Structural changes during pitch-based carbon granular composites carbonisation |
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Authors: | Ana Méndez Ricardo Santamaría Marcos Granda Rosa Menéndez |
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Affiliation: | (1) Instituto Nacional del Carbón, INCAR, CSIC, C/ Francisco Pintado Fe, n°26, 33011 Oviedo, Spain;(2) Present address: Dpto. Ingeniería de Materiales, E.T.S.I.Minas-Universidad Politécnica de Madrid, C/Alenza n°4, 28003 Madrid, Spain |
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Abstract: | This article deals with the study of carbon composites behavior during their carbonization. Composites were prepared using
four granular carbons (graphite, anthracite, green petroleum coke, and foundry coke) and four pitches (a commercial impregnating
coal-tar pitch, an air-blown and two thermally treated pitches). The evolution of the optical microstructure, porosity, volume,
and weight of carbon composites was monitored at different intermediate carbonization temperatures (350, 500, 700, and finally
1000 °C). The porosity of composites increases with carbonization due to volume changes and weight loss of pitches. Weight
loss of carbon composites during their carbonization mainly depends on the pitch characteristics and it was slightly influenced
by the presence of granular carbon. On the other hand, carbon composites with the commercial coal-tar pitch and foundry coke,
anthracite, or graphite deform in the initial stages of carbonization (<350 °C) probably due to the lower porosity of the
green pellets and the high amount of low-molecular weight compounds of the pitch. Carbon composites with green petroleum coke
underwent important dimensional changes during their carbonization, expanding initially and then shrinking at temperatures
above 700 °C. The type of granular carbon strongly influenced the microstructure of the final carbon composite, as a result
of its effect on the development of mesophase. Graphite, anthracite and foundry coke delays mesophase development, whereas
green petroleum coke accelerates mesophase formation. |
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