-
Stability of electrochemical hydrogen charging in NaCl aqueous solution containing NH4SCN: Effect of changes in solution chemistry
Peer-reviewed
Saya Ajito, Yusuke Kabasawa, Hiroshi Kakinuma, Motomichi Koyama, Eiji Akiyama
Corrosion Science 2025/06
DOI：
10.1016/j.corsci.2025.112843
-
Grain boundary nanochemistry and intergranular corrosion of Fe-0.01wt.%P alloy: Roles of elemental segregations and misorientation
Peer-reviewed
Saya Ajito, Kazuya Tojima, Hiroshi Kakinuma, Kohei Ikeda, Yongjie Zhang, Tomohiko Hojo, Goro Miyamoto, Motomichi Koyama, Tadashi Furuhara, Eiji Akiyama
Acta Materialia 120577-120577 2025/01
Publisher:
Elsevier BV
DOI：
10.1016/j.actamat.2024.120577
ISSN：
1359-6454
-
Visualization of Microscopic Hydrogen Diffusion in Polycrystalline Pure Ni Using an Ir Complex
Peer-reviewed
Saya Ajito, Hiroshi Kakinuma, Motomichi Koyama, Eiji Akiyama
MATERIALS TRANSACTIONS 2024
Publisher:
Japan Institute of Metals
DOI：
10.2320/matertrans.mt-c2024008
ISSN：
1345-9678
eISSN：
1347-5320
-
Environment-assisted cracking of AZ31 magnesium alloy in a borate buffer solution containing ammonium thiocyanate under various potentials
Peer-reviewed
Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Sachiko Hiromoto, Eiji Akiyama
Corrosion Science 218 2023/07/01
DOI：
10.1016/j.corsci.2023.111195
ISSN：
0010-938X
-
Effect of Stretch-forming on Hydrogen Diffusion Behavior in High-strength Steel Sheet
Peer-reviewed
Hayato Nishimura, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Ken-ichi Fujita, Yuki Shibayama, Hiroshi Kakinuma, Eiji Akiyama
ISIJ International 2023
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2023-149
ISSN：
0915-1559
eISSN：
1347-5460
-
Application of an iridium complex for detecting hydrogen permeation through pure iron
Peer-reviewed
Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Ken-ichi Fujita, Eiji Akiyama
International Journal of Hydrogen Energy 45 (46) 25580-25586 2020/09
Publisher:
Elsevier BV
DOI：
10.1016/j.ijhydene.2020.06.113
ISSN：
0360-3199
-
Factors controlling transformation-induced hydrogen desorption and hydrogen-reduced transformability in austenitic steels clarified via dynamic hydrogen detection during cryogenic deformation
Motomichi Koyama, Yifei Wen, Tomohiko Hojo, Saya Ajito, Makoto Kawamori, Eiji Akiyama
Scripta Materialia 2025/08
DOI：
10.1016/j.scriptamat.2025.116749
-
Semi-quantitative characterisation of coherency-dependent hydrogen diffusion at Σ3 grain boundaries in pure Ni
Peer-reviewed
Hiroshi Kakinuma, Motomichi Koyama, Rama Srinivas Varanasi, Saya Ajito, Eiji Akiyama
Materials Research Letters 1-8 2025/01/24
Publisher:
Informa UK Limited
DOI：
10.1080/21663831.2025.2457369
eISSN：
2166-3831
-
Hydrogen Effects on Hall–Petch Coefficient and Fracture Strength in Pure Ni and Ni-20Cr Alloy: A Macroscopic Insight of the Hydrogen Embrittlement Mechanism
Peer-reviewed
Motomichi Koyama, Kota Tomatsu, Hiroshi Kakinuma, Saya Ajito, Eiji Akiyama
Metallurgical and Materials Transactions A 2025/01/23
Publisher:
Springer Science and Business Media LLC
DOI：
10.1007/s11661-025-07688-6
ISSN：
1073-5623
eISSN：
1543-1940
-
Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation-Induced Plasticity-Aided Bainitic Ferrite Steels
Peer-reviewed
Tomohiko Hojo, Motomichi Koyama, Bakuya Kumai, Yutao Zhou, Yuki Shibayama, Ayumi Shiro, Takahisa Shobu, Hiroyuki Saitoh, Saya Ajito, Eiji Akiyama
ISIJ International 65 (2) 284-296 2025
DOI：
10.2355/isijinternational.ISIJINT-2024-268
ISSN：
0915-1559
-
Real-Time 2D Mapping of Hydrogen Entry and pH Distribution inside a NaCl Droplet on an Fe Sheet Using a Hydrogenochromic Sensor
Hiroshi Kakinuma, Sachiko Hiromoto, Tomohiko Hojo, Saya Ajito, Motomichi Koyama, Eiji Akiyama
ECS Meeting Abstracts 2024/11/22
DOI：
10.1149/MA2024-02171711mtgabs
-
Visualization of Microscopic Hydrogen Diffusion in Polycrystalline Pure Ni Using an Ir Complex
Peer-reviewed
Saya Ajito, Hiroshi Kakinuma, Motomichi Koyama, Eiji Akiyama
Zairyo-to-Kankyo 73 (8) 194-199 2024/08/10
Publisher:
Japan Society of Corrosion Engineering
DOI：
10.3323/jcorr.73.194
ISSN：
0917-0480
eISSN：
1881-9664
-
ポリアニリンを用いた金属中を拡散する水素の可視化技術
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Motomichi Koyama, Eiji Akiyama
Materia Japan 63 (6) 381-389 2024/06/01
Publisher:
Japan Institute of Metals
DOI：
10.2320/materia.63.381
ISSN：
1340-2625
eISSN：
1884-5843
-
Mechanism of local hydrogen entry into Fe sheets induced by atmospheric corrosion: Significance of potential, pH, and rust layer thickness
Peer-reviewed
Hiroshi Kakinuma, Sachiko Hiromoto, Tomohiko Hojo, Saya Ajito, Motomichi Koyama, Eiji Akiyama
Corrosion Science 232 112043-112043 2024/05
Publisher:
Elsevier BV
DOI：
10.1016/j.corsci.2024.112043
ISSN：
0010-938X
-
Microscopic visualization of hydrogen diffusion in UNS S32750 super duplex stainless steel: Roles of crystal structure and grain size
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Motomichi Koyama, Eiji Akiyama
International Journal of Hydrogen Energy 59 866-873 2024/03
Publisher:
Elsevier BV
DOI：
10.1016/j.ijhydene.2024.02.069
ISSN：
0360-3199
-
Hydrogen Embrittlement Property of a 1.5 GPa Dual-Phase Steel Evaluated Using U-bending Test: A Comparison with Tempered Martensitic Steel with Identical Tensile Strength
Peer-reviewed
Shuya Chiba, Motomichi Koyama, Tomohiko Hojo, Saya Ajito, Yuki Shibayama, Rama Srinivas Varanasi, Eiji Akiyama
ISIJ International 64 (4) 706-713 2024/02/28
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2023-287
ISSN：
0915-1559
eISSN：
1347-5460
-
Plasticity-induced Hydrogen Desorptions Associated with Hydrogen-assisted Martensitic Transformation and Deformation Twinning in Austenitic Stainless Steels
Peer-reviewed
Yifei Wen, Motomichi Koyama, Tomohiko Hojo, Saya Ajito, Eiji Akiyama
ISIJ International 64 (2) 474-481 2024/01/30
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2023-130
ISSN：
0915-1559
eISSN：
1347-5460
-
Transformation Behaviors and Microstructure Modifications in Hydrogen-Charged Ti-Ni Shape Memory Alloy
Saya Ajito
Shape Memory and Superelasticity 2024
DOI：
10.1007/S40830-024-00495-9
-
Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries
Peer-reviewed
Yutao Zhou, Zhipeng Yang, Motomichi Koyama, Saya Ajito, Tomohiko Hojo, Hiroshi Fudouzi, Eiji Akiyama
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 110 (3) 311-320 2024
