Chapter 7.2 Thermally Modified Clay Minerals

Abstract

Publisher Summary This chapter describes thermally modified clay minerals. The structure and composition of clay minerals are modified by heating. The concomitant changes in properties can be exploited for practical purposes. The actual temperatures at which changes occur vary greatly from one clay mineral group to another, and even for different specimens within a given group. These temperatures also depend on the particle size and on the heating regime. Four principal temperature ranges in which significant changes occur in the structures of clay minerals may be distinguished. In view of the great variety of starting materials and the many variables involved in the heating regime, a range of options is available for the thermal modification of clays. The ubiquitous impurities in natural clays may also play a part. The preactivation temperatures required to develop desirable properties, or prevent undesirable properties from developing, vary with different clay minerals. Some minerals are preferably used in the dehydrated, others in the dehydroxylated form.