65. Kinetics of carbon crystallite growth during graphitization

✍ Scribed by E.S. Bale

• Publisher: Elsevier Science
• Year: 1965
• Tongue: English
• Weight: 141 KB
• Volume: 3
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(65)90131-4

✦ Synopsis

During the first stage, ordering occurred without decrease in L,. The second stage of ordering was associated with a sharp increase in L, and preferred orientation, and with changes in microstructure. The effective activation energy was found to be 26Of20 kcaljmole for both stages. For some pyrolytics, a fairly narrow continuous distribution of rate processes was required to fit the observations, and separate stages were not always resolved in these cases. However, the effective activation energy was the same. Petroleum coke, coked coal tar pitch and a composite of the two (all pretreated N 15 minutes at ZOOO'C) were studied over the treatment temperature range of 2200-2900°C. Within experimental error all three graphitized at the same rates with the possible exception of a small portion (N 15%) of the composite. The behavior of these carbons could be represented by a superposition of first order rate processes with a broad distribution of rate constants. Under the assumption that the distribution occurred entirely in the pre-exponential factors, an effective activation energy of -260 kcal/mole was obtained for these carbons also. Reasons for a range of pre-exponential factors will be discussed. *This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract NAS7-100 sponsored by the National Aeronautics and Space Administration.