Study On The Electromagnetic Wave Absorption Performance Of Ti₃C₂T_x-MXene And Their Composites

MXenes are a new class of two-dimensional materials,which have high specific surface area,rich surface functional groups,high electrical conductivity and unique multi-layer structure.Because of its unique structure and properties,MXenes have been widely used in the fields of batteries,supercapacitors,catalysis,etc.,and it also shows great potential in the field of electromagnetic absorption.Based on the excellent electrochemical properties and surface properties of MXenes,it is possible to modify the surface of MXenes and synthesize related composites.However,these new materials also have problems such as impedance mismatch and less of effective absorption bandwidth when used as electromagnetic wave absorption materials.Unsolved these problems,to better improve the electromagnetic wave absorption efficiency of the materials,the synthesis of composites based on MXenes is a reasonable solution.In this paper,we selected Ti₃C₂T_x-MXene as the research object.And on this basis,surface modification and modification and composite with different materials are tried on the Ti₃C₂T_x-MXene.The structure and components of surface modified Ti₃C₂T_x-MXene and its composites were studied,and the electromagnetic wave absorption properties and absorbing mechanism of these materials were analyzed and discussed.Specific research contents and results are as follows:（1）Lithium fluoride（LiF）and hydrochloric acid solution were used as etching solution to etch Ti₃Al C₂ precursors.The effects of different etching temperatures on the morphology of Ti₃C₂T_x-MXene were compared under the condition that the etching solution concentration and etching time were fixed,and the optimal etching process was determined by comparison:The mixed solution of 9 mol/L hydrochloric acid and LiF was used as the etching solution at 55℃for 24 h.After the etching process was determined,the surface of Ti₃C₂T_x-MXene was modified,and the surface of Ti₃C₂T_x-MXene was doped with cerium by a simple one-step hydrothermal method to form Ti₃C₂T_x-MXene/CeO₂ composites.The effects of the hydrothermal reaction time and the amount of MXene on the electromagnetic wave absorption properties of the composite and the microwave absorption mechanism of the composite were also discussed.When the mass ratio of MXene to Ce（NO₃）₃·6H2O is1:3,the sample obtained by hydrothermal reaction at 180℃for 6 h has the best electromagnetic absorption performance.The lowest reflection loss(RL_min)-43.38 d B can be obtained at 2.8 mm,and the effective absorption bandwidth（EAB,When RL<-10 d B,90%of electromagnetic wave can be absorbed）at 2.4 mm can reach to 5.44 GHz（11.28～16.72 GHz）.（2）The accordion-like Ti₃C₂T_x-MXene with large layer spacing was prepared by intercalation method,and Ti O₂particles were grown on the surface of the material without the addition of titanium source.Finally,the polyaniline was grown by in-situ polymerization on the surface of the material to obtain the Ti₃C₂T_x/Ti O₂/PANI composite with sandwich structure.Due to the existence of Ti O₂ particles and PANI polymer on the surface of Ti₃C₂T_x/Ti O₂/PANI composite,abundant heterojunctions are formed and the electromagnetic wave absorption performance is excellent.It can obtain the RLmin value of-65.61 d B at the matching thickness of 2.18 mm and the frequency of 13.92 GHz,and it can obtain the effective absorption bandwidth of up to 5.92 GHz（11.84～17.76 GHz）at the matching thickness of 2.10 mm.（3）Ti₃C₂T_x-Mxene with large size and few layers was prepared by hydrofluoric acid as etching agent.NiCo-LDH with flower shape was prepared by simple one-step hydrothermal method,and the NiCo-LDH/MXene composite was prepared by the solution aging and deposition method.The effects of the Ti₃C₂T_x-Mxene content in NiCo-LDH/MXene composites on the morphology and electromagnetic wave properties of the composite samples were discussed.When the Ti₃C₂T_x-Mxene load is 75 wt%,the NiCo-LDH/MXene composite can obtain the lowest reflection loss of-64.24 d B at 12.0 GHz frequency and 2.18 mm at 2.00 mm.The NiCo-LDH/MXene sample can obtain the maximum effective absorption bandwidth of 4.48 GHz（11.04～15.52 GHz）.