Abstract:

To observe the effect of nanoparticle on the thermal physical properties of the low melting point eutectic mixed nitrate salt. In this study 1% (mass) SiO₂ nanoparticles with the average size of 20 nm were doped into the mixed salt[Ca(NO₃)₂·4H₂O-KNO₃-NaNO₃-LiNO₃] to obtain molten-salt nanocomposites at different dispersion condition by the high temperature melting dispersion method. Specific heat capacity and thermal diffusivity of the nanocomposites were analyzed by differential scanning calorimeter (DSC) and laser flash apparatus (LFA). Then the thermal conductivity was gotten. The results show that at the stirring rate of 600 r/s the thermal physical properties of the molten-salt nanocomposites vary with the mixing time (15, 45, 90, 120 and 150 min). At the mixing time of 45 min, the thermal physical properties of the molten-salt nanocomposites reach the optimum enhancement. The average enhancement of the specific heat capacity, thermal diffusivity and thermal conductivity was 11.5%, 12.9%, and 26.4%, respectively. The scanning electron microscope (SEM) found that a large number of special nanostructures (resembling chain-like nanostructures) existed on the surface of solid molten-salt nanocomposites. The special nanostructures with large specific surface area and high surface energy may enhance the specific heat capacity and thermal conductivity of the molten salt nanocomposites.

Key words: molten salt, nanoparticle, molten-dispersion, thermal physical properties, nanostructure

摘要：

为探究纳米粒子对低熔点混合硝酸盐热物性的影响规律，采用高温熔融分散法将平均粒径20 nm的SiO₂纳米粒子以1%（质量）比例直接分散到混合熔盐[Ca（NO₃）₂·4H₂O-KNO₃-NaNO₃-LiNO₃]中得到不同分散条件下的熔盐纳米复合材料。采用同步热分析仪（DSC）与激光闪射仪（LFA）测量熔盐纳米复合材料比热容与热扩散系数，进而得到热导率。分析发现，600 r/s搅拌速率下熔盐纳米复合材料热物性随分散时间（15，45，90，120和150 min）发生明显变化。比热容、热扩散系数和热导率在分散45 min时提高率最大，平均提高率分别为11.5%，12.9%和26.4%。扫描电镜（SEM）观察到熔盐纳米复合材料表面有大量特殊结构（类似于链状或条状）存在。这些具有高比表面积和表面自由能的特殊结构可能是熔盐纳米复合材料热物性提高的关键。

关键词: 熔盐, 纳米粒子, 熔融分散, 热物性, 微观结构