Preparation And Microwave Absorption Properties Of Lightweight Ti₃C₂T_x MXenes Based Composite Aerogel

Nowadays,rapidly expanding electromagnetic?EM?radiation interference and pollution have aroused imperative concern to develop EM wave?EMW?absorbing materials,which dissipate external EMW by converting EM energy into thermal energy.And EMW absorbers are playing an increasingly crucial role in military defense security,electronic reliability and healthcare.The new-generation EMW absorption materials may satisfy the requirements of lightweight,strong absorption,broad absorption bandwidth and thin coating thickness,which are necessary to satisfy the ever-growing demand for practical applications.To fulfill above characteristics,considerable efforts have devoted to the study of high-efficiency EMW absorption materials.In this thesis,Ti₃C₂T_x and its hybrids composites applied to EMW absorption are thus fabricated,and a facile and effective route of the as-prepared materials is developed.Especially,the relation between structure characteristics,EM parameters and EM absorbing performance are systematically investigated.Considering the electromagnetic wave?EM?absorption ability of Ti₃C₂T_x MXenes have only been explored in X?8-12.4 GHz?band,in this paper,we synthesized Ti₃C₂T_x by using HF solution for different etching times and then investigated comprehensively as EM absorbing materials in the centimetre-band?C,X and Ku band?from 2 to 18 GHz for the first time to make up the research vacancy.The impact of etching time on the crystal structure,morphology,surface termination and absorption performance of Ti₃C₂T_x were investigated.Besides,the influences of mass ratio,layer thickness and different morphologies on the EM wave absorption performance were systematically studied.Among the etching samples,Ti₃C₂T_x-24exhibited the optimal RL_min value of-42.5 dB with a matching thickness of 1.7 mm and a broad and tunable absorption bandwidth of 13.8 GHz.The superior EM wave absorption could be ascribed to the multiple reflections and scatterings and interfacial polarizations produced in the generated interfaces due to the laminated structure after etching.Most notably,the EM wave absorption performance of Ti₃C₂T_x was compared to those typical two-dimensional materials in this work.The thorough explorations aim to supplement and improve the study of EM wave absorption properties of Ti₃C₂T_x in the centimetre-band and further design Ti₃C₂T_x based hybrid materials reasonably and effectively.Furthermore,multilayer sandwich heterostructural Ti₃C₂T_x modified with polypyrrole chains have been fabricated successfully via HF etching treatment and in-situ chemical oxidative polymerization approach,and investigated as EM wave absorbers for the first time.The samples were well characterized in terms of crystal structure,microstructure,morphology and EM wave absorption performance.The hierarchical multilayer microstructure and synergistic effect between laminated Ti₃C₂T_x and conductive polypyrrole network make contributions to the enhanced EM wave absorption performance in the frequency range of 2-18 GHz.With the mass fraction of 25 wt%in paraffin matrix,Ti₃C₂T_x/PPy hybrids exhibited the effective bandwidth of 4.9 GHz at 2.0 mm and an optimal RL_min of-49.2 dB at 8.5 GHz with coating layer thicknesses of 3.2 mm.Furthermore,an effective bandwidth?RL<-10dB?of 13.7 GHz?4.3-18 GHz?could be achieved via adjusting thicknesses from 1.5to 5.0 mm.Tunable and high-efficiency electromagnetic wave?EMW?absorption materials of three-dimensional?3D?hierarchical reduced graphene oxide?RGO?aerogel network entrapped with TiO₂/Ti₃C₂T_x hybrids were synthesized by a hydrothermal process and a mild chemical reduction treatment,and investigated as EM wave absorbers for the first time.The as-acquired samples were well characterized in terms of morphology,microstructure,EM properties.The highly porous conductive networks,better impedance match,multiple reflection and scattering and defective polarization properties of the resultant TiO₂/Ti₃C₂T_x/RGO composite aerogel make dominating contributions to the enhanced EMW absorption performance.When the filler loading of TiO₂/Ti₃C₂T_x/RGO ternary composite aerogel in paraffin matrix is only 10 wt%,the optimal reflection loss of the composite was up to-65.3 dB at a thickness of only 2.5 mm and the effective absorption bandwidth exceeding-10 dB were 4.3 GHz when the coating thickness is only 2.0 mm.And the tunable absorption bandwidth achieves to 13.8 GHz via adjusting the thicknesses from 1.5 to 5.0 mm.Lightweight and enhanced electromagnetic wave?EMW?absorbing materials of three-dimensional?3D?hierarchical reduced graphene oxide?RGO?aerogel modified with in-situ entrapped MnO₂/Ti₃C₂T_x micro-nanohybrids,which were obtained by a hydrothermal process,were realized by a mild chemical reduction and a direct freeze-drying route.The as-obtains specimens were well characterized in terms of morphology,microstructure,composition,EM parameters.The well-defined architectures not only successfully reduces the agglomeration of RGO and the density of the composites,but also contributes a lot to matching impedance,conductive loss,multiple reflection and interfacial polarizations,thus achieving enhanced EMW absorption performance.As the filler loading of MnO₂/Ti₃C₂T_x/RGO ternary composite aerogel sample in the paraffin matrix is only 10 wt%,the RL_min was-66.5dB at 2.0 mm together with the effective bandwidth of 3.5 GHz within whicn the RL value is exceeding-10 dB.