Correlative 3D-Characterization of Liquid Metal Catalysts (LMC) utilizing X-ray and Analytical Electron Microscopy

Beitrag bei einer Tagung
(Konferenzbeitrag)


Details zur Publikation

Autor(en): Wirth J, Englisch S, Wiktor C, Taccardi N, Wasserscheid P, Spiecker E
Herausgeber: Microscopy Society of America 2018
Jahr der Veröffentlichung: 2018
Tagungsband: Microscopy & Microanalysis 2018
Seitenbereich: 556-557
Sprache: Englisch


Abstract

X-ray microscopy (XRM) allows non-destructive 3D
investigations of materials across multiple length scales. At the University of
Erlangen-Nürnberg a high-resolution XRM/NanoCT instrument (ZEISS Xradia 810
Ultra) has been recently installed and put into  operation. The instrument uses Fresnel zone plate
optics to achieve 3D resolutions down to 50 nm and can be equipped with a
Zernike phase ring enabling phase contrast in addition to standard absorption
contrast imaging. While the latter is well suited to image materials containing
regions of sufficiently different densities the former can be employed to study
weakly absorbing materials and to discriminate materials exhibiting similar
densities. Due to the high resolution capabilities and flexible contrast the
ZEISS Xradia 810 Ultra can be combined with Scanning Electron Microscopy (SEM) and
Transmission Electron Microscopy (TEM) techniques for correlative 3D studies of
functional materials.



 



In this
contribution we report correlative 3D studies of Pd-Ga liquid metal catalysts
which have been recently shown outstanding performance in alkane dehydrogenation
and, in particular, high resistance against coking [1]. Such liquid metal
catalysts exhibit a complex material structure featuring a molecularly defined,
catalytically active liquid film/droplet layer adsorbed on meso- or macroporous
silica. High-resolution 3D characterization across different length scales is
required to gain deeper insight into the structure and microscopic mechanisms
of the catalyst system. SEM imaging (Fig. 1a) and corresponding Energy- Dispersive
X-ray Spectroscopy (EDXS) analysis (not shown) reveal the presence of larger Ga-rich
particles on the surface of the porous silica but do not allow to clarify to which
extend Ga and Pd is incorporated in the bulk of the porous network. By combining
absorption and phase contrast imaging in the XRM the metal droplets and the
macroporous silica network can be independently resolved. Tomographic
reconstruction enables non-destructive characterization of the 3D distribution of
metal droplets in the porous network structure (Fig. 1b).



 



In order to study the composition of individual metal
droplets inside the porous network site-specific sample preparation has to be
combined with high-resolution analytical TEM techniques. Fig. 1c) exemplarily
shows a Scanning Transmission Electron Microscopy (STEM) image of a mesoporous silica
network containing a single Pd-Ga particle. The corresponding EDXS mapping
clearly shows that the particle has a bimetallic structure with Pd-rich and Ga-rich
parts occurring in direct contact to each other. Currently, we perform in situ TEM
experiments in order to reveal phase transformations and melting behavior of
such bimetallic particles upon heating to typical process temperatures of ~ 500
°C.


FAU-Autoren / FAU-Herausgeber

Englisch, Silvan
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Spiecker, Erdmann Prof. Dr.
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Taccardi, Nicola Dr.
Lehrstuhl für Chemische Reaktionstechnik
Wasserscheid, Peter Prof. Dr.
Lehrstuhl für Chemische Reaktionstechnik
Wiktor, Christian Dr.
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Wirth, Janis
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)


Zusätzliche Organisationseinheit(en)
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Graduiertenkolleg 1896/2 In situ Mikroskopie mit Elektronen, Röntgenstrahlen und Rastersonden


Zitierweisen

APA:
Wirth, J., Englisch, S., Wiktor, C., Taccardi, N., Wasserscheid, P., & Spiecker, E. (2018). Correlative 3D-Characterization of Liquid Metal Catalysts (LMC) utilizing X-ray and Analytical Electron Microscopy. In Microscopy Society of America 2018 (Eds.), Microscopy & Microanalysis 2018 (pp. 556-557). Saskatoon, Saskatchewan, Canada, CA.

MLA:
Wirth, Janis, et al. "Correlative 3D-Characterization of Liquid Metal Catalysts (LMC) utilizing X-ray and Analytical Electron Microscopy." Proceedings of the 14th International Conference on X-ray Microscopy (XRM2018), Saskatoon, Saskatchewan, Canada Ed. Microscopy Society of America 2018, 2018. 556-557.

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Zuletzt aktualisiert 2018-27-09 um 09:15