GRAIN-GROWTH IN SYNTHETIC AND NATURAL DOLOMAS

Grain growth of CaO and MgO phases during sintering of synthetic, natu ral and CaO-added natural dolomas was studied in the temperature range 1300-1700 degrees C. The time exponents of the grain growth laws depe nd on the starting materials, processing parameters and sintering temp erature, varying from 1/2 to 1/3 for the synthetic doloma, and from 1/ 6 to 1/3 for the natural doloma and CaO-added natural dolomas. Kuczyns ki's statistical model for the intermediate stage of solid state sinte ring was applied to the dual-phase interpenetrating microstructures of doloma, assuming that the volume fraction of the minor phase substitu tes for the open porosity in the monophasic systems. The results showe d that the model is applicable as a whole, provided that the relative widths of the CaO and MgO grain size distributions are considered to b e proportional instead of equal. (C) 1998 Elsevier Science Ltd and Tec hna S.r.l.