The Experts below are selected from a list of 606 Experts worldwide ranked by ideXlab platform
Per Nylen - One of the best experts on this subject based on the ideXlab platform.
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thermal conductivity and thermal cyclic fatigue of multilayered gd2zr2o7 ysz thermal barrier coatings processed by suspension plasma spray
Surface & Coatings Technology, 2015Co-Authors: Satyapal Mahade, Nicholas Curry, Stefan Bjorklund, Nicolaie Markocsan, Per NylenAbstract:Rare earth Zirconates have lower thermal conductivity, better phase stability, improved sintering resistance and CMAS (calcium magnesium alumino silicates) infiltration resistance than yttria stabilized zirconia (YSZ) at temperatures above 1200 °C. However, their lower fracture toughness and lower coefficient of thermal expansion (CTE) compared to YSZ lead to premature coating failure. In order to overcome these drawbacks at higher temperatures, a multilayered coating approach is attempted in this study and compared with the single layer YSZ. Suspension plasma spray of single layer YSZ, single layer gadolinium zirconate (GZ) and double layer GZ/YSZ was carried out. Additionally, a triple layer coating system, with denser gadolinium zirconate on top of the GZ/YSZ system was sprayed to impart an added functionality of sealing the TBC from CMAS infiltration. Microstructural analysis was done using scanning electron microscopy and optical microscopy. Columnar microstructure with vertical cracks was observed. XRD analysis was used to identify phases formed in the as sprayed TBC samples. Porosity measurements were done using water impregnation method. Thermal diffusivity of single and multi-layered coatings was obtained by laser flash analysis and thermal conductivity of the coating systems was determined. It was found that the thermal conductivity of single layer gadolinium zirconate was lower than YSZ and that the thermal conductivity of multilayered systems were between their respective single layers. The single (YSZ), double (GZ/YSZ) and triple (GZ dense/GZ/YSZ) layer TBCs were subjected to thermal cyclic fatigue (TCF) test at 1100 °C and 1200 °C. It was observed that the single layer YSZ had lowest TCF life whereas the triple layer TBC had highest TCF life irrespective of test temperature.
Sossina M. Haile - One of the best experts on this subject based on the ideXlab platform.
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oxygen affinity the missing link enabling prediction of proton conductivities in doped barium Zirconates
Chemistry of Materials, 2020Co-Authors: Yoshihiro Yamazaki, Sossina M. Haile, Akihide Kuwabara, Junji Hyodo, Yuji Okuyama, Craig A J FisherAbstract:Proton-conducting oxides, specifically doped barium Zirconates, have garnered much attention as electrolytes for solid-state electrochemical devices operable at intermediate temperatures (400–600 °...
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Enhanced sintering of yttrium-doped barium zirconate by addition of ZnO
Journal of the American Ceramic Society, 2005Co-Authors: Peter Babilo, Sossina M. HaileAbstract:The influence of transition metal oxides additives, especially zinc oxide, on the densification and electrical properties of doped barium zirconate have been examined. With the use of zinc oxide as a sintering aid, BaZr0.85V0.15O3-8 was readily sintered to above 93% of theoretical density at 1300 degrees C. Scanning electron microscopic investigations showed Zn accumulation in the intergranular regions. Thermogravimetric analysis of the material under flowing CO2 showed ZnO-modified barium zirconate to exhibit excellent chemical stability. The conductivity, as measured by A.C. impedance spectroscopy under H2O saturated nitrogen, was slightly lower than that of unmodified barium zirconate. Electromotive force measurements under fuel cell conditions revealed the total ionic transport number to be similar to 0.9 at 600 degrees C. The combination of electrical and chemical properties and good sinterabifity render ZnO-modified barium zirconate an excellent candidate for reduced temperature solid oxide fuel cell applications.
Satyapal Mahade - One of the best experts on this subject based on the ideXlab platform.
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thermal conductivity and thermal cyclic fatigue of multilayered gd2zr2o7 ysz thermal barrier coatings processed by suspension plasma spray
Surface & Coatings Technology, 2015Co-Authors: Satyapal Mahade, Nicholas Curry, Stefan Bjorklund, Nicolaie Markocsan, Per NylenAbstract:Rare earth Zirconates have lower thermal conductivity, better phase stability, improved sintering resistance and CMAS (calcium magnesium alumino silicates) infiltration resistance than yttria stabilized zirconia (YSZ) at temperatures above 1200 °C. However, their lower fracture toughness and lower coefficient of thermal expansion (CTE) compared to YSZ lead to premature coating failure. In order to overcome these drawbacks at higher temperatures, a multilayered coating approach is attempted in this study and compared with the single layer YSZ. Suspension plasma spray of single layer YSZ, single layer gadolinium zirconate (GZ) and double layer GZ/YSZ was carried out. Additionally, a triple layer coating system, with denser gadolinium zirconate on top of the GZ/YSZ system was sprayed to impart an added functionality of sealing the TBC from CMAS infiltration. Microstructural analysis was done using scanning electron microscopy and optical microscopy. Columnar microstructure with vertical cracks was observed. XRD analysis was used to identify phases formed in the as sprayed TBC samples. Porosity measurements were done using water impregnation method. Thermal diffusivity of single and multi-layered coatings was obtained by laser flash analysis and thermal conductivity of the coating systems was determined. It was found that the thermal conductivity of single layer gadolinium zirconate was lower than YSZ and that the thermal conductivity of multilayered systems were between their respective single layers. The single (YSZ), double (GZ/YSZ) and triple (GZ dense/GZ/YSZ) layer TBCs were subjected to thermal cyclic fatigue (TCF) test at 1100 °C and 1200 °C. It was observed that the single layer YSZ had lowest TCF life whereas the triple layer TBC had highest TCF life irrespective of test temperature.
