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E N Naumovich - One of the best experts on this subject based on the ideXlab platform.
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Oxygen Permeability of perovskites in the system srcoo 3 δ srtio 3
Solid State Ionics, 1997Co-Authors: V V Kharton, Li Shuangbao, A V Kovalevsky, E N NaumovichAbstract:Abstract Existence of two concentration ranges of solid solutions with cubic perovskite-like structure has been ascertained in the SrCoO 3 − δ-SrTiO 3 system. It has been found that an increase in titanium concentration in SrCo 1 − xTi xO 3 − δ leads to a decrease in electrical conductivity and Oxygen Permeability of cubic solid solutions. Oxygen transfer through ceramics SrCo(Ti)O 3 − δ has been shown to be limited by the process of Oxygen exchange with gas phase. Application of platinum layers on the surface of cobaltites-titanates results in substantial buildup of Oxygen Permeability. Thermal expansion coefficients of the above oxide materials lie in the range 11 − 21 × 10 −6K −1.
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Oxygen Permeability of perovskites in the system SrCoO 3 − δ-SrTiO 3
Solid State Ionics, 1997Co-Authors: V V Kharton, Li Shuangbao, A V Kovalevsky, E N NaumovichAbstract:Abstract Existence of two concentration ranges of solid solutions with cubic perovskite-like structure has been ascertained in the SrCoO 3 − δ-SrTiO 3 system. It has been found that an increase in titanium concentration in SrCo 1 − xTi xO 3 − δ leads to a decrease in electrical conductivity and Oxygen Permeability of cubic solid solutions. Oxygen transfer through ceramics SrCo(Ti)O 3 − δ has been shown to be limited by the process of Oxygen exchange with gas phase. Application of platinum layers on the surface of cobaltites-titanates results in substantial buildup of Oxygen Permeability. Thermal expansion coefficients of the above oxide materials lie in the range 11 − 21 × 10 −6K −1.
A A Yaremchenko - One of the best experts on this subject based on the ideXlab platform.
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processing stability and Oxygen Permeability of sr fe al o3 based ceramic membranes
Journal of Membrane Science, 2005Co-Authors: V V Kharton, A L Shaula, Frans Snijkers, J F C Cooymans, Jan Luyten, A A Yaremchenko, Anabela A Valente, E V Tsipis, J R Frade, F M B MarquesAbstract:Abstract Minor additions of alumina into perovskite-type SrFe 0.7 Al 0.3 O 3− δ , a composition close to the solid solution formation limits in SrFe 1− x Al x O 3− δ system, result in decreasing thermal expansion and increasing Oxygen Permeability. The improved sinterability of SrFe 0.7 Al 0.3 O 3 -based composite with 3 wt.% Al 2 O 3 addition enables to fabricate high-quality tubular membranes for the methane conversion reactors. No essential degradation in the performance of SrFe 0.7 Al 0.3 O 3− δ membranes under air/CH 4 or air/H 2 H 2 O gradients at 973–1223 K was observed during 200–700 h. The stable operation under high Oxygen chemical potential gradients is possible due to surface-limited Oxygen transport, indicated by the dependencies of Oxygen Permeability on the membrane thickness. Applying porous layers of the same composition, synthesized via cellulose-precursor technique, onto the permeate-side surface leads to substantially higher Oxygen fluxes. For a model reactor with the surface-modified SrFe 0.7 Al 0.3 O 3− δ membrane and commercial Ni/Al 2 O 3 catalyst, the CH 4 conversion rate achieved 90–97% at 1073–1123 K, when the CO selectivity was almost 100%.
