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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Tracing the Reactive Melting of Glass-Forming Silicate Batches by In Situ ~(23)Na NMR
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Tracing the Reactive Melting of Glass-Forming Silicate Batches by In Situ ~(23)Na NMR

机译：原位〜（23）Na NMR追踪玻璃化硅酸盐批料的反应性熔融

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摘要

The kinetics of the reaction of batches of powdered quartz and sodium carbonate was studied by in situ ~(23)Na nuclear magnetic resonance (NMR) spectroscopy using a laser-heated probe.We show for the first time that the technique allows one to study solid-state reactions at high temperatures with good time resolution and without the risk of quenching artifacts.The reaction is controlled by solid-state Na~+ diffusion across the grain interface.Independent of the batch composition,the first reaction product is crystalline sodium metasilicate,Na_2SiO_3,even if the temperature is high enough for much of the composition space between silica and metasilicate to be above the equilibrium liquidus.Fast Na~+ diffusion allows the reaction front to cross the grain interface and form the solid product before liquid intermediate equilibrium products can be formed.This purely solid-state reaction slows down as the thickness of the interface increases;the reaction is more deceleratory than published models suggest.If excess quartz is present,it reacts in a second step involving a liquid film wetting the excess grains.Once this reaction has started,it pulls the reaction into the thermodynamic regime,which leads to an increase even in the rate of the first step leading to intermediate solid metasilicate.
机译：用激光加热探针通过原位〜（23）Na核磁共振波谱研究了一批石英粉和碳酸钠的反应动力学，我们首次证明了该技术可以研究在高温下进行固态反应，具有良好的时间分辨率，并且没有淬灭假象的风险。反应受固态Na〜+在整个晶粒界面上的扩散控制。与批料组成无关，第一反应产物是结晶硅酸钠Na_2SiO_3，即使温度足够高，即使二氧化硅和偏硅酸盐之间的大部分组成空间都高于平衡液相线。快速的Na〜+扩散也可使反应前沿在液体中间平衡之前穿过晶粒界面并形成固体产物可以形成产物。随着界面厚度的增加，这种纯固态反应会减慢;该反应比已发表的论文更具减速性如果存在多余的石英，则它会在第二步进行反应，这涉及液膜润湿多余的晶粒。一旦此反应开始，它将把反应拉入热力学状态，这甚至会提高反应速率。第一步产生中间体固体偏硅酸盐。

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