Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma
Processes of sputtering, surface modification and deuterium retention of tungsten coatings were studied under the influence of low-energy (500 eV) deuterium plasma with fluence (2·10²⁴D+/m²) at room temperature. The method of cathodic arc evaporation was used to deposit W and WN-coatings on stainles...
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| Zitieren: | Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma / G.D. Tolstolutskaya, A.S. Kuprin, A.V. Nikitin, I.E. Kopanets, V.N. Voyevodin, I.V. Kolodiy, R.L. Vasilenko, A.V. Ilchenko // Problems of atomic science and tecnology. — 2020. — № 2. — С. 54-59. — Бібліогр.: 23 назв. — англ. |
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Tolstolutskaya, G.D. Kuprin, A.S. Nikitin, A.V. Kopanets, I.E. Voyevodin, V.N. Kolodiy, I.V. Vasilenko, R.L. Ilchenko, A.V. 2023-11-23T11:06:29Z 2023-11-23T11:06:29Z 2020 Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma / G.D. Tolstolutskaya, A.S. Kuprin, A.V. Nikitin, I.E. Kopanets, V.N. Voyevodin, I.V. Kolodiy, R.L. Vasilenko, A.V. Ilchenko // Problems of atomic science and tecnology. — 2020. — № 2. — С. 54-59. — Бібліогр.: 23 назв. — англ. 1562-6016 PACS: 52.40Hf, 28.52Fa, 68.49Sf, 79.20Rf https://nasplib.isofts.kiev.ua/handle/123456789/194363 Processes of sputtering, surface modification and deuterium retention of tungsten coatings were studied under the influence of low-energy (500 eV) deuterium plasma with fluence (2·10²⁴D+/m²) at room temperature. The method of cathodic arc evaporation was used to deposit W and WN-coatings on stainless steel. Results of erosion studies indicated that the sputtering yields for coatings WN and W are 3.1·10⁻³ and 4.8·10⁻³ at./ion, respectively, and at least two times larger compared to bulk W but almost an order of magnitude smaller compared to ferritic martensitic steels. The total D retentions of W coatings were on the order of 5·10¹⁹D/m² and around one orders of magnitude lower than that of WN. Вивчено процеси розпилення, модифікації поверхні і захоплення дейтерію в вольфрамових покриттях під впливом низькоенергетичної (500 еВ) дейтерієвої плазми з флюенсом (4·10²⁴D+/м²). Метод катоднодугового випаровування використано для осадження W- і WN-покриттів на нержавіючу сталь. Результати ерозійних досліджень показали, що коефіцієнти розпилення покриттів WN і W складають 3.1·10⁻³ і 4.8·10⁻³ ат./іон відповідно і, як мінімум, в два рази більше в порівнянні з масивним W, але майже на порядок величини менше в порівнянні з феритно-мартенситними сталями. Загальна кількість дейтерію, утримуваного в W-покритті, становила близько 5·10¹⁹D/м², що приблизно на один порядок нижче, ніж у WN. Изучены процессы распыления, модификации поверхности и захвата дейтерия в вольфрамовых покрытиях под воздействием низкоэнергетической (500 эВ) дейтериевой плазмы с флюенсом (4·10²⁴D+/м²). Метод катодно-дугового испарения использован для осаждения W- и WN-покрытий на нержавеющую сталь. Результаты эрозионных исследований показали, что коэффициенты распыления покрытий WN и W составляют 3,1·10⁻³ и 4,8·10⁻³ ат./ион соответственно и, как минимум, в два раза больше по сравнению с массивным W, но почти на порядок величины меньше по сравнению с ферритно-мартенситными сталями. Общее количество дейтерия, удерживаемого в W-покрытии, составляло около 5·10¹⁹D/м², что примерно на один порядок ниже, чем у WN. The work was financially supported by the National Academy of Science of Ukraine (program “Support of the development of main lines of scientific investigations” (KPKVK 6541230)). en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Physics of radiation damages and effects in solids Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma Захоплення дейтерію і розпилення вольфрамових покриттів при дії низькоенергетичної дейтерієвої плазми Захват дейтерия и распыление вольфрамовых покрытий при воздействии низкоэнергетической дейтериевой плазмы Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| spellingShingle |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma Tolstolutskaya, G.D. Kuprin, A.S. Nikitin, A.V. Kopanets, I.E. Voyevodin, V.N. Kolodiy, I.V. Vasilenko, R.L. Ilchenko, A.V. Physics of radiation damages and effects in solids |
