Zirconia and alumina have been successfully incorporated into turbines used for propulsion and power generation. They exert a crucial influence on the fuel efficiency. The roles of these oxides within the overall system are described, relative to those for the other constituents, and their most important properties are outlined. The mechanisms that govern their properties are presented and approaches for adjusting them in desirable directions are discussed. Opportunities for new materials with potential for superior performance are assessed.

The influence of oxides on the performance of advanced gas turbines

Embodiments related to managing the process feed conditions for a semiconductor process module are provided. In one example, a gas channel plate for a semiconductor process module is provided. The example gas channel plate includes a heat exchange surface including a plurality of heat exchange structures separated from one another by intervening gaps. The example gas channel plate also includes a heat exchange fluid director plate support surface for supporting a heat exchange fluid director plate above the plurality of heat exchange structures so that at least a portion of the plurality of heat exchange structures are spaced from the heat exchange fluid director plate.

Process feed management for semiconductor substrate processing

The present invention relates to a process and system for depositing a thin film onto a substrate. One aspect of the invention is depositing a thin film metal oxide layer using atomic layer deposition (ALD).

Systems and methods for thin-film deposition of metal oxides using excited nitrogen-oxygen species

A showerhead including a body having an opening, a first plate positioned within the opening and having a plurality of slots, a second plate positioned within the opening and having a plurality of slots, and wherein each of the first plate plurality of slots are concentrically aligned with the second plate plurality of slots.

Semiconductor reaction chamber showerhead

Modern gas turbines rely on ceramic coatings to protect structural components along the hot gas path. These coatings are susceptible to accelerated degradation caused by silicate deposits formed when ingested environmental debris (dust, sand, ash) adheres to the coatings. This article reviews the current understanding of the deposit-induced failure mechanisms for zirconia-based thermal barrier coatings and silicate environmental barrier coatings. Details of the debris melting and crystallization behavior, the nature of the chemical reactions occurring between the deposits and coatings, and the implications for the thermocyclic durability of the coatings are described. Given the challenges posed in understanding how prospective coating materials and architectures will respond to a broad range of deposit compositions, it is proposed to develop an integrated framework linking thermochemical and thermomechanical models to predict coating durability. Initial progress toward developing this framework, and the r...

Silicate Deposit Degradation of Engineered Coatings in Gas Turbines: Progress Toward Models and Materials Solutions

One failure mechanism of thermal barrier coatings composed of yttria-stabilized zirconia (YSZ) has been proposed to be caused, in part, by the transformation of the tetragonal phase of YSZ into its monoclinic phase. Normally, studies of phase evolution are performed by X-ray diffraction (XRD) and by evaluating the intensities of a few diffraction peaks for each phase. However, this method misses some important information that can be obtained with the Rietveld method. Using Rietveld's refinement of XRD patterns, we observed, upon annealing of YSZ coatings, an increase of cubic phase content, a reduction in as-deposited tetragonal phase content, and the appearance of a new tetragonal phase having a lower yttria content that coexists with the as-deposited tetragonal phase of YSZ.

http://premierdentallab.net/wp-content/uploads/2013/05/Gregoire-articles-rietveld1.pdf

Phase Evolution in Yttria-Stabilized Zirconia Thermal Barrier Coatings Studied by Rietveld Refinement of X-Ray Powder Diffraction Patterns

The invention pertains to components (1) with a thermal barrier coating (2-6) on the surface thereof, wherein the thermal barrier coating comprises at least one layer (3) comprising chemically stabilised zirconia, and wherein at least indirectly adjacent to the layer (3) comprising chemically stabilised zirconia and on its surface facing side there is provided a protective layer (4) and/or a infiltration zone (5) which is not reacting with environmental contaminant compositions that contain oxides of calcium and which is not reacting with the material of the layer (3) comprising chemically stabilised zirconia. It furthermore relates to methods for making such components as well as to uses of specific systems for coating thermal barrier coatings for the prevention of CMAS.

Multilayer thermal barrier coating

Yttria stabilized zirconia (YSZ) thermal barrier coatings (TBC) can be destabilized by combustions products, formed due to either dirty fuel or dust ingested through the air intake. The origin of this destabilization is high-temperature interaction of YSZ with molten calcium-magnesium-alumino-silicate (CMAS) deposits. The destabilization of the YSZ changes the behavior of the TBC, finally leading to failure. As a part of this investigation, X-ray powder diffraction, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) studies of ex-service combustor tiles subjected to CMAS attack have been performed. Rietveld refinement of powder diffraction patterns is allowed for the quantitative analysis of phase transformations, chemical composition change of YSZ and reconstruction of the scheme of element migration during the interaction of YSZ with the CMAS deposit. The composition of the deposit that infiltrated the open pores of the YSZ was found to be different from the average deposit composition. Based on the results, some solutions to protect YSZ against CMAS attack are discussed.

High-temperature interaction of yttria stabilized zirconia coatings with CaO–MgO–Al2O3–SiO2 (CMAS) deposits

A reliable lifetime prediction rule for bondcoat/thermal barrier coating (BC/TBC) coated parts in gas turbine operation is necessary to determine remnant service life. The specimens investigated were coated with MCrAlY plus yttria partially stabilized zirconia applied by vacuum plasma spraying and atmospheric plasma spraying processes, respectively. The performances of these laboratory specimens were statistically assessed, combining long term oxidation testing with thermal cycling, thus superimposing thermomechanical loading on the laboratory specimens to more accurately represent engine conditions. A design of experiment (DOE) approach was used for manufacturing optimization of the BC/TBC system . The life of the coating system is influenced by several manufacturing parameters such as BC thickness, BC roughness, TBC thickness, TBC porosity, and TBC stiffness. Specimens with a suitable variation in these parameters were produced to ensure a balanced test matrix of fractional factorial DOE. Based on results derived from laboratory testing the specifically tailored parts, first and second order effects of manufacturing parameters on lifetime were quantified. The findings revealed that the second order effects (the interaction of manufacturing parameters) were more important on the lifetime of the BC/TBC system than the corresponding first order effect (single parameter). For instance, the variation in BC thickness or BC roughness led to a scatter of lifetimes of 10% and 60%, respectively whereas their interaction resulted in a scatter of lifetime of 150% for the same range of coating parameters. Further examples of such pairings are also demonstrated. Finally, a lifetime prediction for three quality classes (high, medium, and low qualities) has been demonstrated. The difference in achievable lifetime highlights the importance of manufacturing parameters in determining the life of the BC/TBC system.

Sharath Bachegowda

Papers

Phase Evolution in Yttria-Stabilized Zirconia Thermal Barrier Coatings Studied by Rietveld Refinement of X-Ray Powder Diffraction Patterns

Multilayer thermal barrier coating

High-temperature interaction of yttria stabilized zirconia coatings with CaO–MgO–Al2O3–SiO2 (CMAS) deposits

Manufacturing Optimization for Bondcoat/Thermal Barrier Coating Systems

Monitoring the Phase Evolution of Yttria Stabilized Zirconia in Thermal Barrier Coatings Using the Rietveld Method