Updated on 2026/07/19

写真a

 
Ryohei Nagahiro
 
Organization
Graduate School of Engineering Department of Advanced Science and Technology Mechanical Systems Engineering Mechanical Material Engineering Laboratory Assistant Professor   
Degree
博士（工学） （ 2025.3   東京大学 ）
Homepage
https://mme-lab.github.io/en/
External link

Research Areas

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Thermal engineering

  • Nanotechnology/Materials / Nanostructure physics

Main research papers

Research History

  • Toyota Technological Institute   Graduate School of Engineering Department of Advanced Science and Technology Mechanical Systems Engineering Mechanical Material Engineering Laboratory   Assistant Professor

    2026.7

  • The University of Tokyo   The Graduate School of Engineering Institute of Engineering Innovation   Postdoctoral Researcher

    2025.8 - 2026.7

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    Country：Japan

  • The University of Tokyo   The Graduate School of Engineering Department of Mechanical Engineering   Research assistant

    2025.5 - 2025.7

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    Country：Japan

  • Research Fellow, JSPS   DC2

    2021.4 - 2023.3

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    Country：Japan

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Education

  • The University of Tokyo   The Graduate School of Engineering   Department of Mechanical Engineering

    2020.4 - 2025.3

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    Country： Japan

    Notes： Ph.D.

  • Gunma University   Graduate School of Science and Technology   Mechanical Science and Technology

    2018.4 - 2020.3

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    Country： Japan

    Notes： M.S.

  • Gunma University   School of Science and Technology   Mechanical Science and Technology

    2014.4 - 2018.3

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    Country： Japan

    Notes： B.S.

Professional Memberships

  • Thermoelectric Society of Japan

  • The Heat Transfer Society of Japan

  • The Japan Society of Applied Physics

Papers

  • Control of thermal conductivity in amorphous silicon oxide and silicon oxynitride thin films via ubiquitous transition metal doping Reviewed

    Michiko Sasaki, Kunihiko Shizume, Ryohei Nagahiro, Junichiro Shiomi, Masahiro Goto

    Japanese Journal of Applied Physics   65 ( 11 )   115502 - 115502   2026.6 （   ISSN:0021-4922   eISSN:1347-4065 ）

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    Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

    Abstract

    We report a strategy to tune and reduce thermal conductivity (TC) in dense amorphous silicon oxide (SiO x ) and silicon oxynitride (SiN x O y ) thin films through ubiquitous transition metal doping (iron [Fe], nickel [Ni], and chromium [Cr]) combined with process parameter control. Using a custom combinatorial sputter coating system, we fabricated multipoint libraries on single Si substrates and measured TC using frequency-domain thermoreflectance. Fe-, Ni-, and Cr-doped amorphous SiO x achieved an ultralow TC of 0.51 W m −1 K −1 , below typical glass-limit values reported for dense amorphous SiO 2 /SiN x . Anomalously high-TC samples (up to 2.2 W m −1 K −1 ) were linked to nanocrystalline phase formation. Principal component analysis revealed that in SiO x , TC is governed primarily by sputtering power, pressure, and target–substrate distance rather than dopant level, indicating structure-mediated suppression of long-mean free path propagon-like modes. In SiO x N y , TC spans 0.68–2.5 W m −1 K −1 ; and a distinct mechanism involving heavy element incorporation and a more open amorphous network. This approach enables continuous TC tailoring (0.51–2.5 W m −1 K −1 ) for robust high-temperature insulation coatings.

    DOI： 10.35848/1347-4065/ae6e81

    Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/ae6e81/pdf

  • The Frequency Domain Thermoreflectance Technique for Thermal Property Measurements Reviewed

    Alesanmi R. Odufisan, Benjamin Stern, Ryohei Nagahiro, Rosemary Wynnychenko, Sevan Chanakian, Junichiro Shiomi, Eleonora Isotta, Oluwaseyi Balogun

    Journal of Visualized Experiments   ( 226 )   2025.12 （     eISSN:1940-087X ）

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    Publishing type：Research paper (scientific journal)   Publisher：MyJove Corporation  

    DOI： 10.3791/68908

  • A thermal boundary resistance model via mean free path suppression functions and a Gibbs excess approach Reviewed

