Journal of The Surface Finishing Society of Japan
Online ISSN : 1884-3409
Print ISSN : 0915-1869
ISSN-L : 0915-1869
Research Papers
Diffusion behavior of hydrogen in Nickel films electrodeposited from Watt's solution with and without thiourea
Ryo SHIMAKITAMai KOMORISatoshi OUEYu-ki TANINOUCHIMakoto AKAHOSHIHiroaki NAKANO
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2025 Volume 76 Issue 10 Pages 465-472

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Abstract

This study investigated diffusion behaviors of hydrogen in Ni films that had been electrodeposited from Watt's solutions with and without thiourea addition. Ni films with 100 μm thickness were obtained by physical exfoliation from the titanium substrate after electrodeposition at 500 A・m−2 and 333 K in unagitated solutions. Hydrogen permeation measurements were taken using the Devanathan-Stachurski double cell technique. The hydrogen flux at a steady state in the electrodeposited films, irrespective of thiourea addition in the plating solution, was greater than that in Ni films prepared by cold-rolling. The Ni crystal grain size in the electrodeposited films was less than those in the rolled films, which suggests that the primary diffusion path of hydrogen in the electrodeposited Ni is the grain boundary. Comparison of the microstructures and hydrogen permeation behaviors among electrodeposited Ni films shows that thiourea addition in Watt's solution reduces the Ni grain size and decreases the apparent diffusion coefficient of hydrogen. Co-deposition of S with Ni was observed in films deposited from the thiourea-added solution, which is apparently a major reason for hydrogen's lower diffusion coefficient. Unlike earlier studies, the hydrogen flux at a steady state in Ni films deposited from the thiourea-added solution was greater than that deposited from the thiourea-free solution. This greater flux is attributed to the effect of the increased hydrogen permeation paths: refinement of crystal grains with thiourea has a greater effect than that of the decreased diffusion coefficient.

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