Characterization of latticed SiC nanowires containing coating for carbon foam using carbonization activated pack cementation process

In order to improve the oxidation resistance of carbon foam, a silicon carbide (SiC) coating was prepared using carbonization-activated pack cementation method. Carbon foam was firstly carbonized partially at 500 °C and then fully carbonized at 1600 °C with pack powder containing activated carbon, silicon powder, and iron chloride. The as-obtained coating was characterized using scanning and transmission electron microscopies, X-ray diffraction, thermogravimetric analysis, oxidation thermal shock and coefficient of thermal expansion. The results showed that the coating was mainly composed of randomly distributed SiC nanowires extended inside the surface pores forming pinning effect. The growth mechanism involved dissolution of SiO and CO (vapors) in the Fi-Si melt (liquid) and precipitation of one-dimensional SiC nanowires (solid). In non-isothermal oxidation, the coated carbon foam showed a mass loss of only 1.97%. The thermal shock results indicated that due to matching of thermal expansion coefficients, no cracks occurred on the surface after 15 cycles under temperature drop of 1475 °C. Consequently, we expect that this new high temperature coating method, and the subsequent microstructure that it creates, can be widely applied to improve the thermal shock and oxidation resistance of carbon foam.