Morphological characteristics of Quercus variabilis charcoal prepared at different temperatures
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The morphology of charcoals was investigated by scanning electron microscopy. Charcoal of Quercus variabilis was prepared in an electric furnace under nitrogen gas atmosphere at 400, 600, 800 and 1,000°C. Charring temperature greatly affects the structure of charcoal. In charcoal prepared at 400°C, most of the morphological characteristics remained relatively unchanged with the exception of the cell-wall layering. The cell walls appeared homogenous and glass-like. Above 400°C, there was an increase in cell-wall thinning and volumetric shrinkage with an increase in the charring temperature. These two factors were responsible for most of the observed changes in structure. Fracture surfaces became increasingly rough and disrupted. Vessel elements were increasingly distorted and tyloses disintegrated with increases in temperature. Parenchyma cells exhibited greater shrinkage except at the pits. This resulted in the appearance of distinctive small protuberances over the surface of the parenchyma cells. Rhomboidal calcium crystals were found to be abundant at all the temperatures studied, but at 800 and 1,000°C the crystals had a sponge-like appearance.
KeywordsCharcoal Vessel Element Volumetric Shrinkage Small Protuberance Honeycombed Appearance
This work was supported by Kangwon National University Grant [3004113-1-1(2004494)].
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