高温相变材料Li_2CO_3-Na_2CO_3循环热稳定性分析

Thermal stability of Li_2CO_3-Na_2CO_3 based high-temperature phase change materials

利用静态熔融法制备了Li2CO3-Na2CO3(4∶6,质量比)二元熔盐。采用自制"自动热循环测试系统"测试了400～600℃内此二元熔盐1010次热循环,分析了其相变参数动态变化特性,利用DSC测试了其热稳定性,利用XRD分析了其化学组分。结果表明:"自动热循环测试系统"可以替代DSC定性测试相变材料的热循环稳定性;Li2CO3-Na2CO3二元熔盐熔化/凝固过程中主要以LiNaCO3形式存在,其峰值温度为499.1℃,其相变潜热为365.5J/g;热循环过程中,此二元熔盐的熔化和凝固温度变化不大,相变潜热最大降低了45.3J/g;通过XRD物相分析,可知整个循环过程中此二元熔盐的物相没有明显的变化。总之,Li2CO3-Na2CO3二元熔盐能够满足太阳能高温热发电和其它高温储热需求。

This paper is concerned about the thermal stability of a lithium carbonate-sodium carbonate （40%Li2CO3-60%Na2CO3 by mass） based binary molten salt. A static fusion method was used to prepare the salt and the salt underwent 1010 cycles over a temperature range between 400℃ and 600℃ in an automatic thermal cycle test rig. Variation in phase change parameters and chemical compositions during the thermal cycles were analyzed by using DSC and XRD, respectively. The results show that the methodology for the thermal stability works well and primary composition of the molten salt is lithium sodium carbonate （LiNaCO3） with the peak temperature of 499.1 ℃ and a latent heat of 365.5 J/g. The melting（freezing） temperatures of the binary molten salt show small fluctuations during repeated thermal cycling, and the phase change latent heat is reduced by 45.3 J/g. No new compositions were detected during the thermal cycling.