Preparation And Microwave Absorption Properties Of Fe₃O₄/Dielectric Composites

In this paper,ferrierrous oxide and dielectric materials were compounded by in-situ self-polymerization,mechanical stirring physical mixing and pyrolysis.The Fe₃O₄@NC and Fe₃O₄/ZnO composites were successfully prepared with dopamine as carbon source,nitrogen source and zinc acetate as precursor.The composite was characterized by X-ray diffractometer,transmission electron microscope,scanning electron microscope,Raman spectrometer and vector network analyzer and the microwave absorption characteristics of samples were analyzed.The results show that the different content of the dielectric material will affect the absorbency of the sample.The Fe₃O₄@NC composites were prepared by in situ self-polymerization using dopamine as carbon source and nitrogen source,and the amount of dopamine in the self-polymerization process was controlled to adjust the content of NC in Fe₃O₄@NC composites.The results showed that the NC layer was successfully coated on Fe₃O₄ surface by this method,and the microwave absorption characteristics of the composite sample were greatly improved compared with that of the pure phase Fe₃O₄ particles,and the wave absorption performance of the sample was closely related to the NC content on the surface of the composite material.When the amount of dopamine was 2 mM,the wave absorption performance of Fe₃O₄@NC composite material reached the best.When the thickness of the sample is 3.6 mm,the maximum reflection loss at 7.8 GHz can reach-48.8 dB,and the frequency band width below-10 dB in the range of 1-18 GHz can reach14.1 GHz,and the corresponding thickness is 1.5-6.0 mm.The excellent absorbing performance can be attributed to the synergistic effect of magnetic loss and dielectric loss and the enhancement of interfacial polarization.The Fe₃O₄/ZnO composites have been successfully prepared by mechanical stirring physical mixing and pyrolysis method,the Fe₃O₄ particles were thoroughly mixed with a certain amount of Zn?CH₃COO?₂·2H₂O in absolute ethanol,and the mixture was subjected to heat treatment at500?under nitrogen atmosphere to decompose Zn?Ac?₂·2H₂O.ZnO particles and Fe₃O₄particles were fully combined to obtain Fe₃O₄/ZnO composites.The morphology and structure of the samples were characterized by SEM,XRD and XPS.The effects of different amounts of Zn?CH₃COO?₂·2H₂O on the absorbing properties of the samples were investigated by vector network analyzer.The results show that when the weight ratio of the Fe₃O₄ to Zn?CH₃COO?₂·2H₂O is 1:2,the absorbing properties of Fe₃O₄/ZnO composites are obviously improved compared with pure Fe₃O₄.When the frequency is 11 GHz,the optimum reflectivity is-14.4 dB and the corresponding coating thickness is 3 mm.The research shows that Fe₃O₄@NC and Fe₃O₄/ZnO composite materials designed and synthesized take Fe₃O₄ as the main body.Compared with pure phase Fe₃O₄,the composite process is simple,the cost is low,and the wave absorption performance has been greatly improved.It is a microwave absorbing material with a good development prospect.