纳米SiO2在低熔点熔盐中的分散对其比热容的影响

摘要

为提高低熔点熔盐Ca(NO3)2-KNO3-NaNO3-LiNO3的比热容，采用超声振荡法将低熔点熔盐与30 nm的SiO2纳米粒子复合制备出低熔点熔盐纳米流体，研究了纳米粒子对低熔点盐比热容的影响及制备过程中影响纳米粒子分散的关键因素：超声振荡时间和超声振荡频率.采用同步热分析仪( DSC)测量熔盐比热容；采用扫描电镜表征低熔点熔盐纳米流体的微观表面结构，观察纳米粒子分布情况.研究结果表明：分散均匀的SiO2纳米粒子可以提高低熔点盐纳米流体的比热容，纳米熔盐比热容平均值达到1.86 J/( g·K)左右，在200~350益温度范围内，比热容提高率为14%~22%，并通过实验验证了超声波分散法是制备熔盐纳米流体的一种稳定可靠的方法.%In order to enhance specific heat capacity of the low melting point salt ( Ca ( NO3 ) 2-KNO3-NaNO3-LiNO3 ) , low melting point salt( LMPS) nanofluid was prepared by adding SiO2 nanoparticles with size of 20 nm into the low melting point salt with using ultra-sonication. The influence of nanoparticles dispersion on enhancing specific heat of the low melting point salt was investigated by experiments. Two factors of ultra-sonication ( time for sonication and frequency ) were researched. The specific heat capacity was measured by using a differential scanning Calorimetry ( DSC ) , and the microstructures following solidification was observed by using a scanning electron microscope ( SEM) . Results show that the specific heat of the LMPS nanofluid is significantly improved, when nanoparticles disperse evenly in the LMPS nanofluid. The average specific heat of the LMPS nanofluid is 1. 868 J/( g·K ) and the enhancement of the specific heat is 14% ~22% in 200~350℃. Moreover, it is verified the fact that the ultra-sonication is a stable method of preparing LMPS nanofluid.