Quantitative structural and textural assessment of laminar pyrocarbons through Raman spectroscopy, electron diffraction and few other techniques

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• 作者：Jean-Marie Vallerot ; Xavier Bourrat ; Arnaud Mouchon and Georges Chollon
• 关键词：Pyrolytic carbons ; Optical microscopy ; Raman spectroscopy ; Electron energy-loss spectroscopy
• 刊名：Carbon
• 出版年：2006
• 出版时间：August 2006
• 年：2006
• 卷：44
• 期：9
• 页码：1833-1844
• 全文大小：806 K

文摘

In pyrocarbon materials, the width of the Raman D band (FWHM_D) is very sensitive to low energy structural defects (e.g., disorientations of the graphene layers). The correlation between the two parameters, FWHM_D and OA (as derived from selected area electron diffraction: SAED), has allowed to differentiate various pyrocarbons unambiguously. Furthermore, the optical properties of pyrocarbons, i.e., the extinction angle, the optical phase shift and the ordinary and extraordinary reflectance, have been accurately determined at 550 nm by means of the extinction curves method. These results are completed by in-plane and out-of-plane dielectric constant measurements by angular resolved EELS. Moreover, the hybridization degree of the carbon atoms has been assessed by the same technique. About 80 % of the carbon atoms of the pyrocarbons have a sp² hybridization. The lack of pure sp² carbon atoms, as compared to graphite, might be explained by the presence of sp³-like line defects.