APS Y2O3 environmental barrier coatings for oxide ceramic matrix composites

Similar thermal expansion, microstructural stability, good adherence, and corrosion resistance are key issues for environmental barrier coatings (EBC) for oxide ceramic matrix composites (CMC) such as Al2O3/Al2O3. Laboratory-scale specimen as well as prototypic engine components were coated with Y2O3 by means of air plasma spraying (APS). Cubic -Y2O3 exhibits favorable properties such as thermal expansion close to that of Al2O3 and phase stability up to melting. The high thermal stability and low diffusivity of Y2O3 provides an exceptional microstructural stability of APS Y2O3 coatings. Although Y2O3 and Al2O3 are not thermodynamically compatible, the interdiffusion and reaction zone consisting of Y-aluminates is growing only slowly under relevant thermal conditions and does not seriously affect coating adherence. Consequently, APS Y2O3-coated Al2O3/Al2O3 CMC exhibited a high durability versus thermal cycling. APS Y2O3 coatings showed a high recession resistance in water vapor-rich, high-velocity combustion atmospheres. Moreover, APS Y2O3-coatings exhibited a high resistance against thermos-chemical attack by inorganic particles commonly referred to as CMAS corrosion. Infiltration of molten CMAS is mitigated by a dense reaction layer as well as by a quasi-impermeable coating microstructure. The outstanding combination of properties was the rationale for selecting APS Y2O3 as EBC material for Al2O3/Al2O3 combustor liners. Two can-type demonstrators with 0.5 and 1 mm thick APS Y2O3 EBC were manufactured and tested under engine conditions. Both EBCs passed high-pressure combustor rig tests without visible damages, emphasizing the fundamental viability of the concept

Current trends in CMC research & development across DLR’s technology programs

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Microstructure modification of EB-pvd gadolinium zirconate thermal barrier coatings and the effect on their resistance against siliceous CMAS melts

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Synthesis of multi component rare-earth silicate systems for T/EBC application: Study of their high temperature interactions with CMAS

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Microstructure modification of EB-pvd gadolinium zirconate thermal barrier coatings and the effect on their resistance against siliceous CMAS melts

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The Fast ATLAS Track Simulation (FATRAS)

Various systematic physics and detector performance studies with the ATLAS detector require very large simulated event samples. Since the full detector simulation is a highly CPU time consuming operation, fast simulation techniques are widely used in such applications. Furthermore, the simulation of background events does, in general, not require the very detailed detector simulation and fast simulation techniques satisfy the needed accuracy. In ATLAS, the fast simulation program ATLFAST has been extensively used for such purposes. It is, however, based on the smearing of the initial particle properties and is not capable of producing hits along the track. Tracking relevant studies that include both hit information and pattern recognition effects can not be performed when using ATLFAST. An alternative simulation program, the new Fast ATLAS Track Simulation (FATRAS) has been recently deployed, capable of producing full track information, including hits on track. Initially developed as a validation tool for the ATLAS offline track reconstruction, it has become a powerful engine for various use cases. In general, the CPU time determining factor of the full simulation is the tracking of the particle through the very complex detector geometry, while the event reconstruction including pattern recognition and track fitting is relatively fast. In FATRAS, the simplified reconstruction geometry is used as a simulation geometry model, which leads to a significant speed up of the simulation process. FATRAS uses furthermore mainly common offline track reconstruction code and the reconstruction event data model. It is fully embedded in the ATLAS C++ based software framework ATHENA

Y2O3-ZrO2 ratio studies for CMAS resistant thermal barrier coatings prepared by EB- PVD

Thermal barrier coatings based on the yttria-zirconia system with compositions over 50 mol. % YO1.5 rest ZrO2 have shown potential as CMAS/Volcanic ash (VA) resistant coatings1–4. However, it is still not clear what Y-Zr ratio is the optimal to promote effective CMAS/VA arrest. A previous study has shown that pure Y2O3 coatings are not as effective as their yttria-zirconia counterpart4 making this topic of high relevance for the development of CMAS/VA resistant coatings. Therefore, this study is based on the determination of the optimal Y-Zr ratio for EB-PVD TBCs produced with compositions ranging from 40-70 mol. % YO1.5. Preliminary results for short term infiltration (up to 7 min.) at 1250°C with natural VA from the Eyjafjallajökull volcano show a tendency of increased infiltration resistance with coatings having a higher yttria composition (70 mol. %) seen from Figure 15. The experiments indicate formation of reaction products when a 50 mol. % YO1.5 coating composition is used and no significant reaction with lower yttria compositions. Thus, it appears that the threshold point to saturate the glass promoting formation of reaction products (apatite and garnet) is for compositions with at least 50 mol. % YO1.5. A systematic study will be presented to determine the optimum yttia content in EB-PVD coatings for effective glass crystallization. Please click Additional Files below to see the full abstract

A Novel Method for the Preparation of Fibrous CeO2–ZrO2–Y2O3 Compacts for Thermochemical Cycles

Zirconium-Yttrium-co-doped ceria (Ce0.85Zr0.13Y0.02O1.99) compacts consisting of fibers with diameters in the range of 8–10 µm have been successfully prepared by direct infiltration of commercial YSZ fibers with a cerium oxide matrix and subsequent sintering. The resulting chemically homogeneous fiber-compacts are sinter-resistant up to 1923 K and retain a high porosity of around 58 vol% and a permeability of 1.6–3.3 × 10−10 m² at a pressure gradient of 100–500 kPa. The fiber-compacts show a high potential for the application in thermochemical redox cycling due its fast redox kinetics. The first evaluation of redox kinetics shows that the relaxation time of oxidation is five times faster than that of dense samples of the same composition. The improved gas exchange due to the high porosity also allows higher reduction rates, which enable higher hydrogen yields in thermochemical water-splitting redox cycles. The presented cost-effective fiber-compact preparation method is considered very promising for manufacturing large-scale functional components for solar-thermal high-temperature reactors