Micro-focusing effect of electromagnetic fields and its influence on sintering during the microwave processing of ceramic particles of SiC

Microwave sintering is an efficient technology for the rapid preparation of high-performance ceramic materials. Here, an investigation has been performed on the intensity distribution of microwave electric fields in a SiC ceramic powder system and its effect on the sintering behaviour. The results show that the microstructure of the “ceramic-void” will induce a non-uniform distribution and a micro-focusing effect of microwave electric fields in some regions (e.g., the neck) during microwave processing. This effect may be an important factor for the increase of mass diffusion and the rapid densification process observed with microwave sintering. However, this effect is not always prominent throughout the entire sintering process, and it will decline as the neck grows larger. Furthermore, the micro-focusing effect on the non-smooth and the sharp portion of the particle׳s surface has also been examined. These results were verified by SR-CT experimental observations of the microstructure evolution of ceramic powders during an entire uninterrupted microwave sintering process.