共查询到20条相似文献,搜索用时 0 毫秒
1.
A. Abrutis A. Teiserskis G. Garcia V. Kubilius Z. Saltyte Z. Salciunas V. Faucheux A. Figueras S. Rushworth 《Journal of membrane science》2004,240(1-2):113-122
Dense ceramic mixed ionic and electronic conducting membranes have been deposited by atmospheric spray-pyrolysis technique onto porous ceramic substrates. Perovskite oxide layers, i.e. manganites La1−xSrxMnO3, ferrites La1−xSrxFe1−y(Co,Ni)yO3, gallates La1−xSrxGa1−y(Co,Ni,Fe)yO3, cobaltites La1−xSrxCoO3 and related perovskites such as lanthanum nickelate La2NiO4 layers have been prepared. The structure, morphology and composition of the layers were characterised by XRD, SEM and WDS, respectively. Density and gas tightness of the layers were studied as a function of deposition process parameters, film thickness (from 0.5 to 3 μm) and preparation procedure. The presence of cracks and defects due to thermo-mechanical stresses applied during or after the preparation process were correlated with the membrane composition and the corresponding thermal expansion coefficient differences between substrates and membranes. 相似文献
2.
Zhihao Chen Zongping Shao Ran Ran Wei Zhou Pingying Zeng Shaomin Liu 《Journal of membrane science》2007,300(1-2):182-190
A configuration of dense mixed ionic and electronic conducting (MIEC) membrane with layered morphological structure for oxygen separation, which combines the benefits of high oxygen permeation flux of cobalt-based membrane, high chemical stability of iron-based perovskite and high mechanical strength of thick membrane, was studied. The membrane is normally composed of two layers; each layer is a dense MIEC oxide. The substrate layer is a thick dense membrane with high oxygen permeability but relatively lower chemical stability. The feasibility of dense thick Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF5582) membrane as the substrate layer and Ba0.5Sr0.5Co0.2Fe0.8O3−δ (BSCF5528) as the thin-film layer was mainly experimentally investigated. Both the BSCF5582 and the BSCF5528 show the same cubic perovskite structure and the similar lattice constant with no detrimental reaction products formed. By optimizing fabrication parameters of a simple dry pressing process, dual-layered membrane, free of cracks, was successfully fabricated. The oxygen permeation flux of a dual-layered membrane with the thin-film BSCF5528 layer facing to the sweep gas reached 2.1 mL cm−2 min−1 [STP] (1.56 × 10−6 mol cm−2 s−1) at 900 °C, which is about 3.5 times higher than that of the BSCF5528 membrane (0.6 mL cm−2 min−1, [STP] (4.46 × 10−7 mol cm−2 s−1) under the same conditions. 相似文献
3.
Yunfei Cheng Hailei Zhao Deqiang Teng Fushen Li Xionggang Lu Weizhong Ding 《Journal of membrane science》2008
BaCo0.7Fe0.3−xNbxO3−δ (BCFN, x = 0–0.2) were prepared by the conventional solid state reaction process. The crystal structure, electrical conductivity and oxygen desorption property were studied by X-ray diffraction (XRD), different thermal analysis (DTA), four-terminal direct current conductivity and oxygen temperature programmed desorption (O2-TPD), respectively. At x = 0.08–0.20, BCFN have a cubic perovskite structure, while it exhibits the hexagonal structure for x = 0.00 and the mixed phases of cubic perovskite with trace amount of hexagonal for x = 0.05. BCFN shows good structure stability in 5%H2 + Ar reducing atmosphere, and it is enhanced with the increased Nb-doping content. The electrical conductivity of BCFN increases with increasing temperature and decreases with the Nb substitution content for iron. BCFN exhibits a p-type semiconductor and obeys the thermally activated small polarons hopping mechanism. The oxygen fluxes increase with the working temperature and the COG flow rate, but decrease with increasing Nb content. The flux of BCFN (x = 0.08) with 1.0 mm thickness membrane reaches 25.77 ml min−1 cm−2 at 875 °C, higher than most of the reported materials. 相似文献
4.
