In-situ fabrication of Al2O3–SiC nanocomposites using B2O3 as sintering aid

Abstract

Abstract Al 2 O 3 –SiC nanocomposites with 5 and 10 vol% SiC have been in-situ fabricated by sol-gel method followed by carbothermal reduction of alumina–silica gel using B 2 O 3 as sintering aid. Green bodies were formed by cold isostatic pressing of calcined gel, which was prepared by an aqueous sol-containing aluminum chloride, TEOS, sucrose and boric acid. Pressureless sintering was carried out in Ar–12%H 2 atmosphere at 1700 °C. Addition of B 2 O 3 (1 or 3 wt%) was an effective densification aid in the Al 2 O 3 –5 vol% SiC composites, while the densification of Al 2 O 3 –10 vol% SiC composites was not affected by adding B 2 O 3 . The composite material containing 5 vol% SiC doped with 3 wt% B 2 O 3 reached 98.7% of full density. Nano-sized β-SiC particles were formed in-situ by means of a reaction between mullite and carbon at 1600 °C. Scanning electron microscopy revealed that the spherical in-situ synthesized SiC nanoparticles were well distributed through the composite and located predominantly to the interior of alumina matrix grains.