In situ transmission electron microscopy of high-temperature degradation of yttria-stabilized zirconia thermal barrier coatings

2018 ◽  
Vol 150 ◽  
pp. 50-53 ◽  
Author(s):  
Shogo Kikuchi ◽  
Manabu Tezura ◽  
Masao Kimura ◽  
Norio Yamaguchi ◽  
Satoshi Kitaoka ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Transmission Electron

Effect of Coupled Conditions of Thermal Cycle and Dump Environment on Conductivity of 5mol% Yttria Stabilized Zirconia

2013 ◽  
Vol 591 ◽  
pp. 245-248 ◽  
Author(s):  
Jin Feng Xia ◽  
Hong Qiang Nian ◽  
Tao Feng ◽  
Hai Fang Xu ◽  
Dan Yu Jiang
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Thermal Cycle ◽  
Oxygen Sensor ◽  
Yttria Stabilized Zirconia ◽  
Cyclic Change ◽  
Stabilized Zirconia ◽  
Transmission Electron

In some applications such as automotive oxygen sensor, 5mol% Y2O3stabilized zirconia (5YSZ) is generally used because it has both excellent ionic conductivity and mechanical properties. The automotive oxygen sensor would experience a cyclic change from high temperature (engine running) environment to the low temperature damp environment (in the tail pipe when vehicle stops). The conductivity change with coupled conditions of thermal cycle and dump environment in the 5mol%Y2O3ZrO2(5YSZ) system was examined by XRD,Impedance spectroscopy and transmission electron microscopy (SEM) in this paper.

Running-in behaviour of thermal barrier coatings in the combustion chamber of a diesel engine

2019 ◽  
Vol 234 (1) ◽  
pp. 172-182 ◽  
Author(s):  
Anders Thibblin ◽  
Siamak Kianzad ◽  
Stefan Jonsson ◽  
Ulf Olofsson
Keyword(s):  
Heat Flux ◽  
Diesel Engine ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Heavy Duty ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Heavy Duty Diesel

Thermal barrier coatings have the potential to improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A method for in-situ measurement of heat flux from the combustion chamber of a heavy-duty diesel engine has been developed and was used to study the running-in behaviour of different thermal barrier coating materials and types of microstructures. The in-situ measurements show that the initial heat flux was reduced by up to 4.7% for all investigated thermal barrier coatings compared to a steel reference, except for an yttria-stabilized zirconia coating with sealed pores that had an increase of 12.0% in heat flux. Gd2Zr2O7 had the lowest initial value for heat flux. However, running-in shows the lowest values for yttria-stabilized zirconia after 2–3 h. Potential spallation problems were observed for Gd2Zr2O7 and La2Zr2O7.

Degradation of Yttria Stabilized Zirconia Thermal Barrier Coatings by Molten CMAS (CaO-MgO-Al2O3-SiO2) Deposits

2008 ◽  
Vol 595-598 ◽  
pp. 207-212 ◽  
Author(s):  
Prabhakar Mohan ◽  
Biao Yuan ◽  
Travis Patterson ◽  
Vimal Desai ◽  
Yong Ho Sohn
Keyword(s):  
Electron Microscopy ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Microstructural Development ◽  
Thermal Barrier ◽  
Isothermal Heat Treatment ◽  
Stabilized Zirconia ◽  
Free Standing ◽  
Barrier Coatings ◽  
Ysz Coating

In advanced gas turbine engines that operate in a dust-laden environment causing ingestion of siliceous debris into engines, thermal barrier coatings (TBCs) are highly susceptible to degradation by molten CMAS (calcium-magnesium alumino silicate) deposits. In this study, the degradation mechanisms other than the commonly reported thermomechanical damage are investigated with an emphasis on the thermochemical aspects of molten CMAS induced degradation of TBCs. Free-standing yttria stabilized zirconia (8YSZ) TBC specimens in contact with a model CMAS composition were subjected to isothermal heat treatment in air at temperatures ranging from 1200°C to 1350°C. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Starting at 1250°C, the molten CMAS readily infiltrated and dissolved the YSZ coating followed by reprecipitation of zirconia with a different morphology and composition that depends on the local melt chemistry. Significant amount of Y2O3 depleted monoclinic ZrO2 phase evolved from CMAS melt that dissolved ť-ZrO2 was evident. Thus the mechanism of dissolution and reprecipitation due to molten CMAS damage resulted in destabilization of the YSZ with disruptive phase transformation (t’ f + m).

