RECENT DEVELOPMENTS IN THE CHARACTERIZATION OF ANISOTROPIC VOID POPULATIONS IN THERMAL BARRIER COATINGS USING ULTRA-SMALL ANGLE X-RAY SCATTERING


T.A. Dobbins1, A.J. Allen1, J. Ilavsky1,2, A. Kulkarni3, P.R. Jemian4, H. Herman3, G.G. Long1


 


1.Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8520

2.Dept. of Chemical Engineering, Purdue University, West Lafayette, IN 47907

3.NSF Center for Thermal Spray Research, SUNY Stony Brook, Stony Brook, NY 11794-2275

4.UNICAT Sector 33, Bldg.438D, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439


ABSTRACT

 

 

Thermal barrier coatings (TBC) have complex void microstructures, which control in service properties. In the research presented here, ultra-small-angle x-ray scattering (USAXS) has been used to characterize anisotropic void populations in TBC's. A new analysis method has been developed for characterizing the voids in three dimensions. The anisotropy in the microstructure at a given length scale associated with a value of the scattering vector, |Q| gives rise to changes in scattered intensity as a function of the sample orientation. By measuring the scattered intensity at fixed |Q| as the sample is rotated about the beam, the distribution of the scattering population(s) at this length scale is determined. Using an anisotropic modeling method, the void orientation distribution, void size distribution, shape, and volume fraction information is determined for up to four different void populations. This paper illustrates the use of three-dimensional anisotropic USAXS modeling for the analysis of scattering from voids in several different TBC microstructures.