Effect of mechanical activation and microwave sintering on crystallization and mechanical strength of cordierite nanograins

In this study mechanical activated powders were synthesized by high-energy ball milling of starting powders containing 34.86 wt% Al2O3, 51.36 wt% SiO2, and 13.78 wt% MgO. The activated powders were then sintered by either conventional or microwave sintering methods at temperatures between 900 and 1400 °C and the crystallization and sintering behavior of the samples were investigated. SEM observations showed that microwave sintering of the 30 h milled sample led to a microstructure consisting of equiaxed nanograins with average grain size of 38 nm. The specimens that were sintered by the microwave method exhibited lower porosity, higher density and higher bending strength compared to those sintered by the conventional method. The mechanical strength of the materials was evaluated by three-point bending test and the optimum sample, which was milled for 30 h and microwave sintered at 1390 °C, showed a maximum strength of 110±5 MPa.