Environmental TEM in der modernen Mikro- und Nanostrukturforschung
Zusammenfassung der Projektergebnisse
The development of novel materials as well as the analysis of failure of applied materials strongly rely on advanced transmission electron microscopy (TEM) on the nm- and atomic scale. For functional materials, e.g., in catalysis and energy conversion as well as many structural alloys and ceramics, environmental TEM (ETEM) provides exceptional capabilities not merely to study the microstructure and composition down to the atomic scale but to study the evolution of such a material under gaseous environment conditions meaning during operation or formation within the microscope. In this project, fundamental methodical aspects of in situ and environmental TEM were addressed and ETEM was applied to understand and develop novel materials for energy conversion and catalysis. In particular, the better understanding of Li-ion battery degradation was already utilized to build novel prototype batteries with with superior performance and long-term stability compared to commercial ones. Those results were widely highlighted in the press (see Altmetric, Elektronikpraxis). It turned out early during the project that the operation of an ETEM microscope in conjunction with a complex state-of-the-art in situ holder for, e.g., heating/cooling, biasing or electrical/mechanical testing may be quite challenging, because both, the gas environment as well as the sample holder, have to be monitored and controlled while comprehensive TEM data is being acquired. Consequently, close collaboration of scientists at the microscope was found to be beneficial to conduct such experiments. Moreover, accurate methods are still needed to validate and monitor the process parameters during ETEM like temperature, gas composition and pressure close to or at the investigated region of the TEM sample. As listed before, a joint preparatory study on precise temperature measurements in TEM with an accuracy of better than 5K (for metals) by electron diffraction is already published. Currently, the local temperature measurement by CBED with similar accuracy is being developed. A related task was to achieve sample temperatures far above 700 °C at gas pressures as low as only a few mbar. Independent of the sample geometry (bulk, FIB lamella, dispersed NPs) such temperatures could not be reached reliably using a common FEI ETEM Titan in conjunction with a MEMS-based heating holder — Renu Sharma’s group from NIST already published on that issue and the significant discrepancies between pre-set and true sample temperature of a few 100 K in ETEM using such a microscope. That research is still ongoing and requires the development of novel experimental capabilities. Despite such challenges, the project provided a deep insight in the design and conduct of ETEM experiments. Working on most different types of materials allowed for recognizing essential methodical limitations and requirements on optimal TEM samples and sample handling. The obtained knowledge will allow for the better evaluation of the feasibility of future ETEM measurements and thus for a successful design of in situ / in operando environmental studies for materials research. Most importantly, the fellowship strengthened my scientific independency and allowed me to connect to renowned researchers, both, from the EM community as well as in the field of materials science and to initiate fruitful collaborations with numerous groups. After my return to Germany I started to set up a new research group on advanced EM and materials science at the University of Siegen.
Projektbezogene Publikationen (Auswahl)
- Highly intact and pure oxo-functionalized graphene — Synthesis and electron-beam induced reduction, Angew. Chem. Int. Ed. 55 (2016), 15771–15774
B. Butz, C. Dolle, C. Halbig, E. Spiecker, S. Eigler
(Siehe online unter https://doi.org/10.1002/anie.201608377) - Atomic structure of sensitive battery materials and interfaces revealed by cryo-electron microscopy, Science 358 (2017), 506–510
Y. Li, Y. Li, A. Pei, K. Yan, Y. Sun, C.-L. Wu, L.-M. Joubert, R. Chin, A.L. Koh, Y. Yu, J. Perrino, B. Butz, S. Chu, Y. Cui
(Siehe online unter https://doi.org/10.1126/science.aam6014) - Local Temperature Measurement in TEM by Parallel Beam Electron Diffraction, Ultramicroscopy 176 (2017), 161–169
F. Niekiel, S.M. Kraschewskia, J. Müller, B. Butz, E. Spiecker
(Siehe online unter https://doi.org/10.1016/j.ultramic.2016.11.028) - Revealing Nanoscale Passivation and Corrosion Mechanisms of Reactive Battery Materials in Gas Environments, Nano Lett. 17 (2017), 5171–5178
Y. Li, Y. Li, Y. Sun, B. Butz, K. Yan, A.L. Koh, J. Zhao, A. Pei, Y. Cui
(Siehe online unter https://doi.org/10.1021/acs.nanolett.7b02630)
