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Development of Low Conductivity and Ultra High Temperature Ceramic Coatings Using A High-Heat-Flux Testing ApproachThe development of low conductivity, robust thermal and environmental barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity and cyclic resistance at very high surface temperatures (up to 17OOOC) under large thermal gradients. In this study, a laser high-heat-flux test approach is established for evaluating advanced low conductivity, ultra-high temperature ceramic thermal and environmental barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) program. The test approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity: the initial conductivity rise under a steady-state high temperature thermal gradient test due to coating sintering, and the later coating conductivity reduction under a subsequent cyclic thermal gradient test due to coating cracking/delamination. The coating system is then evaluated based on the damage accumulations and failure after the combined steady-state and cyclic thermal gradient tests. The lattice and radiation thermal conductivity of advanced ceramic coatings can also be evaluated using laser heat-flux techniques. The coating external radiation resistance is assessed based on the measured specimen temperature response under a laser heated intense radiation flux source. The coating internal radiation contribution is investigated based on the measured apparent coating conductivity increases with the coating surface test temperature under large thermal gradient test conditions. Since an increased radiation contribution is observed at these very high surface test temperatures, by varying the laser heat-flux and coating average test temperature, the complex relation between the lattice and radiation conductivity as a function of surface and interface test temperature is derived.
Document ID
20050210233
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Zhu, Dongming
(NASA Johnson Space Center Houston, TX, United States)
Miller, Robert A.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 23, 2013
Publication Date
January 8, 1990
Subject Category
Composite Materials
Meeting Information
Meeting: Symposiumon Advanced Ceramic Coatings for Structural, Environmental and Functional Applications
Location: Cocoa Beach, FL
Country: United States
Start Date: January 26, 2003
End Date: January 31, 2003
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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