Decomposition of Fe5C2 catalyst particles in carbon nanofibers during TEM observation

• Published in: Science and technology of advanced materials Vol. 10; no. 1; p. 015004
• Main Authors: Blank, Vladimir D, Kulnitskiy, Boris A, Perezhogin, Igor A, Alshevskiy, Yuriy L, Kazennov, Nikita V
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 2009; IOP Publishing; Taylor & Francis Group
• Subjects: carbon nanofiber; electron beam; HRTEM; iron carbide
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1088/1468-6996/10/1/015004

The effect of an electron beam on nanoparticles of two Fe carbide catalysts inside a carbon nanofiber was investigated in a transmission electron microscope. Electron beam exposure does not result in significant changes for cementite (θ-Fe
3
C). However, for Hägg carbide nanoparticles (χ-Fe
5
C
2
), explosive decay is observed after exposure for 5-10 s. This produces small particles of cementite and γ-Fe, each covered with a multilayer carbon shell, and significantly modifies the carbon-fiber structure. It is considered that the decomposition of Hägg carbide is mostly due to the damage induced by high-energy electron collisions with the crystal lattice, accompanied by the heating of the particle and by mechanical stress provided by the carbon layers of the nanofiber.