Interface Formation of Unidirectional SiC_f/SiC Composites by Electrophoretic Deposition Method

Abstract

C-and BN-interphases on SiC fibers for unidirectional SiCf/SiC composites were formed by EPD process, and their microstructure and mechanical properties were investigated. Whereas the C-SiCf/SiC composites showed a pseudo-ductile fracture behavior with large amount of fiber pullout, the BN-SiCf/SiC composites fractured in a brittle manner without fiber pullout in spite of sufficient thickness of BN interphase. It is inferred from the results of EDS that sintering additives would react with h-BN-interphase, and the interphase did not act effectively for toughening the SiCf/SiC composites.

Mechanical properties of SiCf/SiC composites with h‐BN interphase formed by the electrophoretic deposition method

“…We have already demonstrated that the EPD method is effective to form the carbon interphase on SiC fibers and SiC f /SiC composites with the carbon interphase formed by EPD shows excellent mechanical properties. [17][18][19][20][21][22][23][24] In addition, the application of the EPD process is considered to be difficult to form the interphase on SiC fibers with low electric conductivity, but our group demonstrated that polypyrrole (Ppy) coating on the low-conductive SiC fibers was very effective to improve their surface electric conductivity, and uniform and sufficient carbon coating was successfully formed on the SiC fibers by EPD for achieving highperformance SiC f /SiC composites as well as conventional gas-phase-based process. 25 In this study, the present authors focused on the h-BN interphase, which shows better oxidation resistance than carbon, and tried to form dense and uniform h-BN coating on low-conductive SiC fibers by the EPD method using flaked h-BN suspension prepared by wetjet milling.…”

“…The EPD process for the interphase formation on SiC fibers has some advantages compared with conventional gas‐phase‐based process; interphase coating on SiC fibers can be formed in very shorter time, the EPD process is very simple, less‐costly and environmentally benign, it does not need complicated apparatus, and the layered interphase can be easily formed on SiC fibers by the deposition of plate‐like particles. We have already demonstrated that the EPD method is effective to form the carbon interphase on SiC fibers and SiC f /SiC composites with the carbon interphase formed by EPD shows excellent mechanical properties 17–24 . In addition, the application of the EPD process is considered to be difficult to form the interphase on SiC fibers with low electric conductivity, but our group demonstrated that polypyrrole (Ppy) coating on the low‐conductive SiC fibers was very effective to improve their surface electric conductivity, and uniform and sufficient carbon coating was successfully formed on the SiC fibers by EPD for achieving high‐performance SiC f /SiC composites as well as conventional gas‐phase‐based process 25 …”