| At present,various types of wireless electronic devices have been widely used in the military,modern transport,communications,electronic information and internet industries.They not only bring great convenience to human life,but also make the human living environment full of electromagnetic radiation pollution.Materials that absorb electromagnetic waves are materials that eliminate the energy interference of electromagnetic waves or promote a different form of energy to dissipate.In recent years,Mo2C@C nanoparticles embedded in carbon matrix have attracted much attention in microwave absorption because of the abundant heterogeneous interface between carbon and Mo2C nanoparticles.In practice,electromagnetic wave absorption must have a strong absorption capacity,effective range and a thin layer thickness.In order to meet these requirements,the microstructure and morphology of the absorbing material should be reasonably designed and regulated.In this work,the microstructure design is used to control the morphology of composite materials,and the impedance characteristics of materials are optimized with the help of simple manufacturing process,so as to comprehensively improve the performance loss and further improve the absorption performance.The main work content of this paper includes the following aspects:(1)The flower spheres(Mo2C@C(FCN-Mo2C)composite was prepared by using ammonium molybdate as molybdenum source and dopamine as monomer.After carbonization in situ under N2 atmosphere,the flower spheres(FCN-Mo2C)composite was formed by carbon nanosheets embedded with ultrafine Mo2C nanoparticles.By adjusting the addition amount of ammonium molybdate in the precursor preparation solution,the particle size of molybdopamine could be regulated,and then the particle size,BET and composition of FCN-Mo2C could be regulated,so as to regulate the wave absorbing performance.When molybdopamine was prepared and the amount of ammonium molybdate was 15 mg,the FCN-Mo2C composite was prepared with excellent absorbing properties.Its addition amount in paraffin matrix is only 10 wt%,the matching thickness is 2.9 mm,and its effective frequency bandwidth(EAB)can reach 7.04 GHz,achieving full Ku band coverage.(2)Using ammonium molybdate as molybdenum source,dopamine as monomer and ethanol/water as mixed solvent,hollow flower spherical molybdenum-polydopamine(Mo-PDA)was prepared by interfacial self-assembly method based on the difference of solubility of molybdenum-dopamine chelate in ethanol and water.The hollow flower ball Mo2C@C(HS-Mo2C)composites were synthesized by carbon nanosheets embedded with ultrafine Mo2C particles after in-situ carbonization under N2 atmosphere.By adjusting the amount of dopamine added in the precursor preparation solution,the cavity size of the hollow blossom spherical molybdopamine could be adjusted,and then the cavity size of HS-Mo2C could be adjusted,so as to regulate the absorbing performance of HS-Mo2C.When the amount of dopamine hydrochloride was 300 mg,the HS-Mo2C composite had excellent wave-absorbing performance.When the amount of dopamine hydrochloride was 15 wt%in paraffin matrix and the matching thickness was 2.7 mm,the EAB of Hs-Mo2C composite was 7.92 GHz.(3)Using MoO3 nanorods synthesized by hydrothermal method as template,one-dimensional hollow molybdenum-polydopamine precursor was obtained by in-situ polymerization and etching of dopamine,and Mo2C@C nanotubes(NTMo2C)were synthesized by carbonization at high temperature,which were composed of carbon nanosheets embedded with ultrafine Mo2C particles.By adjusting the amount of MoO3 template agent,the number of nanotubes in NTMo2C composite can be adjusted to the microstructure,so as to achieve the regulation of microwave absorption properties.The NT-Mo2C composite has good absorption capacity for MoO3 content of 100mg and EAB of 9.36 GHz for suitable thickness of 3.4 mm. |
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