Abstract

Alteration under atmospheric conditions

Alteration under atmospheric conditions

Aurélie Verney-Carron* 1

1 Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France

The understanding and modeling of glass alteration in atmospheric medium is a major concern for the conservation of historic glass, as well as for the safety of the nuclear glass geological disposal. For these different cases, the atmospheric conditions are obviously different. Stained glass windows are subjected to rainfall events, wind, solar radiation… and overall changing conditions. Glass in museum collections can be altered by variable relative humidity and temperature and by internal pollution. The expected unsaturated phase in the geological repository of nuclear glass packages is caused by the release of hydrogen during the steel corrosion. The composition of these glass types is also very different as a function of the time period and context. However, the methodology to study atmospheric alteration is similar. Ancient samples of historic glass have been characterized by different techniques to identify the alteration patterns and their formation processes and to measure the apparent alteration rates. Model historic glass samples have also been exposed in real conditions to investigate the first stages of alteration. And for all types of glass, specific experiments in aqueous medium to simulate rain events and/or at different relative humidity and temperature values, sometimes with additional gases, to simulate the vapor phase, have been performed to determine mechanisms and kinetics. Results show that the alteration mechanisms involved during the atmospheric alteration are quite similar (hydration, interdiffusion, hydrolysis, secondary phase precipitation) but their relative contribution differ in the different situations and by comparison to aqueous medium. We will therefore provide an overview of these mechanisms, of the associated kinetics as a function of specific environmental parameters and of the options to model the alteration of historic and nuclear glasses under atmospheric conditions.