The Construction Of Three-dimensional Porous MXene Materials With Terahertz Shielding Performance

Terahertz technology has received widespread attention because of its potential applications in many frontier fields.With the rapid development of terahertz devices,terahertz electromagnetic interference shielding materials have become more and more important due to the urgent need to manage electromagnetic radiation emission and interference in complex systems.Although extensive research has been conducted on reducing gigahertz（GHz）radiation pollution,there are few reports on high-performance terahertz shielding materials.In order to meet the requirements of increasingly popular portable and wearable devices,research on low-density,ultra-thin,flexible,and even foldable terahertz shielding materials has become crucial.Designing a three-dimensional porous structure has been proven to be an effective way to greatly reduce the density and improve the electromagnetic interference shielding performance by promoting internal multi-scattering to further attenuate incident microwaves.Because of its rich surface chemistry and superior metal conductivity,MXene has attracted attention in the field of electromagnetic interference shielding.However,the three-dimensional MXene material used for electromagnetic interference shielding has weaker inter action between rigid MXene,resulting in poor structural stability and limited mechanical flexibility,which limits its application in the field of terahertz shielding.Therefore,it is urgent to seek efficient and controllable technology to obtain self-supporting three-dimensional porous MXene foam with strong stability and strong mechanical flexibility.In response to the above problems,this thesis proposes an efficient and controllable metal ion diffusion-induced gelation method for the manufacture of self-supporting,lightweight,foldable and highly stable MXene foam material with internally oriented porous structure and high Electrical conductivity makes it have good terahertz shielding performance.The main content and innovations of this thesis are as follows:（1）Use metal foil to automatically release polyvalent metal ions in the acidic MXene and graphene oxide dispersion to achieve metal ion-induced gelation,in which MXene is effectively cross-linked by polyvalent metal ions and a small amount of graphene oxide to form orientation.The cells are connected to the porous structure.This method is highly efficient and controllable,and can be extended to generate functional three-dimensional porous MXene materials with arbitrary shapes and synergistic properties.The unique cross-linked porous structure endows the lightweight MXene foam with good foldability and excellent durability and stability in humid environments.At the same time,due to the well-designed porous structure and moderate electrical conductivity,the three-dimensional porous MXene and a small amount of graphene oxide composite foam has an excellent terahertz shielding effectiveness of 51 d B at a small thickness of 85μm and a low density of 0.11 g cm^-3.（2）Under the same conditions,by only increasing the concentration of the MXene dispersion to 10 mg ml^-1,without adding additional graphene oxide and other crosslinking agents,the metal ion-induced gelation can be directly carried out.In the end,a lightweight pure MXene foam can still be obtained.Due to the absence of other substances with low conductivity,the conductivity of MXene foam is greatly improved(1678 s m^-1),making it reach an average EMI SE in the 0.1-2.0 THz band52.9 d B,the density is only 0.005 g cm^-3,and the thickness is about 200μm,indicating that most of the terahertz wave radiation can be shielded.This work not only provides ideas for the design of high-performance terahertz shielding materials,but also simplifies the gelation process induced b y metal ion diffusion and eliminates the use of crosslinking agents,so that the inherent excellent characteristics of MXene can be well retained.Expand its scope of application.In summary,the method of using metal ions to induce gelation proposed in th is thesis can efficiently and controllably prepare three-dimensional porous MXene foam,and make it light,high conductivity,excellent mechanical flexibility,and strong water environment stability.It provides a new type of shielding material for terahertz shielding equipment,and at the same time provides new ideas for the three-dimensional construction of MXene materials.