MSANS STUDIES OF AN ANISOTROPICALLY-SCATTERING MICROSTRUCTURE. A.J. Allen¹, J. Ilavsky^1,2 and G.G. Long¹, ¹Materials Science and Engineering Lab., NIST, Gaithersburg, MD, ²Plasma Spray Lab., State University of New York, Stony Brook, NY.

Multiple-SANS (MSANS) methods, recently modified to study anisotropically-scattering microstructures, have been applied to the quantitative characterization of the coarse and concentrated pore/splat morphologies within ceramic plasma-sprayed deposits. The new MSANS formulation has been used to interpret the multiple scattering arising from the different coexisting anisotropic orientation distributions of coarse interlamellar voids and intralamellar cracks. For oblate- or prolate-shaped scatterers, this formulation considers both diffraction and refraction effects in predicting the MSANS broadening as a function of neutron wavelength. In ceramic materials, pores or voids with mean diameters of up to about 4 micrometers have proved measurable. For plasma-sprayed deposits, the MSANS studies have been combined with porosimetry and anisotropic Porod scattering measurements in a quantitative characterization of the undisturbed statistically-representative microstructures, as a function of the processing parameters or service degradation conditions. Similar MSANS methods are now being employed in the study of anisotropic crack propagation during the controlled-texture sintering of ceramic materials.