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7Hydrogen in metals and alloys
EQUILIBRIUM DEUTERIUM PRESSURE OVER PALLADIUM AND ITS ALLOYS
S. V. Dyomina, M. V. Glagolev, A. I. Vedeneev
Russian Federal Nuclear Centre — All-Russian Research Institute (RFNC-VNIIEF), 37 Mira pr., Sarov, Nizhniy Novgorod Region, 607188, Russia E-mail: demina@dep19.vniief.ru
The accumulation of hydrogen based on reversible sorption of hydride-forming metals is a widely used hydrogen storage method. One of the main requirements made for hydrogen sources for hydrogen energy is the release temperature, which, according to present-day concepts, shall not exceed 373 K [1, 2]. From this point of view, a number of alloys based on palladium are of interest.
As a result of studies performed, the equilibrium deuterium pressures over palladium (foil, powder) and alloys of Pd-In-Ru, Pd-Y(foil) proposed for use in [3] have been measured. Isotherms measured within the temperature range from 22 0C to 100 0C in the deuterium desorption process are given in Fig 1. The system of Pd-Y—D2 is characterised by the absence of the isotherm plateau. The deuteride isotherm for the alloy of Pd-In-Ru is characterised by the presence of a plateau, which extent is by ~ 40% less that that of the palladium deuteride plateau. The equilibrium pressure value for the alloy of Pd-In-Ru on the plateau is by 1,6 times less than that with palladium at the room temperature and equals to ~ 2,7 kPa (~ 20,5 mm of mercury column).
Based on isotherms measured, the dependencies of equilibrium desorption (sorption) pressure upon reciprocal temperature have been plotted. Fig. 2 shows such a dependence for the alloy of Pd-In-Ru with the content of deuterium in the alloy being 20 cm3/g (the plateau middle).
The temperature dependencies of equilibrium sorption and desorption pressures for the alloy deuteride have the following form: lgPabs(kPa)=6.66-1787.0/T; lgPdes(kPa)=7.49-2082.3/T.
Form the dependencies obtained, the mean enthalpy and entropy values have been calculated for the decomposition and generation of the Pd-In-Ru alloy deuteride:
AH, = 40 kJ/mole,
des.
AS = 105 J/mole-K;
des
AHabs
= 34 kJ/mole, ASabs= 89 J/mole-K respectively. The hysteresis phenomenon [4] being characterised by the ratio between the equilibrium sorption pressure (Pabs) and the equilibrium desorption pressure (Pdes) is inherent to the system studied, the same as to the majority of metal-hydride systems. The hysteresis effect of P, /P. at the deu-
J J abs. des
terium interaction with the alloy being investigated in the temperature range studied is within the limits of 1.1-1.6.
1,5
& i
0,5
-0,5
-1
-1,5
T
11 )0°C
75°C
5C v
21
d
0 5 10 15 20 25 30 35 40 45
Specific gas content, cm3/g
— Pd powder; --Pd foil; --foil of the Pd-In-Ru alloy
a) b)
Fig. 1. Isotherms of equilibrium pressure in systems: a) Pd-D, Pd-In-Ru-D; b) Pd-Y-D
ISJAEE Special issue (2003)
Second International Symposium «Safety and Economy of Hydrogen Transport»
IFSSEHT-2003
2
0-1------
2,8 3 3,2 3,4
1/T 103
0 — desorption -Q- — sorption
Fig. 2. Temperature dependence of equilibrium deuterium pressure over the alloy of Pd-In-Ru
References
1. Dresselhaus M. S., Williams K. A., Eklund P. A.C. //MRS Bulletin. -1999. -P. 45.
2. Tarasov B. P.//Int. Sci. J. Alternative Energy and Ecology. -2000. -Vol.1. -P. 168.
3. R. C. J. Wieleman, M. Doyle and I. R. Harris. A Comparison of the Permeability, Solubility, and Diffusion Characteristics of H and D in a Palladium-8% Yttrium and Palladium-25% Silver Solution Alloy. Zeitschrift fur Physikalische Chemie Neue Folge, Bd. 164, S. 797-802 (1989).
5. Kolachev B. A., Shalin R. E., Il'yn A. A. Reference Book. Alloys - hydrogen accumulators. Moscow, Metallurguia. 1995.
