Abstract:

In order to study the effects of SiO₂ nanoparticles content on the specific heat capacity and thermal conductivity of nano-SiO₂/NaNO₃-KNO₃/EG composite heat storage materials, a series of nano-SiO₂/NaNO₃-KNO₃/EG composites were prepared by mechanical dispersion method. NaNO₃-KNO₃ and SiO₂ nanoparticles with different mass fractions (0.1%, 0.5%, 1%, 2%, 3%) were used as heat storage materials and expanded graphite (EG) was used as matrix material. Then the specific heat and the thermal diffusivity of composite heat storage materials were measured, and the microstructural characteristics were analyzed by scanning electron microscopy (SEM). The results show that adding 1% of SiO₂ nanoparticles to the composite can significantly affect its average specific heat capacity and thermal conductivity, with a measured value of 3.92 J/(g·K) and 8.47 W/(m·K), respectively, which are 1.37—2.17 times and 1.7—3.2 times higher than that of the other similar composites. This is owed to its high density network nanostructure with the large specific surface area and high surface energy which can improve the specific heat capacity and thermal conductivity.

Key words: binary nitrate, silica, nanoparticles, composites, specific heat capacity, thermal conductivity

摘要：

为了得到SiO₂纳米粒子含量对SiO₂/NaNO₃-KNO₃/EG复合蓄热材料比热容和热导率的影响，通过机械分散法，采用NaNO₃-KNO₃和不同质量分数（0.1%，0.5%，1%，2%，3%）的SiO₂纳米粒子所形成的熔盐纳米材料作为蓄热材料，膨胀石墨（EG）作为基体材料，制备出纳米SiO₂/NaNO₃-KNO₃/EG复合材料。对复合材料的比热容和热导率进行了测量，同时用扫描电镜对其微观结构特征进行了分析。结果表明，SiO₂纳米粒子的质量分数为1%时，复合材料的平均比热容和热导率分别为3.92 J/(g·K)和8.47 W/(m·K)，与其他纳米SiO₂添加比例相比，其比热容和热导率分别提高了1.37～2.17倍和1.7～3.2倍。这是由于复合材料表面会形成高密度的网状结构，这种具有较大比表面积和高表面能的特殊纳米结构可以提高复合材料的比热容和热导率。

关键词: 二元硝酸盐, 二氧化硅, 纳米粒子, 复合材料, 比热容, 热导率