The Structure and Chemical Composition of the Cr and Fe Pyrolytic Coatings on the MWCNTs’ Surface According to NEXAFS and XPS Spectroscopy
by
Danil Sivkov 1,2,*, Olga Petrova 2, Alena Mingaleva 1,2, Anatoly Ob’edkov 3, Boris Kaverin 3, Sergey Gusev 4
, Ilya Vilkov 3, Sergey Isaenko 2, Dmitriy Bogachuk 2, Roman Skandakov 2, Viktor Sivkov 2 and Sergey Nekipelov 2
Danil Sivkov 1,2,*, Olga Petrova 2, Alena Mingaleva 1,2, Anatoly Ob’edkov 3, Boris Kaverin 3, Sergey Gusev 4, Ilya Vilkov 3, Sergey Isaenko 2, Dmitriy Bogachuk 2, Roman Skandakov 2, Viktor Sivkov 2 and Sergey Nekipelov 2
1
Federal State Budgetary Educational Institution of Higher Education “Saint-Petersburg State University”, 199034 St. Petersburg, Russia
2
Komi Science Center Ural Division of the Russian Academy of Sciences, 167982 Syktyvkar, Russia
3
G.A.Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia
4
Institute for Physics of Microstructures of the Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(2), 374; https://doi.org/10.3390/nano10020374
Received: 3 February 2020 / Revised: 16 February 2020 / Accepted: 19 February 2020 / Published: 21 February 2020
(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)
The paper is devoted to the structure and properties of the composite material based on multi-walled carbon nanotubes (MWCNTs) covered with pyrolytic iron and chromium. Fe/MWCNTs and Cr/MWCNTs nanocomposites have been prepared by the metal organic chemical vapor deposition (MOCVD) growth technique using iron pentacarbonyl and bis(arene)chromium compounds, respectively. Composites structures and morphologies preliminary study were performed using X-ray diffraction, scanning and transmission electron microscopy and Raman scattering. The atomic and chemical composition of the MWCNTs’ surface, Fe-coating and Cr-coating and interface—(MWCNTs surface)/(metal coating) were studied by total electron yield method in the region of near-edge X-ray absorption fine structure (NEXAFS) C1s, Fe2p and Cr2p absorption edges using synchrotron radiation of the Russian-German dipole beamline (RGBL) at BESSY-II and the X-ray photoelectron spectroscopy (XPS) method using the ESCALAB 250 Xi spectrometer and charge compensation system. The absorption cross sections in the NEXAFS C1s edge of the nanocomposites and MWCNTs were measured using the developed approach of suppressing and estimating the contributions of the non-monochromatic background and multiple reflection orders radiation from the diffraction grating. The efficiency of the method was demonstrated by the example of the Cr/MWCNT nanocomposite, since its Cr2p NEXAFS spectra contain additional C1s NEXAFS in the second diffraction order. The study has shown that the MWCNTs’ top layers in composite have no significant destruction; the MWCNTs’ metal coatings are continuous and consist of Fe3O4 and Cr2O3. It is shown that the interface between the MWCNTs and pyrolytic Fe and Cr coatings has a multilayer structure: a layer in which carbon atoms along with epoxy –C–O–C– bonds form bonds with oxygen and metal atoms from the coating layer is formed on the outer surface of the MWCNT, a monolayer of metal carbide above it and an oxide layer on top. The iron oxide and chromium oxide adhesion is provided by single, double and epoxy chemical binding formation between carbon atoms of the MWCNT top layer and the oxygen atoms of the coating, as well as the formation of bonds with metal atoms.
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Keywords:
NEXAFS; XPS; MOCVD; total electron yield; multi-walled carbon nanotubes; nanocomposite; (pyrolytic Cr)/MWCNTs; (pyrolytic Fe)/MWCNTs
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MDPI and ACS Style
Sivkov, D.; Petrova, O.; Mingaleva, A.; Ob’edkov, A.; Kaverin, B.; Gusev, S.; Vilkov, I.; Isaenko, S.; Bogachuk, D.; Skandakov, R.; Sivkov, V.; Nekipelov, S. The Structure and Chemical Composition of the Cr and Fe Pyrolytic Coatings on the MWCNTs’ Surface According to NEXAFS and XPS Spectroscopy. Nanomaterials 2020, 10, 374.
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