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Electrochemical methods study on corrosion of 5% Al–Zn alloy-coated steel under thin electrolyte layers / S. Xing in Materials and corrosion, Vol. 61 N° 5 (Mai 2010) 

Public ISBD [article]  in Materials and corrosion > Vol. 61 N° 5 (Mai 2010) . - pp. 428–431 Titre : Electrochemical methods study on corrosion of 5% Al–Zn alloy-coated steel under thin electrolyte layers Type de document : texte imprimé Auteurs : S. Xing, Auteur ; Y. Li, Auteur ; J. Wu, Auteur Année de publication : 2010 Article en page(s) : pp. 428–431 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : 5%  Al–Zn;  corrosion  monitoring;  electrochemical  impedance  spectroscopy;  wet–dry  condition Résumé : The corrosion behavior of a 5% Al–Zn alloy (GF) coated steel was investigated under cyclic wet–dry condition using electrochemical techniques. The wet–dry cycle was conducted by exposure to alternate condition of 1 h immersion in seawater and 7 h drying at ambient temperature. The polarization resistance, Rp of the coating was monitored during the wet–dry cycles by two points AC impedance method and the corrosion potential, Ecorr was measured only when the coating was immersed in seawater. Simultaneously, the electrochemical impedance spectroscopy (EIS) of the coating was obtained after it was immersed in different cycles of wet–dry condition. The results obtained by two points AC impedance method had good agreement with those achieved from EIS technique, which proved that the two points AC impedance method was correct and an effective method for atmospheric corrosion study. The monitoring results indicated that the corrosion rate of GF coating firstly increased, then decreased slowly with time, and at last reached a relative steady state with local corrosion under the cyclic wet–dry alternate condition. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905313/abstract [article] Electrochemical methods study on corrosion of 5% Al–Zn alloy-coated steel under thin electrolyte layers [texte imprimé] / S. Xing, Auteur ; Y. Li, Auteur ; J. Wu, Auteur . - 2010 . - pp. 428–431. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 61 N° 5 (Mai 2010) . - pp. 428–431 Mots-clés : 5%  Al–Zn;  corrosion  monitoring;  electrochemical  impedance  spectroscopy;  wet–dry  condition Résumé : The corrosion behavior of a 5% Al–Zn alloy (GF) coated steel was investigated under cyclic wet–dry condition using electrochemical techniques. The wet–dry cycle was conducted by exposure to alternate condition of 1 h immersion in seawater and 7 h drying at ambient temperature. The polarization resistance, Rp of the coating was monitored during the wet–dry cycles by two points AC impedance method and the corrosion potential, Ecorr was measured only when the coating was immersed in seawater. Simultaneously, the electrochemical impedance spectroscopy (EIS) of the coating was obtained after it was immersed in different cycles of wet–dry condition. The results obtained by two points AC impedance method had good agreement with those achieved from EIS technique, which proved that the two points AC impedance method was correct and an effective method for atmospheric corrosion study. The monitoring results indicated that the corrosion rate of GF coating firstly increased, then decreased slowly with time, and at last reached a relative steady state with local corrosion under the cyclic wet–dry alternate condition. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905313/abstract

HRTEM and EELS study of aluminum nitride in nanostructured Al 5083/B4C processed via cryomilling / Y. Li in Acta materialia, Vol. 58 N° 5 (Mars 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1732–1740 Titre : HRTEM and EELS study of aluminum nitride in nanostructured Al 5083/B4C processed via cryomilling Type de document : texte imprimé Auteurs : Y. Li, Auteur ; W. Liu, Auteur ; V. Ortalan, Auteur Année de publication : 2011 Article en page(s) : pp. 1732–1740 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : High-resolution  electron  microscopy  (HREM)  Electron  energy  loss  spectroscopy  (EELS)  Transmission  electron  microscopy  (TEM)  Particulate  reinforced  composites  Metal  matrix  composites  (MMC) Résumé : The presence of aluminum nitride in nanostructured aluminum metal matrix composites was studied by high resolution transmission electron microscopy, electron energy loss spectroscopy, energy dispersive X-ray spectroscopy analysis and electron microscopy simulations. Three types of aluminum nitride structures were identified; predominantly, one layer of N atoms occupies the tetrahedral interstitial positions in the Al lattice, the frequency of which varies as a function of spatial location. The second and third were in the form of hexagonal and possibly cubic aluminum nitride particles with particle sizes on the order of 15–20 nm. The results suggest that the aluminum nitride phase evolves from intermediate transitional structures that involve N atoms in the Al lattice. The aluminum nitride phases frequently contained O and Mg, which preferentially segregate in close proximity to the reinforcement particles. First-principle calculations were used to describe the influence of O and Mg on the adsorption of N. