Takahiro Nomura

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‐Al 2 O 3 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.