The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xingqiu Chen - One of the best experts on this subject based on the ideXlab platform.
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vacancy mechanism of high Oxygen Solubility and nucleation of stable Oxygen enriched clusters in fe
Physical Review Letters, 2007Co-Authors: Maja Krcmar, Gayle S Painter, Xingqiu ChenAbstract:First-principles studies identify a vacancy mechanism underlying the unusually high O Solubility and nucleation of stable O-enriched nanoclusters in defect-containing Fe. Oxygen, confined as an interstitial, shows an exceptionally high affinity for vacancies, an effect enhanced by spin polarization. If vacancies preexist, the O-vacancy pair formation energy essentially vanishes, allowing the O concentration to approach that of the vacancies. This O-vacancy mechanism enables the nucleation of O-enriched nanoclusters, that attract solutes with high O affinities (Ti and Y) and strengthen Fe-based alloys.
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vacancy mechanism of high Oxygen Solubility and nucleation of stable Oxygen enriched clusters in fe
Physical Review Letters, 2007Co-Authors: C L Fu, Maja Krcmar, Gayle S Painter, Xingqiu ChenAbstract:First-principles studies have identified the atomic-level mechanism that underlies the unusually high Solubility of O and nucleation of self-assembled stable O-enriched nanoclusters in defect-containing Fe. Oxygen is confined as an interstitial in Fe such that it shows an exceptionally high affinity for vacancies (an effect that is augmented by density expansion due to spin-polarization), leading to the formation of very stable O-vacancy (O:V) pairs. If vacancies pre-exist, the formation energy of an O:V pair essentially vanishes, allowing the O concentration to become as high as that of the vacancies. This vacancy mechanism based upon O-confinement enables the nucleation of O-enriched nanoclusters, that also contain solutes (Ti and Y) with high O-affinities. Fe-based alloys strengthened by these stable nanoclusters exhibit superior mechanical properties.
S Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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investigations of the o sub 2 reduction reaction at the platinum nafion interface using a solid state electrochemical cell
Journal of The Electrochemical Society, 1991Co-Authors: Arvind Parthasarathy, Charles R Martin, S SrinivasanAbstract:This paper reports on research in solid polymer electrolyte fuel cells gaining momentum because of the prospects of attaining high energy efficiencies and power densities essential for transportation and space applications. The most advanced solid polymer electrolytes for these fuel cells are the perfluorosulfonate ionomers (PFSIs), such as Du Pont's Nafion and the Dow PFSIs. The high Oxygen Solubility, chemical stability, proton conductivity and permselectivity exhibited by Nafion and the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on electrodes from fluorinated acids enhances Oxygen reduction kinetics. The objectives of this work were to determine the concentration and diffusion coefficient of Oxygen in Nafion, and the electrode kinetic parameters for the reduction of Oxygen at the Pt/Nafion interface under totally solid-state conditions (i.e., no contacting liquid electrolyte phase). Cyclic voltammetric and potentiostatic transient measurements were made at the Pt/Nafion interface. From cyclic voltammetric measurements, the purity of Nafion was ascertained and the roughness factor of the electrode was calculated. The slow sweep experiments yielded the Tafel parameters for Oxygen reduction. From the two-section Tafelmore » plot, the calculated exchange current densities were found to be higher than those obtained at any other Pt/acid interface. From an analysis of the potentiostatic transients, the calculated values of Oxygen Solubility and diffusion coefficient in Nafion were higher than previously reported. These differences in mass-transfer data were attributed to differences in water content of the Nafion membrane.« less
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investigations of the o 2 reduction reaction at the platinum nafion interface using a solid state electrochemical cell
Journal of The Electrochemical Society, 1991Co-Authors: Arvind Parthasarathy, Charles R Martin, S SrinivasanAbstract:This paper reports on research in solid polymer electrolyte fuel cells gaining momentum because of the prospects of attaining high energy efficiencies and power densities essential for transportation and space applications. The most advanced solid polymer electrolytes for these fuel cells are the perfluorosulfonate ionomers (PFSIs), such as Du Pont's Nafion and the Dow PFSIs. The high Oxygen Solubility, chemical stability, proton conductivity and permselectivity exhibited by Nafion and the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on electrodes from fluorinated acids enhances Oxygen reduction kinetics. The objectives of this work were to determine the concentration and diffusion coefficient of Oxygen in Nafion, and the electrode kinetic parameters for the reduction of Oxygen at the Pt/Nafion interface under totally solid-state conditions (i.e., no contacting liquid electrolyte phase). Cyclic voltammetric and potentiostatic transient measurements were made at the Pt/Nafion interface. From cyclic voltammetric measurements, the purity of Nafion was ascertained and the roughness factor of the electrode was calculated. The slow sweep experiments yielded the Tafel parameters for Oxygen reduction. From the two-section Tafelmore » plot, the calculated exchange current densities were found to be higher than those obtained at any other Pt/acid interface. From an analysis of the potentiostatic transients, the calculated values of Oxygen Solubility and diffusion coefficient in Nafion were higher than previously reported. These differences in mass-transfer data were attributed to differences in water content of the Nafion membrane.« less
Y F Cheng - One of the best experts on this subject based on the ideXlab platform.
