One-step synthesis of carbon nanotubes with Ni nanoparticles as a catalyst by the microwave-assisted polyol method

Research highlights: → In this study, CNTs of diameter about 20 nm were firstly synthesized by the microwave-assisted polyol method and magnetic Ni nanoparticles were employed as a catalyst. → As the microwave eddy current effect excited an electric spark on the inner wall, which was plated metal nickel in the glass flask, metal Ni nanoparticles can induce CNTs' formation in the further reaction. → CNTs could be observed after the observation of a small electric spark, and the length of hollow carbon nanotubes was of the order of micron. → The further experimental results indicated that the as-synthesized samples were ferromagnetic. → Ni/CNTs composites exhibited some different ferromagnetic behaviors compared with Ni nanoparticles and bulk Ni. - Abstract: Carbon nanotubes (CNTs) were firstly synthesized by the microwave-assisted polyol method and magnetic Ni nanoparticles were employed as a catalyst in the process. The structures, morphologies and magnetic properties of the as-synthesized samples were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. Our results indicated that CNTs can be synthesized after the observation of a small electric spark with Ni particles used as a catalyst. TEM showed that the length of the hollow carbon nanotubes was of the order of micron. VSM demonstrated that Ni/CNTs composite was ferromagnetic characteristic with hysteretic behavior at room temperature.