Abstract:

Melt temperature, fusion heat and decomposition temperature are three fundamental thermo-physical properties of molten salt. Based on NaBr (AR), KBr (AR), CaBr₂ (AR) and LiBr (AR) 25 quaternary bromides with different average diameter (10 nm, 20 nm and 50 nm) and mass concentration of SiO₂ nanoparticles were prepared. Differential scanning calorimetry (DSC) was employed to investigate melt temperature, fusion heat and decomposition temperature of the 25 quaternary bromides with SiO₂ nanoparticles. Experimental results showed that the melting point of the nano-quaternary bromides decreased first and then increased subsequently with the increase of SiO₂ nanoparticles. The fusion heat increased first and then decreased, which varies greatly with the increase of SiO₂ nanoparticles. As the mass concentration of the 10 nm SiO₂ nanoparticles is 1.5%, nano-quaternary bromides reached a maximum fusion heat of 47.06 J·g^-1, which increased by 89.6%. As the mass concentration of the 10 nm SiO₂ nanoparticles is 0.7%, nano-quaternary bromides reached a maximum decomposition temperature of 876.3℃.

Key words: quaternary bromides, SiO₂ nanoparticles, preparation, phase change, melting point, fusion heat, decomposition temperature, thermodynamic properties

摘要：

熔点、熔化潜热和分解温度是熔盐传热蓄热材料的重要热物性参数。以分析纯NaBr、KBr、CaBr₂和LiBr配制四元溴化盐，分别将颗粒平均直径为10、20、50 nm的纳米SiO₂颗粒按一定含量分散入所配制四元溴化盐中配制得到25种不同含量和粒径的纳米SiO₂溴化盐，利用DSC法研究添加纳米SiO₂含量和粒径对四元溴化盐熔点、熔化潜热及分解温度的影响。结果表明，随着纳米SiO₂含量的增大，溴化盐的熔点先降低后升高，但变化范围较小；熔化潜热先升高后逐步降低，变化较大。添加10 nm SiO₂颗粒含量为质量分数1.5%时，最大熔化潜热为47.06 J·g^-1，提高89.6%；添加10 nm SiO₂颗粒含量为质量分数0.7%时，最高分解温度为876.3℃。

关键词: 四元溴化盐, 纳米SiO₂, 制备, 相变, 熔点, 熔化潜热, 分解温度, 热力学性质