    Eleonora Isotta, Ryohei Nagahiro, Alesanmi R. Odufisan, Junichiro Shiomi, Oluwaseyi Balogun, G. Jeffrey Snyder

    International Journal of Heat and Mass Transfer   252   127417 - 127417   2025.12 （   ISSN:0017-9310 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.ijheatmasstransfer.2025.127417

  • Module-scale silicon 3D softened nanoarchitectures for eco-friendly thermoelectric energy harvesting Reviewed

    Ryohei Nagahiro, Bin Xu, Shingo Terashima, Yifei Li, Yuanzhe Li, Yuxuan Liao, Zhenglong Fang, Cheng Shao, Masato Ohnishi, Shinya Kato, Eiji Iwase, Junichiro Shiomi

    Materials Today Physics   57   101798 - 101798   2025.9 （   ISSN:2542-5293 ）

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.mtphys.2025.101798

  • Heat Transport at Silicon Grain Boundaries Reviewed

    Eleonora Isotta, Shizhou Jiang, Ruben Bueno‐Villoro, Ryohei Nagahiro, Kosuke Maeda, Dominique Alexander Mattlat, Alesanmi R. Odufisan, Alexandra Zevalkink, Junichiro Shiomi, Siyuan Zhang, Christina Scheu, G. Jeffrey Snyder, Oluwaseyi Balogun

    Advanced Functional Materials   34 ( 40 )   2024.7 （   ISSN:1616-301X   eISSN:1616-3028 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    Engineering microstructural defects, like grain boundaries, offers superior control over transport properties in energy materials. However, technological advancement requires establishing microstructure‐property relations at the micron or finer scales, where most of these defects operate. Here, the first experimental evidence of thermal resistance for individual silicon grain boundaries, estimated with a Gibbs excess approach, is provided. Coincident site lattice boundaries exhibit uniform excess thermal resistance along the same boundary, but notable variations from one boundary to another. Boundaries associated with low interface energy generally exhibit lower resistances, aligning with theoretical expectations and previous simulations, but several exceptions are observed. Transmission electron microscopy reveals that factors like interface roughness and presence of nanotwinning can significantly alter the observed resistance, which ranges from ∼0 to up to ∼2.3 m2K/GW. In stark contrast, significantly larger and less uniform values ‐ from 5 to 30 m2K/GW ‐ are found for high‐angle boundaries in spark‐plasma‐sintered polycrystalline silicon. Further, finite element analysis suggests that boundary planes that strongly deviate from the sample vertical (beyond ∼45°) can show up to 3‐times larger excess resistance. Direct correlations of properties with individual defects enable the design of materials with superior thermal performance for applications in energy harvesting and heat management.

    DOI： 10.1002/adfm.202405413

  • Extremely suppressed thermal conductivity of large-scale nanocrystalline silicon through inhomogeneous internal strain engineering Reviewed

    Bin Xu, Yuxuan Liao, Zhenglong Fang, Yifei Li, Rulei Guo, Ryohei Nagahiro, Yoshifumi Ikoma, Masamichi Kohno, Junichiro Shiomi

    Journal of Materials Chemistry A   11 ( 35 )   19017 - 19024   2023 （   ISSN:2050-7488   eISSN:2050-7496 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

    Record low thermal conductivity was achieved in large-scale crystal silicon due to the effect of inhomogeneous internal strain-induced phonon engineering via HPT processing.

    DOI： 10.1039/d3ta03011c

  • Nondestructive observation of pores during press forming of aluminum foam by X-ray radiography Reviewed

    Yoshihiko Hangai, Daisuke Kawato, Mizuki Ando, Masataka Ohashi, Yoshiaki Morisada, Takuya Ogura, Hidetoshi Fujii, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    Materials Characterization   170   110631 - 110631   2020.12 （   ISSN:1044-5803 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.matchar.2020.110631

  • Continuous Foaming of Multiple Aluminum Foam Precursors by Combining Conveyor and Optical Heating Reviewed

    Yoshihiko Hangai, Masataka Ohashi, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    MATERIALS TRANSACTIONS   61 ( 8 )   1703 - 1706   2020.8 （   ISSN:1345-9678   eISSN:1347-5320 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals  

