Marske Felix, Martins de Souza E Silva Juliana, Wehrspohn Ralf B, Hahn Thomas, Enke Dirk
Institute of Technical Chemistry, Martin Luther University of Halle-Wittenberg 06108 Halle (Saale) Germany
Institute of Physics, Martin Luther University of Halle-Wittenberg 06108 Halle (Saale) Germany.
RSC Adv. 2020 Jan 16;10(6):3072-3083. doi: 10.1039/c9ra10631f.
The confinement of phase change materials (PCMs) in construction materials has recently solved leakage, supercooling and low thermal conductivity problems in the industrial use of PCMs as monolithic thermal energy storage materials. To produce shape-stabilized PCMs (ss-PCMs) as crack-free monoliths, less than 15-30% v/v pure or encapsulated PCMs can be used in construction materials. Therefore, the heat storage capacity of these monolithic ss-PCM boards is comparatively low. In this study, we synthesized a novel class of monolithic ss-PCM boards with high compressive strength of 0.7 MPa at 30 °C (1.2 MPa at 10 °C), high PCM loadings of 86 wt%, and latent heats in the range of 100 J g a porogen-assisted sol-gel process. We confined butyl stearate (BS) as PCM in a core-shell-like silica matrix stabilized silica sol as silica source, sodium dodecyl sulfate as surfactant and poly(vinyl alcohol) as co-polymer. The ss-PCMs obtained are hydrophobic, thermally stable up to 320 °C and perform 6000 state transitions from solid to liquid and , without losing melting or freezing enthalpies. We analyzed the silica structure in the ss-PCMs to understand in detail the reasons for the high mechanical stability. The silica structure in ss-PCMs consists of spherical meso- and macropores up to 10 000 nm filled with PCM, formed mostly by BS droplets in water as templates during gelation. With an increasing BS amount in the synthesis of ss-PCMs, the total nanopore volume filled with PCM in ss-PCMs increases, resulting in higher compressive strengths up to 500% and thermal conductivities up to 60%.
将相变材料（PCM）封装于建筑材料中，最近解决了PCM作为整体式储热材料在工业应用中的泄漏、过冷和低导热率问题。为了生产无裂纹整体式的形状稳定PCM（ss-PCM），建筑材料中可使用的纯PCM或封装PCM的体积分数小于15%-30%。因此，这些整体式ss-PCM板的储热能力相对较低。在本研究中，我们通过一种致孔剂辅助的溶胶-凝胶法，合成了一类新型的整体式ss-PCM板，其在30℃时具有0.7MPa的高抗压强度（在10℃时为1.2MPa）,PCM负载量高达86wt%，潜热在100J/g范围内。我们将硬脂酸丁酯（BS）作为PCM封装于核壳状二氧化硅基质中，以稳定的硅溶胶作为硅源，十二烷基硫酸钠作为表面活性剂，聚乙烯醇作为共聚物。所得到的ss-PCM具有疏水性，在高达320℃的温度下热稳定，并且能够进行6000次从固态到液态的状态转变，而不会损失熔化或凝固焓。我们分析了ss-PCM中的二氧化硅结构，以详细了解其高机械稳定性的原因。ss-PCM中的二氧化硅结构由填充有PCM的高达10000nm的球形介孔和大孔组成，这些孔主要是在凝胶化过程中以水中的BS液滴为模板形成的。随着ss-PCM合成中BS量的增加，ss-PCM中填充PCM的总纳米孔体积增加，导致抗压强度提高高达500%，热导率提高高达60%。
