Rheological properties of SiC suspension for direct ink writing

Silicon carbide is one of the most widely used ceramic materials today due to its excellent properties such as high strength, light weight and high temperature resistance. However, the traditional preparation method has long production cycle, high cost and is difficult to manufacture relatively complex structures. In this paper, the SiC slurry used in direct ink writing was studied to fabricate SiC ceramics with 3D complex structure. The effects of dispersant content, pH, solid loading and thickener on the rheological properties of SiC suspension were investigated. Printable SiC suspension was prepared and direct-written into three-dimensional lattice structures of silicon carbide. The results show that the optimum content of dispersant results in the lowest paste viscosity; pH affects the dissociation of the dispersant to change the viscosity of the paste; the higher the solid loading, the stronger the printable structural integrity; and the addition of methyl cellulose (MC) increases the viscosity and shear elastic modulus of the slurry, making it printable. The optimized silicon carbide slurry formulations are: 0.01% polyacrylic acid (PAA)in mass fraction, 63% solid loading and 0.04% MC in mass fraction, pH > 10, respectively.