    DOI： 10.2320/matertrans.mt-m2020137

  • Foaming of A1050 aluminum precursor by generated frictional heat during friction stir processing of steel plate Reviewed

    Yoshihiko Hangai, Keisuke Takada, Hidetoshi Fujii, Yasuhiro Aoki, Yuma Aihara, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    The International Journal of Advanced Manufacturing Technology   106 ( 7-8 )   3131 - 3137   2020.1 （   ISSN:0268-3768   eISSN:1433-3015 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1007/s00170-019-04834-4

    Other Link： http://link.springer.com/article/10.1007/s00170-019-04834-4/fulltext.html

  • Uniform Heating Model Analysis for the Formation Process of Aluminium Foam by Spot-Type Halogen Lamp Reviewed

    R. Nagahiro, N. Rosli, Y. Hangai, A. Yano, K. Amagai

    International Journal of Automotive and Mechanical Engineering   16 ( 4 )   7170 - 7180   2019.12 （   ISSN:2229-8649   eISSN:2180-1606 ）

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    Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Universiti Malaysia Pahang Al-Sultan Abdullah Press (UMPSA Press)  

    Heat treatment by heating furnace has limited the capability of heat treatment processes to control the desired heating volume and products’ sizes. This study introduced a heat treatment process using light heat sourced from a spot-type halogen lamp, with the aim of clarifying the thermal phenomenon of aluminium (Al) foam. Here, the temperature and deformation of Al foam were observed experimentally. In addition, thermal analysis was conducted numerically using a uniform heating model by neglecting the energy consumption of the blowing agent and deformation and thermal conductivity of Al. The experimental results revealed that the precursor initially formed at almost the same time as the phase change. The numerical results almost corresponded with the experimental results until the melting point of Al, after which a slight disagreement was observed. Moreover, the phase transformation appeared slightly earlier as a result of neglecting the deformation of Al foam and energy consumption of the blowing agent. Although the formation of Al foam cannot be expressed perfectly using the proposed uniform heating model, a qualitative phenomenon of such formation was successfully explained. In the future, the effects of deformation and energy consumption of the blowing agent and the thermal conductivity of Al can be considered in the proposed uniform heating model.

    DOI： 10.15282/ijame.16.4.2019.02.0536

  • Press Forming of Aluminum Foam during Foaming of Precursor Reviewed

    Yoshihiko Hangai, Masataka Ohashi, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    MATERIALS TRANSACTIONS   60 ( 11 )   2464 - 2469   2019.11 （   ISSN:1345-9678   eISSN:1347-5320 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals  

    DOI： 10.2320/matertrans.mt-m2019192

  • Fabrication of aluminum foam with complex shapes using pin screen mold and effect of arrangement of pins on its surface morphology Reviewed

    Yoshihiko Hangai, Keita Takahashi, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    Journal of Porous Materials   27 ( 2 )   347 - 353   2019.10 （   ISSN:1380-2224   eISSN:1573-4854 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1007/s10934-019-00810-1

    Other Link： http://link.springer.com/article/10.1007/s10934-019-00810-1/fulltext.html

  • Shaping of Aluminum Foam during Foaming of Precursor Using Steel Mesh with Various Opening Ratios Reviewed

    Yoshihiko Hangai, Ryohei Nagahiro, Masataka Ohashi, Kenji Amagai, Takao Utsunomiya, Nobuhiro Yoshikawa

    Metals   9 ( 2 )   223 - 223   2019.2 （     eISSN:2075-4701 ）

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    Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

    In this study, steel meshes with various opening ratios φ were used to shape aluminum foams during precursor foaming. The effect of φ on the heating rate and shape of the obtained aluminum foams was investigated. It was found that steel meshes with various opening ratios can be used to shape aluminum foam. There is no significant effect on the pore structures of the obtained aluminum foams when upward expansion is restricted during foaming, regardless of the value of φ. The meshes with higher φ clearly transfer the mesh pattern onto the surface of the aluminum foam but require a shorter foaming time. In contrast, the lower-φ meshes produce aluminum foams with a smoother surface but a longer foaming time is required.

