Recherches sur l'obtention, la séparation et la purification du tantale et du niobium, notamment par voie électrolytique. IV. Essais de séparation électrolytique du niobium et du tantale

Monnier, R.; Grandjean, Patricia; Zahler, J.

doi:10.1002/hlca.19630460752

Cited by 5 publications

(2 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6 In cryolitic melts of 5 wt.% SiO 2 or 5 wt.% SiO 2 and 10% Al 2 O 3 the decomposition voltage of silica was found to be in the range of 1.00-1.25 V in the temperature range of 1000 °C-1030 °C and according to the experimental conditions mentioned in 6,7 where the cathode was either the bottom of a graphite crucible, aluminium, or copper. The observed decomposition voltage of alumina was 1.25-1.45 V, which was in agreement with the values reported in, 8 when cryolitic melts saturated with alumina at 1000 °C were tested using either aluminium or aluminium-silicon alloy(12.5 wt.% Si) as a cathode. 6 When copper was used as a cathode, the decomposition voltage of alumina was 1.50 V at 1030 °C.…”

supporting

confidence: 91%

Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

Awayssa

Sævarsdóttir

Meirbekova

et al. 2021

J. Electrochem. Soc.

View full text Add to dashboard Cite

Direct production of aluminium-silicon alloy during aluminium electrolysis in fluoride-based melts was studied. Experiments were carried out in a laboratory cell dedicated to current efficiency measurements. Electrolysis was run at 960 °C, 970 °C, and 980 °C at a fixed cathodic current density (CCD) of 0.9 A cm−2 and a cryolite ratio (CR) of 2.2. Silicon content was up to 4 wt.% added via SiO2 precursor. SEM/EDX and ICP-MS were carried out for some of the deposits to characterize the solidified deposit surface of the produced metal and to estimate the current efficiency for Al-Si alloy. It was possible to produce alloys of at least 9.0 wt.% Si in Al with an estimated alloy current efficiency of approximately 63%. The presence of silica in the melt brought a rise in the recorded cell voltage which implies a lowering of the electrolyte conductivity.

show abstract

supporting

confidence: 91%

Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

Awayssa

Sævarsdóttir

Meirbekova

et al. 2021

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…Washing of cathodic deposits.--After having tried different washing techniques described in the literature (1,9,16,23,24), we found (25) that the best method was as follows:…”

Section: Experimental Technique--raw Materials--potas-mentioning

confidence: 99%

Comparative Study of the Electrocrystallization of Tantalum and Niobium from Molten Fluoride Mixtures

Decroly¹,

Mukhtar²,

Winand³

1968

J. Electrochem. Soc.

View full text Add to dashboard Cite

A comparison has been made of the electrocrystallization of tantalum and niobium from baths containing either KF and K2TaF7 or KF and K2NbFT. The main purpose of the work was to determine why current efficiencies are generally much lower for niobium than for tantalum under the same experimental conditions. The phase diagram of the system KF-K2NbF7 has been drawn. Comparison with the diagrams of the system KF-K2TaF7 found in the literature does not give any evidence for a basic difference in the nature of the ionic species present in both types of baths. The results of the electrolyses performed have led to the following main conclusions: (A) An increase of the K2NbF7 or K2TaF7 content of the bath results in a considerable decrease of the current efficiency. This effect is much more striking for niobium than for tantalum. The grain size decreases also when the K2NbF7 or K2TaF7 content of the bath increases. (B) The current efficiency increases roughly with the cathodic current density while the grain size shows a very complex behavior against the same parameter. (C) The current efficiency decreases and the grain size increases when the length of the electrolysis increases. (D) The grain size decreases regularly when the temperature increases, while the current efficiency passes through a maximum at about 900~ Cathodic polarization curves drawn in both types of bath have shown a rather complex behavior of the ionic species to be discharged at the cathode. It appears that some part of the metallic deposit at the cathode is removed from it by the agitation of the bath and by its own weight and is redissolved in the bath through a chemical reaction giving rise to lower valency species. A part of these species is reoxidized at the anode, and another part of them participates again in the cathodic process. This phenomenon is much more effective for niobium than for tantalum in the same type of bath. All the experimental observations are interpreted in terms of this mechanism.It is well known that tantalum and niobium have very similar chemical properties, so similar indeed that it is necessary to use very elaborate methods to separate them during the mineral and chemical processing of their ores.It is thus quite astonishing that, while tantalum can be prepared economically by fused salt electrolysis, all the attempts to prepare niobium in the same way failed, the current efficiency being very low. It should of course be very interesting to know why there is such a big difference in the behavior of the two metals during the electrolysis. In this respect, although the literature (1) contains a rather large number of papers on the electrowinning of tantalum and niobium, it is rather difficult to draw any general conclusion from the published results. This is mainly due to the fact that most of the researchers have worked only on one of the two metals and generally under conditions so different that any valuable comparison of the results is impossible. It should be pointed out however that Chuk-Ching Ma (2) has studied the ...

show abstract

Recherches sur le raffinage électrolytique du silicium

Monnier

Giacometti

1964

Helvetica Chimica Acta

Self Cite

View full text Add to dashboard Cite

show abstract

Recherches sur l'obtention, la séparation et la purification du tantale et du niobium, notamment par voie électrolytique. IV. Essais de séparation électrolytique du niobium et du tantale

Abstract: The electrolytic separation of Ta and Nb from cryolitic solutions of their respective pentoxides gives, under specified conditions, a yield of 90% of the initial Nb with a purity better than 98%.

Cited by 5 publications

References 3 publications

Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

Comparative Study of the Electrocrystallization of Tantalum and Niobium from Molten Fluoride Mixtures

Recherches sur le raffinage électrolytique du silicium

Contact Info

Product

Resources

About