Study On Wideband Electromagnetic Wave Absorbing Properties And Mechanisms Of Cobalt-Based Metal-Organic Framework-Derived Materials

With the rapid progress and iteration of information technology,technologies such as big data,cloud computing,artificial intelligence,the Internet of Vehicles,and the industrial Internet have profoundly improved the human living environment.The widespread use of these technologies will sharply increase the electromagnetic radiation in space.In order to solve this problem,electromagnetic wave absorbers have emerged.Metal-Organic Framework(MOF)-derived composites are a common type of absorbers.However,the effective absorbing bandwidth(EAB)of such materials is currently narrow,greatly limiting their application scenarios and development potential.In order to achieve the goal of broadband electromagnetic wave absorption,this dissertation uses simple solvothermal method and high-temperature annealing method as preparation means,through physical property characterization,microscopic morphology observation,electromagnetic parameters and electromagnetic wave absorption performance analysis and other methods,combined with electromagnetic simulation,comprehensively evaluated the materials,designed and prepared cobalt based MOF-derived composite electromagnetic wave absorbers with ultrawide EAB,high saturation magnetization and anti-microbiologically influenced corrosion performance,and analyzed the relationship among physical properties,microstructures,and absorption performances and mechanisms.The main results are as follows:1.For the purpose of wide EAB,cobalt-based MOF-derived composites with rodshaped structures of surface modified nanoparticles were prepared.The maximum EAB can reach up to 6.7 GHz with the corresponding matching thickness only 2.2 mm,which is greater than the EAB of similar composites.The unique rod-shaped microstructure can provide a large number of cobalt/carbon heterogeneous interfaces for the composites,which can effectively enhance the polarization phenomenon,further increasing the dielectric loss.In addition,the composite has strong magnetic loss ability.The successful preparation of cobalt-based MOF-derived composites with ultrawide EAB can significantly improve the upper limit of absorption performance of similar materials.2.Cobalt-based MOF-derived composites with layered porous microstructure modified with cobalt nanoparticles have been prepared by solvothermal and hightemperature annealing methods.The saturation magnetization is far higher than other similar materials reported.The higher magnetization of the material helps balance the magnetic loss and dielectric loss,further improve the electromagnetic matching degree,and increase the EAB of the material to 6.9 GHz,Additionally,the minimum reflection loss has been optimized to-32.92 dB.Therefore,increasing the saturation magnetization is an effective way to improve the electromagnetic wave absorption performance.3.When absorbers are applied in marine environments,they should have bifunctional properties of resistance to microbiologically influenced corrosion and electromagnetic wave absorption performance.A series of cobalt-based MOF-derived composites with self-assembled hollow porous bowl like structures were designed and prepared for the purpose of bifunction.Their EAB is still as high as 6.8 GHz,and their minimum reflection loss is significantly improved to-52.66 dB.The excellent absorption performance of the composites is mainly attributed to their ideal electromagnetic matching.Through electromagnetic simulation,it has been confirmed that composite materials have excellent radar wave attenuation characteristics in all incident directions.In addition,the antibacterial and electrochemical impedance spectroscopy tests have demonstrated the anti-microbiologically influenced corrosion performance of the composites.The composites are helpful for the development and exploration of dual functional absorbing materials.