Mechanochemical Behavior of Surface Radicals in Ground Quartz

This work focuses on the chemical reactivity of quartz powders undergoing mechanical activation. The powders were submitted to mechanical loads in the presence of a free radical scavenger dissolved in ethanol. A gradual consumption of the scavenger was observed, ascribable to the chemical reactivity of the active sites generated at the surface of quartz powders by fracture and attrition. The apparent surface density of the active sites was indirectly measured by relating the observed reaction kinetics to the specific surface area of quartz powders. It is shown that not only the apparent surface density of the active sites generated by fracture is higher than the one of the active sites formed by attrition but also that it is even higher than the maximum possible surface density of dangling bonds. This points out the high reactivity of the surface sites generated by fracture and identifies the nature of mechanochemical effects in the present case.