Densification Study and Mechanical Properties of Microwave-Sintered Mullite and Mullite-Zirconia Composites

Abstract

The objective of this research is to evaluate microwave sintering as a viable technique to reliably process high-strength mullite and mullite-zirconia composites. In this report, the advantage of microwave processing over conventional heating is realized by comparing the densification behavior and mechanical properties of sintered mullite and mullite-zirconia composites. Commercially procured mullite powders were sintered using a 3 kW, 2.45 GHz microwave furnace in the range of 14001-15001C, for 1 h. For pure mullite, an increase in sintering temperature from 14001 to 15001C decreased the porosity from 30% to 13%, which increased the compressive strength from 128718 to 387721 MPa with 1 wt% MgO as a sintering aid to mullite. Furthermore, yttria-stabilized tetragonal zirconia (3Y-TZP) was incorporated (up to 20 wt%) to improve the microwave absorption efficiency of mullite. A maximum density of 92% can be achieved for mullite with 1 wt% MgO and 10 wt% ZrO 2 composites sintered at 15001C in microwave furnace and exhibited a maximum hardness of B10.2470.61 GPa, compressive strength of B740738 MPa and a moderately high indentation fracture toughness of B3.6570.43 MPa . m 1/2 . Microwave sintering data, when compared with those of conventional sintering, revealed that volumetric heating of microwaves led to considerable improvement in strength of mullite and mullite-zirconia composites while utilizing reduced time and energy.

Effect of microwave sintering on microstructure and mechanical properties in Y-TZP materials used for dental applications

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Hydrothermal Degradation Behavior of Y‐TZP Ceramics Sintered by Nonconventional Microwave Technology

“…Microwave heating consists on the absorption of electromagnetic radiation by materials due to their intrinsic dielectric properties. 21,22 It differs greatly from CS because heat-transfer mechanisms are not the driving force for densification but rather the conversion of electromagnetic energy into thermal energy within the material. Therefore, the temperature gradient is created from the material bulk toward the surface.…”

Phase Evolution, Microstructure, and Mechanical Properties of Alumina–Mullite–Zirconia Composites Prepared by Iranian Andalusite

“…This resulted in the formation of mullite, a phase with the less density. The sintering of mullite by conventional processing require a high processing temperature as the diffusion kinetics of Si 4+ and Al 3+ ions are slow . It was therefore difficult to attain high density in these composites.…”