Synthesis and characterization of mullite–zirconia nanostructured composite by combined mechanical activation and reaction sintering

Abstract

The objective of present study was to produce mullite–zirconia nanostructured composite by mechanical activation of zircon–alumina powder mixture followed by reaction sintering. The results showed that mechanical activation up to 60h led to no phase change. Complete formation of mullite–zirconia composite was observed after 60h of mechanical activation and subsequent reaction sintering at 1400°C for 2h. This temperature is about 200–250°C lower than the temperatures commonly used in the reaction sintering of zircon–alumina powder mixture. Density measurements showed that the relative density of green bodies was ∼78%, which increased to values above 90% after reaction sintering. It was also observed that the relative density of reaction sintered samples increased with an increase in the mechanical activation time. The produced composite showed a hardness value of 11.1GPa, which is comparable with the hardness value of mullite–zirconia composites obtained by other methods.