The Electrodeposition of Coherent Deposits of Refractory Metals

Senderoff, S.; Mellors, G. W.

doi:10.1149/1.2423866

Cited by 68 publications

(39 citation statements)

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“…Thus, B2 is also reversible. For a reversible process involving the deposition of an insoluble product the following I vs. v'2 relation is valid21 = 1.082 nFAC0 (nFD0v)"2/QrrRTfl"2 [4] Thus, one obtains a value of 3.4 X iO cm2/s for the Nb(IV) fluoro complex. However, during the two-step reduction of the Nb(V) complexes, one might argue that the Nb(IV) concentration cannot be estimated with great certainty.…”

Section: Results Andmentioning

confidence: 99%

The Redox Chemistry of Niobium(V) Fluoro and Oxofluoro Complexes in LiF‐NaF‐KF Melts

Matthiesen

Christensen

Barner

et al. 1996

J. Electrochem. Soc.

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The electrochemical behavior of niobium(V) fluoro and oxofluoro complexes in eutectic LiF-NaF-KF (FLINAK) melts at 700°C has been studied by cyclic voltammetry. The fluoro complexes NbF, introduced into the melt by the addition of K2NbF7, can be reduced to niobium metal in two reversible steps involving one and four electrons, respectively. At 700°C the diffusion constants of the fluoro niobate complexes involved in these reduction steps, i.e., NbF and were determined to be 8.3 X 106 and 3.4 X iO cm2/s, respectively. Titration with equivalent amounts of oxide ions, introduced as Na2O, leads to a conversion of NbF to oxofluoro complexes of the type NbOF3 and NbO2F. At 700°C the conversion of NbF to NbOF3 is not complete, and the degree of conversion is shown to depend stronly on temperature. Thus, at 645°C the conversion is more nearly complete than at 700°C, while the presence of NbOF complexes cannot be identified in cyclic voltammograms obtained at 795°C. It is concluded that the degree of conversion decreases with increasing temperature. At Na20/K2NbF7 molar ratios equal to three, electroactivity is still observed in the melt, indicating the presence of solute secies. The products of reduction of the oxofluoro complexes have not been identified because the reduction of NbOF,°i ons cannot be obtained without simultaneous reduction of Nb(IV)F°4 ions, and at Na2O/K2NbF7 molar ratios exceeding two, no deposits are obtained. The reduction of the oxofluoro complex NbO2F, and complexes formed at Na2O/K2NbF7 molar ratios exceeding two always proceed in one step.

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Section: Results Andmentioning

confidence: 99%

The Redox Chemistry of Niobium(V) Fluoro and Oxofluoro Complexes in LiF‐NaF‐KF Melts

Matthiesen

Christensen

Barner

et al. 1996

J. Electrochem. Soc.

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“…By degassing of Nb electrorefined by Senderoff and Mellors 22,23) at uum of 10 −3 Pa at a speed of 3 mm min −1 proved to be sufficient. The progress in purification over the various processing steps can be seen from the impurity concentrations given in Table 2 which show that Ta and W concentrations < 1 at ppm are obtained.…”

Section: Purification By Liquid-liquid Extraction Combinedmentioning

confidence: 99%

“…On the basis of the earlier results of Senderoff and Mellors, 22,23) Schulze in Stuttgart developed an optimized electrorefining process of Nb. 10,11) The optimization was directed mainly on the purification effect with respect to Ta and W and on the deposition of compact Nb metal having a smooth surface and a low gas content.…”

Section: Purification By Liquid-liquid Extraction Combinedmentioning

confidence: 99%

Preparation of Ultra High Purity Niobium

Koethe

Moench

2000

Mater. Trans., JIM

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The preparation of ultra high purity niobium ("UHP-Nb") from commercial starting materials (niobium metal or Nb 2 O 5 ) requires the elimination of all impurities down to the ppm, sub-ppm or even ppb level. This is possible only by application of a complex technology comprising the following essential processing steps:(1) Removal of critical metallic elements (especially Ta and W) which cannot be evaporated by electron beam melting through suitable chemical and/or physical purification methods as: -liquid-liquid extraction of Nb 2 O 5 with MIBK, chlorination of the oxide, distillation of NbCl 5 and thermal decomposition to metallic niobium, -molten salt electrolysis using LiF-NaF-KF melts containing K 2 NbF 7 , -iodination of Nb, distillation of NbI 5 /partial reduction/re-iodination/thermal decomposition to Nb, (2) Removal of volatile impurities by EBM or EBFZM in high or ultra high vacuum, (3) Decarburization by high temperature annealing under low O 2 partial pressure, (4) Removal of H, O and N by UHV degassing at high temperature. The various purification methods developed for ultra purification of Nb are described with special emphasis on investigations carried out to optimize the conditions of liquid-liquid extraction and molten salt electrolysis. Both processing routes allowed to produce Nb with W and Ta impurity concentrations in the ppb range and residual resistivity ratios R R R > 10000 (best value obtained was 90000). The superconductivity of Nb below the transition temperature T c = 9.288 K requires a special R R R measuring technique which will be described in the paper.

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“…Therefore, research and development efforts into niobium electrodeposition as a viable manufacturing alternative have intensified [8][9][10][11]. The melts made of chloride and fluoride salts were found to be suitable electrolytes for electrodeposition of niobium and some of its alloys [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Electrodeposition of Nb and Al from chloroaluminate melt on vitreous carbon

Vukićević¹,

Cvetković

Jovanović³

et al. 2016

Metall Mater Eng

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Niobium and aluminium were electrodeposited at 200 °C under argon atmosphere onto vitreous carbon from inorganic chloroaluminate melts (AlCl 3 +NaCl) with added niobium. Niobium was introduced into the electrolyte by anodic dissolution of metallic niobium or by chemical dissolution of Nb 2 O 5 in a melt of equimolar AlCl 3 +NaCl mixture. The processes of deposition/dissolution onto/from vitreous carbon were investigated by cyclic voltammetry and chronoamperometry. Characterization of the obtained deposits was done by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The only observed reduction processes on the working electrode in the potential window from 1.000 V to -1.000 V vs. Al, were individual niobium deposition and codeposition of niobium and aluminium with Al-Nb alloys formation.Electrodeposition of niobium from the chloroaluminate melt with added niobium (V) oxide seems to start at around -0.100 V vs. Al and at about -0.200 V vs. Al aluminium starts codepositing. During the codeposition Nb-Al alloys were formed. Niobium deposition starting potential from the electrolyte with niobium added by anodic dissolution starts at 0.100 V vs. Al, and aluminium codeposition starting potential was at around -0.025 V vs. Al, followed by Nb/Al alloy formation.

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The Electrodeposition of Coherent Deposits of Refractory Metals

Cited by 68 publications

References 0 publications

The Redox Chemistry of Niobium(V) Fluoro and Oxofluoro Complexes in LiF‐NaF‐KF Melts

The Redox Chemistry of Niobium(V) Fluoro and Oxofluoro Complexes in LiF‐NaF‐KF Melts

Preparation of Ultra High Purity Niobium

Electrodeposition of Nb and Al from chloroaluminate melt on vitreous carbon

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