Chapter 18 - Hydrothermal synthesis of ceramic materials

Abstract

This chapter introduces the field of hydrothermal materials synthesis and shows how understanding solution thermodynamics of the aqueous medium can be used for engineering hydrothermal crystallization processes. Hydrothermal synthesis is a material synthesis technology. It utilizes single or heterogeneous phase reactions in aqueous media at elevated temperature and pressure to crystallize ceramic materials directly from the solution. Syntheses are usually conducted at autogeneous pressure. Hydrothermal synthesis is different from solvothermal synthesis methods and soft solution processing. Hydrothermal synthesis offers many advantages over conventional and non-conventional ceramic synthetic methods. All forms of ceramics can be prepared with hydrothermal synthesis, with the costs for instrumentation, energy and precursors being far less, and more environmentally benign than many other synthesis methods. Another important technological advantage of the hydrothermal technique is its capability for a continuous materials production. In order for hydrothermal synthesis to become a mainstream technology, engineering approaches must be available to facilitate rapid-technology development. By designing a hydrothermal process to be thermodynamically favored to form desired products, kinetics limitations of the process can be subsequently resolved. Thermodynamic modeling can be used to design a process to be thermodynamically favored using fundamental principles instead of the Edisonian methods. Such models can perform many functions in the design of hydrothermal experiments.