Materials Science Forum Vols. 610-613

Abstract: Nano-TiO2 synthesized by hydrolysis of TiCl4 demonstrated high reactivity in presence of peroxide hydrogen under visible light (λ>420nm).The nano-TiO2 powders were characterized by XRD, Uv-Vis, FT-IR. The results showed that the TiO2 nanocatalyst sensitized with peroxide hydrogen could absorb visible light up to 550nm, and Vis absorption could be extended to 600 nm for the sulfated TiO2 .Photocatylytic degradations of methyl orange and methylene blue were above 90% for sulfated TiO2 in 180min. The inorganic sulfate species absorbing on the surface of titania were mainly responsible for the high activity of the TiO2 under visible light regions．

Abstract: Pure rutile TiO2 nanorod-assembled microspheres were synthesized on a large scale without templates or surfactants by hydrolysis of TiCl3 in ethanol and HCl mixed solution at 180°C.The spheres exhibit unique three-dimensional hierarchical architectures with significantly improved photocatalytic activities in visible light.

Abstract: Active oxygen species generated from semiconductor under irradiation play an important role in decomposing and mineralizing pollutants and undesirable compounds in the air and waste water. The production of superoxide anion (O2－) and hydroxyl radical (•OH) generated in the suspension of zinc oxides with different morphologies and particle sizes were studied in the present paper. Three kinds of zinc oxides, which named tetra-needle like ZnO (T-ZnO) whisker with length of 10~20 μm and basal diameter of 1~3 μm, nanosized ZnO (n-ZnO) with particle size of 20~30 nm and commercial ZnO powder (p-ZnO) with particle size of ~1 μm, respectively, were used in this work. Nitroblue tetrazolium (abbr. NBT) was used to determine the amount of super oxide anion generated from the related zinc oxides, in which NBT can be reduced to insoluble purple formazan by super oxide anion. The amount of hydroxyl radicals was determined by detecting the decreased absorption intensity of Fe(phen)32+ (complex of iron (II) with 1,10-phenanthroline) at 510 nm with UV-Vis spectrophotometer. The results indicated that the most amounts of superoxide anion and hydroxyl radical were detected in T-ZnO whiskers and n-ZnO respectively. The difference between the production amount of superoxide anion and hydroxyl radical can be attributed to the different mechanisms for both of the production and transportation of these two kinds of active oxygens.

Abstract: Cerium oxide nanoparticles with sphere-like in shape were synthesized by precipitation method, using cerium nitrate as raw material and ammonium acid carbonate as precipitation agent. Effects of reactant concentration, supersonic wave and dispersant agent on properties of the cerium oxide particles were investigated. Experimental results showed that the dispersant agent played important roles on the size of resulting particles. Besides, supersonic wave prevented the precipitate from agglomerateing partially.

Abstract: Single crystal rutile TiO2 microfibers have been synthesized by hydrothermal method using TiCl3 as titanium source. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal that the microfibers with average diameter of 15 μm and length of 1~2 mm are self-assembled by single crystal TiO2 nanorods and well-dispersed. The bandgap Eg of microfibers is about 3.0 eV by UV-vis adsorption spectrum.

Abstract: Films of linear-low density polyethylenes, made from metallocene catalyst and Ziegler-Natta catalyst , were exposed to accelerate photo-oxidation conditions. The investigations were focused on the changes of the physical and chemical structures and elongation at break occurring in the photo-oxidation process. The results showed that ethylene-hexene m-LLDPE was more favorer to photo-oxidize than ethylene-octene LLDPE. The other two ethylene-ocetene m-LLDPEs were comparable to LLDPE with the same comonomer. The oxidation rate of LDPE is slower than those of all the LLDPEs.

Abstract: (0-2%) Fe-doped TiO2 nanopowders were prepared by sol-gel method. The Size, structure, appearance, the light absorption and hydroscopicity properties were characterized by XRD, TEM, UV-Vis and FTIR. The photocatalytic degradation of crystal violet under UV over catalyst was used as a probe reaction to evaluate their photocatalytic activity, the dependence of photocatalytic properties on Fe doping content and roasting temperature were also discussed. The results show that the process of phase transfer of TiO2 from anatase to rutile was promoted by doping Fe, 1.5% Fe3+-doped TiO2 nanoparticles formed many defects at grain boundaries, inhibited effectively the recombination of the photoproduced e-/h+, improved the efficiency of photons, enhanced the absorbing water function of catalyst, and 1.5% Fe3+-doped TiO2 revealled strongly absorption in UV and widened obviously absorption in Vis. Photocatalytic degradation ratio of crystal violet (4mg/L) on 1.5% Fe3+-doped TiO2 was increased 30% than pure TiO2.

Abstract: Cobalt- superhard high speed steel layer has been formed on the surface of low alloy steel 20Cr2V by tungsten-molybdenum-cobalt plasma surface alloying and following plasma carbonizing. After plasma surface alloying, a homogeneous and dense surface alloying layer was formed, thickness of which is 200μm. Composition, microstructure and properties of the alloying layer were investigated. Contents of W, Mo, Co, Cr, V and C in the surface layer reach 8%,5%, 6% ,4%,1.5% and 1.5% or so respectively. The concentrations of alloy elements basically meet the requirements of high cobalt type superhard high speed steel. Constituent phases of the surface layer were martensite, M7C3 ,M2C and Cr3C2 carbides and μ phase after quenching treatment. The advanced gradient superhard high speed steel possesses not only high surface hardness, high anti-temper softening ability but also enough toughness.

Abstract: In this article, Sm(Sal)xPhen, SmyY1-y(Sal)3Phen were synthesized and its films were prepared. They were characterized by infrared spectra (IR), ultra-violet visible spectrometer (UV), X-ray diffraction (XRD) and fluorescence spectroscopy. Sm/Y complexes and its mixture doped with the polyvinyl alcohol (PVA) showed photoluminescence at the wavelength of 646 nm. There was an excellent compatibility among Sm/Y complexes, the polyvinyl alcohol (PVA) and dimethyl sulphoxide (DMSO), which were used to prepare the resin film. The results indicated that Sm/Y rare earth light conversion films were better light conversion films with good compatibility in resins, and with emission wavelength suitable for plants’ photosynthesis.

Abstract: In this paper, silicon carbide materials bonded with superfine SiO2 powder were produced using silicon powder, superfine SiO2 powder and different grain grade silicon carbide as raw materials. At the condition of the same content of silicon powder, the effect of the superfine SiO2 powder content on properties of silicon carbide materials after sintered at 1450°C for 3 h in air atmosphere was studied by means of SEM and other analysis methods. The results showed that silicon powder contributes to both sintering by liquid state and plastic phase combination to improve the strength of samples. When the superfine SiO2 powder content is lower than 3.5%, the density and strength of samples increase and porosity decrease with increasing superfine SiO2 powder content. However when the superfine SiO2 powder content is higher than 3.5%, the density and strength of samples decrease and porosity increase with increasing superfine SiO2 powder content. At the same time, sample with 3.5% superfine SiO2 powder has the best oxidation resistance property at 1100°C.