High-strength and toughness CNT films from microwaving-promoted purification and structural reconstruction

Carbon nanotube (CNT) films can now be prepared by catalytic floating chemical vapor deposition (CVD) with low cost and high yield. However, their performance deteriorates drastically due to the presence of impurities and structural defects all over the films. In this study, we report a simple and fast heating and quenching approach to tackle this issue by using a household microwave oven. Experimental results show that the strong interaction between CNTs and low-power microwaves within 10 s not only triggered the diffusion of Fe particles from the interior to the surface of the film for easy purification but also improved the graphitic structure of CNTs and their inter-tube binding for mechanical strengthening and electrical conduction. After a sequential treatment of microwaving-acid washing-microwaving, followed by additional rolling, the final CNT film exhibited a tensile strength of 7.45 GPa, an elongation at break of 11.33 %, and an electrical conductivity of 1.85 × 10⁶ S m⁻¹. The combination of such mechanical and electrical properties is superior to previous fibers and films reported in open literature. Considering its efficient and environment-friendly features, the present approach is suitable for the large-scale production of high-performance CNT films, thereby meeting the requirements for practical applications in many fields.