National Engineering Laboratory for Vacuum Metallurgy

Kunming, China

National Engineering Laboratory for Vacuum Metallurgy

Kunming, China
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Huang X.,Kunming University of Science and Technology | Huang X.,National Engineering Laboratory for Vacuum Metallurgy | Du Y.,Kunming University of Science and Technology | Qu P.,Kunming University of Science and Technology | And 7 more authors.
International Journal of Electrochemical Science | Year: 2017

A modified method of carbon coating by vacuum decomposition was employed to synthesize nano-sized LiFePO4/C cathode material. Sucrose, polyvinyl alcohol (PVA) and citric acid (CA) were used as different carbon resource and their pyrolysis behavior on the properties of the LiFePO4/C composite was also investigated. During vacuum decomposition process, the organic carbon suppressed particle growth and decreased particle agglomeration, resulting in homogeneous carbon coated material. Among them, the sucrose coated LiFePO4/C sample exhibited reduced particle size, regular spherical grains and graphitized carbon coating, indicating an enhancement to electrochemical performance. The sample delivered high specific capacity of 123.9 mAh/g at 5C and good capacity retention of 96.2% after 100 cycles at 1C. A comparison of carbon coating by traditional argon atmosphere and vacuum condition further demonstrated that vacuum decomposition method is conducive to refining particle for better carbon coating, leading to dramatically improved electrode polarization and rate performance of LiFePO4/C composite. © 2017 The Authors.


Lan Y.-P.,Chongqing University | Lan Y.-P.,University of Utah | Sohn H.Y.,University of Utah | Mohassab Y.,University of Utah | And 5 more authors.
Journal of Nanoparticle Research | Year: 2017

Thermally stable blue nonstoichiometric nanoceria was produced by feeding nanoceria with an average size of 50 nm into a DC thermal plasma reactor. The effects of different plasma power levels and atmospheres were investigated. XRD results showed the ceria lattice parameter increased with plasma power. SEM and TEM results showed that the shape of nanoparticles changed after plasma treatment; the blue nonstoichiometric nanoceria had highly regular shapes such as triangular pyramids and polyhedral in contrast to the irregular shape of the raw nanoceria. Significant downshift was found in the Raman spectra of the plasma products, with a 7.9-cm−1 shift compared with raw nanoceria, which was explained by the reduction of Ce4+. X-ray photoelectron spectroscopy results showed that the Ce3+ fraction increased from 14% in the raw nanoceria to 38–39% for the product CeO2-x, indicating the high reduction state on the ceria surface. It was determined that this blue nonstoichiometric nanoceria was stable up to 400 °C in air, but the color changed to pale yellow after 4 h at 500 °C in air indicating oxidation to CeO2. Additionally, this novel stable nano-CeO2-x caused a red shift in the UV-visible absorption results; a 48-nm red shift occurred for the nonstoichiometric nanoceria produced at 15 kW compared with the raw nanoceria. The band gap was calculated to be 2.5 eV while it was 3.2 eV for the raw nanoceria, indicating that this novel stable blue nonstoichiometric nanoceria should be a promising material for optical application. © 2017, Springer Science+Business Media B.V.


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.-Y.,Honghe University | Sen W.,Yunnan Tin Company Ltd | Ma W.-H.,National Engineering Laboratory for Vacuum Metallurgy | Yu J.,National Engineering Laboratory for Vacuum Metallurgy | Yang J.-J.,National Engineering Laboratory for Vacuum Metallurgy
Rare Metals | Year: 2014

La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) and La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM) powders were synthesized by glycine-nitrate process, and LSGM electrolyte thin film was successfully fabricated on porous anode substrate of LSCM by slurry spin coating technology. Some technical parameters for the preparation of LSGM thin films were systematically investigated, including ink composition, sintering temperature, and spin coating times. The electrolyte films with the best compactness and somewhat rough are obtained when the operating parameters are fixed as follows: the content of ethyl cellulose as binder is 5 wt%, the content of terpineol as modifier is 5 wt%, the optimum coating cycle number is 9 times, and the best post-deposition sintering temperature is 1,400 °C for 4 h. © 2014 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg.


Yang J.,National Engineering Laboratory for Vacuum Metallurgy | Yang J.,Kunming University of Science and Technology | Ma W.,National Engineering Laboratory for Vacuum Metallurgy | Ma W.,Kunming University of Science and Technology | And 7 more authors.
Journal of Rare Earths | Year: 2013

La0.9Sr0.1Ga0.8Mg0.2O 3-δ (LSGM) electrolyte materials were synthesized by the solid state reaction method. The conductivity of LSGM materials was detected by four probe method, and it was 0.08 S/cm at 850 °C. Dense and uniform films of LSGM materials were deposited by the magnetic sputtering on substrates of Si and La0.7Sr0.3Cr0.5Mn0.5O 3-δ (LSCM). The experimental results showed that the deposition rates dropped and the average grain sizes of the films enlarged with increase in the substrate temperatures. In the sputtering process, the LSGM film was deposited with preferred growth direction. After annealing, the preferred growth direction disappeared and the film surface became smoother and denser. Through observing the deposition process, deposition mechanism was proposed, which was consistent with a model of island growth.


Tian Y.,National Engineering Laboratory for Vacuum Metallurgy | Tian Y.,Kunming University of Science and Technology | Liu H.,National Engineering Laboratory for Vacuum Metallurgy | Liu H.,Kunming University of Science and Technology | And 4 more authors.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2012

Magnesium metal was extracted from magnesia by carbothermic reduction in vacuum. The Mg condensates were characterized with X-ray diffraction and scanning electron microscopy. The impacts of extraction conditions, including the pressure, temperature, molar ratio, carbothermic time and content of the catalyst, compactness of magnesia grains, etc., on the Mg reduction rate and reactant weight loss were evaluated. The results show that the newly-developed Mg vacuum extraction technique does a good job, and that the extraction conditions strongly affect the Mg extraction rate and reactant weight loss. For instance, at a temperature over 1553 K, a pressure ranging 30~100 Pa, and with the grains compressed at 8 MPa, the largest reactant weight losses were obtained, resulting in the highest Mg reduction rate. As the molar ratio of C/MgO and reaction time increased, the rates of both carbothermic reaction and Mg reduction increased slowly. Addition of CaF 2 significantly increased the reactant weight loss. When CaF 2 accounted for 3% of the total weight, the weight loss rate increased up to 95%, coinciding with a large Mg reduction rate.


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.


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.


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.


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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