Mesure des coefficients de diffusion de <sup>22</sup>Na et de <sup>18</sup>F dans les bains de fluorures de sodium et d’aluminium,

Harari, Dominique; Lantelme, F.; Chemla, M.

doi:10.1051/jcp/196966s21286

Cited by 11 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Diffusion measurements in Graphite Sleeve cryolitic melts have been limited. Harari et al (1970) found the self diffusion coefficient for A1 to be 6.9 x lo-' cm"s in 3.0 CR bath at 1,051"C and 7.4 x lo-' cm'/s in 6.4 C R bath at 1,034OC. Lantelme and Chemla (1968) reported a diffusivity of 1.8 x lo-' cm2/s for AlF63-in cryolite at 1,05O0C.…”

Section: Cell Designmentioning

confidence: 94%

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Burgman¹,

Sides²

1988

AIChE Journal

View full text Add to dashboard Cite

Forced-convection mass transfer at the metal / bath interface during aluminum reduction from cryolitic melts was studied under reproducible convective conditions. A film of molten aluminum on a rotating molybdenum cylinder was the cathode. Concentration overpotential measured as a function of rotation rate, current density, and bath composition was converted to concentration differences between the bulk and the metal surface. Chosen as the basis for calculation of a mass transfer coefficient was the concentration of aluminum fluoride given by:2p( 100 -A1203% -CaF,% -IMP%)

show abstract

Section: Cell Designmentioning

confidence: 94%

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Burgman¹,

Sides²

1988

AIChE Journal

View full text Add to dashboard Cite

show abstract

“…The radiuses of ions shown in Table III were derived by rebuilding their ionic structures based on the literatures. [30][31][32] Harari et al 33,34 measured the diffusion coefficients of Na + , F − and 26 Al in the molten NaF-AlF 3 salts. According to the ranges of the reported values in the previous work, the diffusion coefficients of Na + and F − were set to 8 × 10 −5 cm 2 s −1 and 5 × 10 −5 cm 2 s −1 respectively in this study.…”

Section: + =mentioning

confidence: 99%

Thermodynamic Investigation on Ionic Structure and Electrical Conductivity of Molten NaF-AlF₃Salts

Tan

Yan

et al. 2020

J. Electrochem. Soc.

View full text Add to dashboard Cite

The behavior of the ions in the molten NaF-AlF 3 salts plays a significant role in aluminum reduction process. Many modelling works have been carried out to investigate the physical properties of the molten salts and the mass transfer behavior in the aluminum reduction cells. The Temkin model was widely used in the models above, in which the molten salts were assumed to be consisted by F − , AlF 4 − , AlF 5 2− , AlF 6 3− , and Al 2 F 7 − . However, beside those in the Temkin model, some additional fluoroaluminate complexes were reported as well, such as Al 2 F 9 3− , Al 2 F 10 4− and Al 3 F 14 5− . In this paper, the influence of the cryolite ratios (CR) and the temperature on the ionic structure of the molten salts was investigated by thermodynamic calculation based on the Temkin model combining with the Al 2 F 9 3− , Al 2 F 10 4− and Al 3 F 14 5− . The ionic structure of the molten salts with the various CR was discussed by analyzing fractions of all the anions. Additionally, the calculation of electrical conductivity of molten NaF-AlF 3 salts based on thermodynamic model involving eight anions was performed to illustrate the effect of fluoro-aluminate complexes on the electrical conductivity, which is compared and agrees well with the experimental results reported in the previous work.

show abstract

“…The industrial preparation of a l u m i n u m by electrolysis of alumina dissolved in fused cryolite involves complex electrochemical reactions, especially on the anodic side. In order to improve the working conditions of the electrolytic cells, much research is devoted to the study of these reactions (1); the nature of the ionic associations present in the bath has been studied (2), the diffusion coefficients (3), and the transport numbers of the constituent elements are k n o w n (4). F r o m these data different hypotheses have been built up to obtain a better insight into the mechanism of the electrolysis.…”

mentioning

confidence: 99%

Chronopotentiometric Investigation of the Anodic Reaction in Cryolite Melts: Influence of Dissolved Metal Traces

