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 Change 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 materials  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，制备了具有多孔结构的气凝胶载体（MFC/PVA/G），并基于真空浸渍法负载相变材料Na₂SO₄·10H₂O后，制备出了性能出色的复合相变储能材料（MFC/PVA/G-PCM）。结果表明，MFC/PVA/G对Na₂SO₄·10H₂O的负载效果良好，且具有出色的尺寸稳定性和防泄漏性，相比纯Na₂SO₄·10H₂O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。对比其他MFC/PVA/G-PCM，当MFC与PVA质量比为8∶2时，MFC₈/PVA₂/G-PCM的热焓最大，凝固焓为169.5 J/g，熔融焓为217.8 J/g，在0~50 ℃范围内，经300次相变循环后，其热焓变化不大，凝固焓为165.6 J/g、熔融焓为170.3 J/g，具有良好的相变循环稳定性。此外，在Na₂SO₄·10H₂O中引入4%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（变化范围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， aerogel carrier （MFC/PVA/G） with porous structure were prepared from microfibrillated cellulose （MFC）， polyvinyl alcohol （PVA）， and graphene （G） by using freeze-drying technology， and after loading the phase change material Na₂SO₄·10H₂O based on vacuum impregnation method， composite phase change energy storage materials （MFC/PVA/G-PCM）. The results showed that the MFC/PVA/G had good loading effect on Na₂SO₄·10H₂O with excellent dimensional stability and anti-leakage， and the thermal conductivity was improved by more than 150% compared with that of pure Na₂SO₄·10H₂O. With the increase of PVA content， the specific surface area of MFC/PVA/G increased and the pore size decreased. Comparing with other MFC/PVA/G-PCM， when the mass ratio of MFC and PVA was 8∶2， the enthalpy of MFC₈/PVA₂/G-PCM was the largest， with the enthalpy of solidification being 169.5 J/g and the enthalpy of melting being 217.8 J/g. In the range of 0~50 ℃， the enthalpy of solidification after 300 phase change cycles was not changed much， with the enthalpy of solidification being 165.6 J/g and the enthalpy of melting 170.3 J/g， which had good stability of phase change cycle. In addition， the introduction of 4% borax into Na₂SO₄·10H₂O could significantly improve the energy storage phase change performance of MFC/PVA/G-PCM， resulting in an increase in the crystallisation temperature and a decrease in the degree of supercooling （within the variation range of 1 ℃）.