Processing and design methodologies for advanced and novel thermal barrier coatings for engineering applications

Influence of original powders on the microstructure and properties of thermal barrier coatings deposited by supersonic atmospheric plasma spraying, Part I: Microstructure

Laser treatment of zirconia surface for improved surface hydrophobicity

Microstructural evolution of plasma sprayed submicron-/nano-zirconia-based thermal barrier coatings

Over the past few years, dye-sensitized solar cell (DSC) research has been focused on the material and process cost reduction, and on the electronics integration of the devices. Monolithic design is one of the most promising DSC architectures for mass production, because it allows the elimination of one conductive substrate and offers the possibility of printing layer-by-layer the materials that compose the structure. In this study, the formulation, the realization, and the processing of the spacer and the catalyst layers are proposed, and the relative performance in terms of J-V characteristics, incident photon to current conversion efficiency, and impedance analysis of the device with the optimized material thickness is reported. The optimized profile of the overall structure permits us to obtain masked cells with a conversion efficiency of about 5% with no chemical treatment.

Fabrication of Spacer and Catalytic Layers in Monolithic Dye-Sensitized Solar Cells

A technique used to improve the life cycle and/or the working temperature of the turbine blades uses ceramic coatings over metallic material applied by electron beam-physical vapor deposition (EB-PVD). The most usual material for this application is yttria doped zirconia. Addition of niobia, as a co-dopant in the Y 2 O 3 –ZrO 2 system, can reduce thermal conductivity. The purpose of this work is to evaluate the influence of the addition of niobia on the microstructure and thermal properties of the ceramic coatings. This new formulation will, in the future, be able to become an alternative to the composition currently used by the aerospace field in EB-PVD thermal barrier coatings (TBC). A significant reduction of the thermal conductivity, measured by laser flash technique, in the zirconia ceramic coatings co-doped with yttria and niobia when compared with zirconia–yttria coatings was observed.

Thermal conductivity investigation of zirconia co-doped with yttria and niobia EB-PVD TBCs

The most usual ceramic material for coating turbine blades is yttria doped zirconia. Addition of niobia, as a co-dopant in the Y 2 O 3 -ZrO 2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work was to evaluate the influence of the addition of niobia on the microstructure and thermal properties of the ceramic coatings. SEM on coatings fractured cross-section shows a columnar structure and the results of XRD show only zirconia tetragonal phase in the ceramic coating for the chemical composition range studied. As the difference NbO 2,5 -YO 1,5 mol percent increases, the tetragonality increases. A significant reduction of the thermal conductivity, measured by laser flash technique in the zirconia coating co-doped with yttria and niobia when compared with zirconia-yttria coating was observed.

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Thermal barrier coating by electron beam-physical vapor deposition of zirconia co-doped with yttria and niobia

Turbine blades of airplanes and thermoelectric plants work in adverse conditions, with corrosive environment and high temperature and pressure. One way to improve the life and/or the working temperature of the blades is the use of special coatings over metallic material applied by Electron Beam–Physical Vapor Deposition (EB–PVD). The most usual material for this application is yttria doped zirconia. Addition of niobia, as a co-dopant in the Y 2 O 3 –ZrO 2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work is to show the influence of the addition of niobia on the microstructure of ceramic coatings by using X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM) observations. SEM on fractured cross-section shows a columnar structure and the results of XRD show only zirconia tetragonal phase in the ceramic coating for the chemical composition range studied. As the difference (NbO 2.5 –YO 1.5 ) mol% increases, the ratio c / a (tetragonality) increases. Considering that the t-ZrO 2 solid solutions begins unstable when the relation c / a exceeds 1.020, it is possible to evaluate the maximum niobia content that can be added to the coating without losses in its mechanical properties. SEM on ceramic coatings polished cross-section shows color bands associated with chemical composition changes due to the differences in saturation vapor pressure of the individual components. As the niobia content increases, there is a tendency to reduction of the ceramic coating theoretical density.

EB–PVD TBCs of zirconia co-doped with yttria and niobia, a microstructural investigation

This paper provides an overview of the design and development process of the L75 Liquid Propellant Rocket Engine (LPRE). Being developed at Institute of Aeronautics and Space (IAE), it is the first Brazilian open-cycle liquid rocket engine pressurized by turbopump, designed to deliver 75 kN of thrust in vacuum as a cryogenic upper stage engine using liquid oxygen and ethanol. The Preliminary Design Review (PDR) was accomplished in December 2011 and December 2012 the project received from Agencia Espacial Brasileira (AEB) a financial support, through an agreement with Fundacao de Desenvolvimento da Pesquisa (FUNDEP), to proceeding with the development of models and tests. The main components of the engine, briefly described here, are thrust chamber assembly, gas generator, turbopump assembly, control system and ignition system.

http://www.jatm.com.br/ojs/index.php/jatm/article/download/386/378

Daniel Soares de Almeida

Papers

Thermal conductivity investigation of zirconia co-doped with yttria and niobia EB-PVD TBCs

Thermal barrier coating by electron beam-physical vapor deposition of zirconia co-doped with yttria and niobia

EB–PVD TBCs of zirconia co-doped with yttria and niobia, a microstructural investigation

Development Status of L75: A Brazilian Liquid Propellant Rocket Engine

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