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p type electronic conductivity Oxygen Permeability and stability of la2ni0 9co0 1o4 δ
Journal of Materials Chemistry, 2003Co-Authors: A A Yaremchenko, V V Kharton, M V Patrakeev, J R FradeAbstract:The Oxygen Permeability, total conductivity and Seebeck coefficient of La2Ni0.9Co0.1O4+δ were studied in the Oxygen partial pressure range of 10−16 Pa to 50 kPa at 973–1223 K. The conductivity of La2Ni0.9Co0.1O4+δ is predominantly p-type electronic within the whole p(O2) range in which the K2NiF4-type structure exists. Thermally-activated mobility, the values of which are 0.02–0.08 cm2 V−1 s−1, and the p(O2) dependencies of electron-hole transport suggest a small-polaron conduction mechanism. Oxygen Permeability of dense La2Ni0.9Co0.1O4+δ membranes, with an apparent activation energy of 192 kJ mol−1 in oxidising conditions, is limited by both bulk ionic conductivity and the surface exchange rate. The role of surface processes in limiting permeation is also significant under air/H2–H2O gradients and increases with decreasing temperature. The stability boundary of the La2Ni0.9Co0.1O4+δ phase at low Oxygen pressures is similar to that of undoped lanthanum nickelate, which allows stable operation of nickelate membranes under high Oxygen chemical potential gradients, such as air/10% H2–90% N2, at 973 K. At temperatures above 1000 K, the decomposition products form blocking layers on the membrane surface causing degradation of the membrane performance with time. The average thermal expansion coefficient of La2Ni0.9Co0.1O4+δ ceramics, calculated from dilatometric data in air, is 12.8 × 10−6 K−1 at 400–1265 K.
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ceramic microstructure and Oxygen Permeability of srco fe m o 3 δ m cu or cr perovskite membranes
Journal of The Electrochemical Society, 1998Co-Authors: V V Kharton, Li Shuangbao, V N Tikhonovich, E N Naumovich, A V Kovalevsky, A P Viskup, I A Bashmakov, A A YaremchenkoAbstract:Stabilization of the cubic perovskite phase was demonstrated in the SrCo{sub 0.90{minus}x}Fe{sub 0.10}Cr{sub x}O{sub 3{minus}{delta}} oxide system at x {ge} 0.03. Oxygen Permeability of SrCo(Fe, Cr)O{sub 3{minus}{delta}} solid solutions was independent of chromium content at x = 0.01--0.05. It was found that reducing ceramic grain size dimensions resulted in decreasing thermal expansion, electrical conductivity, and Oxygen Permeability of SrCo(Fe, Cu)O{sub 3{minus}{delta}} ceramic membranes. Oxygen transport through SrCo(Fe, M)O{sub 3{minus}{delta}} ceramics was shown to be limited by both the bulk ionic conductivity and Oxygen exchange currents. The limiting effect of the membrane permeate-side surface on the permeation was higher in comparison with that on the feed-side surface.
Li Shuangbao - One of the best experts on this subject based on the ideXlab platform.
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ceramic microstructure and Oxygen Permeability of srco fe m o 3 δ m cu or cr perovskite membranes
Journal of The Electrochemical Society, 1998Co-Authors: V V Kharton, Li Shuangbao, V N Tikhonovich, E N Naumovich, A V Kovalevsky, A P Viskup, I A Bashmakov, A A YaremchenkoAbstract:Stabilization of the cubic perovskite phase was demonstrated in the SrCo{sub 0.90{minus}x}Fe{sub 0.10}Cr{sub x}O{sub 3{minus}{delta}} oxide system at x {ge} 0.03. Oxygen Permeability of SrCo(Fe, Cr)O{sub 3{minus}{delta}} solid solutions was independent of chromium content at x = 0.01--0.05. It was found that reducing ceramic grain size dimensions resulted in decreasing thermal expansion, electrical conductivity, and Oxygen Permeability of SrCo(Fe, Cu)O{sub 3{minus}{delta}} ceramic membranes. Oxygen transport through SrCo(Fe, M)O{sub 3{minus}{delta}} ceramics was shown to be limited by both the bulk ionic conductivity and Oxygen exchange currents. The limiting effect of the membrane permeate-side surface on the permeation was higher in comparison with that on the feed-side surface.
