Preparation Of MXene-based Composites And Their Absorbing Properties

The development and popularity of communication electronic devices with the continuous innovation of mobile communication technology has brought convenience to people's production and life.However,the resulting electromagnetic radiation not only seriously interferes with the normal operation of electronic equipment and human health,but also greatly reduces the survivability of weapons and threatens military security.Electromagnetic wave absorbing materials can effectively attenuate electromagnetic radiation and thus receive wide attention from all walks of life.Two-dimensional transition metal carbides or nitrides(MXenes)are lamellar substances formed by etching metal intercalations in the MAX phase.MXene is favored by researchers for its unique structure,abundant surface terminations,excellent electrical conductivity,large specific surface area,and metal-like properties.The composite of MXene as the base material with magnetic particles,conductive polymers,porous carbon and semiconductors can give full play to the loss mechanism of each material to improve the impedance matching characteristics and enhance the attenuation capability.In this paper,the absorbing properties and mechanisms of different component composite absorbing materials were investigated by changing the structure of MXene and the types of complexes.The main research contents and conclusions are as follows:(1)The Ti₃AlC₂was etched in situ using lithium fluoride and hydrochloric acid solution to obtain a few layers of Ti₃C₂T_x,while a series of Ni Co₂O₄was prepared by changing the calcination temperature under air atmosphere,and finally the two substances were compounded by electrostatic self-assembly,and the effects of different composite morphologies,defects and magnetic properties on their electromagnetic parameters were investigated.The crystal structure,microscopic morphology and defects of the material were characterized by X-ray diffraction technique,scanning and transmission electron microscopy,micro confocal Raman spectroscopy,etc.It was found that with the increase of calcination temperature,the size of spherical Ni Co₂O₄changed slightly and some of the spheres were broken,and the dielectric properties of the material decreased.The minimum reflection loss of the composite was-43.52 d B at a calcination temperature of400°C,and the effective absorption bandwidth was 2.4 GHz,which corresponded to a thickness of 2.0 mm.(2)The accordion-like Ti₃C₂T_xwas obtained by etching Ti₃AlC₂with hydrofluoric acid solution.Co₉S₈/C/Ti₃C₂T_xcomposites were prepared by hydrothermal method and heat treatment process.The dielectric loss capability of the composites was enhanced by the introduction of Co₉S₈and carbon.The addition amount of Ti₃C₂T_xwas further adjusted and the effects of different throw-in ratios on the electromagnetic parameters were investigated.Based on the above characterization and measurement,the composite maintained a typical accordion-like shape,and the dielectric properties of the composite increased and then decreased with the increase of Ti₃C₂T_xincorporation,and the Co₉S₈/C/Ti₃C₂T_xcomposite exhibited the best absorption performance when its incorporation amount was 100 mg,and the lowest reflection loss was-50.07 d B at the thickness of 2.51 mm and the corresponding effective absorption bandwidth is 4.24 GHz.The enhancement of dielectric loss,the tuning of electromagnetic parameters and the optimization of impedance matching improved the absorption performance of Co₉S₈/C/Ti₃C₂T_xcomposites.(3)The ZIF-67 particles were grown on accordion Ti₃C₂T_xby aging process under room temperature conditions,and then Ni Co LDH/Ti₃C₂T_xwas synthesized by one-step hydrothermal method,followed by selenization in argon atmosphere to obtain Ni Se₂-Co Se₂@C/Ti₃C₂T_xcomposites.Based on the study of the dielectric properties on the wave absorption properties,the introduction of transition metal selenides with low intrinsic conductivity was proposed to modulate the dielectric properties of Ti₃C₂T_x.The characterization test results demonstrate that the transition metal selenides are anchored on the Ti₃C₂T_xlamellae and the composite structure is stable and maintains an accordion-like multilayer structure.With the introduction of transition metal selenides,the problem of excessive dielectric constant of pure Ti₃C₂T_xmaterial is improved,the impedance matching property of the material is improved,and the effective bandwidth of the absorber material is broadened.The strongest reflection loss value at 10.32 GHz is-60.46 d B,and the expanded effective bandwidth is up to 5.68 GHz.This paper presents a composite of magnetic metal,transition metal sulfide and ZIF-67-derived selenide with the intrinsic properties of Ti₃C₂T_xto obtain a composite material with exceptional electromagnetic wave absorption properties.By changing the morphology,components,dielectric properties and loss mechanisms of the composites,the impedance characteristics and absorbing properties of the composites can be adjusted to obtain efficient electromagnetic wave absorbers.