Aspects of the thermal decomposition of ε-zinc hydroxide: a kinetic compensation effect

Abstract

Differential scanning calorimetry and quantitative thermal analysis of the kinetics of thermal decomposition of zinc and related hydroxides, undertaken in order to investigate the relations between the decomposition kinetics and the catalytic properties of the resulting oxides, has revealed the existence of a remarkable compensation effect for ε-Zn(OH)₂. Optical microscopy has been used as a complementary technique to study the formation and growth of product nuclei during the thermal decompositions and to test the reliability of the thermal methods. The microscopic study, by the etching technique, of the points of emergence of the dislocations, reveals the existence of two distinct types of line defects, one of which is more conducive for the reaction. The results are interpreted in terms of a Sosnovsky-type mechanism, and the elastic strain energy of the dislocations is considered to be the main contributor to the lowering of the activation energy of the nucleation process.