Al–Ni alloy-based core-shell type microencapsulated phase change material for high temperature thermal energy utilization

Abstract

Latent heat thermal energy storage (LHTES) using alloy-based phase-change materials (PCMs) is a promising technique for stabilizing the power supply of grid-connected renewable energies. In particular, recently developed alloy-based microencapsulated PCMs (MEPCMs) are attracting considerable attention owing to their ease of handling and ability to overcome the problems of corrosion and melting leakage experienced by alloy PCMs. To expand high-temperature LHTES, more MEPCMs need to be developed. In this study, an MEPCM was developed using Al-5 wt.%Ni alloy (melting point 640°C). Microencapsulation was performed in two steps: 1) Al hydroxide layer formation on the surface of PCM particles by boehmite treatment in boiling water for 1 h or 3 h and 2) Al 2 O 3 shell formation by heat oxidation treatment in an O 2 atmosphere. The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. The sample after 1 h of boehmite treatment and heat oxidation treatment had melting and solidification latent heat capacities of 241 J g –1 and 251 J g –1 , respectively. The developed MEPCM maintained its original shape and high latent heat capacity, even after 100 cycles of melting and solidification. The developed Al–Ni alloy-based MEPCM is expected to be applied to next-generation LHTES, in which a large-scale and ultrafast heat exchange system is employed in a small space by cascade configuration with other MEPCMs with different melting points. In addition, the formation of the Al–Ni alloy core/α-Al 2 O 3 shell structure was investigated thermodynamically, providing insights that will promote the development of Al- X alloy-based MEPCMs in the future. • Al–Ni alloy based microencapsulated phase change materials (MEPCMs) were developed. • The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. • The MEPCM exhibited high thermal storage capacity about 241 - 251 J g -1 . • The MEPCM had melting temperature of 640°C. • They are good candidates for high-temperature thermal energy storage application.