ISSN:
1572-8838
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Electrical Engineering, Measurement and Control Technology
Notes:
Abstract The partial dissolution of zinc from electrodeposited Ni-Zn alloys (withX Zn 0 =22–87.3 mol %) was studied, in cold and nearly boiling 10m KOH. It was found that alloys withX Zn 0 ≤22 mol % are not dissolved at all. The dissolved zinc fraction,A, increased rapidly with further increase in zinc content and after having passed a maximum withA=82–90% atX Zn 0 =55–58 mol % and a sharp minimum withA=52–65% atX Zn 0 =65–69 mol %, it asymptotically approached toA → 100% atX Zn 0 → 100 mol %. The discontinuous dependence ofA againstX Zn 0 may be explained by differences in the crystallographic composition of the alloy deposits. Alloys withX Zn 0 〈50–60 mol % can be allocated to solid solutions of zinc in the Ni matrix (α-phase); the range of 50–60〈X Zn 0 〈70–80 mol % corresponds to the coexistence of α+γ phases. The pure γ-phase exists within a narrow range atX Zn 0 =75–80 mol %. No zinc dissolution from Ni-Zn alloys withX Zn 0 ≤22 mol % was explained by extremely low zinc activities in dilute solid solutions of the α-phases shifting the Gibbs energy of the dissolution reaction to very low negative, or even to positive values. The dependence of the hydrogen and oxygen overvoltage atj=0.4 A cm−2 in 10m, KOH at 100°C on the original zinc contentX Zn 0 showed, in both cases, a clear minimum atX Zn 0 =75–78 mol %. This points to a practically pure γ-phase in the original Ni-Zn alloy with an approximate composition NiZn3.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01027498
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