Direct observation of inelastic deformation and mechanochemical activation of indented quartz single crystals

In a basic study of the mechanism of mechanochemical activation of fine powdery materials, a large single crystal of quartz was stressed by loading with a diamond indenter. The stressed crystal was subsequently immersed in 1 N KOH solution at 60 °C for various periods. The microstructures of the indented region before and after immersion were observed under a scanning electron microscope, in order to examine the direct correlation between the manner and the extent of deformation and the degree of activation. Inelastic deformation was recognized by indenting under a load as low as 1 kp. As the force is related to the area of indentation, the corresponding local pressure amounts to about 10 GPa. At higher loads, very fine fragments were produced and deformed highly inelastically. This part of the material dissolved preferentially because of the enhanced reactivity. It was thus verified qualitatively that the enduring effect of mechanochemical activation is a consequence of the inelastic deformation.