Slurry preparation and forming process optimization of silicon nitride ceramic with digital light processing technology

Digital light processing （DLP） technology has attracted significant attention for its ability to quickly form complex structure porous silicon nitride （Si3N4） ceramics without the need for molds. However， challenges still exist regarding the rheological properties， stability， and curing performance of the Si3N4 ceramic slurry. This paper successfully enhances the rheology and curing performance of Si3N4 slurries by optimizing the multi-component photosensitive resin， dispersant system， and photocuring forming parameters. The results show that the multi-component resin system consisting of HDDA， TMP3EOTA， and ACMO at 3∶1∶2 mass ratio achieves optimal performance. Compared to the system containing IBOA， ACMO has no strong conjugated groups， and its morpholine ring can stabilize the free radicals of photoinitiators， achieving 95% increase in curing depth of the Si3N4 slurry. After the introduction of the dispersant Solsperse 41000， the stability and rheological properties of the slurry are further improved. As the content of Solsperse 41000 increases， the viscosity of the Si3N4 slurry first decreases and then increases； when the dispersant content reaches 3% of the powder mass， the slurry viscosity drops to its minimum value （0.16 Pa·s）. However， the addition of an excessive amount of dispersant will lead to multi-layer adsorption on the powder surface and self-entanglement of the dispersant itself， which impairs the rheological properties of the slurry. Based on the above optimizations， adjusting the laser power and exposure time to 15 mW/cm2 and 7 s， respectively， can simultaneously meet the requirements for both curing depth and forming precision. Finally， Si3N4 ceramic green bodies with complex structures are successfully printed， and a porous Si3N4 ceramic with porosity of 18.76% and flexural strength of 240.28 MPa is ultimately produced. This study provides an experimental basis for the preparation of high-performance porous Si3N4 ceramics.