Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation
An erosion behavior of TiN-coated stainless-steel (SS) surfaces was investigated during biased-limiter experiments within the Uragan-3M torsatron and during simulation experiments, which were performed with plasma-accelerator and glow-discharge (GD) plasmas. For a TiN-coated SS head-plate of a limit...
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| Zitieren: | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation / G.P. Glazunov, E.D. Volkov, V.P. Veremeyenko, N.A. Kosik, Al.A. Kutsyn, J. Langner, E. Langner, Yu.K. Mironov, N.I. Nazarov, J. Piekoszewski, M. Sadowski, J. Stanislawski, V.I. Tereshin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 155-159. — Бібліогр.: 18 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859683207000096768 |
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| author | Glazunov, G.P. Volkov, E.D. Veremeyenko, V.P. Kosik, N.A. Kutsyn, Al.A. Langner, J. Langner, E. Mironov, Yu.K. Nazarov, N.I. Piekoszewski, J. Sadowski, M. Stanislawski, J. Tereshin, V.I. |
| author_facet | Glazunov, G.P. Volkov, E.D. Veremeyenko, V.P. Kosik, N.A. Kutsyn, Al.A. Langner, J. Langner, E. Mironov, Yu.K. Nazarov, N.I. Piekoszewski, J. Sadowski, M. Stanislawski, J. Tereshin, V.I. |
| citation_txt | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation / G.P. Glazunov, E.D. Volkov, V.P. Veremeyenko, N.A. Kosik, Al.A. Kutsyn, J. Langner, E. Langner, Yu.K. Mironov, N.I. Nazarov, J. Piekoszewski, M. Sadowski, J. Stanislawski, V.I. Tereshin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 155-159. — Бібліогр.: 18 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | An erosion behavior of TiN-coated stainless-steel (SS) surfaces was investigated during biased-limiter experiments within the Uragan-3M torsatron and during simulation experiments, which were performed with plasma-accelerator and glow-discharge (GD) plasmas. For a TiN-coated SS head-plate of a limiter the arc ignition probability was found to be lower than 10-4 per plasma pulse. Possible physical mechanisms of this effect had been discussed. Within special vacuum stands, using thermal-desorption and mass-spectrometry methods, there were performed measurements of an outgassing rate and hydrogen permeability of TiNcoatings. The negligible outgassing from TiN-coated SS samples, during their heating up to 473 K, was observed after a cleaning procedure with a molecular hydrogen inflow under pressure of about 10-4 Torr, on contrary to the considerable increase of (q) rate for the irradiated samples. Measured values of the TiN-film hydrogen permeability were several times lower, and activation energy of the hydrogen permeation was considerably lower than that for the SS films (15 kJ/mole instead of 19.9 kJ/mole). The use of TiN-coated SS and diffusion membranes, for the reduction of the erosion, recycling, and hydrogen isotope inventory control, as well as for improvement of vacuum conditions, has been considered.
|
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| fulltext |
UDC 533.9
Problems of Atomic Science and Technology. 2000. № 6. Series: Plasma Physics (6). p. 155-159 155
EROSION, PERMEATION AND OUTGASSING PERFORMANCES OF
TiN COATING UNDER/AFTER HYDROGEN PLASMA IRRADIATION
G.P. Glazunov, E.D. Volkov, V.P. Veremeyenko, N.A. Kosik, Al.A. Kutsyn, J. Langner *,
E. Langner *, Yu.K. Mironov, N.I. Nazarov, J. Piekoszewski *, M. Sadowski *,
J. Stanislawski *, and V.I. Tereshin
Institute of Plasma Physics of NSC KhIPT, 61108 Kharkov, Ukraine
* The Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk by Warsaw, Poland
An erosion behavior of TiN-coated stainless-steel (SS) surfaces was investigated during biased-limiter experiments within the
Uragan-3M torsatron and during simulation experiments, which were performed with plasma-accelerator and glow-discharge
(GD) plasmas. For a TiN-coated SS head-plate of a limiter the arc ignition probability was found to be lower than 10-4 per plasma
pulse. Possible physical mechanisms of this effect had been discussed. Within special vacuum stands, using thermal-desorption
and mass-spectrometry methods, there were performed measurements of an outgassing rate and hydrogen permeability of TiN-
coatings. The negligible outgassing from TiN-coated SS samples, during their heating up to 473 K, was observed after a cleaning
procedure with a molecular hydrogen inflow under pressure of about 10-4 Torr, on contrary to the considerable increase of (q)
rate for the irradiated samples. Measured values of the TiN-film hydrogen permeability were several times lower, and activation
energy of the hydrogen permeation was considerably lower than that for the SS films (15 kJ/mole instead of 19.9 kJ/mole). The
use of TiN-coated SS and diffusion membranes, for the reduction of the erosion, recycling, and hydrogen isotope inventory
control, as well as for improvement of vacuum conditions, has been considered.