| title_short |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| title_full |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| title_fullStr |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| title_full_unstemmed |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| title_sort |
deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma |
| author |
Tolstolutskaya, G.D. Kuprin, A.S. Nikitin, A.V. Kopanets, I.E. Voyevodin, V.N. Kolodiy, I.V. Vasilenko, R.L. Ilchenko, A.V. |
| author_facet |
Tolstolutskaya, G.D. Kuprin, A.S. Nikitin, A.V. Kopanets, I.E. Voyevodin, V.N. Kolodiy, I.V. Vasilenko, R.L. Ilchenko, A.V. |
| topic |
Physics of radiation damages and effects in solids |
| topic_facet |
Physics of radiation damages and effects in solids |
| publishDate |
2020 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Захоплення дейтерію і розпилення вольфрамових покриттів при дії низькоенергетичної дейтерієвої плазми Захват дейтерия и распыление вольфрамовых покрытий при воздействии низкоэнергетической дейтериевой плазмы |
| description |
Processes of sputtering, surface modification and deuterium retention of tungsten coatings were studied under the influence of low-energy (500 eV) deuterium plasma with fluence (2·10²⁴D+/m²) at room temperature. The method of cathodic arc evaporation was used to deposit W and WN-coatings on stainless steel. Results of erosion studies indicated that the sputtering yields for coatings WN and W are 3.1·10⁻³ and 4.8·10⁻³ at./ion, respectively, and at least two times larger compared to bulk W but almost an order of magnitude smaller compared to ferritic martensitic steels. The total D retentions of W coatings were on the order of 5·10¹⁹D/m² and around one orders of magnitude lower than that of WN.
Вивчено процеси розпилення, модифікації поверхні і захоплення дейтерію в вольфрамових покриттях під впливом низькоенергетичної (500 еВ) дейтерієвої плазми з флюенсом (4·10²⁴D+/м²). Метод катоднодугового випаровування використано для осадження W- і WN-покриттів на нержавіючу сталь. Результати ерозійних досліджень показали, що коефіцієнти розпилення покриттів WN і W складають 3.1·10⁻³ і 4.8·10⁻³ ат./іон відповідно і, як мінімум, в два рази більше в порівнянні з масивним W, але майже на порядок величини менше в порівнянні з феритно-мартенситними сталями. Загальна кількість дейтерію, утримуваного в W-покритті, становила близько 5·10¹⁹D/м², що приблизно на один порядок нижче, ніж у WN.
Изучены процессы распыления, модификации поверхности и захвата дейтерия в вольфрамовых покрытиях под воздействием низкоэнергетической (500 эВ) дейтериевой плазмы с флюенсом (4·10²⁴D+/м²). Метод катодно-дугового испарения использован для осаждения W- и WN-покрытий на нержавеющую сталь. Результаты эрозионных исследований показали, что коэффициенты распыления покрытий WN и W составляют 3,1·10⁻³ и 4,8·10⁻³ ат./ион соответственно и, как минимум, в два раза больше по сравнению с массивным W, но почти на порядок величины меньше по сравнению с ферритно-мартенситными сталями. Общее количество дейтерия, удерживаемого в W-покрытии, составляло около 5·10¹⁹D/м², что примерно на один порядок ниже, чем у WN.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/194363 |
| citation_txt |
Deuterium trapping and sputtering of tungsten coatings exposed to low-energy deuterium plasma / G.D. Tolstolutskaya, A.S. Kuprin, A.V. Nikitin, I.E. Kopanets, V.N. Voyevodin, I.V. Kolodiy, R.L. Vasilenko, A.V. Ilchenko // Problems of atomic science and tecnology. — 2020. — № 2. — С. 54-59. — Бібліогр.: 23 назв. — англ. |
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2025-11-26T01:45:43Z |
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2025-11-26T01:45:43Z |
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1850606257334910976 |
| fulltext |
ISSN 1562-6016. PASТ. 2020. №2(126), p. 54-59.
