Ionic Conductivity Of Oxygen Research Articles

Effect of the Reactant Transportation on Performance of a Planar Solid Oxide Fuel Cell

The process of reactant transportation greatly affects the performance of solid oxide fuel cells (SOFCs). Therefore, a three-dimension numerical SOFC model was built to evaluate mainly the effect of the reactant transportation coupling of heat and mass transfer and electrochemical reactions, and the reliability of numerical calculations was validated. Numerical studies revealed the correlation of both increase of reactant concentration gradients and improved mass transfer capability of multi reactants in gas diffusion electrode with the enhancement of the SOFC performance, in the condition of enough supplies of the fuel and the oxidant. Further studies identified the oxygen ions conductivity in electrolytes played a critical role in energy output and thus the performance of SOFCs. For example, the current density would increase by 65% if the ionic conductivity of electrolytes doubled. This study gives insight into the significance of operational conditions, electrolytes, and structures on the ionic oxygen conductivity and further on the optimization of the SOFCs. Overall, the numerical modeling leads a clear path toward the optimization of SOFCs.

A new approach to modeling TiO2−x-based memristors using molecular dynamics simulation

This study aims to investigate the oxygen ion migration in defect rutile titanium dioxide (TiO2−x) in the presence of oxygen and titanium vacancies using a new approach based on molecular dynamic simulation. In this approach, the force field models along with Buckingham and Columbic potentials are used. For this purpose, the simulation is conducted in two different phases. In the first phase, the effect of temperature on the mean square displacements of oxygen ions is examined; besides, the diffusion and ionic conductivity of oxygen are studied in the absence of the electrical field. The results reveal that in the temperature range of 1100–1900 K, the oxygen vacancies tend to form clusters. These clusters consist of two oxygen vacancies. In the second phase, the memristor is applied to the model and hysteresis loops are studied in five cycles. The results of the second phase show that the new model correctly predicts the migration behavior of the oxygen ions in the memristor configuration. In conclusion, compared to the models using the Langevin equation method, the proposed model provides information which is closer to reality. Furthermore, the mean square displacements of the oxygen ions versus time are studied in the presence and absence of the electrical field at 300 K, and the results indicate greater diffusion in the presence of the electrical field.

Nd2−xGdxZr2O7 electrolytes: Thermal expansion and effect of temperature and dopant concentration on ionic conductivity of oxygen

The effect of temperature and complex dopant composition on oxygen ion conductivity in solid oxide electrolyte fuel cells was investigated by atomistic molecular dynamics simulation. A new electrolyte (Nd2−xGdxZr2O7) was selected to study oxygen ion conductivity using three Gd compositions (x = 0.8, 1.0, and 1.2) in a wide range of temperature (T = 1273 K–1873 K). MSD results of cations showed these groups of electrolyte are stable at high operating temperature. The first composition (x = 0.8) had the highest ionic conductivity that was in good agreement with the experimental data. A simple effective model that works with configuration energy of the oxygen crossing plate was applied to explain the observed conductivity trend. The model illustrated the point as well. Increasing Gd concentration decreases existence probability of easy crossing plate. Radial distribution function analysis also confirmed results. Thermal expansion of the electrolyte has a major effect on the selecting of the electrolyte materials; thus, this important factor was also studied. Results showed the first composition had the greatest thermal expansion.

Synthesis ofβ-Phase (Bi2O3)1-x(Dy2O3)x(0.01<x<0.10) System and Measurement of Oxygen Ionic Conductivity

β-phase (Bi2O3)1-x(Dy2O3)xsystem with tetragonal structure is synthesized for0.01<x<0.10molar doping. Unit cell parameters increased with increasing the doping. We have studied the dependence of total electrical conductvity on temperature, doping concentration ofβ-phase systems. The phase transition which manifests itself by the jump in the conductivity curve was also verified by DTA and both measurements are rather compatible. The electrical conductivity curves ofβ-phase structure revealed regular increase in the form of an Arrhenius curve. The activation energies are calculated from these graphs.Bi2O3-basedDy2O3doped ceramics show ionic oxygen conductivity. The conductivity increased as the doping concentration increased. The highest value of conductivity is 0.006 0.006ohm-1cm-1(600∘C)for theβ-phase (Bi2O3)0.91(Dy2O3)0.09(800∘C). The sample with the highest conductivity is (Bi2O3)0.91(Dy2O3)0.09(800∘C)binary system where 1.450 ohm−1cm−1(745∘C).

The oxygen permeation through YBa 2Cu 3O 6+x

The ionic conductivity of oxygen was studied in the dense ceramic YBa 2Cu 3O 6+ x using the oxygen permeation measurements. The temperature interval of measurements was 600–850°C and the limits of the partial pressure of oxygen were 0.06-1.00 atm. The method was based on the direct determination of the steady flow of oxygen through the specimen in the conditions of constant temperature with a small gradient of oxygen chemical potential along the sample. The oxygen diffusion coefficient was calculated. The activation energy ( U) of the oxygen conductivity (diffusion coefficient) was determined in the interval 0.35< x<0.6. The dependence of the activation energy on the oxygen content in the tetragonal phase, U=2.80-1.45 x (eV), was found. This dependence was explained by the interaction of the mobile oxygen ions.

The oxygen conductivity and chemical diffusion in YBa2Cu3O6+χ

Abstract The ionic conductivity of oxygen was studied in the dense ceramic YBa 2 Cu 3 O 6+χ using oxygen permeation measurements. The temperature interval of the measurements was 600–850°C and the limits of the partial pressure of oxygen were 0.06–1.00 atm. The method was based on the direct determination of the steady flow of oxygen through the specimen in the conditions of constant temperature with a small gradient of oxygen chemical potential along the sample. The oxygen diffusion coefficient was calculated. The activation energy ( U ) of the oxygen conductivity (diffusion coefficient) was determined in the interval 0.35 U = 2.80−1.45 χ eV was found. This dependence was explained by the interaction of the mobile oxygen ions.