Swelling of Microporous High‐Silica Glasses

The swelling of microporous glasses in water was found to change as a function of the heat–treatment time and temperature required for phase separation in the original borosilicate glass (70SiO 2 ‐23B 2 O 3 ‐7Na 2 O (wt%)). The swelling appears to be determined primarily by the quantity of silica gel remaining in the micropores, which in turn is determined by the composition of the alkali‐borate‐rich phase of the phase‐separated glass.