Longitudinal and shear ultrasonic velocities were measured in sodium
borate glass samples of different compositions before and after irradiation with
γ-rays. Measurements were carried out at room temperature and 4 MHz
frequency using pulse echo technique. Densities of the glass samples were
measured using displacement method while toluene was used as immersion
liquid. Elastic constants were calculated as well as Debye temperature,
softening temperatures and microhardness for all glass samples. The results
showed that, irradiation of sodium borate glass has less noticeable change on
ultrasonic velocity than the effect of increasing sodium oxide content. The
increase in velocity was attributed to the gradual increase in the rigidity of the
glass and, hence, strengthening of the network due to the gradual change of
boron atoms from the three-fold to the four-fold coordination of oxygen atoms.