DOI：
10.2355/tetsutohagane.TETSU-2023-020
ISSN：
0021-1575
-
Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation- Induced Plasticity-Aided Bainitic Ferrite Steels
Peer-reviewed
Tomohiko Hojo, Motomichi Koyama, Bakuya Kumai, Yutao Zhou, Yuki Shibayama, Ayumi Shiro, Takahisa Shobu, Hiroyuki Saitoh, Saya Ajito, Eiji Akiyama
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 110 (3) 227-240 2024
DOI：
10.2355/tetsutohagane.TETSU-2023-062
ISSN：
0021-1575
-
In situ visualization of misorientation-dependent hydrogen diffusion at grain boundaries of pure polycrystalline Ni using a hydrogen video imaging system
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Eiji Akiyama
Acta Materialia 119536-119536 2023/11
Publisher:
Elsevier BV
DOI：
10.1016/j.actamat.2023.119536
ISSN：
1359-6454
-
Temperature dependence of hydrogen-assisted damage evolution and fracture behavior in TRIP-aided bainitic ferrite steel
Peer-reviewed
Yutao Zhou, Tomohiko Hojo, Motomichi Koyama, Saya Ajito, Eiji Akiyama
Materials Science and Engineering: A 886 2023/10/17
DOI：
10.1016/j.msea.2023.145663
ISSN：
0921-5093
-
Hydrogen-Induced Delayed Fracture in a 1.5 GPa Dual-Phase Steel via Coalescence of Surface and Sub-surface Cracks
Peer-reviewed
Rama Srinivas Varanasi, Motomichi Koyama, Yuki Shibayama, Shuya Chiba, Saya Ajito, Tomohiko Hojo, Eiji Akiyama
Metallurgical and Materials Transactions A 2023/05/31
Publisher:
Springer Science and Business Media LLC
DOI：
10.1007/s11661-023-07096-8
ISSN：
1073-5623
eISSN：
1543-1940
-
Influence of post-oxidizing treatment on passivation performance on the spin-coated titanium oxide films on crystalline silicon
Peer-reviewed
Hao Luo, Van Hoang Nguyen, Kazuhiro Gotoh, Saya Ajito, Tomohiko Hojo, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami
Thin Solid Films 764 139597-139597 2023/01
Publisher:
Elsevier BV
DOI：
10.1016/j.tsf.2022.139597
ISSN：
0040-6090
-
Transformation-Induced Microcracks and Their Arrest with Different Deformation Temperatures in a Medium Mn Steel
Peer-reviewed
Yutao Zhou, Motomichi Koyama, Tomohiko Hojo, Saya Ajito, Eiji Akiyama
Metallurgical and Materials Transactions A 54 (1) 153-166 2023/01
Publisher:
Springer Science and Business Media LLC
DOI：
10.1007/s11661-022-06855-3
ISSN：
1073-5623
eISSN：
1543-1940
-
In situ 2D mapping of hydrogen entry into an Fe sheet under a droplet of NaCl solution using a hydrogenochromic sensor
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Sachiko Hiromoto, Eiji Akiyama
International Journal of Hydrogen Energy 2022/09
Publisher:
Elsevier BV
DOI：
10.1016/j.ijhydene.2022.09.006
ISSN：
0360-3199
-
Simultaneous observations of the corrosion behavior of an Fe sheet and the associated hydrogen distribution therein employing a hydrogenochromic sensor
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Sachiko Hiromoto, Eiji Akiyama
Corrosion Science 206 110534-110534 2022/09
Publisher:
Elsevier BV
DOI：
10.1016/j.corsci.2022.110534
ISSN：
0010-938X
-
Synergistic effects of hydrogen and deformation temperature on mechanical properties of TRIP-aided bainitic ferrite steel
Peer-reviewed
