Gelcasting of fused silica glass using a low-toxicity monomer DMAA

A low-toxicity and water-soluble monomer N,N-dimethylacrylamide (DMAA) was used as gelling agent in gelcasting of fused silica glass. In order to make high solid loading and low-viscosity slurries, acrylic acid-2-acrylamido-2- methypropane sulfonic acid copolymer (AA-AMPS) was selected as dispersant. Zeta potential, pH, dispersant dosage, solid loading and milling time have been investigated to prepare the optimum gelcasting slurries. The results suggest that the best conditions were pH 4.8, dispersant dosage 0.1-0.2 wt.% and milling time 5 h. Gelation of slurries took place with the help of initiator at 65-80 C. Flexural strength of dried fused silica green bodies with only 3.04 wt.% polymers reached up to 20.16 MPa. Nanometer silica was introduced to boost sinterability by immersing green bodies in the tetraethyl silicate solvent. Bulk density and flexural strength of sintered fused silica bodies without obvious crystallization have been increased to 1.975 g/cm³ and 81.36 MPa, respectively.