Electronic/Ionic Conductivity and Oxygen Diffusion Coefficient af the Sr-Fe-Co-O System

1995 ◽  
Vol 393 ◽  
Author(s):  
B. Ma ◽  
J.-H. Park ◽  
C. U. Segre ◽  
U. Balachandran
Keyword(s):  
Diffusion Coefficient ◽  
Ionic Conductivity ◽  
Oxygen Diffusion ◽  
Ionic Conductivities ◽  
Transference Number ◽  
Transference Numbers ◽  
Oxygen Diffusion Coefficient ◽  
Ionic Transference Number ◽  
Local Fitting ◽  
Oxide Ion

ABSTRACTOxides in the Sr-Fe-Co-O system exhibit both electronic and ionic conductivities. Recently, the Sr-Fe-Co-O system attracted great attention because of its potential to be used for oxygen-permeable membranes that can operate without electrodes or external electrical circuitry. Electronic and ionic conductivities of two compositions of the Sr-Fe-Co-O system, named SFC-1 and SFC-2, have been measured at various temperatures. The electronic transference number is much greater than the ionic transference number in SFC-1, whereas the electronic and ionic transference numbers are very similar in SFC-2. At 800°C, the electronic and ionic conductivities are ≈76 and ≈4 S•cm−1, respectively, for SFC-1; whereas, for SFC-2, the electronic and ionic conductivities are ≈10 and ∼1 S•cm−1, respectively. By performing a local fitting to the equation σ • T = Aexp(-Ea / kT), we found that the oxide ion activation energies are 0.92 and 0.37 eV, respectively, for SFC-1 and SFC-2. The oxygen diffusion coefficient of SFC-2 is ≈ 9 x 10−7cm2/sec at 900°C.

scholarly journals Electrical Properties and Defect Structure in The Sr-Fe-Co-O System

1995 ◽  
Vol 411 ◽  
Author(s):  
B. Ma ◽  
C.-C. Chao ◽  
J.-H. Park ◽  
C. U. Segret ◽  
U. Balachandran
Keyword(s):  
Ionic Conductivity ◽  
Electrical Properties ◽  
Defect Structure ◽  
Ceramic Membrane ◽  
Ionic Conductivities ◽  
Transference Number ◽  
Total Conductivity ◽  
Interstitial Oxygen ◽  
Oxygen Ions ◽  
Ionic Transference Number

ABSTRACTThe ceramic Sr-Fe-Co-O has potential use as a membrane in gas separation. This material exhibits high conductivity of both electrons and oxygen ions. It allows oxygen to penetrate at high flux rates without other gas components. Electrical properties are essential to understanding the oxygen transport mechanism and defect structure of this material. By using a gas-tight electrochemical cell with flowing air as the reference environment, we were able to achieve an oxygen partial pressure (P02) as low as 10−16 atm. Total and ionic conductivities of Sr-Fe-Co-O have been studied as a function of P02 at elevated temperature. In air, both total and ionic conductivities increase with temperature, while the ionic transference number is almost independent of temperature, with a value of ≈0.4. Experimental results show that ionic conductivity decreases with decreasing P02 at high P02 (≥10−6 atm). This suggests that interstitial oxygen ions and electron holes are the dominant charge carriers. At 800°C in air, total conductivity and ionic conductivity are 17 and 7 S/cm, respectively. Defect dynamics in this system can be understood by means of the trivalence-to-divalence transition of Fe ions when P02 is reduced. By using the conductivity results, we estimated oxygen penneation through a ceramic membrane made of this material. The calculated oxygen permeability agrees with the experimental value obtained directly from an operating methane conversion reactor.

Use of a dynamic gassing-out method for activity and oxygen diffusion coefficient estimation in biofilms

1998 ◽  
Vol 37 (4-5) ◽  
pp. 171-175
Author(s):  
Artem Khlebnikov ◽  
Falilou Samb ◽  
Paul Péringer
Keyword(s):  
Diffusion Coefficient ◽  
Oxygen Uptake ◽  
Oxygen Diffusion ◽  
Fixed Bed ◽  
Biofilm Reactor ◽  
Strictly Aerobic ◽  
Comamonas Testosteroni ◽  
Respiration Activity ◽  
Oxygen Diffusion Coefficient ◽  
Biofilm Development

p-toluenesulphonic acid degradation by Comamonas testosteroni T-2 in multi-species biofilms was studied in a fixed bed biofilm reactor. The polypropylene static mixer elements (Sulzer Chemtech Ltd., Switzerland) were used as a support matrix for biofilm formation. Biofilm respiration was estimated using the dynamic gassing-out oxygen uptake method. A strong relation between oxygen uptake and reactor degradation efficiency was observed, because p-toluenesulphonate degradation is a strictly aerobic process. This technique also allowed us to estimate the thickness of the active layer in the studied system. The mean active thickness was in order of 200 μm, which is close to maximum oxygen penetration depth in biofilms. A transient mathematical model was established to evaluate oxygen diffusitivity in non-steady-state biofilms. Based on the DO concentration profiles, the oxygen diffusion coefficient and the maximum respiration activity were calculated. The oxygen diffusion coefficient obtained (2 10−10-1.2 10−9 m2 s−1) is in good agreement with published values. The DO diffusion coefficient varied with biofilm development. This may be, most likely, due to the biofilm density changes during the experiments. The knowledge of diffusivity changes in biofilms is particularly important for removal capacity estimation and appropriate reactor design.

