Electromotive Force Studies Research Articles

Thermochemical Expansion and Protonic and Electronic Hole Conductivity of Grain Interior and Grain Boundaries in 10 Mole% Y-Substituted SrZrO3.

Proton conducting acceptor-doped SrZrO3 has a history as long as that of BaZrO3 , but has attracted less interest. Inspired by its higher transport number of ionic conduction in wet oxygen revealed by our recent work, we here explore further aspects of doped SrZrO3 as electrolyte in proton ceramic electrochemical cells. In-situ high temperature XRD (HT-XRD) analysis of SrZr0.9 Y0.1 O3-δ (SZY10) indicated an anisotropic chemical expansion of hydration, stronger along the b than the a direction, and negative in the c direction. A systematic electromotive force (EMF) and impedance spectroscopy study as a function of and allowed determination of partial conductivities of electron holes and ions (mainly protons) in bulk (grain interior) and grain boundaries. Enthalpies and preexponentials were determined and interpreted for bulk and grain boundary partial conductivities based on defect chemistry and a brick layer model. The hole conductivity in bulk is modest and ensures high ionic transport numbers in oxidizing atmospheres, while grain boundaries exhibit lower ionic transport numbers from a relatively higher hole conductivity attributed primarily to tunnelling past the deepest part of the space charge region. Y-doped SrZrO3 (SZY) materials exhibit lower proton conductivities but excel over Y-doped BaZrO3 (BZY) in terms of thermal expansion compatibility with electrode materials and higher ionic transport numbers in oxidizing atmospheres and may hence be candidates for functional layers between BZY-based electrolytes and positrodes in proton ceramic electrochemical cells.

Phase diagram, thermodynamic studies, and ab-initio calculations of the Ge-Li system

The limiting enthalpy of solution of liquid germanium in the liquid tin ΔsolH¯Ge(l)∞ was measured at 927 K and equals 3.24 ± 0.34 kJ/mol at. The standard enthalpy of formation of intermetallic phases from the Ge-Li system were calculated at 747 K with the use of the solution calorimetric method. These alloys and intermetallic phases were prepared from pure, metallic germanium and lithium, which were melted in a glove-box filled with high purity argon with a very low concentration of impurities. The X-ray diffraction measurements were conducted to verify the structure of the prepared alloys. The electromotive force studies were performed at three temperatures: 634 K, 807 K, and 841 K by the titration technique. Based on obtained results and other thermodynamic quantities available in the literature the thermodynamic properties of phases were optimized, and the Ge-Li phase diagram was determined.

EMF study of liquid Al–Fe–Ge alloys

Abstract The thermodynamic properties of ternary liquid Al–Fe–Ge alloys have been studied in the temperature range of 1050 – 1250 K by the electromotive force (EMF) technique with a liquid electrolyte. The ternary alloys are characterized by negative deviations from Raoult’s law.

Study of electromotive force of a new type of membraneless fuel cell operating on renewable fuel

The possibility of using base metals and alloys based on them as electrodes for a new type of membraneless fuel cells operating on renewable fuel has been investigated. The phase boundary of two immiscible liquids in the ethanol-water-potassium hydroxide system plays a role of a membrane in these elements. Top phase of this fuel cell has significant alcohol content and insignificant electrolyte content, bottom phase has significant electrolyte content and insignificant alcohol content. Platinum- and ruthenium-coated titanium electrode, carbon electrode and stainless steel electrode were used as the anode. Stainless steel electrode and carbon steel electrode were used as the cathode. The possibility of using ferrous alloys as anode and cathode catalysts in this type of fuel cells is shown.

