The composition, MgO 20.3, Al20 3 18.3 and Si02 61.4 per cent, corresponding
to the ternary eutectic at 1345° in the system Mg0-Al20 3-Si02, can be approximately
obtained using a mixture of talc and clay. Hot stage microscopic studies revealed that the
gross eutectic mixture of talc and clay readily melts to clear glass at a temperature
as low as 1375°C. The observation has been discussed in the light of
earlier X-ray and DT A studies and it has been concluded that rapid vitrification
of the mixture is due to high reactivity of the starting materials.
High temperature viscosity, thermal expansion, transverse strength, resistance
to water attack, the DC and AC resistivities and dielectric strength of the eutectic
glass composition were measured and it has been shown that most of the
properties compare favourably with those of the soda-lime-silica and the heat resistant
boro-silicate type of glasses. |