Novel and durable composite phase change thermal energy storage materials with controllable melting temperature

Abstract The development of high temperature phase change materials (PCMs) with great comprehensive performance is significant in the future thermal energy storage system. In this study, novel and durable Al-Si/Al2O3-AlN composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO2 source. The Al2O3 shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO2. Importantly, the crack caused by the incomplete encapsulation of the Al2O3 shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al2O3-AlN composite shell. The produced dense Al2O3-AlN composite shell could significantly improve the thermal cycling stability of composite PCMs, and thus, the thermal storage density decrease of the Al-Si/Al2O3-AlN (59.8 J/g to 77.7 J/g) was far less than that of the Al-Si/Al2O3 (118.5 J/g) after 3000 thermal cycles. Moreover, the synthesized Al-Si/Al2O3-AlN still exhibited a controllable melting temperature (571.5‒637.9 ℃), relatively high thermal storage density (105.6‒150.7 J/g), great dimensional stability and structural stability after 3000 thermal cycles. Hence, the synthesized Al-Si/Al2O3-AlN composite PCMs, as promising preferential thermal energy storage materials, can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.