Research on synthesis of kaolinite clay and humidity conditioning materials

Abstract

Development of measures to deal with the shortage of high-quality clays and advancement of new uses for traditional ceramics have been matters of great importance for ceramic industries. As a solution to these problems, this review focuses on the recent development of kaolinite clay synthesis and the use of kaolinite as a humidity conditioning material. (1) Kaolinite clay synthesis has been investigated. During investigations, a spherical-shaped kaolinite, which is crystallographically novel, was discovered. A new reaction vessel was also developed for efficient hydrothermal synthesis of clayey materials. The conditions for the synthesis of fine grain size, high plasticity, and reduced iron content kaolinite were optimized for a bench-scale process as one measure against clayey resource shortage. (2) Materials which autogenously regulate humidity without using electric energy have been studied, and model substances have been developed for porous materials with fine pore size of several nanometers based on the capillary condensation theory. Selectively leached kaolinite showed suitable properties as a humidity conditioning material and synthesis conditions were optimized for a material with uniform pore size and high pore volume. Natural nanoporous materials were also developed as low-cost humidity conditioning materials. It was concluded that elucidation of the relation between water and materials is important for synthesis and application of clays as an environmentally friendly material.