Mechanism for the Environmental Control of Drilling in MgO AND CaF2 Monocrystals

摘要

The effects of certain liquid environments on the penetration of a carbide space drill, and on the mobility of near-surface edge dislocations in freshly cleaved MgO and CaF2 monocrystals, have been determined at room temperature. It was found that drilling efficiency and near-surface dislocation mobility are directly related, and that 'softening' environments facilitate crack initiation in MgO. The n-alkanes have also been found to be extremely surface active with respect to MgO and CaF2 surfaces. It is proposed that adsorbed surface-active species control the drilling behavior of MgO and CaF2 -- and perhaps of other notch-sensitive nonmetallic solids (minerals) also -- as a consequence of their influence on the flow and flow-dependent fracture properties of the near-surface regions of these solids. Possible effects of adsorption-induced reductions in surface free energy are of minor importance. (Author)