形状稳定相变材料的制备及其热物性研究

PREPARATION OF SHAPE STABILIZED PHASE CHANGE MATERIALS AND THEIR THERMOPHYSICAL PROPERTIES

吴邦耀

11930260

硕士

工程硕士

孙大陟

2021-05-17

2021-06-24

南方科技大学

深圳

能源短缺是限制人口的不断增长以及现代工业的快速发展的关键因素。使用基于固-液相变的相变储能材料可以有效解决能源供应与需求之间不匹配，从而减少传统能源的消耗。但纯固-液相变材料在蓄热过程中存在易泄露的问题，这严重限制了其实际应用。利用多孔支撑材料制备形状稳定相变材料是解决泄露问题的最常用的手段。但是，制备高相变储热（>125 J/g）、高相变介质吸附量(>70%)的形状稳定相变储能材料依旧是个挑战。作为载体来吸附相变介质的生物质硅藻壳具有高比表面积和独特的多级孔结构。实验通过对煅烧温度的调控，可以有效调节硅藻壳载体的微观形貌和孔隙结构。400℃下煅烧的硅藻壳具有相对较高的比表面积（~155.9 m2/g），同时其精细的三维骨架保持良好。使用硅藻壳制备的形状稳定相变复合材料可实现72.7％的PEG4000负载，相应的熔融焓为128.9 J/g，凝固相变焓为136.7 J/g，热能储存效率高达97.7％。硅藻壳对PEG优异的吸附能力是因为其高的比表面积、丰富的多级孔结构以及表面大量的硅羟基。充放热循环测试表明复合材料仍具有良好的热稳定性与化学稳定性。因此，将PEG/硅藻壳复合材料应用在建筑材料具有巨大的前景。制备基于固-固相变的相变储能材料是解决泄露问题的另一个有效策略。本文利用1-十六烷基-3-甲基咪唑溴盐离子液体在升温过程中发生晶型结构转变来实现热能存储与释放。热管理模拟测试表明嵌入了合成的离子液体相变材料的散热器能够高效地利用LED灯工作过程所散发的热量来提供额外300s的温度控制，因此可实现对大功率电子器件的被动式热管理。实验中进一步添加石墨烯纳米片来构筑导热通路以强化相变材料的导热能力。添加了1 wt%石墨烯纳米片的复合相变材料的导热系数达到了0.410 W/mK，相比于原始离子液体提高了44.4%，同时其结晶焓为66.4 J/g，熔融焓为57.3 J/g。综上，本论文利用独特的生物无机材料羽纹纲硅藻壳成功制备出高相变焓复合材料，拓展了硅藻壳在相变储能领域的应用。实验合成出固固相变材料—咪唑溴盐离子液体，通过巧妙地设计可以应用于电子器件热管理系统。

Phase-change energy storage technology is an effective approach to solve the worldwide energy crisis. Nowadays, the development of shape stabilized phase change materials (ss-PCMs) are highly applied for thermal energy storage (TES)，thereby reducing traditional energy consumption. The ss-PCMs have many advantages, such as a relatively small phase-change temperature range, very high TES density, and no leakage problems during the phase change process. Thus, ss-PCMs are capable of realizing effective storage and stable conversion of thermal energy for a long time. However, Based on SiO2 porous materials ss-PCMs with high heat storage (>125 J/g) and high adsorption capacity (>70%) are still challenging. Biomass-based diatom frustules used as a SiO2 porous carrier have a high specific surface area and the hierarchical pores structure to absorb PCMs. The microscopic morphology of diatom frustules can be adjusted by changing the calcination temperature. The diatom frustules calcined at 400°C (400CDF) have a relatively high specific surface area (~155.9 m2/g) containing a large number of silanols and maintain a 3D framework with the coexistence of mesopores and macropores. The designed PEG/400CDF achieves 72.7 wt% PEG4000 loading, resulting in 128.9 J/g melting enthalpy and 136.7 J/g freezing enthalpy. And more importantly, the heat storage efficiency reaches up to 97.7%. The 200-time high-low-temperature cycles show that the composite still has excellent thermal and chemical stability. Therefore, the application of PEG/CDF to building materials can effectively absorb and utilize solar radiant heat, maintaining a comfortable indoor environment. Preparation of ss-PCMs based on solid-solid phase transition is another effective strategy to solve the leakage problem. The 1-hexadecyl-3 methylimidazole bromide ([C16MIM]Br) undergoes crystal structure transformation during the heating process to realize thermal energy storage and release. In the LED lamps’ thermal management application, the heat sink embedded with ionic liquid PCMs can use the heat emitted during the working process of the LED lamp more efficiently. Thus, it achieves temperature control for an extra 300s, realizing the passive thermal management strategy. Graphene nanosheets are further added to build a thermal conduction path to enhance PCMs’ thermal conductivity. The thermal conductivity of the composite added with 1 wt% graphene nanosheets reaches 0.410 W/mK, which is 44.4% higher than the original [C16MIM]Br. Besides, its crystallization enthalpy is 66.4 J/g, and the melting enthalpy is 57.3 J/g.In summary, taking ss-PCMs as the starting point, we tactfully designed the CDF-based composite with high enthalpy, which expands the application of diatom frustules in the field of phase-change energy storage. What’s more, we synthesized the imidazolium bromide ionic liquid and successfully applied it into the field of device thermal management.இ

硅藻壳 形状稳定相变材料 聚乙二醇 离子液体 石墨烯纳米片

diatom frustules shape stabilized phase change materials polyethylene glycol ionic liquids graphene nanosheets

中文

独立培养

南方科技大学

吴邦耀. 形状稳定相变材料的制备及其热物性研究[D]. 深圳. 南方科技大学,2021.