纤维素基复合相变储能材料的制备及相变性能研究

Preparation and phase transition properties of cellulose-based composite phase transition energy storage materials

关键词:  纤维素  气凝胶  复合相变储能材料  相分离

Key Words:Cellulose  Aerogel  Composite phase change energy storage material  Phase separation

摘要:为克服水合盐相变材料在储能相变过程中易泄漏的问题,本研究以微纤化纤维素(MFC)、聚乙烯醇(PVA)和石墨烯(G)为原料,采用冷冻干燥技术制备了多孔结构的MFC/PVA/G气凝胶载体,并基于真空浸渍法负载十水硫酸钠相变材料后制备出了性能出色的复合相变储能材料(MFC/PVA/G-PCM)。研究结果表明MFC/PVA/G对十水硫酸钠的负载效果良好,且具有出色的尺寸稳定性和防泄漏性,导热性能提升150%以上。随着PVA含量的增加,MFC/PVA/G的比表面积增大、孔径尺寸减小。MFC₈/PVA₂/G-PCM的热焓最大,凝固晗为169.46 J/g,熔融晗为217.8 J/g,在0~50 ℃范围内经300次相变循环后其凝固焓为165.56 J/g、熔融焓为171.53 J/g,具有良好的相变循环稳定性。此外,在十水硫酸钠相变材料中引入4 wt%的硼砂可明显改善MFC/PVA/G-PCM的储能相变性能,使其结晶温度提升,过冷度减小(1 ℃内)。

Abstract:In order to overcome the problem that hydrated salt phase change materials are prone to leakage during the energy storage phase change process, in this study, the porous structure of MFC/PVA/G aerogel carriers were prepared by freeze-drying technique using microfibrillated cellulose (MFC), polyvinyl alcohol (PVA), and graphene (G) as the raw materials, and a composite phase change energy storage material with excellent performance was prepared based on the loading of sodium sulfate decahydrate phase change material by vacuum impregnation method (MFC/PVA/G-PCM). The results show that MFC/PVA/G has good loading effect on sodium sulfate decahydrate, and has excellent dimensional stability and leakage prevention, and the thermal conductivity is improved by more than 150%. With the increase of PVA content, the specific surface area of MFC/PVA/G increased and the pore size decreased, and the enthalpy of MFC₈/PVA₂/G-PCM was the largest, with the solidification enthalpy of 169.46 J/g, the melting enthalpy of 217.8 J/g, and the solidification enthalpy of 165.56 J/g and the melting enthalpy of 171.53 J/g in the range of 0-50 ℃ after 300 phase change cycles. The solidification enthalpy was 165.56 J/g and the melting enthalpy was 171.53 J/g after 300 phase change cycles in the range of 0~50 ℃. In addition, the introduction of 4 wt% of borax into the sodium sulfate decahydrate phase change material can significantly improve the energy storage phase change performance of MFC/PVA/G-PCM, resulting in an increase in the crystallization temperature and a decrease in the supercooling degree (within 1 ℃).