Kinetics of graphitization within the first minute of heat treatment

Abstracts tion of pitch bonded samples are examined. For the quality level the following measurements appear to be necessary and sufficient: the true density and the volumetric CTE of individual pieces of coke isothermally reheated in the laboratory at high temperature (e.g. 1300°C); the sulphur and vanadium content; the micrographic estimation of the optical anisotropy; the ash. On the contrary, for the quality constancy the following determinations on the coke as received should be necessary and sufficient: electrical resistivity or residual hydrogen content; true density; sulphur and vanadium content; ash; particle size distribution; bulk porosity; floating in water. 139. Kinetics of graphitixation within the first minute of heat treatment E. Fitzer and S. Weisenburger (Institute fur Chemische Technik, Universitat Karlsruhe, W. Germany). To study the kinetic of graphitization within the first minute of heat treatment, an in situ X-ray technique was used which allows fast heating of the sample and measurements after SO-60set of heat treatment. Experimental data and extrapolation procedures were combined to obtain the non-isothermal contraction curve of interlayer spacing between 1700-2500°C. Evaluation of these data which represents the kinetic behaviour within the first 20-30 set of heat treatment, leads to an activation energy of 0.4 eV which is relatively low compared with values found in the later stage of graphitization (7-10 eV for heat treatment times above l-2 min up to several hours). Conclusions are drawn in respect to the mechanism of the first steps of graphitization. 140. Graphites made from seeded cokes? C. R. Kennedy and W. P. Eatherly (Metals and Ceramics Division, Oak Ridge National Laboratory$, Oak Ridge, Tenn 37830, U.S.A.). This study is to

demonstrate a method of introducing a select defect for the reduction of the coefficient of thermal expansion without reducing the mechanical integrity. This is done by seeding the coke precursor before coking. Examples of graphites made from coke using various seed materials are given. tThis work was funded by the U.S. Naval Surface Weapons Laboratory under the REVMAT Program, P.O. 4-0208. SOperated for the Energy Research and Development Administration by the Union Carbide Corporation. 141. Evidence of catalytic effect of sufphur on graphitixa-

tion between 1400 and 2000°C E. Fitzer and S. Weisenburger (Institut fur Chemische Technik, Universitat Karlsruhe, W. Germany). The catalytic effect of sulphur on graphitization was studied on petrol- and pitch cokes having sulphur contents between 0.4 and 1.7% S. The in situ measurements of interlayer spacing have shown that not only a shoulder at the high angle side of the (002) reflection can appear but that also the main part of the sample tends to graphitize partly below 170&18OO”C.The shoulder indicates as well ordered phase with an interlayer distance of 3.359 8. The

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amount of this phase within the sample is determined to be below 0.5%. The activation energy of graphitization is lowered by the catalytic effect of sulphur from 7-10 eV to about 3-4eV within 140~2OOO’C. 142. Kinetics of the graphitixatfon-induceddimensional changes of artigciai carbons K. J. Huttinger and U. Rosenblatt (Schunk & Ebe GmbH, D 63 Gieben, W. Germany). Bars 7 X 7 x 30 mm of five different artificial carbons pretreated at 1200°C were heattreated at various temperatures between 1500 and 2900°C and residence times between 0.5 and 4 hr. The shrinkage kinetics of all materials can be described by a rate law of third order in respect to the length change perpendicular to the grain orientation. However, the temperature dependence of the total shrinkage was found to be determined by the binder system used. 143. Graphitizedhigh density carbon with no pitch binder K. Kobayashi, I. Ogawa and H. Honda (National Industrial Research Institute of Kyushu, Tosu-Kyushu, Japan) and Y. Matsushita (Nippon Crucible Co., Japan).

Graphitized high density carbon was fabricated from coke powder without the use of a pitch binder phase utilizing the hot-press method by the addition of small amount of boric acid with the pressure of about 200 kg/cm’ and the temperature of about 2200°C.The bulk density was about 2.0, and the graphitization degree of the sample was accelerated by this treatment. 144. Theoretical and practical approach to influences on graphite electrodes consumption in arc furnaces (Experiencewith coated electrodes) Dr. D. Ziillner, W. Lippert, G. Klier, F. Schieber and F. Rittmann (C. Conradty, P.O. Box 480,85 Niimberg , West Germany). A detailed study of electrode consumption in arc furnaces and how to influence their individual data is given. Correct application, consideration of numerous technical procedures, construction techniques at the furnace and special machine-processing of coated electrodes are discussed. Besides considerable reduction in consumption, higher electrical load can be achieved with coated electrodes: lateral burn off is relatively well suppressed, whilst the electrical load can simultaneously be increased up to 30%. 145. The graphitixation process of different types of pyrolytic carbon obtained in low-temperaturepyrolysis of acetylene S. Jasienko and J. Machnikowski (Technical University of Wroclaw, Poland). Investigations on the graphitization of different types of pyrolytic carbons obtained during the pyrolysis of acetylene at 1000°C are carried out. Graphitizability of the examined products decreased in the direction: compact/after graphitization at 3OOO”CdW2= 3.364 A, L, = 13OOA, L,=19OOA, PH. = 2.215 g/cm3, feathery, fragile, spongy, soot-like carbon. The changes of structure parameters with graphitization temperature, proves that the graphitization occurs according to the mechanism which is typical for