氯化盐/陶瓷定形复合相变材料的制备和热物性研究

The preparation and thermophysical properties of chloride/ceramic-shaped stabilized composite phase-change materials

为了开发一种低成本、热性能好的蓄热材料,本文选用氯化盐(CaCl_(2)-NaCl-KCl)作为相变材料,氧化铝(α-Al_(2)O_(3))为载体材料,膨胀石墨(EG)为导热增强剂,通过混合烧结法制备出CaCl_(2)-NaCl-KCl/α-Al_(2)O_(3)/EG定形复合材料。基于X射线衍射(XRD)分析可知,氯化盐、氧化铝、EG在样品烧结过程中仅仅是物理混合,不发生化学反应;通过扫描电子显微镜(SEM)观察微观结构发现,氯化盐和氧化铝均匀混合并附着在EG的孔隙中,EG形成的孔隙有利于防止熔盐液体泄漏。通过对复合材料的热物性测量,结果表明,CaCl_(2)-NaCl-KCl/α-Al_(2)O_(3)/EG复合材料在相变前(150~450℃)的比热容为1.35 J/(g·K),导热系数为5.03 W/(m·K);相变后(520~640℃)的比热容为1.43 J/(g·K),导热系数为3.18 W/(m·K)。与纯氯化盐相比,复合材料的熔点基本不变,在100~700℃使用范围里,复合材料的蓄热密度为902.5 kJ/kg,较纯氯化盐增加了8.3%。所制备的CaCl_(2)-NaCl-KCl/α-Al_(2)O_(3)/EG复合材料,使用过程中始终保持固定形状,比热容和导热系数有较大提高,本研究为高温储热领域提供了一种可供选用的低成本且综合性能好的储热材料,为推动氯化盐在高温储热领域的实际应用提供了筛选依据。

This study aimed to develop a type of low-cost heat-storage material with good thermal performance.Chloride salt(CaCl_(2)-NaCl-KCl)was selected as the phase-change material,alumina(α-Al_(2)O_(3))was used as the matrix material,and expanded graphite(EG)was used as a thermal conductivity enhancer.A mixed sintering method prepared the CaCl_(2)-NaCl KCl/α-Al_(2)O_(3)/EG stable composite material.Based on X-ray diffraction results,chloride,alumina,and the EG physically mixed,but no chemical reaction occurred.Scanning electron microscopy was used to observe the microstructure of the EG.Chloride and alumina were evenly mixed and adhered to the pores of the EG.The pores formed by the EG helped to prevent liquid leakage.The results showed that the melting point of the composite was almost the same as that of chloride.By measuring the thermal properties of the composite material,the results showed that the specific heat capacity of the CaCl_(2)-NaCl-KCl/α-Al_(2)O_(3)/EG composite material was 1.35 J/(g·K)before the phase change(150~450℃),and the thermal conductivity was 5.03 W/(m·K).After the phase change(520~640℃),the specific heat capacity was 1.43 J/(g·K),and the thermal conductivity was 5.03 W/(m·K).Compared with the chloride salt,the melting point of the composite material essentially remained unchanged.In the application range of 100~700℃,the composite material's heat storage per unit mass was 902.5 J/g,increasing 8.3%compared with the pure chloride salt.In the prepared CaCl_(2)-NaCl-KCl/α-Al_(2)O_(3)/EG composite material,the chloride salt avoided direct contact with the container during use,thereby reducing its corrosiveness.Concurrently,the thermal performance greatly improved.This study provides an alternative low-cost and good comprehensive performance heat-storage material for high-temperature heat-storage contexts.It provides an experimental basis for promoting the practical application of chloride in high-temperature heat-storage environments.