Language：English   Publisher：Microscopy  

In-situ observation has expanded the application of transmission electron microscopy (TEM) and has made a significant contribution to materials research and development for energy, biomedical, quantum, etc. Recent technological developments related to in-situ TEM have empowered the incorporation of three-dimensional observation, which was previously considered incompatible. In this review article, we take up heating as the most commonly used external stimulus for in-situ TEM observation and overview recent in-situ TEM studies. Then, we focus on the electron tomography (ET) and in-situ heating combined observation by introducing the authors’ recent research as an example. Assuming that in-situ heating observation is expanded from two dimensions to three dimensions using a conventional TEM apparatus and a commercially available in-situ heating specimen holder, the following in-situ heating-and-ET observation procedure is proposed: (i) use a rapid heating-and-cooling function of a micro-electro-mechanical system holder; (ii) heat and cool the specimen intermittently and (iii) acquire a tilt-series dataset when the specimen heating is stopped. This procedure is not too technically challenging and can have a wide range of applications. Essential technical points for a successful 4D (space and time) observation will be discussed through reviewing the authors’ example application.

DOI： 10.1093/jmicro/dfae008

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Language：Japanese   Publisher：The Japanese Association for Crystal Growth  

<p>  Metal nanoparticles undertake sintering at a lower temperature compared to their bulk counterparts, attracting great attention in industrial applications such as printed electronics. Since nanoparticles are easy to aggregate, the three-dimensional (3D) visualization of their sintering process plays a vital role in quantifying the morphological changes during heating. However, the nanoparticles are sensitive to surface contamination, resulting in poor affinity to the 3D visualization with conventional electron beam intensity because the visualization technique requires a long beam exposure time, potentially making beam induced contamination significant. In this paper, we demonstrate our developed 3D observation scheme, including advanced image processing techniques. A sample transfer system, which enables to prevent nanoparticles from being exposed to air, and an ultra-low-electron dose observation protocol prevents surface contamination during the observation. The low-signal-to-noise ratio of acquired images is compensated by the advanced image processing techniques. The obtained 3D images of nanoparticles enable to measure the neck growth and variation of particle distance in 3D during the sintering in a quantitative way.</p>

DOI： 10.19009/jjacg.51-1-03

CiNii Research

Language：Japanese   Publisher：The Society of Materials Science, Japan  

DOI： 10.2472/jsms.72.631

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CiNii Research

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

The current study reveals the Hall-Petch relationship, or mean grain size control, and flow properties of equiatomic FeCoNi alloy having different grain sizes at room temperature (298 K) and cryogenic temperature (77 K). For the first time, various mean grain sizes ranging from the ultra-fine regime (0.7 μm) to the coarse grain regime (145.3 μm) were achieved in a FeCoNi alloy by high-pressure torsion and subsequent annealing. The tensile yield strength depends strongly on temperature and grain size. Hall-Petch plots demonstrate that the grain boundary strength coefficient is insensitive to the temperature, whereas friction stress increases as the temperature decreases. For all the grain sizes both strength and ductility were increased with decreasing the temperature down to 77 K. Dislocation slip is responsible for the room temperature mechanical properties. At cryogenic temperature, on the other hand, nano twinning appears as an additional deformation mechanism in addition to the dislocation slip.

DOI： 10.1016/j.scriptamat.2023.115392

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Materials Science and Engineering: A  

While leading a great strain hardening capability, carbon-containing twinning-induced plasticity (TWIP) steels exhibit serrations on their stress-strain curves, resulting in barriers to commercial development. Although grain refinement is believed to suppress the serrations, how the grain size, particularly in the ultrafine-grained (UFG) range, and its orientation impacting on the serrations and plastic deformation mechanism are overlooked. Here, we compared the plastic deformation behavior in fine-grained (2 μm) and ultrafine-grained (0.86 μm) specimens, in both macroscopic and microscopic behavior, using digital image correlation (DIC) and scanning transmission and transmission electron microscopy (S/TEM) techniques. Our results showed that the dominant plastic deformation mode was changed from dislocation gliding and tangling to stacking faults and deformation twinning in the grains equal to or smaller than 1 μm (ultrafine grains). This alteration is also strongly influenced by the grain orientation, i.e., the maximum resolved shear stress for slip versus twinning. The enhancement of strain localization and the inhibition of the serrations in the UFG specimens are discussed.

DOI： 10.1016/j.msea.2022.144506

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Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.61.84

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Scanning transmission electron microscopy (STEM) is suitable for visualizing the inside of a relatively
thick specimen than the conventional transmission electron microscopy, whose resolution is
limited by the chromatic aberration of image forming lenses, and thus, the STEM mode has been
employed frequently for computed electron tomography based three-dimensional (3D) structural
characterization and combined with analytical methods such as annular dark field imaging or
spectroscopies. However, the image quality of STEM is severely suffered by noise or artifacts especially
when rapid imaging, in the order of millisecond per frame or faster, is pursued. Here we demonstrate
a deep-learning-assisted rapid STEM tomography, which visualizes 3D dislocation arrangement only
within five-second acquisition of all the tilt-series images even in a 300 nm thick steel specimen. The
developed method offers a new platform for various in situ or operando 3D microanalyses in which
dealing with relatively thick specimens or covering media like liquid cells are required.

Event date： 2024.11

Language：Japanese   Presentation type：Poster presentation  

Event date： 2024.7 - 2024.8

Language：English   Presentation type：Poster presentation  

Venue：Cleveland, Ohio   Country：United States  

Event date： 2024.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：出島メッセ長崎  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：BEXCO, Busan   Country：Korea, Republic of  

Event date： 2023.9

Language：English  

Venue：Bexco, Busan   Country：Korea, Republic of  

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Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Chikushi hall, Chikushi Campus, Kyushu University   Country：Japan  

Event date： 2023.6

Language：Japanese  

Venue：くにびきメッセ   Country：Japan  

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Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学幸町キャンパス   Country：Japan  

Event date： 2023.5

Language：Japanese  

Venue：香川大学幸町キャンパス   Country：Japan  

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Event date： 2023.3

Language：Japanese  

Venue：日本溶接協会四国地区溶接技術検定委員会   Country：Japan  

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Event date： 2022.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都テルサ   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：日本製鉄 ㈱ 富津ＲＥセンター 本館ホール   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：石川県政記念「しいのき迎賓館」   Country：Japan  

Event date： 2022.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ビッグパレットふくしま   Country：Japan  

Event date： 2022.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ビッグパレットふくしま   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：崇城大学(オンライン)   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学(オンライン)   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学(オンライン)   Country：Japan