High-temperature in situ Cross-sectional Transmission Electron Microscopy Investigation of Crystallization Process of Yttrium-stabilized Zirconia/Si and Yttrium-stabilized Zirconia/SiOx/Si Thin Films

2005 ◽  
Vol 20 (7) ◽  
pp. 1878-1887 ◽  
Author(s):  
Takanori Kiguchi ◽  
Naoki Wakiya ◽  
Kazuo Shinozaki ◽  
Nobuyasu Mizutani
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Crystallization Process ◽  
Stabilized Zirconia ◽  
Cross Sectional ◽  
Plan View ◽  
Transmission Electron ◽  
Tem Method

The crystallization process of yttria-stabilized zirconia (YSZ) gate dielectrics deposited on p-Si (001) and SiOx/p-Si(001) substrates and the growth process of SiOx has been investigated directly using high-temperature in situ cross-sectional view transmission electron microscopy (TEM) method and high-temperature plan-view in-situ TEM method. The YSZ layer is crystallized by the nucleation and growth mechanism at temperatures greater than 573 K. Nucleation originates from the film surface. Nucleation occurs randomly in the YSZ layer. Subsequently, the crystallized YSZ area strains the Si surface. Finally, it grows in the in-plane direction with the strain, whereas, if a SiOx layer of 1.4 nm exists, it absorbs the crystallization strain. Thereby, an ultrathin SiOx layer can relax the strain generated in the Si substrate in thin film crystallization process.

Application of in situ Transmission Electron Microscopyfor Tribological Investigations of Magnetron Sputter Assisted Pulsed Laser Deposition of Yttria-stabilized Zirconia-gold Composite Coatings

2005 ◽  
Vol 20 (7) ◽  
pp. 1860-1868 ◽  
Author(s):  
J.J. Hu ◽  
A.A. Voevodin ◽  
J.S. Zabinski
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Composite Coatings ◽  
Pulsed Laser ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Range

Yttria-stabilized zirconia (YSZ)-Au composite coatings have great potential as solid film lubricants for aerospace applications over a wide range of environmental conditions. They were grown on steel disks or silicon wafers by pulsed laser ablation of YSZ and simultaneous magnetron sputtering of a Au target. Such a combination of ceramics with soft metals improved the toughness of the composite coating and increased its ability to lubricate at high temperature. Information on the time-dependent response of these microstructures to changes in temperature is essential to tribological investigations of high temperature performance. In situ transmission electron microscopy was used to directly measure the dynamic change of YSZ-Au coating structure at elevated temperatures. High-resolution electron microscopy and electron diffraction showed that amorphous YSZ-5 at.% Au coatings proceeded to crystallize under the irradiation of electron beams. Time varying x-ray energy dispersive spectra measured a loss of oxygen in the sample during about 10 min of irradiation with subsequent slight oxygen recovery. This behavior was related to the activation of oxygen diffusion under electron irradiation. X-ray diffraction patterns from vacuum annealed samples verified crystallization of the coatings at 500 °C. Real-time growth of Au nanograins in the sample was observed as the temperature was increased to 500 °C in a TEM specimen holder that could be heated. The grain growth process was recorded using a charge-coupled device camera installed on the transmission electron microscope. The crystallization and growth of zirconia and Au nanograins resulted in low friction during tribological tests. The nucleation of Au islands on heated ball-on-flat specimens was responsible for lowering friction.

YTTRIA-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS — A REVIEW

2006 ◽  
Vol 13 (05) ◽  
pp. 535-544 ◽  
Author(s):  
L. B. CHEN
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Coefficient Of Thermal Expansion ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Recent Developments ◽  
Structural Parts ◽  
Power Generation Systems

Thermal barrier coatings (TBCs), which protect metallic components from high-temperature environments, have been widely applied to the fields of high-temperature and corrosion-resistant structural parts such as gas turbine engines, diesel engines, and power generation systems. Yttria-stabilized zirconia (YSZ) is one of the most widely used materials for TBCs owing to its excellent shock resistance, low-thermal conductivity, and relatively high coefficient of thermal expansion. In this paper the properties of YSZ and the recent developments of YSZ-TBCs are reviewed. The failure mechanism of YSZ-TBCs and corresponding methods for lengthening the lifetime of YSZ-TBCs are discussed. The advantages of graded thermal barrier coatings and the problems in processing are elucidated.

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