Preparation and magnetic properties of multiwalled carbon nanotubes decorated by Fe₃ O₄ nanoparticles

Iron oxide (Fe₃ O₄) nanoparticles with average sizes of 6 and 10nm were synthesized by a chemical co-precipitation method from mixtures of FeCl₂ · 4H₂O and FeCl₃ · 6H₂O. They were ultrasonicated with HNO₃-oxidized MWCNTs in a solution (water/ethanol=1∶1v/v) to carry out the decoration. The structure and properties of as-obtained Fe₃ O₄/MWCNT composites were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometry, X-ray diffraction and thermal gravimetry. Results showed that the Fe₃ O₄ mass fraction in the composites were 26.6 and 29.3% for particle sizes of 6 and 10nm, and their saturation magnetizations were 16.5 and 7.5emu · g^-1 respectively.