Small-angle x-ray scattering from oriented ellipsoidal voids in pyrolytic graphite

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Abstract
Small‐angle x‐ray scattering from oriented voids in pyrolytic graphite has been studied. The scattering is found equivalent to that from a dilute dispersion of ellipsoids of revolution called ’’Guinier spheres’’ of radius of gyration R=[(3/5) H]1/2=[(3/5)(a2 sin2γ+b2 cos2γ)]1/2, where γ is the angle between the common axis of revolution (semiminor axis b) and the scattering vector h. Analysis of the data using Hamzeh and Bragg’s theory provides values of a, b, and a/b from the ’’Guinier’’ and the ’’Porod’’ regions, independently, with good agreement. The theoretically predicted angular dependence of H using ’’best‐fit’’ values of a and b is in good agreement with the experimentally determined value of H, γ varying from 0° to 180°.