Published: 8 October 2020, 13:40
Cleaved dolomite (CaMg(CO3)2) crystals were immersed in supersaturated, saturated, and undersaturated solutions with respect to zabuyelite (Li2CO3), and the growth process was characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In all cases, overgrowths formed by 2D-nucleation could be clearly distinguished in the lateral force images recorded by AFM. With highly supersaturated solutions, AFM imaging was hindered by the formation of 3D crystal aggregates. When saturated solutions were used, the overgrowths reproduce the topography of the substrates, indicating that the lattice of the overgrown phase undergoes a compressive strain.
Furthermore, we performed a nanotribological characterization by sliding a nanotip over both the 2D-overgrowths and dolomite substrates. Thus, friction coefficients, µ, could be easily quantified. As a result, a µ = 0.08 on the 2D-overgrowths was measured, which is one order of magnitude lower than the value of µ = 0.89 on the dolomite substrate. This friction reduction in the sliding of a nanotip on the overgrowth as compared to the friction observed on the dolomite substrate, together with the fact that atomic-scale stick-slip is observed on dolomite but not on the 2D overgrowths, point towards an anomalously weak interaction of Li2CO3 overgrowths with the AFM probe.