Spectral changes in Si–O–Si stretching band of porous glass network upon ingress of water

Water ingress into porous glass can induce internal stress, resulting in strains in chemical bonds of the network. For silica and silicate glasses, the position of Si–O–Si stretching mode in infrared spectroscopy is known to vary with the degree of strain in the Si–O network. Then, one could hypothesize that the stress due to water ingress could be probed with infrared spectroscopy. We tested this hypothesis using porous layers formed through aqueous corrosion on a model nuclear waste glass. The porosity and thickness of the porous layer were determined using ellipsometry. The humidity-dependent infrared spectra of the samples showed red-shifts of the Si–O–Si stretching band; however, it was difficult to deconvolute the spectral change due to variation of effective refractive index of the sample upon water ingress. Thus, it was infeasible to unambiguously determine the internal stress of porous glass network upon water ingress using the infrared spectroscopy alone.