DEUTERIUM TRAPPING AND SPUTTERING OF TUNGSTEN
COATINGS EXPOSED TO LOW-ENERGY DEUTERIUM PLASMA
G.D. Tolstolutskaya
1
, A.S. Kuprin
1
, A.V. Nikitin
1
, I.E. Kopanets
1
, V.N. Voyevodin
1,2
,
I.V. Kolodiy
1
, R.L. Vasilenko
1
, A.V. Ilchenko
1
1
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine;
2
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
Processes of sputtering, surface modification and deuterium retention of tungsten coatings were studied under
the influence of low-energy (500 eV) deuterium plasma with fluence (210
24
D
+
/m
2
) at room temperature. The
method of cathodic arc evaporation was used to deposit W and WN-coatings on stainless steel. Results of erosion
studies indicated that the sputtering yields for coatings WN and W are 3.110
-3
and 4.810
-3
at./ion, respectively, and
at least two times larger compared to bulk W but almost an order of magnitude smaller compared to ferritic
martensitic steels. The total D retentions of W coatings were on the order of 510
19
D/m
2
and around one orders of
magnitude lower than that of WN.
PACS: 52.40Hf, 28.52Fa, 68.49Sf, 79.20Rf
INTRODUCTION
Tungsten (W) is a promising plasma-facing material
(PFMs) for ITER and future fusion reactors due to its
favorable thermo-mechanical properties, low hydrogen
permeability, low sputtering erosion yield, high thermal
conductivity and no chemical reaction with hydrogen
[1]. However, it is currently believed that the
manufacture of the first wall of a fusion reactor entirely
from tungsten is not economically viable because of
high cost implications to the project, difficulties in
machining due to its hardness and brittleness of W and
bulkiness resulting in large structural weight. Tungsten
coatings on a stainless-steel substrate can be considered
as a good solution in terms of economic and the
protection of structural material from interaction with
the plasma [2].
To assess the possibility to use the W coatings as
PFMs, there is a need to examine a behavior of these
materials under plasma exposure. Sputtering of PFMs
due to interaction with energetic ions (particularly
hydrogen isotopes) is an essential issue in magnetically
confined fusion devices because it is directly related to
impurity generation as well as to the lifetime of plasma-
facing components 3.
For divertor radiative cooling by impurity seeding,
different noble gases like Ne and Ar have been tested,
but the best results so far have been obtained with N2
seeding [4, 5]. An overall improvement of the plasma
confinement was detected thanks to a strongly reduced
power load to divertor surfaces and the total suppression
of W influx into the plasma [6]. One of the reasons of
these effects has been development of tungsten nitrides
films at the surface of the W tiles reducing the W
sputtering. This decrease is related to the accumulation
of nitrogen at the tungsten surface, thus reducing the
possibility of a tungsten atom being sputtered out,
combined with the similar, large bonding energy of
W-W and W-N (~ 8.6 eV). However, before using
tungsten nitride coatings in tokamaks, it must be studied
how the processes of hydrogen isotopes retention and
the formation of blisters proceed in them, due to the
possible long-term trapping of tritium, which could lead
to an important safety issue; finding out if the tungsten
nitrides will survive the divertor tokamak conditions
(temperature and particle loads). In addition, it is need
to determine the sputtering at particle loads similar to
the expected in ITER.
The goal of this work is to experimentally determine
the sputtering yields, surface morphology changes and
deuterium retention of W and WN coatings that are
deposited by the cathodic arc evaporation and exposed to
low-energy deuterium plasma.
1. MATERIAL AND METHODS
A set of tungsten coatings was formed using
unfiltered cathodic arc evaporation in a “Bulat-6”
system equipped with a W (99.9%) cathode of 60 mm
diameter [7]. The substrate-cathode distance was about
250 mm. A vacuum-arc plasma source with magnetic
stabilization of a cathode spot was used. The arc current
was 140 A. The chamber was evacuated to a pressure of
2∙10
−3
Pa. Coatings were deposited on the substrates
(10×20×1.5 mm) of stainless steel 18Cr10NiTi at a
negative bias potential of –50 V without rotation. The
W coatings were deposited in vacuum ~ (3…4)∙10
−3
Pa
and WN coatings under nitrogen pressure ~ 2 Pa. The
substrate temperature during deposition did not exceed
500 °C. The coating deposition rate was ~ 6 µm/h.
