Study of plastic flow in CaCO3 and NaNO3 crystals under concentrated loads

Abstract

The mode of plastic deformation of CaCO3 and NaNO3 crystals under concentrated loads is investigated as a function of temperature. At room temperature CaCO3 undergoes plastic deformation by twinning on (011) planes at both, low and high loads whereas NaNO3 deforms by glide at low loads and at high loads both, the glide and twinning processes operate. At higher temperatures both, NaNO3 (T > 100 °C) and CaCO3 (T > 300 °C) exhibit plasticflow by glide at low loads; at high loads both, glide and twinning occur in CaCO3, whereas glide is the dominant mode of deformation in NaNO3 even at higher loads. The effect of adsorbate on microhardness of these materials is considered. The effect of adsorbates on microhardness value may be due to a weakening or strengthening of surface and near surface bonds.

Atomic layer wear of single-crystal calcite in aqueous solution using scanning force microscopy

“…A similar average stress exerted by a Vicker's indentor would produce an indent some tens of microns in diameter. 18 Nevertheless, we see no evidence for FIG. 5.…”

Tribological Enhancement of CaCO3Dissolution during Scanning Force Microscopy

“…This stress is sufficient to produce significant plastic deformation in tests with micrometer-sized probes. For instance, a Vicker's indentor supporting a load of 0.8 N will typically produce an indent in CaCO 3 ∼35 μm across the diagonal, corresponding to σ av ≈ 1.3 GPa. (In CaCO 3 , room temperature deformation is principally by twinning; high densities of dislocations are often found within the twinned material . )…”

Surface force microscope observations of corrosive tribological wear on single crystal NaNO3 exposed to moist air

“…The hydrophilic nature of the salt surface favors the formation of a water layer which responds rapidly to changes in ambient humidity. NaNO3 itself is quite soft (Moh hardness, 1.5-2 [1]; Vicker's hardness, 200 MPa at 50 g load [2]), and thus is vulnerable to tribological wear. In this study, surface force microscopy (SFM) is used to both apply the mechanical loading and to image the resulting topographical changes.…”