Study On Preparation And Absorbing Properties Of Core-shell Structure Fe20Ni80/Cu Composite Nanopowders

Magnetic nanoparticles possess a large Specific surface area and unique ferromagnetism, it can effectively attenuate electromagnetic waves by the interaction with electromagnetic waves, therefore, it was widely used in electromagnetic wave absorbing materials. In addition, the core-shell magnetic nanoparticles tend to have a wider absorption range and a higher strength of electromagnetic waves than a single nanoparticle, it was supposed to be a new absorbing material with broad band and high attenuation.In this article, the author prepared FeNi alloy nanopowders by liquid phase reduction method, made a systematic study on the morphology and absorbing properties of FeNi alloy powder with different atomic percentage, then optimized the preparation of FeNi alloy nanopowders; made a coating on the surface of FeNi alloy nanopowders with the conductive material Cu to integrate their absorbing characteristics in different frequency bands, finally, obtained the core-shell nanoparticles with stable properties and good absorbing properties.Research showed that the size of nano alloy powders particle( atomic percentage of FeNi was 5:5, 4: 6, 3: 7, 2:8 respectively)was about 100 nm, there was no iron oxide among Fe20Ni80 powder phase,it was the most stable product.Fe20Ni80 alloy powder possessed the best relatively absorbing performance, in the band of f≤6GHz, the electromagnetic waves loss mechanism was magnetic loss,while in the band of f>6GHz, it absorbed electromagnetic waves in dielectric loss mode. Fe20Ni80 powder(80wt%)/ epoxy composite sheet which was thickness of4 mm displayed the best effect of absorbing, the absolute value of reflection coefficient reached up to the maximum 37.88 at frequency of 2.36 GHz, Fe20Ni80 alloy nanopowders was an excellent absorbing agents.By using orthogonal experiment and combined with the experience of previous experiments, made a systematic combination of reaction temperature, reaction time,reactant concentration and pH of the reaction solution to explore the preparation of Fe20Ni80 alloy powder, ultimately determined the experimental parameters whichproduced the minimum aggregate size as the optimum preparation, namely the reaction temperature was 75 ℃, reactant concentration was the same with original process, pH was 13, the reaction time was 30 min.Core-shell nano Fe20Ni80/Cu composite powders prepared by liquid phase reduction method was uniform composition, the diameter of composite powder particle was about 100nm; it possessed good absorbing properties over whole range of frequency 1~18GHz, at band of 1 ~ 10 GHz, the composite powder lost electromagnetic waves mainly through magnetic loss, the principal electromagnetic waves loss mechanisms turned to dielectric loss at band of 10~18GHz,especially in the range of 12~18GHz, core-shell nano Fe20Ni80/Cu composite powders possessed a much better ability of dielectric loss than Fe20Ni80 alloy powders, the loss factor was about 1.25 to 2.45 in this frequency range.