STABILITY OF THE HYDROGEN ABSORPTION AND DESORPTION PLATEAUS IN LANI5-H .4. THERMAL HISTORY EFFECTS

Citation
Ce. Buckley et al., STABILITY OF THE HYDROGEN ABSORPTION AND DESORPTION PLATEAUS IN LANI5-H .4. THERMAL HISTORY EFFECTS, Journal of alloys and compounds, 231(1-2), 1995, pp. 460-466
Citations number
21
Categorie Soggetti
Chemistry Physical","Metallurgy & Metallurigical Engineering","Material Science
ISSN journal
09258388
Volume
231
Issue
1-2
Year of publication
1995
Pages
460 - 466
Database
ISI
SICI code
0925-8388(1995)231:1-2<460:SOTHAA>2.0.ZU;2-X
Abstract
We consider the effects of elevated (uniform) temperatures on the pres sure hysteresis of LaNi5-H, concentrating on two main aspects: (i) pro motion of gamma-phase formation and (ii) annealing effects. Hysteresis data taken at temperatures up to 110 degrees C and at 30 degrees C af ter annealing at temperatures up to 400 degrees C are presented and di scussed. A strictly ascending sequence of measuring and annealing temp eratures was employed. From the discontinuities in the absorption and desorption plateaux, the formation of the gamma phase at 90 degrees C in absorption and 60 degrees C in desorption was inferred. Both these temperatures are lower than in the original studies during an ascendin g temperature sequence. Critical perusal of published data suggests th at detailed thermal history, rather than measuring temperature: determ ines the temperature at which the gamma phase appears. Hydrogen cyclin g at 110 degrees C caused the gamma phase to also form during the imme diately following absorption-desorption cycle executed at room tempera ture. It is tentatively proposed that the microstructural modification required to form the gamma phase at room temperature is an ordering o f dislocations.