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The structural changes in the formation of carbon fibers from polyacrylonitrile precursors
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ABSTRACTS
II. FIBERS AND COMPOSITES 18. Carbon work at the Royal Aircraft Establishment (Charles Pettinos Award Lecture) W. Watt (RqaZ Air~aft ~s~bl~hm~t, bates Depar~e~t, Fu~borough, Hunts, ZJK.) 19. The fine structure of a range of pan-based carbon fibres D. J. Johnson, D. Crawford and C. Oates (Textile Physics Laboratory, Department of Textile Industries, University of Leeds, U.K.). The development of fine structure in PAN-based carbon fibres prepared in the temperature range 300°C to 1000°C will be discussed in terms of X-ray and electron microscope results, including direct lattice resolution. Further evidence on high-modulus carbon fibres treated around 28OO”C, and a three-dimensional model of structure which is probably independent of the precursor material, will be included. 20. The structural changes in the formation of carbon fibers from polyacrylonitrile precursors T. Uchida, I. Shionoya, 1’. Ito and K. Nukada (Pione~ng~esearch and D~elo~ent L~~rut~~, Toray Zlotys, Inc., Son~a~, Otsu, 520 Japan). The thermal oxidation and the carbonization process of PAN precursors have been studied by the thermal gravimetric and evolution gas analysis method and with the infrared and X-ray techniques. By comparing the results of the thermal degradation studies with those of the structural analyses, the mechanisms of the reactions in the oxidation and carbonization processes are proposed. 21. X-ray preferred orientation studies of carbon fibers S. Duliere (Sandiu Laboratories, Division 5522, PO. Box 5800. AZbuquerque, New Mexico). The preferred orientation of an anisotropic carbon fiber or matrix is indicative of the physical properties of the material. The relative moduli and coefficients of thermal expansion of the fiber and matrix determine the composite response to mechanical stress and heating. The relative preferred orientation of the fiber and matrix is related to the relative physical properties. The preferred orientations of several carbon fiber bundles infiltrated with Ctr, at 1100°C to various volume percents of matrix, have been measured. The preferred orientations versus volume percent matrix for a given system can be extrapolated to get the fiber and matrix preferred orientations. The results indicate that the composites can be ranked by this nondestructive X-ray technique. 22. Electron microscopy of carbon fibers A. Fourdeux, R. Perret and W. Ruland (U&n Carbide European Research Associates, S.A., Rue Gatti de Gamond 96, 1180 Bruxelles, Belgium). A detailed electron microscopy study of carbon fibers including high-resolution phase-contrast and high resolution dark-field techniques has been carried out. The results confirm the basic structural model developed earlier and give further details on the lateral packing of microfibrils, the distribution of relative tilt angles between adjacent microfibrils and the average length of carbon ribbons. 23. The influence of preferred orientation on the line width of (hk) interferences W. Ruland and H. Tompa (Union Carbide European Research Associates, S.A., Rue Gatti de Gamond 95, 1180 Bruxelles, Belgium). Using a theoretical treatment already developed earlier, the variation of the constant of proportionality between the half-width of (hk) interferences and the reciprocal of the apparent size parameter as a function of the preferred orientation has been computed for systems of cylindrical symmetry. The relationships obtained are applicable to X-ray studies of pyrolytic carbon as well as of carbon fibers. 24. Surface properties of carbon fibers V. J. Mimeault (Ferro Corporation Technical Center, Clevet’and, Ohio) and D. W. McKee (General Electric Research and D~telo~~t Center, ~ch~ec~dy, New York,). The surface area of treated and untreated carbon fibers has been measured after outgassing the fibers in vacuum at temperatures up to tOOO°C. The surface area after outgassing increases by - 50 per cent for untreated Modmor Type I (high modulus low strength) and by - 300 per cent for treated Type I. In a separate experiment, the composition of the desorption products was monitored with a mass spectrometer. The composition of the evolved gas was mainIy CO, below 500°C and CO above, with hydrogen detected above 700°C. The temperature-pressure profile was dependent upon the type of fiber and subsequent treatment. The thermal behavior and reactivity of the fibers is strongly dependent upon the prior high temperature heat treat-
