X‐ray topographic examination of large paraffin single crystals

The internal microstructure of large melt‐grown paraffin (n‐eicosane, C20H42) single crystals was examined by the Lang x‐ray diffraction projection topographic technique. Crystal selection was facilitated by use of an electro‐optical system which permitted instantaneous display of Laue transmission x‐ray diffraction patterns on a television monitor. The crystals were oriented and topographic diffraction planes were selected by the use of a standard (001) stereographic projection plotted from computed angles between crystallographic planes. A second electro‐optical system which permitted direct viewing of the topographic images was use for rapid alignment of the Lang camera and ensured uniformly exposed topographs. X‐ray topographs were obtained from crystals in the as‐grown, plastically deformed, and γ‐irradiated states. The results indicate that both plastic deformation and γ irradiation caused marked changes in the microstructure of the crystals, and that x‐ray topography can be successfully exploited to determine such changes in hydrocarbon crystals.