六方-BN对非晶前驱体制备不含添加剂的Si3N4/SiC复合材料相变的影响

摘要

Si3N4/SiC nanocomposites are well known and attractive for advanced ceramic applications due to excellent mechanical and thermal properties, which make them suitable for use in turbine engines,heat exchangers,and other sophisticated applications.However,without the presence of additives,the fabrication of Si3N4/SiC composites is difficult.The additives form a liquid phase during sintering and facilitate the densification of the composite.However,the additives present a drawback at high temperatures since they decrease the mechanical properties of the composites.Recently,Si3N4/SiC composites were fabricated via the polymer precursor route without any additives,using electric field assisted sintering (EFAS).In this study,fully densified Si3N4/SiC nanocomposites incorporating hexagonal-BN were successfully fabricated by hot pressing without any additives at 1700 ℃ for 2 h under vacuum at a pressure of 50 MPa (via the amorphous precursor route).Moreover,the incorporation of additives and h-BN is found to decrease the content of SiC.The phase transformation,densification,microstructure,and mechanical properties were discussed and presented.%Si3N4/SiC纳米复合材料由于具有优良的力学和热性能,广泛应用于涡轮发动机、热交换器和其他复杂情况中.然而,不添加添加剂很难制备出Si3N4/SiC复合材料.添加剂在烧结过程形成液相从而促进复合材料的致密化.然而,添加剂的存在降低了复合材料的高温力学性能.通常在不添加添加剂的情况下,采用电场辅助烧结,利用聚合物前体路线制备Si3N4/SiC复合材料.本研究中,在无添加剂、温度1700℃、真空50MPa条件下,热压烧结2h,利用非晶前体路线成功制备了六方-BN致密化的Si3N4/SiC复合材料.聚合物前驱体和BN的作用减少了的SiC含量.并对相变、致密化、微观组织和力学性能进行了讨论.