Microstructural Development in Metal-Ceramic Systems Containing a Liquid Phase
A wide range of metal-ceramic composites are processed with the aid of liquid metal phases. Examples include cast metal-matrix composites, cemented carbides, glass-enameled metals, and thick film conductors. The central phenomenon in processing these systems is wetting of the solid phase by the liquid. Unfortunately, many potentially useful metal-ceramic combinations (especially oxide ceramics) exhibit insufficient wetting for interface and/or microstructural development.
Most of the current strategies to promote wetting (e.g. pressure infiltration) have evolved by trial and error and are best described as "brute force" methods. MSE researchers have recently demonstrated that spontaneous (pressureless) infiltration of porous ceramics can be achieved by controlled oxygen doping in molten metals.
The notion that an interfacial chemical reaction can drive spreading of a partially wetting liquid on a solid has been discussed for 20 years. In no case have other systematic studies of these effects or correlations with interface microstructural observations been made. A better understanding of the microstructural origins and implications of dynamic wetting phenomena would open new avenues to improve composite processing, as well as enable the development of new composites.