Material Synthesis in Supercritical Water

Specific Features of Reactions in Supercritical Water and Novel Processes for Organic and Inorganic Syntheses

Abstract

In this paper, we describe specific features of reactions in supercritical water. Around the critical point, phase behavior and reaction rate or kinetics varies significantly. In higher temperature region, contribution of noncatalytic reaction becomes significant even for hydrolysis, dehydration, or other heterolitic reactions. Complex contribution of these factors and the change of these effects sometimes lead to the appearance of extraordinary reactions. Previously reported researches on organic and inorganic synthesis reactions in supercritical water are summarized, referring to these key features, and controllability of reactions around the critical point is pointed out based on these results. Especially for the hydrothermal synthesis of metal oxide fine particles, the method of which we have proposed and developed, detailed explanation and discussion has been made. Key features of the method (control of phase, reactions and crystallization) are summarized and then applications of this method to the continuous production of magnetic materials (BaO₆ Fe₂O₃), Phosphor (YAG : Tb), and lithium ion battery materials (LiCoO₂) are explained, with discussing the possibility of creating new materials.