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Role of Y_(4)Al_(2)O_(9)in High Temperature Oxidation Resistance of NiCoCrAlY-ZrO_(2)·Y_(2)O_(3)Coatings 被引量:2
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作者 Shuqin YANG Xiaohua LAN Ningkang HUANG 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2007年第4期568-570,共3页
NiCoCrAlY-ZrO2·Y2O3 coatings were deposited on the substrates by using a technology of combining electron,atom and ion beams (three beams). Isothermal oxidation for these samples was performed at 1100℃ for 100... NiCoCrAlY-ZrO2·Y2O3 coatings were deposited on the substrates by using a technology of combining electron,atom and ion beams (three beams). Isothermal oxidation for these samples was performed at 1100℃ for 100-300 h. The results show that a thermally grown oxide (TGO) layer was formed between NiCoCrAlY layer and oxidation. The TGO contains α-Al2O3 and Y4Al2O9 etc. oxides. The intensity ratio of α-Al2O3/Y4Al2O9 was monotonously decreased with increasing oxidation time based on XRD (X-ray diffraction) analysis. The Y4Al2O9 phase plays the most important role in high temperature oxidation resistance at 1100℃. The related mechanism was also discussed. 展开更多
关键词 NiCoCrAlY-ZrO2·Y2O3 coatings XRD al2y4o9
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Theoretical prediction on mechanical and thermal properties of a promising thermal barrier material:Y_(4)Al_(2)O_(9) 被引量:5
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作者 Yanchun ZHOU Huimin XIANG +2 位作者 Xinpo LU Zhihai FENG Zhongping LI 《Journal of Advanced Ceramics》 SCIE CAS CSCD 2015年第2期83-93,共11页
The mechanical and thermal properties of Y_(4)Al_(2)O_(9)were predicted using a combination of first-principles and chemical bond theory(CBT)calculations.Density functional theory(DFT)computations were performed for t... The mechanical and thermal properties of Y_(4)Al_(2)O_(9)were predicted using a combination of first-principles and chemical bond theory(CBT)calculations.Density functional theory(DFT)computations were performed for the structural,mechanical,and thermal properties,and the results were confirmed by chemical bond theory.Based on the calculated equilibrium crystal structure,heterogeneous bonding nature has been revealed,i.e.,Al-O bonds are stronger than Y-O bonds.Low second-order elastic constants c44,c55,and c66 demonstrate the low shear deformation resistance.Low G/B ratio suggests that Y_(4)Al_(2)O_(9)is a damage tolerant ceramic.Y_(4)Al_(2)O_(9)shows anisotropy in elastic behavior based on the discussion of direction dependence of Young’s modulus.The hardness is predicted to be 10.2 GPa from calculated elastic moduli.The thermal expansion coefficient(TEC)calculated by chemical bond theory is 7.51×10^(-6)K^(-1).In addition,the minimum thermal conductivity of Y_(4)Al_(2)O_(9)is estimated to be 1.13 W·m^(-1)·K^(-1),and the thermal conductivity decreases with temperature as 1305.6/T. 展开更多
关键词 Y4Al2O9 chemical bonding elastic constants thermal conductivity thermal expansion coefficient(TEC)
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Preparation,mechanical,and thermal properties of a promising thermal barrier material:Y_(4)Al_(2)O_(9) 被引量:4
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作者 Yanchun ZHOU Xinpo LU +1 位作者 Huimin XIANG Zhihai FENG 《Journal of Advanced Ceramics》 SCIE CAS CSCD 2015年第2期94-102,共9页
In our previous work,anisotropic chemical bonding,low shear deformation resistance,damage tolerance ability,low thermal conductivity,and moderate thermal expansion coefficient of Y_(4)Al_(2)O_(9)(YAM)were predicted.In... In our previous work,anisotropic chemical bonding,low shear deformation resistance,damage tolerance ability,low thermal conductivity,and moderate thermal expansion coefficient of Y_(4)Al_(2)O_(9)(YAM)were predicted.In this work,phase-pure YAM powders were synthesized by solid-state reaction between Y2O3 and Al_(2)O_(3)and bulk YAM ceramics were prepared by hot-pressing method.Lattice parameters and a new set of X-ray powder diffraction data were obtained by Rietveld refinement.The mechanical and thermal properties of dense YAM ceramics were investigated.The measured elastic moduli are close to the theoretical predicted values and the stiffness can be maintained up to 1400℃.The flexural strength and fracture toughness are 252.1±7.3 MPa and 3.36±0.20 MPa·m^(1/2),respectively.Damage tolerance of YAM was also experimentally proved.The measured average linear thermal expansion coefficient(TEC)of YAM is 7.37×10^(-6)K^(-1),which is very close to the theoretical predicted value.Using high-temperature X-ray diffraction(XRD)analysis,volumetric TEC is determined(23.37±1.61)×10^(-6)K^(-1)and the anisotropic TEC areaa=7.34×10^(-6)K^(-1),ab=7.54×10^(-6)K^(-1),andac=7.61×10^(-6)K^(-1). 展开更多
关键词 Y4Al2O9 X-ray diffraction(XRD)pattern mechanical properties thermal expansion damage tolerance
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