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Study on hot corrosion behavior of Yb2Zr2O7 ceramic against Na2SO4+V2O5molten salts at temperatures of 900-1200 °C en air / Li, S. in Materials and corrosion, Vol. 63 N° 4 (Avril 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 4 (Avril 2012) . - pp. 303–309 Titre : Study on hot corrosion behavior of Yb2Zr2O7 ceramic against Na2SO4+V2O5molten salts at temperatures of 900-1200 °C en air Type de document : texte imprimé Auteurs : Li, S., Auteur ; Z.-G. Liu, Auteur ; J.-H. Ouyang, Auteur Année de publication : 2012 Article en page(s) : pp. 303–309 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : fluxing  mechanism;  hot  corrosion;  Na2SO4;  V2O5;  Yb2Zr2O7 Résumé : Yb2Zr2O7 ceramic powders synthesized by chemical-coprecipitation and calcination method were pressureless-sintered at 1700 °C for 10 h in air to fabricate dense bulk materials. Hot corrosion studies were performed on Yb2Zr2O7 against Na2SO4 and Na2SO4 + V2O5 (molar ratio = 1:1) molten salts in a temperature range of 900–1200 °C for 8 h in air, respectively. Chemical reactions were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Yb2Zr2O7 ceramic was severely corroded by Na2SO4 + V2O5 molten salt, however, no chemical reaction was found between individual Na2SO4 and Yb2Zr2O7. Yb2Zr2O7 reacted with Na2SO4 + V2O5 molten salt to form YbVO4 and m-ZrO2. The thickness of hot corrosion scales formed at different temperatures was investigated to evaluate hot corrosion behavior based on fluxing mechanism. The introduction of vanadium into sulfate led to subsequent formation of NaVO3, which was acidic enough to dissolve Yb2Zr2O7 by acidic fluxing. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005779/abstract [article] Study on hot corrosion behavior of Yb2Zr2O7 ceramic against Na2SO4+V2O5molten salts at temperatures of 900-1200 °C en air [texte imprimé] / Li, S., Auteur ; Z.-G. Liu, Auteur ; J.-H. Ouyang, Auteur . - 2012 . - pp. 303–309. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 4 (Avril 2012) . - pp. 303–309 Mots-clés : fluxing  mechanism;  hot  corrosion;  Na2SO4;  V2O5;  Yb2Zr2O7 Résumé : Yb2Zr2O7 ceramic powders synthesized by chemical-coprecipitation and calcination method were pressureless-sintered at 1700 °C for 10 h in air to fabricate dense bulk materials. Hot corrosion studies were performed on Yb2Zr2O7 against Na2SO4 and Na2SO4 + V2O5 (molar ratio = 1:1) molten salts in a temperature range of 900–1200 °C for 8 h in air, respectively. Chemical reactions were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Yb2Zr2O7 ceramic was severely corroded by Na2SO4 + V2O5 molten salt, however, no chemical reaction was found between individual Na2SO4 and Yb2Zr2O7. Yb2Zr2O7 reacted with Na2SO4 + V2O5 molten salt to form YbVO4 and m-ZrO2. The thickness of hot corrosion scales formed at different temperatures was investigated to evaluate hot corrosion behavior based on fluxing mechanism. The introduction of vanadium into sulfate led to subsequent formation of NaVO3, which was acidic enough to dissolve Yb2Zr2O7 by acidic fluxing. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005779/abstract

A transient mixed elastohydrodynamic lubrication model for spur gear pairs / Li, S. in Transactions of the ASME . Journal of tribology, Vol. 132 N° 1 (Janvier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 1 (Janvier 2010) . - 09 p. Titre : A transient mixed elastohydrodynamic lubrication model for spur gear pairs Type de document : texte imprimé Auteurs : Li, S., Auteur ; Kahraman, A., Auteur Année de publication : 2010 Article en page(s) : 09 p. Langues : Anglais (eng) Mots-clés : Gear  lubrication  Transient  EHL  Mixed  EHL Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this study, a transient, non-Newtonian, mixed elastohydrodynamic lubrication (EHL) model of involute spur gear tooth contacts is proposed. Unlike the contact between two cylindrical rollers, spur gear contacts experience a number of time-varying contact parameters including the normal load, radii of curvature, surface velocities, and slide-to-roll ratio. The proposed EHL model is designed to continuously follow the contact of a tooth pair from the root to the tip to capture the transient characteristics of lubricated spur gear contacts due to these parameter variations, instead of analyzing the contact at discrete positions assuming time-invariant parameters. The normal tooth force along the line of action is predicted by using a gear load distribution formulation and the contact radii and tangential surface velocities are computed from the kinematics and geometry of involute profiles. A unified numerical approach is adapted for handling asperity interaction in mixed EHL conditions. The differences between the transient and discrete EHL analyses are shown for a spur gear pair having smooth surfaces and different tooth profile modifications. The transient behavior predicted by the proposed model is found to be mainly due to the squeezing and pumping effects caused by sudden load changes. The lubrication behavior under rough conditions is also investigated at different operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013200 [...] [article] A transient mixed elastohydrodynamic lubrication model for spur gear pairs [texte imprimé] / Li, S., Auteur ; Kahraman, A., Auteur . - 2010 . - 09 p. Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 1 (Janvier 2010) . - 09 p. Mots-clés : Gear  lubrication  Transient  EHL  Mixed  EHL Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this study, a transient, non-Newtonian, mixed elastohydrodynamic lubrication (EHL) model of involute spur gear tooth contacts is proposed. Unlike the contact between two cylindrical rollers, spur gear contacts experience a number of time-varying contact parameters including the normal load, radii of curvature, surface velocities, and slide-to-roll ratio. The proposed EHL model is designed to continuously follow the contact of a tooth pair from the root to the tip to capture the transient characteristics of lubricated spur gear contacts due to these parameter variations, instead of analyzing the contact at discrete positions assuming time-invariant parameters. The normal tooth force along the line of action is predicted by using a gear load distribution formulation and the contact radii and tangential surface velocities are computed from the kinematics and geometry of involute profiles. A unified numerical approach is adapted for handling asperity interaction in mixed EHL conditions. The differences between the transient and discrete EHL analyses are shown for a spur gear pair having smooth surfaces and different tooth profile modifications. The transient behavior predicted by the proposed model is found to be mainly due to the squeezing and pumping effects caused by sudden load changes. The lubrication behavior under rough conditions is also investigated at different operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013200 [...]