Fluid-cell Raman Spectroscopy for operando Studies of Reaction and Transport Phenomena during Silicate Glass Corrosion.

Fluid-cell Raman Spectroscopy (FCRS) enables the real-time and space-resolved (operando) study of reaction mechanisms, kinetics, and their mutual interactions with transport processes during silicate glass corrosion at the micrometer scale and at elevated temperatures. This manuscript provides a detailed protocol for setting up an FCRS experiment, exemplified by a corrosion experiment with a ternary Na borosilicate glass and a 0.5 M NaHCO3 solution at a temperature of 86 ± 1 °C. The protocol involves (i) sample preparation, (ii) assembly of the fluid cell, and (iii) setting of Raman measurement parameters for collecting Raman spectra across the sample/solution interface in regular time intervals. The results from the experiment show the formation of a water-rich zone between a silica-based surface alteration layer (SAL) and the pristine glass, which is an intrinsic feature of an interface-coupled dissolution-precipitation model for the formation of a SAL during silicate glass corrosion. The ability to track the reaction and transport processes during the corrosion of silicate glasses and potentially of other transparent materials, spatially resolved and in real-time, represents a unique strength of this technique, overcoming the disadvantages of conventional analysis of multi-step quenching experiments. The corrosion of the top side of the glass sample represents a current issue, reducing spatial resolution at depth due to precipitation within the laser pathway. This is caused by a solution-filled gap between the sapphire window of the fluid cell lid and the top side of the monolith, which is difficult to avoid during the experimental setup. This must be taken into account when choosing the depth at which the measurement should be made. In a few cases, the formation of air bubbles was observed, which disrupted or even led to the termination of the experiment. However, this can be avoided by carefully setting up the experiment, which requires little practice.