Anti-oxidation performance of carbon aerogel composites with SiCO ceramic inner coating

To improve the oxidative-resistant ability of carbon fibre-reinforced carbon aerogel composites (C/CAs), C/CAs were impregnated with a silicon oxycarbide (SiCO) precursor sol several times. After gelating, aging, solvent exchanging, ambient drying, and pyrolyzing, the SiCO precursor sol infiltrated the nanoporous C/CA, and anti oxidation carbon aerogel composites with a SiCO ceramic inner coating (C/CA-SiCO) were prepared. It was found that the density of the material increases with the number of times that impregnation and pyrolysis were carried out. The mechanical properties and the anti-oxidant performance were significantly improved after the deposition with different numbers of the SiCO coating cycles. The bending strength increased from 2.2 MPa to 10.8-32.3 MPa and the compressive strength (10%epsilon) increased from 0.4 MPa to 3.6-44.4 MPa. The weight loss for the as-prepared composites after heating at 1600 degrees C for 60 min in air was only 7.6%, and the in-plane shrinkage was less than 2%. Additionally, after the oxidation resistance test, the surface of the C/CA-SiCO had abundant beta-SiO2 crystalline, whereas its inner region of the composite remained amorphous.