Mechanisms, feedbacks and resulting non-linearity during silicate glass alteration in a hyperalkaline carbonate solution were studied through hyperspectral Raman imaging of heated fluid-cells. Our experimental setup enabled in operando visualization and rate measurements of glass dissolution and secondary phase precipitation, complemented by spectral characterization of the phases involved and semi-quantitative monitoring of the ionic strength of the solution close to the glass interface. After initial congruent dissolution of the Ba-bearing soda-lime boroaluminosilicate glass, the formation of a crystalline, saponite-based surface alteration layer (SAL), as well as subsequent zeolite precipitation, witherite coating, and carbonate precipitation within pore spaces of the saponite layer were observed. Two in operando experiments were conducted at ∼ 90 °C for 180 and 260 h that otherwise solely differed in the solution volume (SV) while keeping the surface area constant. The high SV experiment exhibited a transient upward excursion of initial dissolution rates, followed by continuously rapid glass dissolution along with slow SAL growth and sustained oscillations in ionic strength. Contrastingly, in the low SV experiment, glass dissolution monotonically decreased after the onset of rapid SAL growth and no sustained oscillations were observed. We find that growth conditions and resulting properties of the SAL exert dominant, non-linear effects on the evolution of glass dissolution rates. In turn, SAL formation depends on nucleation/growth kinetics and the accumulation of glass-derived solutes at the reaction front. Both, dissolution and precipitation, feedback with solution chemistry and transport processes, together controlling the evolution of the corrosion process. Additionally, fracturing, delamination, and the evolution of surface morphology may affect glass dissolution rates and transport pathways. Such interpretations of decelerating reaction rates in response to the growth of a protective layer are consistent in micro-scale experiments and in outcrop- to global-scale observations, as is the accelerating effect of surface area creation by physical disruption and morphology. Thus, these µm-scale mechanistic insights could help elucidating local to global environmental feedbacks (e.g., erosion or weathering patterns) as well as process dynamics in engineered environments (e.g., nuclear waste disposal) and may assist the improvement predictive models.

通过加热流体细胞的高光谱拉曼成像研究了超碱性碳酸盐溶液中硅酸盐玻璃变化过程中的机制、反馈和产生的非线性。我们的实验装置能够对玻璃溶解和二次相沉淀进行操作可视化和速率测量，并辅以相关相的光谱表征和接近玻璃界面的溶液离子强度的半定量监测。在含 Ba 钠钙硼铝硅酸盐玻璃的初始全等溶解后，形成结晶的皂石基表面改变层 (SAL)，以及随后在皂石孔隙空间内的沸石沉淀、毒重石涂层和碳酸盐沉淀层被观察到。二在操作中实验在~ 90°C 下进行 180 和 260 小时，否则溶液体积 (SV) 仅不同，同时保持表面积恒定。高 SV 实验表现出初始溶解速率的短暂向上偏移，随后是持续快速的玻璃溶解以及缓慢的 SAL 生长和离子强度的持续振荡。相比之下，在低 SV 实验中，玻璃溶解在 SAL 快速生长开始后单调下降，并且没有观察到持续的振荡。我们发现 SAL 的生长条件和由此产生的特性对玻璃溶解速率的演变产生主要的非线性影响。反过来，SAL 的形成取决于成核/生长动力学和玻璃衍生溶质在反应前沿的积累。溶解和沉淀，与溶液化学和传输过程的反馈，共同控制腐蚀过程的演变。此外，破裂、分层和表面形态的演变可能会影响玻璃溶解速率和传输路径。这种对响应于保护层生长的反应速率减速的解释在微观尺度实验和露头到全球尺度的观察中是一致的，物理破坏和形态对表面积产生的加速效应也是如此。因此，这些微米尺度的机械见解可以帮助阐明局部到全球的环境反馈（例如，侵蚀或风化模式）以及工程环境中的过程动态（例如，核废料处理），并可能有助于改进预测模型。