Preparation of core-shell Zn-doped CoFe2O4 cubes @ CNT composites and their absorbing performances

Core-shell structured composites of Zn-doped CoFe2O4 cubes @CNTs were in situ synthesised using a CVD method at 450 degrees C C with Zn-doped CoFe2O4 cubes as catalysts and ethanol as carbon source. The as-obtained products were characterised using an X-ray diffractometer, transmission electron microscope, thermogravimetric analyser and vibrating sample magnetometer. Results demonstrated that CNTs uniformly grew on the surface of Zn doped CoFe2O4 cubes to form the shell with average diameter of 20-80 nm. The average diameter of the core/shell Zn-doped CoFe2O4 @CNTs cubes range from 3 to 10 mu m. The magnetic hysteresis curves of Zn-doped CoFe2O4 cubes @CNTs illustrated the strong magnetic response to a varying magnetic field and the saturation magnetisations for the composites obtained at 450 and 600 degrees C C were 33.55 and 10.05 emu g(-1), respectively. A minimum reflection loss of -9.98 dB was observed at 9.2 GHz for the Zn-doped CoFe2O4@ CNTs core/shell composites with a thickness of 2 mm. The Zn-doped CoFe2O4@ CNTs core/shell composites prepared at a higher temperature exhibited better microwave absorbing performance than the sample prepared at a lower temperature.