Preparation And Microwave Absorption Properties Of The Fe-based Metallic Composite Materials

With the rapid development of modern communication technology, the electromagnetic signals of the electronic devices and systems are spread extensively and the effect of electromagnetic interference (EMI) on electronic control systems becomes a serious problem. As EMI suppressing coatings, microwave absorption materials have attracted extensive attention. As a kind of microwave absorption materials, metallic magnetic materials and their alloys have attracted much attention due to high saturation magnetization, high permeability and high Curie temperature. It is a conventional method to obtain a good impedance matching by mixing metallic magnetic materials with other materials.In this work, four series of microwave absorption materials were prepared by ball milling method and autocatalytic reduction method. The microstructure, static magnetic characteristics, high frequency electromagnetic characteristics and microwave absorbing properties of the materials were studied. The main conclusions are as follows:(1) FexCo1-x/Al2O3and FexNi1-x/Al2O3composites were prepared by mechanochemical method. After10h of milling, it is found that the particle-size distributions of FeCo/Al2O3FexNi1-x/Al2O3composites are from sub-micron to several microns. The diffraction peaks of FexCo1-x and FexNi1-x alloys shift to a low angle with the increase of Fe content.The Ms and Hc of FexCo1-x/Al2O3composites increase first and then decrease with the increase of Co content, and the maximum value of Ms appears when Co content is30at.%. Both ε’ and ε" of the samples decrease as the content of Fe increases, and the μ’ and μ" have no a significant change. The values of RL can reach-20dB in the range of0.95-8.3GHz with the absorber thickness of1.8-9.4mm by adjusting the content of Fe in the sample.The Ms of FexNi1-x/Al2O3composites decrease with the increase of Ni content and the Hc increase first and then decrease. Both complex permittivity and complex permeability of the samples decrease with the increase of Ni content. The values of RL can reach-20dB in the range of1.2-9.3GHz with the absorber thickness of1.8-9.5mm by adjusting the content of Fe in the sample.(2) Flake shape carbonyl iron powder (FSCIP) and Ni hollow sphere (NHS) were prepared by ball milling method and autocatalytic reduction method, respectively, and mixed them together with different mass rate. The particle-size distributions of NHS are from sub-micron to several microns. The Ms and Hc of NHS are11.3emu/g and65.1Oe, respectively. Both complex permittivity and permeability of the samples increase with the increase of FSCIP content. The values of RL of Sample A can reach-20dB in the range of3.6-18GHz with the absorber thickness of1.1-3.9mm. The values of RL can reach-20dB in the range of1.2-18GHz with the absorber thickness of1.1-8.2mm by adjusting the content of FSCIP in the sample.(3) Three samples were prepared by ball milling method using NaCl as dispersant and alcohol as progress control agent. After10h of milling, the morphology of carbonyl iron powder turns from sphere to flake. The particle size is about several microns and the thickness is about500nm. Compared with the sample without NaCl, the surface of the sample with NaCl is rough. The resonance frequency of μ" shifts to a low frequency with the increase of NaCl content. The values of RL of Sample C can reach-20dB in the range of3.0-18GHz with the absorber thickness of1.2-4.6mm. The values of RL can reach-20dB in the range of1.7-18GHz by changing the absorber thickness and adjusting the content of NaCl in the ball milling.