Heating of ceramic joints by a high-power 83-GHz millimeter-wave beam

The high power beams which can be generated by CW gyrotrons represent a promising new energy source for high-temperature processing of materials. An experimental facility based on an 83-GHz, 15-kW CW industrial gyrotron, produced by Gycom, Ltd., has been set up at the Naval Research Laboratory to investigate novel mm-wave-beam-based approaches to processing ceramic materials including sintering, coating, and joining applications. Current experimental and theoretical studies are investigating the formation of strong bonds between ceramics and between ceramics and metals using controlled, selective heating of the joint region. The development of a successful joining process requires a consideration of the material thermal and dielectric properties to model the response to energy deposition by the beam. In this paper a method of evaluating the time-dependent temperature profile in the joint region is discussed. The region is treated as a composite system comprised of slabs of dielectric material, and the heat conduction problem including heat generation is solved using a Green's function approach. The modeling studies are being used to guide joining experiments in progress. Available results will be presented.