The Mechanism of Electrolytic Rectification

Haring, H. E.

doi:10.1149/1.2779656

Cited by 43 publications

(16 citation statements)

References 2 publications

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“…From the frequency dependence study, Hoar and Wood were able to place the following values on the analog circuit shown in Figure 17 for a 15-ju porous oxide film formed at 20 V and immersed in nickel acetate at 19°: Cp = 0.39 /uF cm-2, Rp = 700 kO cm-2, R" = 25 O cm-2, C0 = 0.001 ixF cm-2, and R0 = 5 MO cm-2. Hence, below 104 Hz measuring frequency (ac techniques) the capacitance of unsealed porous films is then seen as equivalent to a barrier film whose thickness is also obtained from Cp. This capacitance Cp can be written as tA/4ird if the parallel-plate equation applicable to condensers is assumed valid.…”

Section: Electrical Characteristicsmentioning

confidence: 99%

Anodic oxide films on aluminum

Diggle¹,

Downie²,

Goulding³

1969

Chem. Rev.

1,173

844

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Section: Electrical Characteristicsmentioning

confidence: 99%

Anodic oxide films on aluminum

Diggle¹,

Downie²,

Goulding³

1969

Chem. Rev.

1,173

844

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“…And second, existence of P element in both the PEO coatings may be also helpful in decreasing the friction coefficient [14]. Finally, the lowest friction coefficient of Fe 3 O 4 coated sample may result from [15,16]. The uncoated Q235 substrate with low hardness was more easy to destroy, which exhibited a higher and unstable friction coefficient.…”

Section: Hardness and Wear Testsmentioning

confidence: 99%

In situ formation of low friction ceramic coatings on carbon steel by plasma electrolytic oxidation in two types of electrolytes

Wang¹,

Jiang²

2009

Applied Surface Science

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“…metal/oxide interface and within the oxide both play a part in controlling the ionic current flow (10)(11)(12)(13).…”

Section: (C )mentioning

confidence: 99%

Field Dependence of the Tafel Slopes for Formation of Anodic Oxide Films

Christov¹,

Ikonopisov²

1969

J. Electrochem. Soc.

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An explanation of the field dependence of Tafel slopes for formation of anodic oxide films is proposed on the basis of an earlier general consideration of charge transfer over potential barriers. An expression for the activation energy as a function of the field strength is derived which contains a quadratic term arising from the shifting of both the barrier top and the equilibrium position of the ion under the influence of the electric field. The treatment includes the usual parabolic approximation of a continuous potential-energy function in the regions of its maximum and minimum. A comparison with the experimental data for anodic oxidation of Ta, Nb, and A1 shows this approximation to be quite satisfactory. The theoretical expression permits the determination of the actual barrier parameters at a given field strength go near the experimental field range, as well as an extrapolation to zero field strength. This theory is applicable equally well to any possible mechanism of the current flow in the anodic formation of oxide layers.The growth of homogeneous oxide layers during anodization of film-forming metals such as A1, Ta, Nb, Zr, etc., in a suitable electrolyte is interpreted by passage of ions across the oxide, surmounting some potential energy barrier in their way. Measurable rates of growth require considerable electric fields (more than 10 6 v/cm)~ so that the ionic transitions can be considered to occur only in the direction of the field.On the basis of elementary kinetic considerations, one obtains the welt-known equation for ionic current densitywith the activation energy being a linear function on the field strengthwhere Wo is the activation energy in the absence of an external field (4 -~ 0), a the activation distance, and q the charge on the moving ion. The pre-exponential factor A has a different meaning depending on the assumptions for the kind and location of the potential barrier. In this respect, the various theories could be classified on the basis of the following three assumptions:(a). Internal control.--According to Verwey's model (1), the limiting factor is the rate at which ions move from one interstitial position to another. It was proposed later (2-4) that the high field produces Frenkel defects (pairs of interstitial cations and cation vacancies) by drawing out metal ions in interstitial positions. Recently, a new theory for the internal control was developed by Dignam (5) on the basis of a dielectric mosaic model of the anodic oxide film.(b). Interlace control.--Mott and Cabrera (6, 7) considered as rate determining the first barrier which metal ions have to surmount to enter the oxide. This was shown to be the case with anodization of sputtered tantalum films (8). Jukova and Odynec (9) assumed that the electrochemical reactions at the oxide/electrolyte interface play a certain role in the growth of nonporous anodic films as well. (c ). Internal-interface control.--That is an extensionof the mentioned models for including effects of space charge due to ions in transit, so tha...

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The Mechanism of Electrolytic Rectification

Cited by 43 publications

References 2 publications

Anodic oxide films on aluminum

Anodic oxide films on aluminum

In situ formation of low friction ceramic coatings on carbon steel by plasma electrolytic oxidation in two types of electrolytes

Field Dependence of the Tafel Slopes for Formation of Anodic Oxide Films

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