Materials Science Forum Vols. 544-545

Abstract: The pretreatment of ABS (acrylonitrile-butadiene-styrene) plastics prior to metallization has been generally performed with strong acids, such as sulfuric, chromic, or potassium-permanganate acid. However, conventional wet-chemical pretreatment presents inherent environmental and safety problems to consider. In particular, the presence of Cr+6 imposes a serious environmental threat. Therefore, in this study, aspects of pretreatment, using the photocatalytic reaction in TiO2 sol, were investigated as a replacement for wet-chemical pretreatment. Surface characterization, before and after the pretreatment, was examined by X-ray photoelectron spectroscopy and scanning electron microscopy. A copper film was deposited by electroless plating, and the adhesion strength between the deposited film and ABS plastics was evaluated by the cross-cut tape test (ISO 2409). When ABS plastics were pre-treated in TiO2 sol, the adhesion strength was improved to levels obtained using a strong acid solution.

Abstract: Laboratory-scale batch experiments were conducted to investigate the possible inhibition of acidogenic volatile fatty acids (VFAs) fermentation by an inorganic and a polymer coagulant. It was found that the conversion from organic matter to VFAs decreased more than 10% when the dosages of coagulant exceeded 46 (mgAl/L) and 120 (mgFe/L). Inhibition by Al was greater than that Fe. When the dosage of polymer was over 102 (mg/L), VFAs conversion fell to below 2%. The protein content was more affected than the carbohydrate content. Ultrasonic treatment increased the VFAs conversion for synthetic sludge at both treated with either inorganic coagulant or polymer

Abstract: Ni nanosheet has been prepared at various temperature and time with anion surfactant by chemical reduction of the nickel ion complexes formed from complexing reagent in a pressurized vessel. Sample was characterized by the means of an X-ray diffractomer (XRD), a field emission scanning electron microscopy (FESEM), an energy dispersive X-ray spectrometer (EDS), a selected-area electron diffraction (SAED) and a high sensitive magnetometer (HSM). The use of SDBS and sodium tartrate could be a key factor for the formation and growth of Ni nanosheet.

Abstract: Based on low-temperature hot-press sintering and rapid thermit reaction, heat-resistant metal matrix composites with nano-ceramic reinforcement were prepared via reactive hot pressing. According to XRD, the composites comprised predominantly of (fcc) Cr0.19Fe0.7Ni0.11, (fcc) Fe-Cr and alumina at 700°C through the highly-exothermic thermit reaction between the starting powders. Three-point bending strength, fracture toughness, Vickers hardness and relative density increased with the increase of hot-press sintering temperature and holding time. The improving mechanical properties may be explained by increasing of content of (fcc) Cr0.19Fe0.7Ni0.11. SEM analysis showed a microstructure consisting of equiaxial granules at 700°C for 1 h and a uniformly dispersed network of very fine grains at 700°C for 2 h. It is considered that, in the reactive hot-pressing process, Al atoms diffused into the metal matrix (Fe2O3, Cr, Ni) sites and formed Al2O3 and Fe-Cr-Ni matrix. Such a technique offers the possibility of synthesizing heat-resistant metal matrix composites with nano-ceramic reinforcement materials at considerably lower temperature.

Abstract: We analyzed the effects of several process variables on removal efficiencies of NO and SO2 by the low temperature plasma process combined with photocatalysts. The cylinder-wire type, dielectric barrier discharge process for plasma generation was used. The photocatalysts were coated onto the glass beads by dip-coating method. As the voltage applied to the plasma reactor increases, or as the pulse frequency of applied voltage increases, the NO and SO2 removal efficiencies also increase. As the initial NO concentration decreases, or as the residence time increases, the NO and SO2 removal efficiencies increase.

