Microwave-assisted synthesis and magnetic properties of size-controlled CoNi/MWCNT nanocomposites

Research highlights: → Size-controlled CoNi alloy nanoparticles with quasi-spherical and face-centered cubic structure attached uniformly on the surface of multi-walled carbon nanotubes were prepared by microwave-assisted method. → The size of CoNi alloy nanoparticles with average diameters in the range of 15-48 nm can be controlled though adjusting the atomic ratios of metals to carbon nanotubes in the mixed acetate solution. → Magnetic measurement shows that both the coercivity and the saturation magnetization increase with the increase of the particle size from 15 nm to 37 nm, and decrease from 37 nm to 48 nm. - Abstract: Size-controlled CoNi alloy nanoparticles with average diameters in the range of 15-48 nm attached on the multi-walled carbon nanotubes (MWCNTs) were prepared to form CoNi/MWCNT nanocomposites by microwave-assisted method. The size of CoNi alloy nanoparticles can be controlled through adjusting the atomic ratios of metals to carbon nanotubes in the mixed acetate solution. The as-prepared nanocomposites have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-disperse X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). The results show that CoNi alloy nanoparticles are face-centered cubic structure, quasi-spherical and disperse uniformly on the surface of MWCNTs. Magnetic measurement shows that both the coercivity and the saturation magnetization of the samples increase with the increase of the particle size from 15 to 37 nm, and decrease from 37 to 48 nm.