Preparation And Performance Of Light-thermal Conversion Form-Stable Phase Change Materials With Modified Silicon

The visible high energy that cannot directly produce thermal energy effect accounts for about 40%of the solar radiation energy,which is difficult to be effectively utilized by phase change materials(PCMs).Therefore,the development of light-thermal conversion form-stable phase change materials can achieve the integration of the three processes of light absorption,light-thermal conversion and thermal energy storage,which is an important strategy to achieve the efficient utilization of solar energy.However,the compatibility of the directly added light thermal conversion materials with PCMs is often poor,leading to insufficient stability of the light-thermal conversion and storage performance of materials.Aiming at the key scientific problems,the silica sol was modified by using the silane coupling agent for introduction of amino or double bond reactive group,thus,the functionalized carbon nanotubes get better dispersion and the reactive dye was grafted on the silica support materials through chemical bond.Thus,the light thermal conversion form-stable PCMs with high stability,high energy storage density and high light-thermal conversion efficiency are prepared.Firstly,silica sol was modified by silane coupling agent aminopropyltriethoxysilane(APS),and then PEG/SiO2-APS form-stable phase change material was prepared by sol-gel method by using polyethylene glycol(PEG)as PCMs.When PEG content reached 88 wt%,the melting enthalpy of phase change was-170.4 J/g,and the crystallization enthalpy was 174.8 J/g.After 500 cycles of phase change,the enthalpy of phase transition only decreased by 0.63?0.65%.Using silane coupling agent 3-(Trimethoxysilyl)propyl methacrylate(KH570)modified PMMA as wall material and paraffin wax as core material,paraffin@SiO2-PMMA form-stable PCMs was synthesized.Through cross-linking agent and silane coupling agent,the connection between organic shell layer and inorganic shell layer was strengthened.When the encapsulation rate of paraffin in microcapsule was 51.9%,the melting enthalpy was-136.0 J/g,and the crystallization enthalpy was 142.8 J/g.After 500 cycles of phase transition,the enthalpy of phase transformation only decreases by 1.4%.Functional carbon nanotubes(MWCNTs-COOH and O-MWCNTs)with high thermal conductivity,full-band light absorption and light-thermal conversion was used as light-thermal conversion materials and uniformly doped into PEG/SiO2-APS composites,PEG/SAM and PEG/SAOM form-stable PCMs were prepared,respectively.The enthalpy of phase transition of PEG/SAM and PEG/SAOM reaches 133 J/g and 173.5 J/g,respectively,and the light-thermal conversion storage efficiency reaches 88%and 94.3%,respectively.Moreover,the materials have good stability of light-induced phase change heat storage performance.SiO2-dye gel was prepared by grafting reactive black 5 dye(RB5)to SiO2 supporting materiais in the form of chemical bonds by 3-aminopropyl triethoxy silane(APS),and the reaction efficiency of dye reached nearly 100%.Using PEG as phase change material and SiO2-dye gel as supporting material,PEG/SiO2-dye form-stable phase change materials were synthesized by sol-gel method.When PEG content reached 88.5 wt%,the melting enthalpy was-167 J/g and the crystallization enthalpy was 168.2 J/g.The material has a wide absorption wavelength(400-700 nm),light-thermal conversion and storage efficiency of 88.1%,and the material has a good stable light-induced phase change heat storage performance.