Synthesis of Functional Materials Based on Electromagnetic Processing

Abstract

Materials fabrication based on millimeter (MM)-wave and pulsed high current (SPS) heating processes have been reviewed and characteristics of these processes are discussed from the standpoints of the interaction between electromagnetic energy and solid materials. Capabilities of these processes in the fabrication of functional materials are indicated by exemplifying several successful results such as highly-strengthened or nano-structured alumina, highly thermal conductive AlN and preferentially oriented dense nano-structured anatase. In MM-wave heating process, the interactions between millimeter-wave and charged species in solid, such as ponderomotive force, have the important roles on the consolidation of powder materials, while atomistic mechanism in SPS heating process has not been explained well, though pulsed high current effect is important. Synthesis of pseudobinary T-Al-N (T: transition element) coatings by PVD process is also reviewed as an example of the processes assisted by electromagnetic energy. Hardness of the nitride coatings can be improved by dissolving AlN into TN and the formation of pseudobinary hard phase dissolved AlN is qualitatively explained by the pressure effect of energetic particle bombardment in PVD process. The experimental values of the maximum solubility of AlN into TN show good agreement with the values predicted by the band parameters method, indicating the importance of prediction based on electronic picture.