A novel treatment of carbon fibers with improving tensile strength to synthesize evenly distributed carbon nanotubes on their surface

Well-dispersed iron oxide (Fe ₃ O ₄ ) nanoparticles and evenly distributed carbon nanotubes (CNTs) were synthesized on the surface of carbon fibers pretreated by the concentrated HNO ₃ oxidation and subsequent KOH activation. Results showed that KOH activation provided an opportunity not only to fix a suitable content of oxygen-containing functional groups on carbon fiber surface thus preventing the absorption of large nanoparticles, but also contributed to the formation of numerous nanopores on the fiber surface by etching effect, which could limit the movement of the absorbed nanoparticles. The well-dispersed Fe ₃ O ₄ nanoparticles had a uniform diameter of 122.01 nm and density of 2.47 × 10 ⁹ cm ⁻² . Tensile test demonstrated that the tensile strength of fiber bundles was increased by 30.88% due to the decrease of surface defect size. In addition, CNTs reached a homogenous distribution on the surface of KOH-treated carbon fibers while only CNTs clusters, short CNTs and large pyrocarbon particles were formed on the surface of oxidized carbon fibers. Our work provides a meaningful way to modify carbon fibers with improving the mechanical strength and synthesize well-dispersed Fe ₃ O ₄ nanoparticles as well as evenly distributed CNTs on their surface.