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monitoring of coating disbondment by a scanning kelvin probe technique
2010 8th International Pipeline Conference Volume 1, 2010Co-Authors: Y F ChengAbstract:The coating disbondment and corrosion of a X65 pipeline steel under coating were studied by scanning Kelvin probe (SKP) measurements. The effects of immersion time and wet-dry cycle on the Kelvin potential profile and the corrosion behavior of the steel were investigated. Kelvin potential measured on “intact” area is shifted negatively with time, indicating an increasing water uptake under the “intact” coating. There is a more negative Kelvin potential on disbonded area than that on “intact” area, which is attributed to corrosion reaction of steel occurring under the disbonded coating. During wet-dry cycle, the thickness of solution layer trapped under disbonded coating decreases due to evaporation of water, causing a negative shift of Kelvin potential. It is associated with the reduction of Oxygen Solubility in the concentrated solution during drying of electrolyte.Copyright © 2010 by ASME
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characterization of corrosion of x65 pipeline steel under disbonded coating by scanning kelvin probe
Corrosion Science, 2009Co-Authors: Y F ChengAbstract:Abstract Corrosion of X65 pipeline steel under a disbonded coating was studied by scanning Kelvin probe measurements. Three types of specimen were designed and prepared to investigate the effects of immersion time, Oxygen concentration and wet–dry cycle on Kelvin potential profile and thus corrosion behavior of the steel. Kelvin potential measured on “intact” area is shifted negatively with time, indicating an increasing water uptake under the “intact” coating. With the increase of the amount of solution, it is expected that the electrolyte concentration and electrochemical reaction rate change, resulting in a significant decrease of interfacial potential. Moreover, there is a more negative Kelvin potential on disbonded area than that on “intact” area. The negative shift of Kelvin potential is attributed to corrosion reaction of steel occurring under the disbonded coating. Due to the narrow geometry of coating disbondment, an Oxygen concentration difference exists along the depth of the disbondment. The corrosion behavior under disbonded coating strongly depends on the Oxygen partial pressure and local geometry. With continuous purging of nitrogen and removing of Oxygen, Kelvin potential tends to be identical throughout the disbonded area. During wet–dry cycle, the thickness of solution layer trapped under disbonded coating decreases due to evaporation of water. With the decrease of solution layer thickness, the measured Kelvin potential decreases, indicating that the effect associated with the reduction of Oxygen Solubility in the concentrated solution during drying of electrolyte is favored over that related to the enhanced Oxygen diffusion and reduction. There exists a critical thickness of solution layer, below which the Oxygen Solubility is sufficiently low to support the electrochemical corrosion reaction of steel.
Arvind Parthasarathy - One of the best experts on this subject based on the ideXlab platform.
