MECHANICALLY ACTIVATED ROOM-TEMPERATURE REDUCTION OF SULFIDES

Solid state room temperature reduction and exchange reactions of metal (M) sulphides are described. Reactions are driven by ball milling powder mixtures of the sulphide and the reductant (R) or exchange compound (CaO). Reduction reactions show a complete reduction of the metal sulphide with formation of M-R(sulphide) nanocomposites. Exchange reactions with CaO show the formation of M(oxide)-CaS nanocomposites. Reactions having positive enthalpy or even positive free-energy changes in a wide temperature range are shown to occur. The effect of milling iron sulphide alone is also reported. Milling was performed for 24 h to assess the feasibility of the various reactions involved. X-ray diffraction and Mossbauer spectroscopy for iron-containing systems were used to characterize the powders before and after processing.