Fabrication And Electromagnetic Microwave Absorption Properties Of Iron Based Epoxy Resin Nanocomposites

Fe and carbon-coated Fe(Fe@C) nanoparticles synthesized by a DC arc-discharge plasma method were characterized by XRD and TEM for their phases and structures. It revealed that both Fe and Fe@C nanoparticles were in sphere shapes. Fe@C nanoparticles possess a core/shell structure with Fe core and graphite-like outside shell. According to the experimental results, the condition for the pretreatment of nanoparticles were confirmed. It’s clear that the dispersion of iron nanoparticles improved by the surface with KH550, while Fe@C nanoparticles were well dispersed in lipophilicity solvents without any modification due to the existence of graphite-like outside shell.With differential scanning calorimetry(DSC), the influences of curing agent and heating rate on the epoxy resin curing were studied. In the practical operations, the optimal curing processing for Fe and Fe@C/epoxy resin(EP) nanocomposite were confirmed as below. For Fe/epoxy resin nanocomposite(Fe/EP), the curing process is110℃/0.5h+23℃/1.5h+134℃/2h; while for Fe@C/epoxy resin nanocomposites(Fe@C/EP), it is90℃/1.5h+110℃/0.5h+123℃/lh+134℃/2h.Complex electromagnetic parameters of Fe/paraffin and Fe@C/paraffin nanocomposites were experimentally measured in2-18GHz. Theoretical analysis indicated that polarization mechanisms for nanoparticle include the interface polarization, space charge polarization and dipole polarization. The existence of graphite-like shells enhanced the interface polarization and the space charge polarization for Fe@C nanoparticles. Magnetic losses for the nanoparticles are attributed from the natural resonance, possible exchange resonance and domain resonance. Graphite-like would weaken the magnetization of Fe@C nanoparticles.The actual reflection loss of Fe/epoxy resin and Fe@C/epoxy resin nanocomposites were experimental measured in2～18GHz range. Compared by measured and computed reflection losses, it was indicated that, the matrix’s density and electromagnetic properties would greatly affected on the electromagnetic properties of nanocomposites.Based on the analyse of mechanisms for magnetism and polarization, an attempt to fit the complex permittivity and complex permeability were carried out. Theoretical fitting of complex permittivity spectra were done by the universally dielectric law and Cole-Cole equation, those were then compared with measured ones. It was indicated Cole-Cole equation can accurately exhibit the fluctuation of complex dielectric spectra. Meanwhile, it was also reasonable to replace multi-polarization with orientation polarization in microwave range. Take Bruggeman equation and Mclachlan generalised effective medium approximate(GEM) as the tools, their applications on the complex permittivity and complex permeability were inspected. For magnetic considerations, the intrinsic permeability of Fe nanoparticles was theoretical calculated from Landau-Lifshitz-Gilbert equation and the dependence of nanoparticles contractions were calculated by effective medium theory. It’s clear that the calculations can well exhibit a same tendency with the measured complex permeability.