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The defect theory of carbon structure
ABSTRACTS 116. Multiple
X-ray small-angle
545
scattering of porous carbon materials
R. Perret and W. Ruland (Union Carbide European Research Associates, S.A., Rue Gatti de Gamond 95,118O Bruxelles, Belgium). Luzzati’s method for the evaluation of multiple X-ray small angle scattering has been revised and completed. Under the usual experimental conditions multiple scattering occurs practically in all cases in which the produce of the average pore size (in A) and the volume fraction of pores is larger than 10. The information obtainable from multiple scattering can, under appropriate experimental conditions, be as complete as that from single scattering. Absolute measurements are easier to carry out with multiple scattering than with single scattering. 117. Preferred lattice orientation and three-dimensional crystallinity in some carbon fibers S. Ergun (U.S. Bureau of Mines, Pittsburgh, Pennsylvania). It has been found that some carbon fibers derived from acrylic yarns show an extensive degree of orientation of the graphitic layer lattice such that the two-dimensional (10) lines tend to be parallel to the fiber axis. Such fibers also give rise to strong three-dimensional (112) reflections. From a study of five fibers it is concluded that carbon fibers are indeed polymers. 118. Interactions
between Halogen
impurities
and stacking faults in graphite
M. Saito (School of Medicine, Nihon University, Tokyo, Japan) and T. Tsuzuku (College of Science and Engineering, Nihon iiniversity, Tokyo, Japan). By means of the transparent electron microscopy, the temperature dependence of the stacking fault width in pure and halogen-doped graphites has been investigated in the range 90-300°K. It has been found that the dopants lower the stacking fault energy itself as well as the temperature dependence. Some quantitative discussions are given on the bases of theoretical models for chemical and elastic interactions. 119. Paracrystalline
distortions
in carbon blacks
L. L. Ban and W. M. Hess (Cities Service Company, Petrochemicals Research, Drawer 4, Cranbq, brew Jersey). Short range graphitic order of carbon blacks is analyzed by using optical Fourier analysis of high resolution phase contrast electron microscope images. Interlayer distortions are measured and used to follow changes occurring with graphitization. From the knowledge of interlayer distortions the density of these carbons is predicted. 120. Microstructure of carbons: a high resolution electron microscopy study L. L. Ban and W. M. Hess (Cities Service Company, Petrochemicals Research, Drawer 4, Cransbury, New Jersey). Representative samples of different carbons: coals, chars and vacuum evaporated carbon films are analyzed using high resolution phase-contrast electron microscop!,. Changes in microstructure with low and high temperature treatments, i.e. beloll: and above IOOOY~., are studied. 121. The effect of thermal expansion
anisotropy
on the strength of carbon fibers
and R. J. Diefendorf (Rensselaer Polytechnic Institute, Materials Division, Troy, ,$‘ew York). Increasing heattreatment temperature of fibers was shown to increase the degree of- radial and axial ordering of the basal planes, that is, the three dimensional structure of the fibers. A variation in the fracture mechanics of the fiber was shown to result and this was related to the changes that occur in both strength and modulus, of these fibers, with heattreatment temperature. C. W. LeMaistre
122. The defect theory of carbon structure S. Ergun (U.S. Bureau of Mines, Pittsburgh, Pennsylvania). In most carbons the existence of small crystallites having sizes indicated by the line widths of their X-ray diffraction profile is often not substantiated by small-angle X-ray scattering intensities nor by electron-microscopic observations. It is shown that they are made up of very large but defective layers. By the defect theory the line widths of the (hk0) profiles are a measure of the mean defect-free distance and not of the extent of the layers. Similarly the line-width of the (001) reflections is a measure of the number of fault-free parallel layer sequences and not of the extent of stratification (stacking height). The defect theory is critically tested by examining the small angle and high angle X-ray scattering profiles of several types of carbons. 123. The structure of polymeric carbons G. M. Jenkins and K. Kawamura (University College of Swansea, Swansea, Glamorgan, IJ.K.)
