Showing papers by "Vladislav V. Kharton published in 2009"
TL;DR: In this paper, the performance of B2O3-containing diopside-based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC) was investigated.
61 citations
TL;DR: In this paper, the steady-state oxygen permeation through dense La2NiO4+δ ceramics, limited by both surface exchange and bulk ambipolar conduction, can be increased by deposition of porous layers onto the membrane surfaces.
52 citations
TL;DR: The structure of Ba4Nb2O9 has two basic polymorphs: a high-temperature γ phase, which represents an entirely new structure type; and a low-temperate α phase, a rare Sr4Ru2O 9 structure type as discussed by the authors.
Abstract: Ba4Nb2O9 is shown to have two basic polymorphs: a high-temperature γ phase, which represents an entirely new structure type; and a low-temperature α phase, which has the rare Sr4Ru2O9 structure type. The phases are separated by a reconstructive phase transition at ∼1370 K, the kinetics of which are sufficiently slow that the γ phase can easily be quenched to room temperature. Below ∼950 K, both α and γ phases absorb significant amounts of water. In the case of the γ phase, protons from absorbed water occupy ordered positions in the structure, giving rise to a stoichiometric phase γ-III-Ba4Nb2O9·1/3H2O at room temperature. γ-III-Ba4Nb2O9·1/3H2O partially dehydrates at ∼760 K to give another stoichiometric phase γ-II-Ba4Nb2O9·1/6H2O, which completely dehydrates at ∼950 K to γ-I-Ba4Nb2O9. The hydrated γ phases exhibit faster protonic and oxide ionic transport than the hydrated α phases because of the presence in the gamma phases of 2D layers containing Nb5+ cations with unusually low oxygen coordination numb...
38 citations
TL;DR: In this paper, the cathodic performance of selected mixed-conducting electrodes, including perovskite-type SrMn 0.95 Sr 0.6 Nb 0.1 O 3−−− δ, and Ruddlesden-Popper La 2 Ni 0.5 Cu 0.4 O 7−−
32 citations
TL;DR: Mossbauer spectroscopy of layered YBaCo 3.96 Fe 0.04 O 7+ δ ( δ = 0.02 and 0.80), where 1% cobalt is substituted with 57 Fe isotope, revealed no evidence of charge ordering at 4-293 K as discussed by the authors.
27 citations
TL;DR: In this paper, the authors present the design and part-load performance of a natural gas-fired oxy-combustion combined cycle power plant for CO2 capture, where the combustion chamber of a conventional gas turbine was replaced by a membrane reactor, making it possible to obtain a highly concentrated CO2 stream for long-term storage.
Abstract: This paper presents the design and part-load performance of a natural gas-fired oxy-combustion combined cycle power plant for CO2 capture. The combustion chamber of a conventional gas turbine was replaced by a membrane reactor, making it possible to obtain a highly concentrated CO2 stream for long-term storage. The focus was on power plant operation with a view to operational and material constraints of individual process components to ensure their proper performance and required lifetime. In this respect, the mixed-conducting membrane modules were of particular interest. Temperature as well as concentration limitations for CO2 and other chemical species narrowed the operating window. Other critical reactor components added further constraints. For part-load operation of the power plant, two load control strategies were analysed for the gas turbine operating at constant rotational speed. In the first load control strategy, variable guide vanes were used to manipulate the mass flow of air to the gas turbine compressor. This degree of freedom was used to control the turbine exit temperature. In the second control strategy, variable guide vanes were not used and the turbine exit temperature was allowed to vary. For both load control strategies, the mean solid-wall temperature of the membrane modules was maintained close to its design value, which led to improved stability. The load-control strategy using variable guide vanes was superior to the strategy without variable guide vanes due to higher combined cycle efficiencies and increased load-reduction capability. Moreover, the performance of the catalytic combustors in the membrane reactor, operating at near stoichiometric conditions, also improved as a result of increased oxygen concentrations at part-load operation. Relevant process components were based on spatially distributed conservation balances for energy, species, mass, and momentum. A stability diagram was incorporated into the membrane module model to investigate the risk of degradation. Performance maps were used for turbomachinery components.
19 citations
TL;DR: In this article, the authors used de-convolution of impedance spectra to identify changes in grain boundary properties, which can be used to tune preferential electronic conductivity at bulk or grain boundary level.
