Preparation,Structure And Properties Research Of Polymer/MXene Radiative Heating/Cooling Composites

Traditional energy as the propellant for world development has been consumed in large quantities,resulting in the increasingly serious energy crisis and global warming.Heating and cooling are important components of traditional energy consumption,especially in areas such as building energy consumption and industrial thermal management.Thermal management is closely related to environment and energy issues.However,the low heating and cooling efficiency of traditional thermal management materials seriously hinders the realization of energy saving and emission reduction and the dual carbon strategic goals of"emission peak and carbon neutrality".Therefore,it is necessary to develop new thermal management materials to improve heating and cooling efficiency and reduce thermal management energy consumption.Due to its spectral selectivity,radiative thermal management materials can achieve efficient passive thermal management of individuals and spaces by selectively regulating radiation reflectivity or emissivity without active energy supply.However,at present,radiative thermal management materials generally have some disadvantages,such as complex preparation process,high cost,single mode and poor practicability.Therefore,the design and preparation of high efficiency,green and energy saving new radiative thermal management materials is significant to the sustainable development of energy.In this paper,based on the two polymers of nanoporous polyethylene(nano PE)and Poly(vinylidene fluoride)(PVDF),the two-dimensional nano material MXene is introduced.The textile with high-efficiency radiative heating and the film material with dual modes of radiative cooling/heating are prepared by a simple surface spraying method.Its passive radiative heating,radiative cooling,solar heating and Joule heating properties are deeply investigated.The main research contents are as follows:(1)Polydopamine(PDA)was used to hydrophilically modify nano PE textile,and then Ti3C2Tx MXene solution was sprayed on the modified textile to obtain MXene/nano PE textile.It has three heating modes:passive radiative heating,solar heating and Joule heating.Due to the low infrared emission characteristics of MXene,the infrared emissivity of MXene/nano PE textile is only 17.6%with a thickness of only12μm in the wavelength range of 7～14μm.Therefore,the passive radiative heating performance of MXene/nano PE textile is excellent,which is 4.9℃higher than that of traditional cotton textile(576μm).In addition,MXene’s high photothermal conversion efficiency and conductivity also give MXene/nano PE textile excellent solar heating performance and Joule heating performance.It can rise to 73.5℃and 55℃under 840 W/m~2 solar irradiance and 5 V voltage,respectively.When the three heating modes are turned on simultaneously,the maximum temperature of MXene/nano PE textile can reach 90℃.In addition,MXene/nano PE textile has excellent wearability,including mechanical strength,water vapor permeability,windproof ability,flame retardancy,electromagnetic interference shielding,antibacterial and quick drying.(2)Porous PVDF films were prepared by phase conversion and the radiative dual-mode(cooling/heating)MXene/PVDF composite films were prepared by spraying MXene solution onto the films.The two modes can be switched by film inversion.In the process of phase conversion,continuous coral like porous structure is formed in the PVDF film,which has a strong scattering effect on sunlight.In the cooling mode,the reflectivity of MXene/PVDF film to sunlight is as high as 96.7%,and in the atmospheric window(8～13μm),the IR emissivity reaches 96.1%.The excellent spectral selectivity of MXene/PVDF film endows it with high radiative cooling performance,which can achieve the daytime radiative cooling performance of 9.8℃and the nighttime cooling performance of 11.7℃.The daytime radiative cooling power and nighttime cooling power reach 107.5 W/m~2 and 140.7 W/m~2,respectively.MXene’s low mid infrared emissivity,high photothermal conversion ability and high conductivity give MXene/PVDF film excellent passive radiative heating performance(40.7℃),solar heating performance(41.2℃)and Joule heating performance(63.9℃).After turning on the triple heating mode,the maximum temperature of MXene/PVDF film can reach 73.2℃.In addition,MXene/PVDF film also has excellent practical properties such as water vapor permeability,water stability,tensile properties,electromagnetic interference shielding and flame retardancy.