Ion release characterization in phase separated borosilicate glass powders

A series of novel borosilicate ionomer glasses composed of varying amount of SiO2–B2O3–K2OCaO–Al2O3 were investigated. The influence of the thermal treatment was evaluated in terms of ion release and glass microstructure. Inductively coupled plasma optical emission spectrometry (ICP-OES) and scanning electron microscopy (SEM) were the main analytical techniques used in this study. The results show that all the glasses samples were amorphous according to the XRD and the SEM results before and after the heat-treatment. However, whilst the as-quenched samples appeared consistently transparent and colourless, the thermal treatment at 700 °C for 20 h induced some of the samples to turn opalescent. The ion concentration profiles suggest that the dissolution rate of Ca and B were enhanced by the heat treatment in all cases. Moreover, it was confirmed that different leaching rates exist between the opal and clear samples