Effect of pH and Ratio of Alumina Sol on Properties of 3D Printed Silica Ceramics

3D printed silica ceramics have the advantages of low thermal expansion coefficient, high thermal stability, easy removal, etc., and are widely used in ceramic core manufacturing. However, in the sintering stage, silica often cracks due to shrinkage and phase transformation, which seriously affects the mechanical properties of the material. The impregnation of alumina sol can promote the formation of cristobalite phase in ceramics, and the mechanical properties of ceramics can be improved with appropriate amount of cristobalite. In this study, 3D printed silica ceramics were impregnated with alumina sol, and the effects of pH value and the concentration of alumina in the sol on the properties of the samples were investigated. When pH was 2.5, the mechanical properties of alumina sol impregnated samples reached a flexural strength of 24.98 +/- 0.93 MPa, with a bulk density of 1.70 +/- 0.01 g/cm3, and an open porosity of 25.82 +/- 0.33%. When the ratio of alumina sol to silica sol was 3:1, the mechanical properties of alumina sol impregnated ceramics reached the maximum, with a flexural strength of 33.85 +/- 1.69 MPa, a bulk density of 1.73 +/- 0.01 g/cm3, and an open porosity of 24.02 +/- 0.72%.