The W and WN coatings have been irradiated with
deuterium ions using glow gas-discharge plasma at
1000 V. The design and principle of operation of the
gaseous plasma source used for irradiation of the samples
is described in detail in [8]. The specimen temperature
was measured by the thermocouple and was (30±2.5) °C
during irradiation. The maximum irradiation fluence was
410
24
m
–2
. The experimental ion flux and fluence were
calculated from the measured ion currents and beam
spot areas.
The erosion yield was primarily evaluated by a
weight-loss technique. Before and after plasma exposure,
the weight of each target was measured by a
microbalance system, and the erosion rate was then
calculated from the weight loss and the total deuterium
fluence.
The implanted deuterium depth distribution was
measured by means of the D (
3
He, p)
4
He nuclear reaction
(NRA). The measurements were performed at room
temperature using back scattering geometry. Deuterium
depth profiles were extracted from the obtained data
using “Helen” software [9].
XRD analysis was performed by DRON-4-07
diffractometer using Cu-Kα filtered radiation. Residual
macrostress analysis of the samples was carried out by
the sin2ψ-method. Lattice parameters in the unstrained
state a0 were calculated from sin
2
ψ-plots.
Investigations of surface microstructure before and
after irradiation were performed using scanning electron
microscope JEOL JSM-7001F. Chemical composition
of the coatings was determined by energy dispersive
X-ray spectroscopy – EDS.
2. RESULTS AND DISCUSSION
Fig. 1 shows a view of cross-section of the W and
WN coatings deposited by CAE. The surface and
interface between the coating and substrate are indicated
by the white horizontal line. The coating thickness is
about 5 µm. Within the coating we can see the grains
with dimensions in the µm range and the absence of a
pronounced columnar structure.
a
b
Fig. 1. Cross-section SEM images of W (a)
and WN (b) coatings
The structure of W and WN-coating is dense and
without pores (see Fig. 1). The absence of columnar
structure into those coatings may be explained by
sufficiently high energy of deposited tungsten ions and
by the high degree of plasma ionization relatively to the
flow of evaporated material which is characteristic of
cathodic arc evaporation method [10]. WN-coating has
a less refined microstructure with columnar structure
elements (see Fig. 1,b) and near stoichiomertic
concentration of N ~ 50 at.% according to EDS analysis.
X-ray diffraction patterns of the W and WN coatings
are shown in Fig. 2. Diffraction pattern of W
corresponds to the single-phase α-modification of
tungsten (see Fig. 2,a) with lattice parameter
а = (3.1730±3)·10
-4
Å. Lattice parameter in unstrained
state а0 = (3.1668±3)·10
-4
Å is large than literature data
(а = 3.1648 Å) due to presence of impurities and/or
interstitial atoms. Only one phase was revealed in the
WN coating − hexagonal tungsten nitride WN-δ
(hexagonal system, space group No. 187, structural type
WC) (see Fig. 2,b).
The sharp peaks indicate a high crystallinity of the
W and WN coatings. Compared with the standard card,
the coatings have obvious preferred orientation (110)
shown in Fig. 2. In addition, an analysis of the
substructural characteristics (the crystallite size and the
level of microstrains ) was carried out according to the
integral width of the diffraction lines (Williamson-Hall
method). The parameters determined by diffractometric
studies of samples from W and WN, namely, the lattice
period, macrostresses, crystallite size and microstrains
are given in Table 1.
a
b
Fig. 2. X-ray diffraction patterns of W (a)
and WN (b) coatings
Table 1
Structural and substructural parameters of W and WN
Sample
Lattice
period,
Å
Macro-
stresses σφ,
GPa
Crystallite
size,
nm
Micro-
strains
ε, × 10-3
W a = 3.1730 -1.63 46.9 2.55
WN
a = 2.922
c = 2.964
– 29.8 7.81
The macrostress analysis of the samples were carried
out by the sin
2
ψ-method (tilt angles ψ = -45; -30; 0; 30;
1um
45º, as well as φ = -60; 0, and +60º). The lattice
parameters of both types of coatings are much larger
than the literature values, which is most likely due to the
presence of compressive stress in the coating.
