Single-step additive manufacturing of silicon carbide through laser-induced phase separation

Silicon carbide (SiC) tubes are fabricated through femtosecond high-energy ultra-short pulsed laser powder bed fusion (LPBF) additive manufacturing. Widespread implementation of pulsed LPBF of SiC compounds is hampered by a poor understanding of the material–laser interaction for such short processing times and under such extreme thermal regimes, which is due to the complexity of SiC materials. In this investigation, binding and phase separation mechanisms of SiC powders driven by pulsed laser–material interactions are elucidated using numerous state-of-the-art analytical tools as well as theoretical calculations. Partial disintegration of 6H-SiC powders into silicon and carbon during laser sintering is demonstrated to bind SiC powder particles together with no measurable SiO2 phase formation. During femtosecond laser–material interactions, 6H-SiC decomposes into silicon and carbon at high temperatures and localized high pressure state on the process. Decomposition of 6H-SiC is corroborated by density functional theory (DFT) calculations. Furthermore, relatively large (~200 nm–1.5 µm) pockets of 6H-SiC, 3C-SiC, repetitive nanoscale-pattern “nanobreathing” (~2–20 nm) of 6H-SiC and highly oriented pyrolytic graphite spheres are formed. The experimental observations indicate the viability of the synthesis of highly oriented spheroidal pyrolytic graphite and 3C-SiC and 6H-SiC grains, and thin elements of silicon and carbon, using high energy short-pulse laser irradiation.