Advanced Materials Research Vol. 650

Abstract: The Ag/TiO₂ powders with different Ag contents were synthesized with tetrabutyl titanate as a titanium source and silver nitrate as silver source by sol-gel method, and the Ag contents in the Ag/TiO₂ powders were 0.1%, 0.3%, 0.5 %, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, and 4% (mole ratio) respectively. Meanwhile, Rhodamine B was used as target degradant to value the photocatalytic activity of Ag/TiO₂ powders, the effects of Ag contents, the calcination temperature and calcination time on the photocatalytic activity were disscussed The results show that catalytic activity of the Ag/TiO₂ powders prepared with the Ag content of 2%, calcination temperature of 450 °C and calcination time of 2 hours exhibited the best photocatalytic activity, which was ascribed to the abundant electron traps in favor of the separation of the photoinduced electron-hole pairs.

Abstract: TA15 titanium alloy thick-wall parts have been deposited by Laser rapid forming (LRF) process. In this paper, a new overlap method between two adjacent laser tracks has been used to deposit the thick-wall titanium part. Results showed that the LRFed thick-wall titanium part was good in shape by using the new overlap method. The microstructure of the LRFed titanium alloy primarily consists of columnar prior-beta grain, which is perpendicular to the substrate resulting from directionally solidification. It also could be observed that the size of alpha phase increased with increasing laser power and decreasing scanning velocity. Tensile properties of LRFed titanium was slightly lower than that of the wrought annealed TA15 titanium alloy, after the heat-treatment of 940°C/1h/AC, the heat-treated titanium alloy showed good tensile properties which were equivalent to that of the wrought annealed TA15 titanium alloy.

Abstract: Titanium oxide is believed as one of the key factors that influence the excellent corrosion properties as well as biocompatibility of titanium alloy. In the present research, thermal-electrochemical anodizing processes were performed in order to form thick layer of titanium oxide on titanium alloys (Ti6Al4V) surface. Oxidation temperature, blasting and anodizing voltage were selected as the evaluated parameters process at the present study. It was observed that temperature plays important role in the formation of oxide layer, where the thickness of the oxide increases significantly as temperature increases. However, for the case of oxide layer formed by thermal oxidation at temperature of 950oC, oxide layer on the non-blasted sample become easily peel off, whereas oxide layer on the blasted sample shows good adhesion properties. In addition, oxide layer on the blasted samples also have thicker layer as compared with oxide on the non-blasted sample. On the other hand, it was observed that further oxidation by anodizing at 43V and 63V create finer oxide layer by the filled up of porosity on the existing oxide layer. However decreasing of oxide layer thickness was also observed after anodizing, which is predicted due to the breaking up the outer oxide layer during anodizing process.

Abstract: Atomic layer deposition (ALD) is utilized to grow high performance zinc oxide (ZnO) thin films, where the effects of ALD process temperature on the thin film properties are also studied in this work. Some major properties of the ALD ZnO films are characterized and compared with those of sputtered ZnO films. Significant differences are observed that the electrical resistances of the ALD ZnO films are largely improved, while the optical transmittances also increase. Nevertheless, the adhesion and mechanical properties of the ALD films are worse than the sputtered films because of the weak bonding in the ALD process. For various substrate temperatures, the ALD ZnO films with 200°C behave the best performance.

Abstract: In order to change the single color of wood surface after chemical plating, this study conducts the surface chemical plating Ni, then in the containing ammonium molybdate solution for staining. The content of Mo is 4.09% when the wood surface displays purple; the content of Mo is 8.65% when the wood surface displays yellow; the content of Mo is 25.26% when the wood surface shows rainbow; the content of Mo is 40.92% when the wood surface shows pink; the content of Mo is more than Ni when the wood surface displays black; besides, after different time, there are purple, yellow, rainbow, pink, black, which can be seen. Mo, Ni, P form multilayer film thickness, which has an effect on the optical transmittance.

Abstract: An ab initio B3LYP-DFT/6-311G(3df) study has been performed for the stability, structural and electronic properties of forty Zn_m O_n (m + n = p = 2 to 4) nanoclusters. We also consider the zero point energy correction. The nanoclusters containing large number of strongly electronegative O atoms for p = 3 and 4 are found to be most stable as compared to the other nanoclusters of the same configuration. The most stable clusters have linear or planer structures and not the three dimensional ones. The observed trend of decrease of the HOMO-LUMO gap with the size of the nanocluster is in conformity with the quantum confined behavior.

Abstract: The porous silicon samples were prepared with n(111) Si wafers by electrochemical polarization and their microstructures were characterized by high-resolution transmission electron microscopy (HRTEM). The DigitalMicrograph image processing was used to analyze the HRTEM images. The distorted Si (111) crystal plane was observed on porous silicon and could be distinguished with the Fourier transforming electron diffraction (ED) pattern. Grain boundaries were presented in the HRTEM images where the lattice fringes distortions took place. The anisotropy property could be preserved at a small location area because of the smaller nanocrystals in different directions appeared amorphous in the ED pattern at a larger range.

Abstract: Dye-sensitized solar cells (DSSCs) have been fabricated using a TiO₂ paste composed of mixtures of 25 nm and 250 nm TiO₂ particles at various ratios. A maximum energy conversion efficiency of 6.7% has been achieved using the DSSC, based on a TiO₂ layer composed of 40 wt% 25 nm and 60 wt% 250 nm TiO₂ particles. The short-circuit current density, open-circuit voltage, and filling factor of the cell were 12.95 mA, 0.82 V, and 0.63, respectively. The overall performance of the DSSCs based on TiO₂ layers composed using a mixture of two different sized particles is much better than that of either only 25 nm or only 250 nm TiO₂ particles. It is recognized that adding the larger particles to the small particles in the TiO₂ paste increases the dye absorption and light scattering effects of DSSC, resulting in a higher short-circuit current density and improved energy conversion efficiency.

Abstract: Highly efficient photocatalytic TiO₂ powders were prepared using a conventional ball mill with various milling times of 0, 12, 24 and 48 h. The photocatalytic activity of the prepared TiO₂ powders was evaluated using the decomposition rate obtained by methylene blue (MB) solution and acetic acid gas under UV light irritation. After 24 h milling, the particle size decreased from 555 nm to 122 nm without changing any of the crystal structure. The photocatalytic TiO₂ powders prepared by 24 h milling decomposed 94% of the methylene blue solution while the non-milled TiO₂ powders provided only 61% decomposition. After the removal of acetic acid gas, it took 1.5 h for the 24h-milled powders to decompose 100%, while the non-milled TiO₂ showed 73% decomposition with same UV illumination duration.