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Jia J.,National Engineering Laboratory for Vacuum Metallurgy | Xu B.,Key Laboratory for Nonferrous Metals Vacuum Metallurgy | Yang B.,Kunming University of Science and Technology | Wang D.,National Engineering Laboratory for Vacuum Metallurgy | And 2 more authors.
Key Engineering Materials | Year: 2013

Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor. Copyright © 2013 Trans Tech Publications Ltd.


Sen W.,National Engineering Laboratory for Vacuum Metallurgy | Sen W.,Key Laboratory of Vacuum Metallurgy for Nonferrous Metal of Yunnan Province | Sen W.,Kunming University of Science and Technology | Xu B.-Q.,National Engineering Laboratory for Vacuum Metallurgy | And 11 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2011

The preparation of fine TiC powders by carbothermal reduction of TiO 2 in vacuum was investigated by XRD, SEM, XRF and laser particle sizer. Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and the formation sequence of products are Ti4O7 (Magneli phase), Ti3O5, Ti2O3, TiC xO1-x and TiC with the increase of reaction temperature. Experimental results demonstrate that TiC powders with single phase are obtained with molar ratio of TiO2 to C ranging from 1:3.2 to 1:6 at 1 550 °C for 4 h when the system pressure is 50 Pa, and TiC1.0 is gained when the molar ratio of TiO2 to C is 1:4 and 1:5. In addition, fine TiC1.0 powders (D50 equals 3.04 μm) with single phase and low impurities are obtained when the molar ratio of TiO2 to C is 1:4. SEM observation shows that uniform shape, low agglomeration, and loose structure are observed on the surface of block product. © 2011 The Nonferrous Metals Society of China.


Li Y.,National Engineering Laboratory for Vacuum Metallurgy | Li Y.,Kunming University of Science and Technology | Yu Q.,National Engineering Laboratory for Vacuum Metallurgy | Yang B.,National Engineering Laboratory for Vacuum Metallurgy | And 2 more authors.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2012

Here, we addressed the vacuum decomposition of kaolin, mainly consisting of kaolinite, diaspore, and pyrite, to explore the possible applications of the decomposed compounds. The impacts of The decomposition conditions, such as the decomposition temperature and time, pressure, and impurities, on microstructures and stoichiometries of the decomposed compounds were evaluated with scanning electron microscopy, X-ray diffraction and differential scanning calorimetry-Thermogravimetric analysis. The results show that the low pressure strongly affects the dehydration of diaspore and decomposition of pyrite. For instance, at a pressure of 15~50 Pa, starting at 100°C, The complete dehydration of the diaspore occurred at 300°C. At a temperature ranging from 500°C~600°C, The decomposition of the pyrite into FeS and S 2 took place, and completed at 700°C. The dehydration temperature of kaolinite into metakaolinite was about 200~300°C, 200°C lower than that at atmospheric pressure. The experimental data agree fairly well with the calculated results based thermodynamics at a pressure from 10 5 Pa to 50 Pa. We found that the decomposition sequence of the three main components little affects the decomposition of the kaolin.


Sun H.,National Engineering Laboratory for Vacuum Metallurgy | Sun H.,Kunming University of Science and Technology | Sun H.,Honghe University | Ma W.,National Engineering Laboratory for Vacuum Metallurgy | And 7 more authors.
Vacuum | Year: 2012

Thin films of solid electrolyte La 0.9Sr 0.1Ga 0.8Mg 0.2O 3-δ (LSGM) were deposited by RF magnetron sputtering onto porous La 0.7Sr 0.3Cr 0.5Mn 0.5O 3-δ (LSCM) anode substrates. The effects of substrate temperature, sputtering power density and sputtering Ar gas pressure on the LSGM thin film density, flatness and morphology were systematically investigated. RF sputtering power density of 7.8 W cm -2, substrate temperature of 300°C and sputtering Ar gas pressure of 5 Pa are identified as the best technical parameters. In addition, a three-electrode half cell configuration was selected to investigate the electrochemical performance of the thin film. The LSGM film deposited at optimum conditions exhibited a lower area specific ohmic resistance of 0.68 Ω cm -2 at 800°C, showing that the practicability of RF magnetron sputtering method to fabricate LSGM electrolyte thin film on porous LSCM anode substrates. © 2011 Elsevier Ltd. All rights reserved.


Sun H.,National Engineering Laboratory for Vacuum Metallurgy | Sun H.,Kunming University of Science and Technology | Ma W.,National Engineering Laboratory for Vacuum Metallurgy | Ma W.,Kunming University of Science and Technology | And 5 more authors.
Journal of Rare Earths | Year: 2010

The La0.8Sr0.04Ca0.16Co 0.6Fe0.4O3-δ (LSCCoF) and La 0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) powders were synthesized by glycine-nitrate combustion process and conventional solid-state reaction method, respectively. The LSCCoF-LSGM composite cathode material was successfully elaborated and deposited on dense pellets of the LSGM electrolyte by means of slurry spin-coating process. The cathode films with the best surface morphology and microstructure were obtained when the operating parameters fixed as follows: the content of ethyl cellulose which acted as pore former and binder is 10 wt., the content of terpineol which acted as modifier is 5 wt., the speed of rotation rate is 3200 r/min and the best post-deposition sintering temperature is 1000 °C. © 2010 The Chinese Society of Rare Earths.

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