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Enthalpy data for the zirconium-hydrogen system
JOURNAL
OF NUCLEAR
MATERIALS
ENTHALPY
7, No. 3 (1902) 346-347,
DATA
FOR
THE
NORTH-HOLLAND
PUBLISHING
ZIRCONIUM-HYDROGEN
CO., AMSTERDAM
SYSTEM
D. G. WESTLAKE Metallurgy
Division,
Laboratory Argonne,
Argonne National Received
24 July
Libowitz 1) has summarized a few of the zirconium-hydrogen phase equilibria studies which are in the literature and presented thermodynamic data which the various authors obtained. The purpose of this letter is to provide a more nearly complete collection of enthalpy data which have been published, or which can be obtained from published experimental results. All the available information comes from pressure - composition - temperature (P - C - T) studies except for that obtained by Douglas 2) from heat content measurements. The form of the P-C isotherms is shown in fig. 1. Below the eutectoid temperature of 550’ C, P” increases linearly with C until the terminal solubility of hydrogen in alpha zirconium is reached. The pressure remains constant with increasing C over the entire alpha + delta-hydride composition range. The pressure increases again in the single phase delta range. Above 550” C, at the terminal solubility,
Ill.,
USA
1962
to form. When formation of the hydride is completed, the pressure rises again as the composition approaches ZrHs. The use of impure metal or failure to achieve equilibrium can alter the shape of the isotherms. For example, some studies of the zirconium-hydrogen system report no concentration ranges in which the pressure remains constant. The results of these studies are not included here. Enthalpies of the various reactions can be obtained from the P-C-T curves by plotting the results as indicated in table 1. The published enthalpy values are given in table 2 along with
Schematic
Fig. 1.
pressure-composition
beta
isotherms
zirconium begins to form and pressure remains constant in the alpha + beta range. The pressure increases again for single phase beta zirconium and becomes constant when delta-hydride begins
Zr-H
of the
system.
TA < Ts < 550’ C < Tc <
TD.
TABLE 1 Thermodynamic Composition
Pk. 1)
data yielded
by P-C-T
f Plotted
vs
results
Enthalpy
l/T
1nP
Partial
InC
Heat
of solution
1nP
Heat
of formation
1nP
Partial
1nC
Heat
of solution
InP hlP
Heat
of formation
Partial 346
d(f)
= R d(V)
molar heat of solution of d-hydride
of Hz. in c+Zr. in saturated
of S-hydride
molar heat of solution of &hydride
a-Zr.
from saturated
wZr.
of Ha in b-Zr. in saturated
of S-hydride
@--Zr.
from saturated
p-Zr.
molar heat of solution of Hr in a-hydride.
ENTHALPY
347
DATA
TABLE 2 Enthalpies Ref. ? 3) :;
of reactions in the zirconium-hydrogen
-
27.6
~- 15.7
6,
-
24.3-4
7) 8) g, 10) 11) 12) 13)
-
28.9
-
28.9
-
42.7
-
40.5B,n 39.6” 3.6E
-
41.7*
-
35.O*,F 30.8**G
-
45.8 43.5* 43.5*
-
43.0*
-
37.9*sn
+ 8.6
+ 8.6
I
Zip
f’H,-,d
A%p
system (kcallmole)
1 AH@+, 1
22,
-
50.7 49.6
-
45.15
-
53.2 50.8*
-
39.5X
-
52.0-4 50.1*
dH,C
- 38.2M
-- 39.6N + 2.3.4
I - 43.5*sL
+ 8.6
* Estimated by present author from published P-C-T B Estimated by Douglas from plots in 3) C Partial molar heat of solution of Hz in E-hydride. n H/Zr = 0.65 - 0.89 E H/Zr = 0.003 F H/Zr = 0.46
values which have been calculated
from published
P-C-T results. There appears to be fair agreement between the values from all the studies except on the partial molar heats of solution of hydrogen in the alpha, beta, and delta single phases. Sievert’s law holds for alpha solid solution so an, should not depend on concentration. This invariance was shown for concentrations up to H/Zr = 0.07 by Ells and McQuillan, while Gulbransen and Andrew 7) found only a slight variation. Therefore the low value of 15.7 kcal/mole cannot be explained on this basis. The value of AH, is a function of concentration e), but it seems doubtful that this could account for one value being an order of magnitude different from the others. All values of dH, are for the same small range of concentrations and should be nearly equal. Ref. 5) and 12) are the only two which reported observable changes in the shapes of the pressurecomposition isotherms caused by the deltahydride --f epsilon -hydride transformation. These changes are not depicted in fig. 1. The pressure did not remain constant in the (delta +
curves.
