Personne : Darvishi Alamdari, Houshang
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Darvishi Alamdari
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Houshang
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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
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ncf11847835
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Publication Accès libre Characterization of carbon anode protected by low boron level : an attempt to understand carbon−boron inhibitor mechanism(American Chemical Society, 2017-07-19) Ziegler, Donald Paul; Laroche, Gaétan; Lamonier, Jean-François; Darvishi Alamdari, Houshang; Ishak, RamziSeveral chemical reactions occur during the electrolysis of alumina in the Hall–Héroult process resulting in a significant overconsumption of the carbon anode. Carbon oxidation with oxygen is one of these reactions. The inhibition of this reaction by the application of protective layers on the anode can be an effective technique to reduce carbon consumption. Boron impregnation was shown to suppress this reaction. In this study, very low boron content has been impregnated on the anode, and several characterization methods have been performed to understand the protection mechanism of such a low boron concentration during the oxidation reaction of anodes. An air reactivity test of boron-impregnated anodes has been performed at temperatures between 400 and 600 °C. The samples were characterized using XPS, Raman spectroscopy, XRD, XRF, porosimetry, and thermogravimetric analysis (TGA). TGA revealed that the total number of interactions between oxygen atoms and carbon active sites was reduced, decreasing the pre-exponential factor. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) has been employed as a highly sensitive surface characterization method to identify chemical forms of boron on the anode. It has been confirmed that boron blocks active sites of carbon by creating boron–carbon bonds, thus reducing the interaction of carbon active sites with oxygen.Publication Accès libre Application of boron oxide as a protective surface treatment to decrease the air reactivity of carbon anodes(MDPI AG, 2017-03-03) Picard, Donald; Ziegler, Donald Paul; Laroche, Gaétan; Darvishi Alamdari, Houshang; Ishak, RamziThe oxidation of a carbon anode with air and CO2 occurs during the electrolysis of alumina in Hall-Héroult cells, resulting in a significant overconsumption of carbon and dusting. Boron is well known to decrease the rate of this reaction for graphite. In this work, the application of boron oxide has been investigated to evaluate its inhibition effect on the air oxidation reaction, and to provide an effective protection for anodes. Different methods of impregnation coating have been explored. Impregnated anode samples were gasified under air at 525 °C according to the standard measurement methods. X-ray tomography was used to obtain the microstructural information of the samples before and after air-burning tests. The impregnated samples showed a very low oxidation reaction rate and dust generation.