Mechanically Induced Reactivity of Solids

Abstract

The action of mechanical energy on solids effects changes to their structure. The resulting structural defects lead to a storage of energy in the solid, which may raise its chemical reactivity. Investigations on the mechanically induced reactivity of solids have been carried out with the specific aim of influencing reaction processes in order to obtain high yields, high reaction velocities or selective reactions. On the basis of detailed structural investigations on mechanically treated quartz and hydrargillite, the interaction of the stressed solid with the surroundings has been explored (titanite formation, zeolite formation, polymorphous transformation, gas adsorption, Na+-elimination and hydration of amorphous Al2O3). The investigations reveal that the size reduction which occurs during mechanical activation is not the decisive reason for reactivity enhancements, but that these are caused primarily by structural changes. Apart from the structural properties of solids, however, their chemical properties as well as those of the surroundings have an influence on their reactivity.