We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） sub...We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） substrates. Our studies show that the properties of these films （surface energy, work-function, charge density decay length in a vacuum and chemical reactivity） exhibit pronounced oscillatory behavior as a function of the film thickness, with an oscillation period of about four MLs for both cases due to the relationship of the match between the Fermi wave vector and the film thickness. Due to the localization of d-electron of Ru films, these quantum oscillations almost disappear when the thickness of the film is more than -20 ML for the free standing Ru films, while for the Ru films on Pt substrates the oscillations disappear quickly when the thickness of the film is beyond -13 ML. Our results reveal that the stability and reactivity of the Ru films could be tailored through Q, SE and the Ru bilayer grown on Pt substrates observed in the experiment is also related to the effect.展开更多
The paper describes the instrumentation for studying temperature and void reactivity effects that were developed at VR-I zero power reactor. Further are described its operational parameters, fields and ways of its uti...The paper describes the instrumentation for studying temperature and void reactivity effects that were developed at VR-I zero power reactor. Further are described its operational parameters, fields and ways of its utilization as well as issues connected to its implementation into the reactor core.展开更多
Three different chromizing coatings were produced on Ni substrate using a conventional pack-cementation method with Al2O3,Al2O3＋CeO2 and CeO2 acting as filler,respectively,at a greatly decreased temperature（700 ℃）...Three different chromizing coatings were produced on Ni substrate using a conventional pack-cementation method with Al2O3,Al2O3＋CeO2 and CeO2 acting as filler,respectively,at a greatly decreased temperature（700 ℃）.Effects of different fillers on the isothermal and cyclic oxidation resistance of chromizing coating in air at 850 ℃ were comparably investigated.Microstructure results show that the addition of CeO2 into the filler significantly retards the grain growth of the chromizing coating.Oxidation results indicate that the chromizing coating using CeO2 as filler exhibits somewhat increased oxidation resistance than the normal chromizmg coating,while the chromizing coating using Al2O3＋CeO2 as filler exhibits much better oxidation resistance.The effects of different fillers on the oxidation behaviors were discussed in detail.展开更多
Ni-La2O3/CeO2 composite films were prepared by electrodeposition from a nickel sulfate bath containing certain content of micrometer and nanometer La2O3/CeO2 particles. The effect of La2O3 or CeO2 particle size on the...Ni-La2O3/CeO2 composite films were prepared by electrodeposition from a nickel sulfate bath containing certain content of micrometer and nanometer La2O3/CeO2 particles. The effect of La2O3 or CeO2 particle size on the oxidation resistance of the electrodeposited Ni-La2O3/CeO2 composites in air at 1000 °C was studied. The results indicate that, compared with the electrodeposited Ni-film, Ni-La2O3/CeO2 composites exhibit a superior oxidation resistance due to the codeposited La2O3 or CeO2 particles blocking the outward diffusion of nickel. Moreover, compared with nanoparticles, La2O3 or CeO2 microparticles have stronger effect because La2O3 or CeO2 microparticles also act as a diffusion barrier layer at the onset of oxidation.展开更多
By using CeO2 particles instead of part of Al2O3 particles as filler, the CeO2 was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline （NC） and microcrystalline...By using CeO2 particles instead of part of Al2O3 particles as filler, the CeO2 was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline （NC） and microcrystalline （MC） Ni films using a conventional pack-cementation method at 800 °C. For comparison, chromizing was also performed under the same condition on MC Ni film using Al2O3 as filler without CeO2 particles. SEM/EDX and TEM results indicate that the refinement of Ni grain and CeO2 entrapped into the chromizing coatings refine the grain of the chromizing coating. Oxidation at 900 °C indicates that compared with the CeO2-free chromizing coating, the CeO2-dispersed chromizing coating exhibits an increased oxidation resistance. For the CeO2-dispersed chromizing coating, the refinement of Ni grain size significantly decreases the transient-oxidation scaling rate of the chromizing coatings. Together with this, the CeO2-dispersed chromizing coating formed on NC Ni exhibits a better oxidation resistance.展开更多
Ni3Al coatings with and without Y2O3 particles were developed by annealing the electrodeposited Ni-Al composite coatings with and without Y2O3 particles at 800°C for 3 h.The microstructures and cyclic oxidation p...Ni3Al coatings with and without Y2O3 particles were developed by annealing the electrodeposited Ni-Al composite coatings with and without Y2O3 particles at 800°C for 3 h.The microstructures and cyclic oxidation performances of the produced Ni3Al coatings were comparatively investigated,with the emphasis on the effect of Y2O3.SEM/EDAX and TEM characterizations showed that the dispersion of Y2O3 refines the grains.Oxidation at 900°C for 100 h showed that the addition of Y2O3 significantly improved the cyclic oxidation resistance of Ni3Al coating.The effect of Y2O3 on the microstructure and the oxidation of the Ni3Al coating were discussed in detail.展开更多