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Oxygen Permeability of perovskites in the system srcoo 3 δ srtio 3
Solid State Ionics, 1997Co-Authors: V V Kharton, Li Shuangbao, A V Kovalevsky, E N NaumovichAbstract:Abstract Existence of two concentration ranges of solid solutions with cubic perovskite-like structure has been ascertained in the SrCoO 3 − δ-SrTiO 3 system. It has been found that an increase in titanium concentration in SrCo 1 − xTi xO 3 − δ leads to a decrease in electrical conductivity and Oxygen Permeability of cubic solid solutions. Oxygen transfer through ceramics SrCo(Ti)O 3 − δ has been shown to be limited by the process of Oxygen exchange with gas phase. Application of platinum layers on the surface of cobaltites-titanates results in substantial buildup of Oxygen Permeability. Thermal expansion coefficients of the above oxide materials lie in the range 11 − 21 × 10 −6K −1.
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Oxygen Permeability of perovskites in the system SrCoO 3 − δ-SrTiO 3
Solid State Ionics, 1997Co-Authors: V V Kharton, Li Shuangbao, A V Kovalevsky, E N NaumovichAbstract:Abstract Existence of two concentration ranges of solid solutions with cubic perovskite-like structure has been ascertained in the SrCoO 3 − δ-SrTiO 3 system. It has been found that an increase in titanium concentration in SrCo 1 − xTi xO 3 − δ leads to a decrease in electrical conductivity and Oxygen Permeability of cubic solid solutions. Oxygen transfer through ceramics SrCo(Ti)O 3 − δ has been shown to be limited by the process of Oxygen exchange with gas phase. Application of platinum layers on the surface of cobaltites-titanates results in substantial buildup of Oxygen Permeability. Thermal expansion coefficients of the above oxide materials lie in the range 11 − 21 × 10 −6K −1.
V V Kharton - One of the best experts on this subject based on the ideXlab platform.
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processing stability and Oxygen Permeability of sr fe al o3 based ceramic membranes
Journal of Membrane Science, 2005Co-Authors: V V Kharton, A L Shaula, Frans Snijkers, J F C Cooymans, Jan Luyten, A A Yaremchenko, Anabela A Valente, E V Tsipis, J R Frade, F M B MarquesAbstract:Abstract Minor additions of alumina into perovskite-type SrFe 0.7 Al 0.3 O 3− δ , a composition close to the solid solution formation limits in SrFe 1− x Al x O 3− δ system, result in decreasing thermal expansion and increasing Oxygen Permeability. The improved sinterability of SrFe 0.7 Al 0.3 O 3 -based composite with 3 wt.% Al 2 O 3 addition enables to fabricate high-quality tubular membranes for the methane conversion reactors. No essential degradation in the performance of SrFe 0.7 Al 0.3 O 3− δ membranes under air/CH 4 or air/H 2 H 2 O gradients at 973–1223 K was observed during 200–700 h. The stable operation under high Oxygen chemical potential gradients is possible due to surface-limited Oxygen transport, indicated by the dependencies of Oxygen Permeability on the membrane thickness. Applying porous layers of the same composition, synthesized via cellulose-precursor technique, onto the permeate-side surface leads to substantially higher Oxygen fluxes. For a model reactor with the surface-modified SrFe 0.7 Al 0.3 O 3− δ membrane and commercial Ni/Al 2 O 3 catalyst, the CH 4 conversion rate achieved 90–97% at 1073–1123 K, when the CO selectivity was almost 100%.
