Oxidation Behaviors of the Pressureless Sintered ZrB_2-SiC Composites

The pressureless sintering process of ZrB2-SiC composite ceramics was studied.The ceramic samples was prepared by using sol-gel synthesized ultra-fine ZrB2 powders as sources and different contents of Mo and/or B4C as sintering aids.The static oxidation behaviors of the sintered ZrB2-20wt%SiC composite ceramics using 4wt%Mo and 4wt%Mo-2wt%B4C additives were systemically analyzed.The results show that the composite ceramics oxidized quickly with visible ZrO2 particles on the surface above 1300℃/30min with pure Mo additive.While Mo-B4C additive is added,the protective liquid layer appears at 1300℃ and becomes thicker and uniform with the temperature rising.The composite ceramics present good oxidation resistance of which the flexural strength retains 86% of the value in room temperature after oxidiation at 1500℃ for 30min.