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					                      MAE GRADUATE SEMINAR
      Self-Health Monitored Thermal Barrier Coating (TBC) Designs with
       Increased Reflectivity and Lower Thermal Conductivity for High
                     Temperature Turbine Applications
                 December 13, 2006, 1:00 PM, Room 355 ESB

                                 Jogender Singh**
                          Applied Research Laboratory,
            The Pennsylvania State University, University Park, PA 16802


                                         ABSTRACT

Future thrust in turbine industry is designing and developing next generation thermal
barrier coating (TBC) with lower thermal conductivity, increased reflectivity, and
increased performance through nano-layered structures, microstructural modifications
and rare-earth dopants for health monitoring and life prediction. A novel approach was
investigated to introduce periodic strains in the form of microporosity within the
columnar microstructure of ZrO2-8wt.%Y2O3 (YSZ) by periodically interrupting the
condensing vapor reducing its thermal conductivity and increasing hemispherical
reflectivity. The microstructural modification resulted in improved oxidation cyclic life
(over 100%), 20-30% reduction in the thermal conductivity, 28-56% increase in
hemispherical reflectance, and better strain tolerance as compared to standard YSZ. In
addition, coatings consisting of multiply alternating nano-layers of Al2O3 and YSZ were
applied in a one-step evaporation process that showed significant improvement in
hemispherical reflectivity at 1 m. Changing the individual thickness of the Al2O3 / YSZ
multi-nanolayered structure showed an increase in thermal reflectance over the range of
wavelengths (i.e., temperature ranges) that will allow higher combustion temperatures,
and thus increased efficiency. Lastly, TBC with luminescent properties offers non-
intrusive evaluation techniques in monitoring and predicting TBC life. Incorporating
rare-earth doped luminescent sublayers within the YSZ allows early detection of erosion
and spallation which can lead to premature thermal barrier coating failure. All coating
development effort was performed as one step process in industrial scale EB-PVD facility
at Penn State University.


** Dr. Jogender Singh, Chief Scientist, Materials and Manufacturing Division, Applied Research
Laboratory, Professor of Materials Science and Engineering and Engineering Science and
Mechanic Departments, The Pennsylvania State University with over 170 publications, 7 patents
and numerous awards. Dr. Singh is one of the top 214 highly cited researchers in the field of
materials science in the world as published by the Institute for Scientific Information (ISI). Dr.
Singh is a Fellow of three professional societies including American Society for Metals (ASM)
International, American Association Advancement of Science (AAAS) and Institute of Materials
(FIM), London. He is recipient of 1997R&D100 award.

				
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