| As a typical soft magnetic material, the magnetic properties of Fe-Ni alloy are deeplyaffected by its structure, composition and heat treatment. When Fe-Ni alloy is used aselectromagnetic interference (EMI) shielding materials, its shielding effect is mostlycaused by the absorption to electromagnetic wave, thus it is a kind of ideal electromagneticwave absorber and can be used in the development of low secondary pollution EMIshielding conductive coatings. In this thesis, and the effect of the preparation conditions ofnano Fe-Ni alloy particles on the phases and paricle size, the effect of the compositions andannealing temperatures on the magnetic properties of alloys were studied; theelectromagnetic parameters of the alloy particles were measured; the influence of differentkinds and contents of Fe-Ni alloy powders on the shielding effectiveness while used aselectromagnetic wave absorber in developing the EMI shielding conductive coatings wereaslo discussed.Fe-Ni binary alloy nanoparticles were prepared by solution reduction. Differentreaction conditions (reaction temperature, concentration of total metal ion, volume ofreductant) on the effect of phase and grain size of products were studied, and alloyparticles with different ratios (1:3,1:4,1:6,1:10) of Fe/Ni were successfully prepared. Theexperimental results showed that all the particles prepared are the aggregates of smallgrains; when the reaction temperature was80C, the concentration of total metal ion was1.0mol/L and the volume of hydrazine was13mL, alloy powders had the smallest grainsize and particle size, and the mean particle size was45-60nm. Under the same conditions,alloy powders with different atom ratios can be successfully prepared and the elementratios of Fe/Ni of the products were similar to the initial ratios of [Fe2+]/[Ni2+].The structures and magnetic properties of alloy powders with different Fe/Ni ratiosand annealing temperatures were studied. The results showed that there wasn’t obviouslychange on the component and structrue of alloy powders except for the increase of grainsize and variation of lattice constant after annealing. With the increase of nickel content,the saturation magnetization of Fe-Ni alloy powders decreased and the coercivity increased,while they had opposite variation trend with the increase of annealing temperature. Inaddition, the samples transformed from a half hard magnetic behavior to a typical softmagnetic behavior after annealing.The electromagnetic parameters of different Fe-Ni alloy powders were measured anddiscussed; the results showed that the attenuation of EM wave was mostly caused by themagnetic loss of the four kinds of alloy powders. Coatings were made by adding different alloy powders into a matrix of40wt%acrylic resin and60wt%nickel, then the types andcontents of alloy powders on the effect of coatings’ performance were well discussed, theresults showed that the conductivity of coatings obviously decreased with the addition ofalloy powders. When the contents of alloy powders were the same, the coatings with F1N4and F1N10(Atom ratios of Fe to Ni are1:4and1:10) alloy powders had higher shieldingeffectivenesses than that of coating made without any alloy powders, especially the coatingwith F1N10. By studing the SE of coatings made with different contents of F1N10alloypowders, when the contents were not more than8%of the mass of nickel powder, due tothe increase of electromagnetic wave absorption loss, the SE of the coatings had definitlyincreased, especially when the frequency was below100MHz and between500-1000MHz. The coating with5wt%addition of F1N10alloy had a highest SE value, witch was8-10dB higher than that of coating without any alloy powders. Meanwhile, the absorptionloss proportion had obviously increased in the whole test bandwith, and was above53%,indicating the achievement of the low secondary pollution goal at some extent. |
PDF Full Text Request