TEM Gas Heating sample holder – Fe-alloy catalysts facilitate C nanotube CVD

How can alloying of Fe catalysts enhance carbon nanofiber and nanotube growth?

Andrew Meng and Eric Stach from the University of Pennsylvania, along with colleagues from Vanderbilt University and the Toyota Research Institute of North America published recent work using the Hummingbird Scientific TEM gas heating sample holder to characterize the effect of three different Fe-based alloy catalyst systems on the in-situ atmospheric pressure chemical vapor deposition (CVD) of carbon nanotubes (CNT) and nanofibers (CNF) in the transmission electron microscope (TEM) using ethylene.

a) TEM image timelapse images of in-situ growth on 1 nm Fe/10 nm Al₂O₃ sputtered onto sample chips exposed to trace Na₂CO₃; the blue ovals highlight the high-aspect-ratio CNFs. b) TEM timelapse images of in-situ CNF growth from H₂/C₂H₄: 5/2 on 40–60 nm drop-casted stainless steel 316L nanoparticles. Copyright © 2026 AIP Publishing LLC

Compared to pure Fe, Cr and Na alloying additions improved the robustness of CNF and CNT growth, facilitating catalyst reduction by acting as a O₂ getter and a desiccant, respectively. Characterization of grown structures in experimental gas mixtures at high temperatures was enabled by the Hummingbird Scientific in-situ TEM gas heating sample holder as well as ex-situ scanning TEM (STEM)with electron energy loss spectroscopy (EELS) which demonstrated the important role that the oxidation state of the catalyst plays in CNT growth. The reduction of the already oxidized catalyst is thought to be the primary challenge of atmospheric pressure CNT and CNF growth which the results demonstrate potential strategies to overcome.

Reference: Andrew C. Meng, Peifu Cheng, Piran R. Kidambi, Nikhilendra Singh, Yuyang Song, Eric A. Stach, J. Vac. Sci. Technol. B 43 040601 (2025) DOI: 10.1116/6.0004664

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