Conversion of silicon carbide fibers to continuous graphene fibers by vacuum annealing

Abstract Continuous graphene fibers (GFs) and graphene/SiC fibers (G/SiCFs) are fabricated from silicon carbide (SiC) fibers through vacuum annealing. The transformation gradually happens from the surface to the core of the fiber until complete conversion. Graphene sheets are in-situ formed after Si sublimation of 3C–SiC grains in the SiC fiber. Although porous structure is formed inevitably, the fiber shape is well maintained with circular cross section. The continuous GFs exhibit low density (1.63 g/cm3), excellent electric conductivity (53,900 S/m), high tensile strength (0.22 GPa) and elastic modulus (23 GPa, gauge length: 25 mm). Good properties can be probably attributed to interconnected graphene sheets. GFs have great electromagnetic interference shielding effectiveness of 62.8 dB, while G/SiCFs have outstanding microwave absorption properties. The minimum reflection loss (RL) value of −54.86 dB is achieved with sample thickness of 2.1 mm. When sample thickness is 1.4 mm, the effective absorption bandwidth of G/SiCFs can reach 4.4 GHz. Excellent flexibility is also possessed by a bundle of 1000 graphene filaments. Taking advantages of the facile conversion of silicon carbide fibers, the method demonstrated in this work can be further extended to prepare metal-containing GFs (Ti, Al, Zr, et.) and achieve large-scale production.