Lokesh Chandra Pathak - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process
Journal of Materials Engineering and Performance, 2016Co-Authors: S. K. Mishra, N. Jagdeesh, Lokesh Chandra PathakAbstract:The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La_2Zr_2O_7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.
K.m. And Ozgurluk - One of the best experts on this subject based on the ideXlab platform.
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Interface failure behavior of yttria stabilized zirconia (YSZ), La2Zr2O7, Gd2Zr2O7, YSZ/La2Zr2O7 and YSZ/Gd2Zr2O7 thermal barrier coatings (TBCs) in thermal cyclic exposure
'Elsevier BV', 2020Co-Authors: A.c. And Doleker, K.m. And OzgurlukAbstract:Gas turbine engines are exposed to severe oxidation and thermal shock under service conditions. Thermal barrier coatings (TBCs) are used to protect metallic components of gas turbines against such failures. Yttria stabilized zirconia (YSZ) has been the most common top coating material for TBC systems. However, rare earth Zirconates such as La2Zr2O7 and Gd2Zr2O7 stand out as alternatives to YSZ top coating for TBCs. In this study, Inconel 718 substrates were coated with CoNiCrAlY using cold gas dynamic spray (CGDS) technique, which is a promising technology for bond coat spraying. All the ceramic top coats were produced by electron beam physical vapor deposition (EB-PVD) method that provides high strain tolerance under thermal loadings. To predict the lifetime of TBCs, the samples were subjected to furnace cycling tests at 1150 °C. After the tests, the microstructure of thermally grown oxide (TGO) layers, crack formations and chemical compatibility between the coating layers were investigated in detail. Results show that TBCs with double layered rare earth zirconate exhibit longer lifetime as compared to single layered TBCs. © 2019 Elsevier Inc
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Interface failure behavior of yttria stabilized zirconia (YSZ), La2Zr2O7, Gd2Zr2O7, YSZ/La2Zr2O7 and YSZ/Gd2Zr2O7 thermal barrier coatings (TBCs) in thermal cyclic exposure
'Elsevier BV', 2020Co-Authors: A.c. And Doleker, K.m. And OzgurlukAbstract:Gas turbine engines are exposed to severe oxidation and thermal shock under service conditions. Thermal barrier coatings (TBCs) are used to protect metallic components of gas turbines against such failures. Yttria stabilized zirconia (YSZ) has been the most common top coating material for TBC systems. However, rare earth Zirconates such as La2Zr2O7 and Gd2Zr2O7 stand out as alternatives to YSZ top coating for TBCs. In this study, Inconel 718 substrates were coated with CoNiCrAIY using cold gas dynamic spray (CGDS) technique, which is a promising technology for bond coat spraying. All the ceramic top coats were produced by electron beam physical vapor deposition (EB-PVD) method that provides high strain tolerance under thermal loadings. To predict the lifetime of TBCs, the samples were subjected to furnace cycling tests at 1150 degrees C. After the tests, the microstructure of thermally grown oxide (TGO) layers, crack formations and chemical compatibility between the coating layers were investigated in detail. Results show that TBCs with double layered rare earth zirconate exhibit longer lifetime as compared to single layered TBCs
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Isothermal oxidation and thermal cyclic behaviors of YSZ and double-layered YSZ/La2Zr2O7 thermal barrier coatings (TBCs)
'Elsevier BV', 2018Co-Authors: K.m. And Ozgurluk, Yasin And Karaoglanli, Abdullah CahitAbstract:TBCs provide protection of superalloy substrates against harsh environments in gas turbine engines. Typical TBCs consist of two main coating layers called bond and top coat. Recently, Zirconates have become attractive top coat materials as an alternative to yttria stabilized zirconia (YSZ) due to their superior thermal properties. Zirconates are deposited on YSZ layer to decrease the thermal conductivity and to minimize the oxygen penetration. Furthermore, their high melting point as well as phase stability and sintering properties render them promising materials for TBC applications. In this regard, YSZ and YSZ/La2Zr2O7 top coats were deposited using EB-PVD technique on HVOF-CoNiCrAlY bond coated Inconel 718 superalloy, in the present research. TBCs were exposed to isothermal oxidation tests in high temperature furnace at 1000 degrees C with different time periods and also, they were subjected to furnace cycling tests at 1150 degrees C. After oxidation and thermal cycling tests, formation of thermally grown oxide (TGO) layers at the interface and crack surfaces were investigated according to analysis results. The results show that double layered TBC system exhibits better oxidation performance in terms of TGO growth and thermal cyclic lifetime compared to single layer TBC system
