Synthesis Of Iron Oxide Materials Based On The Thermolysis Method And Its Electromagnetic Wave Absorption Properties

Iron oxide, as a typical magnetic loss material, has a great application prospect in electromagnetic wave absorbing field. Since the crystallinity, morphology and size of the material has a big influence on the electromagnetic wave absorption behavior, here the thermolysis method is adopted to prepare Fe₃O₄ particles with different morphologies and sizes by modulating the thermolysis temperature, to control the crystal growth process. These methods are easy one-pot methods without any template and can get products in large scale. The X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS） and Raman are employed to identify the phase and composition of the samples. The morphology, the size and the content of the samples are characterized by field emission scanning electron microscope（FE-SEM） and Energy Dispersive Spectrometer analysis（EDS）. The static magnetism and electromagnetic parameters are characterized by the vibration sample magnetometer（VSM） and vector network analyzer. The reflection loss values of the samples are obtained by simulation calculation.The Fe₃O₄ nanoparticles with different crystallinities and monodispersities are acquired by modulating thermolysis temperature of ferric acetate, without any structure directing agent, surfactant and reducing agent. The results show that the electromagnetic parameters of the samples are changed with temperature increasing. When the decomposing temperature is 500℃, the as-prepared sample displays the best impedance matching characteristic and reaches the largest magnetic loss value in the high frequency of 13.72 GHz. The electromagnetic wave reflection loss value is-13.28 d B with the thickness of 1.5 mm.The Fe₃O₄ samples with good crystallinity are synthesized by in-situ molten salt thermolysis method using ferric acetate as the precursor. The ferric acetate and the molten salt system are mixed homogeneously according to a certain proportion. It turns out that the calcining temperature has a great influence on the size and saturation magnetization of the sample, thus leading to the electromagnetic parameters. According to the testing results, the octahedral F-800 microparticles are of high saturation magnetization value（86 emu?g-1） and best electromagnetic wave absorption ability. The reflection loss values are all less than-10 dB with the thickness between 1.1¹.5 mm. When the thickness is 1.4 mm, the reflection value reaches-23.67 dB.The ferric triacetylacetonate and NaCl-KCl molten salt system are mixed homogeneously with the Fe₃O₄/C composites are obtained by in situ molten salt thermolysis method. After the heat treatment in the air, γ-Fe₂O₃/C composites are acquired. The C of γ-Fe₂O₃/C decreases the density of the composites and makes them a light weight electromagnetic wave absorption material. Meanwhile the impedance matching characteristic of the obtained γ-Fe₂O₃/C is obviously enhanced. The electromagnetic wave absorption ability of the samples are weak with the thickness of 1.5 mm, however, the ability of them are excellent with the increasing thickness. R-700 shows the best reflection loss value of-38.0 d B with the thickness of 3.5 mm, and the effective bandwidth of the sample with the reflection loss value less than-10 dB（corresponding to the incident wave reflection loss of 90%） reaches 4.28 GHz. R-800 displays the best reflection loss value of-41.86 dB with the thickness of 3.5 mm. While the effective bandwidth of the sample with the reflection loss value less than-10 dB reaches 4.08 GHz when the thickness is 2 mm.