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investigations of the o sub 2 reduction reaction at the platinum nafion interface using a solid state electrochemical cell
Journal of The Electrochemical Society, 1991Co-Authors: Arvind Parthasarathy, Charles R Martin, S SrinivasanAbstract:This paper reports on research in solid polymer electrolyte fuel cells gaining momentum because of the prospects of attaining high energy efficiencies and power densities essential for transportation and space applications. The most advanced solid polymer electrolytes for these fuel cells are the perfluorosulfonate ionomers (PFSIs), such as Du Pont's Nafion and the Dow PFSIs. The high Oxygen Solubility, chemical stability, proton conductivity and permselectivity exhibited by Nafion and the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on electrodes from fluorinated acids enhances Oxygen reduction kinetics. The objectives of this work were to determine the concentration and diffusion coefficient of Oxygen in Nafion, and the electrode kinetic parameters for the reduction of Oxygen at the Pt/Nafion interface under totally solid-state conditions (i.e., no contacting liquid electrolyte phase). Cyclic voltammetric and potentiostatic transient measurements were made at the Pt/Nafion interface. From cyclic voltammetric measurements, the purity of Nafion was ascertained and the roughness factor of the electrode was calculated. The slow sweep experiments yielded the Tafel parameters for Oxygen reduction. From the two-section Tafelmore » plot, the calculated exchange current densities were found to be higher than those obtained at any other Pt/acid interface. From an analysis of the potentiostatic transients, the calculated values of Oxygen Solubility and diffusion coefficient in Nafion were higher than previously reported. These differences in mass-transfer data were attributed to differences in water content of the Nafion membrane.« less
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investigations of the o 2 reduction reaction at the platinum nafion interface using a solid state electrochemical cell
Journal of The Electrochemical Society, 1991Co-Authors: Arvind Parthasarathy, Charles R Martin, S SrinivasanAbstract:This paper reports on research in solid polymer electrolyte fuel cells gaining momentum because of the prospects of attaining high energy efficiencies and power densities essential for transportation and space applications. The most advanced solid polymer electrolytes for these fuel cells are the perfluorosulfonate ionomers (PFSIs), such as Du Pont's Nafion and the Dow PFSIs. The high Oxygen Solubility, chemical stability, proton conductivity and permselectivity exhibited by Nafion and the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on the Dow PFSIs make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on electrodes from fluorinated acids enhances Oxygen reduction kinetics. The objectives of this work were to determine the concentration and diffusion coefficient of Oxygen in Nafion, and the electrode kinetic parameters for the reduction of Oxygen at the Pt/Nafion interface under totally solid-state conditions (i.e., no contacting liquid electrolyte phase). Cyclic voltammetric and potentiostatic transient measurements were made at the Pt/Nafion interface. From cyclic voltammetric measurements, the purity of Nafion was ascertained and the roughness factor of the electrode was calculated. The slow sweep experiments yielded the Tafel parameters for Oxygen reduction. From the two-section Tafelmore » plot, the calculated exchange current densities were found to be higher than those obtained at any other Pt/acid interface. From an analysis of the potentiostatic transients, the calculated values of Oxygen Solubility and diffusion coefficient in Nafion were higher than previously reported. These differences in mass-transfer data were attributed to differences in water content of the Nafion membrane.« less
Maja Krcmar - One of the best experts on this subject based on the ideXlab platform.
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vacancy mechanism of high Oxygen Solubility and nucleation of stable Oxygen enriched clusters in fe
Physical Review Letters, 2007Co-Authors: Maja Krcmar, Gayle S Painter, Xingqiu ChenAbstract:First-principles studies identify a vacancy mechanism underlying the unusually high O Solubility and nucleation of stable O-enriched nanoclusters in defect-containing Fe. Oxygen, confined as an interstitial, shows an exceptionally high affinity for vacancies, an effect enhanced by spin polarization. If vacancies preexist, the O-vacancy pair formation energy essentially vanishes, allowing the O concentration to approach that of the vacancies. This O-vacancy mechanism enables the nucleation of O-enriched nanoclusters, that attract solutes with high O affinities (Ti and Y) and strengthen Fe-based alloys.
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vacancy mechanism of high Oxygen Solubility and nucleation of stable Oxygen enriched clusters in fe
Physical Review Letters, 2007Co-Authors: C L Fu, Maja Krcmar, Gayle S Painter, Xingqiu ChenAbstract:First-principles studies have identified the atomic-level mechanism that underlies the unusually high Solubility of O and nucleation of self-assembled stable O-enriched nanoclusters in defect-containing Fe. Oxygen is confined as an interstitial in Fe such that it shows an exceptionally high affinity for vacancies (an effect that is augmented by density expansion due to spin-polarization), leading to the formation of very stable O-vacancy (O:V) pairs. If vacancies pre-exist, the formation energy of an O:V pair essentially vanishes, allowing the O concentration to become as high as that of the vacancies. This vacancy mechanism based upon O-confinement enables the nucleation of O-enriched nanoclusters, that also contain solutes (Ti and Y) with high O-affinities. Fe-based alloys strengthened by these stable nanoclusters exhibit superior mechanical properties.