Electromotive force study of lanthanum in liquid bismuth

The thermodynamics of lanthanum (La) dissolved in liquid bismuth (Bi) were determined by means of the electromotive force (EMF) measurement using a galvanic cell consisting of molten chloride and liquid bismuth at the temperature ranging from 723 K to 975 K. A considerable increase of the activity coefficient with temperature was observed for the La-Bi alloy. In addition, the activity coefficient increased slightly with the concentration of La. The values of the molar excess free energy of formation, the excess enthalpy, and the excess entropy of La dissolved in Bi were determined. The heat of formation of liquid La-Bi alloys (ΔHLa–BiM) was deduced from the measured activity coefficient. There is a linear dependence of experimental ΔHLa–BiM on the La concentration.

Calorimetric and Electromotive Force Measurements of Al-Li-Zn Liquid Solutions

The solution calorimetry and electromotive force methods were used for the study of the mixing enthalpy and partial excess Gibbs energy of the Al-Li-Zn liquid solutions. Calorimetric investigations were conducted for solutions with the ratio of XLi/XAl and XLi/XZn = 0.8/0.2 and at the temperatures of 942 and 978 K, respectively. The electromotive force studies were performed at two temperatures: 873 and 923 K by the titration technique and for dilute solutions. Based on the data of the mixing enthalpy change and the partial excess Gibbs energy of Li available in the literature, together with that obtained in these studies, the ternary interaction parameters were elaborated. The comparative analysis of the experimental mixing enthalpy change generally showed a good agreement with the values calculated based on different models. The observed deviations between the experimental and the calculated values were, for most of the experimental data, lower than 1 kJ/mol. The experimental partial excess Gibbs energy of Li showed a satisfactory agreement with that modeled on the basis of the ternary parameters elaborated in this work.

Electromotive force study on interaction between a triblock copolymer and cationic surfactants in water

The interaction between a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer F127 and three cationic surfactants with varying alkyl chain length in water were investigated in detail by electromotive force (EMF) studies. The cationic surfactants investigated are hexadecyltrimethylammonium bromide (HTAB), myristytrimethylammonium bromide (MTAB), and lauryltrimethylammonium bromide (LTAB) which have carbon numbers of 16, 14, and 12 in the alkyl chain, respectively. Obvious binding was detected by EMF measurements between F127 and HTAB. For MTAB, the binding has also been detected with a weaker strength than that of HTAB. The LTAB/F127 mixed system exhibits the weakest binding, presumably due to the too short alkyl chain. This indicates that the binding between cationic surfactants and F127 is mainly dominated by the hydrophobic/hydrophobic interaction. In addition, the interaction also shows considerable dependence on the concentration of F127 and solution parameters such as the salinity.

Study of Back Electromotive Force in the Preparation of Al-Ca Alloy by Molten Salt Electrolysis Method

Al-Ca master alloy was prepared by molten salt electrolysis method, using a mixed molten salt system of CaCl2-CaF2and feeding CaO as electrolysis material. The technological parameters such as back electromotive force (BEMF), cell voltage, and current were measured by testing device of molten salt electrolysis. The effects of current density, CaO addition, electrolysis time and feeding period on the back electromotive force in the electrolysis process are studied. The results indicate that back electromotive force increases with current density increasing, the feeding period is 30min measured by potential control method. Finally, the Al-Ca alloy with the Ca content of 11.6wt% can be obtained by electrolyzing for 1h at the current of 7A and at 740.

