LOU Yongwei, CHEN Hao, CHEN Jianjun
(Institute of Advanced Ceramic Material & Fiber, School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou 310018, Zhejiang, China)
Abstract: SiCnf reinforced SiC ceramic matrix composites (SiCnf/SiC-CMC) were fabricated by using hot pressing sintering method with single crystal silicon carbide nanofibers (SiCnf) 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 SiCnf 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 SiCnf, the porosity in the composite increases, the density decreases, the bending strength and fracture toughness first increase and then decrease. When the content of SiCnf 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 SiCnf, toughness of the composite is increased by 93.8%. As shown by the microstructure, the presence of SiCnf can increase the energy consumption throughout crack propagation mainly through fiber pulling out, thus improving fracture toughness of the ceramic composites.
Key words: SiCnf-reinforced SiC ceramic matrix composites; Al-B-C sintering aids; hot pressing sintering; the fracture toughness