Effect of Dry Grinding on the Structures and Physical Properties of Pyrophyllite and Talc by a Planetary Ball Mill

Abstract

The effect of dry grinding by a planetary ball mill on the structures and physical properties of pyrophyllite and talc minerals has been investigated by X-ray diffraction, TG-DTA, density and specific surface area measurements, particle size analysis and SEM observation.Size reduction of these two minerals was dominated in the early stages of grinding. The obtained fine particles of ground talc and pyrophyllite were subsequently found to aggregate with an increase in grinding time. X-ray diffraction patterns showed that the pyrophyllite and talc structures progressively deformed from a crystalline state to a disordered one with an increase in grinding time. Both ground pyrophyllite and talc specimens exhibit lower temperature dehydroxylation and new exothermic reactions. The ground pyrophyllite recrystallizes to mullite and y -alumina, while the ground talc changes to enstatite and amorphous silica when heated.