Oxygen-Free Pretreatment Enables Crack-Free Air Debinding in Vat Photopolymerized Silicon Nitride (Si3N4) Green Bodies

Additive manufacturing of ceramics by vat photopolymerization (VPP) faces persistent challenges during thermal debinding, as air atmospheres often induce severe cracking in green bodies, limiting industrial viability. This study identifies a critical mechanism: low-temperature oxidative decomposition (LTOD) of incompletely cured acrylates below 200 °C in air, which generates trapped gases before escape channels can form, leading to cracking. Through thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR), we demonstrate that these acrylates undergo premature oxidative cleavage under air, whereas oxygen-free (argon, nitrogen, or vacuum) pretreatment during the initial debinding stage effectively suppresses this phenomenon. Experimental results confirm that applying an oxygen-free environment below 200 °C eliminates low-temperature cracking, allowing subsequent debinding to proceed safely in air. This optimized, staged-atmosphere process produces crack-free silicon nitride green bodies and yields sintered ceramics with exceptional mechanical properties (flexural strength: 1218.4 MPa; fracture toughness: 9.37 MPa·m 1/2 ). The proposed strategy offers a cost-effective and scalable solution for reliable air debinding in ceramic additive manufacturing, providing both theoretical insight and practical guidance for advancing high-performance, low-cost ceramic 3D printing.