ACCELERATING THE KINETICS OF LOW-TEMPERATURE INORGANIC SYNTHESES

This paper reviews several different methods used by the author over the past 40 years and those very recently developed in his laboratory for accelerating reactions in oxide materials at temperatures in the range 0-500-degrees-C. The latter include: (1) acoustic wave stimulation (sonochemical), (2) using ionizing and nonionizing radiation, and (3) the hydrothermal process with microwave fields. The results show that several of these methods can accelerate reactions of the most common oxides, especially in aqueous environments, by one to two orders of magnitude, and are therefore technologically significant. The basic science behind the processes is still primitive. The classical methods include: (4) utilizing precursors made via the solution sol-gel method and, recently, epitaxy via nanocomposite gel routes, (5) using low melting ''fluxes,'' (6) hydrothermal processes, hydrothermal process with superimposed electric fields, and hydrothermal process with mechanical forces, and (7) mechanochemical effects including very high uniaxial pressure and shear. (C) 1994 Academic Press, Inc.