Transformation Process of Sodium Tungstata and Natural Graphite in Argon Atmosphere at High Temperature

WEI Linyin, CHUAN Xiuyun†, HUANG Dubin, SU Shuangqing, JIN Shiyun

ACTA Scientiarum Naturalium Universitatis Pekinensis - - Contents -

School of Earth and Space Sciences, Peking University, Beijing 100871; † Corresponding author, E- mail: xychuan@pku. edu. cn

Abstract Using sodium tungstate as tungsten source, natural soil shaped graphite as carbon source, an experiment is provided for researching the transformation process and rules of them in argon atmosphere at high temperature. The final products are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), etc. The result shows that the mixed samples of sodium tungstate and graphite can generate different tungsten carbon compounds in an argon atmosphere with heat treatment. First, reduction reaction occurs between mixed graphite and sodium tungstate dihydrate at the reaction interface, reducing sodium tungstate dihydrate to α- W2C and βW2C. Second, when the mass ratio of NA2WO4 : C is less than 1:1, reduction of α- W2C to α- WC occurs, till the mass ratio was 1:5, and α- W2C can be reduced to α- WC completely. Key words graphite; sodium tungstate; tungsten carbide; high-temperature treatment; XRD; SEM; EDS

WC 具有熔点高、硬度大、耐磨性好等特性,可以作为硬质合金的硬质相原料[ 1], 也可以利用WC 涂层技术, 增强复合材料的力学性能和耐磨性

[ 2]能 。此外, WC具有与金属铂相似的催化性能, 在电极反应中具有广泛的应用价值[ 3], 是复合材料及电化学领域的研究热点。制备 WC 的方法主要有

[ 4] [ 5]喷雾转换法 、机械合金化法 、直接还原碳化

[ 6] [ 7] [ 8 10]法 、溶胶凝胶法 、气相反应法 及等离子体[ 11]法等 。采用直接还原碳化法制备 WC 的优点在于, 在真空气氛下直接还原碳化, 不仅提高了 WC粉末的生产效率[ 12], 而且避免了传统方法中水蒸气[ 6]的产生, 从而抑制含钨气态水化物的合成 。罗[ 6]崇玲等 以 WO3 为钨源, 炭黑为碳源, 在 1000~ 1100ºc 条件下, 利用直接碳化法制得 WC 和过量

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