•Micro-encapsulated phase change material (MEPCM) for middle-high temperature applications are achieved.•The MEPCM is composed of oxide shells and Zn-Al alloy core.•The MEPCM exhibits a phase-change ...temperature of 437–512 °C and latent heat of 117 J g−1.•The MEPCM composites exhibits excellent durability up to100 heating and cooling cycles.
Thermal energy storage (TES) that utilizes renewable energy and industrial waste heat has recently attracted attention. For the development of TES technology, latent heat storage (LHS) technology using phase change materials (PCMs) is necessary. Covering a PCM with a thermally and chemically stable shell to form a microencapsulated PCM (MEPCM) expands applicability. In this study, for the first time, the authors report the microencapsulation of Zn-30 wt%Al alloy, a new PCM for middle-high temperature (400–500 °C) applications. The microencapsulation process was conducted in two main steps, viz. formation of an AlOOH-based shell on the PCM particles by boehmite treatment and heat-oxidation treatment in an O2 atmosphere to form an oxide shell. Furthermore, composites were synthesized by sintering the MEPCMs with glass frit (GF) as the sintering agent. The prepared MEPCM had multilayers with 500 nm thickness of ZnO and 300 nm thickness of Al-oxide. It exhibited a phase-change temperature of 437–512 °C and latent heat of 117 J g−1. About 75% of the MEPCM-particles retained their spherical shape after 100 melting and solidification cycles, in addition, the MEPCM-GF composite completely retained their shape and thermal energy storage performances after 100 melting and solidification cycles. Therefore, the authors believe that the MEPCMs and their composites described in this study have the potential to develop new applications involving thermal energy storage, transportation, and management.
High temperature phase change materials (PCMs) are drawing increasing attentions globally due to their high latent heat storage ability for solar thermal energy. Encapsulation of PCMs is an effective ...method for preventing the leakage of liquid PCM during heat storage, which makes PCMs easier to handle. In this paper, the synthesis of microencapsulated PCM (MEPCM) with Al-25 wt% Si core (spheres, average diameter 36 µm) and Al2O3@Cu multilayered shell is reported, which works at temperature up to 500 °C. The homogeneous and effective composite shell is synthesized in multi-steps: First, a boehmite (AlOOH) shell is formed by boiling treatment in water, which is then transferred to Al2O3 shell by heating at 500 °C. Second, the Al2O3 covered particles are etched with HCl solution. Third, electroless plating of Cu layer is carried out to form the multilayered MEPCM. The surface morphology, cross-sectional structure, and thermal durability and stability of the MEPCM are investigated. The core/shell Al-25 wt%Si@Al2O3@Cu particles can maintain their integrity even after 100 melting–solidification cycles with a low breakage ratio of about 1.7%. The results indicate that as-prepared MEPCM can be used for high temperature thermal energy storage such as solar thermal power generation. The success of Cu plating on spherical particles can also be applied to fabricate other Cu coated PCMs due to expected high thermal conductivity of Cu, especially for the low temperature ones such as organic PCMs.
SEM view and schematic of core/shell Al-25 wt% Si@Al2O3@Cu MEPCM particle. Display omitted
•MEPCM with Cu coated Al2O3 bilayer shell was prepared.•Al-25 wt% Si alloy with a melting point of 577 °C was used as core PCM.•Electroless plating of Cu was formed on Al2O3 shelled Al-25 wt% Si alloy.•MEPCM showed two melting points at 518 °C (Al-Si-Cu) and 570 °C (Al-Si).•MEPCM showed good stability and durability in oxygen atmosphere.
•New heat storage pellets mainly composed of microencapsulated phase change material (MEPCM), were fabricated.•The core of the MEPCM is Al-25mass%Si, which acts as a PCM; the shell is Al2O3.•The ...pellets have a melting temperature of 577 °C, 108–122 Jg−1 of latent heat, and excellent cyclic durability.•The developed pellets represent great promise for high-temperature thermal energy storage systems.
