Electrochemistry—I

Lantelme, F.; Inman, D.; Lovering, D. G.

doi:10.1007/978-1-4615-7502-3_5

Cited by 16 publications

(19 citation statements)

References 149 publications

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“…The experiments were carried out under a dry and oxygen-free argon atmosphere. The temperature was maintained at a fixed value, ±0.5 °C, by an electrical furnace fitted with a PID controller …”

Section: Methodsmentioning

confidence: 99%

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Activity Measurements in Nickel−Platinum Alloys

and

Salmi

1996

J. Phys. Chem.

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The thermodynamic properties of Ni−Pt metallic alloys, in the temperature range 500−720 °C, are measured from energy dispersive analysis of the X-ray of alloys prepared by fused salt electrolysis at constant potentials in the cell: Ni−Pt alloy|fused electrolyte + NiCl2|Ni. For nickel-rich alloys, the partial entropy of nickel exhibits a nearly ideal behavior. For a molar fraction of nickel between 0.4 and 0.6, a rapid change in the thermodynamic properties occurs. A minimum in the entropy of mixing is found at xNi ≃ 0.5. The departure from ideality of the Gibbs energy is mainly due to the negative value of the molar enthalpy of mixing; ΔH 0.5 = −10.5 kJ mol-1. This behavior, which results from the preferential interaction Pt−Ni, is linked to an order−disorder transformation around the equiatomic composition.

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Section: Methodsmentioning

confidence: 99%

“…The temperature was maintained at a fixed value, (0.5 °C, by an electrical furnace fitted with a PID controller. 9 The electrodes were made of a sheet of pure nickel and a rod of platinum (diameter 1 mm). The metals were supplied by Johnson Matthey.…”

Section: Methodsmentioning

confidence: 99%

Activity Measurements in Nickel−Platinum Alloys

and

Salmi

1996

J. Phys. Chem.

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“…In order to observe the formation of gas bubbles a transparent electrical furnace was used. For more details concerning the cell, the electrolyte preparation and the atmosphere purification see [10].…”

Section: Methodsmentioning

confidence: 99%

“…The ohmic drop due to the passage of a current, /, through this shell is dt/R = I dRe (9) with I = fs dI (10) dI being given by Equation 3. For a not too large current density the concentration, Cr, is given by the Nernst equation (Equation 2) where E = E ~ + %T-However the current density increases considerably near the tip of the triple contact and the charge transfer kinetics has to be considered; the concentration, Cr, is then deduced from the equation…”

Section: Role Of the Gas Bubbles In Chlorine Reductionmentioning

confidence: 99%

Role of gas bubbles adsorbed on a carbon electrode: electroreduction of chlorine gas in fused salts

1989

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The reaction C12 + 2e ~ 2C1-has been studied by transient electrochemical techniques on a vitreous carbon electrode in fused alkali chlorides. Two regimes have been detected: for small overpotentials the electrode response obeys the classical laws of linear diffusion, for larger overpotentials the electrode behaviour involves the gas coming from the bubbles. A model is presented to describe these mechanisms. Four steps are considered: dissolution of chlorine around a gas bubble, diffusion in the electrolyte, charge transfer and chloride ion migration. The first step is always rapid. The influence of the three other steps is examined. It is indicated that the largest part of the reaction occurs near the triple contact interface. At the very extremity of the tip, charge transfer is the primary limiting factor; it is considered that over a distance of a few atomic diameters the mass transport is very rapid. At the largest distances the diffusion of dissolved chlorine constitutes the main limiting factor. The ohmic drop due to the electrical resistance of the electrolyte remains small. The influence of the interfacial tension and of the shape of the bubbles are predicted. The non-stationary situation is also examined in order to take into account the size variation of the gas bubbles during transient conditions.

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“…The wide potential span between decomposition limits allows the electrowinning of highly electropositive metals or very electronegative elements. 1 In the authors' laboratory a great deal of research has been devoted to the industrial preparation of aluminium and fluorine. More recently, this interest has been extended to the preparation of refractory metals.…”

Section: Introductionmentioning

confidence: 99%

Niobium and titanium electrowinning in fused salts

Lantelme

Groult

2010

Mineral Processing and Extractive Metallurgy

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In the frame of the preparation of refractory metals, thermodynamics and kinetics properties of salts of refractory metals (mainly titanium, and niobium) dissolved in alkali chloride melts were determined by transient electrochemical techniques. Two kinds of reactions occur in the melts: homogeneous reactions such as: Me nzz ð Þz zne { 'Me z where Me (nzz)z and Me zz are two oxidation states of metal ions; heterogeneous reactions corresponding to the metal deposition: Me nz zne { 'Me. The potential corresponding to the reactions are linked to the Gibbs free energy of formation of salt solutions. The formal standard potentials of the various redox reactions were measured by transient electrochemical techniques. These techniques were also used to determine the reaction kinetics and to measure the diffusion coefficients of the active ions which control the deposition process. In pure chloride melts, the metal is obtained from the reduction of lower oxidation states, Ti 2z and Nb 3z . However, disproportionation reactions and the formation of insoluble subhalides perturb the reduction reaction. When a small amount of NaF was added to the bath, the direct reduction of Ti 3z or Nb 4z to metal was obtained, which greatly improved the quality of the deposit.

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Electrochemistry—I

Abstract: This is intended to be the first part of an occasional series on electrochemical techniques in molten salts. Such a diversity of equipment, instrumental, and handling problems arises in this subject area that a division into parts seemed appropriate.

Cited by 16 publications

References 149 publications

Activity Measurements in Nickel−Platinum Alloys

Activity Measurements in Nickel−Platinum Alloys

Role of gas bubbles adsorbed on a carbon electrode: electroreduction of chlorine gas in fused salts

Niobium and titanium electrowinning in fused salts

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