Development of bond coats for extending lifetime of TBCs

This talk will be focused to study the MCrAlY bond coat for thermal barrier coating applications. First of all, residual stresses in the bond coat have been measured with use of X-ray diffraction, in which effect of temperature and thermal cycling will be studied. Secondly, rumpling phenomena of such bond coat after thermal treatments have been examined to identify factors affecting the stress evolution and rumpling of the bond coat. Thirdly, effect of the bond coat microstructure on early oxidation of the bond coat has been investigated to understand how the grain size in the bond coat affected both oxidation products and oxidation kinetics. Finally, the comparison of MCrAlY bond coat vs the NiPtAl bond coat will be made in terms of residual stress evolution, residual stresses, and oxidation kinetics to illustrate the effect of these factors on failure and lifetime of TBCs

The quantum solvation, adiabatic versus nonadiabatic, and Markovian versus non-Markovian nature of electron transfer rate processes

In this work, we revisit the electron transfer rate theory, with particular interests in the distinct quantum solvation effect, and the characterizations of adiabatic/nonadiabatic and Markovian/non-Markovian rate processes. We first present a full account for the quantum solvation effect on the electron transfer in Debye solvents, addressed previously in J. Theore. & Comput. Chem. {\bf 5}, 685 (2006). Distinct reaction mechanisms, including the quantum solvation-induced transitions from barrier-crossing to tunneling, and from barrierless to quantum barrier-crossing rate processes, are shown in the fast modulation or low viscosity regime. This regime is also found in favor of nonadiabatic rate processes. We further propose to use Kubo's motional narrowing line shape function to describe the Markovian character of the reaction. It is found that a non-Markovian rate process is most likely to occur in a symmetric system in the fast modulation regime, where the electron transfer is dominant by tunneling due to the Fermi resonance.Comment: 13 pages, 10 figures, submitted to J. Phys. Chem.

Micromechanical Testing of Thermal Barrier Coatings

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