研究者詳細 - 三浦　飛鳥

論文 - 三浦　飛鳥

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回転型トライボエレクトリック発電機の開発査読有り

上原脩, 児嶋広紀, 三浦飛鳥, 矢吹智英, 宮崎康次

熱工学コンファレンス講演論文集 ( 一般社団法人日本機械学会 ) 2021 ( 0 ) 0116 2021年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

<p>The triboelectric generator consists of triboelectric charging and electrostatic induction. The generator is characterized by its light weight, flexibility to use a wide range of materials, and the ability to achieve miniaturization through microfabrication technology. Extracting the static electricity generated in our daily lives as electric power can be considered as a sustainable energy source for the future. In this study, we will measure the amount of power generated when the number of blades, rotational speed, torque, material, and size of the generator are varied, and discuss the power generation mechanism in terms of capacitance and external load.</p>

DOI： 10.1299/jsmeted.2021.0116

CiNii Research

Experimental Analysis of Rotary Freestanding Triboelectric Nanogenerators 査読有り国際誌

Chatar K., Uehara S., Kojima H., Miura A., Yabuki T., Miyazaki K.

2021 IEEE 20th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, PowerMEMS 2021 84 - 87 2021年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this paper, we design, develop, and test rotary freestanding triboelectric nanogenerators (TENGs) for harvesting energy from mechanical rotation. The objective is characterizing the fundamental processes involved in energy harvesting and obtaining a thorough understanding of the development process for TENG devices. An experimental testbed was built for mounting, testing, and analyzing the TENG electrical characteristics. To test the electrical performance, several versions of TENGs were created with varying design and measurement parameters. We measured the effects of changing the diameter (50, 75, 100mm) and changing the number of blades (4, 8 and 12-blade). We also analyzed the effect of changing RPM, applied torque and electrode materials on the output performance produced. Additionally, we also measured and characterized the performance of thin-film MEMS deposition techniques by depositing an Aluminum Oxide (Al2O3) layer and Aluminum (Al) electrode layer for the TENGs. The 12-blade 100mm TENG produced an open circuit voltage of 180VOC and a short circuit current of 10μA at 1000RPM and 0.04Nm applied torque. The Al2O3 thin-film blocking layer exhibited a two-fold increase in current and a three-fold increase in voltage output for the tested TENG devices.

DOI： 10.1109/PowerMEMS54003.2021.9658403

Scopus

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Thermal transport properties of Ni-Co-based superalloy 査読有り国際誌

Miura A., Osada T., Kawagishi K., Uchida K.I.

AIP Advances 10 ( 12 ) 2020年12月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We report systematic measurements of thermal transport properties of a Ni-Co-based superalloy at temperatures ranging from room temperature to around 800 K. In this temperature range, the thermal diffusivity and conductivity of the superalloy monotonically increase with an increase in the temperature, while the specific heat capacity is almost temperature-independent. We found that the observed thermal conductivity of the Ni-Co-based superalloy is higher than the electronic thermal conductivity expected from the Wiedemann-Franz law, indicating the substantial contribution of phonon thermal conductivity. The temperature dependence of the phonon thermal conductivity for the Ni-Co-based superalloy was observed to be weaker than that for other Ni-based alloys, which can be qualitatively explained by enhanced phonon scattering due to small γ′-phase precipitates in the superalloy. This result suggests possible tuning of the thermal conductivity of the superalloy based on phonon transport engineering.

DOI： 10.1063/5.0030847

Scopus

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Observation of the Magneto-Thomson Effect 査読有り国際誌

Uchida K.I., Murata M., Miura A., Iguchi R.

Physical Review Letters 125 ( 10 ) 2020年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report the observation of the higher-order thermoelectric conversion based on a magneto-Thomson effect. By means of thermoelectric imaging techniques, we directly observed the temperature change induced by the Thomson effect in a polycrystalline Bi88Sb12 alloy under a magnetic field and found that the magnetically enhanced Thomson coefficient can be comparable to or even larger than the Seebeck coefficient. Our experiments reveal the significant contribution of the higher-order magnetothermoelectric conversion, opening the door to "nonlinear spin caloritronics."

DOI： 10.1103/PhysRevLett.125.106601

Scopus

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Simultaneous achievement of high thermal conductivity, high strength and formability in Mg-Zn-Ca-Zr sheet alloy 査読有り国際誌

Li Z.H., Sasaki T.T., Shiroyama T., Miura A., Uchida K., Hono K.

