Rheological behavior of Al2O3 suspensions containing polyelectrolyte complexes for direct ink writing

Al 2 O 3 polyelectrolyte suspensions containing PAA-PEI complexes have been used for direct ink writing to fabricate complex 3D structures with micro-sized feature. Zeta potential and rheological behavior of the Al 2 O 3 polyelectrolyte suspensions were investigated. The isoelectric point of Al 2 O 3 particles shifts from alkaline region to acidic region as the [COOH]:[NH x ] ratio increases from 0.12 to 3. The rheological results reveal that the 40   vol% Al 2 O 3 suspension with [COOH]:[NH x ] ratio of 0.3 and 15   mg/mL methylcellulose at pH   10 is the optimal suspension for direct ink writing, due to its good shear thinning and viscoelastic behavior . The filament in lattice structure prepared using this polyelectrolyte suspension can maintain its original shape with little spreading. In the micrograph of sample sintered at 1600   °C for 2   h, the uniform size of grains indicates that the structure is fully sintered under this sintering condition.