1. Introduction
The modification of SS components by titanium-
nitride (TiN) coatings has been widely used in
technology of the manufacturing of RF antennas,
shields, movable and unmovable limiters for the
Uragan-3M (U-3M) and Uragan-2M (U-2M) torsatron-
type facilities. When a TiN-coated RF antenna frame
was applied, a considerable reduction in the unipolar arc
erosion of antenna surfaces, and a decrease in amount of
heavy impurities in plasma, had been observed [1].
Also, the TiN coating sputtering coefficient, under the
ion irradiation, had been found to be lower by factor of
3 as compared with that for stainless steel. For hydrogen
discharges within U-3M, however, some uncontrollable
disruptions of the TiN-coating (upon the SS shields)
were observed after two experimental campaigns.
Considerable changes in coating colors, from golden for
non-irradiated parts of shield - to silvery, orange, red,
and dark-blue color for heavily irradiated parts, were
observed. The data obtained in previous studies [2],
with help of the Auger electron spectroscopy (AES), X-
ray spectroscopy (XRD), fluorescence (EDX) diagnostic
methods, allow to suggest that these color changes
could be caused by various alterations in the
stoichiometric composition of a TiN-film surface layer
after the interaction with U-3M hydrogen plasma. It
must be noted, that such damages were not observed
after the hydrogen-ion irradiation of the same TiN
coatings, as described in Ref. [3], but a considerable Ti
enrichment of the film surface layer was found. On the
contrary, the film color changes took place after the
high-power pulsed hydrogen-plasma irradiation at
certain energy densities and fluencies [2]. The TiN
erosion values, as measured in this work, were
considerably higher than those observed for bare SS.
The nature of the disruptions mentioned above and
mechanisms of such an erosion behavior of the TiN-
coating were not explained enough. Taking into
account, that large-surface TiN-coated SS shields and
RF-antennas, which were installed in U-2M, have to be
operated in future, additional investigations of a TiN-
coating behavior under the pulsed plasma irradiation are
needed. Besides that, in order to get a data base for
control of vacuum conditions, erosion, hydrogen
recycling, and inventory processes, there was necessity
to study the outgassing and hydrogen behavior
characteristics of the TiN coatings. Such information
could also be useful for TiN surface modification
technologies used today, and in particular for ultra-high
vacuum applications [4], for an improvement of the RF-
window breakdown resistance [5], etc.
2. Experiments and results
2.1. Erosion behavior in biased-limiter experiments
For the experiments with a biased limiter a new
version of the movable limiter was installed within the
U-3M vacuum chamber. Instead of a hot-pressed boron-
carbide tile [6], the limiter head plate material was
12KH18N10T SS coated with 5-µm-thick TiN-film,
which was deposited by means of the plasma-flux
condensation method [7]. The scheme of experiment
was similar to that described in Ref. [6]. The limiter
plate edge was located at a distance of 14 cm from the
plasma column axis (at the plasma edge position). In
order to investigate a TiN erosion behavior there were
channels for measurements of TiII and NII spectral lines
and eleven collecting probes placed on plasma facing
surfaces of the helical winding housings. Tests of the
limiter material were performed in the ICRF plasma
discharge cleaning-regime. Typical operational
parameters were as follows: hydrogen pressure p = 10-4
Torr, ne = 2x1012 cm-3, Te = 10-15 eV, B = 0.035 T,
plasma pulse duration t = 50 ms, pulse frequency f = 0.2
Hz, total discharge power W = 80 kW at frequency of
the RF generator equal to 5.4 MHz. The limiter head
plate was biased negatively to -(120-200) V, and the
bias pulse duration was 10-50 ms. After 104 plasma
cleaning discharges (no arc ignition was observed
during that period) the limiter was removed from its
position near plasma edge region and it was placed
within a divertor slot. No increase in NII or TiII line
intensity was observed for biased/unbiased regimes of
the experiments, both for edge plasma and divertor
plasma positions. After the exposure of the limiter to
156
divertor plasma during 103 work discharges, when the
experimental campaign was finished, the TiN-coated
head plate was dismounted for an analysis.
