Papers by Author: Li Yun Cao

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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: Wen Dong Yang, Jian Feng Huang, Li Yun Cao, Xie Rong Zeng
Abstract: Cristobalite aluminum phosphate (C-AlPO4) coatings were prepared by hydrothermal electrophoretic process on SiC coated C/C composites at different temperatures. The as-prepared C-AlPO4 coatings was characterized by SEM analyses. The influence of hydrothermal deposition temperature on the microstructures of the as-prepared coatings and the deposition kinetics mechanism were investigated. Results show that dense and homogeneous C-AlPO4 coatings on SiC coated C/C composites can be achieved at 373K and 220V deposition voltage; Kinetics investigations show that the deposition process of the C-AlPO4 coatings on SiC coated C/C composite is controlled by the diffusion rate of the charged C-AlPO4 particles to the cathode; the deposition rate increases with the increase of hydrothermal temperature. The diffusion equation and the kinetic expression of coating process follow the Fick’s second law and Ahrennius relationship. The deposition activation energy of the C-AlPO4 coatings fabricated by the hydrothermal electrophoretic process is calculated to be 21.88kJ/mol.
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: Hui Zhu, Jian Feng Huang, Li Yun Cao, Yan Wang, Xie Rong Zeng
Abstract: Zinc sulphide (ZnS) thin films were deposited on the indium tin oxide (ITO) substrates by a novel, simple cathodic electrodeposition method under atmospheric pressure. These thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence spectrum (PL) at room temperature. The effects of deposition voltage on the phase composition, morphology and photoluminescence behavior of the thin films were investigated. XRD analysis shows that the deposited thin films is highly preferential growth along (200) orientation. Both AFM and XRD analyses indicate that the surface of the ZnS thin films is composed of uniform grains of around 50 nm in diameter. With the increase in the deposition voltages, the crystallization of the obtained thin films improves and the grain size of the ZnS thin films increases. Photoluminescence emission peaks are observed at at 475~490 nm and 500 ~530 nm at room temperature for an excitation of 210 nm.
Authors: Wen Bin Li, Jian Feng Huang, Jie Fei, Wen Jing Wang, Li Yun Cao
Abstract: In order to make clear the effects of modified-phenolic on the tribological properties, three kinds of carbon fiber reinforced phenolic friction materials (cashew-modified phenolic, boron-modified phenolic and chemigum-modified phenolic) were fabricated with the ethyl alcohol as the solvent by vacuum filtration. The tribological properties of samples were studied by the QM1000-II wet friction performance tester. The scanning electron microscope was employed to analyze the micro topography of specimens. Results show that the dynamic friction coefficient and variable coefficient of cashew-modified phenolic friction materials are better than other two materials. The temperature is the most stable during the continuous engagements. The friction torque curve is the smoothest and most symmetrical. Thus, the comprehensive performance of cashew-modified phenolic friction materials is excellent.
Authors: Jian Feng Huang, Yan Wang, Li Yun Cao, Hui Zhu, Xie Rong Zeng
Abstract: Bismuth sulfide (Bi2S3) is an important semiconductor material, which has wide applications in thermoelectricity, electronics, photoelectricity and infrared spectroscopy. Bi2S3 thin films have been deposited on ITO substrates through a cathodic electrodeposition approach at room temperature. The as-deposited thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence spectrum (PL). The effects of solution pH values on the structures and optical properties of the thin films were particularly investigated. Results show that uniform Bi2S3 thin films with oriented growth along (240) direction can be obtained at the solution pH value range from 4.5 to 6.5. The as-prepared thin films exhibit stable blue-green photoluminescence properties under the ultraviolet light excitation at room temperature. With the increase of the solution pH values, the crystallization of the Bi2S3 thin films improves while the grain size of the obtained thin films decreases and the light emission intensity of the thin films decreases.
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: Liu Qing Yang, Jian Feng Huang, Xin Gang Kong, Li Yun Cao, Jia Yin Li, Jie Fei, Cui Yan Li, Hai Bo Ouyang
Abstract: Zinc borate (4ZnO·B2O3·H2O) crystallites at diverse pH values were prepared by a hydrothermal method. The phase composition, morphologies and photocatalytic properties of the samples were characterized by XRD, SEM, UV–vis spectro-scopy and UV–vis diffuse reflectance spectro-scopy. Results show that the 4ZnO·B2O3·H2O microcrystalline obtained at pH=9 shows a new clintheriforms morphologies assembled by nanowiskers. Superior UV-light photocatalytic activity of the samples for MB, RhB and MO is observed especially higher than that of P25 for MB. These samples exhibit morphology-related ultraviolet absorbing ability with different optical band gaps from 4.01 eV to 4.22 eV. Band gaps are responsible for the highly UV-light photocatalytic activity.
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.
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