| In order to solve the problem of electromagnetic wave pollution caused by the growth of electronic communication equipment,the exploration of efficient electromagnetic wave absorption materials（also known as microwave absorption materials）is of great importance.In recent years,wave absorption materials have been the focus of research to develop reasonable material configurations and effective preparation methods to obtain high performance absorbers to meet the needs of"thin,wide,light and strong".Due to the limitations of single-loss absorbers,such as poor impedance matching and narrow absorption bands,multi-loss composite absorbers have become a hot research topic.Shape and structure control is an effective strategy to regulate the absorption characteristics.One-dimensional structures have received a lot of attention from researchers due to their high aspect ratio and shape anisotropy.Carbon materials have been widely used as wave-absorption materials due to their low cost,light weight,dielectric properties and excellent electrical conductivity.However,single carbon materials are difficult to obtain ideal impedance matching and need to be compounded with other materials to achieve excellent wave absorption performance.In this paper,five one-dimensional carbon-based composite wave-absorption materials are designed and prepared,their microstructure,phase composition and magnetic properties are characterized,electromagnetic parameters and wave absorption properties are investigated,the main studies are as follows.（1）One-dimensional ZnFe2O4@carbon@Mo S2/Fe S2 composites were assembled using ZnFe2O4 nanoparticles prepared by the solvothermal method as the assembly unit,covered with polymer using distillation-precipitation polymerization induced by an applied magnetic field and coated with a layer of Mo S2/Fe S2 heterojunction using hydrothermal method,and finally carbonized to obtain one-dimensional ZnFe2O4@carbon@Mo S2/Fe S2 composites.The one-dimensional and heterojunction structure helps to induce multiple reflection/scattering of microwaves and the multiple interfaces between the structures enhance the interfacial polarization.The composite shows a strong microwave absorption capability with a minimum reflection loss value of-52.5 d B at 13.2 GHz when the thickness is 2.23 mm,an effective absorption frequency range of 10.10-15.08 GHz and an effective bandwidth of 4.98 GHz.It is expected that the synthesized ZnFe2O4@carbon@Mo S2/Fe S2 composites could be a promising material for electromagnetic wave absorption.（2）CoFe2 alloy particle-doped carbon fibers were prepared by electrostatic spinning technique and high temperature calcination,and a layer of Mo S2 flowers was clad on the outside of the CoFe2/C fibers using hydrothermal method.The excellent absorption performance of the composites is mainly due to the one-dimensional structure and the ideal impedance matching,and the CoFe2/C@Mo S2 composites show a strong absorption capacity.The optimum reflection loss reaches-66.8 d B（13.28 GHz）at a matched thickness of 2.12 mm,and it has an effective absorption frequency range of 10.70-16.02GHz and an effective bandwidth of 5.32 GHz.（3）The ZnFe2O4/C composite fibers were prepared by electrostatic spinning technique and high temperature calcination,and then polypyrrole was successfully coated on the surface of the ZnFe2O4/C composite fibers by chemical polymerization.the ZnFe2O4/C@PPy composite exhibited excellent electromagnetic wave absorption performance,and at a loading of 25 wt%and a matched thickness of 1.93 mm,the optimum reflection loss value is up to-66.34 d B（13.80 GHz）with an effective absorption bandwidth of 5.74 GHz（11.78-17.52 GHz）.The efficient absorption performance of the ZnFe2O4/C@PPy composite is mainly attributed to the dielectric loss and the ideal impedance matching.（4）N-doped carbon fibers embedded with Co Ni alloy particles were successfully synthesized by electrospinning techniques and carbonization,and a conductive polypyrrole coating was applied to the Co Ni/C fiber surface by chemical polymerization.The synthesized Co Ni/C@PPy composites show excellent electromagnetic wave absorption properties due to the synergistic interaction between Co Ni,nitrogen-doped carbon fibers and PPy.The optimum reflection loss is-68.78 d B（12.90 GHz）at a thickness of 2.43 mm and a filler content of 15 wt%,and the widest effective absorption bandwidth is 5.62 GHz at a thickness of 2.10 mm and a filler content of 20 wt%.The excellent electromagnetic wave absorption performance is mainly due to the three-dimensional network structure,the great impedance matching and the strong dielectric loss.（5）MgFe2O4/Mg O/C fibers were successfully prepared via electrospinning technology and carbonization,and their surfaces were coated by Mo S2 via hydrothermal method.The electromagnetic wave absorption performance of composites was enhanced due to the introduction of Mo S2.The results showed that the electromagnetic wave absorption performance of MgFe2O4/Mg O/C could not meet the requirements due to low dielectric loss and poor impedance matching.The performance of composites was improved after coating of Mo S2,which showed the strong wave absorption capability and the broad absorption bandwidth.The optimal reflection loss（RL）is-56.94 d B at 9.5 GHz and the effective absorption bandwidth is 3.9 GHz（8.08-11.98 GHz）with a thickness of2.7 mm.The excellent electromagnetic wave absorption performance can be mainly attributed to excellent synergistic effect between MgFe2O4/Mg O/C and Mo S2.Furthermore,Mo S2 also contributes to dielectric loss and ideal impedance matching.In summary,five one-dimensional magnetic carbon-based absorbers were prepared and their absorption properties were systematically investigated.The results show that the prepared absorbers all have excellent performance and good application prospects,providing new ideas and technical support for the preparation of efficient one-dimensional electromagnetic wave absorption materials in the future. |
PDF Full Text Request