Materials Research Letters 8 ( 9 ) 335 - 340 2020年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

Lightweight magnesium alloys with good thermal conductance are in demand for structural components in portable devices. This work presents a strategy to achieve excellent thermal conductivity, room temperature (RT) formability and high strength in magnesium sheet alloys. We found that a Mg-1.6Zn-0.5Ca-0.4Zr alloy shows a substantial increase in thermal conductivity to over 130 W/(m·K) due to the reduced supersaturation of solute atoms in the matrix by the precipitation of Guinier-Preston (G.P.) zones while exhibiting excellent RT formability with a large Index Erichsen value of 8.1 mm, and a high yield strength of 227 MPa by peak aging treatment.

DOI： 10.1080/21663831.2020.1759718

Scopus

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High-temperature dependence of anomalous Ettingshausen effect in SmCo<inf>5</inf>-type permanent magnets 査読有り国際誌

Miura A., Masuda K., Hirai T., Iguchi R., Seki T., Miura Y., Tsuchiura H., Takanashi K., Uchida K.I.

Applied Physics Letters 117 ( 8 ) 2020年08月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The anomalous Ettingshausen effect (AEE) in SmCo5-type permanent magnets has been investigated in the high-temperature range from room temperature to around 600 K. The anomalous Ettingshausen coefficient of the SmCo5 and (SmGd)Co5 magnets monotonically increases with increasing the temperature and shows a similar temperature dependence, while the coefficient of SmCo5 is slightly larger than that of (SmGd)Co5 at high temperatures. The dimensionless figure of merit for the AEE in SmCo5 at high temperatures is much greater than the previous record obtained for the anomalous Nernst effect. The observed high-temperature behavior of the AEE is discussed based on the first-principles calculations of transverse transport coefficients.

DOI： 10.1063/5.0023111

Scopus

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Simultaneous direct measurements of conventional and inverse magnetocaloric effects in Ni-Mn-based Heusler alloys using lock-in thermography technique 査読有り国際誌

Modak R., Iguchi R., Sepehri-Amin H., Miura A., Uchida K.I.

AIP Advances 10 ( 6 ) 2020年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

The second-order conventional and first-order inverse magnetocaloric effects (MCEs) in Ni-Mn-based quaternary Heusler alloys have been systematically investigated by means of the lock-in thermography technique, which enables the direct measurement of the MCE-induced temperature change in a periodic magnetic field. Through systematic measurements of the temperature dependence of the MCE signals, the tuning of the conventional and inverse MCEs with temperature for the same Heusler alloys has been demonstrated, where the phase transitions responsible for the MCEs are clearly distinguished. The lock-in thermography measurements show that some Ni-Mn-based Heusler alloys exhibit much smaller temperature changes due to the inverse MCEs in the periodic field as compared to the conventional MCEs, even though they exhibit a larger magnetic entropy change across the first-order transition responsible for the inverse MCEs. We discuss the origin of this behavior in terms of the field-induced entropy change and thermal hysteresis of the alloys. These findings will be useful not only in accelerating the optimization of inverse MCE materials but also in understanding the mechanism of the MCEs.

DOI： 10.1063/5.0005865

Scopus

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Spin-mediated charge-to-heat current conversion phenomena in ferromagnetic binary alloys 査読有り国際誌

Miura A., Iguchi R., Seki T., Takanashi K., Uchida K.I.

Physical Review Materials 4 ( 3 ) 2020年03月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Spin-mediated charge-to-heat current conversion phenomena, i.e., the anomalous Ettingshausen effect (AEE) and the anisotropic magneto-Peltier effect (AMPE), have been investigated in various ferromagnetic Ni-Fe, Ni-Pt, Ni-Pd, and Fe-Pt binary alloys at room temperature. When a charge current is applied to a ferromagnetic conductor, the AMPE modulates the Peltier coefficient depending on the angle between the directions of the charge current and magnetization, while the AEE generates a heat current in the direction perpendicular to both the charge current and magnetization. We observed the strong material dependence of the thermoelectric conversion coefficients and figures of merit of these phenomena. Among the ferromagnetic alloys used in this study, Ni95Pt5 exhibits the largest AMPE of which the anisotropy of the Peltier coefficient is ∼12%. In contrast, the magnitude of the AEE signals is moderate in Ni95Pt5 but largest in Ni75Pt25 and Ni50Fe50. We discuss these behaviors by exploring the relations between these charge-to-heat current conversion phenomena and other transport as well as magnetic properties. This systematic study will provide a clue for clarifying the mechanisms of the AMPE and AEE and for enhancing the thermoelectric conversion efficiency of these phenomena.

