High thermal conductivity and high energy density compatible latent heat thermal energy storage enabled by porous Al2O3@Graphite ceramics composites

Phase change material (PCM) is an ideal heat storage material with huge latent heat and nearly constant phase change temperature, but there are serious problems in application such as leakage and low thermal conductivity. Porous ceramic is widely used in PCM packaging because of its advantages of controllable porosity and high thermal conductivity. Porous Al2O3 ceramics were prepared by foaming injection coagulation method. In order to improve the thermal conductivity of porous ceramic matrix, Porous Al2O3@Graphite Ceramics (PAGC) were prepared by sucrose decomposition. Form-Stable Phase Change Materials (FSPCMs) were prepared by adsorption of Lauric Acid/Myristic Acid (LA/MA) in PAGC by vacuum impregnation method. SEM showed that the prepared PAGC had a three-dimensional interpenetrating structure and high porosity. TEM and XPS showed that alumina skeleton were uniformly coated with graphite. After PAGC impregnated by LA/MA, the maximum PCM storage reached 62.11 wt %. The maximum latent heat of FSPCMs reaches 83.33 J/g. Thermogravimetric analysis, thermal cycling test and Fourier transform infrared spectroscopy show that the prepared FSPCMs has good thermal stability, thermal reliability, chemical stability and compressive strength. More importantly, the thermal conductivity of the prepared FSPCMs is greatly improved, reaching up to 3.73 W/mK. It is 20.72 times the original PCM, mainly due to the synergistic effect of the Al2O3 skeleton and the graphite coating to build a continuous highway for heat transfer. This study provides a practical means to greatly improve the thermal conductivity of FSPCMs, which will promote the practical application of FSPCMs.