Microwave joining of dissimilar SiC ceramics

Tubes of sintered silicon carbide have been joined to sockets of reaction bonded silicon carbide as a first step in the fabrication of tube assemblies for ceramic heat exchangers. An end tube section of reaction bonded silicon carbide with an inner diameter matching the sintered silicon carbide tube was used to establish a butt joint in addition to the cylindrical lap joint. A 2.45 GHz multi-mode microwave applicator was used, together with hybrid (microwave plus radiant) heating. The joined tubes held a vacuum of 12 x 10-3 torr, before and after thermal cycling to simulate service conditions. 10 refs., 5 figs