In Situ and Ex Situ X-ray Diffraction and Small-Angle X-ray Scattering Investigations of the Sol-Gel Synthesis of Fe3N and Fe3C.

Chambers, MS; Hunter, RD; Hollamby, M; Pauw, BR; Smith, AJ; Snow, T; Danks, AE; Schnepp, Z

Abstract

Iron nitride (Fe3N) and iron carbide (Fe3C) nanoparticles can be prepared via sol-gel synthesis. While sol-gel methods are simple, it can be difficult to control the crystalline composition, i.e., to achieve a Rietveld-pure product. In a previous in situ synchrotron study of the sol-gel synthesis of Fe3N/Fe3C, we showed that the reaction proceeds as follows: Fe3O4 ? FeOx ? Fe3N ? Fe3C. There was considerable overlap between the different phases, but we were unable to ascertain whether this was due to the experimental setup (side-on heating of a quartz capillary which could lead to thermal gradients) or whether individual particle reactions proceed at different rates. In this paper, we use in situ wide- and small-angle X-ray scattering (wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS)) to demonstrate that the overlapping phases are indeed due to variable reaction rates. While the initial oxide nanoparticles have a small range of diameters, the size range expands considerably and very rapidly during the oxide-nitride transition. This has implications for the isolation of Rietveld-pure Fe3N, and in an extensive laboratory study, we were indeed unable to isolate phase-pure Fe3N. However, we made the surprising discovery that Rietveld-pure Fe3C nanoparticles can be produced at 500 °C with a sufficient furnace dwell time. This is considerably lower than the previous reports of the sol-gel synthesis of Fe3C nanoparticles.

Citation

Chambers, M., Hunter, R., Hollamby, M., Pauw, B., Smith, A., Snow, T., …Schnepp, Z. (2022). In Situ and Ex Situ X-ray Diffraction and Small-Angle X-ray Scattering Investigations of the Sol-Gel Synthesis of Fe3N and Fe3C. Inorganic Chemistry, 61(18), 6742-6749. https://doi.org/10.1021/acs.inorgchem.1c03442

• Journal Article Type: Article
• Acceptance Date: Apr 26, 2022
• Online Publication Date: Apr 26, 2022
• Publication Date: May 9, 2022
• Publicly Available Date: May 9, 2022
• Journal: Inorganic Chemistry
• Print ISSN: 0020-1669
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 61
• Issue: 18
• Pages: 6742-6749
• DOI: https://doi.org/10.1021/acs.inorgchem.1c03442
• Public URL: https://keele-repository.worktribe.com/output/423041
• Publisher URL: https://pubs.acs.org/doi/10.1021/acs.inorgchem.1c03442