Synthesis And Electromagnetic Microwave Absorption Properties Of Ti₃C₂T_x-Based Aerogel Materials

With the development of science and technology,there is a huge demand for electromagnetic microwave absorbing materials in the daily civilian field and military field.In order to protect human health under electromagnetic microwave pollution and enhance national defense strength,microwave absorbing materials have received extensive attention and research.However,traditional microwave absorbing materials can not cope with the increasingly diversified requirements in the modern microwave absorption field.Shortcomings such as heavy mass,simple structure,narrow effective absorption band width limit its application,so the electromagnetic microwave absorption materials should be“thin,light,wide and strong”.In this paper,Ti₃C₂T_x monolayer dispersions were prepared by etching with HCl and Li F and ultrasonic exfoliation,and different Ti₃C₂T_x-based composite aerogel materials were prepared by the template method,hydrothermal reaction,and freeze-drying processes.Subsequently,the phase composition and microscopic morphology of these composite aerogels were systematically analyzed.Then the electromagnetic wave absorption properties of each composite material were explored and their absorption mechanisms were studied.The main research contents and results of this paper are as follows.（1）The Ni source was introduced to the Ti₃C₂T_x nanosheets by mechanical stirring,and the PMMA microspheres were used as the pore-forming agent.The Ti₃C₂T_x/NiO composite aerogel with three-dimensional spherical pore structure was prepared by freeze-drying and high-temperature treatment,which not only realized the demand of light weight,but also improved its wave-absorbing performance.It was found that the loading of NiO can regulate the wave absorption performance of Ti₃C₂T_x/NiO composite aerogel.When the mass ratio of Ti₃C₂T_x to NiO was 1:1,the sample showed the best absorbing performance with the minimum RL value of-22.86 d B（10.8 GHz,with thickness of 2.5 mm）and the effective absorbing bandwidth up to 2.9 GHz（9.7-12.6 GHz）.The analysis of the loss mechanism reveals that the Ti₃C₂T_x nanosheets mainly provide dielectric loss,while the presence of NiO provides magnetic loss,which create a synergistic effect.The layered structure of Ti₃C₂T_x and the three-dimensional spherical porous structure can simultaneously provide multiple scattering and reflection of electromagnetic waves,and the interfacial polarization loss,thus achieving the improvement of the wave absorption performance of the composite material.（2）The aerogel structure can not only provide a large number of pore structures to realize the need for lightweight,the pore walls of aerogel can also provide electromagnetic wave reflection and scattering barriers.In this chapter,Ti₃C₂T_x/r GO composite aerogel was prepared by one-step hydrothermal technique with r GO as the pore-forming agent,and Ti₃C₂T_x/r GO composite aerogel with different Ti₃C₂T_xcontent was obtained when the hydrothermal temperature was 120°C and the hydrothermal time was 6 h.It was found that when the Ti₃C₂T_x to GO mass ratio was1:6,the samples had the best wave absorption performance with the minimum RL value of-53.49 d B（17.0 GHz,thickness of 2.2 mm）and the effective absorption bandwidth up to 6.6 GHz（11.4-18 GHz,thickness of 2.5 mm）.The absorption loss mechanism is mainly dielectric loss,and the introduction of r GO is beneficial to enhance the dielectric loss and build three-dimensional structure to improve the performance.（3）Based on the above study,this chapter combines the method of mechanical stirring and high-temperature treatment to introduce Ni source on Ti₃C₂T_x nanosheets and use r GO as the pore-forming agent to prepare Ti₃C₂T_x/r GO/NiO composite aerogel by hydrothermal technique.Ti₃C₂T_x/r GO/NiO composite aerogels with different NiO contents were obtained when the hydrothermal temperature was 120°C and the holding time was 10 h.It was found that the samples had the best wave absorption performance when the mass ratio of NiO to Ti₃C₂T_x was 1:1,with the minimum RL value of-62.9d B（7.5 GHz,thickness of 3.15 mm）and the effective absorption bandwidth up to 3.1GHz（10.6-13.7 GHz,thickness of 2.0 mm）.This Ti₃C₂T_x/r GO/NiO composite aerogel inherits the advantages of synergistic effect of multiple loss mechanisms and three-dimensional porous structure and can be used as a lightweight and efficient wave absorbing material.