Characterization of sp2- and sp3-bonded carbon in wood charcoal |
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Authors: | Kengo Ishimaru Toshimitsu Hata Paul Bronsveld Takashi Nishizawa Yuji Imamura |
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Affiliation: | (1) Daiwa House Industry Co. Ltd., 6-6-2 Sakyo, Nara 631-0801, Japan;(2) Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;(3) Department of Applied Physics, University of Groningen, 9747 AG Groningen, The Netherlands;(4) Polymer Electrolyte Fuel Cell Cutting-Edge Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064, Japan |
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Abstract: | Japanese cedar (Cryptomeria japonica) preheated at 700°C was subsequently heated to 1800°C and characterized by electron microscopy, X-ray diffraction, and micro-Raman spectroscopy. The degree of disorder of carbon crystallites and the amount of amorphous phase decreased considerably with an increase in heat treatment temperature to 1400°C, while carbon crystallites clearly developed above this temperature, showing that the microstructure of carbonized wood undergoes drastic changes around 1400°C. Besides showing the bands for sp2-bonded carbon, the Raman spectra showed a shoulder near 1100 cm−1 assigned to sp3-bonded carbon. With an increase of heat treatment temperature, the peak position of the Raman sp3 band shifted to a lower frequency from 1190 to 1120 cm−1, which is due to the transformation of sp3-bonded carbon from an amorphous phase to a nanocrystalline phase. These data showed that the microstructure of carbonized wood from 700° to 1800°C consisted of the combination of sp2- and sp3-bonded carbon, which is probably due to the disordered microstructure of carbonized wood. It is suggested that the sp3-bonded carbon is transformed from an amorphous structure to a nanocrystalline structure with the growth of polyaromatic stacks at temperatures above 1400°C. |
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Keywords: | Charcoal Carbonization Microstructure Raman spectroscopy |
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