The Study Of BN-SiC Composite Ceramic Material By Hot-pressing Sintering Based On Polymer Network Method

This study was used BN as the matrix phase, SiC as the second phase to synthesize BN-SiC composite powders through three different technological methods. Then these composite powders were used for the preparation of BN-SiC composite ceramic by hot-pressing sintering method. Finally, the densification mechanism, mechanical properties and micro-structure were theoretical analyzed,and the influence of sintering temperature, holding time and the content of Si C on the micro-structure and mechanical properties of BN-SiC composite ceramic was systematic researched. At the same time,the intensity distribution of BN-SiC composite ceramic was analyzed in statistics.In this paper, the phase analysis and micro-structure observation of BN- Si C composite ceramic were measured by X-ray diffraction, field emission scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The density,bending strength and hardness of composite ceramic was respectively characterized by Archimedes principle, three point bending method and vickers hardness measuring instrument.The research results show that, for the BN- SiC composite ceramic that was prepared BN-SiC composite powder based on polymer network method, when the sintering temperature was 1750℃, the relative density, bending strength and hardness of the composites were the best(respectively was 74.19%, 69.02 MPa and 374.54 MPa);When the holding time was 120 min, the densification degree of BN-Si C composite ceramic was the best,(about 81.48%); The flexural strength and hardness also achieved the best effect, respectively was 98.29 MPa and 423.81 MPa; Meanwhile it found that the BN-SiC composite powders that were prepared by different methods would get different performance BN-SiC composite ceramic through hot pressing sintering. Under the same process condition(1750 ℃ x120 min,30 MPa), the sintered density and mechanical property of BN-SiC composite ceramic based on polymer network method were better than that of based on mechanical alloying method and ball mill mixing,Finally the effect of SiC content on the composite ceramic sintering properties was also discussed. When the SiC content was 30%, BN- SiC composite ceramic densification degree was at the best: relative density was 84.95%, and its mechanical properties also showed the best, the bending strength and hardness respectively were 132.23 MPa and777.356 MPa. The main innovation point of this article is uesd the highly active compound powder by polymer network to reduce sintering temperature and improve mechanical properties, and lay a foundation for the popularization and application of BN- SiC.