FINE STRUCTURE OF GRAPHITIZED FIBRES

Carbon fibres graphitized at high temperature have been investigated by the techniques of x-ray diffraction and electron microscopy. The particular sample discussed here contains misoriented turbostratic crystals stacked end to end with widths in the range 20-110 Å; the maximum frequency occurs at 65 Å and this is also a reasonable measure for the length of a crystal. Sharp-edged voids with a mean width of less than 10 Å separate the crystals. A perfectly stacked three-dimensional graphite phase has been discovered and is the predominant phase in recrystallized nickel-graphite fibres. Regions with relatively short turbostratic crystals are also found in the nickel-graphite fibres. The mechanism of recrystallization is discussed in terms of these structures. Extinction bands orthogonal to the crystallite direction are held to define twist boundaries between misoriented crystals. The presence of tilt boundaries is also inferred and the boundaries are assumed to comprise non-basal screw and edge dislocations.