原位合成Mo_5SiB_2的热力学分析

Thermodynamic analysis for the synthesis of Mo_5SiB_2

计算了Mo-Si-B三元系中各化合物不同温度下标准生成自由焓和合成Mo5SiB2(T2相)反应在不同开始温度下的绝热温度及反应产物的熔化比.结果表明:用Mo、Si和B三种元素粉末混合物来原位合成Mo5SiB2在热力学上是完全可行的;合成Mo5SiB2不宜用燃烧合成的自蔓延模式,宜采用燃烧合成的热爆模式(原位反应热压工艺);反应的绝热温度及反应产物的熔化比与开始温度有关.

The standard formation free energies at different temperatures of compounds in a Mo-Si-B ternary system were calculated. The adiabatic temperatures and the molten ratios of Mo5Sit2（T2 phase） at different initial temperatures for the reaction of synthesizing Mo5Sit2 were obtained, The results showed that it was feasible to synthesize in-situ Mo5Sit2 from the elemental powders. Mo5Sit2 could not be synthesized using the SkIS （self-propagating high-temperature synthesis） mode of combustion. In contrast, the explosion mode of combustion （in-situ reactively hot-pressing） was acceptable. The adiabatic temperature and the molten ratio of Mo5Sit2 were relative to the initial temperature.