| The rates of extraction of Li20 and Si02 from silicate glasses containing up to
34 mole per cent Li20 were studied. From the composition containing 7 mole per cent
Li20 hardly any Li20 could be extracted, apparently due to entrapment of the lithium
silicate phase in a matrix of silica. On raising the Li20 content to 10 mole per cent and
above, the separated phase became progressively continuous and the rate of extraction
increased sharply. Boro-silicate glasses containing 10 and 12 mole per cent of Li20 and
B20 3 respectively, were readily attacked by water due to the presence of a more readily
soluble phase. The soluble phase having a probable composition around 1.5 Li20, 1 B20 3,
1 Si02, could be selectively extracted from one of the glasses leaving a skeleton containing
over 92 per cent Si02 and hardly any Li20. Compositions comparatively richer
in Li20 and B20 3, disintegrated in water presumbly due to the presence of the insoluble
phase as islets in a matrix of soluble boro-silicate phase. Replacing B20 3 by Al20 3 in
one of the glass compositions, the resistance to water attack increased by over t1-ro
orders of magnitude. The mechanism of water attack has been discussed in relation to
the structure and phase separation phenomena. |
