Insights into the mechanisms controlling the residual corrosion rate of borosilicate glasses
| Autor: | Kamalesh Damodaran, Xiaolei Guo, Sebastien N. Kerisit, Stéphane Gin, J.M. Delaye, Frédéric Angeli, Véronique Testud, Jincheng Du, Seong H. Kim |
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| Rok vydání: | 2020 |
| Předmět: |
010302 applied physics
Solid-state chemistry Materials science Passivation Thermodynamic equilibrium Borosilicate glass Materials Science (miscellaneous) Diffusion 02 engineering and technology Activation energy 021001 nanoscience & nanotechnology 01 natural sciences Corrosion Chemical engineering Chemistry (miscellaneous) 0103 physical sciences TA401-492 Materials Chemistry Ceramics and Composites Leaching (metallurgy) 0210 nano-technology Materials of engineering and construction. Mechanics of materials |
| Zdroj: | npj Materials Degradation, Vol 4, Iss 1, Pp 1-9 (2020) |
| ISSN: | 2397-2106 |
| Popis: | Borosilicate glasses are widely used to confine high-level radioactive wastes. The lifetime of these materials could reach hundreds of thousands of years if leaching of the glass into groundwater enables the formation of a passivating gel layer. Even in this regime, the glass will never stop corroding as thermodynamic equilibrium between glass and solution cannot be achieved. Therefore, accurate predictions of glass durability including passivation, require a deep understanding of the mechanisms controlling the so-called residual rate. However, despite tremendous efforts, these mechanisms remain poorly understood. Here, focusing on the behavior of the soluble elements of the International Simple Glass (B, Na, and Ca), we show that the residual rate is controlled by the behavior of B, a glass former supposed to dissolve instantaneously when in contact with water and thus widely considered as an ideal tracer. We then demonstrate that B release is controlled by multiple processes highly dependent on the pH. At the beginning of the passivating layer formation, the hydrolysis of B-O-Si linkages is rate-limiting and has an activation energy of ∼60 kJ mol−1, a value slightly lower than that for breaking Si-O-Si linkages. Once the fraction of closed pores resulting from gel restructuring is high enough, then diffusion of both reactants (water molecules) and some products (mainly Baq, Caaq) through the growing gel layer becomes rate-limiting. Consequently, B and Ca accumulate in an inner layer referred to as the active zone, with potential feedback on the B-O-Si hydrolysis. A new paradigm, including B as a key element of the system, is proposed to develop a comprehensive model for the corrosion of borosilicate glass. |
| Databáze: | OpenAIRE |
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