THE APPLICATIONS OF MICROWAVES IN CHEMICAL SYNTHESES

The application of microwave dielectric heating techniques for chemical syntheses has attracted considerable interest in recent years. A fundamental understanding of the mechanisms responsible for effective coupling of microwave radiation to liquid and solid chemicals and the establishment of techniques for containing the chemicals safely within a microwave cavity have contributed to the rapid progress in this area. A wide range organic and inorganic reactions have been accelerated using microwave techniques. The rapid syntheses of these compounds can be attributed primarily to superheating effects which result from the effective coupling of microwaves to the polar organic solvent in the containment vessel. Similar methods have been used for accelerating intercalation reactions resulting in the incorporation of organic molecules between the layers of an inorganic host material. In the solid state mixed metal oxides may be synthesized at an accelerated rate if one of the components has a high loss tangent. The ceramic high temperature superconducting materials have been synthesized in this manner and have utilized the high loss tangent of copper oxide. Metal chlorides, chalcogenides and oxides have also been synthesized directly from the elements using microwave dielectric heating effects resulting from the efficient coupling of microwaves to the particles of metal powder.