The effects of graphene nanoplatelet addition to in situ compacted alumina nanocomposites using ultra-high frequency induction sintering system

Abstract

The aim of this study was to compact and sinter in situ graphene nanoplatelets (GNPs) with the addition of alumina (Al2O3) nanoparticles to form nanocomposites by using an ultra-high frequency induction sintering system with the assistance of applying a uniaxial load. To obtain the effect of the addition of GNPs to the compaction and to the mechanical properties of the nanocomposite, 1 to 5 wt.% GNPs was mixed to alumina nanoparticles by high-speed ball milling for 2 h at 350 rpm. Mixed Al2O3-GNP compositions were compacted in situ and sintered in a graphite die by induction-assisted heating at 1650 °C for 20 min with a uniaxial load applied in a vacuum chamber. The microstructure of as-sintered nanocomposites was observed using a scanning electron microscope (SEM) before and after thermal etching. Hardness and wear tests were carried out to determine mechanical properties. The results were compared with the properties of a pure alumina nanocompact. It was found that minimum grain size and maximum density, hardness, and wear resistance can be obtained by the addition of 1 wt.% GNPs to alumina nanoparticles. Higher amounts of GNP addition gradually decreased the density, hardness, and wear rates and increased the grain size of the alumina matrix. © 2019, Australian Ceramic Society.