Microstructural evolution and mechanical properties of in situ nano Ta4HfC5 reinforced SiBCN composite ceramics
Bingzhu Wang, Daxin Li, Zhihua Yang, Dechang Jia, Jingyi Guan, Hao Peng, Delong Cai, Peigang He, Xiaoming Duan, Yu Zhou, Tao Zhang, Chenguang Gao
Abstract
Abstract The in situ nano Ta 4 HfC 5 reinforced SiBCN-Ta 4 HfC 5 composite ceramics were prepared by a combination of two-step mechanical alloying and reactive hot-pressing sintering. The microstructural evolution and mechanical properties of the resulting SiBCN-Ta 4 HfC 5 were studied. After the first-step milling of 30 h, the raw materials of TaC and HfC underwent crushing, cold sintering, and short-range interdiffusion to finally obtain the high pure nano Ta4HfC5. A hybrid structure of amorphous SiBCN and nano Ta 4 HfC 5 was obtained by adopting a second-step ball-milling. After reactive hot-pressing sintering, amorphous SiBCN has crystallized to 3C-SiC, 6H-SiC, and turbostratic BN(C) phases and Ta 4 HfC 5 retained the form of the nanostructure. With the in situ generations of 2.5 wt% Ta 4 HfC 5 , Ta 4 HfC 5 is preferentially distributed within the turbostratic BN(C); however, as Ta 4 HfC 5 content further raised to 10 wt%, it mainly distributed in the grain-boundary of BN(C) and SiC. The introduction of Ta 4 HfC 5 nanocrystals can effectively improve the flexural strength and fracture toughness of SiBCN ceramics, reaching to 344.1 MPa and 4.52 MPa·m 1/2 , respectively. This work has solved the problems of uneven distribution of ultra-high temperature phases in the ceramic matrix, which is beneficial to the real applications of SiBCN ceramics.