DOI： 10.1103/PhysRevMaterials.4.034409

Scopus

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Mechanism of strong enhancement of anomalous Nernst effect in Fe by Ga substitution 査読有り国際誌

Nakayama H., Masuda K., Wang J., Miura A., Uchida K.I., Murata M., Sakuraba Y.

Physical Review Materials 3 ( 11 ) 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have investigated the anomalous Nernst effect (ANE) in Fe1-xGax alloy films with different Ga atomic compositions (x=0-0.44) deposited on MgO(001) single-crystalline substrates. We found that the magnitude of the ANE increases with increasing x up to x=0.32 even though the saturation magnetization decreases with increasing x, suggesting a dominant contribution of the intrinsic mechanism on the observed ANE. The magnitude of the ANE reaches 2.4μV/K in bcc Fe0.68Ga0.32 film, which is two orders of magnitude greater than that of pure Fe film. The magnetotransport measurements and the first-principles calculations revealed that the large ANE in bcc Fe1-xGax is caused by the large transverse Peltier coefficient. The drastic enhancement of the transverse Peltier coefficient with increasing x can be attributed to small Fermi level tuning through the electron doping effect. Thus, we anticipate that our finding will provide a crucial piece of information to enhance the thermopower through the ANE.

DOI： 10.1103/PhysRevMaterials.3.114412

Scopus

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Observation of anomalous Ettingshausen effect and large transverse thermoelectric conductivity in permanent magnets 査読有り国際誌

Miura A., Sepehri-Amin H., Masuda K., Tsuchiura H., Miura Y., Iguchi R., Sakuraba Y., Shiomi J., Hono K., Uchida K.I.

Applied Physics Letters 115 ( 22 ) 2019年11月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

This study focuses on the potential of permanent magnets as thermoelectric converters. It is found that a SmCo5-type magnet exhibits a large anomalous Ettingshausen effect (AEE) at room temperature and that its charge-to-heat current conversion coefficient is more than one order of magnitude greater than that of typical ferromagnetic metals. The large AEE is an exclusive feature of the SmCo5-type magnet among various permanent magnets in practical use, which is independent of the conventional performance of magnets based on static magnetic properties. The experimental results show that the large AEE originates from the intrinsic transverse thermoelectric conductivity of SmCo5. This finding makes a connection between permanent magnets and thermal energy engineering, providing the basis for creating "thermoelectric permanent magnets".

DOI： 10.1063/1.5131001

Scopus

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Scalable Multi-nanostructured Silicon for Roomerature Thermoelectrics 査読有り国際誌

Kashiwagi M., Liao Y., Ju S., Miura A., Konishi S., Shiga T., Kodama T., Shiomi J.

ACS Applied Energy Materials 2 ( 10 ) 7083 - 7091 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Thermoelectric conversion is capable of converting heat directly to electricity. However, actual implementations of thermoelectric devices are still limited with the leading bottleneck being the costs of materials and device integration, which calls for thermoelectric materials based on standard semiconductors with sufficient figure of merit (ZT) at room temperature. Bulk silicon crystal comes on the top of the list; however, the ZT even with nanostructuring has been limited due to its high thermal conductivity. Here, we have realized nanostructured silicon material with ZT larger than 0.3 at room temperature by a scalable process consisting of metal-assisted chemical etching and plasma-activated sintering. The material structure is highly complex being composed of randomly distributed nanograins, nanopores, and metal nanoprecipitates with hierarchical sizes, which significantly reduces thermal conductivity without appreciably sacrificing electrical conductivity. It is further identified by detailed experimental and theoretical investigations that the key contribution to the reduction comes from the softening of grain boundaries significantly limiting the interfacial phonon transmission. The developed high-performance silicon nanocomposite is expected to greatly enhance the application of thermoelectrics by lowering the material and process costs.

DOI： 10.1021/acsaem.9b00893

Scopus

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Anomalous Ettingshausen effect in ferrimagnetic Co-Gd 査読有り国際誌

Seki T., Miura A., Uchida K.I., Kubota T., Takanashi K.

