The fate of silicon during glass corrosion under alkaline conditions: A mechanistic and kinetic study with the International Simple Glass
The fate of silicon during glass corrosion under alkaline conditions: A mechanistic and kinetic study with the International Simple Glass
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DOI：
10.1016/j.gca.2014.12.009
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发表时间：
2015-02-15
影响因子：
5
通讯作者：
Ryan, Joseph V.
中科院分区：
文献类型：
--
作者：
Gin, Stephane;Jollivet, Patrick;Ryan, Joseph V.
International Simple Glass是一种由国际核玻璃界选择的六氧化物硼硅酸盐玻璃，用于提高对玻璃腐蚀机制和动力学的理解，在90 ℃下，在最初相对于非晶（SiO2）-Si-29饱和的溶液中进行了改变。在实验开始时将pH（90 ℃）固定在9，并在209天后通过加入KOH升高至11.5。同位素敏感的分析技术被用来分析溶液和改变的玻璃样品，帮助理解的驱动力和速率限制过程控制长期的玻璃蚀变。在pH 9时，腐蚀速率持续下降，玻璃缓慢转变为均匀、同质的无定形蚀变层。负责这种转变的机制是水渗透通过不断增长的蚀变层和离子交换。我们表明，这种无定形的蚀变层是不是从硅酸盐网络的水解产生的沉淀物，它主要是继承从玻璃结构中最弱的键合阳离子（Na，Ca和B）已被释放。在pH值为11.5时，蚀变过程非常不同：玻璃网络形成剂（Si、Al、Zr）的高溶解度引发玻璃的快速和完全溶解（溶解变得一致）以及非晶相和结晶相的沉淀。与在pH 9下玻璃腐蚀速率降低3个数量级可能是由于在反应前沿的水动力学/反应性上的蚀变层的反作用不同，在pH 11.5下的速率保持在接近于正向速率的值，这是由于由OH-促进的硅酸盐网络的水解以及CSH和沸石的沉淀。这项研究提供了一个统一的玻璃溶解模型的关键信息。(C)2014爱思唯尔有限公司版权所有。
International Simple Glass - a six oxide borosilicate glass selected by the international nuclear glass community to improve the understanding of glass corrosion mechanisms and kinetics - was altered at 90 degrees C in a solution initially saturated with respect to amorphous (SiO2)-Si-29. The pH(90 degrees C), was fixed at 9 at the start of the experiment and raised to 11.5 after 209 d by the addition of KOH. Isotope sensitive analytical techniques were used to analyze the solution and altered glass samples, helping to understand the driving forces and rate limiting processes controlling long-term glass alteration. At pH 9, the corrosion rate continuously drops and the glass slowly transforms into a uniform, homogeneous amorphous alteration layer. The mechanisms responsible for this transformation are water penetration through the growing alteration layer and ion exchange. We demonstrate that this amorphous alteration layer is not a precipitate resulting from the hydrolysis of the silicate network; it is mostly inherited from the glass structure from which the most weakly bonded cations (Na, Ca and B) have been released. At pH 11.5, the alteration process is very different: the high solubility of glass network formers (Si, Al, Zr) triggers the rapid and complete dissolution of the glass (dissolution becomes congruent) and precipitation of amorphous and crystalline phases. Unlike at pH 9 where glass corrosion rate decreased by 3 orders of magnitude likely due to the retroaction of the alteration layer on water dynamics/reactivity at the reaction front, the rate at pH 11.5 is maintained at a value close to the forward rate due to both the hydrolysis of the silicate network promoted by OH- and the precipitation of CSH and zeolites. This study provides key information for a unified model for glass dissolution. (C) 2014 Elsevier Ltd. All rights reserved.