PNNL

Abstract

Recently a new method of ceramic brazing has been developed. Based on a two-phase liquid composed of silver and copper oxide, brazing is conducted directly in air without the need of an inert cover gas or the use of surface reactive fluxes. Because the braze displays excellent wetting characteristics on a number ceramic surfaces, including alumina, various perovskites, zirconia, and ceria, we were interested in investigating whether a metal-reinforced ceramic matrix composite (CMC) could be developed with this material. In the present study, two sets of homogeneously mixed silver/copper oxide/ceria powders were synthesized using a combustion synthesis technique. The powders were compacted and heat treated in air above the liquidus temperature for the chosen Ag-CuO composition. Metallographic analysis indicates that the resulting composite microstructures are extremely uniform with respect to both the size of the metallic reinforcement as well as its spatial distribution within the ceramic matrix. The size, morphology, and spacing of the metal particulate in the densified composite appears to be dependent on the original size and the structure of the starting combustion synthesized powders.