Valery V. Belousov

The Oxygen Permeation of Solid/Melt Composite BiVO4 – 10 wt % V2O5 Membrane

The oxygen permeation fluxes through solid/melt composite BiVO 4 ― 10 wt % V 2 O 5 membrane have been measured by using the conventional gas flow technique in the temperature range 650―670°C under various oxygen partial pressure gradients. Results indicate that in the range of thickness 0.9―3.5 mm used in the present study, the membrane operates under mixed control of the bulk diffusion and surface exchange kinetics. The ambipolar conductivity, characteristic thickness, and surface exchange coefficient are estimated at values of about 2.8 x 10 ―3 S/cm, 0.5 mm, and 5.2 x 10 ―6 cm/s, respectively, at 650°C.

Transport Properties of BiVO4 – V2O5 Liquid-Channel Grain-Boundary Structures

Mixed-conducting BiVO 4 -5, 7, 10, 12 wt % V 2 O 5 liquid-channel grain-boundary structures were studied with respect to their electrochemical properties. The electrical conductivity and oxygen-ion transference number, measured by the four-probe dc and volumetric measurements of the faradaic efficiency techniques in the temperature range of 640-660°C, vary from 5 X 10 -3 to 3 × 10 -2 Ω -1 cm -1 and from 0.68 to 0.85, respectively. The apparent conductivity activation energy decreases from 0.86 to 0.56 eV with increasing content of V 2 O 5 .

Electrical and mass transport processes in molten oxide membranes

A review of the transport properties of molten oxide membranes (MOMs) is given. The MOMs are a new type of mixed-conducting membranes for oxygen separation from air. The rapidly expanding field of ion transport membranes is driven by a growing number of potential applications (fuel cells, membrane reactors, oxygen separators, sensors, etc.). Special attention is paid to the oxygen ion transport in MOM. The oxygen permeation kinetics and thermodynamics of MOM are considered. A dynamic polymer chain model for oxygen ion transport in molten oxides is analyzed. Prospects of MOM for oxygen technology are discussed.

Novel Molten Oxide Membrane for Ultrahigh Purity Oxygen Separation from Air.

We present a novel solid/liquid Co3O4-36 wt % Bi2O3 composite that can be used as molten oxide membrane, MOM ( Belousov, V. V. Electrical and Mass Transport Processes in Molten Oxide Membranes. Ionics 22 , 2016 , 451 - 469 ), for ultrahigh purity oxygen separation from air. This membrane material consists of Co3O4 solid grains and intergranular liquid channels (mainly molten Bi2O3). The solid grains conduct electrons, and the intergranular liquid channels predominantly conduct oxygen ions. The liquid channels also provide the membrane material gas tightness and ductility. This last property allows us to deal successfully with the problem of thermal incompatibility. Oxygen and nitrogen permeation fluxes, oxygen ion transport number, and conductivity of the composite were measured by the gas flow, volumetric measurements of the faradaic efficiency, and four-probe dc techniques, accordingly. The membrane material showed the highest oxygen selectivity jO2/jN2 > 10(5) and sufficient oxygen permeability 2.5 × 10(-8) mol cm(-1) s(-1) at 850 °C. In the range of membrane thicknesses 1.5-3.3 mm, the oxygen permeation rate was controlled by chemical diffusion. The ease of the MOM fabrication, combined with superior oxygen selectivity and competitive oxygen permeability, shows the promise of the membrane material for ultrahigh purity oxygen separation from air.

Catastrophic Oxidation of Copper: A Brief Review

A brief review of the current understanding of copper accelerated oxidation in the presence of low-melting oxides (Bi2O3, MoO3, and V2O5) is given. Special attention is paid to the kinetics, thermodynamics, and mechanisms of accelerated oxidation of copper. The mechanisms of two stages (fast and superfast) of the copper accelerated oxidation are considered. It is shown that the fast oxidation of copper occurs by a diffusion mechanism. Oxygen diffusion along the liquid channels in the oxide scale is the rate-limiting step in the overall mechanism. The superfast oxidation of copper occurs by a fluxing mechanism. Realization of the particular mechanism depends on the mass ratio of low-melting oxide to the metal. The mass ratios of low-melting oxide to the metal and the oxygen partial pressures for superfast oxidation of copper are established. A model of the fast oxidation of copper is discussed.

Modeling oxygen Ion transport of molten oxide membranes based on V2O5

A polymer model for oxygen ion transport in molten oxide membranes (MOM) based on V2O5 was developed. The model adapts Wagner’s theory for molten oxides and provides an interpretation of oxygen mobility in the oxide melts. Within the framework of this model, the values of oxygen permeation fluxes through the MOM were calculated and compared with experimental data. The calculated and experimental values are of the same order of magnitude which shows an adequacy of the model. A dynamic polymer chain concept is proposed. It is shown that the transference of oxygen ions in the oxide melts may occur by a mechanism of “connection–disconnection” of the polymer chains.

Oxygen Transport in Melts Based on V2O5

An oxygen ion transport model was developed for oxide melts based on V2O5. Within the framework of this model, the values of the parabolic rate constant of catastrophic oxidation of V2O5-deposited copper and the oxygen flux through the slags based on molten V2O5 were calculated and compared with experimental data. The calculated and experimental values are of the same order of magnitude which shows an adequacy of the model.

An Oxygen-Permeable Bilayer MIEC-Redox Membrane Concept

Mixed ionic-electronic conducting (MIEC) membranes attract the attention because of their high potential for oxygen separation and energy conversion applications. The different fabrication methods of asymmetric membranes consisting of a thin MIEC layer on porous support were developed. The basically dense but not completely hermetic thin layers were achieved. To overcome this problem, we suggest a new concept of bilayer MIEC-Redox membrane. This solid/liquid composite membrane consists of a gastight MIEC thin external layer and a thick internal layer in which the redox reactions and oxygen bubbling occur. Here, we report the transport properties of a copper oxide-based MIEC-Redox membrane.

New Generation Molten Oxide Energy Materials R&D

Energy technologies and their supporting materials are crucial in the context of the global challenges facing our present civilization. A great many opportunities remain, particularly for energy vector in relation to the molten oxides. Thanks to their unique electrochemical properties, molten oxide innovations offer significant potential benefits for improving energy efficiency. Advances in the field of solid and liquid state ionics for energy conversion are necessary to address the challenge of attaining cleaner and sustainable sources of energy. In this framework high temperature electrochemical devices based on oxide materials play a crucial role in decarbonising the future energy mix. Current targets of cost and durability necessitate solid oxide fuel cells (SOFCs) to operate in the intermediate temperature range. To achieve these targets, the oxygen ion conductivity of the SOFC ceramic oxide based electrolyte needs to be enhanced. Innovative molten oxide based electrolytes, with highest oxygen ionic conductivity at intermediate temperatures, show some real promise as the alternative materials. We summarize the recent progresses that have been made in the research and development of innovative alternative materials for the fabrication of novel electrochemical devices, such as molten oxide fuel cells (MOFCs) for electric power generation and molten oxide membranes (MOMs) for oxygen separation from air.