Porous Carbon Composites Derived From Heterobimetallic (Zn, Co) MOFs For Electromagnetic Wave Absorptio

Nowadays,with the continuous development of radio communication technology and radar technology in the military industry,electromagnetic waves play an important role in all aspects of our lives,but at the same time,they also bring serious electromagnetic pollution.Electromagnetic waves will not only reduce the service life of the equipment itself,but also cause damage to human health.Therefore,the development of high-quality electromagnetic wave absorption materials is particularly important,in practice,high-quality absorbing materials in addition to the requirements of the absorption band,but also has a light weight,thin thickness and other characteristics,which requires both excellent absorption performance and impedance matching performance,a single absorption mechanism of the material is often difficult to meet the above requirements.In this thesis,metal organic frameworks（MOFs）are used as excellent precursors for the preparation of magnetic carbon-based materials,and two-dimensional heterogeneous bimetallic（Zn,Co）MOFs are compounded with other dielectric or magnetic materials,and the parameters are adjusted to build the ideal absorbing materials with rich structure and absorption mechanism,good impedance matching and comprehensive performance.The main research contents and conclusions are as follows.（1）Co/Zn O/Ti₃C₂T_x was successfully grown on layered Ti₃C₂T_x based on a two-dimensional heterogeneous bimetallic（Zn,Co）MOF by an aqueous phase self-assembly process,and Co/Zn O/Ti₃C₂T_x was successfully prepared by a subsequent annealing process.The effect of carbonisation temperature on the microwave absorption properties of the composites was investigated in detail.With the change of temperature,the components and morphology of the products changed accordingly and influenced the electromagnetic wave absorption properties.The best reflection loss at 2.4 mm is up to-44.22 d B at an annealing temperature of 750°C,with a maximum effective absorption bandwidth of 5.28 GHz.Multiple interfacial polarisations can be generated between Co₃Fe₇,Zn O and the porous carbon framework in the material.（2）Fe₂O₃@Zn Co-MOF composites were prepared by an aqueous phase self-assembly process and Co₃Fe₇@Zn O@C nanocomposites were obtained by a subsequent annealing process.By varying the loading of Fe₂O₃ during the synthesis process,a series of composites were obtained.Among them,Co₃Fe₇@Zn O@C has the best electromagnetic wave absorption performance when the loading of Fe₂O₃ is 0.1 g.The reflection loss can reach-40.63 d B at a thickness of 2.2 mm,and the maximum effective absorption bandwidth is 5.84 GHz at a thickness of 2.4 mm.where Co₃Fe₇,Zn O and the porous in the material Multiple interfacial polarisations can be generated between the carbon framework,the open holes obtained by the MOF pyrolysis allow multiple reflections and scattering of incident electromagnetic waves,and the Co₃Fe₇ magnetic nanoparticles cause magnetic loss in the material.The abundant absorption mechanism makes Co₃Fe₇@Zn O@C a good absorber of electromagnetic waves.（3）Zn Co-MOF@MWCNTs（MOF@M）were obtained by compounding MWCNTs with heterobimetallic（Zn,Co）MOF through an in-situ growth process via an aqueous phase self-assembly process,and through a subsequent pyrolysis process to Co/Zn O/C@MWCNTs（CZC@M）composites,when the mass ratio of MWCNTs in the composites was changed,the dielectric constant of the products could be adjusted,thus changing the impedance matching and properties.The results show that multi-walled carbon nanotubes are uniformly distributed onto the surface of Co/Zn O/C,and the multi-component synergistic effect makes CZC@M have good electromagnetic wave absorption performance,and the reflection loss value of sample CZC@M-50 is-41.75 d B at a thickness of 2.4 mm and the maximum bandwidth is 4.72 GHz at a thickness of 2.2 mm at a sample to paraffin ratio of 1:9.In this thesis,we start from heterobimetallic（Zn,Co）MOF,compound it with different dielectric,or magnetic materials using aqueous-phase self-assembly and annealing processes,change the components of the composites,and also control the experimental conditions（addition amount,weight percentage,annealing temperature,etc.）during the reaction process to study the effects of different construction strategies on the morphological structure and wave absorption properties of the materials,and regulate the impedance matching and attenuation constants of the materials to obtain high-quality and efficient electromagnetic wave absorption properties.