China Postdoctoral Forum on Materials Science and Engineering

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Authors: De Liang Chen, Tao Li, Li Yin, Rui Zhang, Xin Jian Li
Abstract: Hierarchical SnO2 (H-SnO2) and particulate SnO2 (P-SnO2) nanostructures were synthesized by a hydrothermal method with and without the aid of sodium 1-dodecanesulfonate (SDS), respectively. X-ray diffraction and scanning electron microscopy were used to characterize the products obtained. The sensing properties of the H-SnO2 and P-SnO2 nanostructures to volatile organic compound gas (VOCs) were measured. The H-SnO2 sensors show better gas-sensing performance than the P-SnO2 sensors due to the hierarchical microstructure.
Authors: Yan Min Yang, Wei Zhang, Shan Du, Zhi Ping Yang
Abstract: Yb3+-Ho3+ co-doped germanium-phosphate glasses have been prepared and characterized for its optical properties through measuring photoluminescence and Raman spectra. UV-visible up-conversion emission of holmium ion in Yb3+-Ho3+ co-doped germanium-phosphate glasses has been observed on 980nm excitation. As phosphate was substituted for germanium the red emission Red I decreased at first and then increased later while the green emission Green I decreased and the ratio of Red I to Green I increased. Interestingly, the value of ultraviolet emission intensity was larger than that of the blue and green emission intensity in phosphate glass sample. We believe that Yb3+-Ho3+ co-doped germanium-phosphate glasses might be a potential host material for developing ultraviolet all–solid compact lasers. The possible excitation mechanisms involved in these emissions were discussed, too.
Authors: Jing Li, Yong Cai Zhang, Ming Zhang
Abstract: The synthesis of phase-pure CuInS2 microclusters comprising nanoflakes was achieved by solvothermal treatment of copper indium diethyldithiocarbamates (compositionally CuIn-(DDTC)5) in ethanol at 190 °C for 36 h. The obtained product was characterized by X-ray diffraction, Raman, energy dispersive X-ray spectroscopy and field emission scanning electron microscopy. Besides, contrast synthesis tests using multi-source precursors were also conducted.
Authors: Hong Tao Gao, Yuan Yuan Liu, Xian Zhao
Abstract: N, Cd-codoped TiO2 has been synthesized by sol-gel method coupling with thermolysis. The products were characterized by XRD, SEM, UV-visible DRS, XPS and BET analysis, respectively. The photocatalytic activities of samples were evaluated on the degradation of methyl orange (MO). It was showed that particle sizes of anatase photacatalysts were about 10-15 nm. The maximum specific surface area of the products was 102.7 m2⋅g-1. N atoms were incorporated into the TiO2 crystal lattice, while Cd atoms existed on the crystal surface. The optical absorption edge of N, Cd-codoped TiO2 was 435 nm, which illustrated that the product represented photoactivity in the visible region. It indicated a strong N-Cd synergistic interaction appeared to play a decisive role in driving the excellent photoactivity performance of N,Cd-codoped TiO2.
Authors: Zhi Duan Cai, Lin Dong, Guo Xi Cao, Xing Yan Zhang, Shao Kang Guan
Abstract: A two-step hydrothermal synthesis technique has been developed to obtained 1D ZnO nanostructures with adjustable aspect ratio and size distribution. The pre-curing process has important influence on the morphological, structural and optical properties. The LO phonons of the nanowires obtained by pre-curing for 24 h exhibit slight batho-shift in comparison with nanorods. The increase of the intensity ratio of ultraviolet to visible emissions in room-temperature photoluminescence spectra show the improvement in the quality of ZnO nanostructures as the pre-curing time prolonged. The fitting result of EX energy at T=0 is 3.382 and 3.370 eV for ZnO nanowires and nanorods, respectively.
Authors: Rong Yang, Er Wei Kang, Bai Ling Jiang, Xiao Ping Song
Abstract: LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.% and the XRD experiment confirms that all samples are pure single phase indexed with orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as complexing agent is drastically fine with 200nm. The electrochemical performance of this material, including reversible capacity, cycle number and charge-discharge characteristics, exhibits better.
Authors: Shao Chun Li, Yong Juan Geng, Qi Long Zhang, Hui Yang
Abstract: The dispersion behavior of the solid solution Li1.075Nb0.625Ti0.45O3 (LNT) in aqueous media was studied. Optimum dispersing conditions were investigated in terms of zeta potential, sedimentation, and rheology measurements. Zeta potential measurement showed that the isoelectric point (IEP) of the LNT particles was shifted from pH 3.7 to pH 2.6 after adsorption of PAA-NH4 and made the LNT surface more electronegative. Good agreement between zeta potential, sedimentation, and rheological test was found, which identified an optimum pH value of 10 and an optimum dispersant concentration of about 0.6 wt%. The green microstructures of the casting tapes bear a direct relationship to the state of dispersion of the slurries. The results showed that PAA-NH4 is a suitable dispersant for obtaining well-dispersed LNT slurries.
Authors: Xiao Hong Li, Jing Jing Huang, Tian Cong Cai, Zhi Jun Zhang
Abstract: Silica nanospheres with good dispersibility in oily solvents were prepared using a facile in-situ surface-modification route. The microstructure of resultant surface-capped silica nanospheres was analyzed with a transmission electron microscope. The tribological behavior of the silica nanospheres as additive in engine oil SE 15W/40 was evaluated using a four-ball machine; and the morphology and composition of the worn steel surfaces were analyzed using a scanning electron microscope equipped with an energy dispersive X-ray analysis attachment. It was found that organic modifier hexamethyldisilazane (HMDS) was combined with nano-SiO2 by covalent bonds, resulting in varied surface properties and improved dispersibility of the nanoparticles in many organic mediums. Besides, oil-soluble silica nanospheres as additive in the engine oil had excellent friction-reducing and antiwear abilities, showing promising application prospect.
Authors: Xue Nan Zhang, Shu Liang Gao, Xu Guang Zhang, Jian Hong Li, Yan Jun Wang, Xiang Li, Hao Ping Shen, Ji Hui Wang
Abstract: In this paper, the radial resistivity variation (RRV) of the gas doped floating-zone (GDFZ) silicon has been studied through of three factors that are the lower shaft rotation speed, the timeratio of the lower shaft clockwise(CW) rotation speed and the counterclockwise (CCW) rotation speed, and the eccentricity between the upper shaft and the lower shaft in the horizontal direction. Test results show that the lower shaft speed has greatly influenced the RRV of GDFZ silicon, and with the increase of the shaft speed, radial deviation of the resistivity decreases first and then increases. As the timeratio between the lower shaft of CW&CCW rotation speed increases, the single crystal radial resistivity distribution is improved. As reversible angle of CW&CCW further increasing, radial deviation of the resistivity distribution rises again. With the increases in eccentricity ing, resistivity variation between the edge and the center decreases, thus radial resistivity inhomogeneity of single crystal significantly is also reduced. Based on the above study, further optimization of process, reasonable regulation and control of shaft speed, reversible angle, eccentricity and other parameters selected during GDFZ process can be obtained, which would obtain good radial resistivity uniformity to meet the requirements of the semiconductor devices.

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