Synthesis And Microwave Absorption Properties Of Fe(Co/Ni/Zn) Doped Cerium Dioxide/reduced Graphene Oxide Composites

Reduced graphene oxide(RGO)has special physical and chemical properties and it’s also one of the typical conductive microwave absorbing materials.Dielectric semiconductor oxide CeO2 has fluorite structure and unique oxygen vacancy defects,the combination of CeO2 and RGO could improve the microwave absorbing properties.The doping of CeO2/RGO compositeswouldadjust the impedance matching of the composites and induce the lattice distortion of CeO2 crystal,enrich the concentration of oxygen vacancy in the structure and improve dipole polarization.The synergistic effect among the composites components could promote the microwave absorption properties of the composites.In this work,based on the former researches of CeO2/RGO composites,a series of Fe(Co/Ni/Zn)doped CeO2/RGO composites were prepared through a hydrothermal method according to different added ratio of raw materials.X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)andscanning electron microscopy(SEM)were used to characterize the structure,composition and the morphology features of composites.Vector network analyzer(VNA)was applied for measuring the electromagnetic parameters of the composites,the relative reflection loss in 2-18 GHz was calculated by transmission line equation.The detailed characterization results are as follows:the synergistic effects among the components improve the microwave-absorbing properties of composites.1、GO was synthesized by modified Hummers’s method.Using RGO and cerium nitrate hexahydrate as the substrate and source of cerium,cobalt nitrate hexahydrate as dopant,preparing the Co-doped CeO2/RGO composites.The effect of different added ratio on the structure,morphology and microwave absorbing properties of the composites were discussed.Experiment results show that:the doping of Co didn’t change the structure of CeO2 crystal,and bring amounts of oxygen vacancies which could enhance the dipole polarization in the materials.The Co-doped CeO2 nanoparticles were densely attached on the surface of RGO nanosheets,promote the absorption to electromagnetic wave.When the ncO:nCe(added ratio)was 1:6 in the composites,it would reach the maximum values of reflection loss-53.66 dB at 6.4 GHz with the thickness of 3.5 mm.The biggest bandwidth of reflection loss below-10 dB was 4 GHz with a thickness of 2 mm.2、Using RGO and cerium nitrate hexahydrate as the substrate and source of cerium,nickel nitrate hexahydrate as dopant,preparing the Ni-doped CeO2/RGO composites.The effect of different added ratio on the structure,morphology and microwave absorbing properties of the composites were discussed.Experiment results show that:the doping of Ni didn’t change the unique structure of CeO2 crystal and increase the magnetic loss in the low frequency,adjusting the impedance match of the composites.The corresponding frequency of the maximum reflection loss peak in the measuring range is moving to lower frequency with the increasing of thickness.When the nNi:nCe(added ratio)was 1:4 in the composites,the maximum reflection loss values of the composites was-21.79 dB at 6.72 GHz with the thickness of 4 mm.3、Using RGO and cerium nitrate hexahydrate as the substrate and source of cerium,ferrite nitrate nonahydrate(zinc nitrate hexahhydrate)as dopant,preparing the Fe(Zn)-doped CeO2/RGO composites.The effect of different added ratio on the structure,morphology and microwave absorbing properties of the composites were discussed.Experiment results show that:the doping of Fe(Zn)didn’t change the structure of CeO2 crystal and the lattice distortion brought by doping would promote the performance of microwave-absorbing.For Fe-doped CeO2/RGO composites,with the increasing of nFe:nCe(added ratio),the skin depth would get bigger,so that the reflection loss values of composites would increase with the increasing of matching thickness.When the nFe:nCe(added ratio)was 1:4 in the composites,composites would obtain the maximum reflection loss values-16.36 dB,the matching frequency and thickness were 2.64 GHz and 4.5 mm.For Zn-doped CeO2/RGO composites,when the nzn:nCe(added ratio)was 1:4,the maximum reflection loss values would reach-36.88 dB at 9.28 GHz with the thickness of 2 mm.The optimal bandwidth of reflection loss below-10 dB was 4.8 GHz(12.8-18 GHz),almost covers the entire Ku band.