Lantelme¹,

Damianacos²,

Chemla³

1980

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

The mechanism of the anodic reaction in cryolite melt is studied in presence and in absence of a layer of a l u m i n u m metal in the cell. These two experimental conditions give rise to large differences which are interpreted on the basis of changes in the interracial properties at the electrode. The chronopotentiometric technique is used to obtain a better insight into these surface variations and on the gas evolution on the graphite anode. The dissolved metal reacts with the graphite to form at its surface a l u m i n u m or sodium carbides and gives a better contact between the electrolyte and the electrode. The analysis presented here is illustrated by the generation of three types of anode effects: By depletion of dissolved metal near the electrode which very much changes the wetting properties; by decrease of the pressure in the cell which, in absence of liquid metal, increases the dimension of retained gas bubbles; and by rapid repetition of the galvanostatic pulses which indicates that the gas evolution is a slow process. These observations have the same origin, i.e., the gas covering of the electrode which markedly depends on the presence of dissolved metal,The industrial preparation of a l u m i n u m by electrolysis of alumina dissolved in fused cryolite involves complex electrochemical reactions, especially on the anodic side. In order to improve the working conditions of the electrolytic cells, much research is devoted to the study of these reactions (1); the nature of the ionic associations present in the bath has been studied (2), the diffusion coefficients (3), and the transport numbers of the constituent elements are k n o w n (4). F r o m these data different hypotheses have been built up to obtain a better insight into the mechanism of the electrolysis.However, it has been recently (5, 6) shown that an important part of the observed overvoltage arises from the gas formation on the graphite anode. The kinetic parameters of the electrochemical reaction depend on the pressure in the cell, and the properties of the electrolyte-graphite interface (wetting angle ~ and interfacial tension 7) have a considerable influence on the electrode process.We plan to give here the results of the chronopotentiometric study of these phenomena. Special attention will be paid to the presence of dissolved a l u m i n u m in the bath (7) for it has been observed that, when molten cryolite is in contact with liquid a l u m i n u m metal, a very large change of the surface tension occurs (8). As a consequence, the results of chronopotentiometry are quite different to those obtained in pure ionic melts.In industrial cells the electrolyte is in contact with a layer of liquid a l u m i n u m ; a part of the faradaic loss can be attributed to the oxidation of the dissolved metal (9). Our research indicates also that this presence induces a large change in the interracial tension at the electrode and influences the gas coverage of the electrode surface.Experimental The experiments with liquid a l u m i n u m in the bath ar...

show abstract

Mesure des coefficients de diffusion de ²²Na et de ¹⁸F dans les bains de fluorures de sodium et d’aluminium,

Cited by 11 publications

References 0 publications

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Thermodynamic Investigation on Ionic Structure and Electrical Conductivity of Molten NaF-AlF₃Salts

Chronopotentiometric Investigation of the Anodic Reaction in Cryolite Melts: Influence of Dissolved Metal Traces

Contact Info

Product

Resources

About

Mesure des coefficients de diffusion de 22Na et de 18F dans les bains de fluorures de sodium et d’aluminium,

Cited by 11 publications

References 0 publications

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Electrochemical measurement of effective diffusivity in Hall‐Heroult electrolyte

Thermodynamic Investigation on Ionic Structure and Electrical Conductivity of Molten NaF-AlF3Salts

Chronopotentiometric Investigation of the Anodic Reaction in Cryolite Melts: Influence of Dissolved Metal Traces

Contact Info

Product

Resources

About

Mesure des coefficients de diffusion de ²²Na et de ¹⁸F dans les bains de fluorures de sodium et d’aluminium,

Thermodynamic Investigation on Ionic Structure and Electrical Conductivity of Molten NaF-AlF₃Salts