Dissolution of comminuted magnesium oxide as affected by the density of dislocations introduced by various comminution methods

Abstract

Commercial refractory grade magnesium oxide (MgO) was comminuted with a steel ball mill, ouck mill, roll mill and pulverizer. The dissolution of the comminuted powders in hydrochloric acid solution was measured and correlated with the dislocation densities in the powder as measured by X-ray powder diffractometry. It was found that the rates of dissolution of the powders were directly related to the dislocation densities introduced by the comminution. The ball-milled powder exhibited the highest dissolution rates and largest dislocation densities. The damage introduced by comminution could be removed by heat treatment at 1400° C. Dislocation densities in comminuted MgO were also found to be much larger than those in similarly comminuted quartz, as expected based on the differences in the plastic deformation behavior of these two materials.