Thermal conductivity improvement of adipic acid by the addition of AlO(OH) and AlO(OH)@SiO2 core-shell nanoparticles

Abstract

Phase change materials (PCMs) can store and release a high amount of thermal energy at various operating temperatures. They can be integrated in both thermal management and thermal storage systems. However, the low thermal conductivity of PCMs is a challenge to tackle since it adversely affects the charge and discharge times in (the aforementioned applications). The aim of this study is to improve the thermal conductivity of adipic acid, which is a non-hazardous widely-available organic PCM capable of storing ∼250 J/g of thermal energy at 150 °C. To achieve this goal, boehmite nanoparticles (AlO(OH)) and core@shell nanoparticles boehmite@silica (AlO(OH)@SiO2) are dispersed in molten adipic acid at low concentration (i.e., 0.05. 0.1, and 0.2 wt%). The thermal conductivity measured using modified transient plane source technique (MTPS) shows that the presence of AlO(OH) and AlO(OH)@SiO2 core-shell nanoparticles leads to an increase of the thermal conductivity of adipic acid by 20 % and 14 %, respectively. This enhancement of thermal conductivity is achieved without reducing the enthalpy of the phase transition based on calorimetric measurements. As shown by thermogravimetric analysis, the mass loss of adipic acid is shifted toward higher temperature upon the addition of nanoparticles. Furthermore, the subcooling in nano-PCMs is decreased by 1.3 K compared to the one in pure adipic acid. These promising results bode well for the utilization of enhanced adipic acid as a PCM in thermal energy storage application.