    DOI： 10.3390/met9020223

  • Refoaming of deformed aluminum foam by precursor foaming process Reviewed

    Yoshihiko Hangai, Hayato Matsushita, Ryosuke Suzuki, Shinji Koyama, Kenji Amagai, Ryohei Nagahiro, Takao Utsunomiya, Masaaki Matsubara, Nobuhiro Yoshikawa

    Journal of Porous Materials   26 ( 4 )   1149 - 1155   2019.1 （   ISSN:1380-2224   eISSN:1573-4854 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1007/s10934-018-0716-y

    Other Link： http://link.springer.com/article/10.1007/s10934-018-0716-y/fulltext.html

  • Shaping of Aluminum Foam Using Point Group Mold Reviewed

    Yoshihiko Hangai, Keita Takahashi, Ryohei Nagahiro, Kenji Amagai, Takao Utsunomiya

    MATERIALS TRANSACTIONS   59 ( 12 )   1952 - 1955   2018.12 （   ISSN:1345-9678   eISSN:1347-5320 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals  

    DOI： 10.2320/matertrans.m2018281

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Presentations

  • A Thermal Boundary Resistance model via mean free path suppression functions and a Gibbs excess approach International conference

    Eleonora Isotta, Rryohei Nagahiro, Alesanmi Richmond, Rerelope Odufisan, Junichiro Shiomi, Oluwaseyi Balogun, G. Jeffrey Snyder

    2025 MRS Spring Meeting & Exhibit  ( Seattle Convention Center, Washington )   2025.4 

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    Language：English   Presentation type：Poster presentation  

    SF01.09.02

  • Validation of Gibbs Excess methods with bonded Si wafer Invited International conference

    Rryohei Nagahiro, Eleonora Isotta, G. Jeffrey Snyder, Oluwaseyi Balogun, Junichiro Shiomi

    The 1st A3 Nano & Thermal Energy Engineering Workshop  ( Sanjo Conference Hall (The University of Tokyo), Tokyo )   2025.1 

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    Language：English   Presentation type：Poster presentation  

    P1-16

  • Direct observation of thermal boundary resistance in silicon system International conference

    Ryohei Nagahiro, Kazuhiro Maeda, Eleonora Isotta, Shuo Jiang, G. Jeffrey Snyder, Oluwatobi Balogun, Junichiro Shiomi

    The Third Asian Conference on Thermal Sciences  ( Shanghai Fuyue Hotel, Shanghai )   2024.6 

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    Language：English   Presentation type：Oral presentation (general)  

    O-0634

  • Strain Engineering in 3D Architected Silicon for High-Performance Thermoelectric Energy Harvesting International conference

    Bin Xu, Ryohei Nagahiro, Shingo Terashima, Cheng Shao, Yifei Li, Zhenglong Fang, Yuanzhe Li, Yuxuan Liao, Masato Ohnishi, Shinya Kato, Eiji Iwase, Junichiro Shiomi

    The Third Asian Conference on Thermal Sciences  ( Shanghai Fuyue Hotel, Shanghai )   2024.6 

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    Language：English   Presentation type：Oral presentation (general)  

    O-0034

  • Machine-Learning Minimization of Amorphous Heat Conduction by High-Throughput Deposition Process in The Loop International conference

    Kunihiko Shizume, Ryohei Nagahiro, Michoko Sasaki, Masahiro Goto, Junichiro Shiomi

    2024 MRS Spring Meeting & Exhibit  ( Seattle Convention Center, Washington )   2024.4 

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    Language：English   Presentation type：Oral presentation (general)  

    MT03.02.08

  • Thermoelectric performance of bulk silicon with 3D nano-architecture International conference

    Ryohei Nagahiro, Bin Xu, Shingo Terashima, Cheng Shao, Yifei Li, Zhenglong Fang, Yuanzhe Li, Yuxuan Liao, Masato Ohnishi, Shinya Kato, Eiji Iwase, Junichiro Shiomi

    The 39th Annual International Conference on Thermoelectrics  ( The University of Washington, Seattle )   2023.6 

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    Language：English   Presentation type：Oral presentation (general)  

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