Oxide pegging is a widely accepted mechanistic model explaining the reactive element effect on the improved adherence of scale.However,previous models for the oxide peg formation process have not considered the effect...Oxide pegging is a widely accepted mechanistic model explaining the reactive element effect on the improved adherence of scale.However,previous models for the oxide peg formation process have not considered the effects of more than one active element added into the alloy during the peg formation.This study proposes a new model of oxide peg formation and growth for the doping of two reactive elements in an alloy(the precipitated Y and solid solute Ti).Different amounts of Ti and Y were added to a Co Ni Cr Al alloy,and the characteristics of the resulting oxide pegs,such as their linear density,size,and forming process,are obtained by examining alloy samples subjected to an isothermal oxidation operation at a temperature of 1150℃.It is found that the amount of Y determines the density of the oxide pegs,and Ti does not form a Ti-rich oxide core if a Y-rich oxide exists in the sample.In samples with the same Y content,the oxide pegs primarily grow in length,and with increased Ti content,they grow along the b-phase boundary and into the alloy.Based on these results,a three-step model for oxide peg formation and growth is conceived.展开更多
The effect of mixed oxide support on the performance of Ni/ZnO in the reactive adsorption desulfurization(RADS) reaction was investigated in a fixed bed reactor by using thiophene as the sulfur-containing compound in ...The effect of mixed oxide support on the performance of Ni/ZnO in the reactive adsorption desulfurization(RADS) reaction was investigated in a fixed bed reactor by using thiophene as the sulfur-containing compound in the model gasoline. A series of oxide supports for Ni/ZnO were synthesized by the co-precipitation method and characterized by XRD, N_2-adsorption, TPR and NH_3-TPD techniques. It was found that the desulfurization capacity of Ni/ZnO was enhanced greatly when active components were supported on the proper mixed oxide. Ni/ZnO supported on oxides exhibited much higher desulfurization efficiency and sulfur adsorption capacity than the unsupported Ni/ZnO and the synthesized Ni/ZnO-SA adsorbent exhibited the highest efficiency for thiophene removal. The higher desulfurization activity and sulfur capacity of Ni/ZnO supported on SiO_2-Al_2O_3 with small particle size, high specific surface area and large pore volume could promote the high dispersion of active metal phase and the transfer of sulfur to ZnO with lower mass transfer resistance. γ-Al_2O_3 species could weaken the interaction of active phases and SiO_2 as well as could increase greatly the amount of weak acids. Therefore, these oxides could impose a great influence on the structure and chemical properties of the catalyst.展开更多
Objective To investigatewhether antioxidants inhibit adhesion of leukocytes to endothelium and furthermore, whether all antioxidants regulate NF-KB activation through a redox sensitive mechanism. Methods The effect of...Objective To investigatewhether antioxidants inhibit adhesion of leukocytes to endothelium and furthermore, whether all antioxidants regulate NF-KB activation through a redox sensitive mechanism. Methods The effect of the antioxidative substances pyrrolidin dithiocarbamat (PDTC), dichloroisocumarin (DCI), chrysin and probucol on the endothelial leukocyte adhesion were examined under near physiological flow conditions. The antioxidative activity of antioxidants was measured in a DCF fluorescence assay with flow cytometry. The activation of NF-kB in endothelial cells was investigated in a gel shift assay. Results PDTC and probucol did not show an inhibitory effect to the formation of intracellular H2O2 in TNFa activated human vascular endothelial cells (HUVEC) . Chrysin showed a moderate effect. DCI showed a strong antioxidative effect. In contrast, PDTC and chrysin inhibited the adhesion of HL 60 cells to TNFa-stimulated HUVEC. DCI and probucol did not have influence on the adhesion within the area of the examined shear stresses. Only PDTC inhibited the TNFa-induced activation of NF-KB in endothelial cells. Conclusion The inhibition of the endothelial leukocyte adhesion by antioxidative substances is not to be explained by its antioxidative characteristics only. The inhibitory effect of PDTC on NF-KB activation was probably not related to its antioxidative properties. Endothelial cell Antioxidants NF-kappa-B展开更多
文摘We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） substrates. Our studies show that the properties of these films （surface energy, work-function, charge density decay length in a vacuum and chemical reactivity） exhibit pronounced oscillatory behavior as a function of the film thickness, with an oscillation period of about four MLs for both cases due to the relationship of the match between the Fermi wave vector and the film thickness. Due to the localization of d-electron of Ru films, these quantum oscillations almost disappear when the thickness of the film is more than -20 ML for the free standing Ru films, while for the Ru films on Pt substrates the oscillations disappear quickly when the thickness of the film is beyond -13 ML. Our results reveal that the stability and reactivity of the Ru films could be tailored through Q, SE and the Ru bilayer grown on Pt substrates observed in the experiment is also related to the effect.
