Sintering Behavior of Plasma-Sprayed Sm2Zr2O7 Coating

2010 ◽  
Author(s):  
Jianhua Yu ◽  
Huayu Zhao ◽  
Shunyan Tao ◽  
Xiaming Zhou ◽  
Chuanxian Ding
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coating ◽  
Expansion Coefficient ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Plasma Sprayed

Plasma-sprayed thermal barrier coating (TBC) systems are widely used in gas turbine blades to increase turbine entry temperature (TET) and better efficiency. Yttria stabilized zirconia (YSZ) has been the conventional thermal barrier coating material because of its low thermal conductivity, relative high thermal expansion coefficient and good corrosion resistance. However the YSZ coatings can hardly fulfill the harsh requirements in future for higher reliability and the lower thermal conductivity at higher temperatures. Among the interesting TBC candidates, materials with pyrochlore structure show promising thermo-physical properties for use at temperatures exceeding 1200 °C. Sm2Zr2O7 bulk material does not only have high temperature stability, sintering resistance but also lower thermal conductivity and higher thermal expansion coefficient. The sintering characteristics of ceramic thermal barrier coatings under high temperature conditions are complex phenomena. In this paper, samarium zirconate (Sm2Zr2O7, SZ) powder and coatings were prepared by solid state reaction and atmosphere plasma spraying process, respectively. The microstructure development of coatings derived from sintering after heat-treated at 1200–1500 °C for 50 h have been investigated. The microstructure was examined by scanning electron microscopy (SEM) and the grain growth was analyzed in this paper as well.

scholarly journals Optimization of the thermophysical properties of the thermal barrier coating materials based on GA-SVR machine learning method: illustrated with ZrO2 doped DyTaO4 system

2021 ◽  
Author(s):  
Zhu Wen Jie ◽  
Mengdi Gan ◽  
Bo Ye ◽  
Xin Xiong ◽  
Feng Jing ◽  
...  
Keyword(s):  
Machine Learning ◽  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coating ◽  
Expansion Coefficient ◽  
Thermophysical Properties ◽  
Thermal Barrier ◽  
Coating Materials ◽  
Barrier Coating

Abstract It is a critical issue to reduce the thermal conductivity and increase the thermal expansion coefficient of ceramic thermal barrier coating (TBC) materials in the course of their utilization. To synthesize samples with different composition and measure their thermal conductivity by the traditional experimental approaches is time-consuming and expensive. Most classic and empirical models work inefficiently and inaccurately when researchers attempt to predict the thermophysical properties of TBC materials. In this research project, we tentatively exploit a Genetic Algorithm-Support Vector Regression (GA-SVR) machine learning model to study the thermophysical properties, illustrated with the potential TBC materials ZrO2 doped DyTaO4, which has resulted in the lowest thermal conductivity in rare earth tantalates RETaO4 system. Meanwhile, we employ statistical parameters of correlation coefficient (R2) and mean square error (MSE) to evaluate the accuracy and reliability of the model. The results reveal that this model has brought about high correlation coefficients of thermal conductivity and thermal expansion coefficient (99.8% and 99.9%, respectively), while the MSE values are 0.00052 and 0.00019, respectively. The doping concentration of ZrO2 was optimized to reach as low as 0.085-0.095, so as to reduce their thermal conductivity further and increase their thermal expansion. This model provides an accurate and reliable option for researchers to design ceramic thermal barrier coating materials.

scholarly journals Effect of Gd2O3 Addition on the Microstructure and Properties of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) Ceramics

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7470
Author(s):  
Pei-Hu Gao ◽  
Sheng-Cong Zeng ◽  
Can Jin ◽  
Bo Zhang ◽  
Bai-Yang Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Fracture Toughness ◽  
Thermal Expansion ◽  
Elastic Modulus ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Thermal Barrier ◽  
High Temperature Stability ◽  
Coating Materials

