Preparation of AI₂O₃-Tic composites using microwave energy

Abstract

The combustion synthesis of AI₂O₃-47wt%TiC powder was performed in a 2.4 kW, 2.45 GHz microwave furnace. The combustion system of TiO₂-Al-C was investigated using various types of precursor, i.e. TiO₂ (rutile and anatase) and c (carbon black, graphite and activated carbon). Combustion under microwave energy could be achieved in less than 3 min which was 60 times faster than conventional combustion. The composition of rutile- carbon black-aluminum gave the shortest ignition time, whereas anatase-activated carbon- aluminum had the highest combustion temperature. The XRD pattern showed incomplete combustion of product that used activated carbon as the carbon source. The pressureless sintering of synthesized powder was progressed at 1800°c with MgO and Y₂O₃additive. The synthesized powder M-TC1 could be sintered to nearly theoretical density (95.9%TD). The corresponding hardness, facture toughness and flexural strength were 14.2 GPa, 5.19 MPa.m[superscript ½]and 321 MPa respectively and these were approached to the literature report. The physical and mechanical properties of sintered microwave- combusted powders were inferior to the conventional ones. It was though that a longer time in conventional synthesis led to more densified reactive AI₂O₃-47wt%TiC powders. From the preliminary microwave sintering result, the highest density sintered sample achieved was 82%TD at 1500°c under 2.4kW. The microwave sintered sample had a tendency to obtain a nearly full densification at lower temperature compared to conventional process. However the obstacle to reach a higher sintering temperature is focussed on the relationship among sample loading, competition in microwave energy between sample and susceptor, and also the amount and configuration of susceptor used. This understanding will assist densification efforts.