Abstract: The purpose of this study is to investigate the effect of the operational parameters of the UV intensity and TiO2 dosage for the removal of humic acid and heavy metals. It also evaluated the applicability of hollow fiber microfiltration for the separation of TiO2 particles in photocatalytic microfiltration systems. TiO2 powder P-25 Degussa and hollow fiber microfiltration with a 0.4 μm nominal pore size were used for experiments. Under the conditions of pH 7 and a TiO2 dosage 0.3 g/L, the reaction rate constant (k) for humic acid and heavy metals increased with an increase of the UV intensity in each process. For the UV/TiO2/MF process, the reaction rate constant (k) for humic acid and Cu, with the exception of Cr in a low range of UV intensity, was higher compared to that of UV/TiO2 due to the adsorption of the membrane surface. The reaction rate constant (k) increased as the TiO2 dosage increased in the range of 0.1~0.3 g/L. However it decreased for a concentration over 0.3 g/L of TiO2. For the UV/TiO2/MF process, TiO2 particles could be effectively separated from treated water via membrane rejection. The average removal efficiency for humic acid and heavy metals during the operational time was over 90 %. Therefore, photocatalysis with a membrane is believed to be a viable process for humic acid and heavy metals removal.

Abstract: The TiO2/mica pearlescent pigments were prepared by the hydrolysis of TiOCl2 on the natural mica (muscovite) followed by a calcinations process. The phase transformation of anatase to rutile during calcination and their proportion in the TiO2 thin layer have been analyzed by XRD measurements. The pH controlling during the initial stage of hydrolysis of TiOCl2 showed a pronounced effect on the phase transformation of TiO2 on the substrate. This result may be due to the fact that the pH controlling during the hydrolysis affects the crystal structure and size of TiO2. The decrease in crystallinity and crystallite size of TiO2 resulted in lowering the temperature of phase transformation from anatase to rutile.

Abstract: The catalytic photodegradation of Rhodamine B with UV irradiation over NaMO3 (M= Ta and Nb) doped with Y2O3, La2O3, Nd2O3 and Sm2O3 has been studied in our laboratories. All catalysts were characterized by different techniques such as X-ray powder diffraction (XRD) and thermal analysis (DTA/TGA). Surface characterization of the solids was carried out from adsorption isotherms and infrared spectroscopy (FTIR). The band gap energy (Eg) of materials ranged from 4.1 to 2.9 eV. For comparative purpose the materials studied as catalysts were also synthesized by classical solid state reaction.

Abstract: Highly nitrogen-substituted TiO2 (N-TiO2) thin film photocatalysts were prepared by a radio-frequency magnetron sputtering (RF-MS) deposition method. N-TiO2 thin films with low nitrogen concentration (0.5%) exhibited a small absorption band as a shoulder in the 400-500 nm wavelength region, indicating that isolated N 2p orbitals are formed above the O 2p orbitals. However, N-TiO2 with higher nitrogen concentration (6%) exhibited a sharp absorption edge at 500 nm, indicating that visible light absorption is due to a band gap transition. These N-TiO2 thin films could operate as photocatalysts to decompose 2-propanol diluted in water under visible light. The band structure of N-TiO2 was also determined by photoelectrochemical measurements and H2 and O2 evolution was carried out from an aqueous solution involving sacrificial reagents.

Abstract: The preparation and the photocatalytic degradation NO2 - activity of Fe3+-doped TiO2 nano-sized particles is reported in this paper. The TiO2 nano particles were prepared by sol-gel method. The various influence factors about the synthesis process of the Fe3+-doped TiO2 nano photocatalyst were controlled and investigated by XRD (X-ray diffraction), SEM (scanning electron microscopy), and TEM (transmission electron microscopy) etc.. The results show that the phase compositions, crystalline grain size, crystal structure , and photocatalytic activity of the Fe3+-doped TiO2 particles prepared by the method depend on the synthesis technology parameters such as calcination temperature, holding time, Fe3+ ions concentration etc.. The influence factors of the preparation process has been discussed. The photocatalytic decomposition of NO2 - ion into N2 and O2 using Fe3+ and Ce4+-doped TiO2 photocatalysts were investigated under UV irradiation. It was fund that Fe3+-doped TiO2 photocatalysts shows much higher photocatalytic activity than that of the Ce4+-doped TiO2 . The photocatalytic decomposition effect of NO2 - ion is related to the crystalline grain size, irradiation time, and the Fe3+ ions concentration. The Fe3+-doped TiO2 nano powders exhibited the photocatalytic degradation NO2 - activity under UV light irradiation.