Latent heat storage using a metallic phase change material (PCM) is an attractive option for high-temperature thermal energy storage. However, there are serious technical barriers to applying a metallic PCM to practical applications, mainly caused by its high corrosivity. This study reports the fabrication of a pellet-type PCM composite, mainly composed of a microencapsulated metallic PCM, as a potentially viable solution to this issue. This microencapsulated PCM (MEPCM) has a core composed of Al-25 mass% Si, which acts as a PCM. Its shell is composed of Al2O3 (or a precursor of Al2O3), and grass frit was used as a sinter agent. The composites were fabricated by mixing the MEPCM with a sintering agent, pelletizing, and sintering. The PCM composites exhibited a melting point of ~577 °C and a latent heat of 108–122 J g−1. The thermal conductivities of the PCM composites were in the range of 2.16–3.20 W m−1 K−1. The cycling performance demonstrated the good durability of the composites. There were no significant changes in the shape and chemical composition of the pellets, even after 300 cycles of melting and freezing tests. These results indicate that the concept of pellet-type composites using MEPCM developed in this study will overcome the technical barriers to utilizing metallic PCMs. Thermal energy storage structures in various shapes could be fabricated via the method for fabricating PCM composites proposed in this study. This concept therefore shows substantial promise for application in high-temperature thermal energy storage systems.
CO
methanation is a promising technology to enable the use of CO
as a resource. Thermal control of CO
methanation, which is a highly active exothermic reaction, is important to avoid thermal runaway ...and subsequent degradation of the catalyst. Using the heat storage capacity of a phase change material (PCM) for thermal control of the reaction is a novel passive approach. In this study a novel structure was developed, wherein catalysts were directly loaded onto a micro-encapsulated PCM (MEPCM). The MEPCM was prepared in three steps consisting of a boehmite treatment, precipitation treatment, and heat oxidation treatment, and an impregnation process was adopted to prepare a Ni catalyst. The catalyst-loaded MEPCM did not show any breakage or deformation of the capsule or a decrease in the heat storage capacity after the impregnation treatment. MEPCM demonstrated a higher potential as an alternative catalyst support in CO
methanation than the commercially available α-Al
O
particle. In addition, the heat storage capacity of the catalyst-loaded MEPCM suppressed the temperature rise of the catalyst bed at a high heat absorption rate (2.5 MW m
). In conclusion, the catalyst-loaded MEPCM is a high-speed, high-precision thermal control device because of its high-density energy storage and resolution of a spatial gap between the catalyst and cooling devices. This novel concept has the potential to overcome the technical challenges faced by efficiency enhancement of industrial chemical reactions.
In Japan, High Speed Rail (HSR) extended its network in 2011 and 2015, and Low Cost Carriers (LCC) entered into the domestic airline market in 2012. We compared the effects of the extension of the ...HSR network and the entry of LCCs on the airfares of the incumbent Full Service Carriers (FSC). We conducted Difference in Differences analysis with passenger level data to evaluate these market changes, and found that the effects of the HSR extension on FSC's airfares were consistently negative and larger in the short haul markets, while the effects of the entry of LCCs were inconsistent. HSR seems to be a stronger competitor than LCC to FSC and this finding could be affected by capacity, which is large for HSR while small for the LCCs.
•We compared the impacts of the extension of HSR network and the entry of LCC on the airfares of the incumbent FSC in Japan.•DID analysis with the individual passenger level data was conducted to evaluate the impacts.•We could conclude that HSR was a stronger competitor for FSCs than LCCs.
Post-hepatectomy bile leakage (PHBL) is a potentially fatal complication that can arise after hepatectomy. Previous studies have identified obesity as a risk factor for PHBL. In this study, we ...investigated the impact of sarcopenic obesity on PHBL in hepatocellular carcinoma (HCC) patients. In total, we enrolled 409 patients who underwent hepatectomy without bilioenteric anastomosis for HCC between January 2010 and August 2021. Patients were grouped according to the presence or absence of PHBL. Patient characteristics, including body mass index and sarcopenic obesity, were then analyzed for predictive factors for PHBL. Among the 409 HCC patients included in the study, 39 developed PHBL. Male sex, hypertension, cardiac disease, white blood cell counts, the psoas muscle area, and visceral fat area, and intraoperative blood loss were significantly increased in the PHBL (+) group compared with the PHBL (-) group. Multivariate analysis showed that the independent risk factors for the occurrence of PHBL were intraoperative blood loss greater than or equal to370 mL and sarcopenic obesity. Our results show that it is important to understand whether a patient is at high risk for PHBL prior to surgery and to focus on reducing intraoperative blood loss during surgery for patients with risk factors for PHBL.
