水热合成钨前驱体-碳热还原-碳化制备超细纳米级碳化钨

提出了一种以水热合成的PbWO₄为原料，然后通过碳热还原-碳化获得超细WC的方法。以PbWO₄为钨中间产品，避免了氨氮试剂的引入；采用碳还原的方式可避免水蒸气的产生，抑制了钨粉的长大。结果表明：在初始pH为7.0、反应温度为160 ℃，反应时间为4.5 h的条件下，Na₂WO₄溶液中99.9%（质量分数）以上的W以PbWO₄的形式回收。然后采用低温碳还原PbWO₄，在C:W摩尔比为5、950 ℃的条件下还原3 h，获得了W和C的混合物，该混合物中预加富余的C有助于抑制钨粉的团聚。然后将W和C混合物高温碳化，在1200 ℃下反应6 h，获得了粒径约为60 nm的WC粉末。

Preparation of Ultrafine Nanosized Tungsten Carbide by Hydrothermal Synthesis of Tungsten Precursor, Carbother-mic Reduction, and Carburization

A novel method to prepare ultrafine WC was proposed: the PbWO₄ prepared by hydrothermal synthesis was used as raw material, and WC was obtained through the carbothermic reduction-carburization process. PbWO₄ was used as the tungsten intermediate product to avoid the introduction of ammonia nitrogen reagent. The carbon reduction method can avoid the generation of water vapor and inhibit the growth of tungsten powder. Results show that more than 99.9wt% of W is extracted in the form of PbWO₄ from the Na₂WO₄ solution under the conditions of initial pH value of 7.0, reaction temperature of 160 °C, and reaction time of 4.5 h. Then, the homogeneous mixture of W and C is obtained by the carbothermic reduction of PbWO₄ at 950 °C for 3 h with the molar ratio of carbon:tungsten as 5. Pre-adding excessive carbon in the mixture can inhibit the agglomeration of tungsten powder. Subsequ-ently, the WC powder with particle size of about 60 nm is obtained by the carburization of the W and C mixture at 1200 °C for 6 h.