THERMAL-BEHAVIOR OF MECHANICALLY AMORPHIZED TALC

Changes in the structure of talc and processes in its dehydration and transformation into enstatite due to mechanical activation have been studied. The structure of talc became amorphous in the early stages of grinding. A decrease in the dehydration temperature and the appearance of an exothermic DTA peak took place following mechanical activation. The amount of heat evolved, estimated from the DTA peak area, increased with grinding time, but the temperature of the exothermic peak remained constant at 822-degrees-C. During mechanical activation, substantial dehydration took place, indicating a preferential destruction of the central layer of talc comprising Mg(OH)2, leaving highly mobile O2-. The formation of enstatite from mechanically amorphized talc is explained by postulating the recombination of O2- ions with the partially broken SiO4 tetrahedra as the rate-determining step.