Ultra Wideband Terahertz Absorbing Material With Gradient Structure

In recent years,the rapid development of terahertz technology has aroused wide attention in the world,and the research on terahertz has been further deepened.Terahertz wave has excellent properties such as strong penetration,low photon energy,wide frequency band and high imaging resolution,which make it show a very wide application prospect in 6G communication,medical application,security inspection military field,atmospheric remote sensing and radio astronomy.At the same time,the demand for high performance terahertz absorbing materials is increasing day by day.However,most of the existing terahertz absorbing materials have one or more problems such as complex process,limited absorption performance,poor structural stability,and limited thinness.Therefore,it is of great significance to study the wide band,high absorption,thin and stable structure of terahertz absorbing materials.Based on the above background,this thesis develops a wideband terahertz wave absorbing material with gradient structure based on MXene material.The specific research results are as follows:Firstly,the preparation and characterization of two dimensional transition metal carbide MXene were studied.The MXene precursor MAX was selectively etched with acid etching solution,and various MXene products were obtained through centrifugation,freeze-drying,intercalation and filtration.The characterization results of each MXene were obtained by XRD,SEM and other tests,which confirmed that we successfully obtained Ti₃C₂and V₂C main preparation technology.The conductivity of Ti₃C₂is up to 3703.70 S/cm,which proves that Ti₃C₂is an excellent conductive material.Secondly,the corresponding absorbent materials for thin films were prepared by filtration and drying using Ti₃C₂and/or WPU dispersions.Terahertz time-domain spectroscopy system was used to test the terahertz absorption rate of each thin film.The absorption rate of pure Ti₃C₂thin film is poor,only 10%～20%in the test band of0.3～1.2 THz,while the absorption rate of Ti₃C₂-WPU mixed thin film is more than 90%,and has the characteristics of soft,flexible and thin structure.In this chapter,it is confirmed that the absorption effect of Ti₃C₂with a single component is poor,but the material with excellent structural strength and absorption effect can be obtained by combining with other substances.Then,Ti₃C₂was combined with soft fabric by soaking method,and a textured wave absorber（MCF）based on Ti₃C₂was prepared.This fabric absorbing material has the advantages of light weight,thin thickness,high flexibility,strong absorption performance,simple preparation process and low manufacturing cost.Meanwhile,by comparing the concentration gradients of Ti₃C₂with different fabric substrates,it is found that in the test frequency band of 0.3～1.2 THz,MCF with gauze-thick as the skeleton and Ti₃C₂concentration gradient of 1mg/m L has the strongest absorption efficiency,and the absorption rate is greater than 95.5%,and that of 0.32 THZ band is greater than 99%.In this chapter,it is proved that MCF is a kind of material with strong absorption performance,and it is proved that MCF with a single gradient cannot take into account impedance matching and attenuation characteristics.Finally,in order to further improve the absorption effect of MCF,we built a gradient multilayer structure with different concentrations of MCF on the basis of previous work,and used WPU as the binder and protective layer.WPU greatly enhanced the adhesion ability of Ti₃C₂and greatly improved the application stability of the material.The structure achieves the compatibility of impedance matching and attenuation characteristics.The structure with the gauze-thick as the skeleton and the MCF with the concentration gradient of 0,1,4 mg/m L from top to bottom has the best absorption effect,and the absorption rate is higher than 98.5%in the frequency band of0.3～1.2 THz.At the same time,the absorption rate of 0.88 THz band is greater than99%,and that of 0.22 THz band is greater than 99.9%,which effectively proves that the absorption capacity of multilayer structure is much stronger than that of single-layer structure.