Construction Of MXene Based Porous Materials By Pickering Emulsion Method And Their Electromagnetic Wave Absorption Properties

With the booming development of wireless electronic device,information and communication technology,and national defense and military,problems such as electromagnetic radiation and electromagnetic interference are increasingly serious.Therefore,it is urgently need to develop electromagnetic wave absorption material that can maintain stable and efficient performance in harsh environments.In this paper,Pickering emulsions were prepared by using cellulose nanofiber（CNF）,Ti₃C₂T_x and nickel nanochain（Ni NW）or nickel chloride hexahydrate（NiCl₂·6H₂O）as the aqueous phase and cyclohexane solution containing paraffin（PW）or styrene-butadiene-styrene（SBS）as the oil phase.And the composite porous materials were further constructed by combining freeze-drying or thermal annealing process.The details are as follows:（1）The aqueous mixture dispersions of CNF and Ti₃C₂T_x or CNF,Ti₃C₂T_x and Ni NW as the water phase and cyclohexane as the oil phase were used to form multiple particle co-stabilized Pickering emulsions by ultrasonic emulsification,respectively.The effects of particle concentration,water/oil volume ratio,p H value and ionic strength of aqueous phase on the morphology and stability of the emulsion were systematically investigated.CNF,Ti₃C₂T_x and Ni NW can synergistically stabilize Pickering emulsions,and the droplet size decreased with the increase of Ti₃C₂T_x and Ni NW particle concentrations,and the emulsions had good stability in p H 5-11 and ionic strength 0 m M-200 m M.The CNF/MXene/Ni（CMN）foam was further prepared by freeze-drying,which had a minimum reflection loss value of-30.2 d B and an effective bandwidth of 1.76 GHz at a thickness of 5.0 mm as well as can maintain a surface temperature of 80.9°C under a simulated sunlight irradiation at 1 Sun,showing potential application in electromagnetic wave absorption and photothermal conversion areas.（2）Based on the formation of Pickering emulsion gel with CNF,Ti₃C₂T_x and Ni NW aqueous dispersion as the aqueous phase and cyclohexane as the oil phase,PW was further introduced into the oil phase and the CNF/MXene/Ni NW/PW composite foam with embedded microsphere was prepared by freeze-drying.The effects of mass concentration ratio of CNF and MXene,Ni NW mass concentration,PW type and test environment temperature（25°C-100°C）on the structural morphology and wave absorption property of the composite foam were investigated.A minimum reflection loss value of-47.1 d B and an effective bandwidth of 4.9 GHz were achieved with C1M2N3P30 at a thickness of only 2.0 mm.The foam not only had photothermal conversion and thermal insulation properties,but also maintained stable and effective wave absorption performance at 50°C.（3）Based on the formation of Pickering emulsion gel with CNF and MXene dispersion containing Ni²⁺as the aqueous phase and cyclohexane solution containing SBS as the oil phase,the C-CNF/MXene/Ni NW composite carbon foam was prepared by in-situ formation of Ni NW in the 3D pore structure,combined with freeze-drying and thermal annealing treatment.The effects of CNF,MXene and Ni²⁺contents on the structural morphology and wave absorption property of the carbon foam were investigated.A minimum reflection loss value of-45.2 d B and an effective bandwidth of 7.6 GHz were obtained for C-C1M1N3 at a thickness of 2.5 mm.After 2 months of exposure to air,C-C1M1N3 maintained a minimum reflection loss value of-25.0 d B and an effective bandwidth of 6.7 GHz with good oxidation resistance.The hydrophobic and lipophilic properties also enabled the carbon foam to adsorb a wide range of solvents or oils,showing a promising application in the field of oil-water separation.