Hydrogen behavior in bimetallic systems:permeation through thin metal films
The hydrogen permeation performances are presented for micron Mo, Ti, Nb, Zr, Cr, Ni, Cu, CuPd, TiN, and stainless steel films deposited on palladium from arc sputtered cathodes. Some physical mechanisms explaining anomalies behavior in above mentioned systems are suggested. In particular, it is sho...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Cite this: | Hydrogen behavior in bimetallic systems:permeation through thin metal films / G.P. Glazunov, E.D. Volkov, A. Hassanein // Вопросы атомной науки и техники. — 2000. — № 3. — С. 102-104. — Бібліогр.: 13 назв. — англ. |
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| author | Glazunov, G.P. Volkov, E.D. Hassanein, A. |
| author_facet | Glazunov, G.P. Volkov, E.D. Hassanein, A. |
| citation_txt | Hydrogen behavior in bimetallic systems:permeation through thin metal films / G.P. Glazunov, E.D. Volkov, A. Hassanein // Вопросы атомной науки и техники. — 2000. — № 3. — С. 102-104. — Бібліогр.: 13 назв. — англ. |
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| description | The hydrogen permeation performances are presented for micron Mo, Ti, Nb, Zr, Cr, Ni, Cu, CuPd, TiN, and stainless steel films deposited on palladium from arc sputtered cathodes. Some physical mechanisms explaining anomalies behavior in above mentioned systems are suggested. In particular, it is shown that extreme high hydrogen permeability in the Mo-Pd system is caused by enhancing of diffusion coefficient in the system with a large number of connected pores. Also the possible use of such systems for an active control of recycling and erosion processes are considered. In the frame of non-ideal plasma theory the mechanism is suggested of hydrogen high content (clusters) formation as the result of hydrogen plasma phase transitions in metal. The small hydrogen clusters can be condensed in metal lattice. The arising of the large ones is more probably around defects and in submicro- and micro-pores appearing under, for example, plasma or energetic particle irradiation.
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UDC 533.9
Problems of Atomic Science and Technology. 2000. N 3. Series: Plasma Physics (5). p. 102-104 102
HYDROGEN BEHAVIOR IN BIMETALLIC SYSTEMS:
PERMEATION THROUGH THIN METAL FILMS
G.P. Glazunov, E.D. Volkov, A. Hassanein*
Institute of Plasma Physics of NSC KhIPT, 61108 Kharkov,Ukraine, e-mail:
glazunov@ipp.kharkov.ua
*Argonne National Laboratory, Argonne, IL 60439, USA
The hydrogen permeation performances are presented for micron Mo, Ti, Nb, Zr, Cr, Ni, Cu, CuPd, TiN, and
stainless steel films deposited on palladium from arc sputtered cathodes. Some physical mechanisms explaining
anomalies behavior in above mentioned systems are suggested. In particular, it is shown that extreme high hydrogen
permeability in the Mo-Pd system is caused by enhancing of diffusion coefficient in the system with a large number
of connected pores. Also the possible use of such systems for an active control of recycling and erosion processes
are considered. In the frame of non-ideal plasma theory the mechanism is suggested of hydrogen high content
(clusters) formation as the result of hydrogen plasma phase transitions in metal. The small hydrogen clusters can be
condensed in metal lattice. The arising of the large ones is more probably around defects and in submicro- and
micro-pores appearing under, for example, plasma or energetic particle irradiation.
INTRODUCTION
Numerous investigations of hydrogen behavior in
different materials and in plasma device volume were
carried out in order to get possibility of active control of
hydrogen isotope recycling process. The studies of
materials, coated by thin films are very important part of
such investigations due to high efficiency of such
systems for hydrogen kinetics control. On the other
hand, taking into account redeposition processes under
plasma-materials interactions in plasma devices,
knowledge of hydrogen behavior performances of thin
metallic films, in particular, of hydrogen permeability at
low pressure, is necessary for control of hydrogen
isotope recycling and inventory, estimation of
construction material state, etc. The bimetallic system,
which consists of a rather thick (0.1-0.5 mm) Pd-
substrate and a thin (1-10 µm ) film, deposited on its
surface is very convenient for measuring of hydrogen
permeability characteristics of thin films. Really, the
probability of hydrogen molecule penetration through a
thin film to palladium membrane in a single collision is,
in the most cases [1-3], essentially lower (usually in a
few times) than that for bare palladium. Hence, a
hydrogen permeability of such bimetallic system can be
often considered as the hydrogen permeability of film
only. Such bimetallic systems ( thin metallic film - Pd
substrate), placed inside a plasma device, could be used
for an active control of a hydrogen isotope density near
plasma facing surfaces, i.e. in order to perform some
kind of the gas puffing for the surface protection. On the
other hand, such systems could be used for high
hydrogen concentration buildup in the plasma facing
materials. As it was shown in recent work [4], the
possibility exists to decrease carbon erosion by
hydrogen shielding due to accumulation of high
hydrogen content at nearest surface bulk during special
regime of high-flux hydrogen ion bombardment. But it
is not clear if the similar mechanism can be realized for
metals. So, it was of a great interest also to consider the
possible mechanism of high hydrogen content buildup
in metallic (bimetallic) systems.
