Closure to “Discussion of ‘Anodic Dissolution of Beryllium in Anhydrous Media’ [H. Aida, I. Epelboin, and M. Garreau (pp. 243–248, Vol. 118, No. 2)]”

Aida, H.; Epelboin, I.; Garreau, M.

doi:10.1149/1.2407879

Cited by 7 publications

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“…In summary, the results of this study provide direct evidence (optical) for the existence of anodic disintegration during polarization of Be in aqueous and nonaqueous media in accord with Aida et al (10). Cyclic voltammograms obtained for Be in LiC1/MeOH and NaNOJMeOH do not show peaks corresponding to two oxidation states, although this observation does not rule out the presence of a short-lived univalent ion.…”

Section: Discussionsupporting

confidence: 79%

“…One indication of the possible formation of Be(I) is the increased current efficiency for the process as well as the difference between the first and second ionization potentials (11). However, the concept of monovalent ions cannot account for the formation of Be particles in the anolyte unless a disproportionation reaction like 2Be(I) --> Be(II) -t-Be [3] is postulated (10,12,13). The source of Be particles, however, in the anolyte has been established clearly as arising from spalling of the electrode as evidenced by the presence of deformation twins on the anode as well as in the anolyte residue (7,14).…”

Section: Discussionmentioning

confidence: 99%

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Polarization Characteristics and Anodic Disintegration of Beryllium in Nonaqueous Solutions

Vaidyanathan

Straumanis

James

1974

J. Electrochem. Soc.

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Anodic polarization of Be in both aqueous and nonaqueous media leads to a spalling or disintegration of the anode. The disintegration product is composed of shiny, metallic, crystalline particles embedded in a white brittle mass [BoO and/or Be(OH)2] as viewed under an optical microscope. Microstructural studies using scanning electron microscopy provide further proof for the nature and identity of the Be particles. Valency determinations from weight loss measurements give values between 0.34 and 1.75. These anomalous values are attributed to the production of Be by anodic disintegration rather than to a disproportionation reaction of monovalent Be. The "apparent" valency appears to be more a function of the nature of the anion than of the solvent. The apparent valency approaches 1.0 in LiC104/EtOH and KC1/aq and is fractional in LiC1/MeOH. Beryllium is passivated both in aqueous and nonaqueous media containing NO3-ions. Beryllium passivated in NaNOs/ MeOH has no electronic conduction; the surface when examined optically appears dark with shiny Be crystals on it. Thus anodic disintegration occurs even at potentials where passive oxides predominate on the surface.The seeming inapplicability of Faraday's law for the anodic dissolution of Be, Zn, Mg, A1, etc. has led to several inquiries into the fundamental aspects of uncommon valency (1-4). The formation of univalent cations as the first stage during anodic dissolution is partly accepted in the case of A1, In, etc. (5, 6 (DMF). Anodic disintegration studies in this laboratory were supplemented with microstructural studies using an optical microscope in the past. The preset%t study utilizes a scanning electron microscope also, which has a high resolution and large depth of focus. ExperimentalThe Be anodes had a purity greater than 99.00%. Circular disks of Be were machined, polished with emery paper, cleansed in an ultrasonic cleaner, degreased with CC14 and acetone, and dried in a desiccator. A specially constructed Teflon holder was used to hold these leak-proof Be disks in the electrolyte. The nonaqueous solvents methanol, ethanol, and dimethyl formamide were 99.9% pure. They were purified further by using Davison Type 4A molecular sieves. Valency determinations were carried out as described earlier (8). Prepurified N2 provided an inert atmosphere in the electrolysis cell. The water content of the electrolyte was determined at the end of each valency study by Karl-Fisher titrations.Several potential sweep experiments were carried out. Though a steady-state galvanostatic study is extremely simple the potential sweep method enables the evaluation of current density at all potentials within the range of interest and hence the pursuit of passivation stages in the reaction. A Wenking potentiostat externally modulated by an Elron function generator was used. The cyclic current (i) vs. After each valency study, the polarized electrodes were washed with methanol and dried. These were then used for optical and scanning electron microscopic (SEM) studies. In ce...

