The Study On The Surface Modification For Iron Based Magnetic Power Absorption Agent

The research about high-performance absorbents has great significance for thedevelopment of absorbing material. Usually magnetic metal particles are used as theabsorbents because their complex permeability is large, then they can be prepared in theform of thinner absorbing coating. But its real permittivity and imaginary permittivity arealways large, it is difficult to achieve impedance matching in the process design ofabsorbing material. So more and more attention is paid on reducing the complexpermittivity of the magnetic metal powder absorbent at microwave frequencies, andreducing the reflection from the surface of coating for incident electromagnetic wave inorder to make it as more as possible into the coating and be absorbed or be attenuated off.In this paper, iron based magnetic powder with a core-shell structure was preparedwith chemical method and mechanical ball grinding method through surface coatingmodification. The characterization of morphology and composition of magnetic metalparticles was analysed by SEM and XRD, complex permeability and complex permittivityof composite materials were tested;（1） sol-gel method was used as chemical method, withtetrabutyl titanate （TBT） as coating agent, to coat the surface of flaky SMSS （Fe-Cr-Si-Al）alloy magnetic metal by TiO₂. We have studied some factors which influence theproperties of coated surface layer, such as dosage of coating agent, reaction temperature,catalyst and the types of solvent and so on. Through comparing the microwaveelectromagnetic parameters with both coated and not coated alloy magnetic metal particles,we have obtained better coating condition: both the dosage of iron base magnetic powderabsorption agent and coated agent are5g, the time of reaction is5h, reaction temperatureis30℃, ammonia is used as catalyst. The flaky carbonyl Fe magnetic metal particles werechosen as research objects, and ethyl silicate （TEOS）, titanate coupling agent, methylmethacrylate and inorganic phosphating liquid were used as precursor for SiO₂, TiO₂,polymer membrane and inorganic phosphating liquid membrane, and the influence ofelectromagnetic properties about absorbent were studied.（2） QM-ISP4planet ball millwas used in mechanical ball grinding method. We have chosen flaky carbonyl Fe magnetic metal particles as research objects, and studied SiO₂, TiO₂, organic polymer membrane forthe influence of electromagnetic properties about absorbent.The results revealed that each coating agent could largely reduce the complexpermittivity and keep the complex permeability unchanged basically. The electromagneticcharacteristics is useful for impedance matching of absorbing coatings, and decreasing thereflection coefficient of absorbents. In this paper, we first used titanate coupling agents ascoating agents to modify the surface of Fe magnetic metal particles, and high reflectioncoefficient was obtained for them.