73Poster Award NomineePoster Award NomineeP4-03In-situ Observation of Post-nucleation Process of NaCl Nanocrystals in an Aqueous Environment Using Liquid-cell Transmission Electron Microscopy Toshiki Shimizu1,2, Ryoga Numazaki1, Natsuki Nakasone2, and Hiroki Minoda1,2 1 Department of Applied Physics, Tokyo University of Agriculture and Technology 2 Department of Applied Physics and Chemical Engineering, Tokyo University of Agriculture and Technology Understanding the mechanism of crystal growth is one of the key factors in developing innovative materials with crystalline properties. Crystalline materials are essential to our daily lives and are closely involved in the production of foods such as salt and the development of new medicines or devices. The crystal growth is the post-nucleation process in which molecules or clusters are attaching to a host crystal. However, due to its stochasticity, complexity and diversity, the research in aqueous environment has been a great experimental challenge. In this work, by using liquid-cell transmission electron microscopy (LC-TEM), we observed the post-nucleation processes of a NaCl nanocrystal in a liquid cell made by amorphous carbon films that enabled stable observation under an electron beam. We succeeded in capturing the same NaCl nanocrystal grew through multiple post-nucleation processes which occurred simultaneously in different planes. The sub-nano level analysis confirmed that NaCl nanocrystal growth occurred via the stepwise attachment of sodium and chlorine ions or the orientated attachment of a cluster. We believe that our LC-TEM methodology will be one of the state-of-the-art materials characterization techniques for observing and analyzing samples in a liquid environment. This study got support from the Precise Measurement Technology Promotion Foundation (PMTP-F), JSPS KAKENHI (JP23K13628) and JKA (KEIRIN RACE). P4-04In Situ Scanning Transmission Electron Microscopy of the MoS2 Lithiation Process Kei Nakayama and Shunsuke Kobayashi Nanostructures Research Laboratory, Japan Fine Ceramics Center (JFCC) Lithiation reactions are crucial, particularly for Li-ion batteries. In many instances, the migration of Li ions into electrode materials is accompanied by atomic-scale and nanoscale structural changes. Therefore, in situ observation is necessary to comprehensively understand the dynamic processes involved in lithiation reactions, which has commonly been achieved through high-resolution transmission electron microscopy (HRTEM). However, the image contrast produced by HRTEM is not always directly interpretable, necessitating the investigation of alternative techniques. In this study, we used annular dark-field (ADF) scanning transmission electron microscopy (STEM), which is expected to provide more directly interpretable image contrast, to perform in situ observation of the MoS2 lithiation process. A tungsten probe equipped in a sample holder was used to bring air-exposed lithium (Li2CO3, etc.) into contact with single-crystalline MoS2 within an electron microscope. In situ ADF STEM at low magnification and following electron energy-loss spectroscopy confirmed the occurrence of a lithiation reaction. High-magnification in situ ADF STEM revealed contrast changes at subnanometer resolution. Although the visibility of the contrast in the raw data was very low due to a low signal-to-noise ratio, applying a threshold filter in Fourier space and a moving average filter improved clarity. As a result, a stepwise formation of a nanoscale domain structure was observed, likely serving to relieve internal stress during the lithiation process. This work was supported by JST PRESTO (JPMJPR23J9), JSPS KAKENHI (JP23K13567, JP23H00241), ISTF (0341198-A), NSGF (no grant number), and ATLA (JPJ004596) in Japan.
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