A. L. Shaula V. V. Kharton F. M. B. Marques A. V. Kovalevsky A. P. Viskup E. N. Naumovich 《Journal of Solid State Electrochemistry》2006,10(1):28-40
Composite ceramic membranes, based on selected combinations of ionic conductors ((La0.9Sr0.1)0.98Ga0.8Mg0.2O3-δ—LSGM or Ce0.8Gd0.2O2-δ—CGO) and electronic/mixed conductors (La2Ni0.8Cu0.2O4+δ—LNC, La0.8Sr0.2Fe0.8Co0.2O3-δ—LSFC, La0.7Sr0.3MnO3-δ—LSM, and SrCoO3-δ – Sr2Fe3O6.5±δ—SCSF), were processed and characterized aiming at the identification of key features to be considered in the design and optimization of materials performance as mixed conductors. Although after almost complete reaction between constituents, the best permeability was observed for the LSGM/LSFC combination processed under moderate firing conditions. Ceria-based composites, while preserving a typical composite microstructure, and suffering small compositional changes due to interaction between constituents, behaved always below the result of an ideal combination of the best characteristics of the individual components. Materials interaction, from modest compositional changes to formation of new phases, with deep changes in nominal composition, can be understood both as a challenge requiring proper identification of ideal processing conditions for phase preservation, but also as an opportunity for the development of entirely new composites and materials with compositional heterogeneities at grain size level. 相似文献
5.
A dense perovskite hollow fiber made of BaCoxFeyZrzO3−δ (BCFZ) was evaluated for the oxygen separation at low temperatures (400–500 °C). An oxygen permeation flux of 0.45 ml/min cm2 was obtained at 500 °C, which is the first oxygen permeation data reported at such low temperature so far. A degradation of the oxygen permeation at 500 °C was observed, but the oxygen fluxes through the hollow fiber membrane can be regenerated by thermal treatment at 925 °C for 1 h in air. Energy-dispersive X-ray spectroscopy (EDXS) shows that a strong element segregation occurs in the membrane during operation at low temperature. 相似文献
6.
Ming Ya Cai Hui Xia Luo Zhong Li Armin Feldhoff Jiirgen Caro Hai Hui Wang 《中国化学快报》2008,19(10):1256-1259
Dense mixed proton and electron conducting membrane made of BaCe0.95Nd0.05O3-δ (BCNd5) was prepared by pressing followed by sintering. X-ray diffraction (XRD) was used to characterize the phase structure of both the powder and the sintered membranes. The microstructure of the sintered membranes was studied by scanning electron microscopy (SEM). Hydrogen permeation through the BCNd5 membrane was studied using a high temperature permeator. The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions, which is due to H^+ hopping via surface OH groups. At 925℃, a hydrogen permeation flux of 0.02 mL/min cm^2 was obtained under wet condition, which recommends BCNd5 as a potential material for hydrogen-selective membranes. 相似文献
7.
In this work we address the optimization of mixed conductivity in fluorite compounds based on zirconia. Phase relations of the new systems YbO1.5-NbO2.5-ZrO2, and CaO-NbO2.5-ZrO2 are presented. The limit of the cubic defect fluorite phase in YbO1.5-NbO2.5-ZrO2 closely resembles that of the system YO1.5-NbO2.5-ZrO2, whilst in CaO-NbO2.5-ZrO2 is narrow extending to include composition Ca0.255Nb0.15Zr0.595O1.82 at 1500°C. The influence of dopant ion size, charge and composition on ionic conduction is assessed and parallels are drawn with the systems YO1.5-NbO2.5-ZrO2 and YO1.5-TiO2-ZrO2. Comparison of these results with published data on the Ti containing systems CaO-TiO2-ZrO2, GdO1.5-TiO2-ZrO2 shows that the highest mixed conducting compositions can only be offered in the system YO1.5-TiO2-ZrO2 out of all the systems here studied. 相似文献
8.
Jürgen Caro 《中国化学快报》2009,20(2):250-252
A novel cobalt-free perovskite based on Ba_(0.5)Sr_(0.5)Fe_(0.8)Zn_(0.2)O_(3-δ)(BSFZ)were prepared by EDTA-citric acid method.The lattice constants of the BSFZ perovskite were characterized by in situ high-temperature X-ray diffraction(HTXRD).The thermal expansion coefficient of BSFZ is 10.5×10~(-6)K~(-1),which is lower than that of cobalt-based perovskite materials.The BSFZ membrane was also used to construct reactors for the partial oxidation of methane(POM)to syngas.Results show that the BSFZ membrane... 相似文献
9.
Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O3−δ were prepared by solid-state reaction method. The crystal
structure, oxygen nonstoichiometry, and phase stability of the materials were studied by TGA and XRD. Oxygen permeation fluxes through
these membranes were studied at operating temperature ranging from 750 to 950 ℃. Results showed that doping Cu in SrFeO3−δ compound
had a significant effect on the formation of single-phased perovskite structure. For SrFe1−xCuxO3−δ series materials, the oxygen nonstoichiometry
and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1–0.3). The sintering property
of the membrane decreased significantly when the Cu substitution amount reached 40%. SrFe0.7Cu0.3O3−δ showed high oxygen permeation
flux, but SrCuO2 and Sr2Fe2O5 phases formed in the compound after oxygen permeation test induced cracks in the membrane. 相似文献
10.
