40. Air oxidation replaced by SO2 treatment in pan-precursor-carbon-fibres preparation

2%

Abstracts

capacitance of a carbon fiber bundle immersed in an aqueous electrolyte is described. The measured relative capacitances of various treated and untreated commercial carbon fibers are shown to be related to the area and the activity of their surfaces, and to the shear strength of composites made from these fibers. 34. Photoelectron spectroscopic studies of chemisorption on carbon surfaces

P. Cadman, J. D. Scott and J. M. Thomas (The University College of Wales, Edward Davies Chemical Laboratories, Aberystwyth SY23 1NE, U.K.). 35. A tietic study of gasification by molecular oxygen, of graphitizing carbons of increasing HTT D. W. Taylor and H. Marsh (Northern Coke Research Laboratories, University of Newcastle upon Tyne, New castle upon Tyne, NE1 7RU, England). The kinetics of

gasification by molecular oxygen of a heat treatment series (1200-3200°K) of a graphitizing carbon prepared from polyvinyl acetate have been studied in the temperature range 750-1000°K. A correspondence between the activation energy for the reaction and the residual hydrogen content of the carbon was observed, the hydrogen ,apparently acting in a catalytic role. 36. The effect of heat-treatment on the reaction of a porous carbon with carbon dioxide B. McEnaney and M. Willis (School of Materials Science, University of Bath, BA2 7AY, England). 37. Pores structure effects in radiolytic oxidation of graphite J. V. Best, A. J. Wickham and C. J. Wood (Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire, U.K.). Consider-

able developments have taken place during the past two years in the understanding of the effect of pore structures on the rate of the radiation-induced oxidation of graphites in CO, cooled nuclear reactors. This paper discusses the present position with particular reference to the assumptions that are necessary, given the present state of knowledge, in order to model the radiolytic oxidation reaction. Experiments designed to throw further light on the subject are outlined. 38. Pore structure and the reactivity of graphite3 P. Campion (UKAEA, Reactor Fuel Element Laboratories, Springfields, Preston, Lancashire, England) and R. J. Blanchard (CEA Centre d’Etudes Nuclt?aires,Grenoble, France). Reactions between radiol-

ysed gas and porous solids are particularly interesting because the reactant is produced within the pore structure. Among radiolytic systems, the carbon dioxide/graphite system has been studied extensively, both with and without inhibitors and, in this paper, some of the major observations from pore structure modfications prior to and during radiolytic oxidation are discussed.

39. Effet catalytique du nickel dans I’hydrogknation des charbons J. Weber et M. Bastick (Laboratoire de Physico-Chimie Industrielle, ENSIC, 1, rue Grandville, 54042 NancyCedex, France). En prCsence de nickel, l’hydrog6nation

du carbone peut &tre rCalisCe, sous la pression atmosph&ique & des tempkratures infkrieures & lOOOY!. Elle conduit g la formation d’un produit de rCaction unique: le mBthane. Celui-ci apparait dans deux domaines bien distincts: d’une part, entre 400 et 650°C et d’autre part, au-deli de 750°C. Alors que la reaction catalyske B haute tempirature ne prksente pas de caracttre particulier, celle qui est observee entre 400 et 650°C est un phCnomtne transitoire. La disparition de ce ph&om&ne doit &tre attribuC g une modification du catalyseur plutBt qu’g I’hydrogCnation sClective de la phase la plus reactive du carbone. 40. Air oxidation replaced by SO, treatment in panprecursor-carbon-fibres preparation

V. RaSkoviC, I. Deiarov and S. MarinkoviC (Materials Science Department, Boris KidriE Institute, BeogradVinEa, Yugoslavia). Temperature dependence of the

processes occuring during SO, treatment of PAN fibres has been studied. At 225°C occurs an exothermic reaction and begins shrinkage of the fibres, indicating cyclization. The amount of cyclization is considerably greater than in the case of oxidation, as is suggested by the DTA. X-ray diffraction shows at the same temperature disordering of the PAN structure and formation of a ladder polymer, which occurs together with an increase of fibre diameter, 0 IR spectroscopy indicate formation of &S-C groups in the fibre structure. Secondary modulus and extension before breaking values of the SO, treated fibres indicate intermolecular crosslinking, with S atoms probably forming bridges. Both stren’gth and modulus are considerably higher for carbon fibres produced from the SO, treated-, than from oxidized PAN fibres. 41. A study of the structure and gasification by carbon dioxide of carbon composites (blends)

D. W. Taylor and H. Marsh (Northern Coke Research Laboratories, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, England). The morphology

before and after gasification by carbon dioxide, of the components of laboratory prepared carbon composites has been investigated by optical microscopy. The results are interpreted in terms of relative layer plane alignments observed at the interfaces between the components of the composite. Iv. STRUCTURE ANDGRAPAITIZATION 42. Kristallisationsformen des Graphitiscben Kohlenstoffs H. B. Haanstra and W. F. Knippenberg (Philips Research Laboratories, Eindhoven, Niederlande) and B. Lersmacher (Philips GmbH Forschungslaboratorium Aachen, D-5000 Aachen). Filr das Studium der fun-

damentalen Prozesse des Kristallwachstums von elementarem Kohlenstoff scheinen Systeme mit disperser Kohlenstoffverteilung in fester, fliissiger oder gasfiirmiger