La fabrication de l'aluminium par le procédé d'électrolyse nécessite l'utilisation des anodes. Or, la qualité des anodes a un impact direct sur le coût du métal, la consommation d'énergie et les émissions environnementales. Une liaison satisfaisante entre le coke et le brai affecte fortement les propriétés finales de l'anode. Une des avenues les plus prometteuses pour améliorer cette liaison est la modification des propriétés du brai. L'objectif de ce travail est d'améliorer la mouillabilité du coke par le brai en modifiant les propriétés du brai par l'ajout de produits chimiques. Des tensioactifs ou agents de modification de surface sont sélectionnés afin d'enrichir les groupements fonctionnels requis pour augmenter la mouillabilité. De plus, les additifs chimiques sont choisis en fonction de l'impact environnemental de même que l'impact économique de cet ajout d'additif pour l'industrie tout en prévenant la contamination des anodes. La méthodologie prévoit d'analyser la composition chimique des brais modifiés par la spectroscopie infrarouge a transformée de Fourier (FTIR) afin d'évaluer l'enrichissement des groupements fonctionnels requis. Puis, l'interaction du brai modifié en présence du coke est vérifiée par la méthode goutte-sessile afin d'en évaluer la mouillabilité du coke par le brai. Une amélioration de la mouillabilité signifie une possible amélioration de l'interaction entre les deux matériaux pouvant améliorer les propriétés anodiques. Dans cette étude, deux des additifs sélectionnés ont permis de démontrer une modification significative des propriétés du brai favorisant l'amélioration de la compatibilité du brai avec le coke.

Dans l'industrie de l'aluminium, les anodes sont utilisées afin de fournir le carbone nécessaire a la réduction électrolytique de l'aluminium. Toutefois, la compatibilité des matériaux de base est compromise par la qualité décroissante du coke et du brai nuisant a l'obtention des propriétés finales des anodes. L'objectif de ce travail est de vérifier si l'amélioration de la mouillabilité du coke par un brai modifié chimiquement peut contribuer a améliorer certaines des propriétés d'anodes. La méthodologie prévoit la fabrication d'anodes au laboratoire de carbone de l'UQAC a partir de brais modifiés a l'aide d'un additif chimique et la comparaison avec des anodes standards. Deux additifs chimiques ont été testés. Les anodes sont ensuite carottées et les échantillons sont caractérisés a l'état cru et cuit selon les normes appropriées. Dans cette étude, les deux additifs sélectionnés ont permis de démontrer une amélioration significative de certaines des propriétés des anodes.

In aluminum industry, it is important to determine the concentration of contaminants present in anode raw materials as rapidly as possible in order to adjust the anode recipe. Sodium, which is an impurity coming largely from anode butts, significantly influences the anode reactivity, and an increase in its concentration increases the anode consumption. A simple and inexpensive method was developed to quantify the sodium content in dry aggregates and anodes without grinding the samples. The method is based on potentiometric principles using a sodium-ion specific electrode. A sample can be analyzed easily within thirty minutes. In order to prevent the rapid degradation of the specific electrode due to experimental conditions, sodium is extracted from samples by electrophoresis prior to the test. The comparison shows that the measured sodium concentrations obtained are similar to the results determined by other test methods.

In aluminum industry, it is important to determine the concentration of contaminants present in anode raw materials as rapidly as possible in order to adjust the anode recipe. Sodium, which is an impurity coming largely from anode butts, significantly influences the anode reactivity, and an increase in its concentration increases the anode consumption. A simple and inexpensive method was developed to quantify the sodium content in dry aggregates and anodes without grinding the samples. The method is based on potentiometric principles using a sodium-ion specific electrode. A sample can be analyzed easily within thirty minutes. In order to prevent the rapid degradation of the specific electrode due to experimental conditions, sodium is extracted from samples by electrophoresis prior to the test. The comparison shows that the measured sodium concentrations obtained are similar to the results determined by other test methods.

Aluminum is one of the major industries in Canada. The main challenges facing the aluminum industry are carbon loss, energy use, greenhouse gas emissions, cell performance, and production costs, especially for high-amperage cells. The quality of carbon anodes plays a major role in the stability of cell operation and energy consumption. Anodes are made from petroleum coke, rejected green and baked anodes and butts, as well as coal tar pitch, which binds all of the particles. Although the industry depends on a steady supply of high-quality anodes, the availability of quality anode raw materials�coke and pitch�has decreased. A means of improving raw material quality is to modify their properties. In this work, using two additives, low-and high-quinoline insoluble (LQI and HQI) pitches were modified. These additives enrich the surface functional groups of the pitch, thereby increasing coke−pitch interactions. Various additive concentrations and pitch percentages were assessed. It is found that the choice of additive type has a marked effect on pitch properties, with different additives improving different pitches. Additive 1 is suitable for the HQI pitch, whereas additive 2 modifies the LQI pitch better. Anode properties are improved by modifying one of the pitches, whereas modifying the other pitch affects the anode quality to a lesser extent. Thus, the results showed that the modification of an already good-quality pitch (LQI pitch) does not significantly affect the anode quality. On the other hand, the modification of the inferior-quality pitch (HQI pitch) improved the anode quality and decreased the optimum pitch percentage necessary to obtain good anodes compared to the percentage of the LQI pitch needed. This would help decrease the anode production cost. The wettability tests give an indication of if the additive has the potential to improve the coke−pitch interactions, but it cannot predict the effect of pitch percent.

Aluminium is produced by electrolysis using carbon anodes. These anodes are manufactured with dry aggregate (mainly calcined petroleum coke, butts, and rejected green and baked anodes) and coal tar pitch, which acts as a binder. Utilization of good quality anodes decreases the consumption of carbon and energy, hence the process cost as well as the emission of greenhouse gases (GHG). The interactions between coke and pitch play an important role in determining the anode quality. If they are compatible, pitch can penetrate into the pores of the coke particles as well as into the voids between the particles, resulting in denser anodes. One way to improve these interactions is to modify the chemical composition of pitch using an additive. The objective of this study is to investigate the effect of the pitch type on the effectiveness of pitch modification in improving the anode properties. Two types of pitch with different quinoline insoluble (QI) contents were used: one with high QI (HQI pitch) and the other with low QI (LQI pitch). They were modified using the same additive. The interactions between the pitches and the coke were studied by measuring the wettability of coke by the pitches. The pitch chemical composition was studied using FTIR and XPS. Then, anodes were produced and characterized. Their apparent density, electrical resistivity, air and CO2 reactivities, and permeability were compared. The results showed that the properties of anodes produced using modified HQI pitch were improved. Modifying LQI pitch did not significantly improve the anode properties.

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This paper presents an original piezoresistive strain gauge architecture based on two polysilicon layers able to sense in-plane strain. These gauges are electrically isolated from the external environment in order to be used in liquids. The presented design is based on three optimization keypoints, which one of these allows the reduction of the beam width thus leading to an increased sensitivity in force. Design, modelling, fabrication and characterization have been investigated. An in-plane sensitivity of 30x10 -6 µN -1 has been obtained which is comparable to out of plane sensitivity, typically obtained with AFM cantilevers.