Grafting of carbon nanotubes onto carbon fiber surfaces by step-wise reduction of in-situ generated diazonium salts for enhancing carbon/epoxy interfaces

Covalent grafting of carbon nanotubes (CNTs) on surfaces of carbon fibers (CFs) has been carried out in aqueous by using the diazonium salts with p-nitroaniline as the starting material. The p-nitroaniline was encapsulated into the cavity of β-CD to form “ host-guest” complexes. The “host-guest” complexes were reacted with NaNO2 in a HCl solution to in situ generate nitrophenyl diazonium salts, which were directly grafted onto CF surfaces, with dinitrogen molecules evolved. Thereafter, the nitro groups on the CFs were electrochemically reduced into amine groups, which can be further converted into the new diazonium groups in a HCl aqueous solution containing NaNO2. The newly-generated diazonium salts on CFs were used to covalently immobilize multi-walled CNTs, yielding the CNT/CF hybrids. The CNT/CF hybrids can improve the CF/epoxy interfacial adhesion strength by 114%, and simultaneously the CF tensile strength remained well.207