Study on the gel casting of fused silica glass

Slip casting process is usually applied for the forming of fused silica products. Segregation always occurs and it will results in density deviation. By using gel casting process, green is fabricated by means of in situ polymerization with a three-dimensional network, holding the particles together and eliminating the tendency of migration. To prepare gel casting slurries, premix solutions were composed of acrylamide and N,N′-methylenebisacrylamide. Solid loading was kept 60% and the average particle size of silica powder 8–8.5 μm. Lactic acid was introduced as a dispersant to regulate the pH value 3–4. Mechanism of the dispersant was investigated by studying ζ-potential at different pH. Ammonium persulfate (NH₄)₂S₂O₄ was added as an initiator. Gelation took place with the help of initiator at 50–60 °C. Nanometer silica was introduced to boost sinterability so that the density and bending strength of fused silica ceramics have been increased to 2.1 g/cm³ and 40 Mpa, respectively.