Incorporating Nanoparticles in Alumina Ink for Improved Solid-Loading and Sinterability of Extrusion-Based 3D Printing

Nanoparticles (NPs) show many unique and advanced behaviors compared to micron-sized particles and above. The effect of NPs on the rheological and sintering nature of direct ink writing (DIW) [extrusion-based three-dimensional (3D) printing] inks has been comprehensively studied. The inks were first formulated through particle size grading of microalumina and nanoalumina (NA) with aqueous-based solvents, and it was found that the solid volume in ink increases up to a certain volume of NA (2%) inclusion due to the change in friction mechanism between particles. Meanwhile, the presence of high volumes of NA (≥3 vol %) reduces solid-loading in ink due to agglomeration of NPs for printable rheology. Second, different NA (0–5 vol %)-containing optimized rheological inks were printed by DIW and sintered at temperatures of 1300–1600 °C. Higher solid-loading ink retaining 2 vol % NA shows low volume shrinkage, and 5 vol % NA-containing ink reaches 97% density at temperatures as low as 100 °C than without NA ink. Including NPs in the ceramic 3D printing technology decreases the use of organic contents (reduce greenhouse effect) and also effectively reduces the shrinkage and fabricates a dense printed structure by eliminating binder-burnout generated pores at a low temperature (energy conservation).