Advanced Materials Research Vols. 634-638

Abstract: CuO nanostructures were synthesized by thermal evaporation method using Cu metal plate in air at temperatures ranging from 400 to 600 C for 6 h. The CuO nanostructures were characterized by X-ray diffraction, XRD and field emission scanning electron microscopy, FE-SEM. X-ray diffraction, XRD pattern showed the bicrystal nanostructure of CuO and Cu2O. FE-SEM images indicated that the nanowires depended on temperatures. The diameter of Cuo nanowires varies from 10 nm to 20 nm and length of several 5 micrometers.

Abstract: ZnO nanostructures were synthesized by thermal evaporation method using Zn metal plate in air. The Zn metal plates were frozen at -10 C, before into the furnace at a temperature ranging from 300 to 420 C for 15 minutes. The ZnO nanostructures were characterized by X-ray diffraction, XRD and field emission scanning electron microscopy( FE-SEM) and X-ray diffraction( XRD) pattern showed the crystal nanostructure of ZnO. FE-SEM images indicated that the nanowires were depended on temperatures. The diameter of ZnO nanowires werevaried from 50 nm to 70 nm and length of several 100 micrometers.

Abstract: Ammonium polyphosphate (APP) with crystalline form II is usually synthesized in temperature 280-3100C, APP with crystalline form V is usually synthesized in temperature 340-3500C. By process of diammonium hydrogen phosphate, the effect of temperature on crystalline forms of APP was studied and discussed in detail. The results were informative for controllable preparation of APP in industrial production.

Abstract: Mesopores are essential to improve transport of molecules within porous network and to facilitate adsorption of larger molecules. Mesoporous activated carbons (MACs) were prepared by template synthesis and KOH activation, using modified coal tar pitch and nanosized silica as carbon precursor and imprinting template respectively. The influences of different activation conditions, including KOH/C mass ratio, activation temperature and activation time on the pore structure of MACs have been studied. The SBET, total volume and mesopore volume of the result MAC were 1356 m2/g, 0.910mL/g and 0.704 mL/g respectively, when activation conditions with KOH/C mass ratio was 3.6:1, activation temperature was 850°C and activation time was 2.0h. It is possible to control their pore structure by selecting appropriate activation conditions depending on the final application of the MACs.

Abstract: Ammonium polyphosphate (APP) has six crystalline forms, in which form II is commercially applied as flame retardant in engineering plastics such as PP and ABS, form V is extensively studied recently. In preparation of APP, the reaction atmosphere is significant to controllably obtain a certain crystalline forms. In this paper, the effect of wet ammonia is investigated. The results show that low concentration of wet ammonia is suitable for preparation of form II, while dry ammonia is suitable for preparation of form V. The results are informative for controllable preparation of APP in industrial production.

Abstract: The V-doped TiO2 nanoparticles were successfully prepared by sol-gel method and characterized by X-ray diffraction (XRD), UV-vis spectroscopy and photoluminescence (PL) spectroscopy respectively. It is found that doping V can shift the absorption edge to the visible light region and decrease the recombination of photo-induced electron-hole pairs. Then the photo-absorption and photocatalytic activity were greatly improved. The optimal doping concentration is 0.5% due to synergetic effect of the recombination of electron-hole pairs and adsorption of dyes molecules at the surface of samples.

Abstract: Fast synthesis of high-silica ZSM-5 zeolite through vapor-phase transport (VPT) method was reported in this paper. The synthesized samples were characterized with XRD, FT-IR, XRF, SEM and N2 Absorption. Factors affecting the synthesis of ZSM-5 zeolite such as the alkalinity, the crystallization temperature and time, the quantity of seeds were investigated. With precipitated silica and fumed silica as silica source respectively, the appropriate ratio was studied as follows: (0.04-0.05) Na2O: 1.0SiO2: 15H2O: (0-0.0046)Al2O3: 0.01Seed, the reaction was carried out at 393-413K for 4-24h.

Abstract: TiO₂ hollow spheres were prepared by hydrothermal method using CTAB, glucose and (NH4)2TiF6 as surfactant, template and titanium source, respectively. The microstructures of hollow spheres TiO2 were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The results showed the concentration of the CTAB obviously influenced the morphology of hollow spheres TiO2. This synthesis route may also extend to the preparation of hollow structures of other metal oxides. Because of the large specific surface area, porous structure, and good penetration, the hierarchical TiO2-derived hollow spheres may find great applications in catalysis, photovoltaic cells and high surface area electrodes.

Abstract: Novel Fe₃O₄/ordered mesoporous carbon (OMC) composite powders have been prepared by impregnation and reduction methods for the microwave absorbing application purpose. The Fe₃O₄ nanoparticles were encapsulated in the mesopores of OMCs, and Fe₃O₄ contents in the composite could be easily controlled by changing the concentration of ferric nitrate solution during the preparation. The Fe₃O₄/OMC composites show very excellent microwave absorbing properties with respect to pure OMC samples, in a frequency ranging of 8.2-12.4 GHz. A minimum reflection loss (RL) value of -32 dB at 11.35 GHz and a broader absorption band with the RL values under -10 dB are obtained when the thickness of samples is 1.6 mm. The enhanced microwave absorption of the Fe₃O₄/OMC nanocomposites is contributed to the better impedance match between dielectric loss and magnetic loss, which originates from the incorporation of magnetic species into OMC.

Abstract: Eu doped TiO₂ powders have been prepared by the solvothermal process followed by calcination treatment. The furfural and dodecylamine assisted solvothermal method is a very simple way of fabricating porous TiO₂ hollow spheres due to in situ hydrolysis and a self-assembled effect. By adding europium nitrate into the precurso_{Subscript text}r solution, Eu-doped TiO₂ hollow spheres with an intense photoluminescence were easily obtained. The stronger photoluminescence of Eu-doped TiO₂ hollow sample can be attributed to the unique microstructures, such as uniform size distribution and the broken hollow structure, compared to solid Eu-TiO₂ sample.