1. HYDROGEN PERMEABILITY
PERFORMANCES OF BIMETALLIC
SYSTEMS
A scheme of the experiments, experimental
procedures and results on the hydrogen permeability of
thin metallic films deposited from arc sputtered
cathodes on palladium were described in details in
previous paper [1-3]. Here are presented only some
results about relative hydrogen permeability j/j0 of films
and the activation energy of hydrogen permeability E
(Table) in order to discuss the possible use of such
bimetallic system for control of erosion and recycling
processes by high hydrogen content buildup in the
nearest surface bulk of plasma facing components.
Table. Relative hydrogen permeability and activation
energy of hydrogen permeability for metallic films
(0.133Pa, 873K).
Metal E, kJ/mole Em, kJ/mole j/j0, %
Ti 11 62.3 48
Zr 16.6 37.6 20
Nb 17.6 21.7 10
Ni 22.6 59.8 54
Stainless
Steel
19.9 71.1 25
Cr 26 19
TiN 15 9
Cu 46 47.6 5
CuPd+
Cu3Pd
9.2(<790K)
44 (>790K)
42
Mo 14.2 84.4 62
For comparison, the values of activation energy for
bulky metals Em [5] are presented in the Table, too.
As it is seen, the activation energies of permeability
for most films are in a few times lower than the
literature data for the bulky metals. This is due to a
high porosity of films which caused by a big difference
103
between substrate temperature (570K) and melting of
most deposited metals. In such situation the hydrogen
permeability of Mo-film can be more higher than that
for Ti or Ni, in spite of the fact, that in the hydrogen
permeability row of metals, Mo stay far behind Ti and
Ni (on the literature data base one can suggest such row
from high to low hydrogen permeation - Ti, V, Zr, Nb,
Ta, Fe, Ni, steel, stainless steel, Co, Cr, Al, Cu, Mo, Ag,
Pt, W). This fact can be easily explained in the frame of
model of anomalies diffusion in the system with the net
of connected pores [6], when hydrogen diffusion
coefficient increases in two orders of value. Such
phenomenon could be useful for creation of erosion
high resistible component with the use of diffusion
membrane coated by erosion high resistance material.
The possible model of such component is given in Fig.
1. The palladium (Ag-Pd alloys) is the unique material,
which can provide high hydrogen isotope concentration
and high hydrogen flows to protective layer. A potential
barrier on the boundary between film and Pd-substrate
might be easily overcome because hydrogen in
palladium is in atomized or partially ionized state,
similar to plasma state [7]. So, even films with the high–
energy hydrogen coupling (Ti, Nb, Zr) are not resistible
for hydrogen penetration from Pd. It must be noted that
not only metal films could be applied in such scheme
but nonmetal material too, e.g., carbon, carbides,
nitrides, etc. In the case of hydrogen recycling control
such scheme can provide different regimes: with high
recycling coefficient (gas puffing through membrane)
and with low recycling coefficient (hydrogen pumping
by membrane). In the latter air or oxygen must be
inputted instead of hydrogen.
So, the simple method exists to provide high
hydrogen flows to protective layer. But a physical
Fig. 1. The possible scheme of the high erosion
resistance plasma facing component.
mechanism of the attractive forces between hydrogen
atoms (ions) in metals providing the high concentration
phase (clusters) formation is not clear . In this paper
we make attempt to explain the process of the
hydrogen-cluster formation from point of view of
hypothesis of hydrogen plasma state in metals [7]
("metals" means in our case, mainly, palladium , as the
PdH -system is the most studied). Such point of view
permits the hydrogen-cluster formation not only in the
grain-boundaries, pores, but in metal lattice, too.
2. THE POSSIBLE MECHANISM OF THE
HYDROGEN-CLUSTERS FORMATION
The hydrogen (below it means all hydrogen isotopes
- protium, deuterium, tritium, if there are no special
reservations) concentration in metal n ~ p0.5, where p-
hydrogen pressure over metal surface. It means, that
hydrogen in metal volume is, at least, in atomic state.
What is more, the hydrogen gas in lattice can be
ionized, so the state similar to plasma state is possible.
The arguments in favor of such state are: the anomalous
high hydrogen diffusion coefficient in many metals,
what one can explain by small size of proton, the
disappearance of paramagnetism (when hydrogen
concentration increases to H/Pd ~ 0.65 the palladium
converts into the poor diamagnetic), the results of the
researches of positive muons in Pd, superconductivity of
PdH and electro-diffusion experiments /8/. So, we
suppose that the palladium lattice plays the role of
original ionizer and trap and then we consider the
hydrogen plasma performances without account of
plasma-lattice interaction.
