In order to clarify whether carbon products deposited on smoked tiles are catalytically graphitized in the manufacturing process, some clay minerals and related substances were examined on their abilities to promote catalytic graphitization. These compounds were added by 20 w/o into carbon black and carbon powders derived from phenol formaldehyde resin, followed by heat-treatment at various temperatures from 900°C to 2200°C under nitrogen gas.
The catalytic graphitization was observed more remarkably in phenolic resin carbon than in carbon black. The phenolic resin carbons containing the clay minerals were catalytically graphitized in the two stages which were observed at 1200-1500°C and at 2200°C respectively. The catalytic effect was slightly detectable in the first stage but remarkably pronounced in the second stage, while it was not observed at all in the temperature range below 1200°C. On the other hand, the carbon product deposited on the surface of smoked tile exhibited the same appearance as that of the isotropic pyrolytic carbon produced at a low temperature, and its crystallite thickness was estimated to be only 18Å. From these results and the fact that the smoked tile is generally manufactured at temperatures below 1000°C, it was concluded that carbon on the smoked tile is not subject to the catalytic graphitization at the temperature range used in the manufacturing process.
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