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p type electronic conductivity Oxygen Permeability and stability of la2ni0 9co0 1o4 δ
Journal of Materials Chemistry, 2003Co-Authors: A A Yaremchenko, V V Kharton, M V Patrakeev, J R FradeAbstract:The Oxygen Permeability, total conductivity and Seebeck coefficient of La2Ni0.9Co0.1O4+δ were studied in the Oxygen partial pressure range of 10−16 Pa to 50 kPa at 973–1223 K. The conductivity of La2Ni0.9Co0.1O4+δ is predominantly p-type electronic within the whole p(O2) range in which the K2NiF4-type structure exists. Thermally-activated mobility, the values of which are 0.02–0.08 cm2 V−1 s−1, and the p(O2) dependencies of electron-hole transport suggest a small-polaron conduction mechanism. Oxygen Permeability of dense La2Ni0.9Co0.1O4+δ membranes, with an apparent activation energy of 192 kJ mol−1 in oxidising conditions, is limited by both bulk ionic conductivity and the surface exchange rate. The role of surface processes in limiting permeation is also significant under air/H2–H2O gradients and increases with decreasing temperature. The stability boundary of the La2Ni0.9Co0.1O4+δ phase at low Oxygen pressures is similar to that of undoped lanthanum nickelate, which allows stable operation of nickelate membranes under high Oxygen chemical potential gradients, such as air/10% H2–90% N2, at 973 K. At temperatures above 1000 K, the decomposition products form blocking layers on the membrane surface causing degradation of the membrane performance with time. The average thermal expansion coefficient of La2Ni0.9Co0.1O4+δ ceramics, calculated from dilatometric data in air, is 12.8 × 10−6 K−1 at 400–1265 K.
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ceramic microstructure and Oxygen Permeability of srco fe m o 3 δ m cu or cr perovskite membranes
Journal of The Electrochemical Society, 1998Co-Authors: V V Kharton, Li Shuangbao, V N Tikhonovich, E N Naumovich, A V Kovalevsky, A P Viskup, I A Bashmakov, A A YaremchenkoAbstract:Stabilization of the cubic perovskite phase was demonstrated in the SrCo{sub 0.90{minus}x}Fe{sub 0.10}Cr{sub x}O{sub 3{minus}{delta}} oxide system at x {ge} 0.03. Oxygen Permeability of SrCo(Fe, Cr)O{sub 3{minus}{delta}} solid solutions was independent of chromium content at x = 0.01--0.05. It was found that reducing ceramic grain size dimensions resulted in decreasing thermal expansion, electrical conductivity, and Oxygen Permeability of SrCo(Fe, Cu)O{sub 3{minus}{delta}} ceramic membranes. Oxygen transport through SrCo(Fe, M)O{sub 3{minus}{delta}} ceramics was shown to be limited by both the bulk ionic conductivity and Oxygen exchange currents. The limiting effect of the membrane permeate-side surface on the permeation was higher in comparison with that on the feed-side surface.
A J Burggraaf - One of the best experts on this subject based on the ideXlab platform.
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influence of order disorder transitions on Oxygen Permeability through selected nonstoichiometric perovskite type oxides
Solid State Ionics, 1993Co-Authors: H Kruidhof, Henricus J M Bouwmeester, Rene H E Van Doorn, A J BurggraafAbstract:New results on the Oxygen Permeability of perovskite-type oxides SrCo0.8B'0.2O3−σ (with B'=Cr, Fe, Co and Cu) and La0.6Sr0.4CoO3−δ are presented. The occurrence of order-disorder transitions at elevated temperatures (790–940°C) in these phases has been confirmed by DSC measurements and, in some cases, by X-ray powder diffraction of samples either slowly cooled or quenched from high temperature after annealing in different atmospheres. The Oxygen Permeability found upon exposing opposite sides of sealed disc specimens to a stream of air and of helium, respectively, increases sharply (between 5–6 orders of magnitude up to 0.3−3×10−7molcm−2s−1) at the onset of the transition from a low-temperature vacancy-ordered state to defec t perovskite, except for SrCo0.8Fe0.2O3−δ. In the latter case only a slight anomaly is found in the Arrhenius plot of th e Oxygen Permeability at ∼790°C. The comparatively high Oxygen flux through SrCo0.8Fe0.2O3−δ observed at intermediate tempe ratures is interpreted in terms of a two-phase mixture of a vacancy-ordered state and disordered perovskite, while above ∼790°C the sample is single-phase of defect perovskite structure.
