Effect of chemical composition on borosilicate glass behavior under irradiation

Assessing the behavior under irradiation of oxide glasses used for nuclear waste immobilization is essential for qualifying the long-term behavior of the wasteform. This study focuses on a series of borosilicate glasses of increasing chemical complexity. The effects of irradiation in these materials were investigated through multi-energy external irradiation by gold ions to obtain a constant nuclear damage level to a depth of about 2 μm. The macroscopic behavior of the glass was estimated from Vickers hardness measurement. The mechanical properties of all the borosilicate glasses studied were observed to improve, their hardness decreasing with the dose down by 30–35%. This evolution is also associated to an increase of the fracture toughness of the glass under irradiation. Analysis of the structural changes in the sodium borosilicate glass common to all the compositions studied with respect to dose revealed a progressive shift to higher wavenumbers in the vibration Raman band near 495 cm−1 indicating a drop in the mean Si–O–Si angle. At the same time, modifications in the Qn band between 850 and 1200 cm−1 are observed and characterize increasing depolymerization of the silicate network.