Papers by Author: Jian Peng Wu

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Authors: Hui Qi, Jian Feng Huang, Li Yun Cao, Jian Peng Wu
Abstract: –Hierarchical flower–like CuS spheres have been synthesized by a facile microwave hydrothermal (MH) method using cetyltrimethylammonium bromide (CTAB) as the surfactant. The as–prepared CuS crystallites under different CTAB contents were characterized by X–ray diffraction (XRD), field–emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Results show that the CTAB–assisted CuS particles have hierarchical flower–like microstructures that were assembled by thin nanoflakes with thickness of 10~20 nm. The corresponding HRTEM images reveal that these nanoflakes are composed of many nanoparticles with average size of about 7 nm. Moreover, when increasing the CTAB contents from 0 g⁄mL to 0.02 g⁄mL, the as–prepared CuS particles were found to have better dispersion stability with decreased average sizes of the hierarchical flower–like spheres. Comparing with the bulk CuS particles, the related UV–vis absorption spectrum of the as–prepared crystallites exhibits an obvious red shift with the absorption peak at 739 nm.
Authors: Ying Sun, Jian Feng Huang, Li Yun Cao, Jian Peng Wu
Abstract: Olivine LiFePO4 and LiFePO4-C composite cathode materials were prepared by microwave hydrothermal process using FeC2O4·2H2O, NH4H2PO4, LiOH·H2O and acticarbon as source materials. The effect of acticarbon on the structure and charge-discharge property of LiFePO4 crystallites was investigated. The as-prepared battery powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer(EDS). The charge-discharge behavior was investigated for the characterization of the electrochemical performances of the powder. Results show that the introduction of acticarbon will not change the LiFePO4 crystal structure, but achieve more uniform and fine crystallites and result in better electrochemical performance. Initial discharge capacity of the as-prepared LiFePO4 is 103.4 mAh·g-1 at 0.1 C rate. The discharge capacity of LiFePO4-C is 136.1 mAh·g-1 at the first cycle and 133.9 mAh·g-1 after 30 cycles at 0.1 C rate.
Authors: Jian Feng Huang, Qin Feng Zhang, Bao Yun Hu, Li Yun Cao, Jian Peng Wu
Abstract: Cadmium sulphide (CdS) crystallites were successfully prepared by a microwave hydrothermal (M–H) process using cadmium chloride (CdCl2·H2O) and sodium thiosulfate (Na2S2O3·5H2O) as source material with different Cd2+ concentration. The phase, composition, morphology and optical property of the obtained crystallites were characterized by X–ray diffraction (XRD), field–emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) and ultraviolet–visible spectrophotometer (UV–Vis). Results show that the crystalline structure of the prepared CdS crystallites changes regularly with the increase of Cd2+ concentration and the corresponding morphology of CdS crystallites transforms from tetrahedron to quasi-sphere. The quasi-spherical CdS is derived from the nanoparticles-assembly behavior. And with the increase of Cd2+ concentration, the decrease in CdS crystallite size is observed. Obvious blue–shift is detected in the UV–Vis absorption when Cd2+ concentration reaches 0.60 mol/L.
Authors: Jian Peng Wu, Chun Yan Yao, Li Yun Cao, Jian Feng Huang, Hai Yan He, Hui Zhu
Abstract: In order to make quantitative analysis by internal standard method, 24 standard curves of inorganic compounds including quartz, corundum, TiO2, BaTiO3, etc. were obtained and the corresponding quantitative analyses were accomplished based on the quantitative analysis software attached in Rigaku D/Max-2200 X-Ray diffractometer. Results show that the coefficient of association R of the as-prepared curves are at the range of 0.928-0.980. By validating the samples with due content, it reveals that the analytical results are consistent with the actual values well, which indicate that the prepared standard curves are suitable for high-precision XRD phase quantitative analysis. Uniformity of samples is an important factor in the quantitative analysis by internal standard method.
Authors: Yu Tao Zhang, Jian Feng Huang, Li Yun Cao, Fei Deng, Jian Peng Wu
Abstract: Yttrium silicates coatings were deposited on SiC-C/C composites surface by a hydrothermal electrophoretic process using yttrium silicates nano-crystallites, isopropanol and siodine as source materials, solvent and charging agent, respectively. The yttrium silicates nano-crystallites were preprepared by a sonochemical process. The influence of deposition temperatures on the microstructures and crystallization of the yttrium silicates coatings were investigated. Surface and cross-section microstructures of the as-prepared multi-coatings were characterized by XRD and SEM. Results show that the coatings are composed by yttrium silicates crystallites with the main phase of Y2Si2O7 and a little Y2SiO5. The thickness and the density of the yttrium silicates coatings increases with the increase of deposition temperatures; and the coating process has little influence on the phase compositions of the coatings.
