Preparation and properties of magnetic metal cobalt/carbon microwave absorber powders
To overcome the drawbacks of high density and single-mode magnetic loss in magnetic metals,Co-based metal organic frameworks were prepared by precipitation method using Co salt and trimesic acid as raw material and organic ligand,respectively.Magnetic metal Co/C composite microwave absorber powders were synthesized through calcination,and the effects of calcination temperature on the morphology and microwave absorption properties of Co/C microwave absorbers were studied.The results show that calcination temperature significantly affect the morphology and properties of Co/C absorbers,uniformly dispersed particle structure and porous framework structures can be obtained after calcination at 500℃and 600℃,respectively,while chain-like rod structures can be obtained at 700℃and 800℃.The sample calcined at 800℃exhibits the best electromagnetic wave absorption property,with a maximum reflection loss of-35 dB and an effective absorption bandwidth of 0.56 GHz at 13.76 GHz when the tested sample thickness is 4.5 mm.The improvement in microwave absorption property is attributed to multiple loss mechanisms(such as eddy current and exchange resonance),suitable electromagnetic parameters and attenuation constant,and the synergistic effect between the porous structure and various components.
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