Papers by Author: Xiao Min Li

Abstract: Well-crystallized LiFePO4 cathode materials were synthesized by NaCl-KCl molten salt method. The effect of heating time on the structure, morphology and electrochemical properties of the materials were studied in detail. Single olivine-type LiFePO4 phase was obtained, and the morphology and particle size of the powders could be controlled by changing the synthesis conditions. It was shown that LiFePO4 cathode material synthesized at 680°C for 3h with the salt content N=2 (defining the molar ratio of NaCl-KCl/LiFePO4 as N) had a narrow particle-size distribution and spherical or quasi-spherical shape. Meanwhile, the tap density of the cathode material reached the maximum of 1.501gcm-3. The charge-discharge test indicated that the initial charge and discharge specific capacity reached 138mAhg-1 and 125mAhg-1 respectively at the current density of 0.3mAcm-2.

Abstract: Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ carbothermic reduction and vacuum pressureless sintering. The effects of Mo-doped on the mechanical properties and microstructures of GT35 composites were investigated. That the good mechanical properties of steel-bonded cemented carbide GT35 with 9wt% Mo were obtained at the same sintering condition that the density reached 6.223g/cm3 and the average bending strength reached about 1155.6MPa after heat treatment, but the hardness dropped the lowest value HRC 60.94 and the difference was not apparent with the change of Mo content. The additive of Mo is beneficial to be refinement of carbide particle size, sphericity of grains and formation of compact composite. In-situ reduction of natural ilmenite was a feasible way to fabricate good performance composite GT35 with a relative low cost.

Abstract: Fe-Al intermetallic/TiC-Al2O3 ceramic composites were fabricated by in-situ carbothermic and aluminothermic reduction from natural ilmenite. Synthesis and sintering of the composites were accomplished unanimously in the vacuum hot pressure furnace. The thermodynamic process, the composition, the microstructure as well as the properties of the FeTiO3-Al-C system were studied in detail through theoretical analysis and experimental research. It was shown that the synthesis process started from the melting aluminium, followed by the deoxidation of ilmenite step by step via a series of different valent titanium oxides to form TiC, Al2O3 and Fe-Al as the ultimate productions. The particle sizes are mostly 3-5μm, and their distributions are uniform. Meanwhile, the addition of additives can improve the wettability of alloy to ceramic phases and the combination of the interfaces, giving rise to the properties of the composites as a whole.