Materials Science Forum Vols. 809-810

Abstract: The present work was dedicated to the tailored synthesis of TiO₂ nanopowders doped with nitrogen (called TiO_2−xN_x ) for the photocatalytic degradation of methyl orange. In particular, the systems were synthesized by a sol-gel combustion route starting from nitric acid and tetrabutyl titanate (Ti (OC₄H₉)₄) as raw materials. The powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), suggesting that anatase phase is obtained at pH value of 4-6 and the heat-treated temperatures as low as 425°C. The photocatalytic activities of the N-doped TiO₂ nanopowders were monitored from the results of the degradation rate of methyl orange (MO) under solar light irradiation. The dependence of dye degradation rate on photocatalyst amount and initial pH was investigated. Under solar light irradiation, the TiO₂ doped with 30% N exhibited the highest photocatalytic reactivity, which could be attributed to the structure of the combustion-synthesized catalyst and the change of the bandgap induced by nitrogen inclusion.

Abstract: In this paper, reporting a new way to directly prepare quality of carbon materials such as artificial graphite, like-graphitization carburant and senior carbonaceous reductant et al ,which is prepared from anthracite under ultra-high temperature without any other additional process and catalyst. The chemical composition of carbon materials was analysed ; the electrical resistivity was tested; the composition of phase and the graphitization degree was tested by XRD; the microstructure was characterized by SEM and the degree of crystallization and crystal defect was characterized by the Raman diffraction spectrum. At the same time, the graphitization method was discussed during ultra-high temperature. The results show that good carburant and carbonaceous reductant can be prepared by anthracite which was graphitization under ultra-high temperature ;The microstructure of carbon materials which was prepared by anthracite that was graphitization during ultra-high temperature is more ordered than that of raw anthracite, its graphitization degree also increase significantly; When the ultra-high graphitization temperature is above 2600 °C, carbon materials which is like to pure graphite have a small amount of structural defects and distortion; the high quality carbon materials prepared by graphitization method under ultra-high temperature ,it is a simple process with low cost and high added value, and its prospects of application is broad.

Abstract: Anthracite and bitumite were processed respectively at 1400°C,1700°C, 2000°C, 2200°C, 2400°C and 2600°C,and their chemical composition,resistivity,microstructure, phase composition,and the internal migration of molecular functional group were tested and characterized. The results indicate that moisture, ash and volatile in coal have gradually shifted and lost with the elevation of heat treatment temperature, while the higher temperature, the quicker and completer phase change. Heat treatment can make the coal transform from approximately insulative phase to conductive phase,. Furthermore, as the temperature increases, the conductive phase transformation effect is better. The higher the heat treatment temperature of coal, the more amorphous carbon transforming into crystalline carbon completely, but the less types of phases .

Abstract: The electrochemical behavior of vanadium solution containing V (III) and V (IV) ion each 50% was characterized by cyclic voltammetry and chronopotentiometry with different working electrodes, temperatures, H₂SO₄ concentrations and vanadium ion concentrations. Cyclic voltammetry analysis indicated that V(IV)/V(V) redox reaction at graphite electrode showed good electrochemical activity and reversibility while V(III)/V(II) redox reaction showed bad electrochemical activity and reversibility on Pt, glassy-carbon and graphite electrode. The cathodic peak current density of V(III)/V(II) couples increased first then remained almost unchanged as temperature raised and approached a maximum at 60°C. With H₂SO₄ concentration elevated, the electrolyte became viscous and diffusion step was the controlling step. The electrochemical activity of electrolyte increased with ascending vanadium concentration, so did the reversibility of V(IV)/V(V) couples. However, no matter what vanadium concentration was, the reversibility of V(III)/V(II) couples stayed poor. Stirring in solution benefited to the anodic peak current density of V(IV)/V(V) couples whereas it did not to the cathodic peak current density of V(III)/V(II) couples. The diffusion coefficients of V(III),V(IV) were calculated as 1.17×10^-5,0.919×10^-5 cm²·s^-1 , respectively. Chronopotentiometry test indicated that solution as anolyte showed good charging performance while solution as catholyte showed poor charging performance.

