A highly coercive carbon nanotube coated with Ni0.5Zn0.5Fe2O4 nanocrystals synthesized by chemical precipitation–hydrothermal process

Novel magnetic composites (Ni0.5Zn0.5Fe2O4–MWCNTs) of multi-walled carbon nanotubes (MWCNTs) coated with Ni0.5Zn0.5Fe2O4 nanocrystals were synthesized by chemical precipitation–hydrothermal process. The composites were characterized by X-ray powder diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy (MS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), etc. A temperature of about 200 °C was identified to be an appropriate hydrothermal condition to obtain Ni0.5Zn0.5Fe2O4–MWCNTs, being lower than the synthesis temperature of a single-phase Ni0.5Zn0.5Fe2O4 nanocrystals. The sizes of Ni0.5Zn0.5Fe2O4 in the composites were smaller than those of Ni0.5Zn0.5Fe2O4 nanocrystals in single phase. The composites exhibited more superparamagnetic than Ni0.5Zn0.5Fe2O4 nanocrystals in their relaxation behaviors. The magnetic properties measured by a vibrating sample magnetometer showed that the composites had a high coercive field of 386.0 Oe at room temperature, higher than those of MWCNT and Ni0.5Zn0.5Fe2O4 nanocrystals.