Study of gel development during SON68 glass alteration using atomic force microscopy. Comparison with two simplified glasses

Literature mentions several physicochemical studies concerning the characterisation of the alteration films that are formed during the dissolution of the nuclear glasses. Up to now, however, no study had been undertaken on the evolution of the alteration film thickness by in situ technique. This study proposes to carry out atomic force microscopy (AFM) in liquid and dry conditions in order to measure the shrinkage or swelling of the alteration film. This work is performed on the glass SON68 and on two glasses with simplified compositions. The results obtained reveal a shrinkage of the alteration film for the simplified glasses and, in situ (underwater), a slight swelling for the SON68 glass caused by the formation of crystalline phase (phyllosilicates) on the surface. In all three cases, when alteration progresses, it increases the density of the gel and the volume occupied by the alteration products tends to be equal to the volume initially occupied by the glass (called isovolumetric alteration). Finally, the drying leads to an important shrinkage. These results could be used to evaluate the potential impact of the internal cracks of an industrial glass block.