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007940 [article] HRTEM and EELS study of aluminum nitride in nanostructured Al 5083/B4C processed via cryomilling [texte imprimé] / Y. Li, Auteur ; W. Liu, Auteur ; V. Ortalan, Auteur . - 2011 . - pp. 1732–1740. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1732–1740 Mots-clés : High-resolution  electron  microscopy  (HREM)  Electron  energy  loss  spectroscopy  (EELS)  Transmission  electron  microscopy  (TEM)  Particulate  reinforced  composites  Metal  matrix  composites  (MMC) Résumé : The presence of aluminum nitride in nanostructured aluminum metal matrix composites was studied by high resolution transmission electron microscopy, electron energy loss spectroscopy, energy dispersive X-ray spectroscopy analysis and electron microscopy simulations. Three types of aluminum nitride structures were identified; predominantly, one layer of N atoms occupies the tetrahedral interstitial positions in the Al lattice, the frequency of which varies as a function of spatial location. The second and third were in the form of hexagonal and possibly cubic aluminum nitride particles with particle sizes on the order of 15–20 nm. The results suggest that the aluminum nitride phase evolves from intermediate transitional structures that involve N atoms in the Al lattice. The aluminum nitride phases frequently contained O and Mg, which preferentially segregate in close proximity to the reinforcement particles. First-principle calculations were used to describe the influence of O and Mg on the adsorption of N. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007940

Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions / M. M. Abou-Ellail in Journal of heat transfer, Vol. 133 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114501/1-12] Titre : Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions Type de document : texte imprimé Auteurs : M. M. Abou-Ellail, Auteur ; T. W. Tong, Auteur ; Y. Li, Auteur Année de publication : 2012 Article en page(s) : pp. [114501/1-12] Note générale : Physique Langues : Anglais (eng) Mots-clés : Cataytic  surface  reaction  Hydrogen/air  Numerical  methods Index. décimale : 536 Chaleur. Thermodynamique Résumé : Catalytic combustion of hydrogen–air boundary layers involves the adsorption of hydrogen and oxygen into a platinum coated surface, chemical reactions of the adsorbed species, and the desorption of the resulting products. Re-adsorption of some produced gases is also possible. The catalytic reactions can be beneficial in porous burners and catalytic reactors that use low equivalence ratios. In this case, the porous burner flame can be stabilized at low temperatures to prevent any substantial gas emissions, such as nitrogen oxides. The present paper is concerned with the numerical computation of heat transfer and chemical reactions in hydrogen–air mixture boundary layers that flow over platinum coated hot plates and inside rectangular channels. Chemical reactions are included in the gas-phase as well as on the solid platinum surface. In the gas-phase, eight species are involved in 26 elementary reactions. On the platinum hot surface, additional surface species are included that are involved in 16 additional surface chemical reactions. The platinum surface temperature distribution is prespecified, while the properties of the reacting flow are computed. The flow configurations investigated in the present paper are those of a flat plate boundary layer and a rectangular channel reacting flow. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Hybrid differencing is used to ensure that the finite-difference coefficients are always positive or equal to zero to reflect the real effect of neighboring nodes on a typical central node. The finite-volume equations are solved iteratively for the reacting gas flow properties. On the platinum surface, surface species balance equations, under steady-state conditions, are solved numerically. A nonuniform computational grid is used, concentrating most of the nodes in the boundary sub-layer adjoining the catalytic surface. For the flat plate boundary layer flow, the computed OH concentration is compared with experimental and numerical data of similar geometry. The obtained agreement is fairly good, with differences observed for the location of the peak value of OH. Surface temperature of 1170 K caused fast reactions on the catalytic surface in a very small part at the leading edge of the catalytic flat plate. The flat plate computational results for heat and mass transfer and chemical surface reactions at the gas-surface interface are correlated by nondimensional relations. The channel flow computational results are also compared with recent detailed experimental data for similar geometry. In this case, the catalytic surface temperature profile along the x-axis was measured accurately and is used in the present work as the boundary condition for the gas-phase energy equation. The present numerical results for the gas temperature, water vapor mole fraction, and hydrogen mole fraction are compared with the corresponding experimental data. In general, the agreement is very good especially in the first 105 mm. However, some differences are observed in the vicinity of the exit section of the rectangular channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions [texte imprimé] / M. M. Abou-Ellail, Auteur ; T. W. Tong, Auteur ; Y. Li, Auteur . - 2012 . - pp. [114501/1-12]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114501/1-12] Mots-clés : Cataytic  surface  reaction  Hydrogen/air  Numerical  methods Index. décimale : 536 Chaleur. Thermodynamique Résumé : Catalytic combustion of hydrogen–air boundary layers involves the adsorption of hydrogen and oxygen into a platinum coated surface, chemical reactions of the adsorbed species, and the desorption of the resulting products. Re-adsorption of some produced gases is also possible. The catalytic reactions can be beneficial in porous burners and catalytic reactors that use low equivalence ratios. In this case, the porous burner flame can be stabilized at low temperatures to prevent any substantial gas emissions, such as nitrogen oxides. The present paper is concerned with the numerical computation of heat transfer and chemical reactions in hydrogen–air mixture boundary layers that flow over platinum coated hot plates and inside rectangular channels. Chemical reactions are included in the gas-phase as well as on the solid platinum surface. In the gas-phase, eight species are involved in 26 elementary reactions. On the platinum hot surface, additional surface species are included that are involved in 16 additional surface chemical reactions. The platinum surface temperature distribution is prespecified, while the properties of the reacting flow are computed. The flow configurations investigated in the present paper are those of a flat plate boundary layer and a rectangular channel reacting flow. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Hybrid differencing is used to ensure that the finite-difference coefficients are always positive or equal to zero to reflect the real effect of neighboring nodes on a typical central node. The finite-volume equations are solved iteratively for the reacting gas flow properties. On the platinum surface, surface species balance equations, under steady-state conditions, are solved numerically. A nonuniform computational grid is used, concentrating most of the nodes in the boundary sub-layer adjoining the catalytic surface. For the flat plate boundary layer flow, the computed OH concentration is compared with experimental and numerical data of similar geometry. The obtained agreement is fairly good, with differences observed for the location of the peak value of OH. Surface temperature of 1170 K caused fast reactions on the catalytic surface in a very small part at the leading edge of the catalytic flat plate. The flat plate computational results for heat and mass transfer and chemical surface reactions at the gas-surface interface are correlated by nondimensional relations. The channel flow computational results are also compared with recent detailed experimental data for similar geometry. In this case, the catalytic surface temperature profile along the x-axis was measured accurately and is used in the present work as the boundary condition for the gas-phase energy equation. The present numerical results for the gas temperature, water vapor mole fraction, and hydrogen mole fraction are compared with the corresponding experimental data. In general, the agreement is very good especially in the first 105 mm. However, some differences are observed in the vicinity of the exit section of the rectangular channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]