文摘The paper describes the instrumentation for studying temperature and void reactivity effects that were developed at VR-I zero power reactor. Further are described its operational parameters, fields and ways of its utilization as well as issues connected to its implementation into the reactor core.
基金Project (11551419) supported by Scientific Research Fund of Heilongjiang Provincial Education DepartmentProject (12511469) supported by Heilongjiang Provincial Science and Technology Department
文摘Three different chromizing coatings were produced on Ni substrate using a conventional pack-cementation method with Al2O3,Al2O3＋CeO2 and CeO2 acting as filler,respectively,at a greatly decreased temperature（700 ℃）.Effects of different fillers on the isothermal and cyclic oxidation resistance of chromizing coating in air at 850 ℃ were comparably investigated.Microstructure results show that the addition of CeO2 into the filler significantly retards the grain growth of the chromizing coating.Oxidation results indicate that the chromizing coating using CeO2 as filler exhibits somewhat increased oxidation resistance than the normal chromizmg coating,while the chromizing coating using Al2O3＋CeO2 as filler exhibits much better oxidation resistance.The effects of different fillers on the oxidation behaviors were discussed in detail.
基金Project(GC13A113)supported by the Technology Research and Development Program of Heilongjiang Provincial Science and Technology DepartmentProject(12511469)supported by Heilongjiang Provincial Science and Technology Department
文摘Ni-La2O3/CeO2 composite films were prepared by electrodeposition from a nickel sulfate bath containing certain content of micrometer and nanometer La2O3/CeO2 particles. The effect of La2O3 or CeO2 particle size on the oxidation resistance of the electrodeposited Ni-La2O3/CeO2 composites in air at 1000 °C was studied. The results indicate that, compared with the electrodeposited Ni-film, Ni-La2O3/CeO2 composites exhibit a superior oxidation resistance due to the codeposited La2O3 or CeO2 particles blocking the outward diffusion of nickel. Moreover, compared with nanoparticles, La2O3 or CeO2 microparticles have stronger effect because La2O3 or CeO2 microparticles also act as a diffusion barrier layer at the onset of oxidation.
基金Project(11531319)supported by Scientific Research Fund of Heilongjiang Provincial Education Department,China
文摘By using CeO2 particles instead of part of Al2O3 particles as filler, the CeO2 was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline （NC） and microcrystalline （MC） Ni films using a conventional pack-cementation method at 800 °C. For comparison, chromizing was also performed under the same condition on MC Ni film using Al2O3 as filler without CeO2 particles. SEM/EDX and TEM results indicate that the refinement of Ni grain and CeO2 entrapped into the chromizing coatings refine the grain of the chromizing coating. Oxidation at 900 °C indicates that compared with the CeO2-free chromizing coating, the CeO2-dispersed chromizing coating exhibits an increased oxidation resistance. For the CeO2-dispersed chromizing coating, the refinement of Ni grain size significantly decreases the transient-oxidation scaling rate of the chromizing coatings. Together with this, the CeO2-dispersed chromizing coating formed on NC Ni exhibits a better oxidation resistance.