o H J K L M N
H/Zr H/Zr H/Zr H/Zr H/Zr H/Zr H/Zr
= = = = = = =
0.042 0.5 1.38 1.4 1.5 1.75 1.88 -
1.6 1.6 1.86 1.94
epsilon) phase region, and Libowitz 12) has explained that because of the martensitic transformation involved, this two phase region is not a true equilibrium in the classical thermodynamic sense. References 1) G. G. Libowitz, J. Nucl. Mat. 2 (1960) 1 2) T. B. Douglas, J. Am. Chem. Sot. 80 (1948) 5040
3, R. K. Edwards, P. Levesque and D. Cubiciotti, J. Am. Chem. Sot. 77 (1955) 1307
4, M. W. Mallett and W. M. Albrecht, J. Electrothem. Sot. 104 (1957) 142
5) D. F. Atkins, NAA-SR-4245
(Feb. 15, 1960)
Y C. E. Ells and A. D. McQuillan, J. Inst. Metals 85 (1956) 89
7, E. A. Gulbransen and K. F. Andrew, Trans.
AIME 203 (1955) 136 8) E. A. Gulbransen and K. F. Andrew, J. Electrothem. Sot. 101 (1954) 474 g, J. R. Morton and D. S. Stark, Trans. Faraday Sot. 56, part 3 (1960) 351-6 10) P. Gilbert, NAA-SR-1026 (1955) 11) L. D. LaGrange, L. J. Dykstra, J. M. Dixon and U. Merten, J. Phys. Chem. 63 (1959) 2035 12 G. G. Libowitz, J. Nucl. Mat. 5 (1962) 228 12 G. i)stberg, J. Nucl. Mat. 5 (1962) 208 1
OF NUCLEAR
MATERIALS
ENTHALPY
7, No. 3 (1902) 346-347,
DATA
FOR
THE
NORTH-HOLLAND
PUBLISHING
ZIRCONIUM-HYDROGEN
CO., AMSTERDAM
SYSTEM
D. G. WESTLAKE Metallurgy
Division,
Laboratory Argonne,
Argonne National Received
24 July
Libowitz 1) has summarized a few of the zirconium-hydrogen phase equilibria studies which are in the literature and presented thermodynamic data which the various authors obtained. The purpose of this letter is to provide a more nearly complete collection of enthalpy data which have been published, or which can be obtained from published experimental results. All the available information comes from pressure - composition - temperature (P - C - T) studies except for that obtained by Douglas 2) from heat content measurements. The form of the P-C isotherms is shown in fig. 1. Below the eutectoid temperature of 550’ C, P” increases linearly with C until the terminal solubility of hydrogen in alpha zirconium is reached. The pressure remains constant with increasing C over the entire alpha + delta-hydride composition range. The pressure increases again in the single phase delta range. Above 550” C, at the terminal solubility,
Ill.,
USA
1962
to form. When formation of the hydride is completed, the pressure rises again as the composition approaches ZrHs. The use of impure metal or failure to achieve equilibrium can alter the shape of the isotherms. For example, some studies of the zirconium-hydrogen system report no concentration ranges in which the pressure remains constant. The results of these studies are not included here. Enthalpies of the various reactions can be obtained from the P-C-T curves by plotting the results as indicated in table 1. The published enthalpy values are given in table 2 along with
Schematic
Fig. 1.
pressure-composition
beta
isotherms
zirconium begins to form and pressure remains constant in the alpha + beta range. The pressure increases again for single phase beta zirconium and becomes constant when delta-hydride begins
Zr-H
of the
system.
TA < Ts < 550’ C < Tc <
TD.