Fig. 3 shows an SEM image the surface
microstructure of the W and WN coatings in the initial
state and after exposed to plasma. As can be seen from
Fig. 3 irradiation of tungsten coatings did not lead to the
formation of blisters. Only the process of sputtering is
observed.
a b
c d
e f
Fig. 3. SEM images of morphology of W (a, c, e) and WN (b, d, f) coatings in initial state (a, b) and after irradiation
at 300 K with 1 keV D2
+
to 1·10
24
D2
+
/m
2
(c, d) and to 2·10
24
ion/m
2
(e, f)
Initial W coatings exhibit surfaces of densely packed
“nanoridges” or overlapping tiles (see Fig. 3,a).
Previously reported in [11] that these “nanoridges” were
observed on the -W phase film surfaces irrespective
of the film thickness. It is shown that many individual
grains contain two types of “nanoridge” domains
oriented with each other with an angle ranging between
109 and 124º. Each domain has ridges with an average
height and period of (1.5±0.5) and (7.5±1.0) nm,
respectively [12].
It was suggested that an anisotropic surface diffusion
mechanism on crystalline W film is responsible for the
formation of such nanostructures. Every atom on the
surface lattice structures of the -W(1 1 0) plane in the
topmost layer has four nearest-neighbors and two next-
nearest-neighbors located at the distances of 3a/2 and a
in the topmost layer, respectively, where a is the lattice
constant of bcc -W(1 1 0) structure. The anisotropy in
diffusion barriers along different directions is large and
therefore W adatom motion on the W (1 1 0) plane
should differ in different directions. In [13] a detailed
study of the self-diffusion of W on W lattice by using
field ion microscopy have done. It was shown that the
surface diffusion not only depends on the plane index
but also on the crystallographic directions on a
particular plane and can be anisotropic. So, the
formation of “nanoridges” oriented in the high mobility
111 directions are a result of the anisotropic surface
diffusion of W particles over the -W (1 1 0) surface.
The -WN is not an amorphous phase but perhaps,
there is no preferred direction for diffusion of the
impinging W adatoms on the -WN coating surface.
Thus, no ridge patterns were visible on the -WN
coating surface (see Fig. 3,b). Instead, the surface
topography shows the smooth and fine cellular
structure.
The evolution of the surface of W coating due to the
sputtering process after exposure to a deuterium plasma
is shown in Fig. 3,c,e. The “nanoridges” preferentially
sputtered at a dose 1·10
24
D2
+
/m
2
(see Fig. 3,c) and
completely sputtered at a dose 2·10
24
D2
+
/m
2
(see
Fig. 3,e). As can be seen on the SEM picture in Fig. 3,e
areas towering above surface of microparticles were
sputtered also.
The evolution of the surface of -WN coating due to
exposure to a deuterium plasma as shown in Fig. 3,d,f
caused by the sputtering process of cellular structure at
an intermediate dose of irradiation up to obtaining
needle like morphology at a dose 2·10
24
D2
+
/m
2
.
Table 2 shows the results for the sputtering yields
(Y) of W and WN coatings in comparison with
published data of sputtering yields of bulk tungsten 14
and reduced-activation ferritic martensitic (RAFM)
steels as promising candidates for PFMs in future fusion
power plants 15. The sputtering yield was determined
from the weight loss and the total deuterium fluence for
accordingly 500 eV/D as dominant impinging energy.
Data for comparison were taken at the same energy of
deuterium ions.
Table 2
Sputtering yields of coatings and RAFM steels
for deuterium (500 eV)
Material W WN Wbulk 14 F-M SS 15
Y, at./ion 4.810
-3
3.110
-3
2.210
-3
310
-2
As seen in Table 2, values of the experimentally
measured sputtering yield of the tungsten coatings
exposed to the D plasma are two times larger compared
to bulk W but almost an order of magnitude smaller
compared to ferritic martensitic (RAFM) steels. It
should be noted that the WN coatings have the
sputtering coefficient which is almost one and a half
times smaller in comparison with W coatings. In Ref.
[16] it has been detected that W2N films presents a
nitrogen preferential sputtering by deuterium, probably
enhanced by chemical reactions towards ammonia
production.
