平成 28 年度 エネルギー・マテリアル融合領域研究センター 若手研究員等研究助成 報告書
研究テーマ名：相変化物質（Phase Change Material: PCM） 研究室名：エネルギーメディア変換材料のマイクロカプセルの開発

氏名：盛 楠1.研究成果の概要
1.1 Introduction
Thermal energy storage (TES) involves the storage of both sensible and latent heat, which has recently attracted
increasing interest related to thermal industrial applications such as solar thermal technologies, aerospace applications, andsteel-making industry. Energy storage is essential whenever there is a mismatch between the supply and consumption ofenergy. One of the solutions proposed is using latent heat of phase change materials (PCMs). PCMs with their high thermal
storage density at almost isothermal conditions and their availability at wide range of phase transitions promote an effectivemode of storing thermal energy. In last decade, the encapsulation of the PCM has attracted interest as a barrier to leakage ofliquid PCM during heat storage. An essential advantage of the encapsulated PCM is prevent the leakage of liquid PCM
during heat storage. Meanwhile, the encapsulation could provide more advantages such as a large heat transfer area, barriers
against harmful environmental reactions, improves thermal and mechanical stability, and provides structural stability and easy
handling. In this research, We investigated the preparation of micro-encapsulated PCMs (MEPCMs) where the PCM
consisted of Al-25 wt.% Si microspheres and the capsule of Al2O3.
1.2 Experiment
The raw material for the preparation ofAl-25 wt.% Si spherical particles (purity 99.0 %)was purchased from Hikari Material Industry Co.
Ltd.. The particles were prepared by a spinning disk
atomisation method, had an average diameter of
36.3 μm, melting point at 577 oC and latent heat of432 J·g-1. The MEPCM of Al-25 wt.% Si alloy wasprepared by using two steps: First is boehmite
treatment in boiling distilled water to form anAlOOH shell on the surface of the alloy. Secondly,
a stable Al2O3 shell was formed on the Al-25 wt.%
Si core by heat-oxidation treatment in an oxygen
atmosphere.

The

experimental

schematically summarized in Fig. 1.

procedure

isFig. 1 Experiment procedure to prepare MEPCMs. TheMEPCMs were prepared by two steps: (1) precursor of Al2O3shell by boehmite treatment, (2) Al2O3 shell preparation byheat-oxidation.

1.3 Results
Fig. 2 shows EDS elemental mapping analysis of raw
material (Al-25 wt.% Si). The Al and Si element could be clearlyobserved on the spherical shape of raw material, and no oxygen
could be found on the surface. Fig. 3 shows EDS elemental
mapping analysis of the samples after boehmite treatment. The Aland Si element show the similar images, and the oxygen element
could be observed on the surface with slight color. This indicatedthe AlOOH precursor of Al2O3 shell was formed during this step.
To synthesis compact and stable Al2O3 shell, the heat-oxidation
step is necessary. Fig. 4 shows EDS elemental mapping analysis

Fig. 2 EDS elemental mapping of the Al-25
wt.% Si raw material.

of the Al-Si partials subjected to heat-oxidation after boehmite treatment. The spherical Al-Si particles showless Si on the surface, and the oxygen element uniformly covered the whole particle. EDS image of the O
element show more dense color than the O element observed in Fig. 3, this indicated more O element could beobserved on the particle surfaces after heat-oxidation. The surface
morphology of the particles after heat-oxidation was also changed.
Some embossment could be observed on the surface. The formationof Al2O3 shell could be divided in three stages. In stage 1, fromroom temperature to about 580 oC, the dehydration of AlOOH,formed during the boehmite treatment, took place. A fast oxidationof Al occurred in Stage 2, from 580 oC to 690 oC, above the Al-Si
eutectic melting temperature (577 oC). The oxygen was supplied tothe Al-Si core through shell cracks that formed following the rapidovolume expansion of the core. And stage 3, from 690 C to the end ofFig. 3 EDS elemental mapping of thesamples after boehmite treatment.

oxidation, corresponded to further oxidation of Al contained in the
inner core, and the cracks formed during stage 2 was self-repaired.
The embossments observed in Fig. 4 corresponding to theself-repaired parts.
4 Conclusions
An MEPCM consisting of Al-25 wt% Si particles of 36.3 μm
average diameter core/ PCM and Al2O3 shell was successfully
developed. The MEPCM showed characteristics such as high heatstorage density, high thermal responsibility, and high endurance forFig. 4 EDS elemental mapping of thesamples after heat-oxidation.

heat storage or transport media, for high temperature applications.
2.研究成果発表リスト (口頭発表・論文等)
①既発表
国内会議：
(1) Nan Sheng, Takahiro Nomura, and Tomohiro Akiyama. Microencapsulated Phase Change Material (PCM) for
High-temperature Thermal Energy Utilization. 5th Hokkaido University – Seoul University Joint Symposium,
November 25,2016.
学術論文：(1) Takahiro Nomura and Nan Sheng, et al. Microencapsulated phase change materials with high heat capacity and highcyclic durability for high-temperature thermal energy storage and transportation. Applied Energy, 188 (2017) 9-18.
(2) C. G. Han, C. Zhu, and N. Sheng, et al. Enhanced cycling performance of surface-doped LiMn2O4 modified by aLi2CuO2-Li2NiO2 solid solution for rechargeable lithium-ion batteries. Electrochimica Acta, 224 (2017) 71-79.
(3) C. G. Han, C. Zhu, and N. Sheng, et al. A facile one-pot synthesis of FeOx/ carbon/ graphene composites as superior
anode materials for lithium-ion batteries. Electrochimica Acta, 235 (2017) 88-97.
②発表予定
Elsevier 投稿予定
3.研究結果のプロジェクト研究等への活用・展開予定
More stable and applicable MEPCMs should be achieved. Some reagent which could promote the growth of theprecursor of Al2O3 shell will be investigated. Research on the condition of heat-oxidation process is also
important.
4.特記事項
注：全体で 2 ページ以内であれば枠の大きさを自由に変更可。