Systematic Optimization of Monomer System and Bimodal Particle Size Distribution for Alumina Slurries in DLP Additive Manufacturing.

Digital light processing (DLP)-based additive manufacturing of ceramics requires photocurable slurries with high solid loading, low viscosity, and excellent photocuring behavior. In this study, the effects of monomer composition and optimized bimodal alumina powder formulations on the rheological behavior, photocuring characteristics, printability, and sintering behavior of high-solid-loading alumina slurries were investigated. Five commercial photocurable monomers with different functionalities were evaluated to optimize the resin formulation. Among them, a binary monomer system consisting of 2-hydroxyethyl acrylate (2-HEA) and 1,6-hexanediol diacrylate (1,6-HDDA) at a weight ratio of 6:4 exhibited a favorable combination of low viscosity and photopolymerization behavior under the investigated conditions. Using this optimized resin, 50 vol.% alumina slurries containing two optimized bimodal powder formulations (2 μm/100 nm and 4 μm/400 nm) were prepared. The 4 μm/400 nm formulation showed higher double-bond conversion during UV curing, whereas the finer 2 μm/100 nm formulation produced higher relative density after sintering because of its superior packing efficiency. The optimized binary monomer system also suppressed lateral over-curing, resulting in improved dimensional accuracy compared with the single-monomer resin. Among all formulations, the slurry containing the 2 μm/100 nm bimodal powder and the optimized binary monomer system exhibited the best overall performance, including stable printing, minimal delamination, the highest relative density, and uniform sintering shrinkage. These findings provide practical design guidelines for the formulation and processing of high-solid-loading photocurable alumina slurries for DLP additive manufacturing.