Formation and growth of in-situ SiC nanowires in Al2O3–C materials under various atmospheres

Abstract

The Al2O3–C materials were fabricated using tabular alumina aggregates and fines, Si powder and resin powder as starting materials. The effect of firing atmosphere on the in-situ formation of SiC nanowires (NWs) at elevated temperatures was investigated. The results show that Al2O3–C samples with superior performance were prepared via a simple process using phenolic resin powder as carbon source and binder. Si reacted with resin powder to form SiC NWs in Al2O3–C materials at high temperature, which created strengthening and toughening effects resulted in increasing mechanical properties. Firing atmosphere had great effect on formation and growth of in-situ SiC NWs, reducing atmosphere could promote Si reacting completely at lower temperature, and morphology of SiC NWs was different under various atmosphere. The linear SiC NWs with relatively smooth surface formed under weak oxidizing atmosphere, SiC NWs with rough surface and irregular diameter formed under reducing atmosphere, and SiC NWs with bamboo-like and chain-bead morphologies formed under weak reducing atmosphere. The length of SiC NWs was in micrometer scale and less than 200 nm in diameter. The growth process of SiC NWs was governed by solid-vapor between Si (s) and CO (g) or C (s) and SiO (g), liquid-vapor between Si (l) and CO (g), and vapor-vapor between SiO (g) and CO (g).