形态稳定的Na2SO4·10H2O-Na2HPO4·12H2O共晶盐相变储能材料的制备及热性能提升

在复合相变材料中引入碳纳米纤维(CNFs)提高相变体系的导热系数,以实现相变材料与外界环境进行快速有效的热量交换。本文采用熔融共混法将Na₂SO₄·10H₂O和Na₂HPO₄·12H₂O制备成共晶盐相变材料,借助聚丙烯酸钠构筑三维聚合物网络封装相变材料,利用CNFs提升复合材料的导热系数。通过Raman、XPS等测试方法,研究了CNFs经高能球磨、湿化学氧化处理后,其表面含氧官能团的变化;借助Raman、DSC、Hot disk、TG等测试方法,分析了CNFs对复合材料化学相容性、相变行为、热稳定性、潜热容量、导热系数的影响。结果表明:CNFs经过功能化处理,氧、碳原子比增大至0.140,氧化效果显著;CNFs引入至复合相变材料中,体系内各组分之间存在良好的化学相容性;当CNFs的添加量达到3%(质量分数),复合材料的固、液态导热系数分别达到1.05 W/(m·K)、0.88 W/(m·K),相较于未添加CNFs的复合材料,固、液态导热性能分别提升了69.4%、60.0%;经过1 000次循环试验,复合材料的熔融焓和结晶焓相较循环前分别下降了56.2%、65.3%,相变体系仍然具备一定的储热能力,表明将相变材料嵌入三维网络结构是一种有效的封装策略。

Preparation and Thermal Performance Enhancement of Shape-Stable Na2SO4·10H2O-Na2HPO4·12H2O Eutectic Salt Phase Change Energy Storage Materials

For the purpose of rapid and effective heat exchange between phase change materials and the external environment, carbon nanofibers (CNFs) were introduced to improve the thermal conductivity of composite phase change materials. In this paper, Na₂SO₄·10H₂O and Na₂HPO₄·12H₂O were prepared into eutectic salt phase change materials by melt blending method, three-dimensional polymer network encapsulation phase change materials were constructed with sodium polyacrylate, and CNFs were used to improve the thermal conductivity of the composites. The changes of oxygen functional groups on the surface of CNFs treated by high energy ball milling and wet chemical oxidation were investigated by Raman and XPS; the effects of CNFs on the chemical compatibility, phase transition behavior, thermal stability, latent heat capacity and thermal conductivity of the composites were analyzed by Raman, DSC, Hot disk and TG. The results show that after functionalization of CNFs, the atomic ratio of oxygen and carbon increases to 0.140, and the oxidation effect is remarkable. The introduction of CNFs into composite phase change materials has good chemical compatibility among the components in the system. When the addition amount of CNFs reaches 3% (mass fraction), the solid thermal conductivity of the composites reaches 1.05 W/(m·K), and the liquid thermal conductivity is 0.88 W/(m·K). Compared with the composites without CNFs, the solid-liquid thermal conductivity increases by 69.4% and 60.0%, respectively. After 1 000 cycles, the melting enthalpy of the composite decreases by 56.2% and the crystallization enthalpy decreases by 65.3% compared with that before cycles. The phase change system still has a certain heat storage capacity, indicating that embedding phase change materials into three-dimensional network structure is an effective packaging strategy.