Fine study of hierarchical interphase constructed by boron nitride and carbon nanotubes in SiC_f/SiC composites

Abstract

A fine study of the interfacial part in the silicon carbide fiber (SiCf) reinforced silicon carbide (SiC) composites was conducted by transmission electron microscopy. The boron nitride (BN) and carbon nanotubes (CNTs) were progressively coated on the SiCf by chemical vapor deposition method to form a hierarchical structure. Three composites with different interfaces, SiCf–CNTs/SiC, SiCf@BN/SiC, and SiCf@BN–CNTs/SiC, were fabricated by polymer infiltration and pyrolysis method. The interfaces and microstructures of the three composites were carefully characterized to investigate the improvement mechanism of strength and toughness. The results showed that BN could protect the surface of SiCf from corrosion and oxidation so that improved the possibility of debonding and pullout. CNTs could avoid the propagation of cracks in the composites so that improved the damage resistance of the matrix. The synergistic reinforcement brought by BN and CNTs interfaces made the SiCf@BN–CNTs/SiC composites with a tensile fracture strength as high as 359 MPa, with an improvement of 23% compared to that of SiCf@BN/SiC.