Determination of silicate liquid thermal expansivity using dilatometry and calorimetry

A method for the determination of relaxed silicate liquid molar volume and expansivity at temperatures just above the glass transition is discussed. The molar expansivity of the liquid is calculated by a fictive temperature normalization of the relaxation behavior of both the heat capacity and the molar expansivity in the glass transition region, with the normalized heat capacity curve being used to extend the dilatometric data into the liquid temperature range. This comparison is based upon the assumed equivalence of the parameters describing the relaxation of volume and enthalpy. The molar expansivity of relaxed sodium trisilicate (Na₂Si₃O₇) has been determined in this manner at temperatures above the glass transition temperature. -from Authors