Journal of Applied Electrochemistry

, Volume 23, Issue 6, pp 662–668 | Cite as

Transition layer thickness in microlaminar deposits

  • A. R. Despić
  • T. LJ. Trišović
Papers

Abstract

A theoretical analysis was carried out on the change of composition of a deposit obtained by the dual pulse method of forming laminar metal foils, with transition from a low current to a high current pulse, both in the galvanostatic and the potentiostatic mode of deposition. It was shown that the existence of a transition layer of varying composition between a layer of pure metal 1 and a layer consisting predominantly of the metal 2 is an inherent consequence of the electrochemical process, primarily because of an induction period in the concentration polarization with respect to ions of metal 1. The importance of this transition layer increases as the thickness of the layers of the two metals decreases. Eventually this limits the possibility of obtaining a sharp boundary between the layers, when the nanometre region of layer thickness is reached. Equations are given for calculating the deposition current density and rate of stirring of the electrolyte which provide a deposit of a required level of metal 1 in the layer of metal 2, as well as a required sharpness of the boundary between two layers. Experimental proof of the correctness of the analysis was sought. It was found that significant changes in the properties of the deposit occur in the same range of layer thickness in which the transition of the composition takes places.

Nomenclature

αc,1, αac,2

transfer coefficient of the cathodic processes

C

interfacial capacitance

C1, C2

concentration of the ions of metals 1 and 2 at the interface r

C01, C02

concentration of ions of the metals 1 and 2 in solution

D1

diffusion coefficient for the diffusion of ions of the metal 1

Er,1,Er,2

reversible potentials of metals 1 and 2, respectively

F

the Faraday constant

J01,J02

exchange current density of the metals 1 and 2, respectively

M1,M2

atomic weights of the metals 1 and 2, respectively

ν

kinematic viscosity of solution

ϱ1, ϱ2

densities of the metals 1 and 2 respectively

υ

rotation speed (r.p.s.)

z

number of electrons exchanged in the deposition process

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Copyright information

© Chapman & Hall 1993

Authors and Affiliations

  • A. R. Despić
    • 1
  • T. LJ. Trišović
    • 1
  1. 1.Institute of Technical Sciences of the Serbian Academy of Science and ArtsBelgradeYugoslavia

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