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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Crystallization of amorphous silicates far from equilibrium part II: Experimental insight into the key role of decoupled cation mobilities
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Crystallization of amorphous silicates far from equilibrium part II: Experimental insight into the key role of decoupled cation mobilities

机译:非晶态硅酸盐的结晶远未达到平衡第二部分:对解耦阳离子迁移率的关键作用的实验见解

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摘要

The crystallization of amorphous and porous Ca-Mg-silicates prepared by a sol-gel method is studied in the glass transition range during isothermal and continuous heating experiments. A starting material of diopside (CaMgSi _2O_6) composition was primarily studied because it is a reference system to study crystal nucleation and growth. The annealed products were characterized by X-ray diffraction and transmission electron microscopy. In the glass transition range, the crystallization is not congruent. It follows a systematic sequence in which the most Ca-rich silicates present in the phase diagram crystallize first. This trend does not obey equilibrium thermodynamics predictions. Instead, this sequence is the result of the decoupled mobilities of network-modifying and network-forming cations. The high surface/volume ratio of gels likely exacerbates this effect compared to compositionally comparable glasses. Altogether, the study shows that local dynamics controls kinetic phase transitions in the glass transition range.
机译:在等温和连续加热实验的玻璃化转变范围内,研究了通过溶胶-凝胶法制备的非晶态和多孔Ca-Mg硅酸盐的结晶。主要研究了透辉石(CaMgSi _2O_6)组成的起始材料,因为它是研究晶体成核和生长的参考系统。通过X射线衍射和透射电子显微镜对退火产物进行表征。在玻璃化转变范围内,结晶不完全。遵循系统的顺序,其中相图中存在的最富钙的硅酸盐首先结晶。这种趋势不符合平衡热力学的预测。取而代之的是,该顺序是网络修改阳离子和网络形成阳离子的迁移率相互独立的结果。与可比的玻璃相比,凝胶的高表面积/体积比可能会加剧这种效应。总之,研究表明,局部动力学控制着玻璃相变范围内的动力学相变。

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