The purpose of this study was to prepare an Al/Al2O3 core–shell microencapsulated phase-change material (MEPCM) for a high-temperature thermal energy storage (TES) system. Al (melting temperature: ...660 °C) was selected as a raw material for use as a phase change material (PCM). The MEPCM was prepared in two steps: (1) the formation of an AlOOH precursor shell on the PCM microspheres via boehmite treatment in boiled distilled water and (2) heat oxidation treatment in an O2 atmosphere to form a stable Al2O3 shell. The effects of the heat oxidation temperature on the shell morphology, shell structure, heat capacity, and cyclic durability of the prepared MEPCMs were examined. The resultant MEPCM was a core–shell-type structure composed of a stable α-Al2O3 shell and an Al core. The melting temperature of the MEPCMs was close to that of pure Al, and small supercooling of approximately 10 K was observed. Although the increase of the heat oxidation temperature reduced the heat-storage capacity of the MEPCMs (273–301 J g−1) as larger amounts of Al were consumed to form α-Al2O3, the repetition durability of the developed specimens was improved by increasing the heat-treatment temperature. In conclusion, the Al-based MEPCM is a potential candidate for high-temperature TES applications owing to its high melting temperature, high thermal storage capacity, and small degree of supercooling.
•Al-based microencapsulated phase change materials (MEPCMs) were developed.•The effect of heat oxidation temperature for preparing MEPCM on the structure and the performance was investigated.•These MEPCMs exhibited high thermal storage capacity about 273–301 J g−1.•They are good candidates for high-temperature thermal energy storage application.
Energy efficiency is fundamental in the steel industry. Latent heat storage (LHS) systems with phase change materials (PCM) are attractive technologies for the recovery and utilization of heat, ...especially for the development of high-temperature thermal energy storage system. This paper describes fabrication of LHS pellets for high-temperature applications using metallic microencapsulated PCM (MEPCM). The LHS pellets consist of Al–Si PCM parts and an Al2O3 matrix. The pellets were fabricated by mixing MEPCM with sinterable alumina. The powder mixture was then pelletized and sintered at different pressures and atmospheric conditions, respectively. Some MEPCM in the pellets remained spherical after being sintered at 1000°C, a high-temperature condition above the PCM melting temperature. All fabricated pellets exhibited latent heat of PCM at the melting point of the PCM, about 577°C. The maximum value of latent heat was 73.5 J g−1. This was observed for the LHS pellet pelletized at 20 MPa and sintered under O2 atmosphere. Therefore, this study presents a great material for high-temperature thermal energy storage systems in the steel industry.
Nanoscale Young's modulus mapping of the cross-section of electrode composite films used in lithium ion batteries was carried out using bimodal atomic force microscopy. Clear difference in Young's ...modulus was observed between the particles of active materials and matrix of conductive additives/binders in the composites of LiCoO2-based positive and graphite-based negative electrodes. Interestingly, there were a few particles showing significantly reduced Young's modulus in the 100% state-of-charge positive electrode although such particles were not present in the pristine electrode.
Display omitted
•A coin cell was fabricated from a LiCoO2 positive and graphite negative electrode.•Bimodal AFM was applied for the electrodes after the charge-discharge cycle.•Nano-mechanical mappings of their cross-sections were successfully demonstrated.
Thermal energy storage using phase change materials (PCMs) has been world-widely accepted as an effective technology for energy saving. In this study, Micro-Encapsulated PCMs (MEPCMs) were developed ...from Al-Si alloys, in which four kinds of Al-Si microspheres with different Al-Si compositions: Al-12%Si, Al-17%Si, Al-20%Si, and Al-30%Si (mass%) were encapsulated by two facile steps for controlling heat storage property. First, boehmite film was formed over the Al-Si microspheres as a precursor shell during boiling in distilled water. Subsequently, the boehmite-coated particles were oxidized by pure oxygen at the high temperatures to ensure the formation of a stable Al2O3 shell. Three different temperatures, 1100 °C, 1150 °C, and 1200 °C, were chosen to study the effect of temperature on the product; the shell morphology, structure, and latent heat storage capacity. Interestingly, the results revealed an increase in MEPCM thermal storage capacity with decreasing Si content and lowering the temperature. The MEPCM melting point was almost identical to its eutectic temperature at ~577 °C, in contrast the larger supercooling was observed for samples with the higher Si content. The cyclic durability of MEPCM was also evaluated through repeated heating and cooling processes in air. The obtained results showed no significant change in both MEPCM structure and thermal storage capacity. It indicated a good repetition durability of MEPCMs oxidized at high temperatures. In conclusion, the Al-Si microencapsulated PCMs appealed great potential as MEPCMs for use in high-temperature thermal energy applications.
•Al-Si-based microencapsulated phase change materials were developed.•The effect of %Si content in raw materials on thermal energy storage was optimized.•These products exhibited high thermal storage capacity about 300 J g−1 and high cyclic durability.•They are good candidates for high-temperature thermal energy storage application.
PDF
