142.
Alkoxide derived gels were prepared in the system Na
2O---B
2O
3---SiO
2. The gel compositions were situated in the liquid-liquid immiscibility area of the phase equilibrium diagram.
Hydrolytic resistance tests were performed on the gels heat-treated at temperatures ranging between 120 to 850 °C. The Na2O, B2O3 and SiO2 extracted from the attack gels were analyzed. The experimental results indicate that the amount of B2O3 has a significant influence on the chemical durability of the heat-treated gels. At temperatures of 850 °C the greater the B2O3 mol% the greater are the amounts of Na2O and B2O3 extracted. Different behaviour was observed for gels heat-treated at 600 °C where the amounts of B2O3 and Na2O extracted slightly increases as the B2O3 mol% increases. Small amounts of extracted SiO2 were always observed.
These results are complemented with other measurements so that an explanation of the controlling mechanism is given. 相似文献