In a general case the hydrogen plasma in metal
contains different particles, such as H+(proton), e-
(electron), H(atom), H-, H2
+, H2. For the concentrations
n > 1018 cm3 and temperature more than ≈1K there will
be only protons ( or D+, T+ ) and electrons in plasma, i.e.
the hydrogen plasma in metal is fully ionized. Really,
as it is seen in hydrogen phase diagram in Fig. 1, the
Mott criterion /9 / ( np = 1.2x1018 xT(K); rD =
(kT/4πe2 np )1/2 = 0.84rB , where np and nc - proton
concentration and critical density, accordingly; rD and
rB - Debye and Bor radiuses, accordingly), which
Fig. 2. The hydrogen plasma characteristics on
density-temperature coordinate plane: 1- electron
degeneracy line (neΛe
3=1); 1- Mott line (rD=0.84rB); 3-
proton degeneracy line (npΛp
3)
determines the hydrogen metal plasma transition to
stripped plasma state, is released at above mentioned
parameters (curve 2, fig.2). It was shown earlier [7] that
at 1 at the hydrogen pressure over palladium surface the
temperature of Mott transition is 520K that is near of
Plasma
Erosion high resistible
coating
Diffusion membrane
Hydrogen
Density, n (cm )-3
10
23
22
21
20
19
18
17
0 1 2 3 4
Temperature, T (K)
1
2
3
104
565K critical temperature of gas-liquid (also called α-β)
type phase transition in palladium.
During the Mott transition the more dense
hydrogen plasma "drops" (clusters) formation can begin
in any unit cell. The small clusters with ion number N
~ 12-100 appears (fig.3). The driving force for such
clusters formation can be the new phase additional
chemical potential ∆µ = ∆µe +∆µH , where ∆µe -is the
caused by electron Fermi-level change by plasma
electrons and ∆µH is caused by palladium lattice
distension ( it is known [8] that unit cell parameter for
palladium α-phase is ≈3.89A, and for β-phase ≈
4.025A), i.e. conditioned by the lattice elastic
deformation energy. The attractive mechanism between
protons, which is founded on ideas that the proton
deforms crystal lattice and creates the observed another
protons long-range deformation field, was given in [8].
The large hydrogen-clusters formation (N>100) is
possible both in lattice volume, and in regions of
defect accumulation (macro- and micro-pores,
dislocations, grain-boundaries, micro-cracks, etc.). The
former requires the certain conditions for point defect
(vacancies and host interstitial atoms) generation. The
irradiation by plasma and energetic particles can be,
for example, as the mechanism, providing hydrogen-
clusters formation conditions. In the latter the large
clusters are generated when hydrogen plasma condensed
in dense phase into
Fig.3. The small (1) and large (2) hydrogen-
clusters formation in metal.
micro-pores, micro-cracks, dislocations and grain-
boundaries. According to Lifshits-Sljozov-Wagner
diffusion coalescence theory [10-12] there are only
pores with sizes more than Rc >((nv/∆nv )/2γ(A/kT) in
metals, where A is the atomic volume, γ is specific
surface energy, nv is vacancy concentration, ∆nv -
vacancy supersaturation, Rc – the critical radius of pore.
The pores with the sizes smaller than Rc dissolve and
move to larger pores or micro-cracks, grain-boundaries
and dislocations, forming the pores chains [8]. The
condensation of the dense hydrogen plasma into such
micro- and submicro-pores causes the large hydrogen-
clusters formation. In very large pores hydrogen clusters
may be destroyed, forming molecular gas. As the
impurities segregation on pores boundaries is usually
observed, the hydrogen back dissociation and sorption
by metal is difficult, the conditions for hydrogen
permeation into pores and back are asymmetric, so
hydrogen pressure in pores can achieve high values (
according to dates in /8/ it is about 1000-2000 at.), that
leads to disruption of metal in some cases.
With further increasing of the hydrogen
concentration in metal the amount of new phase
(number of clusters) increases and the hydrogen
shielding effect could be possible. When the plasma
density keeps the increase, one more phase transition,
which connected with proton degeneracy [7], is possible
(curve 3, fig.2). For protium and tritium plasma this
is Fermi-Dirac degeneracy. For deuterium plasma this
phase transition means Bose-condensation.
CONCLUSION
The use of the diffusion membranes coated by
erosion high resistible material could be as a perspective
variant for plasma facing components providing both
erosion and hydrogen recycling processes control.
