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Oxygen Permeation (oxygen + permeation)

Distribution by Scientific Domains
Chemistry66%
Polymers and Materials Science33%

Selected Abstracts

ChemInform Abstract: Hydrogen Production by Water Dissociation in Surface-Modified BaCoxFeyZr1-x-yO3-, Hollow-Fiber Membrane Reactor with Improved Oxygen Permeation.

CHEMINFORM, Issue 41 2010
Heqing Jiang
Abstract A BaCoxFeyZr1-x-yO3-, hollow-fiber membrane is surface modified by a catalytically active BaCoxFeyZr0.9-x-yPd0.1 O3-, porous layer. [source]

Lanthanum Chromite-Based Interconnects as Key Materials for SOFC Stack Development

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2004
Natsuko Sakai
The historical investigations on the physicochemical and transport properties of lanthanum chromite-based perovskite oxides are reviewed to evaluate the compatibility as interconnects in solid oxide fuel cells. These materials improve sinterability in air. This has led to investigations on other physicochemical properties of these materials, such as thermal expansion, mechanical strength, and chemical stability. Lanthanum and chromium ion can be substituted by alkaline earths or transition metals, and this translates into a large flexibility in physicochemical properties. However, the formation of oxygen vacancies in a reducing atmosphere can result in an undesirable isothermal expansion or oxygen permeation. The chemical stability of these materials is governed by the fast cation diffusion at the grain boundary of the polycrystals. [source]

Oxygen permeability and structural stability of a novel tantalum-doped perovskite BaCo0.7Fe0.2Ta0.1O3,,

AICHE JOURNAL, Issue 3 2010
Huixia Luo
Abstract Dense BaCo0.7Fe0.2Ta0.1O3,, (BCFT) perovskite membranes were successfully synthesized by a simple solid state reaction. In situ high-temperature X-ray diffraction indicated the good structure stability and phase reversibility of BCFT at high temperatures. The thermal expansion coefficient (TEC) of BCFT was determined to amount 1.02 × 10,5 K,1, which is smaller than those of Ba0.5Sr0.5Co0.8Fe0.2O3,, (BSCF) (1.15 × 10,5 K,1), SrCo0.8Fe0.2O3,, (SCF) (1.79 × 10,5 K,1), and BaCo0.4Fe0.4Zr0.2O3,, (BCFZ) (1.03 × 10,5 K,1). It can be seen that the introduction of Ta ions into the perovskite framework could effectively lower the TEC. Thickness dependence studies of oxygen permeation through the BCFT membrane indicated that the oxygen permeation process was controlled by bulk diffusion. A membrane reactor made from BCFT was successfully operated for the partial oxidation of methane to syngas at 900°C for 400 h without failure and with the relatively high, stable oxygen permeation flux of about 16.8 ml/min cm2. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Evaluation of mixed-conducting lanthanum-strontium-cobaltite ceramic membrane for oxygen separation

AICHE JOURNAL, Issue 10 2009
Lei Ge
Abstract In this study, La0.4Sr0.6CoO3-, (LSC) oxide was synthesized via an EDTA-citrate complexing process and its application as a mixed-conducting ceramic membrane for oxygen separation was systematically investigated. The phase structure of the powder and microstructure of the membrane were characterized by XRD and SEM, respectively. The optimum condition for membrane sintering was developed based on SEM and four-probe DC electrical conductivity characterizations. The oxygen permeation fluxes at various temperatures and oxygen partial pressure gradients were measured by gas chromatography method. Fundamental equations of oxygen permeation and transport resistance through mixed conducting membrane were developed. The oxygen bulk diffusion coefficient (Dv) and surface exchange coefficient (Kex) for LSC membrane were derived by model regression. The importance of surface exchange kinetics at each side of the membrane on oxygen permeation flux under different oxygen partial pressure gradients and temperatures were quantitatively distinguished from the oxygen bulk diffusion. The maximum oxygen flux achieved based on 1.6-mm-thick La0.4Sr0.6CoO3-, membrane was ,4.0 × 10,7 mol cm,2 s,1at 950°C. However, calculation results show theoretical oxygen fluxes as high as 2.98 × 10,5 mol cm,2 s,1 through a 5-,m-thick LSC membrane with ideal surface modification when operating at 950°C for air separation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Effect of pH on synthesis and properties of perovskite oxide via a citrate process

AICHE JOURNAL, Issue 2 2006
Zhentao Wu
Abstract A series of La0.6Sr0.4Co0.4Fe0.6O3-, (LSCF) perovskite-type oxides were synthesized using a modified citrate process under various pH conditions (pH =1, 3, 5, 7, and 9, respectively). The effect of pH on the chelate process, crystal development, morphology, and oxygen permeability of LSCF oxides were investigated. FT-IR analysis showed that the chelate processes for pH = 1 and 3 were different from those for pH = 5, 7, and 9. XRD and SEM observations revealed that the crystal formation and morphology of LSCF oxides were dependent on the precursors with different pH conditions. The LSCF membranes derived from the precursors with lower pH values (pH = 1 and 3) exhibited larger apparent activation energy for oxygen permeation than the other samples (pH = 5, 7, and 9) in the range of 1073-1123K. This study indicated that properties such as crystallinity and oxygen permeability of LSCF oxide could be tailored by controlling the pH values in the synthesis process. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]

PVC nanocomposites,Nanoclay chemistry and performance,

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2008
Daphne Benderly
Nanoclay applications in poly(vinyl chloride) (PVC) have been limited, as the organic modifier of conventional nanoclays can promote PVC degradation. Novel nanoclays designed for enhanced PVC compatibility were compounded with PVC. Hectorite and bentonite clays were studied as nanoclay fillers. Two incorporation methods were evaluated to determine the effect on nanoclay dispersion and composite performance. A two-stage method, in which the nanoclay was predispersed in plasticizer, resulted in good nanoclay dispersion at both the micrometer and nanometer scales. The nanocomposites were characterized by using a wide range of analytical tools. They exhibited significantly improved heat stability, an increase of up to 200% in storage modulus, and a decrease of up to 77% in oxygen permeation, as compared to unfilled PVC. Bentonite nanoclays provided a greater increase in barrier and mechanical properties. No change was seen in the PVC glass transition temperature. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers [source]