Papers by Author: Yun Fa Chen

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Authors: X.Y. Xu, Hui Zhao Zhang, Qiang Zhao, Yun Fa Chen, Jian Xu, D.P. Yu
Abstract: Large area well-aligned ZnO nanowire arrays have successfully been synthesized on an unconventional substrate: stainless-steel mesh at a low growth temperature of 400oC. The as-grown ZnO nanowires have uniform diameters about 20 nm and a strong UV peak was observed in photoluminescence spectra. The growth method provides a novel way to produce high quality ZnO nanowire arrays, and can be also used to direct the controllable growth of other nanomaterials.
Authors: Hua Lei Zhou, Dong Yan Li, Guo Zhuo Gong, Ya Jun Tian, Yun Fa Chen
Abstract: Activated carbon was employed as the adsorption carrier for the metal ions in HCl solution of red mud, a solid waste produced in alumina industry. To improve the adsorption capacity to valuable metal ions, the activated carbon was modified by chemicals including HNO3, H2O2, H2SO4, H3PO4, NH3, Na2CO3, and tri-butyl phosphate (TBP). It was found that the modifications contributed the high adsorption capacity to almost all metal ions we focused on. In the case of TBP, remarkably higher adsorption capacity and selectivity of Sc3+ was observed. The correlation between the surface areas, IR spectra of those chemically modified activated carbons and adsorption was schemed.
Authors: C.X. Ruan, Wei Min Gao, R.F. Zhao, Yun Fa Chen, Y.S. Xie
Abstract: To avoid microcrack formation caused by the addition of heterogeneous sintering aids, nano hydroxyapatite powder was prepared by precipitation method and doped into commercial hydroxyapatite powders as homogeneous sintering aid. Gelcasting method was used to prepare these hydroxyapatite green bodies. Densification of the blended powder was performed by pressureless sintering in air atmosphere at the range 1100°C to 1400°C for 2h, with a step size of 50°C. The results showed that the nano particle can greatly improve the densification process of the green bodies, and at 1300°C, which is the highest sintering temperature for hydroxyapatite without decomposition in the air atmosphere, the relative sintering densities of the doped green bodies and the ones without doping were 93.99% and 83.13% respectively.
Authors: Chao Jung Chen, Yu Huai Chang, T.C. Chen, S.H. Li, Yun Fa Chen, H.H. Lin
Authors: Wei Min Gao, Cheng Xiang Ruan, Yun Fa Chen
Abstract: Hydroxyapatite nanoparticles were synthesized in the presence of two kinds of acidic amino acids in order to investigate the effects of acidic amino acids on the morphology of hydroxyapatite obtained by homogeneous precipitation and hydrothermal treating. The results of X-ray diffraction analysis and microphotographs of transmission electron microscope showed that the morphology of hydroxyapatite nanoparticles changed significantly only with aspartic acid. Hydroxyapatite synthesized with aspartic acid showed smooth flake-like morphology at pH= 11 and flake-like morphology with stripes at pH= 8. However, hydroxyapatite synthesized in the present of glutamic acid showed rod-like morphology at both pH values. Variation in the morphology of nanoparticles could be consistent with the difference in the affinity of amino acids binding at the hydroxyapatite crystal surface. The adsorption process was revealed by computer simulation of molecular mechanics using energy minimizing method.
Authors: Qi Wang, Min Jang, Yun Fa Chen
Abstract: The nanocomposite coatings were prepared on the surface of PVC substrate using spinning technique with attempts of introducing nanosized iron oxide particles with different morphology into the organic-inorganic hybrid matrices. The hybrid matrices were derived from 3-glycidoxypropyltrimethoxysilane (GLYMO) and tetraethoxysilane (TEOS) with a process of hydrolyzing and condensation. Nanosized iron oxide particles were synthesized by hydrolysis of FeCl3 solution at different pH value and different temperature. The effects of different additions on nanomechanical properties of the nanocomposite coatings were investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and MTS Nano Indenter XP system. It was found that the acicular α-FeOOH and spherical α-Fe2O3 particles were synthesized, both of them dispersed homogeneously. Nanoindentation and nanoscratch behaviors of the nanoindenter system showed that both of the nanocomposite coatings reinforced the nanomechanical properties of the PVC obviously. Especially, the contribution of acicular α-FeOOH was more remarkable than the spherical α-Fe2O3.
Authors: Qun Yan Li, Wei Min Gao, Yun Fa Chen, Peng Dong, Zhen Jiang Wu
Abstract: The silica colloidal crystal multilayers were deposited from ethanol suspensions with different particle concentrations by vertical deposition method. The microstructures and thicknesses of silica colloidal multilayers were characterized by scanning electron micrography. The thicknesses of colloidal crystal multilayers increased with the particle concentration increasing within a certain range of particles concentrations. When the particle concentration exceeded 2.48wt%, the thicknesses of colloidal crystal multilayers didn’t increased with the concentration increasing. Colloidal crystal multilayers with few defects could be deposited from the suspensions with the particle concentration 2.48wt%. The optical properties of the silica colloidal multilayers were investigated by a UV-Vis scanning spectrophotometer in normal incidence. They corresponded well to the microstructure obtained by SEM images.
Authors: Y. Li, Jiang Hong Gong, Yu Xheng Xie, Zi Long Tang, Yun Fa Chen, Zhong Tai Zhang
Authors: Wei Min Gao, Qun Yan Li, Cheng Xiang Ruan, Yun Fa Chen
Abstract: Hydroxyapatite (HAp) was synthesized in the presence of a variety of amino acids in order to investigate the effect of amino acid on the morphology of HAp obtained by homogeneous precipitation and hydrothermal treating. In the results of X-ray diffraction analysis, HAp synthesized in the presence of some amino acids showed different crystallinity compared with HAp synthesized in the absence of amino acid. The results of Fourier transform infrared spectroscopy suggested the adsorption of these amino acids on HAp. Microphotographs of transmission electron microscope showed that the size and morphology of HAp adsorbed amino acids changed significantly. Collectively, this study suggests that the morphology and the crystallinity of synthesized HAp are different owing to the variation of amino acids in the synthesizing condition.
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