There were observed no damages of the TiN surface,
except for weak change of the TiN-film color on that
part of head plate surface, which had the direct contact
with the edge plasma. Taking into account the number
of plasma pulses, probability of the arc ignition for TiN
was estimated to be less than 10-4 per pulse, instead of
10-1 measured for the previous boron-carbide limiter [8].
Also no increase in collecting probe weights was found,
in contrary to the previous experiments with the B4C
limiter [9]. These results indicate only a higher erosion
resistance of the TiN-coated SS surfaces to the plasma
irradiation, under biased-limiter experiment conditions.
In order to shed some light on the nature of the TiN-
coated SS shield disruption, some simulation
experiments were undertaken.
2.2. Erosion behavior in simulation experiments
The simulation studies of an erosion behavior of
TiN-coated SS samples were performed with pulsed
hydrogen plasmas produced by a plasma accelerator,
and with stationary glow-discharge (GD) plasmas. In
the first case the specimens of 10x25 mm size, which
were cut out from a non-irradiated part of the U-3M RF-
antenna shield, had identical performances to the above-
mentioned limiter head-plate material. It should be
noted that that shield was located between the RF-
antenna frame and a housing of the helical windings,
and it was exposed under typical U-3M operational
parameters during two experimental campaigns. It
should, also, be added that the shield, after its
dismounting and removing from the U-3M vacuum
chamber, was exposed to atmospheric air during about
12 months. A scheme of the irradiation, operational
regimes and diagnostics, were described in details in
previous papers [2, 10]. Here will be described only
data about the erosion dependence on an energy density
and a number of pulses, in order to discuss a physical
mechanism of the TiN-coating disruption. It can be seen
in Fig.1a that the erosion value depends weakly on an
energy flux density in spite of a different character of
the disruption process. It should be noted that all points
in Fig.1a present results of the irradiation with single
plasma pulse. According to estimations the energy flux
density decreased from 5.5 J/cm2 to 1.4 J/cm2 when a
distance was changed from 30 cm to 60 cm. With such
an energy density variation the net erosion value was
changed from 5x10-4 g/cm2 per pulse to 4x10-4 g/cm2
per pulse. An optical analysis of the surface morphology
(Fig 2b) had shown that the melting of a TiN-film takes
place under the higher energy density (the TiN melting
temperature is 3227 K). In the case of a lower energy
density (1.4 J/cm2) the melting did not appear (Fig.2c),
but there were observed some flakes and regions of the
SS substrate free of the TiN-film, due to its flaking (or
shelling). Also, various changes in the film color (from
orange or red to dark-blue color) were observed. Similar
TiN-film color changes were observed after a GD
hydrogen- and helium-plasma treatment. In that case the
GD plasma performances and experimental conditions
were similar to those described in Ref [11]. The
irradiation doses were about 1019 ion/cm2, and an
average energy value for ions was about 200 eV. The
samples under studies were palladium pipes (of 0.6 cm
in diameter, 0.025 cm in thickness, and 19 cm in length)
coated with a 3-µm-thick TiN layer. In that case the TiN
deposition conditions were identical to those applied for
the TiN-coated SS-shield or TiN-limiter. Temperatures
of the samples during a plasma treatment were in
different experiments equal to 623-723 K. After the
irradiation with hydrogen- and helium-plasmas drastic
changes in the coating color (from orange to dark blue),
in dependence on a dose and temperature value, were
observed visually. It should be noted that such color
changes were not observed after the irradiation by GD
nitrogen-plasma. Moreover, it was possible to reproduce
the initial film color by an appropriate treatment with
GD nitrogen plasma.
