Synthesis Of Fe₃o₄ Nanoparticles And The Composite Materials And Study Of Their Performance

In this paper, the preparation of Fe₃O₄ nanoparticles; the conversion of Fe₃O₄ toγ-Fe₂O₃ andα-Fe₂O₃; the preparation and properties of Fe₃O₄/β-CD and GMB/Fe₃O₄ core-shell composite materials were systemically studied, respectively.Fe₃O₄ nanoparticles were synthesized by reduction-precipitation method in water solution. The microwave absorbing property of the sample was measured by RAM reflectivity far-field RCS which showed that Fe₃O₄ nanoparticle was a kind of good microwave absorbing material at high-frequency. The products of Fe₃O₄ heated at 150℃, 200℃, 300℃and 400℃were characterized by XRD and VSM. It was observed that Fe₃O₄ transformed forγ-Fe₂O₃ with superparamagnetic character at 300℃, then transformed forα-Fe₂O₃ when the temperature reached 400℃. The coercive force (800Oe) ofα-Fe₂O₃ appeared along with the particle size grew. The products agglutinated along with the temperature elevated.β-CD was placed into the preparation solution of Fe₃O₄ at different reaction temperature, different reaction time and different mole of proportion to prepare good dispersivity Fe₃O₄/β-CD composite material. The preparation mechanism of Fe₃O₄/β-CD was discussed. The magneto-optical phenomenon was observed. It also found that theβ-CD coating could restrain the growth of Fe₃O₄ nanoparticles and enhance their stability in air. The sensitivity of particle size to reaction time was greatly reduced at low temperature which provided a new method to obtain Fe₃O₄ particles with small size.We coated Fe₃O₄ nanoparticles on the surfaces of the pretreated GMBs to provide superparamagnetic hollow microspheres with low density (0.4-0.5g/cm3). The magnetization of GMB/Fe₃O₄ could be controlled by changing the GMB content and the reaction temperature. The mechanism of how Fe₃O₄ nanoparticles coated on the surfaces of GMBs were proposed.