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Polarization Characteristics and Anodic Disintegration of Beryllium in Nonaqueous Solutions

Vaidyanathan

Straumanis

James

1974

J. Electrochem. Soc.

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“…In summary the study provided direct evidence for the existence of anodic disintegration during polarization of Be in aqueous and nonaqueous media, in accord with Aida et al 73 Cyclic voltammograms did not exhibit peaks corresponding to two oxidation states, although this observation did not rule out the presence of short-lived Be (I). In the specific instance of the anodic polarization of Be in tiCl/MeOH (za = 0.34) and the accompanying disintegration, the univalent ion concept was ruled out.…”

Section: William J Jamessupporting

confidence: 84%

“…Indeed in their recent study of the anodic behavior of Be in anhydrous media Aida et al 73 have presented excellent SEM pictures which nicely document the origin of the metallic particles (Figs. 18-22), namely the anode surface.…”

Section: Discussionmentioning

confidence: 82%

“…In the specific instance of the anodic polarization of Be in tiCl/MeOH (za = 0.34) and the accompanying disintegration, the univalent ion concept was ruled out. The results of Aida et al,73 where specific potential regions were attributed to the occurrence of disintegration, were not borne out by the experimental i-E behavior, since disintegration was observed at all potentials.…”

Section: William J Jamesmentioning

confidence: 77%

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Anodic Dissolution of Metals—Anomalous Valence

James

1974

Advances in Corrosion Science and Technology

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INTRODUCTIONWhen metals are dissolved anodically in aqueous and nonaqueous media, the weight of metal dissolved is sometimes greater than that calculated from Faraday's law assuming normal oxidation states. Among several metals of industrial importance, AI, Be, Cd, Fe, Pb, Mg, Ti, and Zn exhibit this phenomenon. The usual implication is that these metals dissolve as ions with an ionic valence or oxidation number less than normal, e.g., Mg+, Be+, etc.Actually, anomalous anodic dissolution, i.e., that which results in a weight loss of an anode larger than that based on coulometric data, was first reported for Al over a century ago by its discoverers, Wohler and Buff. 1 Yet interestingly enough, despite the considerable research which has focused on this problem since that time, the exact nature of anomalous dissolution of metals remains in dispute.One mechanism which has received considerable support is the concept of univalent (unipositive) ion formation, sometimes referred to as the transitory ion mechanism.The unipositive (uncommon) ion mechanism has been especially espoused in large part by two major groups: Epelboin and co-workers at the University of Paris and Davidson, Kleinberg, and co-workers at the University of Kansas, Lawrence. The mechanism was first employed by Epelboin to explain the apparent valence of 1.40 for Zn dissolving anodically in aqueous perchlorate solution. 2 This value was obtained both from Straumanis, James, and co-workers at the University of MissouriRolla have attributed anomalous anodic dissolution of metals in aqueous solution, as have many other electrochemists, to the competition of secondary processes with an electrochemical oxidation step excluding that of transitory ion formation. They have explained the anomalous dissolution of many metals in aqueous media as arising from related phenomena: local action, film-controlled polarization, and anodic disintegration. The reader should be made aware that these phenomena often involve, but are not necessarily confined to, secondary processes frequently encountered in the electrochemistry of metals dissolving in dilute aqueous systems. Indeed, the major complaint of Epelboin is that too many electrochemists choose to confine their studies of anomalous anodic dissolution within the framework of classical electrochemistry. Despite the conflicting philosophies of the different approaches, considerable credit must be accorded to Epelboin and his colleagues in their extensive and well-planned efforts to come up with a universal and quantitative mechanism of anodic dissolution based on sound kinetic and thermodynamic principles.There is no argument that experimental and theoretical considerations of anomalous dissolution from existing and new points of view are essential to research and development with regard to corrosion protection and inhibition, batteries and other energy devices, electrochemical synthesis, and other associated electronic properties of interfaces. Accordingly, the following review is presented with the hope that it will ...

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