添加纳米SiO_2对四元溴化盐相变热物性的影响

Improving phase change thermal properties of quaternary bromides by adding SiO_2 nanoparticle

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SiO_2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SiO_2溴化盐,利用DSC法研究添加纳米SiO_2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SiO_2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 SiO_2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 SiO_2颗粒含量为质量分数0.7%时,最高分解温度为876.3℃。

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 Li Br（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℃.