| The wide application of various electronic products has brought us lots of convenience,but at the same time the corresponding electromagnetic radiation and electromagnetic pollution have also caused serious troubles.Therefore,developing electromagnetic wave(mainly microwave)absorption materials has become one of hot research topics in recent years.Among many microwave wave absorbing materials,the magnetic loss of iron-based materials have attracted worldwide attention due to their high saturation susceptibility and low cost,however,their high mass density,easy oxidation and single microwave-loss mechanism also limit the further application.Compared to the magnetic loss of iron-based materials,the dielectric loss of carbonbased materials,such as carbon nanotubes,graphene oxide(GO)and porous carbon,has also attracted much attention for wide application in the field of microwave absorption.Among these carbon-based materials,lamellar-structured graphene oxide has the advantages of ultra-low mass density,large specific surface area and high corrosion resistance,but possesses some disadvantages such as easy agglomeration and single microwave-loss mechanism in microwave absorption.Therefore,to prepare high-performance microwave absorbing materials by combining the magnetic loss of iron-based materials with the dielectric loss of carbonbased materials and to ensure their simultaneous occurrence may meet the comprehensive requirements of"thin","wide","light" and "strong" as high-efficiency absorbents.Based on this,the research contents of this are as follows:(1)A ferromagnetic nanocomposite Fe3O4@Fe/Fe4N/CFe15.1-NrGO,which is composed of elemental iron-,iron nitride-and iron carbide-coated ferroferric oxide core-shell structured nanospheres and nitrogendoped partially-reduced graphene oxide(NrGO),has been successfully prepared by combining an initial hydrothermal processing,subsequent reducing agent impregnation and final solid-state thermal reduction.And then,we investigate the effects of the nanocomposite’s content in paraffin dispersion(5.0～15.0 wt%,the interval of 2.0 wt%)and its coating thickness(1.0～5.0 mm,the interval of 0.5 mm)on the microwave absorption performances of this nanocomposite.The results show that,with the increase of the nanocomposite’s filling amount,the microwave absorption properties are an upward trend at first and then go downwards.When the loading mass of Fe3O4@Fe/Fe4N/CFe15.1-NrGO is 9.0 wt%in paraffin dispersion,the minimum reflection loss(RLmin)of microwave is as high as-30.5 dB at the thickness of 1.5 mm,and the corresponding effective absorption bandwidth(EAB<-10 dB)of 4.4 GHz(i.e.,from 13.6 to 18.0 GHz)is the 27.5%of the entirely measuring bandwidth from 2.0 to 18.0 GHz.The excellent microwave absorbing performances of nanocomposite Fe3O4@Fe/Fe4N/CFe15.1-NrGO may be attributed to the following twoaspects:(i)the interfacial polarization of the core-shell structure of spheroidal iron-based constituents and the interface between an iron-based nanosphere and dielectric lamellar NrGO and(ii)a synergistic effect between dielectric properties of lamellar-structured NrGO and the magnetic properties of core-sell structured Fe3O4@Fe/Fe4N/CFe15.1.(2)A ferromagnetic nanocomposite Fe/Ni-NrGO,which is composed of nanosphere shaped iron-nickel alloy Fe/Ni and nitrogen-doped partially-reduced graphene oxide NrGO,has been successfully prepared by combining an initial solvothermal processing with subsequent solid-state thermal reduction.Upon this preparation,we investigate the effects of the nanocomposite’s content in paraffin dispersion(10.0～40.0 wt%,the interval of 10.0 wt%)and its coating thickness(1.0～5.0 mm,the interval of 0.5 mm)on the microwave absorption properties of this nanocomposite.The results show that the detected microwave absorption performance goes upwards with the increase of Fe/Ni-NrGO filling amount.When the loading weight percentage of the nanocomposite is 40.0 wt%,the minimum reflection loss(RLmin)is as high as-32.3 dB at the thickness of 1.5 mm,and the corresponding effective absorption bandwidth(EAB<-10 dB)ranges from 13.1 to 17.1 GHz(i.e.,4.0 GHz in bandwidth)that is a 25%of the entirely measuring bandwidth.In addition,at the Fe/Ni-NrGO loading mass of 40.0 wt%,the total electromagnetic interference shielding effectiveness(EMI SEtotal)amplitude can attain 17.86 dB at the frequency of 8.32 GHz,and the corresponding EMI shielding efficiency is over 90%.Anyway,either the involved interfacial polarization in the integral structure of nanospherical Fe/Ni,lamellar NrGO or a synergistic effect between the dielectric properties of NrGO and the magnetic properties of Fe/Ni could hardly neglected to explain the observed excellent electromagnetic properties of the nanocomposite. |
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