The effects of α-irradiation upon the microstructure was studied by using various experimental techniques. Small-angle X-ray scattering measurements revealed the presence of inhomogeneities of about 1nm in the untreated samples. After annealing these samples, transmission electron microscopic images exhibited a contrast structure and He pycnometry revealed density changes. Both results were typical of glass-phase separation. After irradiation, the glass density had increased and the small-angle X-ray scattering intensity had decreased; thus indicating the occurrence of a compositional homogenization process in samples which were subjected to a higher irradiation dose. The numbers of displacements which were produced by each 10B(n,α)7Li reaction were estimated to be 580, and involved distances of up to 1.5nm. An increase in the density of the irradiated samples could be explained in terms of the atomic displacements which were produced by the nuclear reaction cascades of the reaction, 10B(n,α)7Li. In the case of the present glasses, which exhibited fine phase separation, the density of the Si-rich phase increased with the incorporation of Na and B atoms. The B-rich phase also increased its density, with a flow of Si atoms from the matrix. Vacancies which were created by irradiation of the glass structure were responsible for a density decrease. The final effect was due to the sum of all of the contributions which, in this case, resulted in a net density increase of irradiated samples. It was suggested that the understanding of this phenomenon might lead to the design of glasses which could withstand irradiation, with a minimal density change.

The Effects of Radiation on the Density of an Aluminoborosilicate Glass. M.O.Prado, N.B.Messi, T.S.Plivelic, I.L.Torriani, A.M.Bevilacqua, M.A.Arribere: Journal of Non-Crystalline Solids, 2001, 289[1-3], 175-84