As an important issue for ITER and DEMO, fuel
retention and diffusion in first-wall materials presents a
safety (tritium amount in ITER < 700 g [17]) and cost
concern. In general, hydrogen retention in W is low
[18, 19] but diffusion at elevated temperatures
(> 400 K) is relatively fast [18].
In the present work the retention and depth
distribution of D in coatings after plasma exposure were
measured by NRA method. Fig. 4 presents the depth
distribution profile of deuterium implanted to a dose of
1·10
24
D2
+
/m
2
at Troom in W coating, and its evolution
during aging at Troom for 30 days.
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
0,0
0,2
0,4
0,6
0,8
1,0
D
c
o
n
c
e
n
tr
a
ti
o
n
,
a
t.
%
Depth, mm
1
2
Fig. 4. Depth profiles of D in W coatings with a
thickness of 5 µm on the steel substrate measured after
the D plasma exposure (1) and after 30 days (2)
The calculated normal-incident range of 0.5 keV D
+
in tungsten is about 7 nm. Immediately after exposure
the deuterium depth profile localized at about 0.1 μm,
which is determined by the resolution of the NRA
method in the backscattering geometry and a large
gradient of deuterium concentration. After exposure at
Troom for 30 days deuterium was penetrated into a depth
up to 1.6 µm. A small amount of deuterium is captured
at 0.6…0.8 µm on defects created by an analyzing beam
of He
3
ions.
NRA depth profiling of D-implanted WN films has
indicated that D is retained only in a thin surface layer
(< 0.2 μm) and even after exposure at Troom for 30 days
its depth distribution remains virtually unchanged
(Fig. 5). However, its amount is decreased almost 1.5
times, probably due to desorption from the sample 20.
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
0
2
4
6
8
Depth, mm
D
c
o
n
c
e
n
tr
a
ti
o
n
,
a
t.
%
1
2
Fig. 5. Depth profiles of D in WN coatings with a
thickness of 5 µm on the steel substrate measured after
the D plasma exposure (1) and after 30 days (2)
mm
mm
In Ref. [21] it was proposed that hydrogen trapping
first occurs predominantly within the implantation zone
at impurities, dislocations, vacancies, grain boundaries
and other crystal defects. If all the traps in the implanted
zone become filled, and the flux of hydrogen is larger
than the rate of hydrogen diffusion out of the
implantation zone, there will exist a local
supersaturation of mobile hydrogen. Additional
hydrogen introduced by prolonged irradiation will then
diffuse deeper into the sample, filling traps beyond the
ion range, expanding the distribution of deuterium.
The first analysis presented by many groups in the
PFMC 2013 conference [4] points to an increased D
retention at the surface due to a lower D2 recombination
rate and/or tungsten nitrides acting as a diffusion barrier
for deuterium. The first possibility will cause a larger D
retention in the crystalline defects in bulk tungsten, but
the second one would greatly decrease that retention if
the nitrogen layer is below the ion implantation range.
A set of bulk W samples was implanted with D up to
a fluence of 1∙10
24
Dm
−2
with or without N pre-
implantation at 300 and 500 K. The surface
modification by blistering as well as the D depth
distribution measured by NRA show that N pre-
implantation plays a very different role for D retention
in the following D plasma exposure at the different
applied temperatures: At 500 K, the W–N layer strongly
enhances D retention; while at 300 K it has no obvious
effect [22].
Recent experiments [23] have indicated that a thin
N-containing layer present during plasma loading at
500 K could reduce the loss of D through the surface
thus increasing D retention. Furthermore, NRA depth
profiling of D-implanted WNx films has indicated that
D is retained only in a thin surface layer. It was
hypothesized that D is retained only in the ion
penetration range of the impinging D ions and does not,
as in bulk W, diffuse to greater depth.
D retention in WNx layers deposited on bulk W was
studied as a model system for some aspects of plasma-
surface interaction in N-seeded discharges in fusion
devices with a W first wall. Results show that D is
retained in the topmost surface only and does not
diffuse into deeper layers of the WNx film at the
temperature of 300 K. This is in contrast to the behavior
of pure W films and bulk W samples which clearly
show diffusion to larger depth at this temperature [18].
The presented literature data and experimental
results obtained in this work indicate that WNx films
might be applicable as D diffusion barriers in future
fusion applications.
