Hydrogenation and dehydrogenation properties for DyNi5–H system

Senoh, Hiroshi; Takeichi, Nobuhiko; Tanaka, Hideaki; Kiyobayashi, Tetsu; Toyouchi, Masaru; Takeshita, Hideki; Oishi, Takao; Kuriyama, Nobuhiro

doi:10.1016/j.jallcom.2004.05.087

Cited by 6 publications

(12 citation statements)

References 10 publications

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“…This may be related to the disappearance of the second plateau in the SmNi 5 -H and GdNi 5 -H systems at high temperature. Figure 3 shows the relationship between the hydrogen plateau pressures observed on the hydrogen desorption of P-C isotherm in RNi 5 -H systems 7) and the unit cell volumes of the RNi 5 alloys and phases. The fact that the logarithmic pressure of the first plateau is empirically proportional to the unit cell volume of the alloy (or of the phase) is well known.…”

Section: Resultsmentioning

confidence: 99%

“…6,7) The sample ingots were sieved down to 75 mm and mixed with 10 mass% Si fine powder to calibrate the X-ray diffraction angle. The mixtures were then activated several times under 9.5 MPa of hydrogen and cooled down to 196 K. Prior to the XRD measurement, the fully hydrided samples were exposed to acetone at the same temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Although the phase with hexagonal structure in the PrNi 5 -H system is similar to that in the LaNi 5 -H system, the structure of the phase in the PrNi 5 -H system is classified as C-centered monoclinic lattice. In the other RNi 5 -H system (R = Nd, Sm, and Gd) with two plateaux on the P-C isotherm 6,7) the structure of the hydrides, especially of the phase, remains unknown due to high plateau pressures.…”

Section: Introductionmentioning

confidence: 99%

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Structural Changes in RNi5-H (R = Pr, Nd, Sm and Gd) Systems with Two Hydrogen Pressure Plateaux

2004

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Pressure-composition (P-C) isotherms of RNi 5 -H (R = Pr, Nd, Sm and Gd) systems show two hydrogen pressure plateaux during hydrogen absorption and desorption. These correspond to the transitions among three phases: one hydrogen solid solution ( phase; RNi 5 H $0:5 ) and two hydrides ( phase; RNi 5 H 3$4 and phase; RNi 5 H 5$7 ). To explore the mechanism of the phase transitions, we investigated the structural changes in RNi 5 -H systems with ex-situ XRD. During hydrogen desorption, the ex-situ XRD profiles show that the crystal structures in RNi 5 -H systems change from hexagonal ( phase) through monoclinic ( phase) to hexagonal ( phase). The temporary decrease in structural symmetry may be due to hydrogen occupation except in the basal plane of the crystal structure. Lattice expansion between the and phases normalized in the monoclinic structure decreases slightly with the increasing atomic number of R in RNi 5 -H systems. Similarly to the correlation between the first plateau pressure and the unit cell volume of the phase, the second plateau pressure is logarithmically related to the unit cell volume of the phase. As far as the RNi 5 -H (R: from La to Gd except Ce) system is concerned, we can empirically predict the second plateau pressure as well as the first plateau pressure from the unit cell volume of the alloys.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Changes in RNi5-H (R = Pr, Nd, Sm and Gd) Systems with Two Hydrogen Pressure Plateaux

2004

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“…Instead of the disappearance of these well-known plateaux, a novel plateau appears at low hydrogen content in TbNi 5 Dy, 12) Ho and Y) systems at 248 K.…”

Section: Resultsmentioning

confidence: 92%

“…This corresponds to a decrease in ÁH value (TbNi 5 -H: À12:8 AE 0:2 kJ mol À1 ; DyNi 5 -H: À15:3 AE 0:8 kJ mol À1 , during absorption). 11,12) Hysteresis between absorption and desorption remained constant.…”

Section: Resultsmentioning

confidence: 99%

Appearance of a Novel Pressure Plateau in RNi5-H (R = Rare Earth) Systems

et al. 2005

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We investigated the hydrogen storage properties in a HoNi 5 -H system combined with TbNi 5 -H and DyNi 5 -H systems. Pressurecomposition (P-C) isotherms in the HoNi 5 -H system show one reversible pressure plateau during hydrogen absorption and desorption with a hysteretic phase transition. The maximum hydrogen storage capacity was found to be H/HoNi 5 ¼ ca. 2, and no second plateau similar to that observed in other RNi 5 -H (R: rare earth) systems was observed, even at 196 K. Two pressure plateaux found in light rare earth-based R L Ni 5 -H (R L ¼ La, Pr, Nd, Sm and Gd) systems tend to disappear in TbNi 5 -H and DyNi 5 -H systems and are scarcely present in HoNi 5 -H system. On the other hand, a novel pressure plateau appears at low hydrogen content in these systems due to the presence of a new hydride phase, and the plateau region extends from TbNi 5 -H and DyNi 5 -H to HoNi 5 -H systems. Contrary to the other plateaux, the pressures of the novel plateau during both hydrogen absorption and desorption decrease with decreasing unit cell volume of RNi 5 compounds or with increasing atomic number of the R element in RNi 5 -H systems. To clarify the effect of 4f electrons in the R element in RNi 5 -H systems on the novel plateau, we have evaluated the hydrogen storage properties in an YNi 5 -H system. Our results show that YNi 5 compound with lattice constants similar to those of TbNi 5 and DyNi 5 compounds has a similar P-C isotherm, suggesting that 4f electrons has no direct influence on the appearance of the novel plateau.

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Thermodynamic Properties of AB5 compounds

Joubert

2018

Hydrogen Storage Materials

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Hydrogenation and dehydrogenation properties for DyNi5–H system

Cited by 6 publications

References 10 publications

Structural Changes in RNi<SUB>5</SUB>-H (R = Pr, Nd, Sm and Gd) Systems with Two Hydrogen Pressure Plateaux

Structural Changes in RNi<SUB>5</SUB>-H (R = Pr, Nd, Sm and Gd) Systems with Two Hydrogen Pressure Plateaux

Appearance of a Novel Pressure Plateau in RNi<SUB>5</SUB>-H (R = Rare Earth) Systems

Thermodynamic Properties of AB5 compounds

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