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Effects of excess carbon and vibrational properties in ultrafine SiC powders

Effects of excess carbon and vibrational properties in ultrafine SiC powders,10.1051/epjap:1999236,European Physical Journal-applied Physics,S. Charpe

Effects of excess carbon and vibrational properties in ultrafine SiC powders   (Citations: 4)
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Structural and vibrational properties are investigated in SiC nanopowders synthesized by a CO2 laser pyrolysis of (SiH4, C2H2) gaseous mixture and thermally treated up to 1800 °C. The structural modifications of the SiC crystallites and the arrangement of the carbon in excess are monitored at different annealing stages. A critical behaviour is revealed in the powder annealed at T_a = 1500 °C through the features of the Raman spectra and the insulating-conductor transition. The significant electric conductivity (sigma ≈ 0.05 S cm^{-1}) which appears above T_a is discussed with respect to the powder composition and the interface effects where the carbon in excess seems to play a key role.
Journal: European Physical Journal-applied Physics - EUR PHYS J-APPL PHYS , vol. 8, no. 2, pp. 111-121, 1999
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    • ...For npSiC, it was already reported by TEM observations, Raman spectroscopy, and EPR measurements that a low displacement of the chemical composition from the stoichiometry induces species in excess to be localized at the nanoparticle surface (Charpentier et al., 1999a; Kassiba et al., 2002a)...
    • ...On the other side, in presence of a carbon-rich sample (C/Si > 1), thin free-carbon sheets (amorphous or graphitic) are localized partially or all over the particle surface (Charpentier et al., 1999a; Kassiba et al., 2002a)...
    • ...also expect to find the paramagnetic defects in the carbon-rich sheets covering the particles (Charpentier et al., 1999a)...

    J. Boucléet al. Influence of silicon and carbon excesses on the aqueous dispersion of ...

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