Preparation And Properties Of Magnetic Carbon-based Microwave Absorbers Derived From MOFs

In recent years,in order to meet the requirements of"strong,wide,thin and light"microwave absorbers,magnetic carbon-based absorbing materials have attracted a lot of attention.Because of the advantages of easy preparation method and controllable structure of material composition,the magnetic carbon matrix composites derived from MOFs have a promising application.In this thesis work,the main research contents and results are as follows:（1）NiCo-BTC was synthesized by a simple hydrothermal method,followed by polymerization of dopamine on its surface to produce NiCo-BTC@PDA core-shell nanospheres as precursors,and then calcined in an inert atmosphere to obtain NiCo@C-X composites with a unique bilayer core-shell structure.The"double-layer"design concept,the unique core-shell structure and the regulation of the relative carbon content allow NiCo@C-0.75 to exhibit excellent wave absorption performance.When the matched thickness is 2.2 mm,the effective absorption bandwidth reaches 4.8 GHz.the maximum reflection loss reaches-53.28 d B at 7.1 GHz,and the material packing ratio is only 20 wt%,which has a high potential for practical applications,and the material RCS simulation results also prove this conclusion.（2）On the basis of NiCo@C-0.75,we have explored the carbonization temperature.The NCB@PDA-T composites were obtained by calcining NiCo-BTC@PDA at different temperatures.At T=750°C,the material has the maximum reflection loss value of-55.93 d B,the smallest matched thickness of1.8 mm,and the widest effective absorption band width of 5.6 GHz,achieving both strong and broadband absorption at a packing ratio of only 20 wt%.In addition,NCB@PDA-700 and NCB@PDA-800 also have excellent absorption performance,reaching-53.28 d B（4.8 GHz）and-50.82 d B（4.8 GHz）,respectively,thanks to the unique core-shell structure formed after calcination,which allows multiple reflection and scattering of electromagnetic waves,and the high graphitization of the material,which facilitates electron transport.For this type of absorber,700 to 800 degrees Celsius may be a better carbonization temperature.（3）To further improve the material absorption performance,NCM:NiCo@C@Mo S₂ composites with graded heterogeneous structure were constructed on the basis of NCB@PDA-750 by synergizing NiCo@C core-shell structure and Mo S₂ three-dimensional porous mesh structure.The NCM has the best absorption performance with the maximum reflection loss value of-57.09 d B and the effective absorption bandwidth of 5.6 GHz at the filler ratio of40 wt%,and the bandwidth of NCM-50 wt%composite is even 6.0 GHz.The absorption performance of NCM is better than that of NCB@PDA-750,which also proves that the synergistically constructed graded heterogeneous structure is effective in improving the The NCM is better than the NCB@PDA-750 in terms of absorption performance,which also proves that the hierarchical heterostructure constructed in concert can effectively improve the polarization loss capability of the composites,thus achieving broadband absorption and strong absorption of NCM composites.