Our atomic-scale studies of special boundaries in various natural and synthetic minerals have shown that they are in fact chemically triggered and that they nucleate under specific thermodynamic conditions. Growth twins are only one type of possible special boundaries. Depending on crystallographic operation between the crystal domains, they are defined as twin, inversion or antiphase boundaries. They nucleate in the initial stages of crystal growth as a result of structurally confined 2D chemical reaction between the dopant and the major phase. In the nucleation stage, dopant atoms are chemisorbed (react) onto specific crystallographic planes of the host in a highly ordered manner, controlled by the surface structure. Confirmation of this hypothesis was not possible until the development of modern electron microscopy that enabled a direct insight into the structure of twin boundaries at atomic scale. Despite a solid theoretical background it is surprising how little was done proving these concepts experimentally.
B.04 Guest lecture
COBISS.SI-ID: 28819751Study of atomic structure around inversion domain boundaries in nanometer sized bipods zinc oxide was presented Using energy dispersive X-ray spectroscopy the presence of Si was found in some places, still in smaller quantities as expected. From HAADF images we concluded that Si is most probably in tetragonal coordination. We present a tentative model of the boundary. For final solution more experiments should be done.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 5809434We report on the synthesis of polysynthetic twins in Cu3Pt nanoparticles used as a catalyst material in low-temperature fuel-cells. Studying local arangemet around twin boundaries it was found that within few atomic layers the material become inhomogeneus and depleted in Platinum. We introduced the modified method for the determination of chemical compostion of individual atomic columns.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 5803034