Gas-phase combustion synthesis of materials

To emphasize the scientific and technological challenges still remaining in combustion synthesis, this review highlights three classes of combustion processes for nonoxide refractory solids, especially ceramics, that involve the gas phase during synthesis. In one synthesis process, where the reactants are all gases, simultaneous control of powder particle size, size distribution, and microstructure is still an elusive goal but one that may be on the verge of achievement. A second class of process, gas-phase-assisted solid-solid combustion synthesis, reveals the often hidden role that gases play facilitating and catalyzing the reactions that yield refractories and ceramics, and raises the prospect of tailoring reaction chemistry through judicious selection of additives. A third class of process, the much studied synthesis reaction between a gas and a condensed phase, demonstrates the need for an understanding of both equilibrium and kinetic processes to achieve microstructural control of solid product phases.