Abstracts 291

Mutterphase prinzipietl gut gee&net zu sein. Bei einer vergleichenden Betrachtung einer Reihe von Wach- stumsformen, die in Systemen unterschiedlicher Zusam- mensetzung und unter verschiedenartigen luBeren Be- dingungen entstanden sind, ergeben sich einige bemer- kenswerte ~bereinstimmungen im ~istallinen Habitus.

43. Glassy carbon graphitfzation: density changes D. B. Fischbach and M. E. Rorabaugh (Dept. ofMining

Metallurgical and Ceramic Engineering, FB-10, Univer- sity of Washington, Seattle, Wash. 98195, U.S.A.). Densities of several varieties of glassy carbon were measured in a ~nzene~tetrabromoethane gradient column after heat treatment in the range 800-3000°C. Density decreases occur primarily as a result of volume expansion which depends on material source, sample size, heating rate and temperature. This expansion is attributed to deformation under pressure generated within the closed porosity by desorption and continued pyrolysis.

44. Studies oa the catalytic graphitization of petroleum cokes

S. Jasienko, and L. Wajzer (Znstytut Chemii i Tech- nologii Nafty i Wegla Politechniki Wroclawskiej, ul. ~da~ska 7/9, SO-344 Wro~law, Poland).

45. Aspekte zur Charakterisierung des strukturelien Au- fbaues von R&en

E. Koberstein und M. Voll (Degussa Wolfgang, physikalisch-shenzische und anorganisch -chemische Fors~hungsabte~lung).

46. Disclination structures in the carbonaceous mesopbese J. L,. White and J. E. Zimmer (The Aerospace

Corporation, P.O. Box 92951, Los Angeles, Calif. 90009, U.S.A.). Disclinations are inherent to the lamelliform morphology of the carbonaceous mesophase and its heat-treated fossils, including coke and graphite. Optical and electron microscopy have been used to define disclination structures in coarse and deformed mesophase under various conditions of heat-treatment.

47. Characterization of oriented voids in pyrolytic graphite S. Bose and R. H. Bragg (materials and molecular

Research Divisiori, Lawrence 3e~eley Laborato~ and Department of Materials Science and Engineering, Uni- versity of California, Berkeley, Calif. 94120, U.S.A.). The orientation dependence of the small angle scattering by pyrolytic graphite has been investigated. The intensity can be interpreted in terms of the scattering by voids whose shape is oblate ellipsoids of revolution with semi-major and semi-minor axes of a and b respectively. The scattering in the Guinier region is equivalent to that of a dilute dispersion of oriented “Guinier spheres” whose radius is H\l$(a2sin2 y + b2cosZ~)“2, where y is the angle between b and the scattering vector h.

48. Explanation of “unorganized carbon” in gtassy carbon S. Bose and R. H. Bragg (Materials and Molecular

Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Engineering, Uni- versity of California, Berkeley, Calif 94720, U.S.A.).

X-ray diffraction studies of glassy carbon (CC) in which the collimation of the incident and diffracted beams, and the specimen thickness were varied indicate that: (1) small angle scattering is the most prominent feature of the diffraction pattern and is at least two orders of magnitude stronger than the 002 interference maximum; (2) the excess intensity below the 002 maximum, sometimes attributed to “unorganized carbon” or “misaligned single layers,” is merely the high angle part of the small angle scattering; and (3) the data obtained in reflection are shifted significantly towards smaller values of 28 whereas the line profiles obtained in transmission are relatively undistorted.

49. Informations dCduites de I’analyse de la diffusion des rayons X aux petits angles dans I’btude des carbones

D. Tchoubar et C. H. Pons (Centre de Recherche sur les Solides & O~anisation C~stalline i~pa~aits, C.N.R.S., Rue de la Ferollerie. 4.5045 Orl~ans-C~dex, France). By taking into account the instrumental aberrations in the experimental small angle X-ray scattering curves, it has been possible to refine the description of the porosity in the desordered carbons. The relation between the structural evolution of the layer stakings and the modification of the porosity, during the ~aphitization, is illustrated for a sample of petroleum coke.

50. A microscopic examination of coke structure using an automatic image analysis system

J. W. Patrick, M. J. Sims and A. E. Stacey (British Carbonization Research Association, Cheste~eld, Derby- shire, S42 6JS, England). Cokes prepared on both the large scale and on the laboratory scale were examined by reflected light microscopy and the structure was analyzed by use of a computerized image analysis system. Determinations were made of the total porosity, the mean size and size dis~bution (based on ho~zontal chords) of pores and pore-walls, the pore perimeter and the number of pores. For the laboratory-prepared cokes correlations were found between the coke tensile strength and several of the structural parrameters but these relations were less clearly defined for the cokes prepared on the commercial scale.

51. Einsatz der quantitativen Bldanalyse zur Charak- terisierung von G&t und Fyrokoblenstoff

K. Koizlik, W. Delle, H. Hoven und H. Uhlenbruck, (Institut fiir Reaktorwerkstofe der Kemforschungsanlage Jiilich, D-517 Jiilich, Postfuch 1913). The porosity of reactor graphites and pyrocarbons in~uences decisively their irradiation behaviour and fission product retention during operation in High Temperature Reactors (HTR’s). For the evaluation of total number, total volume and size distribution of macropores for the reason of quality control an automatic, quantitative image analyser is used. The measured variables correlated with the mentioned material parameters are defined, the mathematical opera- tions for the correction of measured values and for the calculation of material parameters are discussed, Finally, first experimental and mathematical results are presented in the case of pyrocarbon.