Antioxidant modification of C/C composites by in situ hydrothermally synthesized 4ZnO·B₂O₃·H₂O

Antioxidant modification of carbon/carbon (C/C) composites by in situ hydrothermally synthesized 4ZnO·B₂O₃·H₂O was successfully achieved. Samples were characterized by X-ray diffraction, scanning electron microscopy, isothermal oxidation test and thermogravimetry/differential scanning calorimetry. The influence of hydrothermal temperature on the phase composition and microstructure of as-prepared 4ZnO·B₂O₃·H₂O, and the antioxidant modification of C/C composites were investigated. Results showed that 4ZnO·B₂O₃·H₂O crystallite coating was achieved on the surface of C/C composites at the hydrothermal temperature range of 100-180°C. A smooth and crack-free 4ZnO·B₂O₃·H₂O layer was obtained when the hydrothermal temperature reached 140°C. The isothermal oxidation test showed that the oxidation resistance of C/C composites was improved. The as-modified composites exhibited a weight loss of only 1.93 g/cm³ after oxidation at 600°C for 15 h, while the non-modified one had a weight loss of 5.20 g/cm³ after only 10 h of oxidation.