Design And Electromagnetic Wave Absorption Properties Of Two-dimensional Ti₃C₂T_x-based Composites

With the rapid development of electronic information technology and military technology,various types of electronic communication equipment and electromagnetic products have gradually occupied human's daily lives.The resulting electromagnetic pollution and electromagnetic interference have attracted more attention from researchers.Electromagnetic wave absorbing materials are of great significance in improving the living environment,maintaining national defense security,and preventing information leakage.Therefore,the researchers make every effort to explore"thin,light,wide,strong"and corrosion-resistant,high-temperature-resistant and good mechanical properties of electromagnetic wave absorbing materials.Ti₃C₂T_x has a unique two-dimensional layered structure,good electrical conductivity,large specific surface area,good dielectric properties and excellent mechanical properties,which is widely applied in the field of absorbing materials.This paper prepared good delaminated two-dimensional layered Ti₃C₂T_x firstly,and then compounded it with other materials by hydrothermal method,heat treatment and other processes.The microstructure and phase composition of the sample were regulated,and the nucleation mechanism of the material was explained.Furthermore,the influence of sample morphology and phase composition on the absorbing properties of materials was studied,and the mechanism of electromagnetic wave absorption of composite materials was explained.The specific research content is as follows:?1?The two-dimensional Ti₃C₂T_x with thin layers and good delamination effect is prepared by changing the etching time of Ti₃Al C₂ in HF solution and combined with freeze-drying technology.Furthermore,layered Ti₃C₂T_x/Ni-spheres composites with various microstructures was prepared by hydrothermal method at 140?for 10 hours,and the growth mechanism of Ni-spheres on the surface and interlayer nucleation of Ti₃C₂T_x was explained.Compared with the pure layered Ti₃C₂T_x and single Ni-spheres,the layered Ti₃C₂T_x/Ni-spheres composites possess excellent electromagnetic wave absorption performance,the minimum reflection loss?RL?value of sample S2 reach-47.06 d B at the frequency of 12.4 GHz,and the effective absorption bandwidth is 3.6 GHz?10.8-14.4 GHz?when the coating thickness of the absorber is 1.5 mm.This is due to the unique two-dimensional structure of Ti₃C₂T_x,good electrical conductivity,dipole polarization,interfacial polarization,and synergistic enhancement effects between dielectric loss and magnetic loss.?2?The Ti₃C₂T_x/Ni-spheres/Ti O₂ nanocomposite was obtained by heat-treating the two-dimensional layered Ti₃C₂T_x/Ni-spheres composite at different temperatures?300?,400?and 500??.The samples analysis of SEM,XRD,and XPS revealed that the microstructure and phase composition changed with the increase of the heat treatment temperature,which was mainly due to the oxidation of Ti₃C₂T_x.Based on the study of the electromagnetic wave absorption properties of Ti₃C₂T_x/Ni-spheres/Ti O₂ nanocomposite,it was found that sample S-300 showed excellent electromagnetic wave absorption performance.The minimum reflection loss?RL?value of sample S-300 is-35.2 d B at f=17.5 GHz.Its effective absorbing bandwidth is>1.7 GHz with the 1.5mm coating thickness of the absorber.This is results from the good impedance matching ratio,the excellent electromagnetic wave absorption loss mechanism and the synergy between the dielectric loss and the magnetic loss of the sample S-300.This shows that the electromagnetic wave absorption properties of the Ti₃C₂T_x/Ni-spheres/Ti O₂ nanocomposite can be adjusted by controlling the phase composition and microstructure of the material.?3?A two-dimensional Ti₃C₂T_x/Ni-sheets composite was prepared by controlling relevant experimental parameters.With the increase of the content of flaky Ni,they are connected to each other to form a network structure,which can increase the conductive path of the sample.This is beneficial to the formation of micro-current,which facilitate enhancing the attenuation of electromagnetic waves.However,the connection of the mesh structure is strengthened,which will increase the reflection of electromagnetic waves on the surface and reduce the impedance matching ratio of the material.Analysis the electromagnetic wave absorption performance of the sample found that the minimum reflection loss?RL?value of Ti₃C₂T_x/Ni-sheets composite can reach-41.84 d B at the frequency of 14.6 GHz,the corresponding absorbing coating thickness is 1.3 mm,and the bandwidth of RL<-10 d B It can be controlled in the bandwidth of 3.5-16.8 GHz by adjusting the thickness of the absorber?1.0-3.0mm?.Therefore,this structure-controllable Ti₃C₂T_x/Ni-sheets composite will be candidates in lightweight and efficient electromagnetic wave absorbing materials.In summary,the electromagnetic wave absorption performance of two-dimensional layered Ti₃C₂T_x and its composite materials can be controlled by adjusting the microstructure and phase composition.Therefore,this thesis provides theoretical guidance for designing excellent electromagnetic wave absorbing materials.