Microstructural evolution of carbon fibers by silicon vapor deposition and its effect on mullite-corundum castables

Y Carbon fibers (CFs) can be introduced to castables, due to the relative higher thermal conductivity and stronger damping properties. In this research, microstructural evolution of carbon fibers (CFs) in the presence of mixture of silicon and silica powders under the protection of carbon black was studied in the temperature range of 1000-1300 degrees C by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that some small amorphous SiOx globules were formed on the surface of CFs at the temperature below 1200 degrees C. With the increase of the treated temperature, the size of globules became bigger and reached maximum at 1200 degrees C. The growth of SiOx globules can be controlled by vapor-solid mechanism. In addition, the effects of these CFs on properties and microstructure of mullite-corundum castables were studied. The results showed that the CFs with SiOx globules (CFs/SiOX) could significantly improve the mechanical properties of the castables because the interfacial bonding strength between CFs/SiOx and matrix is much stronger than the untreated CFs.