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The electrochemical behaviour of polycrystalline silver electrodes in Na2CO3 solution and the effect of ClO− 4 ions (1999)

Ibrahim, Magdy A. M. ; Hassan, Hamdy H. ; Abd El Rehim, Sayed S. ; [et al.]

Springer

Journal of solid state electrochemistry 3 (1999), S. 380-386

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ISSN: 1433-0768

Keywords: Key words Silver electrode ; Sodium carbonate ; Sodium perchlorate ; Pitting corrosion

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The electrochemical behaviour of polycrystalline silver electrodes in Na2CO3 solutions was studied under potentiodynamic and potentiostatic conditions and complemented with X-ray diffraction analysis. Potentiodynamic E/i anodic curves exhibit active passive transition prior to an oxygen evolution reaction. The active region involves a small peak AI followed by a major peak AII before the passive region. Peak AI is assigned to the formation of an Ag2O layer while peak AII is due to the formation of an Ag2CO3 layer. The height of the anodic peaks increases with increasing Na2CO3 concentration, scan rate and temperature. The effect of increasing additions of NaClO4 on the electrochemical behaviour of Ag in Na2CO3 solutions was investigated. The perchlorate ions stimulate the active dissolution of Ag, presumably as a result of the formation of soluble AgClO4 salt. In the passive region, ClO− 4 ions tend to break down the dual passive film, leading to pitting corrosion at a certain critical pitting potential. The pitting potential decreases with ClO− 4 concentration. Potentiostatic current/time transients showed that the formation of Ag2O and Ag2CO3 layers involves a nucleation and growth mechanism under diffusion control. However, in the presence of ClO− 4 ions, the incubation time for pit initiation decreases on increasing the anodic potential step.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s100080050170

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Expansion of cavities in layered elastic system (1987)

Sayed, S. M. ; Hamed, M. A.

New York, NY [u.a.] : Wiley-Blackwell

International Journal for Numerical and Analytical Methods in Geomechanics 11 (1987), S. 203-213

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ISSN: 0363-9061

Keywords: Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Geosciences

Notes: Theoretical formulations to the problem of expansion of spherical and cylindrical cavities in a layered elastic system are presented. The medium surrounding the cavity is assumed to consist of several layers, and each is idealized as a linear elastic solid. The solutions are expressed in matrix forms and can be obtained using a programmable calculator. The developed solutions are of some importance in geomechanics. The spherical cavity solution can be used to compute the settlement of single axially loaded piles. The predicted settlement using the analysis outlined herein agrees reasonably well with one case of field measurements. The cylindrical cavity solution can be used to manifest the effect of disturbed mass at the cavity wall on the stress-strain and deformation characteristics of the intact mass.

Additional Material: 9 Ill.