CONCLUSIONS
Processes of sputtering, surface modification and
deuterium retention of W and WN coatings deposited on
stainless steel by cathodic arc evaporation were studied
under the influence of low-energy (500 eV) deuterium
plasma with fluence (410
24
D
+
/m
2
) at room
temperature.
Coatings deposited in vacuum have a single
crystalline α-W phase with crystallite size ~ 46.9 nm
and microstrain ~ 2.55∙10
-3
. Deposition under a nitrogen
pressure of 2 Pa leads to the formation of δ-WN nitride
coatings with crystallite size ~ 29.8 nm and microstrain
~ 7.81∙10
-3
. All deposited coatings having dense
microstructure without pores.
Values of the experimentally measured sputtering
yield of the tungsten coatings exposed to the D plasma
are two times higher compared to bulk W but almost an
order of magnitude smaller compared to PFM – ferritic
martensitic steels. The WN coatings have the sputtering
coefficient which is almost one and a half times smaller
in comparison with W coatings.
The total D retentions of W coatings were on the
order of 510
19
D/m
2
and around one orders of
magnitude lower than that of WN, which can be
attributed to fast deuterium diffusion in the W coating
within the depth of 1.6 μm.
ACKNOWLEDGEMENTS
The work was financially supported by the National
Academy of Science of Ukraine (program “Support of
the development of main lines of scientific
investigations” (KPKVK 6541230)).
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Article received 21.02.2020
ЗАХВАТ ДЕЙТЕРИЯ И РАСПЫЛЕНИЕ ВОЛЬФРАМОВЫХ ПОКРЫТИЙ
ПРИ ВОЗДЕЙСТВИИ НИЗКОЭНЕРГЕТИЧЕСКОЙ ДЕЙТЕРИЕВОЙ ПЛАЗМЫ
Г.Д. Толстолуцкая, А.С. Куприн, А.В. Никитин, И.Е. Копанец, В.Н. Воеводин, И.В. Колодий,
Р.Л. Василенко, А.В. Ильченко
Изучены процессы распыления, модификации поверхности и захвата дейтерия в вольфрамовых
покрытиях под воздействием низкоэнергетической (500 эВ) дейтериевой плазмы с флюенсом (410
24
D
+
/м
2
).
Метод катодно-дугового испарения использован для осаждения W- и WN-покрытий на нержавеющую сталь.
Результаты эрозионных исследований показали, что коэффициенты распыления покрытий WN и W
составляют 3,110
-3
и 4,810
-3
ат./ион соответственно и, как минимум, в два раза больше по сравнению с
массивным W, но почти на порядок величины меньше по сравнению с ферритно-мартенситными сталями.
Общее количество дейтерия, удерживаемого в W-покрытии, составляло около 510
19
D/м
2
, что примерно на
один порядок ниже, чем у WN.
ЗАХОПЛЕННЯ ДЕЙТЕРІЮ І РОЗПИЛЕННЯ ВОЛЬФРАМОВИХ ПОКРИТТІВ
ПРИ ДІЇ НИЗЬКОЕНЕРГЕТИЧНОЇ ДЕЙТЕРІЄВОЇ ПЛАЗМИ
Г.Д. Толстолуцька, О.С. Купрін, А.В. Нікітін, І.Є. Копанець, В.М. Воєводін, І.В. Колодій,
Р.Л. Василенко, О.В. Ільченко
Вивчено процеси розпилення, модифікації поверхні і захоплення дейтерію в вольфрамових покриттях під
впливом низькоенергетичної (500 еВ) дейтерієвої плазми з флюенсом (410
24
D
+
/м
2
). Метод катодно-
дугового випаровування використано для осадження W- і WN-покриттів на нержавіючу сталь. Результати
ерозійних досліджень показали, що коефіцієнти розпилення покриттів WN і W складають 3,110
-3
і
4,810
-3
ат./іон відповідно і, як мінімум, в два рази більше в порівнянні з масивним W, але майже на порядок
величини менше в порівнянні з феритно-мартенситними сталями. Загальна кількість дейтерію,
утримуваного в W-покритті, становила близько 510
19
D/м
2
, що приблизно на один порядок нижче, ніж у
WN.
|