Fabrication of Al2O3 Microtubes Using Carbon Fibers and Al/ Al2O3 Mixed Powder in Solid-Vapor Reaction (SVR) Process

Abstract

In this work, we report on the fabrication process of alumina (Al2O3) microtubes using carbon fibers and aluminum/alumina (Al/Al2O3) mixed powder via a solid-vapor (SV) reaction. Al and Al2O3 (α-Al2O3) were mixed in a 1:1 molar ratio, and heated to generate an AlO vapor. The carbon fibers were heat-treated in the pre-carburized Al2O3 crucible at 1400°C for 9h with a heating rate of 5°C/min in flowing argon (Ar) gas at 200 ml/min. Any carbon residues remaining in the core after the heat treatment at 1400°C were burned off by subsequent calcination at 700°C for 3 h in air. A post-heat treatment was conducted to convert the product to Al2O3. As a result, Al2O3 microtubes are successfully synthesized via the SV reaction between carbon fibers and Al/Al2O3 mixed powder. The TGA study shows that the AlO vapor is generated at temperatures above 750°C. As the calcination temperature increases, carbon residues and Al4C3 peaks disappear in XRD patterns. Al2O3 microtubes are synthesized at 1200°C, and show thinner wall thickness and undulating outer and inner surfaces arising from the partial decomposition of Al2O3 microtubes.