Accelerated diffusion of hydrogen along grain boundaries in nickel

✍ Scribed by A.M. Brass; A. Chanfreau

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 991 KB
• Volume: 44
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/1359-6454(95)00446-7

✦ Synopsis

Accelerated diffusion of hydrogen was observed at room temperature in polycrystalline nickel samples with the electrochemical permeation technique. A larger hydrogen flux was measured in annealed samples with 25 pm grain size whereas faster hydrogen diffusion was observed at the early stage of the permeation process in samples with a larger grain size (150 pm). The large flux in the small grain material is attributed to the contribution of the grain boundaries to the total hydrogen flux. The influence of grain boundaries is limited to the near room temperature range as shown by comparison of permeation data obtained at 293 and 373 K. When compared to lattice diffusivity, the increase in the diffusion coefficient of hydrogen (computed with Fick's solutions for intergranular diffusion or from the permeation flux at steady state) due to short path diffusion of hydrogen along grain boundaries is of the order of 2-7.

Furthermore, short circuit diffusion is probably minimized by trapping effects.