In situ observation of phase transformation in iron carbide nanocrystals.

Author(s) Cuong, L.Thanh; Dung, N.Duc; Tuan, T.Quoc; Khoi, N.Thi; Huy, P.Thanh; Ha, N.Ngoc
Journal Micron
Date Published 2018 Jan

This paper reports on the in situ observation of phase transformation in an iron carbide nanocrystal encapsulated in a graphitic shell by means of high resolution transmission electron microscopy (HR-TEM). A Fe7C3 nanocrystal in orthorhombic (o-Fe7C3) structure with carbon graphitic cover is captured at the initial time of the experiment. Under the projection of a high-energy electron beam (200kV), the graphitic carbon layer evaporates gradually and structural changes in orthorhombic (o-Fe7C3) crystal manifests simultaneously. Specifically, changes in crystal direction happens first and then the crystal structure switching between orthorhombic and hexagonal (h-Fe7C3) follows. Details analysis and conclusive evidences of the phase structure and transformation are presented and discussed. The appearance of o-Fe7C3 structure is captured for about 92min over 100min of observation, indicating the preference of o-Fe7C3 form over h-Fe7C3 form.

DOI 10.1016/j.micron.2017.10.009
ISSN 1878-4291
Citation Micron. 2018;104:6165.

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