Authors: Jian Feng Huang, Fei Deng, Li Yun Cao, Jian Peng Wu, Hong Jie Luo
Abstract: Oxidation resistant SiC coating for graphites was prepared by a pack cementation process with mixture powders of Si, C, SiC and some infiltration additives containing MgO, Al2O3 and Cr2O3. The influence of different infiltration additives on the phase, microstructure and oxidation resistance of SiC coating was primarily investigated. The results showed that adding infiltration additive in the pack powders is helpful for depositing denser SiC coating on graphite substrate; and the coating prepared by using MgO as infiltration additive exhibited better oxidation resistance at high temperature. XRD analyses revealed that SiC coating prepared by adding of MgO as infiltration additive possessed more free silicon; and the SEM analyses displayed that the free silicon could effectively fill the small holes of the SiC coating, which resulted in a perfect dense surface structure of SiC coating. Oxidation test showed that the as-prepared SiC coating could effectively protect graphite materials at 1500oC for 200 hours and the corresponding weight loss of the coated graphite was only 0.13%.
Authors: Zhi Qing Zhang, Jian Feng Huang, Li Yun Cao, Jian Peng Wu
Abstract: Nanocrystalline TiO2 films were deposited on polymethylmethacrylate (PMMA) substrates by dip–coating process from colloidal anatase aqueous solutions. Microwave–hydrothermal process treating TiO2 colloidal solutions was applied to enhance crystallization under a mild condition and avoid post–treatment. The as–prepared TiO2 films were characterized and analysed by X–ray diffraction (XRD), UV–visible spectroscopy and atomic force microscopy (AFM). The photocatalytic degradation of Rhodamine B (RhB) under ultraviolet radiation was explored. Results show that pure anatase TiO2 is achieved rapidly using microwave hydrothermal process. The TiO2 suspension becomes uniformly disperse, stable and deposit-free after ultrasonic dispersion. The thin films deposited on unmodified PMMA substrates from the dispersive TiO2 colloidal solution are dense, homogeneous, crack–free, without visible agglomerates and show high photocatalytic activity without post-treatment. Rhodamine B has been degraded over 99 % after 180 minutes under UV irradiation.
Authors: Ye Zhang, Li Yun Cao, Jian Feng Huang, Jian Peng Wu
Abstract: The La2S3 microcrystalline were prepared by microwave hydrothermal method (M–H). The influences of different S⁄La molar ratio on the phase composition, and morphology of the La2S3 microcrystalline were particularly investigated. The obtained samples were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet and visible–spectroscopy (UV–vis) and photoluminescence spectroscopy (PL) at room temperature. XRD results show that the decrease of S⁄La molar ratio from 6⁄3 to 6⁄6, the improving in crystallization of the obtained microcrystalline is observed with the decrease in S⁄La molar ratio. The morphology of prepared La2S3 transforms from irregular shapes to quasi-sphere structure. The as-prepared microcrystalline show excellent absorbency of ultraviolet light and are almost transparent to visible light to exhibit stable violet-blue photoluminescence properties under the ultraviolet light excitation at room temperature.
Authors: Jia Zhu, Jian Feng Huang, Li Yun Cao, Jian Peng Wu
Abstract: In order to improve the oxidation resistance property of carbon/carbon composites, the C/C matrix was modified with a borate sol precursor and B4C micro-powders by a sol-gel integrating with a solvothermal process. The phase compositions, surface and cross-section microstructures of the C/C matrix modified by different B4C content were particularly investigated. Results show that the surface of the modified composites is covered by a coating composed of B2O3 and B4C, meanwhile, the internal micro-holes of the C/C composites are occupied by B2O3 and B4C. After oxidation in air at 973 K, the B2O3 glassy phase, due to the oxidation of B4C, seals the cracks and holes and effectively prevents C/C composites from oxidation. The weight loss of the modified C/C composites is only 2.21 % after oxidation in air at 973 K for 20 h.
Authors: Guang Yan Zhu, Jian Feng Huang, Li Yun Cao, Min Zhou, Jian Peng Wu
Abstract: Hydroxyapatite (HAp) coatings were prepared by a hydrothermal electrodeposition method on Carbon/carbon (C/C) composites. The as-prepared HAp coatings were characterized by XRD and SEM analyses. The influence of hydrothermal temperature on the phase and surface microstructures of HAp coatings and the corresponding deposition kinetics were particularly investigated. Results show that with the increase of hydrothermal temperature, the crystallinity, density and homogenous of the prepared HAp coatings are improved. The deposition rate also increases with the increase of hydrothermal temperature. The deposition activation energy of HAp coatings by the hydrothermal electrodeposition process is calculated to be 25.89 kJ/mol.
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