Nickel-catalyzed preparation of self-bonded SiC refractories with improved microstructure and properties

3C-SiC was synthesized after 3 h firing of Si and expanded graphite in flowing Ar at 1300 degrees C with in-situ formed Ni nanoparticle (NP) catalyst. First-principles calculations suggest that Ni catalyst accelerated the formation of SiC via weakening the bonds in adsorbed C=C bond, and CO and SiO molecules. Apart from this, Ni NP catalyst facilitated the epitaxial growth of SiC nanowires. Based on these findings, self-bonded SiC refractories were prepared by using black SiC grain, expanded graphite and Si powders as raw materials and Ni NP as a catalyst. Large amounts of SiC nanowires were catalytically formed in the fired refractories specimens, which resulted in significant improvements in both mechanical strength (MOR of 32.2 MPa at 1400 degrees C) and thermal shock resistance. The catalytic formation method investigated in this work could be readily modified and extended to develop many other types of high performance refractories.