X-ray diffraction study of the evolution of Fe-filled multiwalled carbon nanotubes under pressure

Abstract

We present in situ high pressure X-ray diffraction experiments on multi-walled carbon nanotubes (MWNTs) filled with iron-based nanowires. In addition to our diffraction results, we provide a detailed characterization of our samples in terms of nanotube length, iron contents, nanotube number of walls and radial dimension. Both carbon nanotubes and encapsulated iron-based nanowires were found to be stable under high pressure conditions, in contrast with previous experiments performed on Fe-filled MWNTs where structural transitions of nanotubes and Fe3C nanowires were recorded around 9 GPa. We point out the importance of providing a complete structural characterization of the studied material and we propose an explanation for the contradictory results found in the literature based on different structural characteristics of the samples and on recent results on the non-hydrostaticity of some pressure transmitting media.