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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 >Redox freezing temperature and Bartenev equation in a 25Na _2O-15B_2O_3-60SiO_2 glass doped with chromium and manganese
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Redox freezing temperature and Bartenev equation in a 25Na _2O-15B_2O_3-60SiO_2 glass doped with chromium and manganese

机译：铬和锰掺杂的25Na _2O-15B_2O_3-60SiO_2玻璃中的氧化还原冻结温度和Bartenev方程

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摘要

In a melt with the base mol% composition 25Na_2O-15B _2O_3-60SiO_2, doped with chromium and manganese, a redox reaction takes place during cooling the melt. This reaction was studied using high temperature UV-vis spectroscopy. Above 600 °C, the reaction is in equilibrium and shifted during cooling to the Cr~(3+) and Mn ~(3+) species. At temperatures between 500 and 600 °C, the kinetics of the redox reaction is decisive and the cooling rate plays an important part. At temperatures < 500 °C, the reaction is frozen in. The smaller the cooling rate, the smaller is the Cr~(6+) concentration and the lower is the fictive redox temperature. The kinetics of the reaction was described by a differential equation assuming Arrhenian behaviour. The equation was numerically solved and fictive temperatures were calculated. These temperatures depended on cooling rate similar to Bartenev equation. Activation energies calculated hereof were around 38 kJ·mol~(-1) larger than those inserted into the kinetic equation. The experimentally determined activation energy is 565 kJ·mol~(-1), a value much larger than the activation energies of diffusion of the polyvalent elements. The rate determining step in the case of the Cr~(3+)/Cr~(6+)/Mn~(2+)/Mn~(3+) system is the electron transfer reaction, because a notable structural rearrangement is necessary during the course of the electron transfer reaction (Cr~(3+) and Cr~(6+) occur in octahedral and tetrahedral coordination, respectively). The latter leads to a large inner reorganisation energy and to an activation energy similar to that of the viscous flow. In the case of the redox reaction between copper and arsenic, the activation energy is much smaller (210 kJ·mol~(-1)), because here the coordination numbers do not change during the course of the redox reaction.
机译：在具有基础摩尔％组成的25Na_2O-15B _2O_3-60SiO_2（掺杂有铬和锰）的熔体中，在冷却熔体的过程中发生了氧化还原反应。使用高温UV-可见光谱研究了该反应。高于600°C，反应达到平衡并在冷却过程中转变为Cr〜（3+）和Mn〜（3+）物种。在500至600°C的温度下，氧化还原反应的动力学起决定性作用，冷却速率起着重要的作用。在<500°C的温度下，反应被冻结。冷却速率越小，Cr〜（6+）浓度越小，虚拟氧化还原温度越低。该反应的动力学通过微分方程描述，假设阿累尼安行为。对该方程进行了数值求解，并计算了虚拟温度。这些温度取决于类似于Bartenev方程的冷却速率。由此计算的活化能比插入动力学方程中的活化能大约38 kJ·mol〜（-1）。实验确定的活化能为565 kJ·mol〜（-1），该值比多价元素扩散的活化能大得多。在Cr〜（3 +）/ Cr〜（6 +）/ Mn〜（2 +）/ Mn〜（3+）体系中，速率决定步骤是电子转移反应，因为必须进行显着的结构重排在电子转移反应过程中（Cr〜（3+）和Cr〜（6+）分别以八面体和四面体配位形式发生）。后者导致较大的内部重组能和类似于粘性流的活化能。在铜与砷之间的氧化还原反应的情况下，活化能要小得多（210 kJ·mol〜（-1）），因为此处的配位数在氧化还原反应过程中不会改变。

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