Development of thick-walled ceramic parts via vat photopolymerization using low-viscosity non-reactive diluent as an additive

Abstract

Vat photopolymerization (VPP) is widely studied for manufacturing ceramic parts due to its cost-effectiveness, high efficiency, and excellent resolution. However, defects in complex, thick-walled structures induced by manufacturing process often restrict its application. This study reports the successful development of defect-free, thick-walled ceramic parts using VPP by incorporating gamma-valerolactone (GVL), a circular, safe, biomass-derived diluent, into SiO₂ suspension. This addition effectively controlled defect formation throughout both printing and debinding. Specifically, introducing 50 vol% GVL into organic solution reduced the viscosity of the SiO₂ suspension by 38–48 % at a high solid loading of 67 vol%, thereby eliminating inner pore defects during printing. Furthermore, this modification reduced the volume shrinkage of the SiO₂ suspension during printing by 40 %, significantly alleviating residual shrinkage stress. Remarkably, the toughness of the green sample containing 50 vol% GVL remained exceptionally high during printing and debinding, effectively resisting stress-induced defect formation, particularly interlayer cracks. Microstructural analysis revealed that sufficient exhaust ducts formed when the diluent evaporated at the first debinding stage under lower temperatures, facilitating the release of pyrolyzed gases at the second debinding stage under higher temperatures and thus mitigating gas expansion stress. The defect-free mechanisms can mainly be the balance of the mechanical properties and the process-induced stresses. These findings indicate that ceramic suspensions enhanced with high concentration of non-reactive diluent hold significant promise for manufacturing defect-free, thick-walled ceramic parts through VPP in industrial applications.