Gd and Yb elements have high chemical stability, which can stabilize the solid solution in ZrO2. Gd2O3 and Yb2O3 have high melting points, and good oxidation resistance in extreme environments, stable chemical properties. Therefore, Gd2O3 and Yb2O3 were added to ZrO2 to stabilize oxides, improve the high temperature stability, and effectively decrease the thermal conductivity at high temperature. In this work, 5 wt% Yb2O3 and 5 wt%, 10 wt%, 15 wt% Gd2O3 were doped into 8 wt% Y2O3 stabilized ZrO2 (8YSZ) powders as thermal barrier coating materials, and sintered at 1650 °C for 6 h, 12 h, 24 h. The effects of Gd2O3 addition on the microstructure, density, thermal conductivity, hardness, and fracture toughness of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) bulk composite ceramics were investigated. It was found that the densification of the 8YSZ bulk and GYYZO bulk with 15 wt% Gd2O3 reached 96.89% and 96.22% sintered at 1650 °C for 24 h. With the increase of Gd2O3 addition, the hardness, elastic modulus and fracture toughness of the GYYZO bulk increased and the thermal conductivity and thermal expansion coefficient of the GYYZO bulk decreased. GYYZO bulk with 15 wt% Gd2O3 sintered at 1650 °C for 24h had the highest hardness, elastic modulus and fracture toughness of 15.61 GPa, 306.88 GPa, 7.822 MPa·m0.5, and the lowest thermal conductivity and thermal expansion coefficient of 1.04 W/(m·k) and 7.89 × 10−6/°C at 1100 °C, respectively. The addition of Gd2O3 into YSZ could not only effectively reduce the thermal conductivity but also improve the mechanical properties, which would improve the thermal barrier coatings’ performances further.

Design, Preparation and Thermal Properties of (La0.4Sm0.5Yb0.1)2Zr2O7 Ceramic for Thermal Barrier Coatings

2012 ◽  
Vol 512-515 ◽  
pp. 469-473 ◽  
Author(s):  
L. Liu ◽  
Z. Ma ◽  
F.C. Wang ◽  
Q. Xu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Rare Earth ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coatings ◽  
Expansion Coefficient ◽  
Phonon Transport ◽  
Thermal Barrier ◽  
Barrier Coatings

According to the theory of phonon transport and thermal expansion, a new complex rare-earth zirconate ceramic (La0.4Sm0.5Yb0.1)2Zr2O7, with low thermal conductivity and high thermal expansion coefficient, has been designed by doping proper ions at A sites. The complex rare-earth zirconate (La0.4Sm0.5Yb0.1)2Zr2O7 powder for thermal barrier coatings (TBCs) was synthesized by coprecipitation-calcination method. The phase, microstructure and thermal properties of the new material were investigated. The results revealed that single phase (La0.4Sm0.5Yb0.1)2Zr2O7 with pyrochlore structure was synthesized. The thermal conductivity and the thermal expansion coefficient of the designed complex rare-earth zirconate ceramic is about 1.3W/m•K and 10.5×10-6/K, respectively. These results imply that (La0.4Sm0.5Yb0.1)2Zr2O7 can be explored as the candidate material for the ceramic layer in TBCs system.

A Promising LaSmZr2O7 Ceramic with Pyrochlore Structure for Thermal Barrier Coatings

2008 ◽  
Vol 368-372 ◽  
pp. 1328-1330
Author(s):  
Qiang Xu ◽  
Wei Pan ◽  
Chun Lei Wan ◽  
Long Hao Qi ◽  
He Zhuo Miao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coatings ◽  
Expansion Coefficient ◽  
Pyrochlore Structure ◽  
Solid State Reaction Method ◽  
Rare Earth Ions ◽  
Thermal Barrier ◽  
Barrier Coatings

Based on La2Zr2O7 ceramic for thermal barrier coatings, LaSmZr2O7 ceramic doped with samarium ion was successfully prepared using solid state reaction method. The pellets were sintered at 1600°C for 10 hours in air. The phase structure, thermal conductivity and thermal expansion coefficient of LaSmZr2O7 ceramic and La2Zr2O7 ceramic were measured by XRD, laser-flash device, high-temperature dilatometry, respectively. The results show that the crystal structure of LaSmZr2O7 ceramic is not affected by the doped samarium ion in the zirconium lattice. The thermophysical results show that the thermal conductivity of the LaSmZr2O7 ceramic is lower than that of La2Zr2O7 ceramic, while the thermal expansion coefficient is higher than that of La2Zr2O7 ceramic. These results indicate that LaSmZr2O7 ceramic or Ln2Zr2O7 ceramics doped with other rare earth ions could be candidate materials for future thermal barrier coatings.

scholarly journals Change in Microstructure of Plasma Sprayed Thermal Barrier Coating by High Temperature Isothermal Heat Exposure

2005 ◽  
Vol 69 (1) ◽  
pp. 67-72 ◽  
Author(s):  
Akio Shinmi ◽  
Makoto Hasegawa ◽  
Yutaka Kagawa ◽  
Masashi Kawamura ◽  
Takeshi Suemitsu
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coating ◽  
Heat Exposure ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Plasma Sprayed
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