Direct Introduction Of Amino Termination On The Surface Of Ti₃C₂ MXene And Its Effect On The Properties Of Multifunctional RGO/Ti₃C₂-NH₂ Films

The surface termination of two-dimensional transition metal carbides/nitrides（MXenes）has a great impact on the performance of MXenes.The introduction of amino termination on the surface of Ti₃C₂ MXene can not only increase the dipole on its surface,but also regulate the ratio of covalent bonds and hydrogen bonds between nano assembly units,so as to realize a variety of excellent properties of its assembly and expand its application range.At present,the commonly used amino modification methods are molten salt etching method and polymer branching.Among them,molten salt etching method requires high temperature and difficult operation;the introduction of polymer will lead to the decline of electrical and thermal conductivity.Therefore,in order to solve these problems,a simple sealed thermal method is proposed in this paper.Amino termination was directly introduced on the surface of Ti₃C₂ MXene.Based on Ti₃C₂–NH₂ MXene,a multifunctional rGO/Ti₃C₂–NH₂ composite film was prepared.The main research contents and results are as follows:（1）Preparation of Ti₃C₂–NH₂ MXene by sealed thermal method and mechanism of amino introduction.The amino termination was directly introduced on Ti₃C₂ MXene surface by sealed thermal method;Using FTIR and XPS,combined with the analysis of electromagnetic shielding performance and interface strengthening effect of Ti₃C₂–NH₂ based composites,the direct introduction of amino termination is proved,and the corresponding introduction mechanism is put forward;the solution dispersion and conductivity of Ti₃C₂–NH₂ were analyzed by Zeta potential and UPS.The results show that it is convenient to introduce amino termination directly on Ti₃C₂ MXene surface by sealed thermal method,and the morphology and crystal structure of Ti₃C₂–NH₂nanosheets are similar to those of conventional Ti₃C₂ nanosheets;The introduction of amino groups is due to the attack of positively charged NH₄⁺on negatively charged-OH groups with low binding energy with Ti,so that some-OH groups are replaced by-NH₂groups;although the electronegativity and electron carrier density of Ti₃C₂–NH₂nanosheets are reduced,they still have excellent solution dispersion and conductivity.（2）Preparation and properties of multifunctional rGO/Ti₃C₂–NH₂ composite films.The effect of Ti₃C₂–NH₂ on the interface action and nanostructure order of the composite films were analyzed.The improvement mechanism of the interface action and nanostructure order on the mechanical properties,in-plane thermal conductivity and electromagnetic wave response of the composite films was explored.The results show that Ti₃C₂–NH₂ can induce covalent bonding at the interface of the composite film and make the nanostructure order of the film better.The existence of covalent bonds greatly improves the mechanical properties of rGO/Ti₃C₂–NH₂,its maximum tensile strength and fracture energy can reach 213.82 MPa and 196.19 J mm^-2,respectively.The maximum remained stress can be maintained at 81%.The average fatigue cycles to failure of 3rGO/7Ti₃C₂–NH₂ film approach to 16951 times under 150MPa maximal tensile loading.The in-plane ordering and amide covalent bond greatly reduce the interfacial thermal resistance of the composite film,and its maximum thermal conductivity is about 48.9 W m^-1 K^-1.The absorptivity of Ti₃C₂–NH₂ based film greatly surpassed the maximum of the components in both X-band and middle infrared band.Its maximum absorptivity in X-band is about 70%,and that in middle infrared band is about 55%.It suggests that this film has good prospects in multifunctional flexible film with excellent mechanical properties,EMI shielding,heat dissipation and thermal accumulation monitoring capability.