Abstract: TiO₂ photocatalysts doped with different element of C and Y were synthesized by sol-gel process using glucose, yttrium nitrate and tetrabuty ltitanate as precursors. Samples characterized by XRD, XPS, TEM, PL and UV-Vis methods. The photocatalytic activity of samples was investigated by photocatalytic degradation of methylene-blue (MB) under the irradiation of fluorescent lamp. The results indicate that C ion and Y ion are incorporated into the lattice of TiO₂, and C doping accelerate phase transition from anatase to rutile phase, but Y doping inhabits the phase transition. It was also found that both C and Y doping can broaden the absorption spectrum to visible light region and inhibit the recombination of the photo-generated electron and hole pairs. The synergy effect of co-doped C and Y ions provides C-Y-TiO₂ sample better photocatalytic activity than that of the single-doped samples and P25 under fluorescent lamp. The photocatalytic activity of the sample with C, Y co-doped is the best under the irradiation of fluorescent light. It is 94.23% within 3 hours and significantly higher than that of Degussa P25 (44.72%) under the same experimental conditions.

Abstract: Li₃V₂(PO₄)₃/C is prepared by sol-gel combined with ball milling method (SG-BM). The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), C-S analysis and galvanostatic charge/discharge measurements. The structural characterization shows that the composite prepared by SG-BM is composed of the well crystallized Li₃V₂(PO₄)₃ with the space group P21/n and 6.2 wt.% amorphous carbon. SEM and TEM results show that the prepared composite has uniform size distribution with the narrow range of 0.5-1.5μm, and its surface is covered by a smooth and uniform carbon layer with thickness of about 10nm. Galvanostatic charge/discharge measurements indicate that the composite exhibits high rate capability and excellent cycling stability. The prepared composite delivers a discharge capacity of 131.1mAh/g, 128.9mAh/g, 122.6mAh/g and 113.8mAh/g at 0.5C, 1C, and 10C, respectively. The capacity retention of 100% is achieved after 50 cycles at 1C. This outstanding electrochemical capability is attributed to the ultrafine particles with narrow size distribution and the well-covered carbon layer with proper thickness.

Abstract: The present work reviewed the recent development of preparing LiFePO₄ materials. Solid state method, liquid state method and some rising method were included. The advantages and disadvantages of different methods were compared. And research direction and developing prospect of LiFePO₄ material were pointed out.

Abstract: The multicrystalline silicon wafers purified by directional solidification route were used to introduce copper impurities. The resistivity and minority carrier lifetime of multicrystalline silicon wafers were investigated by four-point probe resistivity tester and μ-PCD, respectively. Annealing temperature, atmosphere and cooling rate were researched. It was found that copper contaminants have a greater impact on the electrical properties of multicrystalline silicon. Research results showed that copper impurities tend to exist at defect sites at high temperature, and high annealing temperature, argon atmosphere and slow cooling conditions make more impact on the electrical properties of multicrystalline silicon than low annealing temperature, air atmosphere and fast cooling.

Abstract: Methods such as processing of ilmenite concentrate by impregnation and roasting, several kinds of CWAO system mineral catalyst is prepared. And to explore under certain conditions of phenol in waste water of phenol removal rate, compare several kinds of preparation methods of catalysts. Studies show that the effort of 723 K calcined after partial acid salt dipping made catalyst is best. Under the condition of 100 r/min at 303K, the 10 mg/L of phenol removal rate can reach more than 98%.

Abstract: A intercalated TiO₂ photocatalyst loaded bentonite was prepared by sol-gel method. The effect of reaction time, reaction temperature,the amount of butyl titanate and other process parameters on prepared material of degradation of methyl orange,as well as the relationship between the concentration of methyl orange on degradation process and illumination time were discussed by single factor method.The results showed : the first absorbance of the intercalated TiO₂ photocatalyst loaded bentonite material was 0.342 and the average absorbance was respectively 0.7402 through 5 washing after the intercalated TiO₂ photocatalyst loaded bentonite irradiated at UV-irradiation 1.5h to 20mg/L methyl orange.