TABLE 1 Thermodynamic Composition
Pk. 1)
data yielded
by P-C-T
f Plotted
vs
results
Enthalpy
l/T
1nP
Partial
InC
Heat
of solution
1nP
Heat
of formation
1nP
Partial
1nC
Heat
of solution
InP hlP
Heat
of formation
Partial 346
d(f)
= R d(V)
molar heat of solution of d-hydride
of Hz. in c+Zr. in saturated
of S-hydride
molar heat of solution of &hydride
a-Zr.
from saturated
wZr.
of Ha in b-Zr. in saturated
of S-hydride
@--Zr.
from saturated
p-Zr.
molar heat of solution of Hr in a-hydride.
ENTHALPY
347
DATA
TABLE 2 Enthalpies Ref. ? 3) :;
of reactions in the zirconium-hydrogen
-
27.6
~- 15.7
6,
-
24.3-4
7) 8) g, 10) 11) 12) 13)
-
28.9
-
28.9
-
42.7
-
40.5B,n 39.6” 3.6E
-
41.7*
-
35.O*,F 30.8**G
-
45.8 43.5* 43.5*
-
43.0*
-
37.9*sn
+ 8.6
+ 8.6
I
Zip
f’H,-,d
A%p
system (kcallmole)
1 AH@+, 1
22,
-
50.7 49.6
-
45.15
-
53.2 50.8*
-
39.5X
-
52.0-4 50.1*
dH,C
- 38.2M
-- 39.6N + 2.3.4
I - 43.5*sL
+ 8.6
* Estimated by present author from published P-C-T B Estimated by Douglas from plots in 3) C Partial molar heat of solution of Hz in E-hydride. n H/Zr = 0.65 - 0.89 E H/Zr = 0.003 F H/Zr = 0.46
values which have been calculated
from published
P-C-T results. There appears to be fair agreement between the values from all the studies except on the partial molar heats of solution of hydrogen in the alpha, beta, and delta single phases. Sievert’s law holds for alpha solid solution so an, should not depend on concentration. This invariance was shown for concentrations up to H/Zr = 0.07 by Ells and McQuillan, while Gulbransen and Andrew 7) found only a slight variation. Therefore the low value of 15.7 kcal/mole cannot be explained on this basis. The value of AH, is a function of concentration e), but it seems doubtful that this could account for one value being an order of magnitude different from the others. All values of dH, are for the same small range of concentrations and should be nearly equal. Ref. 5) and 12) are the only two which reported observable changes in the shapes of the pressurecomposition isotherms caused by the deltahydride --f epsilon -hydride transformation. These changes are not depicted in fig. 1. The pressure did not remain constant in the (delta +
curves.
o H J K L M N
H/Zr H/Zr H/Zr H/Zr H/Zr H/Zr H/Zr
= = = = = = =
0.042 0.5 1.38 1.4 1.5 1.75 1.88 -
1.6 1.6 1.86 1.94
epsilon) phase region, and Libowitz 12) has explained that because of the martensitic transformation involved, this two phase region is not a true equilibrium in the classical thermodynamic sense. References 1) G. G. Libowitz, J. Nucl. Mat. 2 (1960) 1 2) T. B. Douglas, J. Am. Chem. Sot. 80 (1948) 5040
3, R. K. Edwards, P. Levesque and D. Cubiciotti, J. Am. Chem. Sot. 77 (1955) 1307
4, M. W. Mallett and W. M. Albrecht, J. Electrothem. Sot. 104 (1957) 142
5) D. F. Atkins, NAA-SR-4245
(Feb. 15, 1960)
Y C. E. Ells and A. D. McQuillan, J. Inst. Metals 85 (1956) 89
7, E. A. Gulbransen and K. F. Andrew, Trans.
AIME 203 (1955) 136 8) E. A. Gulbransen and K. F. Andrew, J. Electrothem. Sot. 101 (1954) 474 g, J. R. Morton and D. S. Stark, Trans. Faraday Sot. 56, part 3 (1960) 351-6 10) P. Gilbert, NAA-SR-1026 (1955) 11) L. D. LaGrange, L. J. Dykstra, J. M. Dixon and U. Merten, J. Phys. Chem. 63 (1959) 2035 12 G. G. Libowitz, J. Nucl. Mat. 5 (1962) 228 12 G. i)stberg, J. Nucl. Mat. 5 (1962) 208 1