Papers by Author: Xiao Feng Wu

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Authors: Xiao Feng Wu, Yu Chao Liao, Ren Liang Yue, Yun Fa Chen
Abstract: Based on the growth kinetics of the SiO2 particles, we studied the kinetic hetero-precipitation process on the interface of polystyrene (PS) microscale particles. The nanoscale SiO2 shell thickness increased with increasing time and was proportional to the square root of the initial concentration of TEOS precursor while governed by hetero-precipitation process. Moreover, the hetero-precipitation process followed the first-order growth mechanism of silica onto the surface of templating PS pariticles. Properly controlling the reagent concentrations could alleviate and even avoid, to a certain extent, aggregation among PS@SiO2 particles that could otherwise have an adverse effect on the properties and applications of those composite particles and the corresponding SiO2 hollow products.
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Authors: Xiao Feng Wu, Yun Fa Chen, Qun Yan Li, L.Q. Wei
Abstract: Hollow microspheres of nickel hydroxide and nickel oxide were prepared with as-synthesized PS/Ni(OH)2 composite particles by sacrificing core method, respectively. The composite particles were synthesized by deposition of the Ni(OH)2 nanoflakelets formed by the hydrolysis of nickel nitrate onto the surfaces of polystyrene (PS) particles. The effects of different concentrations of nickel salt and urea on the deposition of the nanoflakelets of nickel hydroxide were studied. It was found that the uniform nanoflakelets were deposited on the polystyrene particles under the conditions of the 4╳10-3 M nickel salt and 0.667M urea. Compared with the directly calcinating of composite particles, Integral hollow microspheres of nickel hydroxide were attained by removal of cores of polystyrene in composite particles with toluene and NiO hollow microspheres by calcinating of these Ni(OH)2 hollow spheres in oven at 600°C for 2h.
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Authors: Qi Wang, Yun Fa Chen, Min Yang, Xiao Feng Wu, Ya Jun Tian
Abstract: Low agglomerating spherical α-Fe2O3 nanopowders were synthesized by catalytic phase transformation in hydrothermal reaction and then dried through freeze-drying. It was found that the as-synthesized particles were spherical and the particle size results obtained from the different measurement methods, including BET, XRD, TEM, SEM and laser particle size analyzer, were almost the same, implying that the α-Fe2O3 nanopowders were low agglomerating.
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Authors: Yan Bin Cui, Shuang Lin Zhan, Xiao Feng Wu, Guo Zhuo Gong, Ya Jun Tian, Yun Fa Chen
Abstract: In this paper, mass production of quasi-aligned CNTs was achieved with a new tri-metallic catalyst (Fe-Ni-Mo/MgO) by thermal CVD method, using methane as carbon precursor. The growth process was in-situ monitored by thermal gravimetry/differential scanning calorimetry (TG-DSC) technique, and the yield of CNTs over 2200% was attained under the mixture atmosphere of CH4 and H2 with flow rate about 25 ml/min and 5 ml/min respectively at 900°C for 30 min. The as-prepared products were characterized. Raman spectrums showed that the CNTs are multi-wall structure. The diameter of the CNTs was estimated to be 20-30 nm. We think the synergism of FeNi3 alloy and Mo is the main reason for the high catalytic activity of tri-metallic catalyst.
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