热处理对层状SiC/Si复合材料结构和性能的影响

牛皮纸浸酚醛树脂,经叠层、固化、碳化,最后,埋入硅粉中,在N2气保护下加热到1400℃,再抽真空并升温至1550℃,保温60min,使碳化样品与液态硅充分反应,制备了SiC/Si层状陶瓷复合材料.复合材料的密度、强度分别为2.20g/cm3和435MPa.将SiC/Si层状复合材料分别在氮气和真空中,于1440℃进行再热处理.研究了再热处理后材料的组成、显微结构和气孔率、强度等物理性能.结果表明:在氮气气氛下再热处理60min,样品的密度、强度分别达2.32g/cm3和455MPa,此时,因SiC/Si层状复合材料中Si与C经扩散迁移而反应形成更多的SiC,使材料的密度、强度提高.在真空环境中1400℃再热处理30min,样品的密度、强度分别为2.12g/cm3和430MPa,这是由于Si蒸发,样品的质量减少,气孔率大幅度增加,因此,密度和强度略有下降.

EFFECT OF HEAT TREATMENT ON THE MICROSTRUCTURE AND PHYSICAL PROPERTIES OF SiC/Si LAMINATED COMPOSITES

Carbon templates were prepared by kraft papers impregnated with phenol resin,and after laminated,drying and carbonization,packed with silicon powder and heated to 1400℃ in N2 atmosphere.They were heated to 1550℃ in vacuum for 60 min,and the subsequent reaction resulted in a laminar SiC/Si composire with a density of 2.20 g/cm3 and strength of 435 Mpa.The laminated SiC/Si composites were retreated under nitrogen atmosphere and vaoaum separately at a temperature of 1400℃ for 30 min.The results show that during retreatmem in N2 atmosphere,with the diffusion of Si and C,more SiC formed,and the density and bending strength of the retreated composite increase to 2.32g/cm3 and 455MPa,respectively.The density and bending strength of the retreated composite in vacuum are 2.21g/cm3 and 430 Mpa,respectively.This is because,in addition to the diflusion and reaction of silicon and carbon,the Si evaporation in vacuum can cause a loss of mass,and the open porosity increases distinctively,so the density and bending strength of the composite decrease slightly.