Da-Xin Wang Xiao-Lin Wang Yasuhiro Tomi Masaaki Ando Takuji Shintani 《Journal of membrane science》2006,280(1-2):734-743
A new model is proposed to evaluate the separation performance of nanofiltration (NF) membranes for the mixed salts solution. In the model, the observed transmission of an ion through a NF membrane is applied to express the separation performance of the membrane for the ion in the mixed salts solution, which has a relationship with the total concentration, the equivalent fraction and the species of each ion in the mixed salts solution. The verification of the model was carried out in the permeation experiments of some mixed salts solutions ((1) Na+, Cl− and F−; (2) Na+, K+ and Cl−; (3) Na+, F−, Cl− and NO3−; (4) Na+, Cl−, NO3− and SO42−) through three commercial NF membranes (ESNA 1-LF, ESNA 1 and LES 90). According to the permeation experiments of three NF membranes for some binary salts solutions, the competition coefficients of ions were obtained. The model evaluation results agreed quite well with the experimental data. Finally, the model was applied to evaluate the observed transmission of each ion in the mixed salts solution (Na+, F−, Cl−, NO3− and SO42−) through three NF membranes. The agreement between the model evaluation results and the experimental data indicated that the model is suitable for evaluating the separation performance of three NF membranes for the mixed salts solution. 相似文献
11.
Mingya Cai Song Liu Konstantin Efimov Jürgen Caro Armin Feldhoff Haihui Wang 《Journal of membrane science》2009,343(1-2):90-96
A mixed proton–electron conducting perovskite made of BaCe0.95Nd0.05O3−δ (BCN) was prepared by EDTA/citric acid complexing method. The precursor was characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray diffraction (XRD). In order to learn the perovskite formation process during the calcination, the intermediate, i.e. the sample calcined at 750 °C for 5 h, was investigated by scanning (STEM), energy-filtered (EFTEM), and high-resolution transmission electron microscopy (HRTEM) as well as electron energy-loss spectroscopy (EELS). The results revealed that the perovskite structure was formed via a solid-state reaction between barium–cerium mixed carbonate and cerium–neodymium mixed oxide particles. Dense mixed proton–electron conducting BCN membranes were made by pressing BCN powder followed by sintering. The microstructure of the sintered membranes was investigated by scanning electron microscopy (SEM). Hydrogen permeation through the BCN membrane was studied using a high-temperature permeator. The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions, which is due to increased proton concentrations in the H+ hopping via OH groups. The hydrogen permeation increased with increasing hydrogen and steam concentrations in the feed. For a steam concentration of 15 vol.%, the hydrogen permeation flux reaches 0.026 ml/min cm2. 相似文献
12.
Vladislav V. Kharton Joao C. Waerenborgh Sergey O. Yakovlev Piotr Gaczyński Aleksey A. Yaremchenko Victor V. Samakhval 《Journal of solid state chemistry》2006,179(4):1273-1284
Aluminum incorporation in the rhombohedrally distorted perovskite lattice of (La0.5Sr0.5)1−xFe1−yAlyO3−δ (x=0-0.05, y=0-0.30) decreases the unit cell volume and partial ionic and p-type electronic conductivities, while the oxygen nonstoichiometry and thermal expansion at 900-1200 K increase on doping. The creation of A-site cation vacancies has an opposite effect on the transport properties of Al-substituted ceramics. The maximum A-site deficiency tolerated by the (La,Sr)(Fe,Al)O3−δ structure is however limited, close to 3-4%. The Mössbauer spectroscopy revealed progressive localization of electron holes and a mixed charge-compensation mechanism, which results in higher average oxidation state of iron when Al3+ concentration increases. The average thermal expansion coefficients of (La0.5Sr0.5)1−xFe1−yAlyO3−δ are (12.2-13.0)×10−6 K−1 at 300-900 K and (20.1-30.0)×10−6 K−1 at 900-1200 K in air. The steady-state oxygen permeability (OP) of dense Al-containing membranes is determined mainly by the bulk ionic conductivity. The ion transference numbers at 973-1223 K in air, calculated from the oxygen permeation and faradaic efficiency (FE) data, vary in the range 1×10−4-3×10−3, increasing with temperature. 相似文献
13.
