One of the main disadvantages of combustion synthesis of ceramic and composite materials is the relatively high levels of porosity, e.g., greater-than-or-equal-to 50 pct, present in the product. This article discusses a novel application of combustion synthesis for producing ceramic-metal composites with reduced levels of porosity by allowing an excess amount of liquid metal, generated by the exothermic reaction, to infiltrate the pores. This application of combustion synthesis of ceramic-metal composite materials is discussed with respect to a model reaction system that utilizes an inexpensive oxide, i.e., TiO2, reacted with carbon and an excess stoichiometric amount of aluminum. The aluminum is in the liquid state at the ignition temperature and is intentionally allowed to infiltrate the porous ceramic matrix, i.e., TiC-Al2O3, produced from the combustion synthesis reaction. This in situ process for producing ceramic-metal composites by the simultaneous liquid metal infiltration of the pores in a ceramic matrix using the combustion synthesis approach provides considerable advantages over conventional processes which involve two stages, i.e., sintering followed by liquid metal infiltration. However, there are also certain limitations with respect to total penetration of the liquid metal into the porous ceramic matrix and maintaining a stable propagation of the combustion reaction.
