Sol-Gel Synthesis of Clear Uncracked Silica Glass with Large Pore Sizes

Silica glass is a useful optical material because of its excellent transparency, good radiation hardness, high chemical stability and mechanical strength.In this study, clear uncracked silica glasses were manufactured via sol-gel synthesis. Sol-gel method is a wet chemical process that is suitable for manufacturing silica glasses at relatively low temperatures (1000-1300°C) without melting. The basic concept used in this experiment was assembling a mold containing the precursor solution of different elements mixed in a certain ratio in a low pH for the sol to convert to gel. The precursor solution was then heated in a small oven to form a dried gel followed by additional heating in a larger oven to 1300°C till a sample of clear uncracked glass was obtained. Large pore sizes are desired in the glass because it helps to prevent fractures or crack formations. A chemical named Tetraethyl orthosilicate/ Tetraethoxysilane (TEOS) was used as the silicon source provider that reacted with water under ethanol as a solvent. Besides these chemicals, the other two chemicals used were Hydrofluoric acid (HF) and Dimethylformamide (DMF). Hydrofluoric acid worked as an acid catalyst and also helped to form large pore sizes and DMF worked as a drying control chemical additive (DCCA) helping to prevent hydrogen bond network in the solvent in order to eliminate any crack formations.