Analysis of chemical structure of wood charcoal by X-ray photoelectron spectroscopy

Wood charcoal carbonized at various temperatures was analyzed by X-ray phot oelectron spectroscopy (XPS). Fourier-transform infrared spectroscopy (FTIR ), and X-ray diffractometry to investigate the changes of chemical structur es during the carbonization process. From the infrared spectra, the carbon double bonds and aromatic rings were seen to form at a carbonization temper ature of about 600 degrees C, From the XPS spectra, the ratio of aromatic c arbons increased in the temperature range 800-1000 degrees C and over 1800 degrees C. The condensation of aromatic rings proceeded as carbonization pr ogressed. The drastic reduction of electrical resistivity of charcoals was observed in almost the same temperature range. It was found that the conden sation of aromatic rings had some relation to the decline in electrical res istivity. Wood charcoal carbonized at 1800 degrees C was partly graphitized . a finding supported by the results of X-ray diffraction and XPS. The func tional groups containing oxygen diminished with the increase in carbonizati on temperature.