Accelerated microwave-assisted hydrothermal/solvothermal processing: Fundamentals, morphologies, and applications

This article is designed to serve as a roadmap for understanding the fundamentals, the key advantages and the potential applications of microwave-assisted hydrothermal/solvothermal (MAH/S) processing. MAH/S synthesis is a versatile chemical method for preparing a diversity of materials such as metals, semiconductors, electroceramics, graphene and their composites as bulk powders, thin films, or single crystals. The key to improve performance of these materials is achieving controlled morphologies (0 to 3D dimensionality) that favor desirable physical-chemical phenomena at the surface, and in the bulk of these advanced materials. The main features related to the improvement of the thermal and non-thermal effects associated with the use of microwave power concurrently with hydrothermal or solvothermal methods are discussed. Furthermore, the main crystal growth mechanisms (Ostwald ripening and oriented attachment) of these solids in solution under MAH/S treatment are described. Products synthesized by the MAH/S, particularly of interest in the development of gas sensors, batteries, fuel cells, solar cells and photocatalysts are emphasized. We conclude by envisaging new future directions for the use of this rapid and versatile processing approach.