Increase Of Annealing Point Of 96% Sio2 Glass On Incorporation Of Carbon

The annealing point of reconstructed 96% SiO2 glasses is markedly increased by incorporating carbon in porous glass and firing in a dry, monoxidising atmosphere. Numerous pyrolysable organic compounds can be used as a source of carbon. Furfuryl alcohol, which is miscible in water, is preferred since it can be readily polymerise in the porous glass into a nonvolatile resin by heating. Relatively low concentrations of furfuryl alcohol are sufficient to increase markedly the viscosity of the final fired glasses. Infrared spectra show that carbon is an excellent dehydroxylating agent, removing silanol and boranol groups which, if left in the structure, soften the final glasses.