Impedance spectroscopy study of nickel electrodeposits

• Published in: Materials letters 2002-03, Vol.53 (1), p.91-101
• Main Authors: Karayianni, H.S, Patermarakis, G.S, Papaioannou, J.C
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical and electrochemical properties; Chemistry; Cross-disciplinary physics: materials science; rheology; Electrochemistry; Electrochemistry and electrophoresis; Electrodeposition, electroplating; Exact sciences and technology; General and physical chemistry; Hydrogen hopping/diffusion conduction mechanism; Impedance spectroscopy; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Microstructure model; Miscellaneous (electroosmosis, electrophoresis, electrochromism, electrocrystallization, ...); Nickel electrodeposits; Physics
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/S0167-577X(01)00459-1

Nickel electrodeposits prepared in NiSO 4 and NiCl 2 electrolytes with thicknesses of 43–49.4 μm were examined by the impedance spectroscopy (IS) method for a–c frequencies 1 Hz–100 kHz. The Nyquist diagrams were single, almost perfect semicircles, suggesting the applicability of the in parallel combination of the R a– C a elements characterised by a single relaxation time, 8.27×10 −6 s, combined in series with another R b element, R b≪ R a. This relaxation time predicted that the incorporated hydrogen atoms are involved in the process of conduction by a hopping/diffusion mechanism, which is differentiated in the cases of NiSO 4–Ni and NiCl 2–Ni deposits. The diffusion coefficient of hydrogen, 1.25×10 −11 cm 2 s −1, was determined. The microstructure of Ni electrodeposits was also studied and characterised by electron microscopy. Finally, a general model for the microstructure of Ni electrodeposits, consistent with the results of impedance spectroscopy, was formulated.