Contribution of Slip and Cleavage in Friction and Wear at (1 0 -1 4) Surface of Magnesite (MgCO3) Crystal

Abstract

Frictional force was measured using Bowden-Leben apparatus with a sapphire stylus at directional (1 0 -1 4) surface of magnesite crystal. Deformation patterns formed during the scratch in ± [4 2 -1] directions were observed with optical microscopy. With the normal load up to 460 mN, no trace of slip or cleavage was observed and the friction coefficient remained at 0.0085. Frictional asymmetry due to the tilt of carbonate ions was not recognized in this range. At higher normal loads, new components were added to the frictional force, with the appearance of traces of slip, and then, cleavage on {1 0 -1 4} faces. In contrast with the case of calcite, traces of the slip remained within the width of the stylus. Traces of the cleavage, on the other hand, reached far outside the wear track, and asymmetry was recognized in the pattern formation. In indentation experiments, the cleavage occurred in four directions, but slip on (0 0 0 1) was not recognized. In contrast with isostructural but softer calcite crystal, the difficulty in the (0 0 0 1) slip with magnesite keep the friction coefficient low toward higher normal loads.

Keywords

• friction coefficient
• mgco3
• single crystal
• cleavage
• frictional asymmetry