Joining Ceramics Using Microwave Energy

In the past several years there has been an explosive growth in the use of microwave energy for the processing of a host of materials. Microwave energy provides rapid internal heating which results in an overall reduction in the processing time. The important features of microwave processing are described, as well as several applications.Microwave energy has been used by a few groups for the joining of alumina, mullite, silicon nitride and silicon carbide. The work performed by these groups will be reviewed. Typically, a single mode microwave applicator has been used to join ceramics at temperatures ranging between 1250°C - 1800°C. Microwave joining of ceramics was achieved in a matter of minutes, in contrast to hours reported by conventional methods. The strength of the joints was equal to or greater than the as-received materials. Joining of specimens of sintered silicon carbide (Hexoloy ™ ) using interlayers, and direct joining of reaction bonded silicon carbide (RBSC) to itself and Hexoloy™ has been accomplished recently. Both single mode and multimode microwave applicators were used and larger specimens of RBSC having complex shapes were joined using hybrid heating. The paper describes microwave joining apparatus, techniques and results.