Beyond UV: Near-infrared light enabled vat photopolymerization for direct 3D printing of dense SiC ceramics

Ultraviolet (UV)-based vat photopolymerization (VP) of silicon carbide (SiC) ceramics has been challenging because of the strong UV absorbance and high refractive index of SiC. However, strategies such as particle modification or the use of coarser particles have led to low sample densities and/or impurities that diminish the final properties of printed SiC ceramics. Herein, a novel VP method driven by near-infrared (NIR) light to enable direct three-dimensional (3D) printing of SiC ceramics using unmodified fine SiC particles was demonstrated. A type II photopolymerization resin system was first identified and optimized to allow 50–60 wt% SiC particles to be loaded and printed with NIR light. The use of NIR light offered penetration depths of up to 4 times and cure depths of up to 2 times greater than those of UV-based photocuring for a slurry containing 50 wt% SiC particles, along with much better printing fidelities, where the deviation from the designed dimensions was only ±6.8% (vs. 165.5% for UV light). The NIR-based printed SiC ceramics possessed excellent mechanical properties, with flexural strengths reaching (290±20) MPa at a relative density of 86.29%, which was significantly greater than that of many other VP-printed SiC ceramics (approximately 100–220 MPa) at similar densities. These properties were achieved without any additional particle modification or post infiltration steps, allowing the VP of SiC to be as practical as the VP of common oxide ceramics such as alumina and zirconia.