Twin step synthesis of mullite and mullite–zirconia composite in low power transferred arc plasma (TAP) torch

Mullite and mullite-zirconia composites were prepared in twin step through low power transferred arc plasma (TAP) torch melting followed by mechanical mixing. The mixture was based on 3:2 mole ratios of alumina and silica; alumina and zircon were ball milled and melted for 3 min in a transferred arc plasma torch at 3 kW input power with 10 lpm of argon flow rate. The phase and microstructure formation of the melted samples was investigated by XRD and SEM respectively. The crystalline behavior of the mullite and mullite–zirconia composite was evaluated by differential thermal analysis. The obtained results clearly showed that the complete mullization was achieved only in alumina–silica system and partial mullization occurred in alumina–zircon system due to the inadequate plasma torch input power.