Form stable binary chlorides/expanded graphite composite material with enhanced compressive strength for high temperature thermal storage

Abstract

Abstract In this study, series of KCl-LiCl /expanded graphite (EG) composite phase change materials (CPCM) with different EG contents for high temperature thermal energy utilization were prepared by melting impregnation method. The mixture of KCl-LiCl was served as the phase change material (PCM) for thermal energy storage, while EG was acted as not only the matrix to prevent the leakage of PCM but also the heat transfer promoter to improve the thermal conductivity of PCM. The microstructures, phase transition properties, thermal conductivity and thermal stability of different samples were evaluated, and the results showed that KCl-LiCl was wrapped in the network structure of EG without agglomeration. The experimental latent heat of CPCMs were close to the theoretical value and there was no remarkable variation in melting point. The highest thermal conductivity of CPCMs was 12.05 W/(m•K), which is 41.6 times higher than that of KCl-LiCl. Moreover, the CPCMs whose EG content higher than 20 wt% showed good thermal stability after 100 thermal shock cycles. Furthermore, when 10 wt% SiC particles were added into 80KCl-LiCl/20EG, the compressive strength of 80KCl-LiCl/20EG/10SiC was enhanced to 9 MPa, which is 1.8 times higher than that of 80KCl-LiCl/20EG.