Preparation And Properties Of Fe₃O₄Nanoparticles And Its Composite Materials

In recent years, Fe₃O₄ferrite especially magnetic Fe₃O₄nanomaterials and its composites haveattracted more attentions and studies because of its potential applications in ferrofluid, magneticabsorbing material and biomedicine. Hollow structured magnetite spheres with various sizes werefabricated by a simple solvothermal process. The morphology and crystal structures of the productswere characterized by X-ray diffraction （XRD）, emission scanning electron microscope （SEM） andtransmission electron microscopy （TEM）, respectively, and the vibration sample magnetometer（VSM）,FT-IR and m ssbauer were used to study the magnetic properties. The electromagnetic（EM）absorbing performance wave also studied. The Fe₃O₄@SiO₂nanoparticles with core-shell structurewere prepared with the improved st ber and improved the Fe₃O₄oxide stability, under a hightemperature with reducing gas, the composite materials can convert to Fe@SiO₂and Fe/Fe₃O₄@SiO₂materials; Fe₃O₄/GNS composite materials were aiso prepared with different synthetic methods. Themagnetic properties and EM absorbing performance were investigated by VSM and vector networkanalyzer.Hollow structured Fe₃O₄naonospheres were successfully synthesised by the solvothermal process,with the assistance of various ammonium salts. Fe₃O₄spheres were ferromagnetic with smallhysteresis loops and the values of saturation magnetization are82.989,78.049and87.417emu/g forS-a,S-b and S-c samples, which decreases with increasing particle size. The maximum reflection lossup to-40dB appeared in8⁹GHZ for the hollow structure samples. Fe₃O₄@SiO₂nanoparticles withcore-shell structures were fabricated through control of different experimental conditions. Fe@SiO₂materials were obtained under hydrogen atmosphere, the reduced composite materials have greatreflection loss over a wide frequency range, and the stability of composite material were enhanced,but the thickness with best reflection loss is bigger. The Fe₃O₄/GNS composite materials wereobtained by solvent thermal method in situ with acetylacetone iron as iron source. In the Fe₃O₄/GNScomposite, the Fe₃O₄particles has good dispersion. The magnetization （M） of the Fe₃O₄/GNScomposite is low. Compared to the Fe₃O₄, the value of reflection loss is decrease but the absorptionband of the composite material increases.