Synthesis and toughening effect of SiC nanowires wrapped by carbon nanosheet on C/C composites

SiC nanowires wrapped by carbon nanosheet have been synthesized by chemical vapor deposition using methyltrichlorosilane as precursor at standard atmospheric pressure. The morphological and structure of as-received products were characterized. The nanowires consist of a single-crystalline β-SiC core and a carbon nanosheet shell. The diameter of β-SiC core is about 30 nm. The thickness of carbon nanosheet is about several nanometers. The carbon nanosheet is polycrystalline graphite. EELS analysis of different elements in nanowires further prove that the nanowires are carbon nanosheet wrapped SiC nanowires. To verify its toughening effect, SiC coating has been also deposited in the porous carbon nanosheet wrapped SiC nanowires layer by chemical vapor deposition at low pressure. The thermal shock tests showed that the weight loss of SiC nanowires wrapped by carbon nanosheet-toughened SiC coated C/C composites was only 2.38% after 25 times thermal cycling between 1773 K and room temperature. The incorporation of carbon nanosheet wrapped SiC nanowires can effectively improve the toughness and thermal shock resistance of SiC coating on C/C composites via cracks pining and deflection.