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Optical Diagnostics for Thermal Barrier CoatingsThe translucent nature of ceramic oxide thermal barrier coatings (TBCs) provides an opportunity to employ optical probes to monitor temperature gradients and buried damage propagation within the coating. An important advantage of noncontact optical diagnostics is that they are amendable to health monitoring of TBCs in service. In this paper, two optical diagnostic approaches, operating in different wavelength regimes, are discussed. The first approach is the use of mid-infrared reflectance (MIR) to monitor the progression of TBC delamination produced by thermal cycling. This approach takes advantage of the maximum transparency of the TBCs at mid-infrared wavelengths, in particular, between 3 and 5 microns. Recent progress in extending the MIR method to a more practical visual inspection tool will be presented. A second approach, using visible wavelengths, is the embedding of thermographic phosphors within the TBC to add sensing functions to the coating that can provide depth-selective information about temperature gradients and TBC integrity. Emphasis will be given to the use of fluorescence decay time measurements to provide temperature readings from a thermographic phosphor layer residing beneath the TBC.
Document ID
Document Type
Preprint (Draft being sent to journal)
Eldridge, J. I.
(NASA Glenn Research Center Cleveland, OH, United States)
Spuckler, C. M.
(NASA Glenn Research Center Cleveland, OH, United States)
Bencic, T. J.
(NASA Glenn Research Center Cleveland, OH, United States)
Martin, R. E.
(Cleveland State Univ. Cleveland, OH, United States)
Date Acquired
September 7, 2013
Publication Date
January 16, 2004
Subject Category
Nonmetallic Materials
Meeting Information
Conference on Composites, Materials and Structures(Cocoa Beach, FL)
Funding Number(s)
OTHER: 22-090-20-C1
Distribution Limits
Public Use Permitted.
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