Toughening by <scp> <scp>SiC</scp> </scp> Nanowires in a Dense <scp> <scp>SiC</scp> </scp> – <scp> <scp>Si</scp> </scp> Ceramic Coating for Oxidation Protection of <scp> <scp>C</scp> </scp> / <scp> <scp>C</scp> </scp> Composites

Abstract

A dense oxidation protective SiC – Si ceramic coating with well‐dispersion SiC nanowires was prepared on carbon/carbon ( C / C ) composites using a two‐step technique consisting of chemical vapor deposition and hot‐pressing reactive sintering. The results showed that the toughness and thermal shock resistance of the coating were dramatically improved, resulting in an excellent oxidation protection for the coated C / C composites, which is attributed primarily to the toughening effects of SiC nanowires in the coating including two special energy dissipation mechanisms involving the super‐plasticity deformation of SiC nanowires and the plastic fracture at the interface of the nanowire‐matrix, except for nanowire pullout, nanowire bridging, and microcrack deflection. More importantly, a novel oxidation protective failure mechanism of the coated C / C composites revealed that the presence of Al 3+ in the coating, damaged the network structure of SiO 2 glass and resulted in the slight oxidation of C / C composites.