Fig. 1. The erosion value dependence of (a) distance from
plasma source and (b) number of pulses
Fig. 2. TiN-coating surface for (a) non-irradiated sample,
(b) irradiated by 3 pulses at 5.5 J/cm2, (c) irradiated by 3
pulses at 1.4 J/cm2, (d) after10 pulses at 1.4 J/cm2
2.3. Hydrogen permeability of TiN coatings
A bimetallic sample mentioned above, which
consists of a rather thick Pd substrate and a thin TiN
film, is a convenient system in order to measure
hydrogen permeability characteristics of a thin coating.
Applicable experimental method was described in
details in earlier papers [11-12]. It should, however, be
noted that probability of the hydrogen molecule
penetration trough a thin film to the palladium
membrane, during in a single collision process, is in the
most cases much lower than that for bare Pd. Hence, a
157
hydrogen permeability of the bimetallic system can be
considered as the hydrogen permeability in the film
only, with accuracy up to 10%. Within a frame of this
work, there was studied kinetics of the hydrogen
penetration trough TiN films at temperatures of 630 –
870 K, and at the hydrogen pressure of 10 –10-4 Torr.
After 10 hrs baking at 870 K, under pressure of ~10-8
Torr there was applied the constant volume method. In
Fig.3 there is shown a temperature dependence of
probability of the hydrogen penetration through a bare
Pd substrate (curve 1), and through Pd coated with a 3-µ
m-thick TiN layer (curve 3). For a comparison, there are
also shown data for three SS-coated Pd samples (curve
2). It can be seen that a hydrogen permeability of the
TiN-coating is one order of magnitude lower than that
for an uncoated Pd-membrane, and it is several times
lower than that of Pd coated with 3-µm-thick SS.
Fig. 3. Temperature dependence of the probability of
hydrogen permeation through membrane:1-bare palladium; 2-
3µm SS-coated Pd; 3-3µmTiN-coated Pd
The activation energies of permeability, as one can
determine from a slope of the curves presented in Fig.3,
were calculated to be 15.5 kJ/mole for bare Pd, 15
kJ/mole for the TiN coating, and 19.9 kJ/mole for the
SS-coating, respectively. Measurements of the TiN
permeability versus a pressure showed the strong
deviation from the j ~ p0.5 law up to j ~ p/(1+p0.5), where
j represents a rate of the hydrogen permeation through
the membrane.
2.4. Outgassing from TiN-coated stainless steel
A block scheme of the experimental facility, as used
for outgassing behavior investigations by means of
thermal desorption and mass-spectrometry methods,
was similar to that described in Ref. [13]. It comprised
an SS vacuum-chamber, which contained samples, a
monopole mass-spectrometer, and gauges for pressure
measurements. The vacuum chamber was connected
with a turbomolecular pump and a mechanical fore-
pump. The specimens under studies were SS pipes of 32
mm in diameter, 1 mm in thickness, and 140 mm in
length. The SS pipes of the identical sizes were coated
with TiN-layers . The SS strips of the 150 mm x 10 mm
holder construction allowed the samples to be heated up
to 673 K, and it provided the sample exposure to a GD
hydrogen plasma (of about 200 eV, and 1018 ions/cm2).
