Frictional Asymmetry and Wear Pattern Formation by Slip and Cleavage Detected at Directional <I>r</I>{1 0 -1 4} Face of Calcite (CaCO₃)

Abstract

Frictional force was measured on directional calcite (1 0-1 4) surface, where triangular carbonate ions are all tilted to [4 2-1] direction. With the normal load < 49 mN, observed frictional asymmetry, +[4 2-1] >-[4 2-1], was the same as that measured in nm-scale. In the higher normal load range, a new component was added to the friction in-[4 2-1] direction, and the asymmetry was reversed. Only in the direction of stronger friction, characteristic triangular deformation patterns were formed. Microscopic observation after indentation experiments revealed that the patterns were formed by slip on c (0 0 0 1) faces on one side of the stylus, followed by cleavage on r{1 0-1 4} faces. A mechanical model was proposed to explain why the deformation occurs only in one quadrant of the surface. The result of scratch perpendicularly in [0 1 0] direction, also supports the mechanism of deformation. The results show when and how the contribution of plastic deformation is added to intrinsic surface friction and affects the frictional asymmetry. The frictional force in the-[4 2-1] scratch increased linearly with the total lengths of the traces of c-slip.

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

“…Similar asymmetry was observed in friction measurements in millimeter-scale using a Bowden-Leben apparatus with a sapphire stylus of 60° cone angle, applying the normal load smaller than 49 mN 20) . With heavier normal loads, however, reversed frictional asymmetry, -[4 2 -1] > + [4 2 -1], was observed.…”

“…Clearly much longer cleavage cracks were observed in Fig. 3B In the case of calcite, the cleavage lines were observed only in areas where the c-slip split the surface into thin strips beforehand 20) .The r-cleavage with magnesite, on the other hand, occurs independently. But why do the cleavage lines run in the same direction in the opposite scans?…”

“…Among them, the slip on c(0 0 0 1) face was the one which gave lots of traces in [0 1 0] direction in the -[4 2 -1] scratch at the (1 0 -1 4) face of calcite. The traces were formed under the normal load as small as 49 mN 20) , and extended well out of the wear track. No trace, however, was formed in + [4 2 -1] scratch.…”

Micro-Scale Friction and Wear at Orthorhombic BaSO₄(0&thinsp;0&thinsp;1) Surface

“…To understand friction in relation to the atomic structures of the materials, it is important to know at which stress levels the contribution from surface properties are overwhelmed by that of bulk properties. We have detected transition between the two regimes in the case of calcite (CaCO 3 ) [6]. At the cleaved (1 0 -1 4) surface of the crystal, frictional asymmetry has been observed with FFM in ±[4 2 -1] directions due to triangular CO 3 2− ions tilted to the same direction at the surface [7].…”

“…The optical microscope image in Fig. 3(a) It should be noted that two sides of each triangle are slightly curved, which was not observed in the case of calcite [6]. The AFM images in Fig.…”