In the frame of strongly non-ideal plasma theory it
is possible to explain the high density phase (hydrogen-
clusters) formation in metals, as the result of the phase
transitions of hydrogen plasma in metal. The small
clusters can be condensed in metal lattice. The large
clusters formation is more probably in submicro- and
micro-pores.
REFERENCES
[1] G.P. Glazunov. Int. J. Hydrogen Energy, (1997), v.
22, No 2/3, 263-268.
[2] G.P. Glazunov. Sov. J. Surface: Physics, Chemistry,
Mechanics. (1983), No 8, 33-38.
[3] G.P. Glazunov et al. Sov. J. Tech. Phys. (1981), v.
51, No 10, p. 2139-2141.
[4] E. Salonen et al. Physical Review B, (1999), v.60,
No 20, 14005-14008.
[5] E. Fromm, E. Gebhardt. Gases and carbon in
metals. Moscow, (1980).
[6] G.P. Glazunov. Problems of Atomic Science and
Technology. Series: Vacuum, pure materials,
superconductors. (1995), v. 1(1), p.72-80. (in Russian)
[7] G.P. Glazunov. Sov. J. Tech. Phys. Letters. (1983),
v.9, No 24, 1498-1501.
[8] Hydrogen in Metals. V.1. Basic Properties. V.2.
Application-oriented properties. Edited by G.Alefeld
and J. Volkl. Springer-Verlag, Berlin Heidelberg New
York, 1978.
[9] W. Ebeling, W.D. Kraeft, D. Kremp. Theory of
Bound States and Ionization Equilibrium in Plasma and
Solids. Akademie-Berlin, 1976
[10] S. Ichimary. Rev.Mod.Phys., v.54, 1982, p.1017-
1059.
[11] I.M. Lifshits, V.V. Sljozov. Journal of
Experimental and Theoretical Physics, v.35, 1958,
p.479-492, in Russian.
[12] I.M.Lifshits, V.V.Sljozov. J. Phys. Chem. Solids,
v.19,1961,p.35.
[13] C.Wagner. Z.Electrochemie. Bd 65,S, 1961, p.243
Submicro-pore
R>Rc
Host interstitial
atom
H
(+)
1
2
Vacancy
|
| id | nasplib_isofts_kiev_ua-123456789-82378 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:16:15Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Glazunov, G.P. Volkov, E.D. Hassanein, A. 2015-05-29T07:37:29Z 2015-05-29T07:37:29Z 2000 Hydrogen behavior in bimetallic systems:permeation through thin metal films / G.P. Glazunov, E.D. Volkov, A. Hassanein // Вопросы атомной науки и техники. — 2000. — № 3. — С. 102-104. — Бібліогр.: 13 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/82378 533.9 The hydrogen permeation performances are presented for micron Mo, Ti, Nb, Zr, Cr, Ni, Cu, CuPd, TiN, and stainless steel films deposited on palladium from arc sputtered cathodes. Some physical mechanisms explaining anomalies behavior in above mentioned systems are suggested. In particular, it is shown that extreme high hydrogen permeability in the Mo-Pd system is caused by enhancing of diffusion coefficient in the system with a large number of connected pores. Also the possible use of such systems for an active control of recycling and erosion processes are considered. In the frame of non-ideal plasma theory the mechanism is suggested of hydrogen high content (clusters) formation as the result of hydrogen plasma phase transitions in metal. The small hydrogen clusters can be condensed in metal lattice. The arising of the large ones is more probably around defects and in submicro- and micro-pores appearing under, for example, plasma or energetic particle irradiation. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Рlasma Dynamics and Plasma-Wall Interaction Hydrogen behavior in bimetallic systems:permeation through thin metal films Article published earlier |
| spellingShingle | Hydrogen behavior in bimetallic systems:permeation through thin metal films Glazunov, G.P. Volkov, E.D. Hassanein, A. Рlasma Dynamics and Plasma-Wall Interaction |
| title | Hydrogen behavior in bimetallic systems:permeation through thin metal films |
| title_full | Hydrogen behavior in bimetallic systems:permeation through thin metal films |
| title_fullStr | Hydrogen behavior in bimetallic systems:permeation through thin metal films |
| title_full_unstemmed | Hydrogen behavior in bimetallic systems:permeation through thin metal films |
| title_short | Hydrogen behavior in bimetallic systems:permeation through thin metal films |
| title_sort | hydrogen behavior in bimetallic systems:permeation through thin metal films |
| topic | Рlasma Dynamics and Plasma-Wall Interaction |
| topic_facet | Рlasma Dynamics and Plasma-Wall Interaction |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82378 |
| work_keys_str_mv | AT glazunovgp hydrogenbehaviorinbimetallicsystemspermeationthroughthinmetalfilms AT volkoved hydrogenbehaviorinbimetallicsystemspermeationthroughthinmetalfilms AT hassaneina hydrogenbehaviorinbimetallicsystemspermeationthroughthinmetalfilms |