The viscosity n of a glass varies with temperature according to the relationshipwhere Qvis...

The viscosity n of a glass varies with temperature according to the relationship

where Qvis is the energy of activation for viscous flow, A is a temperature-independent constant, and R and T are, respectively, the gas constant and the absolute temperature. A plot of ln n versus l/T should be nearly linear and have a slope of Qvis/R. Using the data in Figure 14.17, (a) make such a plot for the borosilicate glass, and (b) determine the activation energy between temperatures of 500 and 900°C.

Figure 14.17 Logarithm of viscosity versus temperature for fused silica and three silica glasses.