Yutao Zhou, Tomohiko Hojo, Motomichi Koyama, Saya Ajito, Eiji Akiyama
Materials Science and Engineering: A 842 143070-143070 2022/05
Publisher:
Elsevier BV
DOI：
10.1016/j.msea.2022.143070
ISSN：
0921-5093
-
Effect of Stretch-forming on Hydrogen Diffusion Behavior in High-strength Steel Sheet
Peer-reviewed
Hayato Nishimura, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Ken-ichi Fujita, Yuki Shibayama, Hiroshi Kakinuma, Eiji Akiyama
Tetsu-to-Hagane 108 (5) 316-324 2022/05
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/tetsutohagane.tetsu-2021-096
ISSN：
0021-1575 1883-2954
eISSN：
1883-2954
-
Corrosion Monitoring of Carbon Steel in Non-Irradiated, Humidity-Controlled Environments Simulating Gamma-Ray Irradiation
Peer-reviewed
Atsushi Omori, Saya Ajito, Hiroshi Abe, Kuniki Hata, Tomonori Sato, Yoshiyuki Kaji, Hiroyuki Inoue, Mitsumasa Taguchi, Hajime Seito, Eiji Tada, Shunichi Suzuki, Eiji Akiyama
MATERIALS TRANSACTIONS 63 (4) 555-561 2022/04/01
Publisher:
Japan Institute of Metals
DOI：
10.2320/matertrans.mt-c2021006
ISSN：
1345-9678 1347-5320
eISSN：
1347-5320
-
Comparative study of stress and strain partitioning behaviors in medium manganese and transformation-induced plasticity-aided bainitic ferrite steels
Peer-reviewed
Tomohiko Hojo, Motomichi Koyama, Bakuya Kumai, Yuki Shibayama, Ayumi Shiro, Takahisa Shobu, Hiroyuki Saitoh, Saya Ajito, Eiji Akiyama
Scripta Materialia 210 114463-114463 2022/03
Publisher:
Elsevier {BV}
DOI：
10.1016/j.scriptamat.2021.114463
ISSN：
1359-6462
-
Effects of Thermomechanical Processing on Hydrogen Embrittlement Properties of UltraHigh-Strength TRIP-Aided Bainitic Ferrite Steels
Peer-reviewed
Tomohiko Hojo, Yutao Zhou, Junya Kobayashi, Koh-ichi Sugimoto, Yoshito Takemoto, Akihiko Nagasaka, Motomichi Koyama, Saya Ajito, Eiji Akiyama
Metals 12 (2) 269-269 2022/01/31
Publisher:
{MDPI} {AG}
DOI：
10.3390/met12020269
eISSN：
2075-4701
-
Real‐Time Visualization of Hydrogen Distribution in Metals Using Polyaniline: An Ultrasensitive Hydrogenochromic Sensor
Peer-reviewed
Hiroshi Kakinuma, Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Eiji Akiyama
Advanced Materials Interfaces 9 (18) 2101984-2101984 2022/01/29
Publisher:
Wiley
DOI：
10.1002/admi.202101984
ISSN：
2196-7350
eISSN：
2196-7350
-
Effects of Ammonium Thiocyanate and pH of Aqueous Solutions on Hydrogen Absorption into Iron under Cathodic Polarization
Peer-reviewed
Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Eiji Akiyama
Tetsu-to-Hagane 108 (11) 857-863 2022
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/tetsutohagane.tetsu-2022-043
ISSN：
0021-1575
eISSN：
1883-2954
-
Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries
Peer-reviewed
Yutao Zhou, Zhipeng Yang, Motomichi Koyama, Saya Ajito, Tomohiko Hojo, Hiroshi Fudouzi, Eiji Akiyama
ISIJ International 2022
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2022-054
ISSN：
0915-1559
eISSN：
1347-5460
-
Corrosion Monitoring of Carbon Steel in Non-Irradiated, Humidity-Controlled Environments Simulating Gamma-Ray Irradiation
Peer-reviewed
Atsushi Omori, Saya Ajito, Hiroshi Abe, Kuniki Hata, Tomonori Sato, Yoshiyuki Kaji, Hiroyuki Inoue, Mitsumasa Taguchi, Hajime Seito, Eiji Tada, Shunichi Suzuki, Eiji Akiyama
