(Co,Ni)O Coated Anodes for CO<sub>2</sub>-Free Al Production
Notice bibliographique
Résumé
Canadian aluminum production is an important source of greenhouse gases (GHGs) with 6 Mt of CO 2 eq emitted in 2017, which is equivalent to the amount of GHG generated annually by about 2 million cars. The current technology consumes carbon anodes during the electrolysis of aluminum to form CO 2 according to the overall reaction: Al 2 O 3 + 3/2 C = 2 Al + 3/2 CO 2 . The most effective solution would be to replace the consumable carbon anodes with so-called inert anodes that emit O 2 rather than CO 2 and that are based on the following overall reaction: Al 2 O 3 = 2 Al + 3/2 O 2 . This would reduce GHGs by 75 to 100% depending on the type of emissions (CO 2 , CF x , NO x , SO x , etc.). However, the design of inert anodes is a major challenge because of the severe conditions during aluminum electrolysis that require materials with excellent corrosion and thermal shock resistance while having the same adequate electrochemical properties [1]. Among inert anodes studied so far, Cu-Ni-Fe-based alloys appear to be the most promising owing to their ability to form a layer of nickel ferrite (NiFe 2 O 4 ) on the surface of the anode upon Al electrolysis [2-4]. This nickel ferrite has low solubility in a cryolithic medium. However, the formation of the nickel ferrite protective layer is slow and, depending on the experimental conditions, might not be formed fast enough to provide effective protection of the underlying substrate Cu-Ni-Fe alloy. One strategy to help in the formation of this layer is to coat the Cu-Ni-Fe alloy with a sacrificial layer that would be stable for a period long enough to allow the formation of NiFe 2 O 4 on the surface of the anode. In this context, the use of (Co,Ni)O-based protective coatings for metallic anode appears promising [5]. However, it is challenging to produce coherent and crack-free oxide layer as required for industrial Al production. A potentially relevant method to produce (Co,Ni)O coated inert anodes is by direct deposition of (Co,Ni)O oxide compounds by thermal spray techniques such as suspension plasma spray (SPS) and high velocity oxygen fuel (HVOF). They are well-established technologies for producing protective oxide coatings for various industrial applications ( e.g. gas turbines). Additionally, thermal spray could be used on Al production site to restore protective (Co,Ni)O coating on end-of-life inert anodes. As a first step toward this goal, single phase (Co,Ni)O powders with various Co/Ni ratios that could be used as raw materials for the thermal spraying of protective coatings onto Cu-Ni-Fe inert anodes have been produced [6]. The crystalline structure, thermal stability, electrical conductivity and solubility in cryolite media of the produced (Co,Ni)O powders are characterized depending on their Co/Ni ratio. Finally, selected (Co,Ni)O powders have been used as raw materials for the thermal spraying (HVOF and SPS) of protective coatings onto Cu-Ni-Fe inert anodes and the electrochemical behaviour of the coated inert anodes under Al electrolysis conditions is presented. References [1] I. Galasiu et al., Aluminium-Verlag, Düsseldorf (2007). [2]S. Jucken et al., Corr. Sci. (2019) 147: 321-329. [3]E. Gavrilova et al., Corr. Sci. (2015) 101: 105-113. [4] S. Helle et al., Corr. Sci. (2010) 52:3348-3353. [5] T. Nguyen et al., Light Metals (2006) 385-390 [6] S. Mohammadkhani et al., J Am Ceram Soc. (2019) 102: 5063– 5070
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,004 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».