Mixed matrix membranes (MMMs) have received worldwide attention for natural gas purification due to their superior performance in terms of permeability and selectivity. The zeolitic imidazole framework-8 (ZIF-8) blended polysulfone (PSf) membranes have been fabricated for natural gas purification. ZIF-8 was selected due to its low cost, remarkable thermal and chemical stabilities, and tunable microporous structure. The neat PSf hollow fiber membrane and mixed matrix hollow fiber membranes incorporated with the various ZIF-8 loadings up to 1.25% were fabricated. The prepared membranes were evaluated using field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and gas separation performance. The low loading of ZIF-8 nanoparticles to the MMM improved thermal stability and glass transition temperature and yielded low surface roughness. MMMs were tested using pure gases with a significant improvement of 36% in CO2 permeability and 28% in CO2/CH4 selectivity compared to the neat membrane. However, the high ZIF-8 loading reduced the separation performances. Moreover, CO2/CH4 selectivity decreased at elevated pressure (8 and 10 bar) due to CO2-induced plasticization. Previously, the incorporation of ZIF-8 particles has primarily been subjected to the fabrication of flat sheet membranes, whereas this work focused on hollow fiber membranes which are rarely investigated. Hence, the promising results obtained at low feed pressure in this study demonstrated the potential of ZIF-8 based hollow fiber membrane for natural gas purification. 相似文献
14.
Grayson P. Dennis Kathryn E. O'Harra Irshad Kammakakam Tristin A. Jones Max S. Mittenthal Brian S. Flowers Yi Tuan Enrique M. Jackson Jason E. Bara 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2664-2674
Polyimides (PI) synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with various diamines have been frequently studied as gas separation membranes. The use of 6FDA in polyimides creates a bent structure than can increase fractional free volume (FFV) and gas permeability. Here, we demonstrate that 6FDA is also a useful building block for PI-ionene materials, which contain cations directly within the polymer backbone. These new 6FDA-containing PI-ionenes were combined with several different imidazolium ionic liquids (ILs) to form thin membranes. The thermal properties of all the derivatives were investigated to determine the relationship between regiochemistry and degradation as well as the intermolecular forces that are present within these structures. The gas separation properties of these 6FDA-containing PI-ionene + IL materials were investigated, showing modest CO2 permeabilities similar to other polyimide-ionenes and CO2/CH4 and CO2/N2 permselectivities that were relatively higher than other polyimide-ionenes. 相似文献
15.
Ekaterina V. Tsipis Vladislav V. Kharton 《Journal of Solid State Electrochemistry》2008,12(9):1039-1060
This work is focused on the comparative analysis of electrochemical and transport properties in the major families of cathode
and anode compositions for intermediate-temperature solid oxide fuel cells (SOFCs) and materials science-related factors affecting
electrode performance. The first part presents a brief overview of the electrochemical and chemical reactions in SOFCs, specific
rate-determining steps of the electrode processes, solid oxide electrolyte ceramics, and effects of partial oxygen ionic and
electronic conductivities in the SOFC components. The aspects associated with materials compatibility, thermal expansion,
stability, and electrocatalytic behavior are also briefly discussed. Primary attention is centered on the experimental data
and approaches reported during the last 10–15 years, reflecting the main challenges in the field of materials development
for the ceramic fuel cells. 相似文献
16.
Jason E. Bara Christopher J. Gabriel Evan S. Hatakeyama Trevor K. Carlisle Sonja Lessmann Richard D. Noble Douglas L. Gin 《Journal of membrane science》2008
Solid, polymer membranes fabricated from room-temperature ionic liquid monomers containing oligo(ethylene glycol) or nitrile-terminated alkyl substituents tethered to imidazolium cations were found to exhibit ideal CO2/N2 and CO2/CH4 separation factors significantly greater than those with comparable length n-alkyl substituents, with similar CO2 permeability. Polymers containing these functional groups exhibited CO2/N2 gas separation performance exceeding the “upper bound” of a “Robeson Plot”. 相似文献
17.
