基于Al-B-C烧结助剂的SiC_(nf)增强SiC陶瓷基复合材料制备及性能研究

Preparation and Properties of SiC_(nf) Nanofiber Reinforced SiC Ceramic Matrix Composites with Al-B-C Sintering Aids

以单晶碳化硅纳米纤维(SiC_(nf))为增强体,以铝(Al)粉、硼(B)粉和超细炭黑为烧结助剂,通过化学气相沉积及浸渍裂解工艺在SiC_(nf)上制备了PyC、BN双层界面包覆层,采用热压烧结法制备SiC_(nf)增强SiC陶瓷基复合材料(SiC_(nf)/SiC-CMC)。实验结果表明,Al-B-C烧结助剂在1850℃生成了液相Al8B4C7,促进了SiC陶瓷的致密化,提高了复合材料致密度。当烧结助剂含量为10wt.%时,随着Si Cnf含量的增加,复合材料内孔隙增多,致密度降低,抗弯强度和断裂韧性先增大后降低。当SiC_(nf)含量为10 wt.%时,复合材料的力学性能达到最优,抗弯强度和断裂韧性分别为414 MPa和9.65 MPa·m1/2,相较于未添加SiC_(nf)的热压烧结SiC陶瓷,其韧性提高了93.8%。微观结构分析表明,SiC_(nf)主要通过纤维拔出的方式来增加裂纹扩展时的能量消耗,达到提升陶瓷断裂韧性的效果。

SiC_(nf)reinforced SiC ceramic matrix composites(SiC_(nf)/SiC-CMC)were fabricated by using hot pressing sintering method with single crystal silicon carbide nanofibers(SiC_(nf))as reinforcement,aluminum(Al)powder,boron(B)powder and superfine carbon black as sintering aids.PyC and BN bi-layer interfacial phases were prepared on SiC_(nf)by using chemical vapor deposition(CVD)and impregnation cracking method.It is found that liquid phase Al8B4C7 was formed at 1850℃from the Al-B-C sintering aids,which promoted densification of the SiC ceramics and increased density of the composites.When the content of sintering aids is 10 wt.%,with increasing content of SiC_(nf),the porosity in the composite increases,the density decreases,the bending strength and fracture toughness first increase and then decrease.When the content of SiC_(nf)is 10 wt.%,mechanical properties of the composite are maximized,with bending strength and fracture toughness to be 414 MPa and 9.65 MPa∙m1/2,respectively.Compared with that of the hot-press sintered SiC ceramics without SiC_(nf),toughness of the composite is increased by 93.8%.As shown by the microstructure,the presence of SiC_(nf)can increase the energy consumption throughout crack propagation mainly through fiber pulling out,thus improving fracture toughness of the ceramic composites.