MXene/CNF复合气凝胶的制备及辐射制冷性能研究

Preparation and Radiation Refrigeration Performance of MXene/CNF Composite Aerogels

目的探究制备过程中不同MXene含量、预冻温度及方式对MXene/CNF复合气凝胶内部结构和性能的影响。方法采用原位生成HF刻蚀法和冷冻干燥法制备MXene粉末和MXene/CNF复合气凝胶,采用扫描电镜(SEM)观察刻蚀前后的MXene及–18℃、–196℃下不同含量MXene经过均相冷冻和定向冷冻的MXene/CNF气凝胶的微观结构,并测试力学性能、导热率、光谱性能及制冷性能。结果在相同预冻条件下,气凝胶的密度和力学强度随着MXene含量的增加而下降;随着预冻温度的降低,气凝胶孔隙的尺寸减小且数量增加,CM_(50)-18的孔径在103μm左右,而CM_(50)-196具有最小的孔径,为25μm左右。与普通均质冷冻相比,定向冷冻制备的气凝胶的导热率更低,并且随着MXene含量的增加,导热率增大。在80℃加热条件下其表面温度最多能降低33.4℃,制冷性能优异。而样品的表面平均温度随着MXene含量的增加而上升。不同MXene含量的气凝胶对太阳光的平均吸光度能达到0.95以上,对波长为400 nm、874 nm以及1800 nm以上的光的吸光度能达到1。结论通过定向冷冻制备的MXene/CNF的力学性能、光谱性能、制冷性能有所改善。

The work aims to explore the effects of different fabrication conditions on the internal structure and properties of MXene/CNF composite aerogels.Mxene powder and MXene/CNF composite aerogels were prepared by in-situ HF etching and freeze-drying methods.A scanning electron microscopy(SEM)was used to observe the microstructure of MXene before and af-ter etching and MXene/CNF aerogels with different MXene content after homogeneous freezing and directional freezing at-18℃and-196℃,respectively.The mechanical properties,thermal conductivity,spectral properties and refrigeration proper-ties were tested.According to the experimental results,under the same pre-freezing conditions,the density and mechanical strength of aerogels decreased with the increase of MXene content.With the decrease of pre-freezing temperature,the size and number of aerogel voids decreased and increased respectively.The pore size of CM_(50)-18 was 103μm.CM_(50)-196 had a minimum aperture of 25μm or so.The thermal conductivity of aerogels prepared by directional freezing was lower than that prepared by ordinary homogeneous freezing,and increased with the increase of MXene content.The surface temperature could be decreased by 33.4℃at most under the heating condition of 80℃,contributing to good refrigeration properties.The average surface tem-perature of the sample also increased with the increase of MXene content.The average absorbance of aerogels with different MXene content to sunlight was more than 0.95,and the absorbance of aerogels with wavelengths of 400 nm,874 nm and 1800 nm was more than 1.Through these results,it can be analyzed that the mechanical properties,thermal conductivity,spectral properties and refrigeration properties of MXene/CNF prepared by directional freezing have been improved.