LI Chuxing, YU Jinshan, WANG Honglei, ZHOU Xingui
(Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, National University of Defense Technology, Changsha 410073, Hunan, China)
Abstract: Continuous silicon carbide fiber reinforced silicon carbide matrix composites (SiCf/SiC) are promising structure materials for high-temperature aerospace applications, due to their excellent properties such as high strength, high modulus, high temperature resistance and strong oxidation resistance. Interface layer phase as an extremely important part of composites has the function of protecting the fibers, bearing load, transferring the stress and so on. Especially, the insertion of boron nitride interface layers can effectively enhance the mechanical properties of SiCf/SiC composites. Two boron sources, borazole and BCl3, were used to produce the BN interface layer by using CVD process, while pyrolytic carbon was deposited by using CVI process to prepare SiCf/C and then the SiCf/SiC composites were fabricated by using VSI process. Fourier transform infrared (FTIR) spectroscopy, SEM, TEM, nano indentation and nano CT were used to study morphologies and structures of the BN interface layers. The effects of the interface layers on properties of the composites and the relationship between properties and structures of composites before and after the VSI process were evaluated. Bending strength of the SiCf/SiC sample is up to 294.66 MPa, while the porosity and fracture toughness are 1.65% and 14.59 MPa·m1/2, respectively.
Key words: chemical vapor deposition; BN; interface layer; vapor silicon infiltration; silicon carbide; composites