成型压力对β-SiC晶须增强反应烧结SiC材料性能的影响

Effect of Molding Pressure on Properties ofβ-SiC Whiskers Reinforced Reaction-bonded SiC Ceramics

采用3种粒度的α-SiC颗粒为骨料,以硅粉、石墨粉为合成β-SiC基质的原料,通过埋碳烧成法制备反应烧结碳化硅材料。研究了成型压力对反应烧结SiC的相组成、微观结构以及性能的影响,采用XRD、SEM等测试手段对材料的组成、结构与性能进行了表征。研究结果表明:β-SiC晶须是通过气固机制合成,其合成反应抑制了结构致密化。随着成型压力的增加,致密度升高,β-SiC晶须生成量呈减少趋势。成型压力为12 MPa时制备的材料性能最优,其中吸水率为8.37%,气孔率21.08%,体积密度为2.37 g/m^3,抗折强度达到40.7 MPa,断裂韧性为0.42 MPa·m1/2。

Reaction-bonded silicon carbide ceramics were prepared by using a carbon-buried sintering method,withα-SiC powders of different sizes as the aggregates and silicon and graphite powders as the matrix-phases for in-situ formation ofβ-SiC.The effect of molding pressure on phase composition,microstructure and properties of the reaction-bonded SiC ceramics was studied.The samples were characterized by using XRD and SEM.It is found thatβ-SiC whiskers were formed through the gas-solid reaction mechanism,while the reaction suppressed the densification process.The content ofβ-SiC whiskers was decreased and the density was increased with increasing molding pressure.When the molding pressure was 12 MPa,the sample showed optimum properties,with water absorption rate of 8.37%,porosity of 21.08%,bulk density of 2.37 g/m3,flexural strength of 40.7 MPa for and fracture toughness of 0.42 MPa·m1/2.