Electromotive Force Study of the Liquid Silver-Bismuth-Tin Alloys

Electromotive Force Study of the Liquid Silver-Bismuth-Tin Alloys

Electromotive force study of the liquid silver-bismuth-tin alloys

The Ag−Bi−Sn alloy system has been assessed twice, so far, for its potential applications as a lead-free solder material. The first assessment was based on binary data only; the second assessment introduced ternary parameters. It was noted in conclusion that more experimental studies were needed, especially for the liquid phase. The electromotive force (emf) measurement method was used in this study to determine the thermodynamic properties of liquid Ag−Bi−Sn alloys using solid electrolyte galvanic cells as shown below: Re, Ag−Bi−Sn, SnO2 |Yttria Stabilized Zirconia| Ni, NiO, Pt, Re, Sn, SnO2 |Yttria Stabilized Zirconia| Ni, NiO, Pt. Alloy compositions for in vestigation were chosen along three constant Bi-to-Sn ratio lines (1/3, 1, and 3) and with the silver content changing from 10 up to 90 at.%, every 10 at.%, resulting in a total of 27 different alloy samples. The temperature of the measurements varied from 975 to 1400 K. A linear dependence of the emf on temperature was observed for all compositions, and the appropriate line equations were derived. Excess partial Gibbs energies of Sn were then calculated at 1200 K and compared with the results of the calculations of both assessments; Gibbs energy of formation of SnO2 was determined as well. It was then shown that our new emf data fit better to the binary formalism-based calculations than to the second assessment results.

Application of Finite-Element Method to a PMLSM with Non-Sinusoidal Electromotive Force

An accurate thrust control of permanent magnet linear synchronous motors (PMLSM) is more efficient with a fine knowledge of the harmonics value of the electromotive force (EMF). This is often difficult to obtain experimentally for a PMLSM. As a consequence, this paper deals with the study of the non-sinusoidal EMF of a PMLSM using the 3D Finite-Element Method (FEM). Two potential formulations are used to consider several cases. Afterwards, for the same accuracy, the computation times are examined. The results of the FEM are compared to those given by the measurements from a test bench composed of a Siemens LIMES400/120 linear motor and a dSPACE DS1005 real-time controller board. Finally, the advantages and the limitations of the FE Analysis will be discussed.

Electromotive force studies about some dyes–cationic surfactants interactions in aqueous solutions

Surfactants have been widely used as auxiliaries in many areas of textile finishing. The nature of the interactions between dyes and surfactants is one of the basic pieces of information for understanding the process of dyeing and finishing of textile material. The interactions of Orange II and Direct Red 80, anionic azo dyes, and also Indigocarmine with n-dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HTAB) in submicellar concentration ranges have been investigated by a potentiometric technique using DTAB and HTAB membrane selective electrodes. The detection limits for HTAB and DTAB electrodes are 8 × 10 −7 and 5 × 10 −7 mol dm −3, respectively. The data show that significant binding takes place and the critical concentrations associated with the saturation of the dyes with bound surfactant have been determined. It has also been shown that free micelles occur in solution before the dyes become fully saturated with bound surfactant. The results also show that under the same experimental conditions the complex formation between HTAB and Orange II takes place at more less surfactant concentration than between DTAB and Orange II. EMF data and comparison between calibration and binding curves showed that interaction between HTAB and Orange II is more than that between Direct Red 80 and Indigocarmine.

Isothermal Titration Calorimetric and Electromotive Force Studies on Binding Interactions of Hydrophobic Ethoxylated Urethane and Sodium Dodecyl Sulfate of Different Molecular Masses

The interactions between hydrophobic ethoxylated urethane (HEUR) and sodium dodecyl sulfate (SDS) were examined by isothermal titration calorimetric (ITC) and surfactant-selective electrode (EMF) t...

EMF study of liquid Al–Fe–Ge alloys

The thermodynamic properties of ternary liquid Al - Fe - Ge alloys have been studied in the temperature range of 1050 - 1250 K by the electromotive force (EMF) technique with a liquid electrolyte. The ternary alloys are character- ized by negative deviations from Raoult's law. dium chloride (purity 99.5 %) and aluminium chloride (pur- ity 99.95 %) were purchased from Sigma-Aldrich and were used for the electrolyte preparation. The electromotive forces of ( - )Ta|Alliq| AlCl3 in KCl + NaCl (azeotropic solution) |(AlxFeyGe 1- x - y)liq| Ta(+) concentration cells were measured in the temperature range of 1050 - 1250 K under argon at atmospheric pressure. The EMF values at one temperature were measured several times both during heating and during cooling of the melt. The thermodynamic properties of liquid ternary alloys were studied for four cross-sections with xGe : xFe being 0.55 : 0.45, 0.6 : 0.4, 0.7 : 0.3, and 0.85 : 0.15. The Al mole fraction was from 0.1 up to 0.8. The cell construction, rou- tine of electrochemical technique, and mathematical pro- cessing of the initial experimental data are described in (4). The partial thermodynamic functions of mixing of Al were calculated from the EMF data for the temperature of 1173 K. The integral excess thermodynamic functions of mixing were defined from the partial ones by integration of the Gibbs-Duhem equation:

