逆反应烧结制备碳化硅/氮化硅复合材料的工艺

制备Si3N4／SiC复合材料的常规反应烧结是以Si和SiC为原料进行氮化烧结，而逆反应烧结是以Si3N4和SiC为原料，首先使Si3N4反向反应为活性氧化物后再进行烧结。建立逆反应烧结工艺制备Si3N4／SiC复合材料的热力学基础。确定了Si3N4先于SiC氧化；氧化产物可以是SiO2，也可以是Si2N2O；形成的SiO2氧化膜不会与基体材料反应；在膜与基体之间可能生成Si2N2O。论证了逆反应烧结的热力学可行性。通过6个烧结实验，证实了其热力学分析的正确性，并从工艺参数与密度变化、残氮率和比强度等关系筛选出最佳的烧结工艺参数。

TECHNIQUES OF REVERSE REACTION SINTERED Si3N4/SiC COMPOSITES

Conventional production of Si_3N_4/SiC composites using Si and SiC as raw materials sintered under nitrogen atmospheres.The reverse reaction sintering process convert Si_3N_4 into reactive oxides for sintering. Established the thermodynamics theory of reverse reaction sintering Si_3N_4/SiC composites. Confirmed Si_3N_4 oxidation prior to SiC oxidation; the oxides after oxidation may either be SiO_2 or Si_2N_2O. Formed SiO_2 film will not react with the matrix materials. Si_2N_2O can be formed between SiO_2 film and matrix. So the thermodynamics feasibility of reverse reaction sintering is demonstrated. Further 6 sintering tests were carried out and certificated the correctness of the thermodynamics analysis. The best sintering process parameter is concluded through relationships between process parameters and bulk density, nitrogen remaining rate, strength/density ratio.