浸渍热解对常压烧结SiC/h-BN陶瓷力学性能的影响

Effect of Infiltration-and Pyrolyzation-Treatment on Mechanical Properties of Pressureless Sintered Si C/h-BN Ceramics

采用常压烧结工艺在1700℃保温2 h制备了Si C/h-BN复相陶瓷,在真空条件下使用硅溶胶和酚醛树脂溶液对烧结后试样进行交替循环浸渍,并在1450℃保温1 h进行热解处理,对比研究了浸渍热解处理前后复相陶瓷的致密度、抗弯强度和Vickers硬度的变化,并讨论了复相陶瓷的强化机制。结果表明:Si C/h-BN陶瓷的致密度和力学性能在浸渍热处理后均得到显著的改善,其中Si C/20wt.%h-BN的相对密度从69.7%提高到74.9%,而抗弯强度提高了约1.5倍。浸渍热处理后形成了细小纳米态的Si C颗粒,相互交联沉积在孔隙界面,使裂纹沿界面扩展的阻力显著增加,从而提高了复合材料的力学性能。

Composites of Si C/h-BN ceramic were fabricated by pressureless sintering at 1700oC for2 h. The sintered samples were alternately infiltrated with solutions of silica sol and phenolic in vacuum,and then pyrolyzed at 1450oC for 1 h. The density, flexural strength and Vickers hardness of Si C/h-BN composites before and after infiltration-and pyrolyzation-treatment were investigated, and the strengthening mechanism of the composites was analyzed. The results show that the relative density and mechanical properties of Si C/h-BN composites were improved significantly after infiltration-and pyrolyzation-treatment, as an example, the relative density of increased from 69.7% to 74.9%, and the flexural strength increased near 1.5 times for the composite Si C/20 mass% h-BN; XRD patterns and microstructure of the prepared composite revealed that the Si C particles formed during the pyrolyzation-treatment were nanosized, which precipitated on the inner wall of pores of the sintered composite Si C/h-BN, Therewith, of which the resistance to crack propagation along grain boundaries was obviously increased, i.e., the mechanical properties of Si C/h-BN composite were improved.