Interactions between Sodium Dodecyl Sulfate and Six Nonionic Copolymers Containing 10 Mol of Different Covalently Bonded Derivatives of Vinyl Acrylic Acid: Electromotive Force and Microcalorimetry Studies

The binding of sodium dodecyl sulfate (SDS) to six random nonionic copolymers with the general chemical name polyvinyl(methyl imidazole-co-pyrrolidone-co-acrylate) were studied using electromotive force measurements (EMF) and isothermal titration calorimetry (ITC). In terms of their composition expressed in mole percent, each polymer contains 45 mol % methyl vinyl imidazole (MVI), 45 mol % vinyl pyrrolidone (VP), and 10 mol % of each of six different substituted acrylates. The purpose of the work was to investigate how subtle structural changes in the acrylate monomer affect the binding properties of SDS. The results showed significant differences in the binding behavior of the polymers, which are reflected in the determination of critical constants associated with SDS binding, like binding isotherms, the degree of sodium ion association to the bound SDS micelles, and the binding enthalpies as measured by ITC, especially in the early stages of binding. This opens the possibility of using ITC and EMF exper...

Al-Cu-Li system electromotive force and calorimetric studies—Phase diagram calculations of the Al-Rich part

Electromotive force (emf) studies were made for solid and liquid AI-Cu-Li alloys. Measurements were conducted on four sets of alloys at temperatures and composition ranges as follows (where XLi is mole fraction): T/K XAl/XCu Li Composition Range 888 9 0.001 ≤XLi ≤ 0.639 888 4 0.013 ≤XLi ≤ 0.815 828 7/3 0.0001 ≤ XLi ≤ 0.5 778 7/3 0.0032 ≤ XLi ≤ 0.639 For these alloys, the Li concentration was introduced into an alloy by coulometric titration. Supplementary emf measurements were made at 828 K on 23 pyrometallugically prepared alloys with XA1/XCu=7/3 and with a XLi range of 0.05≤XLi≤0.639. Good agreement was observed between the results from this set of alloys and the results from alloys prepared by coulometric titration. Drop calorimetric studies also were performed at two temperatures to determine mixing enthalpies for liquid Al-Cu-Li alloys. At 986 K, Cu was dropped into an Al-Li bath with XAl/XLi=4 to form liquid alloys with 0.02≤XCu≤0.285, and, at 945 K, Li was dropped into an Al-Cu bath to form alloys with 0.023≤XLi≤0.265. The experimental emf and calorimetric results were combined with available data from the literature to make a new evaluation and to calculate the Al-Cu-Li phase diagram. Good conformity between emf and calorimetric results from the present studies and the optimized thermodynamic parameters was observed for XAl/XCu=9 and 4; however, for XAI/XCu=7/3, differences were observed in the one-, two-, and three-phase boundaries when compared with existing and calculated phase equilibria of the AI-Cu-Li system.

Phase stability domains of (Bi,Pb)-2223: Data sources, correlation, and assessment

An assessment of the phase stability of lead-doped Bi-2223, (Bi,Pb)-2223, as a function of temperature and partial pressure of oxygen, p(O 2), derived from equilibration and electromotive force studies carried out by numerous groups of investigators is presented. The data obtained from this assessment, coupled with additional more recent data from our laboratory, can be used to estimate the stability of this promising high-Tc bismuth cuprate system in the temperature range from 650 to 870°C and for oxygen partial pressures ranging from 10 −5 to one atm. For oxygen contents above pO 2=0.02 atm, the stability boundaries are reasonably well known. For smaller pO 2, discrepancies are found.

