For EB-PVD, different features dominate anisotropy at different Q:

1. Pinhole USAXS Studies of the Anisotropic Microstructures of Thermal Barrier Deposits A.J. Allen1, J. Ilavsky2, A. Kulkarni3, H. Herman3, G.G. Long1 and P.R. Jemian4 1NIST, 2University of Maryland, 3State University of New York, 4University of Illinois Ultrasmall-angle x-ray scattering (USAXS) utilizes Bonse-Hart double-crystal optics to extend the Q-range of SAXS down to ultralow Q values. However, in the standard configuration, data are inherently slit-smeared. With the use of side-bounce reflection stages to remove the slit-smearing effect, an effective pinhole collimation is achieved. Pinhole or side-bounce USAXS (SBUSAXS) is suitable for the characterization of anisotropic microstructures. USAXS STUDIES FOR PORE SIZE DISTRIBUTION Standard USAXS SBUSAXS For EB-PVD, different features dominate anisotropy at different Q: At low Q, anisotropy is dominated by coarse intercolumnar porosity. At intermediate Q, anisotropies of intercolumnar porosity and V-shaped intracolumnar voids are both present. At high Q, anisotropy is dominated by the V-shaped intracolumnar voids, but isotropic scattering also seen due to 34 nm globular voids. CONCLUSIONS: Small beam size and high x-ray brilliance make pinhole USAXS (SBUSAXS) practical for the study of anisotropic materials. By rotating the sample about the incident beam, anisotropic USAXS data can be obtained where both the maximum length-scale probed and the anisotropic resolution surpass those achievable with conventional pinhole SAXS and a 2D detector. Ideal for thin TBCs in situ on the substrate. USAXS imaging can identify the non uniformities in the deposits at different length scales. However, for YSZ higher x-ray energies are needed. At 16.9 keV the energy is just below the Y absorption edge. YSZ thermally-sprayed 0.5-mm-thick deposit. Section 0.3mm thick perpendicular to the substrate. Q=0.00038 Å-1 Standard USAXS: 1.2 x 10-4 < Q < 1 Å-1 Intensity range 8-9 decades Beam size up to 2 mm horizontal x 0.4 mm vertical Slit-smeared data (need for numerical desmearing) – limited to isotropic scatterers Pinhole collimated USAXS: 1.2 x 10-4 < Q < 0.1 Å -1 Intensity range 7-8 decades Beam size up to 0.4 mm x 0.4 mm Pinhole collimated data – studies of anisotropy possible Anisotropy of USAXS data measured by the variation in scattered intensity on rotating the sample around the incident beam at fixed Q. SBUSAXS studies made by taking USAXS Q scans at defined azimuthal rotation angles of the sample around the incident beam. X-ray energy of 17 keV and 0.4 x 0.4 mm beam size ideal for study of 0.3-mm-thick sections of plasma-spray or EB-PVD deposits in situ on the substrate. Acknowledgements The UNICAT facility at the Advanced Photon Source (APS) is supported by the Univ of Illinois at Urbana-Champaign, Materials Research Laboratory (U.S. DOE, the State of Illinois-IBHE-HECA, and the NSF), the Oak Ridge National Laboratory (U.S. DOE under contract with UT-Battelle LLC), the National Institute of Standards and Technology (U.S. Department of Commerce) and UOP LLC. The APS is supported by the U.S. DOE, Basic Energy Sciences, Office of Science under contract No. W-31-109-ENG-38.