Preparation Of Aramid Nanofiber Composite Aerogel And Its Photothermal Propertie

With population growth and socio-economic development,the demand for water resources has increased dramatically.Obtaining sufficient freshwater resources has become an urgent global problem.Solar interface evaporation technology is considered as an effective way to alleviate fresh water shortage.The ideal solar interface evaporator should have effective light absorption,reasonable thermal management,and unobstructed water transport and water vapor escape channels,among which aerogel becomes an ideal matrix for solar interface evaporation with its light weight,porous and thermal insulation properties.Aramid nanofibers（ANFs）are one-dimensional nanoscale materials obtained by deprotonation of para-aramid fibers,which combine the excellent properties of para-aramid as well as nanofibers and can be a powerful candidate for the construction of nanofiber aerogels.In this thesis,we construct aerogels with aramid nanofibers,through the synergy of multi-level pore structure and photothermal materials to enhance light absorption,promote water transport,regulate heat distribution,enhance photothermal evaporation performance,and ensure sustainability.The main research components are as follows.Aramid nanofibers were obtained by deprotonation,and high porosity ANF aerogels with oriented cell cavities were designed using ice template technology to regulate the aggregation structure of ANFs with the help of ice crystal growth.To increase the absorption of the solar spectrum,Ag NPs@ANF/Mo S₂ composite aerogels were prepared using the semiconductor Mo S₂ and the noble metal Ag NPs as the photothermal conversion materials.Its porous structure improves the light absorption by increasing the refraction of the optical path,while the synergistic photothermal material achieves 93.58%light absorption in the visible region.Meanwhile,the vertical pore channels formed inside the aerogel produce capillary effect for effective water transport and also provide a channel for water vapor transmission.The water evaporation rate of the self-drifting Ag NPs@ANF/Mo S₂ composite aerogel under 5 sun irradiation was(11.7 kg m^-2h^-1)higher than that of pure water(2.52 kg m^-2h^-1),which confirmed the feasibility of Ag NPs@ANF/Mo S₂ composite aerogel in interfacial evaporation.In order to adjust the pore structure to accomplish the fast water transfer target,Ag NPs@ANF/Mo S₂ composite aerogel with slit-type pore structure was also prepared by vacuum-assisted filtration process in this paper.Under 5 sun irradiation,the evaporation rate of Ag NPs@ANF/Mo S₂ composite aerogel could reach 13.9 kg m^-2h^-1,showing its superior ability to collect and transform solar radiation.To further improve the photothermal conversion performance,the integrated Au NPs@ANF/CNT composite aerogel was prepared by a simple freeze-drying process.In the aerogel,CNTs are entangled by ANFs to form a homogeneous nanofibrous network,which acts as the body part of the aerogel,and Au NPs are anchored onto the ANFs and are set on the surface layer of the aerogel.The resulting Au NPs@ANF/CNT aerogel has high porosity and open cell structure with self-floating lightness,low thermal conductivity for suppressing heat loss and high capillary action for absorbing water within the aerogel.Due to the synergistic effect of the carbon-rich body and Au NPs-rich surface layer,Au ACAs showed a high evaporation rate of 7.95 kg m^-2h^-1under five solar irradiations,98.6%evaporation efficiency,and the ability to purify multi-media wastewater.