采用表面失重法分析40ZnO-10MgO-50P2O5玻璃在酸性溶液中的溶解过程. 实验结果表明: 含二价金属阳离子的磷酸盐玻璃在水中溶解速度缓慢, 但在酸性溶液中, 因R 2+和H+离子交换加速, 破坏了结构的稳定性, 磷氧基团很容易发生水解, 在pH<3时, 玻璃的溶解速率会急剧增大. 溶解速率随温度升高呈现指数增加的趋势, 溶解活化能随pH值的升高而降低; 在高浓度盐酸溶液中, 溶解速率随浓度变化出现极值, 这一切均应归于H+和H2O活度的双重作用; 通过对失重曲线变化的研究发现: 玻璃的溶解过程分为两个阶段, 第一阶段失重量与时间平方根成正比, 第二阶段失重量与时间成正比, 说明玻璃表面的水化层经历了形成、发展和稳定的过程.
The dissolution process of 40ZnO-10MgO-50P2O5 glass in acid medium was studied by weight loss analysis. The result shows that the water dissolution rate of phosphate glasses doped with bivalent ions is low. However, situation changes greatly as the pH value of the solution reduces because of the ion exchange reaction between R 2+ in glass and H+ in acid. The stability of glass network is thus destroyed and followed by hydrolysis reaction of phosphate structural group. The dissolution rate increases exponentially with the increase of temperature and the reaction activation energy decreases with the increase of pH value. The dissolution rate reaches the maximun in concentrated HCl due to the contribution of both H+ and H2O. The mechanism of the dissolution process is proposed into two steps: first, the weight loss is proportional to the square root of the time, and the next, it is proportional to time, which indicates the formation and development of hydrate layer on the glass surface.
参考文献
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