Annealing-induced structural changes of carbon onions: High-resolution transmission electron microscopy and Raman studies

The first- and second-order Raman spectra of carbon nano-onions (CNOs), produced via annealing of detonation nanodiamonds with a mean grain size of ∼5nm in the argon ambience at the maximal temperature of annealing process (TMAX) varying from 1500 to 2150°C, are analyzed together with the high-resol...

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Bibliographic Details
Published in:Carbon (New York) 2014-07, Vol.73, p.78-86
Main Authors: Bogdanov, Kirill, Fedorov, Anatoly, Osipov, Vladimir, Enoki, Toshiaki, Takai, Kazuyuki, Hayashi, Takuya, Ermakov, Victor, Moshkalev, Stanislav, Baranov, Alexander
Format: Article
Language:English
Subjects:
Annealing
Carbon
Crystal defects
Diamonds
Electron microscopy
Grain size
Nanoparticles
Nanostructure
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Summary:The first- and second-order Raman spectra of carbon nano-onions (CNOs), produced via annealing of detonation nanodiamonds with a mean grain size of ∼5nm in the argon ambience at the maximal temperature of annealing process (TMAX) varying from 1500 to 2150°C, are analyzed together with the high-resolution transmission electron microscopy (HRTEM) images. The combined analysis provides a deep insight into the annealing-induced atomic-scale structural modifications of the CNO nanoparticles. The Raman and HRTEM data unambiguously demonstrate the reduction in the number of defects in the CNO structure, as well as indicate the conversion from the diamond sp3-bonded carbon phase to the sp2-bonded carbon phase with increasing TMAX and its almost full completion for TMAX=1600°C.
ISSN:0008-6223
1873-3891
DOI:10.1016/j.carbon.2014.02.041