Latent heat storage composites composed of Al‐Si microencapsulated phase change material and alumina matrix

Abstract

Latent heat storage (LHS) using phase change materials (PCMs) is expected for application to heat utilization at high‐temperature because it can provide a heat source of high density and constant temperature. Even among PCMs, metals/alloys are promising for high‐temperature operation. However, metals and alloys PCM are concerned about corrosion reactions with structural materials. As a result, micro‐encapsulated PCMs (MEPCMs) have been created in which the surface of alloy PCM is encased in a stable oxide coating. Since the surface of MEPCM is an oxide, the creation of structures with the function of LHS in a variety of shapes by combining MEPCM with sintering aids is also possible. In this study, composite PCMs were prepared by combining Al‐25 mass% Si MEPCM with fine α‐Al2O3 particles as a sintering aid. Consequently, PCM composites containing 70‐90 vol.% of the MEPCM and heat‐treated at 1200°C or 1300°C were successfully fabricated. In particular, a high heat storage density of 0.47 GJ m−3 was obtained under conditions containing 90 vol.% of the MEPCM and a heat treatment temperature of 1200°C, which is 1.6‐fold higher than that of existing sensible heat storage materials. Additionally, the composite PCM retained its shape and the latent heat capacity even after 300 cycles of cyclic testing. Thus, the high heat storage density and high durability of the composite PCM are expected to further promote the expansion of high‐temperature heat utilization in future studies.

Shell-Driven Localized Oxide Nanoparticles Determine the Thermal Stability of Microencapsulated Phase Change Material

“…Cross-sectional observations (Figure S10b) revealed that the MEPCMs maintained their morphology after the 1000 cycles, albeit with a slight reduction in Δ H m and Δ H s values to 25 and 24 J·g –1 , respectively. In comparison, previous research on the Al-25 wt %Si@α-Al 2 O 3 MEPCM composite established a benchmark for thermal durability over 300 cycles ,, a threshold that this study surpassed. Notably, in composite form, Al-25 wt %Si exhibits a considerably higher latent heat energy than Sn, registering at 120–160 J·g –1 .…”

“…Previous studies demonstrated the successful creation of microencapsulation PCMs (MEPCMs) with an α-Al 2 O 3 shell making on metal/alloy PCM systems, achieved through a sequential process of chemical coating with an AlOOH layer followed by a heat-oxidation treatment in an O 2 atmosphere. The MEPCM technology has been excellent-selectable metals , or their alloys − for corrosion resistance PCMs, capable of storing ∼1 GJ·m –3 latent heat, exhibit compatibility with catalyst integration, versatility in composite molding, − and a proven durability over thousand cycles of thermal stability tests. , Nevertheless, the practical extension of the current method remains an endeavor, with the persistent phenomenon of supercooling and its underlying mechanism yet to be comprehensively elucidated.…”