3D printing and in situ transformation of SiCnw/SiC structures

Abstract

Successful preparation of photopolymerizable ceramic slurries using non-oxide ceramics and their 3D printing is highly challenging as the ceramic powders often possess high UV-light absorbance. Even though pre-oxidation of the powders could improve the slurry printability, the residual oxygen element in the material would eventually deteriorate the material purity and performance. In this study, a separated redox route (pre-oxidation, 3D printing and carbothermal reduction) was proposed to overcome these challenges. SiC ceramic powder was pre-oxidized into SiC@SiO 2 core-shell form to lower the UV-light absorbance. It was found that the ultraviolet (UV) light absorbance value of SiC powder at 405 nm decreased 20% from 0.357 to 0.284 after pre-oxidation process. The UV-light penetration depth of SiC@SiO 2 ceramic slurries at 40 ~ 55 vol% solid loading ranging from 14.81 to 12.82 µm, which surpassed two times that for 40 vol% raw SiC ceramic slurry. Different-shaped structures of SiC@SiO 2 /resin green ceramic bodies were successfully fabricated by vat photopolymerization 3D printing. The oxygen element resided was then eliminated by carbothermal reduction to avoid detriment of SiO 2 to the mechanical performance of the SiC ceramics. Phenolic epoxy acrylate resin with 14 wt% pyrolytic carbon (PyC) yield was chosen as the carbon source and thus the SiC@SiO 2 /resin green body pyrolyzed into SiC@SiO 2 /PyC ceramics after 1200 °C. It was found that after the heating temperature was further raised to 1600 °C, most of the pre-introduced SiO 2 shells on the surface of SiC particles were in situ transformed into SiC nanowires through carbothermal reduction reaction between SiO 2 and PyC, and the content of oxygen element in the ceramic matrix sharply dropped from 20.21% to 2.08%. The results demonstrated that through the proposed redox route, the photopolymerization-related issues including high UV-light absorbance and pre-oxidation-induced impurity for 3D printing of SiC ceramic slurries can be tackled. Finally, high purity porous SiC nw /SiC ceramic components with different structures were produced. This study provides a promising route for the preparation and 3D printing of photopolymerization ceramic slurries using non-oxide ceramics possessing high UV-light absorbance. • UV-light absorbance of SiC powder at 405 nm decreased 20% after pre-oxidation. • UV-light penetration depth of SiC@SiO 2 slurries (40 ~ 55 vol%) surpassed two times that for 40 vol% raw SiC slurry. • Pre-introduced SiO 2 shells on SiC particles in situ transformed into SiC nanowires through carbothermal reduction. • SiC nw /SiC components with complex structures successfully fabricated by photopolymerization 3D printing.