Property and morphology of organic modified CeO₂nanocrystals synthesized in supercritical water

Abstract

Poster Sessions the crystal diameter increases into c-axis direction. In contrast, when the electric power applied to the a-axis of crystal is stronger than the electric power applied to c-axis of crystal, the crystal diameter increases into the a-axis direction. As a conclusion, to get the round shape crystal, the electric power of the lamp applied into a-axis direction of crystal should be stronger than c-axis direction of crystal. The regulation of calcite mineralization by chiral biological molecules is one of the fundamental unresolved issues at the interface between biological, geological, and physical sciences. Here we address the role of chirality of L-aspartic acid (L-Asp), a model additive, in the regulation of the calcite growth. We apply phase-shift interferometry to non-intrusively monitor in situ the morphology of the surface and quantify the velocity of propagation of the steps, during crystallization. Similar to complex behavior observed before, L-Asp leads to several-fold increase in the step velocity, in all directions, at low supersaturations, and several-fold slow down at high supersaturations. L-Asp also introduces asymmetry in the velocity of steps of related by mirror symmetry, however, of less than 10 %. To explain the complex effects of L-Asp, and, likely, of other biological regulators of calcite crystallization, we show that prior to incorporation into steps, calcium and carbonate ions adsorb on the terraces and diffuse towards the steps. L-Asp accelerates the surface diffusion towards the steps, an achiral process, likely due to rearrangement by L-Asp of the structure of the water coating the calcite crystal surface. Importantly, L-Asp delays by about 20 times the incorporation of calcite ions into the steps, the only chiral process in the calcite crystallization mechanism, likely by blocking a significant fraction of the kinks. We show that the low asymmetry between the two chiral directions due to attenuation by the surface supply fields of the steps. The results and analyses presented here suggest that the chiral effects of bio-generated molecules on crystallization may be too weak to judge about biological or non-biological origin of minerals.Keywords: chirality, calcite, in-situ observation P16.10.34 Acta Cryst. (2008). A64, C590 Formation of barred olivine texture 4.6 billion years agoHitoshi Miura 1 , Yokoyama Etsuro 2 , Tsukamoto Katsuo 1 , Nagashima Ken 3 1 Tohoku University, Department of Earth Sciences, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578, Japan, 2 Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan, 3 Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan, E-mail miurah@ganko. tohoku.ac.jp Most of chondritic meteorites falling onto the Earth contain mmsized crystalline silicate spheres (chondrules), which are believed to have been formed from molten silicate droplets 4.6 billion years ago in our early solar system. Some of them have interesting textures with rim and bars. The rim has a thin shell-like morphology surrounding a chond...