Research On The Absorption Properties Of Two-dimensional Layered MXene-based Composites With Heterogeneous Structures

The problem of electromagnetic radiation is becoming more and more serious with the frequent use of electronic equipment,therefore,a"wide,light,thin,strong"electromagnetic wave absorbing material came into being,the two measurement standards of electromagnetic wave absorption material are minimum reflection loss(RL_min)and effective absorption bandwidth（EAB）.By designing them as core-shell structures of different sizes,porous flower-like structures,interfacial polarization,conduction networks,magnetic coupling,and dielectric synergistic double loss,the absorption performance of electromagnetic waves can be significantly improved.Due to its unique properties,MXene（transition metal carbides,nitrides,and carbonitrides）has become a rising star in the 2D material family.Although the main research interest is still focused on the original MXene and its composites,a lot of attention has also been paid to MXene with different compositions in recent years.Absorbing materials are expected to meet the performance requirements of the service environment.Taking the structure and composition design and regulation of Ti₃C₂T_x MXene-based nanocomposites as the starting point,MXene-based composite absorbing materials with different microstructures and multiple components were prepared by hydrochloric acid and lithium fluoride to generate hydrofluoric acid in situ etching parent phase Ti₃Al C₂ MAX（ternary layered nanomaterials）precursors,simple one-step solvothermal solvent heating,low-temperature freeze-drying,and high-temperature calcination under an inert atmosphere.This study will help guide the design of future high-performance MXene.The main research contents are as follows:（1）In order to solve the problem that the absorption band of absorbing materials is too narrow,this paper prepares accordion-like Ni Co/Ce O₂/Ti₃C₂T_x nanocomposite absorbing materials by heat treatment in a reducing gas H₂/Ar atmosphere by designing an accordion-like multilayer MXene structure,introducing a variety of loss mechanisms under the premise of retaining the special structure,and using a simple one-step hydrothermal synthesis method.By adjusting the Ce O₂ load,the influence of different feeding ratios on the morphology of the microstructure was explored.When the addition amount is 0.1 mmol,the Ni Co/Ce O₂/Ti₃C₂T_x composites exhibit the best broadband absorption performance,with a minimum reflection loss of-42.48 d B at a thickness of 2.0 mm.The corresponding EAB at1.9 mm is 6.32 GHz.（2）In order to achieve the goal of lightweight absorbing materials,the strategy of combining Fe-based metal-organic frameworks（Fe-MOFs）with porous structures with single-layer MXene materials was adopted to synthesize core-shell layered double hydroxide（Ni Fe-LDH）nanocages with core-shell structure by the one-pot self-template method.MIL-88A@Ni Fe-LDH@Ti₃C₂T_x composite materials are obtained by electrostatic self-assembly by magnetic stirring.The final sample is prepared by varying the concentration of the Ti₃C₂T_x supernatant.Among them,the composite performance was best when the concentration of Ti₃C₂T_x supernatant was 1.0.The optimal reflection loss value is-46.7 d B at a thickness of 1.4 mm,and its maximum EAB is 5.12 GHz at a thickness of 1.8 mm.This method of compounding monolayer MXene with MOFs derivatives also provides a new strategy for the development of ultra-lightweight broadband absorbing materials.（3）In order to realize the problem of the thin thickness of absorbing materials,and obtain better absorbing materials,Co/Zn O nanospheres are compounded with multi-walled carbon nanotubes,and then coated with a single layer of MXene.In this study,the mechanisms of magnetic loss and dielectric loss were introduced,and Co/Zn O@CMWCNTs/Ti₃C₂T_x samples with three-dimensional flower-like porous microstructures were synthesized by two-step hydrothermal method and then calcined to obtain Co/Ti₃C₂T_x samples.The influence of carboxylated multi-walled carbon nanotubes（CMWCNTs）and monolayer Ti₃C₂T_x on microstructure morphology and absorption performance was studied.The results show that by adjusting the loading amount of single-layer Ti₃C₂T_x,the purpose of effective regulation of the electromagnetic parameters of the sample is achieved.When the load of single-layer Ti₃C₂T_x is 3 mg,the lowest reflection loss of the composite is-46 d B,and the EAB is 4 GHz,and the corresponding thickness is only 1.5 mm.The regulation of composite components and morphology realizes the adjustment of absorbing performance,which provides a reference for the preparation of lightweight multifunctional absorbing materials.