ABSTRACTS
II. FIBERS AND COMPOSITES 18. Carbon work at the Royal Aircraft Establishment (Charles Pettinos Award Lecture) W. Watt (RqaZ Air~aft ~s~bl~hm~t, bates Depar~e~t, Fu~borough, Hunts, ZJK.) 19. The fine structure of a range of pan-based carbon fibres D. J. Johnson, D. Crawford and C. Oates (Textile Physics Laboratory, Department of Textile Industries, University of Leeds, U.K.). The development of fine structure in PAN-based carbon fibres prepared in the temperature range 300°C to 1000°C will be discussed in terms of X-ray and electron microscope results, including direct lattice resolution. Further evidence on high-modulus carbon fibres treated around 28OO”C, and a three-dimensional model of structure which is probably independent of the precursor material, will be included. 20. The structural changes in the formation of carbon fibers from polyacrylonitrile precursors T. Uchida, I. Shionoya, 1’. Ito and K. Nukada (Pione~ng~esearch and D~elo~ent L~~rut~~, Toray Zlotys, Inc., Son~a~, Otsu, 520 Japan). The thermal oxidation and the carbonization process of PAN precursors have been studied by the thermal gravimetric and evolution gas analysis method and with the infrared and X-ray techniques. By comparing the results of the thermal degradation studies with those of the structural analyses, the mechanisms of the reactions in the oxidation and carbonization processes are proposed. 21. X-ray preferred orientation studies of carbon fibers S. Duliere (Sandiu Laboratories, Division 5522, PO. Box 5800. AZbuquerque, New Mexico). The preferred orientation of an anisotropic carbon fiber or matrix is indicative of the physical properties of the material. The relative moduli and coefficients of thermal expansion of the fiber and matrix determine the composite response to mechanical stress and heating. The relative preferred orientation of the fiber and matrix is related to the relative physical properties. The preferred orientations of several carbon fiber bundles infiltrated with Ctr, at 1100°C to various volume percents of matrix, have been measured. The preferred orientations versus volume percent matrix for a given system can be extrapolated to get the fiber and matrix preferred orientations. The results indicate that the composites can be ranked by this nondestructive X-ray technique. 22. Electron microscopy of carbon fibers A. Fourdeux, R. Perret and W. Ruland (U&n Carbide European Research Associates, S.A., Rue Gatti de Gamond 96, 1180 Bruxelles, Belgium). A detailed electron microscopy study of carbon fibers including high-resolution phase-contrast and high resolution dark-field techniques has been carried out. The results confirm the basic structural model developed earlier and give further details on the lateral packing of microfibrils, the distribution of relative tilt angles between adjacent microfibrils and the average length of carbon ribbons. 23. The influence of preferred orientation on the line width of (hk) interferences W. Ruland and H. Tompa (Union Carbide European Research Associates, S.A., Rue Gatti de Gamond 95, 1180 Bruxelles, Belgium). Using a theoretical treatment already developed earlier, the variation of the constant of proportionality between the half-width of (hk) interferences and the reciprocal of the apparent size parameter as a function of the preferred orientation has been computed for systems of cylindrical symmetry. The relationships obtained are applicable to X-ray studies of pyrolytic carbon as well as of carbon fibers. 24. Surface properties of carbon fibers V. J. Mimeault (Ferro Corporation Technical Center, Clevet’and, Ohio) and D. W. McKee (General Electric Research and D~telo~~t Center, ~ch~ec~dy, New York,). The surface area of treated and untreated carbon fibers has been measured after outgassing the fibers in vacuum at temperatures up to tOOO°C. The surface area after outgassing increases by - 50 per cent for untreated Modmor Type I (high modulus low strength) and by - 300 per cent for treated Type I. In a separate experiment, the composition of the desorption products was monitored with a mass spectrometer. The composition of the evolved gas was mainIy CO, below 500°C and CO above, with hydrogen detected above 700°C. The temperature-pressure profile was dependent upon the type of fiber and subsequent treatment. The thermal behavior and reactivity of the fibers is strongly dependent upon the prior high temperature heat treat-