Fabrication And Terahertz Absorption Properties Of Flexible Porous Conductive Materials

Terahertz(THz)wave refers to the electromagnetic wave with the frequency between 0.1 and 10 THz.It has the advantages of microwave and infrared because of its unique spectral position.At present,it has a wide application prospect in the fields of non-contact imaging,safety inspection,wireless communication and so on.Therefore,the research and development of THz absorber and THz modulator with high performance is particularly important.In the research of THz devices,functional materials play an irreplaceable role,which determines the transmission,reflection and absorption properties of THz waves.In this paper,two kinds of flexible porous conductive materials were prepared from the perspective of materials,and their THz absorption properties were studied,focusing on the "structure-activity" relationship between the physical and chemical structure of the materials and THz absorption properties.The main research contents and conclusions are as follows:Flexible,efficient and broadband THz absorber based on carbonized sponge:Using cheap commercial sponge as raw material,a flexible porous carbonated sponge was prepared by adjusting the calcination temperature through anaerobic high-temperature calcination.The surface morphology and microstructure of the material were characterized by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),thermogravimetric analysis(TGA)and Raman spectroscopy.The experimental results show that the sample still retains the flexible,lightweight and three-dimensional pore structure characteristics of the original sponge after high temperature calcination.With the increase of calcination temperature,the graphitization degree and conductivity of the samples increased.The THz shielding and stealth properties of the samples were tested.The test results show that the THz stealth and shielding properties of the samples gradually increase with the increase of calcination temperature.When the thickness is 6 mm and the calcination temperature reaches 900 ℃,the shielding efficiency reaches the highest value(49 d B,～ 99.999%),the maximum reflection loss(RL)can reach 47 d B,and the effective spectrum range is between 0.2 and 3.5 THz,which is better than most reported carbon materials.When the calcination temperature reaches 1000 ℃,the reflection of THz wave on the sample surface is enhanced due to the problem of impedance matching,which is not conducive to the application of THz stealth.Humidity THz modulation characteristics of carbonated phytic acid loaded sponge composite: Using phytic acid containing more phosphate as raw material,carbonized phytic acid with different phosphate content was prepared by adjusting the calcination temperature through high-temperature calcination,and loaded in melamine sponge to prepare carbonized phytic acid @ sponge composite.The structure and properties of carbonated phytic acid and its composites were characterized by SEM,EDS,TGA,infrared and zeta potential.The experimental results showed that with the increase of carbonization degree,the graphitization degree of carbonized phytic acid deepened and the content of phytate decreased gradually.When the calcination temperature is higher than 500 ℃,the carbonized phytic acid becomes a conductor.Carbonated phytic acid loaded on the sponge network structure did not change the pore size of the sponge.The effect of humidity on THz absorption properties of composites was studied by changing ambient humidity.The experimental results show that in the dry state,due to the high-temperature calcination,the conductivity of the material is improved,and the absorption strength of carbonated phytic acid loaded sponge composite to THz wave increases gradually;In the humidity environment,due to the ionization of phosphate on the surface of carbonized phytic acid,the conductivity of carbonized phytic acid obtained by low-temperature calcination increases,and the THz transmission and reflectivity decrease significantly;However,the surface of carbonized materials calcined at high temperature contains almost no functional groups that are easy to ionize,so there is almost no significant change in THz transmission and reflectivity.