13 citations
TL;DR: In this paper, the Coulombic repulsion between the point defects and local lattice deformations near Al3+ results in hole displacement out of these layers when the content of vacant anion sites and/or aluminum is significant.
Abstract: Moderate Al3+ doping in Ruddlesden−Popper type Sr3LaFe3O10−δ leads to complete reconfiguration of the electronic sublattice. While oxygen vacancies, Fe4+, and substitutional cations all exhibit energetic affinity for the equatorial perovskite-like planes, the atomistic computer simulations showed that Coulombic repulsion between the point defects and local lattice deformations near Al3+ result in hole displacement out of these layers when the content of vacant anion sites and/or aluminum is significant. The Al3+ cations tend to form relatively stable aluminum−oxygen tetrahedra, which are energetically favorable for the central perovskite layers and distort neighboring polyhedra formed by iron. These effects and partial hole localization in the apical iron−oxygen polyhedra adjacent to Al3+ were confirmed by Mossbauer spectroscopy analysis of Sr3LaFe3−xAlxO10−δ (x = 0.3−0.6, δ = 0−1).
10 citations
07 Oct 2009
8 citations
TL;DR: The structure of Ba4Nb2O9 has two basic polymorphs: a high-temperature γ phase, which represents an entirely new structure type; and a low-temperate α phase, a rare Sr4Ru2O 9 structure type.
Abstract: Ba4Nb2O9 is shown to have two basic polymorphs: a high-temperature γ phase, which represents an entirely new structure type; and a low-temperature α phase, which has the rare Sr4Ru2O9 structure type. The phases are separated by a reconstructive phase transition at ∼1370 K, the kinetics of which are sufficiently slow that the γ phase can easily be quenched to room temperature. Below ∼950 K, both α and γ phases absorb significant amounts of water. In the case of the γ phase, protons from absorbed water occupy ordered positions in the structure, giving rise to a stoichiometric phase γ-III-Ba4Nb2O9·1/3H2O at room temperature. γ-III-Ba4Nb2O9·1/3H2O partially dehydrates at ∼760 K to give another stoichiometric phase γ-II-Ba4Nb2O9·1/6H2O, which completely dehydrates at ∼950 K to γ-I-Ba4Nb2O9. The hydrated γ phases exhibit faster protonic and oxide ionic transport than the hydrated α phases because of the presence in the gamma phases of 2D layers containing Nb5+ cations with unusually low oxygen coordination numb...
TL;DR: In this article, the authors used radio-frequency magnetron sputtering from an yttria-stabilized zirconia target to achieve deposition rates in the range 0.50-0.75 mm/h.
Book•
01 Jan 2009
TL;DR: A review of the current experimental data and their agreement with Theory Overview and Areas for Future Development can be found in this article, where the authors discuss the current state of the art in the field of solids.
Abstract: Preface FUNDAMENTALS, APPLICATIONS AND PERSPECTIVES OF SOLID STATE ELECTROCHEMISTRY - A SYNOPSIS Solid vs. Liquid State Thermodynamics and Kinetics of Charge Carriers Usefulness of Electrochemical Cells Materials Research Strategies: Bulk Defect Chemistry Materials Research Strategy: Boundary Defect Chemistry Nanoionics SUPERIONIC MATERIALS: STRUCTURAL ASPECTS Techniques Families of Superionic Conductors Current Status and Future Prospects DEFECT EQUILIBRIA IN SOLIDS AND RELATED PROPERTIES: AN INTRODUCTION Defect Structure of Solids: Thermodynamic Approach Basic Relationships between the Defect Equilibria and Charge Tranfer in Solids Examples of Functional Materials with Different Defect Structures ION-CONDUCTING NANOCRYSTALS: THEORY, METHODS AND APPLICATIONS Theoretical Aspects Applications and Perspectives Experimental Methods Review of the Current Experimental Data and their Agreement with Theory Overview and Areas for Future Development THE FUNDAMENTALS AND ADVANCES OF SOLID STATE ELECTROCHEMISTRY: INTERCALATION (INSERTION) AND DEINTERCALATAION (EXTRACTION) IN SOLID STATE ELECTRODES Thermodynamics of Intercalation and Deintercalation Kinetics of Intercalation and