Applied Physics Express 12 ( 2 ) 2019年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report the observation of anomalous Ettingshausen effect (AEE) in ferrimagnetic Co100-xGdx amorphous alloy thin films, which was visualized using lock-in thermography. We found that the sign of AEE is determined by the magnetic moments of Co sublattice, as well as those of the magneto-optical Kerr effect and the anomalous Hall effect, and the magnitude of AEE does not decrease even when x is close to the magnetization compensation composition. Our experimental results suggest that the magnetically-compensated ferrimagnets become candidates for high-performance thermomagnetic materials with tiny magnetization.

DOI： 10.7567/1882-0786/aafb5a

Scopus

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Probing length-scale separation of thermal and spin currents by nanostructuring YIG 査読有り国際誌

Miura A., Kikkawa T., Iguchi R., Uchida K.I., Saitoh E., Shiomi J.

Physical Review Materials 1 ( 1 ) 2017年06月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We have fabricated bulk nanostructured ferrimagnetic materials with different grain sizes by sintering ball-milled Y3Fe5O12 (YIG) nanoparticles and measured the grain-size dependence of the thermal conductivity and spin Seebeck thermopower. The nanostructuring reduces both thermal conductivity and thermopower, but the reduction of the latter was found to be considerably stronger despite the moderate difference in magnetization, which suggests that the length scales of transport of magnons and phonons contributing to the spin Seebeck effect are significantly larger than that of phonons carrying thermal current. This is consistent with the measurements of high-magnetic-field response of the spin Seebeck thermopower and low-temperature thermal conductivity, where the quenching of magnons seen in single-crystalline YIG was not observed in nanostructured YIG due to scattering of long-range low frequency magnons.

DOI： 10.1103/PhysRevMaterials.1.014601

Scopus

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Onsite synthesis of thermally percolated nanocomposite for thermal interface material 査読有り国際誌

Obori M., Nita S., Miura A., Shiomi J.

Journal of Applied Physics 119 ( 5 ) 2016年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

To solve the problem of lack of thermal percolation in thermal interface materials (TIM), we propose a two-step synthesis method to realize thermally percolated nanofiber network in polymer matrix. First, by packing vapor grown carbon fibers (VGCFs) on top of aluminum heat sink and integrally sintering the whole material, the aluminum partially melts and connects the VGCF network, forming a continuous thermal path, i.e., realizing thermal percolation. Second, the pores in the hybrid network are filled by Silicone oil to obtain a polymer nanocomposite. The direct synthesis of VGCF-aluminum network on the heat sink (onsite synthesis) omits pasting process of the TIM, and thus, removes the restriction on the network morphology. By this onsite synthesis method, we reinforce thermal contact not only between the nanofibers but also between nanofibers and the heat sink. By testing the developed TIM for thermal contact to silicon surface, we demonstrate the potential to significantly reduce thermal contact resistance from what can be achieved by a conventional TIM.

DOI： 10.1063/1.4941275

Scopus

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Crystalline-Amorphous Silicon Nanocomposites with Reduced Thermal Conductivity for Bulk Thermoelectrics 査読有り国際誌

Miura A., Zhou S., Nozaki T., Shiomi J.

ACS Applied Materials and Interfaces 7 ( 24 ) 13484 - 13489 2015年06月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Responding to the need for thermoelectric materials with high efficiency in both conversion and cost, we developed a nanostructured bulk silicon thermoelectric materials by sintering silicon crystal quantum dots of several nanometers in diameters synthesized by plasma-enhanced chemical vapor deposition (PECVD). The material consists of hybrid structures of nanograins of crystalline silicon and amorphous silicon oxide. The percolated nanocrystalline region gives rise to high power factor with the high doping concentration realized by PECVD, and the binding amorphous region reduces thermal conductivity. Consequently, the nondimensional figure of merit reaches 0.39 at 600°C, equivalent to the best reported value for silicon thermoelectrics. The thermal conductivity of the densely packed material is as low as 5 W m-1 K-1 in a wide temperature range from room temperature to 1000°C, which is beneficial not only for the conversion efficiency but also for material cost by requiring less material to establish certain temperature gradient. (Figure Presented).

DOI： 10.1021/acsami.5b02537

Scopus

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Quantitative Temperature Dependence of Longitudinal Spin Seebeck Effect at High Temperatures 査読有り国際誌

Ken-ichi Uchida, Takashi Kikkawa, Asuka Miura, Junichiro Shiomi, and Eiji Saitoh

Physical Review X 4 041023 2014年11月

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