TEM study on the morphology and interface microstructure of C/C-SiC composites fabricated by liquid infiltration

Carbon fiber reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) have been widely used in aerospace field thanks to their superior high temperature properties. However, the interfacial microstructure of the composites is still not thoroughly understood in details. In this study, we focus on the morphology of the reaction-formed SiC and the interfacial microstructure between carbon and SiC in the C/C-SiC composites fabricated by liquid silicon infiltration performed at 1700 °C. The fine microstructure of the composites was investigated systematically by using transmission electron microscopy. The results show that two main types of interface are formed in the composites: (i) the fine-grained SiC is formed adjacent to the pyrolytic carbon, followed by a layer of coarse-grained SiC; and (ii) some extremely large SiC grains are formed directly on the pyrolytic carbon, and different pyrolytic carbon coatings can be connected by these large SiC grains. Additionally, some subgrains with grain size of a few tens of nanometers or even smaller can be found near the pyrolytic carbon or carbon fibers. The formation mechanism of the SiC/carbon interface is also discussed based on the fine microstructure observed.