Comparative study of microwave and conventional processing of MgAl2O4-based materials

A comparative study of microwave and conventional processing of ceramic materials based on MgAl2O4 is presented in this paper, in particular sinters obtained from MgO and Al2O3 with 1 wt.% of CaO as an additive, and Al2O3–MgAl2O4 composites. Microwave processing took place under air at 800 W and 2.45 GHz during 4.5 min, conventional processing in an electrical resistance furnace, also on air, was conducted at 1400 °C for 96 h. The MgO:Al2O3 weight ratio employed for the synthesis of MgAl2O4 was 1:2.45. According to semi-quantitative X-ray diffraction analysis, approximately 90% of MgAl2O4 was produced with both processing methods. Scanning electron microscope (SEM) images of the microstructure revealed a similar morphology for the two methods, nevertheless the grain size was different. The Al2O3:MgAl2O4 weight ratios for the production of the composites were 9:1, 1:1, and 1:9 using the two methods and the conditions already described. A heterogeneous microstructure was observed in the specimen processed by microwaves. Due to the different nature of the processes, an extensive property was compared against an intensive one, therefore, the aim of this work was to have a realistic comparison between the materials obtained with these processes by taking into account energetic as well as kinetic aspects.