Ionic Conductivity, Morphology and Transport Number of Lithium Ions in PMMA Based Gel Polymer Electrolytes

2013 ◽  
Vol 334-335 ◽  
pp. 137-142 ◽  
Author(s):  
Lisani Othman ◽  
Khairul Bahiyah Md. Isa ◽  
Zurina Osman ◽  
Rosiyah Yahya
Keyword(s):  
Ionic Conductivity ◽  
Salt Concentration ◽  
Polymer Electrolytes ◽  
Ethylene Carbonate ◽  
Transference Number ◽  
Gel Polymer Electrolytes ◽  
Casting Technique ◽  
Ionic Transference Number ◽  
Temperature Dependence Of Conductivity ◽  
Solution Casting Technique

The gel polymer electrolytes (GPEs) composed of polymethylmethacrylate (PMMA) with lithium trifluoromethanesulfonate (LiCF3SO3) salt dissolved in a binary mixture of ethylene carbonate (EC) and propylene carbonate (PC) organic solvents have been prepared by the solution casting technique. The samples are prepared by varying the salt concentrations from 5 wt.% to 30 wt.%. Impedance spectroscopy measurement has been carried out to determine the ionic conductivity of the samples. The sample containing 25 wt.% of LiCF3SO3salt exhibits the highest room temperature ionic conductivity of 2.56 x 10-3S cm-1. The conductivity of the GPEs has been found to depend on the salt concentration added to the sample, while at higher salt concentration reveals a decrease in the ionic conductivity due to ions association. The temperature dependence of conductivity from 303 K to 373 K is found to obey the Arrhenius law. The ionic transference number,tiof GPEs has been estimated by the DC polarization method and the value is found to be 0.98, 0.93, and 0.97 for the sample containing 25 wt.%, 5 wt.% and 30 wt.% respectively. This result is consistent with the conductivity studies.

scholarly journals The Study of Structural, Impedance and Energy Storage Behavior of Plasticized PVA:MC Based Proton Conducting Polymer Blend Electrolytes

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5030 ◽  
Author(s):  
Shujahadeen B. Aziz ◽  
Iver Brevik ◽  
M. A. Brza ◽  
A. S. F. M. Asnawi ◽  
Elham M. A. Dannoun ◽  
...  
Keyword(s):  
Energy Storage ◽  
Ionic Conductivity ◽  
Specific Capacitance ◽  
High Efficiency ◽  
Ammonium Thiocyanate ◽  
Transference Number ◽  
Equivalent Series Resistance ◽  
Ionic Transference Number ◽  
Main Charge ◽  
Electrochemical Double Layer

In this study, structural characterization, electrical properties and energy storage performance of plasticized polymer electrolytes based on polyvinyl alcohol/methylcellulose/ammonium thiocyanate (PVA/MC-NH4SCN) were carried out. An X-ray diffraction (XRD) study displayed that the plasticized electrolyte system with the uppermost value of direct current (DC) ionic conductivity was the most amorphous system. The electrolyte in the present work realized an ionic conductivity of 2.903 × 10−3 Scm−1 at room temperature. The main charge carrier in the electrolyte was found to be the ions with the ionic transference number (tion) of 0.912, compared to only 0.088 for the electronic transference number (telec). The electrochemical stability potential window of the electrolyte is 2.1 V. The specific capacitance was found to reduce from 102.88 F/g to 28.58 F/g as the scan rate increased in cyclic voltammetry (CV) analysis. The fabricated electrochemical double layer capacitor (EDLC) was stable up to 200 cycles with high efficiency. The specific capacitance obtained for the EDLC by using charge–discharge analysis was 132.7 F/g at the first cycle, which is slightly higher compared to the CV plot. The equivalent series resistance (ESR) increased from 58 to 171 Ω throughout the cycles, which indicates a good electrolyte/electrode contact. Ions in the electrolyte were considered to have almost the same amount of energy during the conduction process as the energy density is approximately at 14.0 Wh/kg throughout the 200 cycles. The power density is stabilized at the range of 1444.3 to 467.6 W/kg as the EDLC completed the cycles.

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