Zairyo-to-Kankyo 70 (11) 358-364 2021/11/10
Publisher:
Japan Society of Corrosion Engineering
DOI：
10.3323/jcorr.70.358
ISSN：
0917-0480 1881-9664
eISSN：
1881-9664
-
Strain rate sensitivity of hydrogen-assisted ε-martensitic transformation and associated hydrogen embrittlement in high-Mn steel
Peer-reviewed
Chunxi Hao, Motomichi Koyama, Saya Ajito, Eiji Akiyama
International Journal of Hydrogen Energy 46 (53) 27221-27233 2021/08
Publisher:
Elsevier BV
DOI：
10.1016/j.ijhydene.2021.05.162
ISSN：
0360-3199
-
Effects of Residual Stress on Hydrogen Embrittlement of a Stretch-Formed Tempered Martensitic Steel Sheet
Peer-reviewed
Hayato Nishimura, Tomohiko Hojo, Saya Ajito, Yuki Shibayama, Motomichi Koyama, Hiroyuki Saitoh, Ayumi Shiro, Ryo Yasuda, Takahisa Shobu, Eiji Akiyama
Tetsu-to-Hagane 107 (9) 760-768 2021
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/tetsutohagane.tetsu-2021-055
ISSN：
0021-1575
eISSN：
1883-2954
-
Effects of Ammonium Thiocyanate and pH of Aqueous Solutions on Hydrogen Absorption into Iron under Cathodic Polarization
Peer-reviewed
Saya Ajito, Tomohiko Hojo, Motomichi Koyama, Eiji Akiyama
ISIJ International 61 (4) 1209-1214 2021
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2020-551
ISSN：
0915-1559
eISSN：
1347-5460
-
Simultaneous Measurements of Polarization Resistance and Hydrogen Permeation Current of Iron in an Aqueous NaCl Droplet
Peer-reviewed
Saya Ajito, Eiji Tada, Azusa Ooi, Atsushi Nishikata
ISIJ International 2021
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2020-583
ISSN：
0915-1559
-
Effects of Residual Stress on Hydrogen Embrittlement of a Stretch-Formed Tempered Martensitic Steel Sheet
Peer-reviewed
Hayato Nishimura, Tomohiko Hojo, Saya Ajito, Yuki Shibayama, Motomichi Koyama, Hiroyuki Saitoh, Ayumi Shiro, Ryo Yasuda, Takahisa Shobu, Eiji Akiyama
ISIJ International 61 (4) 1170-1178 2020
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2020-492
ISSN：
0915-1559
eISSN：
1347-5460
-
Effect of Iron Rust on Hydrogen Uptake during Steel Corrosion under an Aqueous NaCl Droplet
Peer-reviewed
Saya Ajito, Eiji Tada, Azusa Ooi, Atsushi Nishikata
ISIJ International 2020
Publisher:
Iron and Steel Institute of Japan
DOI：
10.2355/isijinternational.isijint-2020-528
ISSN：
0915-1559
-
Measurement of pH in a Thin Electrolyte Droplet Using the Kelvin Probe Technique
Peer-reviewed
Saya Ajito
MATERIALS TRANSACTIONS 2019/04/01
DOI：
10.2320/matertrans.m2018385
-
Electrochemical Study on Hydrogen Absorption of Steel in Atmospheric Corrosion
Saya Ajito
Tokyo Institute of Technology 2019/03
-
Simultaneous Measurements of Corrosion Potential and Hydrogen Permeation Current in Atmospheric Corrosion of Steel
Peer-reviewed
Saya Ajito
ISIJ International 2019
DOI：
10.2355/isijinternational.isijint-2019-113
-
Hydrogen Absorption Behavior of Pre-Rusted Steels under an NaCl Droplet
Peer-reviewed
Saya Ajito, Eiji Tada, Azusa Ooi, Atsushi Nishikata
Journal of The Electrochemical Society 166 (10) C243-C249 2019
Publisher:
The Electrochemical Society
DOI：
10.1149/2.0591910jes
https://orcid.org/0000-0003-3444-9845