Suppression of the leading-edge bulge effect in ceramic vat photopolymerization via yield stress regulation for enhanced part performance

• Yield stress regulation eliminates leading-edge bulging in ceramic printing. • Carbomer stabilizes high-solid Si₃N₄ slurry for uniform recoating. • 2 wt% additive produces defect-free 100 mm Si₃N₄ parts with 928 MPa strength. This study addresses the "leading-edge bulge effect" encountered during the ceramic slurry recoating stage in ceramic vat photopolymerization by regulating the slurry’s yield stress to suppress backflow. A three-dimensional network structure was constructed using Carbomer 940 as a thickening agent, thereby enhancing the slurry’s yield stress. A combined approach of numerical simulation and experimental validation was employed to evaluate the impact of yield stress modulation on liquid level control and part performance. When the thickener concentration reached ≥2%, backflow was effectively suppressed, resulting in stable slurry leveling and intact surface quality of printed parts. Under these conditions, the average flexural strength reached a peak value of 928.59 MPa, comparable to that of conventionally sintered silicon nitride. However, excessive thickener content further restricted backflow but led to insufficient slurry coverage, adversely affecting the fabrication of complex geometries. These findings demonstrate that yield stress optimization is critical for achieving a balance between print quality and mechanical performance, offering theoretical guidance for process refinement in ceramic vat photopolymerization.