Mechanical work and conversion degree in mechanically induced processes

Several mechanochemical reactions, involving the formation of amorphous phases and extended solid solutions as well as the spontaneous spreading of self-propagating reactions, were investigated under controlled milling conditions. The work was aimed to identify possible connections among milling parameters and conversion mechanisms. Mechanochemical transformations are shown to proceed according to two different kinetics, characterized by continuously decelerating and sigmoidal conversion trends. Experimental findings are rationalized on the basis of invariant quantities which were found to characterize the observed reactions. Such quantities also provide a means for the absolute comparison of the reactions. It is demonstrated that a major role should be attributed to the mechanical work done on the powders during the course of the mechanical treatment. The degree of conversion is found to depend only on the energy dose transferred to reactants, independently of the milling intensity. (C) 2004 Elsevier B.V. All rights reserved.