(Shaedler, Evans, Levi)

1. Design of Tougher Thermal Barrier Oxides Carols G. Levi, University of CA – Santa Barbara, DMR 0605700 (Shaedler, Evans, Levi) 7Y 15Ti (t’) 7Y 7Ti (t’) 15YSZ (cubic) 7YSZ (t’) Indentation Toughness Measurements on compacts of precursor-derived powders • Potential for tailoring toughness by controlling the tetragonality of the zirconia unit cell through suitable design of the oxide chemistry demonstrated. • Novel compositions also exhibit improved phase stability.

2. Improved Understanding of Phase Transformations in Zirconia Carols G. Levi, University of CA- Santa Barbara, DMR 0605700 • Alternate paths for the partitionless tetragonal to cubic transformation identified. Path selection depends on chemical composition. Displacive Transformation Lightly sintered compacts of precursor derived powders, annealed at 1450°C “Ordering” Transformation

3. Predicting diffusion in B2 NiAl from first principles Carols G. Levi, University of CA- Santa Barbara, DMR 0605700 Qingchuan Xu and A. Van der Ven NiAl has a B2-crystal structure in which Ni and Al atoms occupy sites of interpenetrating cubic lattices. Diffusion in NiAl is mediated by a variety of intrinsic defects, including vacancies and anti-site defects. Atomic diffusion is very sensitive to the concentration of defects, which are difficult to measure. The point defects can cluster, forming for example the triple defect in which a pair of vacancies cluster around a Ni atom on the Al sublattice By combining quantum mechanics (DFT) with statistical mechanics (cluster expansion and Monte Carlo, we have predicted the concentration as a function of alloy content of various important defects and defect complexes Calculated defect concentrations Calculated triple-defect concentrations

4. Combinatorial Synthesis of NiAl Based Bond Coats Carols G. Levi, University of CA- Santa Barbara, DMR 0605700 A library of 45 coated superalloy buttons with Pd and Hf gradients was synthesized using three vapor sources. 0 Excellent control yields desired gradients and centered composition in the NiAl phase field. (Al+Cr+Hf)/(Ni+Pd) ~ 55 (at%) Samples to be shared by team to investigate interdiffusion and furnace cyclic oxidation (Pollock), transient oxide evolution and transformations (Clarke) and hot corrosion (DiDomizio)

5. Carols G. Levi, University of CA- Santa Barbara, DMR 0605700 Industrial Interactions The DYNES team met at the annual TBC workshop at UCSB. Meetings have also been held at GE Global Research for planning and discussion of research activities. Academia/industry teams have been assembled to address the project goals. Samples for phase stability, oxidation and interdiffusion studies have been provided by GE to the team. Professor Pollock is spending part of her sabbatical at GE Global Research and GE Aviation laboratories. A UCSB graduate student, Kendra Grant, spent the summer at GE Aviation working with the airfoil materials group. Robert Stuart, a UCSB Mechanical Engineering undergraduate, working in the mechanical testing laboratory at Cambridge University. Robert investigated the mechanical response of ceramic honeycombs under the mentorship of Prof. Norman Fleck. International Activities A graduate student (Michael Crowell) and an undergraduate student (Robert Stuart) from UCSB spent the summer on internships at Cambridge University. Two CIAM projects were approved in Brazil and Mexico to collaborate with the DYNES program. Levi will co-advise a Mexican student (CINVESTAV) who is researching ferroelastic phenomena in zirconia by nanoindentation. The PI’s met with all international collaborators during the year to explore projects suitable for student visits. The PI’s organized and gave tutorial lectures at an international summer school on Advanced Thermostructural Materials (August 2006), held at UCSB under NSF-IMI sponsorship. Kendra Kendra Grant with her mentor Laura Rowland and their project team at GE Aviation