Effect of Microwave Radiation on the Properties of Sintered Oxide Ceramics

Recent research has been significantly increased our fundamental understanding of microwave interactions with materials. Thermal absorption has been demonstrated to result from simultaneous action of multiple dissipation mechanisms during processing. In addition, it has been conclusively established that strong microwave fields exert a non-thermal driving force during sintering. This force acts as an additional driving force for atomic transport. For strong electric fields, the force can enhance diffusion rates during ceramic sintering. This paper describes recent research on microwave sintering of two oxide ceramics, a silica xerogel ceramic produced from rice husk ash (RHA) and a high purity alpha alumina. A millimeter waves (MMW) heating system with a 28 GHz gyrotron is applied for microwave sintering experiment. The ceramics were also sintered by using an electric furnace where served as comparison. Effect of microwave energy on the porosity reduction of the ceramics was investigated. Some possible physical mechanisms were discussed.