| The thermal use of solar energy is one of the most prominent uses of clean energy today.Since visible light,which accounts for about 45%of solar radiation,does not have a direct thermal effect,the conversion of visible light energy into thermal energy and its storage is a key scientific problem to be solved.In this paper,we have selected polyethylene glycol,which has excellent performance,as the phase change material(PCM),and introduced carbon nanotubes(CNT),organic dyes,and carbon cloth,which have the capability of photothermal conversion,into the shape-stabilized PCMs system,and synthesized three different structures of photothermal conversion PCMs,realizing the dual functions of photothermal conversion and phase change energy storage.This study provides a new idea for the synthesis of photothermal conversion shape-stabilized PCMs.The specific research includes the following three parts:(1)Self-supporting phase change materials for photosensitive polymersThe condensation reaction between diphenylmethane-4,4’-diisocyanate(MDI),a blue anthraquinone dye molecule(Bdye),and polyethylene glycol(PEG),which all have two iso-reactive groups,was used to obtain polyether-based polymeric shaped phase change materials with solid-solid phase change capability.CNT,which has excellent thermal conductivity,was then homogeneously dispersed into the polymer,and the thermal conductivity of the composite(0.405 W·m-1·K-1)was increased by 118.9%compared to that of the composite at a CNT addition of 4 wt%,resulting in a highly thermally conductive self-supporting shaped composite phase change material.The strong absorption of the dye molecule Bdye at specific wavelengths in the visible region interacts with the full-spectrum absorption of CNT to achieve a synergistic enhancement of the light absorption capacity of the composite;the heat gained from the conversion is transferred to the PEG by electronic heat conduction in the π-π conjugated structure of the MDI and Bdye molecules to achieve thermal energy storage.(2)Shape-stabilized composite PCMs with three-dimensional networkBdye was grafted onto carboxylated graphene oxide(GO)by an amide reaction,and different GO nanosheets were linked by iso-reactive amino groups at both ends of Bdye,resulting in a 3D cluster network carrier material(GO-co-Bdye).The 3D networked carrier material has a large surface area and can firmly adsorb the phase change core material PEG into the carrier by capillary forces.At the same time,the fluorescence resonance energy transfer(FRET)between GO and Bdye can further convert the fluorescence energy generated by Bdye through the radiative leap into thermal energy,which synergistically enhanced the photo-thermal conversion efficiency of the composite phase change material with the radiation-free leap of Bdye(88.6%).In addition,PEG@GO-co-Bdye showed a higher thermal conductivity 98.02%than that of pure PEG(0.499 W·m-1·K-1),as well as a high latent heat value(130.6 J·g-1)and excellent thermal stability,showing great potential in the field of photothermal conversion and energy storage.(3)Photo/electric thermal conversion(3)Multi-stage structured shape-stablized composite PCMs for photo/electro-thermal conversionA metal-organic skeleton@carbon cloth(ZIF@CC)carrier with a multi-level structure was prepared by in situ deposition of a graded zeolite imidazolium ester skeleton(ZIF)on the surface of carboxylated carbon cloth,followed by the adsorption of the phase change material PEG into the pore channels of the carrier by vacuum fusion impregnation.The carboxyl-modified CC scaffold modulated the strong attraction between ZIF and PEG to promote the crystalline-amorphous transition behavior of PEG within the pores of the carrier,thus enhancing the energy storage capacity of the phase change composite.In addition,the ZIF nanosheets deposited on the CC surface reduced the convective heat loss at the solid-gas interface,while the CC support facilitated electron transport and photon penetration,thus greatly enhancing the electrical and optical-driven thermal energy storage,which can reach a maximum electrical and photothermal conversion efficiency of 91.0%and 61.1%,respectively.This thesis developed a new method for the synthesis of highly thermally conductive self-supporting photosensitive polymer PCMs,constructed a synergistic enhancement system for the photothermal conversion performance of graphene oxide and dyes,and explored the principle of the influence of multiple material components on the crystallization behavior of phase change materials,providing a new idea for the organic integration of the dual functions of photothermal conversion and phase change energy storage. |
