Effect of Oxide Nanoparticles in Aqueous Alumina Inks for Material Extrusion Additive Manufacturing

The effects of the addition of nanoparticles (NPs) of alumina (NA) and silica (NS) on the rheological properties of aqueous-based ceramic inks for material extrusion-based additive manufacturing (ME-AM) and sinterability of printed ceramic components were investigated. The inks were first designed using bimodal particle sizes of NPs with micro-alumina, and their solids fraction in printable inks was found to be dependent on the functionalization properties of NPs. NAs create a lubricating effect in the ink system and improve solids-loading in the ink. Meanwhile, NSs form silanol bonds in aqueous-based inks that increase viscosity and reduce solids-loading for a printable ME-AM ink. The inks containing NPs with higher solids-loading and optimized rheology were printed using ME-AM, and the printed components were sintered at 1400-1550ºC. Adding NPs in the ink significantly improved the sinterability of printed shapes by enhancing sintering kinetics and filling-effects, with NS having a more significant effect than NA.