A study of cathode improvement for electro-deoxidation of Nb2O5 in a eutectic CaCl2–NaCl melt at 1073K

Xu, Qian; Deng, Liqin; Wu, Yan; Ma, Tao

doi:10.1016/j.jallcom.2005.01.002

Cited by 55 publications

(34 citation statements)

References 6 publications

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“…The difference between the morphologies of the electroreduction-generated dendritic iron crystals and the initial Fe 2 O 3 powder suggests that the dissolution of Fe 2 O 3 may occur during the electroreduction process. [14] Actually, comparing to the typical current-time curves of the electrodeoxidation of solid oxides in molten salts, [9,24,27,28,53] the current-time curves shown in Figures 5, 8(a), and 11 display a small difference. The currents generated during the electrodeoxidation of solid oxides in molten salts generally increase to their maximum values and then decrease immediately.…”

Section: Solid State Electroreduction Mechanismmentioning

confidence: 95%

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Electroreduction of Iron(III) Oxide Pellets to Iron in Alkaline Media: A Typical Shrinking-Core Reaction Process

Zou

et al. 2015

Metall Mater Trans B

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Low temperature electrochemical reduction of iron(III) oxide to iron in a strongly alkaline solution has been systematically investigated in this article. The facile electrochemical process was carried out in 50 to 70 wt pct aqueous NaOH solution at 383 K (110°C) and 1.7 V. The preformed spherical Fe 2 O 3 pellets with porous structures were used directly as precursors for the electrolytic production of iron. The influences of the experimental parameters on the electroreduction process and the characteristics of the iron products as well as the reaction mechanisms were investigated. The results show that the precursor's pre-sintering process and the concentration of NaOH aqueous electrolyte have significant influences on the electroreduction process. The electroreduction-generated spherical metallic iron layer comprising dendritic iron crystals is first formed on the surface of Fe 2 O 3 pellet precursor and then extends gradually into the pellet's interior along the radial direction. The electroreduction process is confirmed to be a typical shrinking-core reaction process. The direct solid state electroreduction mechanism and the dissolution-electrodeposition mechanism coexist in the electrochemical process. The experimental observations suggest that the dissolution-electrodeposition mechanism appears to be the dominant mechanism under the experimental conditions employed in this study. This facile process may open a new green electricitybased route for the production of dendritic iron crystals from iron(III) oxide in alkaline media.

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Section: Solid State Electroreduction Mechanismmentioning

confidence: 95%

“…[20][21][22][23][24][25][26][27][28][29][30][31][32] Moreover, the gaseous reduction of iron oxides to metal iron by hydrogen gas has also been recognized as an environmental friendly way. [33][34][35][36] However, high cost of hydrogen production is still a challenge for iron and steel industry.…”

Section: Introductionmentioning

confidence: 99%

Electroreduction of Iron(III) Oxide Pellets to Iron in Alkaline Media: A Typical Shrinking-Core Reaction Process

Zou

et al. 2015

Metall Mater Trans B

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“…The oxygen ions released from the cathode migrate to the graphite anode, where they react electrochemically with graphite to form carbon dioxide or carbon monoxide. The process was demonstrated for the production of many metals/semimetals, such as titanium, [9,12] chromium, [13,14] niobium, [15][16][17][18] and silicon. [19][20][21][22] An identical electroreduction process, but with molten lithium chloride containing 1 to 3 wt pct Li 2 O as the electrolyte (650°C) medium, has been studied for the reduction of uranium oxides by researchers at the atomic energy institutes in the United States, [23,24] South Korea, [25] and Japan.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Deoxidation of Solid Zirconium Dioxide in Molten Calcium Chloride

Mohandas

Fray

2009

Metall Mater Trans B

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The reduction of zirconium dioxide pellets by electro-deoxidation in molten calcium chloridecalcium oxide (900°C) has been studied. In this technique, the solid oxide is cathodically polarized against a graphite counter electrode under a constant applied potential. Unlike other metal oxides that have been reduced by this technique, only a small area around the cathodic current-collector wire was reduced to zirconium metal with zirconia pellets sintered at~1100°C; the rest of the sample was largely calcium zirconate. Pellets sintered above 1200°C showed better reduction near the cathode wire and the reduction extended to the entire surface of the pellet with the passage of time. However, reduction of the inner core was found to be increasingly difficult, because the surface metal layer thickened on continuous electrodeoxidation. An analysis of the experimental results showed that the poor electrical conductivity of the intermediate compound, CaZrO 3 and its blocky morphology inhibited the electrodeoxidation process. The increase in the sintering temperature of the pellet made it better conducting. However, the pores formed in the thick zirconium metal layer in such samples were too small for an ideal contact between the inner core and the molten electrolyte and hence the reduction of the inner core remained incomplete. Within the scope of this study, it is concluded that preforms with good grain growth and porosity are necessary for the electro-deoxidation of solid zirconium oxide.

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“…Previous work has investigated the current ef ciency for the FFC Cambridge process as a function of the electrolysis time, sintering conditions used for the cathode metal-oxide pellet, cell voltage, the molten salt temperature, and the anodic variables [8][9][10][11][12] . The results of the studies show that the current ef ciency can be improved by optimization of the electrolysis time, sintering conditions, cell voltage, the temperature and the inert anode.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Changed Electrolytic Cell on the Current Efficiency in FFC Cambridge Process

Bai

et al. 2017

Mater. Trans.

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Low current ef ciency of the FFC Cambridge process made it no obvious advantages in cost compared with the traditional process to produce metals. Effect of the changed electrolysis cell on the current ef ciency has been studied. Put the cathode into an alumina tube with a hole can ef ciently avoid short circuit and the cathode contaminated by carbon produced from graphite anode. The results show that the current ef ciency can be improved greatly by reducing the electric eld intensity in the electrolysis cell. The high background current is mainly caused by the electronic conductivity in the electrolysis cell. Otherwise, pollution of the cathode is avoided, the depletion of the anode sharply decreases and the deoxidation of the samples greatly improve when using the improvement electrolysis cell.

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A study of cathode improvement for electro-deoxidation of Nb2O5 in a eutectic CaCl2–NaCl melt at 1073K

Cited by 55 publications

References 6 publications

Electroreduction of Iron(III) Oxide Pellets to Iron in Alkaline Media: A Typical Shrinking-Core Reaction Process

Electroreduction of Iron(III) Oxide Pellets to Iron in Alkaline Media: A Typical Shrinking-Core Reaction Process

Electrochemical Deoxidation of Solid Zirconium Dioxide in Molten Calcium Chloride

Effect of the Changed Electrolytic Cell on the Current Efficiency in FFC Cambridge Process

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