Preparation and characterization of C/Al2 O3 composite aerogel with high compressive strength and low thermal conductivity

Carbon/alumina (C/Al2O3) composite aerogel with high compressive strength and low thermal conductivity has been successfully synthesized by sol-gel method, followed by CO2 supercritical drying and carbonization. SEM images and compressive Young's modulus measurements show that the C/Al2O3 aerogel with a molar ratio of Resorcinol/Alumina (R/Al) of 1.0 presents homogeneous pore structures and obtains excellent compressive Young's modulus up to 90 MPa. Three weight losses regions are observed during heat treatment process, confirmed by TG/DSC measurements. XRD patterns and TEM images indicate that alpha-Al2O3 phase transition occurs only when heat treatment temperature reaches up to 1500 A degrees C with the adding of carbon source, 200 A degrees C higher than pure Al2O3 aerogel. The as-dried RF/Al2O3 aerogel possesses thermal conductivity as low as 0.025 W m(-1) K-1. The thermal conductivities of C/Al2O3 aerogels increase gradually with the increase of heat treatment temperatures, caused by increasing solid thermal conductivity. The thermal conductivities range from 0.033 to 0.049 W m(-1) K-1, suitable for efficient thermal insulations uses.