Study On Nb₂CT_X MXene Based Microwave Absorbing Composites Prepared By Cold Sintering

Absorbing materials can directly dissipate most of the electromagnetic waves inside the material,and have broad application prospects in reducing electromagnetic pollution,extending the service life of electronic equipment,and the development of military stealth materials.In the research of bulk absorbing materials,ceramic-based absorbing materials have unique advantages when used in harsh environments due to their high strength,high hardness,and corrosion resistance.Among composite absorbing materials,layered two-dimensional metal carbide/nitride（MXene）materials are usually ideal for their high specific surface area,high conductivity,high absorption,large bandwidth,light weight,and low thickness.However,the widely studied Ti₃C₂T_X-type MXene is difficult to apply to ceramic-based absorbing materials.This is mainly because Ti₃C₂T_Xhas too high electrical conductivity,and it is difficult to achieve better impedance matching after being composited with ceramic materials.In addition,due to the poor high-temperature thermal stability of MXene materials,it is difficult for ceramics prepared by traditional high-temperature sintering processes to achieve an effective combination of ceramic matrix and MXene without destroying the structure of MXene.In response to the above problems,this article chose a relatively low conductivity Nb₂CT_X MXene material as the absorber,and through the"cold sintering"technology to achieve the preparation of multiphase ceramics at extremely low temperatures.The cold sintering technology is to wet and dissolve the surface of the particles by adding an appropriate solvent under the condition of external temperature and pressure,and then cause the driving force of the particle rearrangement and dissolution,which can make the embryo body completely densified at about 300℃.The application of cold sintering can greatly reduce the damage of the preparation process to MXene,retain the internal structure of the absorber intact,and further broaden the selection range of absorbers with poor thermal stability.（1）The SPS sintering method adopts the raw material ratio of Nb:Al:NbC=1:1.2:1,and the Nb₂AlC MAX phase is quickly synthesized under the conditions of 1450℃and 30 MPa.The aluminum layer was successfully etched using 1.5 g Nb₂AlC as the precursor and 3 g LiF mixed with 18 ml of hydrochloric acid as the etching solution under a closed condition of 80℃under a closed condition of 80℃.（2）The EMT zeolite material was synthesized by a template-free method.Under a cold sintering process at 300℃,500 MPa,and 30 minutes of holding time,360 ul of Na OH solution was used as a sintering aid to successfully synthesize a zeolite ceramic with a density of 2.2 g/cm~3.Compared with the density of SPS sintering Up to 94.6%.Young’s modulus is 54.6 GPa,and Vickers hardness is 2.9 GPa.（3）The Nb₂CT_X/EMT composite material is synthesized by in-situ growth method,and Nb₂CT_Xbased zeolite ceramics（Nb₂CT_X/ZC）are prepared by the cold sintering process of the matrix.The content of Nb₂CT_Xon the experimental surface has a greater impact on the mechanical properties and microwave absorption properties of the composite material.When the addition amount of Nb₂CT_Xis 10 wt%,RLmin=-56.43 d B,the effective bandwidth is 2.4 GHz,and the average MSP strength of the composite material is 40.5 MPa,which is 60%higher than that of the matrix.Nb₂CT_Xsignificantly toughens the matrix.When the amount of Nb₂CT_Xadded is 15 wt%,the fracture toughness is increased by 140% compared to the matrix.