Evolution of the novel C/SiO2/SiC ternary aerogel with high specific surface area and improved oxidation resistance

Abstract

A novel C/SiO2/SiC ternary aerogel is derived from catechol-formaldehyde/silica hybrid aerogel (CF/SiO2) via a one-step sol-gel method followed by carbonization and carbothermal reduction processes under flowing argon. The effects of the carbon/silica molar ratios on the physicochemical properties of the C/SiO2 binary and C/SiO2/SiC ternary aerogel are investigated. The mechanism of the textural and structural evolution for the novel C/SiO2/SiC ternary aerogel is further discussed based on the experimental results and the calculated Gibbs free energy changes at different SiO partial pressure. The SiC layer is first formed on the surface of the composite aerogel via the solid-vapor reaction at 1400°C while SiC nanoparticles form at 1500°C. The C/SiO2/SiC ternary aerogel possesses a rather high specific surface area (746.87m2/g), a high micropore volume (0.2279cm3/g) and a high porosity (89.10%). The oxidation resistance is improved for 100°C when compared with the carbon based aerogel. The ternary aerogel obtains a high compressive strength (1.86MPa) and a low thermal conductivity (0.053W/m*K), which is suitable for high efficient thermal insulation uses both in inert and oxidative atmosphere.