预热SHS法制备β-SiC微粉的研究

Study on Preheating SHS Method for Producing βSiC Powder

用预热的方法可以解决自蔓延合成ＳｉＣ过程中硅与碳弱放热反应热量不足的问题。对预热ＳＨＳ合成β－ＳｉＣ粉末所需的最低预热温度Ｔ０、产物粒度与反应物原始粒度的关系等进行了研究。结果表明，当Ｔ０高于１０２３Ｋ时，预热ＳＨＳ可直接合成出β－ＳｉＣ粉末；合成的β－ＳｉＣ粉末的粒度主要由碳粉的粒度所决定，而与硅粉的粒度无关；在此基础上对ＳｉＣ的反应模式进行了探讨。在通氮气（ＰＮ２＝０．１ＭＰａ）情况下，预热ＳＨＳ－ＳｉＣ反应中有一β－Ｓｉ３Ｎ４的生成过程，但生成的β－Ｓｉ３Ｎ４在反应的高温下又很快分解。

Although SiC SHS process is a weakly exothermic reaction, SiC powder can be synthesized by using preheating SHS method. The minimum preheating temperature T0 required in βSiC synthesis reaction and the relations between reactant particle size and product particle size had been studied. The result shows that βSiC powder can be directly synthesized by SHS method when the T0 is higher than 1 023 K. The particle size of βSiC is controlled by the size of carbon and unaffected by the particle size of silicon; based on these results, the model of SiC formation had been established. In nitrogen atmosphere (PN2=0.1 MPa), there is a process of βSi3N4 synthesis in preheating SHSSiC reaction, but the synthesized βSi3N4 is decomposed fast under the high combustion temperature.