Toughening of Carbon Nanotube Fibers by Graphene Oxide Infiltration and Thermal Reduction: A Comparative Study of Graphene Oxide and Reduced Graphene Oxide

We report a facile approach to improve the toughness of carbon nanotube (CNT) fibers through the incorporation of graphene oxide (GO) or reduced graphene oxide (rGO). CNT aerogel yarns were soaked in aqueous GO dispersions (0.18 wt%, 10 min) followed by twisting and densification with ethanol to produce CNT/GO fibers. Subsequent thermal reduction (250 °C, 24 h, −60 mm Hg) produced CNT/rGO fibers. Tensile testing (N ≥ 8), using two-tailed Welch’s t-tests, revealed significantly enhanced toughness for both hybrid CNT/GO fibers (d = 45 ± 10 µm) and CNT/rGO fibers (d = 63 ± 28 µm) compared to the neat CNT fibers (d = 37 ± 8 µm), but through distinct mechanical responses. CNT/GO fibers exhibited a significantly increased elongation from 11.7 ± 6.6 to 22.6 ± 8.4%, while maintaining comparable strength and modulus. Consequently, their toughness increased by 141% from 12.0 ± 5.2 to 28.9 ± 10.7 MJ/m3. In contrast, CNT/rGO fibers exhibited a significant increase in tensile strength from 214 ± 109 to 407 ± 171 MPa, while maintaining comparable elongation and modulus, resulting in a toughness of 19.4 ± 5.7 MJ/m3. Fracture morphology demonstrated that neat CNT fibers showed little evidence of necking, while CNT/GO and CNT/rGO hybrid fibers exhibited necking. These findings demonstrate that simple incorporation of GO or rGO into CNT fibers can significantly enhance their toughness by elongation-driven or strength-driven means, highlighting the potential to tune CNT fiber properties with graphene-based additives.