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Altération par l'eau des verres borosilicatés : expériences, modélisation et simulations Monte Carlo

Abstract : This work is concerned with the corrosion of borosilicate glasses with variable oxide contents. The originality of this study is the complementary use of experiments and numerical simulations. This study is expected to contribute to a better understanding of the corrosion of nuclear waste confinement glasses.

First, the corrosion of glasses containing only silicon, boron and sodium oxides has been studied. The kinetics of leaching show that the rate of leaching and the final degree of corrosion sharply depend on the boron content through a percolation
mechanism. For some glass contents and some conditions of leaching, the layer which appears at the glass surface stops the release of soluble species (boron and sodium).
This altered layer (also called the gel layer) has been characterized with nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS) techniques.
Second, additional elements have been included in the glass composition. It appears that calcium, zirconium or aluminum oxides strongly modify the final degree of corrosion so that the percolation properties of the boron sub-network is no more
a sufficient explanation to account for the behavior of these glasses.
Meanwhile, we have developped a theoretical model, based on the dissolution and the reprecipitation of the silicon. Kinetic Monte Carlo simulations have been used in order to test several concepts such as the boron percolation, the local reactivity of
weakly soluble elements and the restructuring of the gel layer. This model has been fully validated by comparison with the results on the three oxide glasses. Then, it has been used as a comprehensive tool to investigate the paradoxical behavior of the
aluminum and zirconium glasses : although these elements slow down the corrosion kinetics, they lead to a deeper final degree of corrosion.

The main contribution of this work is that the final degree of corrosion of borosilicate glasses results from the competition of two opposite mechanisms : the rapid extraction of the soluble species and the reconstruction of the passivating altered
layer.
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Submitted on : Wednesday, March 2, 2005 - 8:33:25 AM
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Aurélien Ledieu. Altération par l'eau des verres borosilicatés : expériences, modélisation et simulations Monte Carlo. Matériaux. Ecole Polytechnique X, 2004. Français. ⟨tel-00008627⟩

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