基金Project(11531319)supported by Scientific Research Fund of Heilongjiang Provincial Education Department,China
文摘Ni3Al coatings with and without Y2O3 particles were developed by annealing the electrodeposited Ni-Al composite coatings with and without Y2O3 particles at 800°C for 3 h.The microstructures and cyclic oxidation performances of the produced Ni3Al coatings were comparatively investigated,with the emphasis on the effect of Y2O3.SEM/EDAX and TEM characterizations showed that the dispersion of Y2O3 refines the grains.Oxidation at 900°C for 100 h showed that the addition of Y2O3 significantly improved the cyclic oxidation resistance of Ni3Al coating.The effect of Y2O3 on the microstructure and the oxidation of the Ni3Al coating were discussed in detail.
基金financially supported by Tsinghua University Initiative Scientific Research Program and the National Magnetic Confinement Fusion Energy Research Project of China(No.2015GB118001)。
文摘Oxide pegging is a widely accepted mechanistic model explaining the reactive element effect on the improved adherence of scale.However,previous models for the oxide peg formation process have not considered the effects of more than one active element added into the alloy during the peg formation.This study proposes a new model of oxide peg formation and growth for the doping of two reactive elements in an alloy(the precipitated Y and solid solute Ti).Different amounts of Ti and Y were added to a Co Ni Cr Al alloy,and the characteristics of the resulting oxide pegs,such as their linear density,size,and forming process,are obtained by examining alloy samples subjected to an isothermal oxidation operation at a temperature of 1150℃.It is found that the amount of Y determines the density of the oxide pegs,and Ti does not form a Ti-rich oxide core if a Y-rich oxide exists in the sample.In samples with the same Y content,the oxide pegs primarily grow in length,and with increased Ti content,they grow along the b-phase boundary and into the alloy.Based on these results,a three-step model for oxide peg formation and growth is conceived.
基金financially supported by the National Natural Science Foundation of China(No.21276086)
文摘The effect of mixed oxide support on the performance of Ni/ZnO in the reactive adsorption desulfurization(RADS) reaction was investigated in a fixed bed reactor by using thiophene as the sulfur-containing compound in the model gasoline. A series of oxide supports for Ni/ZnO were synthesized by the co-precipitation method and characterized by XRD, N_2-adsorption, TPR and NH_3-TPD techniques. It was found that the desulfurization capacity of Ni/ZnO was enhanced greatly when active components were supported on the proper mixed oxide. Ni/ZnO supported on oxides exhibited much higher desulfurization efficiency and sulfur adsorption capacity than the unsupported Ni/ZnO and the synthesized Ni/ZnO-SA adsorbent exhibited the highest efficiency for thiophene removal. The higher desulfurization activity and sulfur capacity of Ni/ZnO supported on SiO_2-Al_2O_3 with small particle size, high specific surface area and large pore volume could promote the high dispersion of active metal phase and the transfer of sulfur to ZnO with lower mass transfer resistance. γ-Al_2O_3 species could weaken the interaction of active phases and SiO_2 as well as could increase greatly the amount of weak acids. Therefore, these oxides could impose a great influence on the structure and chemical properties of the catalyst.
文摘Objective To investigatewhether antioxidants inhibit adhesion of leukocytes to endothelium and furthermore, whether all antioxidants regulate NF-KB activation through a redox sensitive mechanism. Methods The effect of the antioxidative substances pyrrolidin dithiocarbamat (PDTC), dichloroisocumarin (DCI), chrysin and probucol on the endothelial leukocyte adhesion were examined under near physiological flow conditions. The antioxidative activity of antioxidants was measured in a DCF fluorescence assay with flow cytometry. The activation of NF-kB in endothelial cells was investigated in a gel shift assay. Results PDTC and probucol did not show an inhibitory effect to the formation of intracellular H2O2 in TNFa activated human vascular endothelial cells (HUVEC) . Chrysin showed a moderate effect. DCI showed a strong antioxidative effect. In contrast, PDTC and chrysin inhibited the adhesion of HL 60 cells to TNFa-stimulated HUVEC. DCI and probucol did not have influence on the adhesion within the area of the examined shear stresses. Only PDTC inhibited the TNFa-induced activation of NF-KB in endothelial cells. Conclusion The inhibition of the endothelial leukocyte adhesion by antioxidative substances is not to be explained by its antioxidative characteristics only. The inhibitory effect of PDTC on NF-KB activation was probably not related to its antioxidative properties. Endothelial cell Antioxidants NF-kappa-B