V.V. Kharton E.V. Tsipis A. Thursfield V.A. Kolotygin I.S. Metcalfe 《Journal of solid state chemistry》2008,181(6):1425-1433
The total conductivity and Seebeck coefficient of La2Ni0.9Fe0.1O4+δ with K2NiF4-type structure, studied in the oxygen partial pressure range from 10−5 to 0.5 atm at 973-1223 K, were analyzed in combination with the steady-state oxygen permeability, oxygen non-stoichiometry and Mössbauer spectroscopy data in order to examine the electronic and ionic transport mechanisms. Doping of La2NiO4+δ with iron was found to promote hole localization on nickel cations due to the formation of stable Fe3+ states, although the electrical properties dominated by p-type electronic conduction under oxidizing conditions exhibit trends typical for both itinerant and localized behavior of the electronic sublattice. The segregation of metallic Ni on reduction, which occurs at oxygen chemical potentials close to the low-p(O2) stability boundary of undoped lanthanum nickelate, is responsible for the high catalytic activity towards partial oxidation of methane by the lattice oxygen of La2Ni0.9Fe0.1O4+δ as revealed by thermogravimetry and temperature-programmed reduction in dry CH4-He flow at 573-1173 K. A model for the oxygen permeation fluxes through dense La2Ni0.9Fe0.1O4+δ ceramics, limited by both bulk ionic conduction and surface exchange kinetics, was proposed and validated. 相似文献
18.
David Uhlmann Shaomin Liu Bradley P. Ladewig João C. Diniz da Costa 《Journal of membrane science》2009
Cobalt-doped silica membranes were synthesized using tetraethyl orthosilicate-derived sol mixed with cobalt nitrate hexahydrate. The cobalt-doped silica structural characterization showed the formation of crystalline Co3O4 and silanol groups upon calcination. The metal oxide phase was sequentially reduced at high temperature in rich hydrogen atmosphere resulting in the production of high quality membranes. The cobalt concentration was almost constant throughout the film depth, though the silica to cobalt ratio changed from 33:1 at the surface to 7:1 at the interface with the alumina layer. It is possible that cobalt has more affinity to alumina, thus forming CoOAl2O3. The He/N2 selectivities reached 350 and 570 at 160 °C for dry and 100 °C wet gas testing, respectively. Subsequent exposure to water vapour, the membranes was regenerated under dry gas condition and He/N2 selectivities significantly improved to 1100. The permeation of gases generally followed a temperature dependency flux or activated transport, with best helium permeation and activation energy results of 9.5 × 10−8 mol m−2 s−1 Pa−1 and 15 kJ mol−1. Exposure of the membranes to water vapour led to a reduction in the permeation of nitrogen, attributed to water adsorption and structural changes of the silica matrix. However, the overall integrity of the cobalt-doped silica membrane was retained, given an indication that cobalt was able to counteract to some extent the effect of water on the silica matrix. These results show the potential for metal doping to create membranes suited for industrial gas separation. 相似文献
19.
Sunho Choi Joaquin Coronas Zhiping Lai David Yust Frank Onorato Michael Tsapatsis 《Journal of membrane science》2008,316(1-2):145-152
Composites of polybenzimidazole (PBI) with proton-exchanged AMH-3 and swollen AMH-3 were prepared, characterized by electron microscopy and X-ray scattering and tested for hydrogen/carbon dioxide ideal selectivity. Proton-exchanged AMH-3 was prepared under mild conditions by the ion exchange of Sr and Na cations in the original AMH-3 using aqueous solution of dl-histidine. Swollen AMH-3 was prepared by sequential intercalation of dodecylamine following the ion exchange in the presence of dl-histidine. Both silicate materials were introduced into a continuous phase of PBI as a selective phase. Mixed matrix nanocomposite membranes, prepared under certain casting conditions, with only 3 wt% of swollen AMH-3 present substantial increase of hydrogen/carbon dioxide ideal selectivity at 35 °C, i.e., more than by a factor of 2 compared to pure PBI membranes (40 vs. 15). Similar ideal selectivity was observed using higher loadings (e.g., 14%) of proton-exchanged AMH-3 particles suggesting that transport of hydrogen is faster than carbon dioxide in AMH-3-derived silicates. However, the ideal selectivity of mixed matrix membranes approaches that of pure polymer as the operating temperature increases to 100 °C and 200 °C. The composite membranes with AMH-3-derived materials were compared with MCM-22/PBI membranes. Composite membranes incorporating MCM-22 plate-like crystals show no selectivity enhancements possibly due to the presence of larger pores in MCM-22. 相似文献
20.
Vladislav V. Kharton Evgeny N. Naumovich Alim A. Vecher 《Journal of Solid State Electrochemistry》1999,3(2):61-81
Developments of solid electrolytes and mixed conductors based on stabilized zirconia in the former Soviet Union are reviewed.
Primary attention is given to experimental data on high-conducting electrolytes, mixed conductors obtained by doping zirconia
with transition metal oxides, oxygen exchange and oxygen permeation processes, as well as properties of metal electrodes in
contact with the stabilized zirconia.
Received: 26 March 1998 / Accepted: 4 June 1998 相似文献