| Abstract Scope |
Experience and data have shown that the viscosity equation, ln(Viscosity) = A + B(T)/T, should meet the following assumptions: 1) the coefficient A is independent of composition; 2) glass viscosity is independent of composition at the glass transition temperature, Tg; 3) when Viscosity < 10^2 to 10^3 Pa s, depending on the glass family and measurement accuracy, B is independent of temperature (i.e., B = Ba). The Adam–Gibbs equation meets these postulates with a minimum number of temperature-independent coefficients when the configuration entropy is expressed as a power-law function of temperature. With the Tg known as a function of composition, only one coefficient in the viscosity equation (Ba or s0, the dimensionless configuration entropy) is a function of composition to be fitted to data. The simplicity and elegance of the proposed viscosity relationship has been demonstrated using a large base of viscosity data for (simulated) nuclear waste glasses. |