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

Al2O3 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 Al2O3 polyelectrolyte suspensions were investigated. The isoelectric point of Al2O3 particles shifts from alkaline region to acidic region as the [COOH]:[NHx] ratio increases from 0.12 to 3. The rheological results reveal that the 40 vol% Al2O3 suspension with [COOH]:[NHx] 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 degrees C for 2 h, the uniform size of grains indicates that the structure is fully sintered under this sintering condition. (C) 2017 Published by Elsevier B.V.