Densification process of borosilicate glass powders under hydrothermal hot-pressing conditions

Borosilicate glass powders containing Li₂O over 3.3 wt% were densified by the addition of water under hydrothermal hot-pressing conditions at 25 MPa below 300° C. The initial shrinkage proceeded by a viscous flow mechanism. The glass powders with a high concentration of network-modifying oxides had high densification rates. At low temperature, the glass powders were gently densified after an induction period in which shrinkage was very slow. During the induction period, the glass powders reacted with water and lithium in the glass structure was dissolved in water.