Preparation And Properties Of Microencapsulated Tetradecanol As Phase Change Materials Doped With Modified Nanomaterials

With the growing energy crisis and environmental pollution problems,the development of new energy storage materials and technologies has become a hot topic for scientists in recent years.As a novel type of heat storage medium,microencapsulated phase change materials can store and release heat through its reversible phase change process,and at the same time it can suppress the leakage of the melted phase change materials.This paper mainly studies the application and modification of phase change microcapsules.In view of problems,such as poor thermal conductivity and the supercooling of the traditional phase change microcapsules,various hydrophobically modified inorganic nanomaterial with good thermal conductivity were introduced to prepare organic/inorganic composite phase change microcapsules.The surface morphology of microcapsules was observed by using optical microscope（OM）and scanning electron microscope（SEM）.The thermal properties and thermal stability of microcapsules were characterized by differential scanning calorimetry apparatus（DSC）and thermogravimetric analyzer（TG）.The chemical composition and structure of the microcapsule were evaluated using fourier transform infrared spectroscope（FT-IR）and X-ray fluorescence spectrometer（XRF）.The temperature control performance of the microcapsules was analyzed by a multi-channel temperature inspection instrument.The particle size distribution of the microcapsules was characterized by a laser particle size distribution analyzer.The main conclusions are listed as follows:（1）In order to enhance the solubility of carbon nanotubes in organic solvent,alkylated carbon nanotubes（i-CNTs）were prepared by reacting carboxyl-terminated carbon nanotubes（C-CNTs）with hexadecylamine with the aid of the condensation agent1,3-dicyclohexylcarbodiimide（DCC）.The carbon nanotube composite phase change microcapsules,with melamine-urea-formaldehyde resin（MUF）as the wall material and n-tetradecanol（TD）doped with i-CNTs as the core material,were prepared by in-situ polymerization.The test results of phase change microcapsules have shown that when the concentration of emulsifier was 0.5 wt%and the additive amount of i-CNTs was 20 mg,the obtained microcapsules have a more regular morphology with a latent heat of fusion of159.0 J/g,and an average particle size of 144.5μm.Compared with pure tetradecanol microcapsules,the core content of the modified microcapsules increased by 17.6%after the core material was doped with 20 mg i-CNTs.The results of TG and multi-channel temperature inspection instrument have shown that phase change microcapsules doped with20 mg i-CNTs show good thermal stability and temperature control performance.（2）In this study,silane coupling agent was applied to modify the surface of inorganic nano-Al₂O₃.The effects of coupling agent type and solvent system on the properties of modifiednano-Al₂O₃ werestudied.Theresultsshowthatwhen3-glycidoxypropyltriMethoxysilane（KH560）is selected as the silane coupling agent and the solvent is 95%ethanol,the dispersion stabilization of modified Al₂O₃ nanoparticles in the organic solvent of dichloromethane is significantly improved.（3）The tetradecanol phase change microcapsules doped with modified nano-Al₂O₃were successfully prepared by in-situ polymerization.The effects of emulsifier concentration and modified nano-Al₂O₃ addition on the properties of phase change microcapsules were studied.The experimental results show that when the emulsifier concentration is 1 wt%and the modified nano-Al₂O₃ is added in an amount of 0.4 g,the microcapsules have good heat storage properties and morphology,and the latent heat of fusion is up to 165.4 J/g.The supercooling degree of the modified phase change microcapsules is 4.79 ℃ lower than that of traditional tetradecanol microcapsules.At the same time,after doped with modified nano-Al₂O₃,the temperature control performance of the microcapsules was improved.The obtained phase change microcapsules had good thermal stability in the temperature range of conventional applications（less than 150 ℃）.