Deintercalation Methodological Overview SOLID STATE ELECTROCHEMICAL REACTIONS OF ELECTROACTIVE MICRO- AND NANOPARTICLES IN A LIQUID ELECTROLYTE ENVIRONMENT Methodological Aspects Theory Examples and Applications ALKALI METAL CATION AND PROTON CONDUCTORS: RELATIONSHIPS BETWEEN COMPOSITION, CRYSTAL STRUCTURE AND PROPERTIES Principles of Classification and General Comments Crystal-Chemistry Factors Affecting Cationic Conductivity Crystal Structural Screening and Studies of the Conduction Paths Conductors with Large Alkaline Ions Lithium Ion Conductors Proton Conductors CONDUCTING SOLIDS: IN THE SEARCH FOR MULTIVALENT CATION TRANSPORT Analysis of Trivalent Cation Transport Search for Tetravalent Cation Conductors OXYGEN ION-CONDUCTING MATERIALS Oxygen Ionic Transport in Acceptor-Doped Oxide Phases: Relevant Trends Stabilized Zirconia Electrolytes Doped Ceria Anion Conductors Based on Bi2O3 Transport Properties of Other Fluorite-Related Phases: Selected Examples Perovskite-Type LnBO3 (B=Ga,, Al, In, Sc, Y) and their Derivatives Perovskite-Related Mixed Conductors: A Short Overview La2Mo2O9-Based Electrolytes Solid Electrolytes with Apatite Structure POLYMER AND HYBRID MATERIALS, THEIR ELECTROCHEMISTRY AND APPLICATIONS Introduction Fundamentals Fluorinated Ionomer Membranes Non-Fluorinated Ionomer Membranes High Temperature PEMs Conclusion ELECTRONICALLY CONDUCTING POLYMERS Solid Organic and Inorganic Electrochemically Active Materials for Galvanic Cells Operating at Moderate Temperatures General Features of Doping-Induced Changes in Pi-Conjugated Polymers HIGH-TEMPERATURE APPLICATIONS OF SOLID ELECTROLYTES: GAS ANALYSIS, PUMPING AND CONVERSION Characteristics of a Current-Carrying Electrode on an Oxide Electrolyte Operating Modes Cell Materials Cell Designs Examples of Applications ELECTROCHEMICAL SENSORS: FUNDAMENTALS, KEY MATERIALS AND APPLICATIONS Operation Principles Materials Challenges Applications
TL;DR: In this article, a 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 is presented.
Abstract: 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.
TL;DR: In this article, minor additions of manganese oxide and cobalt oxide are both shown to be good sintering aids for Ce 08 Pr 02 O 2-δ, a promising ceramic membrane material with comparable values of partial oxygen-ionic and electronic conductivities, to offer dense ceramics with submicron grain sizes under 1150°C Transmission electron microscopy and X-ray energy dispersive spectroscopy suggest the transition-metal oxide addition to be located in the grain boundary regions.
Abstract: Minor additions of manganese oxide and cobalt oxide are both shown to be good sintering aids for Ce 08 Pr 02 O 2-δ , a promising ceramic membrane material with comparable values of partial oxygen-ionic and electronic conductivities, to offer dense ceramics with submicron grain sizes under 1150°C Transmission electron microscopy and X-ray energy dispersive spectroscopy suggest the transition-metal oxide addition to be located in the grain boundary regions The smallest grain size is observed in the case of materials with Mn additions Whereas the addition of cobalt oxide radically improves the transport properties of Ce 08 Pr 02 O 2-δ , boosting the level of electronic conductivity by two to three times and leaving the ionic conductivity intact, the addition of manganese oxide is shown to be detrimental, increasing the activation energy for ionic conductivity while offering no benefit to electronic conductivity These characteristic transport properties impact on levels of oxygen permeation The flux is significantly improved in the case of Co additions due to an increased ambipolar conductivity and improved oxygen surface kinetics, whereas no improvement in oxygen permeation flux is observed for Mn additions in comparison to the base composition Ce 08 Pr 02 O 2-δ It has been suggested that a very slight increase in solubility of the transition oxide addition in the grain bulk in the Mn-doped case may offer an explanation of the resultant properties