Research On The Preparation And Electromagnetic Wave Absorbing Properties Of MXene And Its Composites

In recent years,electromagnetic wave as an important carrier has been widely used in various fields,which has greatly promoted the progress of the society.However,the problem of electromagnetic pollution is getting worse.Electromagnetic pollution will have adverse effects on the normal operation of electronic instruments and human health.Electromagnetic wave absorbing materials can effectively absorb electromagnetic waves by converting them into heat energy or other forms of energy.Therefore,devolping high-performance electromagnetic absorbing materials with the characteristics of“wide,thin,strong and light”is of great significance to reduce electromagnetic pollution.With strong attenuation ability of electromagnetic wave,two-dimensional materials are one of the most competitive and promising electromagnetic absorbing materials.MXene is a typical representative of them.MXene is a new carbon/nitride material with multi-layer structure,large specific surface area,good electrical properties.It has great potential in the field of electromagnetic wave absorbing materials.The fabrication,cold sintering and electromagnetic wave absorbing properties of MXene and its composites were studied in this paper.The main contents and conclusions of this paper are as follows:1.The multilayer Ti₃C₂T_x Mxene was successfully prepared by HF etching method by selectively stripping Al atomic layers from Ti₃Al C₂.The electromagnetic wave absorbing properties of Ti₃C₂T_x Mxene with different filling amounts were studied.When the filling amount of Ti₃C₂T_x Mxene was 30 wt%,the excellent electromagnetic wave absorbing properties were obtained.When the matched thickness is 2.0 mm and the frequency is 12.72 GHz,the peak value of reflection loss of Ti₃C₂T_x Mxene is-27.15 d B,and the effective absorption bandwidth is 7.12 GHz.When the addition amount of Ti₃C₂T_X MXene was up to 50 wt%,the performance was significantly reduced.Within the test thickness range of 1-5 mm,the reflection loss RL values are all between 0 and-6d B,and the absorption intensity of electromagnetic wave is weak.A good impedance matching of Ti₃C₂T_x MXene can be achieved under the low filling amount.The unique layered structure,strong conductivity loss,dipole polarization and interface polarization of Ti₃C₂T_x MXene are conducive to absorbing electromagnetic waves.Due to the high dielectric constant of Ti₃C₂T_x MXene,and the increase of filling amount will cause impedance mismatch,resulting in poor wave absorption effect.2.To further improve the electromagnetic wave absorbing performance of Ti₃C₂T_xMXene,composite modifiedwith low dielectric Zn O is a good option.The sandwiched Ti₃C₂T_x MXene/Zn O composites were prepared by solvo-thermal method,and the nucleation and growth of Zn O on the surface and between layers of Ti₃C₂T_x MXene.The MZ-1,MZ-2 and MZ-3 materials have achieved excellent absorbing properties under the filling amount of 50 wt%.When the thickness of MZ-1 is 1.5 mm,the minimum RL value at 18 GHz is-21.02d B,and the effective absorption bandwidth is 7.28 GHz.When the thickness is 2.0 mm and at 9.12GHz,the minimum RL value is-42.0 d B,and the effective absorption bandwidth is 2.72 GHz.The effective bandwidth is 6.4 GHz when the thickness of MZ-2 is 1.5 mm,and the minimum RL is-18.32 d B at the frequency of 14.32 GHz.When the sample thickness was 4.0 mm,the effective bandwidth was 1.52 GHz,and the minimum RL was-41.84 d B at the frequency of 4.4 GHz.When the thickness of MZ-3 is 1.5 mm and the frequency is 11.68 GHz,the RL reaches-30.20 d B,and the effective absorption bandwidth is 5.2 GHz.The excellent absorbing properties of Ti₃C₂T_x MXene/Zn O composites can be attributed to good impedance matching,enhanced interfacial polarization and unique sandwich structure after modification.3.Structural absorbing materials were prepared by cold sintering of pure Ti₃C₂T_xMXene and its composites,and 1M acetic acid solution as transient liquid phase.The prepared Ti₃C₂T_x MXene with lots of functional groups has a hydrophilic surface,and Zn O is soluble in acid solution,which is conducive to cold sintering.The results show that Ti₃C₂T_x MXene and its complex formed dense blocks after cold sintering,and the lamellae of Ti₃C₂T_x MXene are closely bonded together,but the lamellae are still visible.When the thickness is 5.5 mm and the frequency is 3.44 GHz,the peak value of reflection loss absorption is-14.99 d B,and the effective absorption band is 0.48 GHz.The MZ-2has achieved excellent absorbing performance at low frequency,with a minimum RL of-15.30 d B at a frequency of 4.32 GHz,an effective bandwidth of 0.96 GHz and a thickness of 4.0 mm.The filling amount of absorbing agent in cold sintered samples is 100 wt%.The tight structure between Ti₃C₂T_x MXene layers is easy to form a conductive network,which increases the electrical conductivity of the material and causes impedance mismatch.The above reasons lead to low absorption intensity of electromagnetic wave and narrow effective absorption band.