Engineering topics
Marks, L. D.
Publications and source records attributed to Marks, L. D..
ScO x rich surface terminations on lanthanide scandate nanoparticles
We report that the lanthanide scandate materials are widely used substrates for thin film growth and the potential applications of the LnScO 3 materials continue to grow with the recent ability to synthesize them as cuboidal faceted nanoparticles. A comprehensive understanding of the surface structure and chemistry of these oxides is essential for their informed application, either as single crystal or high surface area nanoparticle substrates. Here the {100} pseudocubic surfaces of LnScO 3 (Ln = La, Nd, Sm, Gd) nanoparticles were examined with aberration-corrected electron microscopy and higher-level density functional theory to reveal ScO x rich terminations across all investigated surfaces. Mixed terminations of single and double layer nature were observed, indicating the presence of multiple domains at the surface and introducing the possibility of synthetically controlling the surface reconstruction in the future.
Does Flexoelectricity Drive Triboelectricity?
The triboelectric effect, charge transfer during sliding, is well established but the thermodynamic driver is not well understood. We hypothesize here that flexoelectric potential differences induced by inhomogeneous strains at nanoscale asperities drive tribocharge separation. Modeling single asperity elastic contacts suggests that nanoscale flexoelectric potential differences of +-1–10V or larger arise during indentation and pull-off. Finally, this hypothesis agrees with several experimental observations, including bipolar charging during stick slip, inhomogeneous tribocharge patterns, charging between similar materials, and surface charge density measurements.