Abstract
Concentrated, aqueous colloidal gels of barium titanate (BT) have been formulated for use as ink in a direct write, solid freeform fabrication process. Micron‐sized BT particles were stabilized by ammonium polyacrylate (APA) and then gelled by salt or cationic poly(electrolyte) additions to achieve shear thinning with yield‐stress rheology. Monovalent cation salts were found to simply increase the ionic strength, whereas divalent cation‐gelled suspensions displayed evidence of bridging flocculation. Suspensions gelled with cationic poly(ethylenimine) (PEI), likewise, exhibited high gel strengths, indicating bridging flocculation. Oscillatory shear measurements revealed that equilibrium and dynamic visco‐elastic properties depended on both the concentration and the molecular weight of the PEI, with higher molecular weight species providing more efficient gelation. PEI and divalent salt flocculated BT gels were evaluated for their performance in the direct write process by printing three‐dimensional lattices.
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