Oxidation behavior of carbon/carbon composites coated with a SiSiOx/BNB2O3SiO2Al2O3 oxidation protection system at intermediate temperature

• Anti-oxidation properties of a SiSiOx/BNB2O3SiO2Al2O3 dual-layer coating are investigated.
• The SiSiOx/BNB2O3SiO2Al2O3 coating has a good oxidation protection ability at intermediate temperature.
• The SiSiOx layer can densify the pores in C/C composites efficiently and improve the oxidation resistance of the samples.
• The oxidation kinetics model of the SiSiOx/BNB2O3SiO2Al2O3 corresponds to two different oxidation mechanisms.

To improve the oxidation behavior of carbon/carbon composites at intermediate temperature, we developed a SiSiOx/BNB2O3SiO2Al2O3 coating by chemical vapor deposition and sol-gel slurry method. The coating exhibited a dual-layer structure with a dense SiSiOx inner layer and a BNB2O3SiO2Al2O3 multi-phase outer layer. The influence of SiSiOx on the C/C composites surface densification was investigated. The results showed that the weight losses of the coated C/C composite after oxidation for 162 h at 700 °C, 162 h at 800 °C, 162 h at 900 °C, 142 h at 1000 °C and 102 h at 1100 °C were 0.92, 3.04, 2.66, 2.93 and 3.81 wt%, respectively. It also performed excellent thermal shock resistance in the above temperature range. The oxidation kinetics of the coated carbon/carbon composites was proposed by Arrhenius equation as two different oxidation phases and mechanisms. The great oxidation resistance and thermal shock resistance were attributed to the formation of a dense B2O3 glass or SiO2-rich borosilicate glassy film covering on the C/C substrate during oxidation. This study provided an oxidation protection system at intermediate temperature.