Microwave sintering of ceramics, composites and metal powders: Recent developments

New developments and innovative ideas in the area of materials processing have often led to the discovery of new materials, with interesting and useful properties, and/or new technologies. The use of microwave energy in the area of materials processing is one such new development. Microwave processing has several advantages over conventional sintering, such as the reduction in cycle time, potential for reduction in manufacturing costs, retaining fine microstructures leading to improved mechanical properties and overall performance of the product. For over 15 years a wide variety of oxide ceramics, non-oxide cermets, and transparent materials have been processed using microwave techniques. The latest surprising development in this field is the sintering of powder metals in a microwave field. It is surprising because metals are known to reflect microwaves. This paper summarizes the important developments in microwave processing of ceramics, composites and metallic materials, which have taken place at the Materials Research Lab of the Penn State University. Main areas of focus will include: hydroxyapatite, various traditional and advanced electroceramics, alumina, cemented carbide, powder metals, transparent ceramics, and designing of microwave systems, etc. In general, the research has demonstrated that in case of almost all materials processed in microwave field, near theoretical densities and better properties than conventional product, were achieved at much lower sintering temperatures and times.