TECHNIQUES OF REVERSE REACTION SINTERED Si_3N_4/SiC COMPOSITES
WU Hongpeng, HONG Yanruo, SUN Jialin (Department of Inorganic Non-Metallic Materials, University of Science & Technology Beijing, Beijing100083, China)
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.