional specimens inside a TEM is intrinsically very difficult to perform despite its obvious interest to study interfaces of surface treated materials. We have combined a FIB-based method to produce H-bar specimens of a nitrided Ti-6Al-4V alloy and in situ TEM straining stage, to successfully study the plastic deformation mechanisms that are activated close to the nitrided surface in the Ti-based alloy.     

Influence of α morphology and volume fraction on the stress-induced martensitic transformation in Ti-10V-2Fe-3Al

This paper reports an investigation into the influence of α morphology and volume fraction on the critical stress levels for the stress-induced martensitic transformation in Ti-10V-2Fe-3Al. Control of the stress-induced martensite transformation offers a new route to the optimization of the load bearing capabilities of titanium alloys. Various heat treatments in α + β and β + (α + β) conditions were imposed to study their effect on both microstructure and mechanical properties. The results show that in samples with globular α, the β matrix stability is the main factor controlling the stress-induced martensitic transformation. For samples with acicular α, the “grain size” (i.e. the size of the retained β domain), which governs the mean length and the width of martensitic plates, also plays an important role in such transformations. The linear combination of both effects provides a good prediction of the stress-induced martensite formation stress as a function of the volume fraction and morphology of the α phase.     

Martensitic transformation and shape memory properties of Ti-Ta-Sn high temperature shape memory alloys

The effects of Ta and Sn contents on the martensitic transformation temperature, crystal structure and thermal stability of Ti-Ta-Sn alloys are investigated in order to develop novel high temperature shape memory alloys. The martensitic transformation temperature significantly decreases by aging or thermal cycling due to the formation of ω phase in the Ti-Ta binary alloys. The addition of Sn is effective for suppressing the formation of ω phase and improves stability of shape memory effect during thermal cycling. The amount of Sn content necessary for suppressing aging effect increases with decreasing Ta content. High martensitic transformation temperature with good thermal stability can be achieved by adjustment of the Ta and Sn contents. Furthermore, the addition of Sn as a substitute of Ta with keeping the transformation temperature same increases the transformation strain in the Ti-Ta-Sn alloys. A Ti-20Ta-3.5Sn alloy reveals stable shape memory effect with a martensitic transformation start temperature about 440 K and a larger recovery strain when compared with a Ti-Ta binary alloy showing similar martensitic transformation temperature.     

Effect of temperature on deformation behavior and microstructures of TC11 titanium alloy

The isothermal compression deformation behavior of TC11 titanium alloy with beta microstructure was studied between 750 °C and 1100 °C under the strain rate ranging from 0.001 s⁻¹ to 10 s⁻¹ by THERMECMASTOR-Z simulator. In addition, the effect of temperature on microstructure was observed using optical microscope. The results showed that the temperature greatly affected the flow stress and microstructure of TC11 titanium alloy cooled from beta phase region in air. During hot deformation of TC11 titanium alloy, the steady state flow characteristic was observed at higher temperature or lower strain rate. In the α + β phase region, spheroidization fraction of α lamellar decreased with increasing temperature, while in near-β and β phase regions, dynamic recrystallization fraction increased with increasing temperature in all strain rates except at the strain rate of 0.001 s⁻¹.     

炭包覆TiO2复合物对低浓度苯的光催化降解

通过将TiO2粉末和聚乙二醇混合,随后在氮气气氛下热处理合成了炭包覆TiO2.利用粉末X射线衍射、紫外-可见漫反射光谱、透射电子显微镜和氮吸附对炭包覆TiO2复合物样品进行了表征,并研究了其对浓度为～1.2×10-5苯的光催化活性.结果表明:炭包覆量受热处理温度和聚乙二醇用量的影响,随着温度的升高和聚乙二醇量的减少而减少;TiO2的结晶度随着温度的升高而提高,但是炭包覆对TiO2晶体的生长有抑制作用.炭包覆锐钛矿样品比纯TiO2表现出对苯更高的光催化活性,这是由于炭吸附作用导致锐钛矿颗粒周围的苯浓度增加以及包覆炭可导致电荷的有效分离;另一个原因是锐钛矿相结晶度的提高.因此,要获得对苯具有高光催化活性的炭包覆TiO2需要综合考虑碳含量和锐钛矿晶体结构.

Abstract：

Carbon-coated TiO2 was synthesized by mixing TiO2 powders and polyethylene glycol,followed by heat treatment in nitrogen atmosphere. All samples were characterized by powder X-ray diffraction,UV diffuse reflectance spectroscopy,high-resolution transmission electron microscopy,and nitrogen adsorption. The photocatalytic activity of carbon-coated TiO2 for benzene degradation was investigated with a benzene concentration of ～ 1.2 × 10-5. Results showed that the residual carbon content was influenced greatly by heat treatment temperature (HTT)and the amount of PEG,which decreased and increased with increasing the temperature and the amount of PEG,respectively. The crystallinity of TiO2 was improved when the HTT increased. However,the carbon residue had an inhibition effect on the crystal growth of TiO2. The carbon-coated anatase samples were shown to exhibit higher photocatalytic activities than the pristine TiO2 because of the adsorption enrichment of benzene by carbon around the anatase particles and of the effective charge separation due to the electronic conduction of carbon. Another important factor affecting photocatalytic activity was the crystallinity of the anatase phase. High photocatalytic activity for benzene requires a balance between the carbon content and the anatase crystalline structure.     

Reactivity of V2O5&z.sbnd;WO3TiO2 de-NOx catalysts by transient methods

The reactivity of ternary V₂O₅&z.sbnd;WO₃TiO₂ de-NO_xing catalysts with compositions similar to those of commercial catalysts (WO₃ ca. 9% w/w, V₂O₅ < 2% w/w) is investigated by transient techniques (temperature programmed desorption, TPD; temperature programmed surface reaction, TPSR; and temperature programmed reaction, TPR). The results indicate that the reactivity of the ternary catalysts in the SCR reaction increases on increasing the vanadia loading, and that the ternary catalysts are more active than the corresponding binary vanadia-titania samples with the same V₂O₅ loading. Indeed the SCR reaction is monitored at lower temperatures and high NO conversions are also preserved at high temperatures. TPSR and TPR data show that at low temperatures the SCR reaction occurs via a redox mechanism that involves at first the participation of the catalyst lattice oxygen and then the reoxidation of the reduced sites by gas-phase oxygen. Based on TPSR and TPR data, the higher reactivity of the ternary catalysts has been related to their superior redox properties, in line with previous chemico-physical characterisation studies. The catalyst redox properties thus appear as a key-factor in controlling the reactivity of V₂O₅&z.sbnd;WO₃TiO₂ de-NO_xing catalysts at low temperatures. The results also show that at high temperatures the surface acidity plays an important role in the adsorption and activation of ammonia.     

TiO2光催化抗菌材料

介绍了ＴｉＯ２光催化材料的抗菌与杀菌原理、特点及提高其杀菌性能的方法。并对其应用前景作了简要评述。     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.