Binding of Sodium Dodecyl Sulfate to Some Polyethyleneimines and Their Ethoxylated Derivatives at Different pH Values. Electromotive Force and Microcalorimetry Studies

Electromotive force and isothermal titration microcalorimetry measurements have been carried out to study the interactions of sodium dodecyl sulfate (SDS) with polyethyleneimines (PEI's) and some ethoxylated PEI's at different pH's. In all cases the polymers show a remarkable affinity toward SDS. The SDS concentration at the onset of binding decreases with decreasing pH. At low pH's phase separation similar to that observed for strong polyelectrolyte/oppositely charged surfactant systems occurs presumably as a consequence of the protonation of the N atoms in the polymer to form a polycation. The SDS range over which phase separation occurs decreases as the size of the ethoxylated chains increases, and for the polymer with the longest ethoxylated chain no precipitation occurs. In many cases where phase separation occurs, as more SDS is added the polymer/surfactant complex often resolubilizes and binding proceeds until the polymer becomes saturated with bound SDS. For any given polymer at this limiting stage in the binding, the number of surfactant molecules bound per mole of polymer is independent of pH. In addition both the charged and uncharged N atoms as well as the pendant ethoxylated chains make significant contributions to the binding process.

Electromotive Force Studies Associated with the Binding of Sodium Dodecyl Sulfate to a Range of Nonionic Polymers

The interaction between sodium dodecyl sulfate (SDS) and a variety of nonionic polymers has been studied using an SDS membrane selective electrode. From the experimental data critical concentrations associated with the binding process have been evaluated. These are (I) the onset of binding T 1 , (II) the SDS concentration T 2 corresponding to the polymer becoming saturated with bound SDS, and (III) the SDS concentration (T f ) when free micelles occur in solution. The binding isotherms have also been measured at different added salt concentrations and in some cases different molecular weight polymers. At low salt concentration the different polymers show some selectivity toward SDS in the sense that the maximum amount of SDS they can bind per gram varies from polymer to polymer. However, in the presence of added salt, this selectivity is almost removed and all polymers seem to behave in a similar fashion. The presence of free sodium counterions in solution whether generated as a result oflow counterion binding by the bound surfactant or by simply adding salt also governs the concentrations at which free micelles occur in solution.

Measurement of Gibbs energy of formation of Ca2 PbO4 using a solid-state cell with three electrodes

Phase relations in the system Ca–Pb–O at 1100 K have been determined by equilibrating 18 compositions in the ternary and identifying the phases present in quenched samples by X-ray diffraction and energy dispersive X-ray analysis (EDX). Only one ternary compound Ca2 PbO4 was found to be present. The compound coexists with CaO and PbO. The intermetallic compounds Ca2 Pb, Ca5 Pb3 and CaPb and liquid alloys are in equilibrium with CaO. The standard Gibbs energies of formation of Ca2 PbO4 (880–1100 K) and Pb3O4 (770–910 K) were determined using solid-state cells based on yttria-stabilized zirconia as the solid electrolyte. Pure oxygen gas at 0.1 MPa was used as the reference electrode. For measurements on Ca2 PbO4 , a novel cell design with three electrodes in series, separated by solid electrolyte membranes, was used to avoid polarization of the electrode containing three solid phases. Two three-phase electrodes were used. The first absorbs the electrochemical flux of oxygen from the reference electrode to the measuring electrode. The other three-phase electrode, which is unaffected by the oxygen flux through the solid electrolyte, is used for electromotive force (EMF) measurement. The results from EMF studies were cross-checked using thermogravimetry (TG) under controlled oxygen partial pressures. The stability of Pb3O4 was investigated using a conventional solid-state cell with RuO2 electrodes. The results can be summarized by the following equations: