Structure and selective anodic dissolution of?-brass

Vvedenskii, A. V.; Маршаков, И. К.

doi:10.1007/bf00727054

Cited by 4 publications

(14 citation statements)

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“…This is supported also by the calculations of the conditions of the appearance of nonlinear segments in the i Ag -t -1/2 dependences carried out for the mean lifetime of vacancies τ ᮀ and the formation rate constant of bivacancies k 2 given in Table 7. These conditions, which are of the following form [7]: k 2 N ᮀ (0)t ~ 1 (the formation of bivacancies) and t/τ ᮀ ~ 1 (the assimilation of vacancies by planar defects), are equally met. At the same time, a number of factors show that the situation with vacancy flows is oversimplified.…”

Section: Resultsmentioning

confidence: 98%

“…The mass transfer in a solid substitution solution is known to proceed via the mutual diffusion of atoms [11,13,14,29] and be accompanied by the shift of the alloy-electrolyte solution boundary and a decelerated relaxation of the nonequilibrium subsystem of vacancies [3,7,27,28].…”

Section: Resultsmentioning

confidence: 99%

“…The solution of the corresponding diffusion problem (model VII) given in [7] with no account for the surface roughness provides the following general expression for the current decay curve:…”

Section: Theoretical Analysismentioning

confidence: 99%

“…Considering the summary diffusion flow in the alloy as isotropic, in the first approximation, we assumed that D ef = D ᮀ , ef N ᮀ , where D ᮀ , ef and N ᮀ are the apparent diffusivity and the atomic part of monovacancies. 1 It is important that this relation is applicable also to nonequilibrium vacancies [12,13,[17][18][19], the main source of which in our case is supposedly the selective dissolution (SD) of silver [3,7,[20][21][22]. As the possible sinks of vacancies, we considered the formation of bivacancies in a quasi-chemical reaction ᮀ + ᮀ 2 ᮀ with a rate constant k 2 , as well as the assimilation of monovacancies by the linear and planar structure defects.…”

Section: Introductionmentioning

confidence: 99%

“…The most sensitive experimental techniques of studying the solid-phase diffusion kinetics of the alloy dissolution and determining the parameters of the nano-size diffusion zone are the transient electrochemical measurements, particularly chronoammetry [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Solid-Phase Diffusion at a Potentiostatic Dissolution of Silver Alloyed with Gold

et al. 2005

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In an acidic nitrate solution containing no less than 10 -4 mol/l Ag + , potentiostatic anodic dissolution of silver from its alloy with gold (up to 35 at. %) already in about 10 s is limited by the solid-phase mutual diffusion of the components. A number of diffusion-kinetic dissolution models taking into account contributions from the liquid-phase mass transfer, segregation in the surface layer, microroughness of the surface, shift of the alloy-solution interface, as well as the relaxation of nonequilibrium vacancies into a transient dissolution current are considered. The diffusivities and mutual diffusivities of the components, concentrations of nonequilibrium vacancies, and thickness of the diffusion zone estimated in terms of these models are compared. The effect of the overpotential and alloy composition is discussed. The main source of nonequilibrium monovacancies in the amount 14 orders as high as the equilibrium one is found to be the dissolution of silver. The efficiency of the sinks, among which the formation of bivacancies seemingly dominates, is not high, which predetermines the slowness of relaxation processes in the solid-phase diffusion zone. PROTECTION OF METALS Vol. 41 No. 4 2005 KOZADEROV et al .

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Theoretical Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solid-Phase Diffusion at a Potentiostatic Dissolution of Silver Alloyed with Gold

et al. 2005

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Solid-Phase Diffusion at a Galvanostatic Anodic Dissolution of Zn-Ag and Cu-Au Alloy

et al. 2005

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The ionization stages of copper and zinc at a galvanostatic anodic dissolution of Zn-Ag and CuAu alloys in acidic chloride environment are found to be electrochemically nonequilibrium. Selective dissolution of the alloys is limited by the transient mutual diffusion of components within a nonequilibrium surface layer. In terms of diverse theoretical models of the solid-phase mass transfer, the effects of the electrode surface microroughness, the apparent shift of the alloy-electrolyte interface boundary, and the relaxation of the vacancy subsystem are analyzed. The parameters of the diffusion layer, namely, its thickness, diffusivities, mutual diffusivities, and the over-equilibrium vacancy concentration were found. The latter characteristic is determined by the dissolution rate of the electrochemically negative alloy component, and, hence, the diffusivities and the Sand parameter of the diffusion kinetics substantially increase with an increase in the current density.

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10.1007/s11124-008-1002-1

2000

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Based on the model taking into account the appearance of a morphological instability and the evolution of a surface with time during the selective anodic dissolution of a homogeneous A-B alloy with the predominant content of the electrochemically negative metal A, equations for the critical potential E cr and overpotential η cr of the surface development are derived. Criteria of the nature of chemical hindrances of the selective dissolution in the over-critical range are formulated. The E cr and η cr values corresponding to the breakage of the morphological stability of the A-B alloy surface (with the atomic silver part X Ag = 0.65 to 0.95) in an acidic nitrate solution containing diverse amounts of silver ions ( 10 -4 to 10 -2 M) are experimentally found. The character of the effect of the atomic gold content in the alloy and the concentration of silver ions in the solution on η cr and E cr values of the alloys is determined. The nature of the kinetic limitations of the selective dissolution in the over-critical potential range is clarified. PACS numbers: 82.45.Q

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Structure and selective anodic dissolution of?-brass

Cited by 4 publications

References 3 publications

Solid-Phase Diffusion at a Potentiostatic Dissolution of Silver Alloyed with Gold

Solid-Phase Diffusion at a Potentiostatic Dissolution of Silver Alloyed with Gold

Solid-Phase Diffusion at a Galvanostatic Anodic Dissolution of Zn-Ag and Cu-Au Alloy

10.1007/s11124-008-1002-1

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