Thermal barrier coatings(TBCs) consisting ofLa_(2)Ce_(2)O_(7)(LCO) and Y_(2)O_(3)-stabilized-ZrO_(2)(YSZ) doubleceramic layer and Dy/Pt co-doped NiAl bond coat were produced by electron beam physical vapor deposition(...Thermal barrier coatings(TBCs) consisting ofLa_(2)Ce_(2)O_(7)(LCO) and Y_(2)O_(3)-stabilized-ZrO_(2)(YSZ) doubleceramic layer and Dy/Pt co-doped NiAl bond coat were produced by electron beam physical vapor deposition(EBPVD). Thermal cyclic performance of the TBCs was evaluated by flame shock testing at 1300 ℃. For comparison, the TBCs with a undoped NiAl bond coat were also studied. The microstructural evolution and failure mechanisms of the above TBCs during thermal cycling were investigated. Spallation failure of the TBCs with the undoped bond coat occurs after around 500 cycles by cracking at the interface between YSZ ceramic layer and thermally grown oxides(TGO) layer. The TBCs with Pt/Dy modified bond coat reveal improved interface bonding even after 1200 thermal cycles, whereas some delamination cracks are presented in the LCO layer. On the other hand,the Pt/Dy modified bond coat effectively suppresses the formation of the needle-like topologically closed packed phases(TCP) in the single crystal superalloy.展开更多
The magnetism and surface behaviour of Pt-Dy/γ-Al_2O_3 catalysts were studied respectively by means of a Faraday magnetic balance and the method of carbon disulfide.The ferromagnetic impurity in the support,γ-Al_2O_...The magnetism and surface behaviour of Pt-Dy/γ-Al_2O_3 catalysts were studied respectively by means of a Faraday magnetic balance and the method of carbon disulfide.The ferromagnetic impurity in the support,γ-Al_2O_3,at low temperature was corrected for the first time.The magnetic susceptibilities of the cat- alysts follow the sequence in different stage of preparation:χ_(uncalcined)<χ_(calcined)<χ_(reduced). The magnetic susceptibilities of the catalysts decrease as they adsorb hydrogen,cyclohexane or benzene. There is a correlation between the aromatization yield of cyclohexane or heptane on these catalysts and the magnetic susceptibility of the catalysts.Since addition of Dy increases the number of adsorption sites and the relevant proportions of weak adsorption sites,the abilities of sulfur-resistance and cyclohexane dehydrogenation are improved.In Pt-Dy/γ-A:_2O_3 catalysts,Dy improves the aromatization activity and stability of the catalyst and plays the role of the electron promoter.展开更多
DyPt2 films were prepared by alternate deposition thin Dy and Pt layers on glass substrates by DC magneto controlled sputtering method. The XRD data indicated that for as-deposited Dy/Pt films, and the periodic layere...DyPt2 films were prepared by alternate deposition thin Dy and Pt layers on glass substrates by DC magneto controlled sputtering method. The XRD data indicated that for as-deposited Dy/Pt films, and the periodic layered structures along thickness direction were evidenced with low angle X-ray scattering. With increasing annealing temperature, the compounds of DyPt, DyPt2 and DyPt3 were formed successively at temperature ranging from 300 to 400 ℃. It was found that the composition reaction DyPt+DyPt3→2DyPt2 took place at 500 ℃. After annealing at 500 ℃ for 1 h, the compounds DyPt and DyPt3 transformed completely into the DyPt2 compound.展开更多
基金financially sponsored by the National Natural Science Foundations of China(Nos.51590894,51425102 and 51231001)。
文摘Thermal barrier coatings(TBCs) consisting ofLa_(2)Ce_(2)O_(7)(LCO) and Y_(2)O_(3)-stabilized-ZrO_(2)(YSZ) doubleceramic layer and Dy/Pt co-doped NiAl bond coat were produced by electron beam physical vapor deposition(EBPVD). Thermal cyclic performance of the TBCs was evaluated by flame shock testing at 1300 ℃. For comparison, the TBCs with a undoped NiAl bond coat were also studied. The microstructural evolution and failure mechanisms of the above TBCs during thermal cycling were investigated. Spallation failure of the TBCs with the undoped bond coat occurs after around 500 cycles by cracking at the interface between YSZ ceramic layer and thermally grown oxides(TGO) layer. The TBCs with Pt/Dy modified bond coat reveal improved interface bonding even after 1200 thermal cycles, whereas some delamination cracks are presented in the LCO layer. On the other hand,the Pt/Dy modified bond coat effectively suppresses the formation of the needle-like topologically closed packed phases(TCP) in the single crystal superalloy.
文摘The magnetism and surface behaviour of Pt-Dy/γ-Al_2O_3 catalysts were studied respectively by means of a Faraday magnetic balance and the method of carbon disulfide.The ferromagnetic impurity in the support,γ-Al_2O_3,at low temperature was corrected for the first time.The magnetic susceptibilities of the cat- alysts follow the sequence in different stage of preparation:χ_(uncalcined)<χ_(calcined)<χ_(reduced). The magnetic susceptibilities of the catalysts decrease as they adsorb hydrogen,cyclohexane or benzene. There is a correlation between the aromatization yield of cyclohexane or heptane on these catalysts and the magnetic susceptibility of the catalysts.Since addition of Dy increases the number of adsorption sites and the relevant proportions of weak adsorption sites,the abilities of sulfur-resistance and cyclohexane dehydrogenation are improved.In Pt-Dy/γ-A:_2O_3 catalysts,Dy improves the aromatization activity and stability of the catalyst and plays the role of the electron promoter.
基金Project supported bythe National Natural Science Foundation of China (50261002 ,50661002)Natural Science Foundaion of Guangxi Province (0575093)
文摘DyPt2 films were prepared by alternate deposition thin Dy and Pt layers on glass substrates by DC magneto controlled sputtering method. The XRD data indicated that for as-deposited Dy/Pt films, and the periodic layered structures along thickness direction were evidenced with low angle X-ray scattering. With increasing annealing temperature, the compounds of DyPt, DyPt2 and DyPt3 were formed successively at temperature ranging from 300 to 400 ℃. It was found that the composition reaction DyPt+DyPt3→2DyPt2 took place at 500 ℃. After annealing at 500 ℃ for 1 h, the compounds DyPt and DyPt3 transformed completely into the DyPt2 compound.