X-ray small-angle
545
scattering of porous carbon materials
R. Perret and W. Ruland (Union Carbide European Research Associates, S.A., Rue Gatti de Gamond 95,118O Bruxelles, Belgium). Luzzati’s method for the evaluation of multiple X-ray small angle scattering has been revised and completed. Under the usual experimental conditions multiple scattering occurs practically in all cases in which the produce of the average pore size (in A) and the volume fraction of pores is larger than 10. The information obtainable from multiple scattering can, under appropriate experimental conditions, be as complete as that from single scattering. Absolute measurements are easier to carry out with multiple scattering than with single scattering. 117. Preferred lattice orientation and three-dimensional crystallinity in some carbon fibers S. Ergun (U.S. Bureau of Mines, Pittsburgh, Pennsylvania). It has been found that some carbon fibers derived from acrylic yarns show an extensive degree of orientation of the graphitic layer lattice such that the two-dimensional (10) lines tend to be parallel to the fiber axis. Such fibers also give rise to strong three-dimensional (112) reflections. From a study of five fibers it is concluded that carbon fibers are indeed polymers. 118. Interactions
between Halogen
impurities
and stacking faults in graphite
M. Saito (School of Medicine, Nihon University, Tokyo, Japan) and T. Tsuzuku (College of Science and Engineering, Nihon iiniversity, Tokyo, Japan). By means of the transparent electron microscopy, the temperature dependence of the stacking fault width in pure and halogen-doped graphites has been investigated in the range 90-300°K. It has been found that the dopants lower the stacking fault energy itself as well as the temperature dependence. Some quantitative discussions are given on the bases of theoretical models for chemical and elastic interactions. 119. Paracrystalline
distortions
in carbon blacks
L. L. Ban and W. M. Hess (Cities Service Company, Petrochemicals Research, Drawer 4, Cranbq, brew Jersey). Short range graphitic order of carbon blacks is analyzed by using optical Fourier analysis of high resolution phase contrast electron microscope images. Interlayer distortions are measured and used to follow changes occurring with graphitization. From the knowledge of interlayer distortions the density of these carbons is predicted. 120. Microstructure of carbons: a high resolution electron microscopy study L. L. Ban and W. M. Hess (Cities Service Company, Petrochemicals Research, Drawer 4, Cransbury, New Jersey). Representative samples of different carbons: coals, chars and vacuum evaporated carbon films are analyzed using high resolution phase-contrast electron microscop!,. Changes in microstructure with low and high temperature treatments, i.e. beloll: and above IOOOY~., are studied. 121. The effect of thermal expansion
anisotropy
on the strength of carbon fibers
and R. J. Diefendorf (Rensselaer Polytechnic Institute, Materials Division, Troy, ,$‘ew York). Increasing heattreatment temperature of fibers was shown to increase the degree of- radial and axial ordering of the basal planes, that is, the three dimensional structure of the fibers. A variation in the fracture mechanics of the fiber was shown to result and this was related to the changes that occur in both strength and modulus, of these fibers, with heattreatment temperature. C. W. LeMaistre
122. The defect theory of carbon structure S. Ergun (U.S. Bureau of Mines, Pittsburgh, Pennsylvania). In most carbons the existence of small crystallites having sizes indicated by the line widths of their X-ray diffraction profile is often not substantiated by small-angle X-ray scattering intensities nor by electron-microscopic observations. It is shown that they are made up of very large but defective layers. By the defect theory the line widths of the (hk0) profiles are a measure of the mean defect-free distance and not of the extent of the layers. Similarly the line-width of the (001) reflections is a measure of the number of fault-free parallel layer sequences and not of the extent of stratification (stacking height). The defect theory is critically tested by examining the small angle and high angle X-ray scattering profiles of several types of carbons. 123. The structure of polymeric carbons G. M. Jenkins and K. Kawamura (University College of Swansea, Swansea, Glamorgan, IJ.K.)