1. Compare the softening points for 96% silica, borosilicate, and soda–lime glasses.
2. The viscosity 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 versus l/T should be nearly linear, and with a slope of Qvis/R.
Using the data in Figure 13.14,
(a) make such a plot for the borosilicate glass, and
(b) determine the activation energy between temperatures of 500 and 900°C.