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Search Publications by: Andrew J Allen (Fed)

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Displaying 101 - 125 of 129

Microstructure-Property Correlations in Industrial Thermal Barrier Coatings

July 1, 2004
Author(s)
A Kulkarni, A N. Goland, H Herman, Andrew J. Allen, J Ilavsky, Gabrielle G. Long, C A. Johnson, J A. Ruud
This paper describes the results from multidisciplinary characterization/scattering techniques employed for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for

Studies of the Microstructure and Properties of Dense Ceramic Coatings Produced by High-Velocity Oxgen-Fuel Combustion Spraying

March 1, 2004
Author(s)
A Kulkarni, J Gutleber, S Sampath, A N. Goland, W B. Lindquist, H Herman, Andrew J. Allen, B A. Dowdy
High-velocity oxygen-fuel (HVOF) spraying stands out among the various processes to improve metal and ceramic coating density and surface characteristics. This paper explores microstructure development, coating characterization and properties of HVOF

Comprehensive Microstructural Characterization and Predictive Property Modeling of Plasma-Sprayed Zirconia Coatings

May 1, 2003
Author(s)
A Kulkarni, Z G. Wang, T Nakamura, S Sampath, A N. Goland, H Herman, Andrew J. Allen, J Ilavsky, Gabrielle G. Long, J Frahm, R W. Steinbrech
Quantitative microstructure characterization to better understand processing-microstructure-property correlations is of considerable interest in plasma sprayed coating research. This paper quantifies, by means of small-angle neutron scattering (SANS) data

Small-Angle Neutron Scattering Study of the Role of Feedstock Particle Size on the Microstructural Behavior of Plasma-Sprayed Yttria-Stabilized Zirconia Deposits

March 1, 2003
Author(s)
H Boukari, Andrew J. Allen, Gabrielle G. Long, J Ilavsky, Jay S. Wallace, C C. Berndt, H Herman
The microstructures of thick plasma-sprayed yttria-stabilized (8% mass) zirconia deposits have been studied in a series of Porod small-angle neutron scattering (SANS) and multiple small-angle neutron scattering (MSANS) experiments. Three main void

Agglomerate Formation During Drying

February 1, 2003
Author(s)
A Vertanessian, Andrew J. Allen, M J. Mayo
The evolution of agglomerate structure during drying of particles from suspension has been studied for a nanocrystalline Y2O3 (8 mol %)-stabilized ZrO2 powder. Agglomerates in drying and dried suspensions were examined at the smallest size scales (100 nm

Recent Developments in the Characterization of Anisotropic Void Populations in Thermal Barrier Coatings Using Ultra-Small Angle X-ray Scattering

January 1, 2003
Author(s)
Gabrielle G. Long, T A. Dobbins, Andrew J. Allen, J Ilavsky, P Jemain, A Kulkarni, H Herman
Thermal barrier coatings (TBC) have complex void microstructures which control their in service properties. In the research reported here, ultra-small-angle X-ray scattering (USAXS) has been used to characterize anisotropic void populations in TBC s. A new

Multiple Small-Angle Neutron Scattering Studies of Anisoptropic Materials

December 1, 2002
Author(s)
Andrew J. Allen, Norman F. Berk, J Ilavsky, Gabrielle G. Long
Various authors have recognized the power of multiple small-angle neutron scattering (MSANS) analysis in providing information on coarse, concentrated microstructures involving micrometer length-scales larger than are accessible in conventional small-angle

Fracture of a Textured Anisotropic Ceramic

September 1, 2001
Author(s)
M H. Zimmerman, D M. Baskin, K T. Faber, Lin-Sien H. Lum, Andrew J. Allen, D T. Keane
The role of crystallographic texture in determining the fracture behavior of a highly anisotropic ceramic, iron titantate, has been examined. By exploiting the anisotropy in its single crystal magnetic susceptibility, crystallographically textured and

Microstructural Characterization Studies to Relate the Properties of Thermal Spray Coatings to Feedstock and Spray Conditions

September 1, 2001
Author(s)
Andrew J. Allen, Gabrielle G. Long, H Boukari, J Ilavsky, A Kulkarni, S Sampath, H Herman, A N. Goland
This paper reports how the microstructural information, obtainable for thick plasma-sprayed ceramic deposits by small-angle scattering can be used to explore the relationships among the feedstock or spray process conditions, the anisotropic void and crack

The Ultra-Small-Angle X-Ray Scattering Instrument on UNICAT at the APS

October 1, 2000
Author(s)
Gabrielle G. Long, Andrew J. Allen, J Ilavsky, P R. Jemian, P Zchack
A new ultra-small-angle X-ray scattering (USAXS) instrument has been commissioned as part of the UNICAT facility on the 33-ID line at the Advanced Photon Source. The instrument offers continuously-tunable optics for anomalous USAXS, 1000 times the

Anisotropic Small-Angle Neutron Scattering Studies of Ceramics

October 1, 1999
Author(s)
Andrew J. Allen, Lin-Sien H. Lum, K T. Faber, M H. Zimmerman, Jay S. Wallace
This paper discusses how small-angle neutron scattering studies can be applied in two variations to obtain a representative characterization of the large, densely-populated, and anisotropic features that occur in the microstructures of various materials

Microstructural Changes in YSZ Deposits During Annealing

March 1, 1999
Author(s)
Andrew J. Allen, J Ilavsky, Gabrielle G. Long, Jay S. Wallace, C C. Berndt, H Herman
Various methods have been applied to the microstructural characterization of thermally-sprayed depostis. However, coexisting anisotropic distributions of intra-splat cracks and interlamellar pores, and the broad size range of rounded globular pores, have

Multiple Small-Angle Neutron Scattering

September 1, 1998
Author(s)
Gabrielle G. Long, Susan Krueger, Andrew J. Allen
Over the past decade, a multiple small-angle neutron scattering (MSANS) formalism has been developed to enable researchers to derive microstructural parameters from multiply-scattered small-angle neutron data. The MSANS formalism is particularly useful in