Session *BB9.1

3:15 PM *BB9.1
MICROSTRUCTURAL CHARACTERIZATION OF PLASMA-SPRAYED DEPOSITS BY MEANS OF SMALL-ANGLE NEUTRON SCATTERING. Gabrielle G. Long, Jan Ilavsky*, Andrew J. Allen, National Institute of Standards and Technology, Materials Science and Engineering Laboratory, Gaithersburg, MD, *current address: Institute of Plasma Physics, Prague, CZECH REPUBLIC.

Despite the fact that the porous microstructure of plasma-sprayed deposits directly determines their physical and mechanical properties, the complexity of the deposit microstructure has long impeded quantitative assessment as a function of powder feed stock and processing parameters. At NIST, small-angle neutron scattering (SANS) techniques and instruments have been developed and used to measure microstructural features from 1 nm to 3 micrometers in size, to follow ceramic microstructural parameters in situ as a function of thermal treatment, and to measure anisotropic as well as isotropic materials. Porod scattering studies have been used to measure, independently, the specific surface areas of interlamellar pores and intralamellar cracks. Multiple SANS (MSANS) measurements have been able to add relative volume fractions and mean sizes of the void systems, and has led to the quantification of a third (globular) population of voids. Studies of plasma-sprayed deposits include investigations of processing-microstructure relationships and of the evolution of microstructure as a function of in-service heat treatment. The results offer the first proof that the quantity and the character of the porosity can be controlled independently by means of processing protocols, and that the in-service thermal environment plays a distinct role in the evolution of the microstructure and properties of product coatings.