Hydriding and Dehydriding Kinetics of LaNi5 Mixed with Silicone Rubber

✍ Scribed by P.R. Bidez; A.J. Goudy; A. Zarynow

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 307 KB
• Volume: 47
• Category: Article
• ISSN: 0026-265X
• DOI: 10.1006/mchj.1993.1019

✦ Synopsis

(\mathrm{LaNi}{5}) powder was mixed with silicone rubber and coated onto the outside of a watercooled brass tube. The hydriding and dehydriding rates of this mixture were measured and compared at temperatures of (25,30,35), and (40^{\circ} \mathrm{C}). Experiments were designed so that, in all cases, the ratio of the equilibrium plateau pressure of the hydride to the opposing hydrogen gas pressure was the same. Under equivalent conditions, hydriding rates were somewhat faster than dehydriding rates. These rates, however, were significantly slower than those from powders of (\mathrm{LaNi}{5}) mixed with an inert matrix. This indicates that the silicone rubber retards hydriding and dehydriding kinetics. Desorption was a first-order process with an activation energy of (30 \mathrm{~kJ} / \mathrm{mol} \mathrm{H}_{2}), whereas the reaction mechanism for absorption was deemed to be complex. It was concluded that the rate-determining step is the rate of hydrogen diffusion through the rubber matrix. 1993 Academic Press, Inc.