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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Thermal dehydration of monohydrocalcite: Overall kinetics and physico-geometrical mechanisms
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Thermal dehydration of monohydrocalcite: Overall kinetics and physico-geometrical mechanisms

机译：单氢方解石的热脱水：整体动力学和物理几何机理

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摘要

Monohydrocalcite (CaCO_3?H_2O: MHC) is similar in composition and synthetic conditions to hydrated amorphous calcium carbonate (ACC), which is focused recently as a key intermediate compound of biomineralization and biomimetic mineralization of calcium carbonate polymorphs. Detailed comparisons of the physicochemical property and reactivity of those hydrated calcium carbonates are required for obtaining fundamental information on the relevancy of those compounds in the mineralization processes. In the present study, kinetics of the thermal dehydration of spherical particles of crystalline MHC was investigated in view of physico-geometrical mechanism. The reaction process was traced systematically by means of thermogravimetry under three different modes of temperature program. A distinguished induction period for the thermal dehydration and cracking of the surface product layer on the way of the established reaction were identified as the characteristic events of the reaction. By interpreting the kinetic results in association with the morphological changes of the reactant particles during the course of reaction, it was revealed that nucleation and crystal growth of calcite regulate the overall kinetics of the thermal dehydration of MHC. In comparison with the thermal dehydration of hydrated ACC, which produces anhydrous ACC as the solid product, the kinetic characteristics of the thermal dehydration of MHC were discussed from the viewpoint of physico-geometry of the component processes.
机译：单氢方解石（CaCO_3？H_2O：MHC）的组成和合成条件与水合无定形碳酸钙（ACC）相似，水合无定形碳酸钙最近被作为碳酸钙多晶型物的生物矿化和仿生矿化的关键中间化合物。要获得有关这些化合物在矿化过程中相关性的基本信息，需要对这些水合碳酸钙的理化性质和反应性进行详细比较。在本研究中，从物理几何机理的角度研究了结晶MHC球形颗粒热脱水的动力学。在三种不同的温度程序模式下，通过热重分析系统地追踪了反应过程。在建立的反应途中，表面产物层的热脱水和破裂的显着诱导期被确定为反应的特征事件。通过解释与反应过程中反应物颗粒形态变化相关的动力学结果，发现方解石的成核和晶体生长调节了MHC热脱水的整体动力学。与产生固体无水ACC的水合ACC的热脱水相比，从组成过程的物理几何学角度讨论了MHC热脱水的动力学特性。

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