A Study On The Preparation And Properties Of Sialon Bonded SiC Composite

Sialon bonded SiC composite was prepared using Si powder,Al powder and Al₂O₃ as starting materials in the flowing nitrogen atmosphere.By means of XRD and SEM,effect of heating program and the Species of Al₂O₃ on the synthesis of Sialon was investigated.The influence of process synthesis including nitrogen flow,nitriding temperature and nitriding time on the preparation of Sialon were studied by orthogonal test.The influence of the Species of Al₂O₃(α-Al₂O₃ micropowder,Brown Corundum powder,white fused corundum powder)and the additives on the properties of Sialon bonded SiC composite were discussed and analyzed.The results showed:(1)The ratio of nitridation of specimens at 1100℃for heat preservation was higher than the sample nitrided at 1150℃and 1200℃;The content of residual Si of the sample nitrided at 1100℃was lower and more homogeneous.The agglomeration of silicon nitrided at 1150℃and 1200℃was serious.It is more suitable to synthesize Sialon when silicon was nitrided at 1100℃than at 1150℃and 1200℃.(2)The orthogonal experiment results showed that the nitrogen flow,nitriding temperature and nitriding time were not the key factors in the preparation of Sialon. Meanwhile,the results showed that the effect of nitrogen temperature on the preparation of Sialon were more significant than the nitrogen flow and nitriding time.(3)The Brown Corundum powder and white fused corundum powder was more suitable for the nitridation of Si and the preparation of Sialon.The effect of fused dense corundum powder and tabular alumina powder on the nitridation of Si and the preparation of Sialon was worse.The effect ofα-Al₂O₃ micropowder was the worst.(4)Samples with white fused corundum powder performed the best on bulk density,porosity,compressive and bending strength at room temperature.Samples with the Brown Corundum powder took the first place on room temperature bending strength and thermal shock resistance.(5)Sialon/SiC composites with clay as additive have the best compressive strength,bending strength at room temperature,resistance to oxidation and thermal shock resistance.Samples admixed Si₃N₄ took the last place on compressive strength, bending strength at room temperature and resistance to oxidation.