Niobium plating processes in alkali chloride melts

Citation
B. Gillesberg et al., Niobium plating processes in alkali chloride melts, J APPL ELEC, 29(8), 1999, pp. 939-949
Citations number
16
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF APPLIED ELECTROCHEMISTRY
ISSN journal
0021891X → ACNP
Volume
29
Issue
8
Year of publication
1999
Pages
939 - 949
Database
ISI
SICI code
0021-891X(199908)29:8<939:NPPIAC>2.0.ZU;2-0
Abstract
Niobium deposits were prepared from alkali chloride melts on nickel and AIS I316 stainless steel substrates both by constant current and by pulse curre nt methods. The influence of electrolysis conditions on the nature, morphol ogy and purity of the deposits was investigated by X-ray diffraction, scann ing electron microscopy and energy dispersive X-ray analysis. No metallic n iobium was obtained at temperatures below 500 degrees C. At temperatures be tween 550 and 650 degrees C, the deposits were dendritic and non-adherent, whereas pure niobium layers could be obtained at 750 degrees C. Detailed an alysis showed that a large negative overpotential during the pulse current period lead to the presence of suboxides, such as Nb6O, in the metallic pha se. Suitable electrolysis conditions gave pure oxygen-free niobium. Cross s ection analysis showed that on nickel a thin layer of niobium-nickel alloy such as NbNi3, was formed at the metal interface. In contrast no alloys wer e detected at the niobium-stainless steel interface, where homogenous adher ent layers of thickness around 50 mu m were obtained.