ZrO2–SiO2 gradient multilayer oxidation protective coating for SiC coated carbon/carbon composites

In order to eliminate the mismatch of thermal expansion coefficient between the ZrO2 outer layer and the internal bonding SiC layer, ZrO2–SiO2 composition-gradient transition layers were prepared by a sol–gel technique using tetraethoxysilane (TEOS) and zirconyl chloride as source materials. Energy dispersive spectroscopy (EDS) analysis displays that the gradient composition ZrO2–SiO2 outer coating could be obtained by immersing the SiC precoated carbon/carbon (C/C) composites into the gradient composition zirconia-silica sols (ZS sol) in turn. Oxidation test shows that, after 10 h oxidation in air at 1773 K, the weight loss of the gradient ZrO2–SiO2 coating coated SiC-C/C is only 1.97%.