Microstructures and mechanical properties of Al2O3–C refractories using nickel-loaded ultrafine microcrystalline graphite and silicon additives

Abstract

Ultrafine microcrystalline graphite (UMCG) and nickel-loaded ultrafine microcrystalline graphite (NMCG) were introduced into Al2O3–C refractories to totally replace graphite flake (GF), respectively. Their interactions with silicon additive were exploited through the observation of microstructures, mechanical and thermo-mechanical properties of Al2O3–C refractories after firing at 800–1400°C in a coke powder bed. It revealed that with NMCG, carbon nanotubes and SiC whiskers are in-situ formed out of nickel-catalytic pyrolysis of phenol resin binder at the temperature low to 1000°C. Moreover, the amount of SiC whiskers increases with increasing fire temperature. The synergistic effect of the ultrafine microcrystalline graphite, carbon nanotubes and SiC whiskers contributes to the substantial improvement of mechanical properties and thermal shock resistance of Al2O3–C refractories using nickel-loaded ultrafine microcrystalline graphite as carbon source.