Before measurements of the outgassing rate, the 3 hrs
baking of the facility at a temperature of 373 K was
performed, and the final pressure po = 6x10-8 Torr was
obtained after the system cooling down to a room
temperature. After that the investigated sample was
heated up to a required temperature value, and the
maximum increase in the total pressure, which was
caused by gases desorbed from the sample, was
measured. At the same time, a mass-spectrum of the
gases was registered during the whole thermal
desorption process. The specific net outgassing rate (q)
was calculated from an equation q = (p – po) S/F, where
S = 50 l/s was the pumping speed, and F was an area of
the heated sample surface facing the vacuum chamber
volume. The measurements were performed with the
same system after its 3-hrs baking at 373 K (curves with
index a), after a 1-hr hydrogen inflow up to pressure of
about 10-4 Torr (index b), and after the GD plasma
treatment (index c). Fig.4 shows that in a temperature
range of 323-523 K the outgassing from the TiN-coated
SS pipes and from theU-3M samples were considerable
higher than that from the SS samples. The registered
mass spectra (Fig.5) showed that the main desorbed
gases were those with the ratio M/e = 18 (H2O), 28 (CO,
N2), and 44 (CO2), respectively. It should, however, be
noted that the desorption kinetics changed dramatically
after an exposure of the samples to a molecular
hydrogen atmosphere under pressure of about 10-4 Torr
(i.e., a typical H2 pressure in the U-3M torsatron during
the discharge cleaning), or to a hydrogen-plasma of an
Fig. 4. Temperature dependence of specific net outgassing
rate q for: (1) - stainless steel tube,(2) - TiN-coated stainless
steel tube, (3) - TiN-coated U-3M shield sample
abnormal GD. In the first case the q value for the TiN-
coated SS showed no change at heating temperatures up
to 473 K, and it was considerably lower than that for the
SS samples (Fig.4). But, with a further increase in
temperature a strong increase in q value was discovered,
up to the values observed for SS without any coating. In
that case the main desorbed gases had the ratio M/e =
28, and 18. It must be noted that, in a comparison with
the bare SS samples, a negligible amount of hydrogen
was desorbed from the TiN-coated SS samples (Fig. 5).
In the second case a considerable increase in q value
was observed after the exposure of the TiN-coated SS
samples to GD hydrogen plasma (see Fig.4, curve 2c).
In Fig.4 and Fig.6 it can also be seen that a similar
character of the outgassing behavior (with some minor
differences) was observed for the TiN-coated samples
made from the U-3M shield.
1 2
Inverse temperature of membrane, 1000/T (K)
Pe
ne
tr
at
io
n
pr
ob
ab
ili
ty
, m
ol
ec
ul
e/
co
lli
si
on
1
2
3
10
-3
-4
-5
300 350 400 450 500 550
Temperature, K
O
ut
ga
ss
in
g
ra
te
, q
, T
or
r.
l/s
.c
m -6
-7
-8
-9
-10
-5
2
1a
1b
2a
2b
2c3a
3b
158
Fig. 5. Mass spectra during baking of stainless steel (1) and
TiN-coated stainless steel (2) at 20°C and 200°C after 3 hours
heating at 100°C (a) and after 1 hour exposure in H2
atmosphere at pressure10-4 Torr (b)
Fig. 6. Mass spectra under baking of TiN-coated samples from
U-3M (1) and TiN-coated SS tube after treatment in glow
discharge plasma (2)
3. Discussion
3.1 Erosion behavior
Erosion behavior and damages of a TiN-coated SS
shield under the hydrogen plasma irradiation are
determined by various processes, e.g. the arcing, the
physical and chemical sputtering, the radiation
enhanced sublimation, etc. In general this behavior
depends on an energy flux density, a sample
temperature, a dose, the impurity concentration, etc. At
low flux densities and low sample temperatures (in lack
of the effective cooling both parameters are
interdependent) the main erosion processes are the
arcing and the physical sputtering. The low values of arc
ignition probability, which were estimated above, might
be due to a low level of the secondary electron emission
from the TiN coating. Such a reason had at least been
called the main one to explain a considerable increase in
the breakdown resistance of a TiN-coated klystron
window [5]. Another important reason can also be
suggested, e.g. well known influence of the surface
cleanness on the arcing probability [14]. After the
cleaning by a plasma discharge, probability of the arc
ignition upon a boron carbide-surface had been
decreased from value of 1.0 (observed for a dirty
surface) to less than 0.1 (achieved for a cleaned surface)
[8]. Taking into account the results of the biased TiN-
limiter experiments, and the obtained TiN outgassing
characteristics, one can suppose that the TiN low
outgassing rate could be one of the main reasons of the
low arcing level. In order to get a direct evidence of
such a mechanism, some additional investigations are
needed.
An enrichment of the Ti population in the nearest-
surface bulk layer and small change in the TiN-film
color (from golden to orange and red only), are main
damages observed at a low energy flux density and low
temperatures. The first effect can be induced by
selective character of the sputtering process, and the
second one can depend on the formation of new
materials caused by interactions of impurities with the
bare coating. When energy flux densities and sample
temperatures are increased, a depth of the defective
near-surface layer is also increased, and intensive color
changes (up to dark-blue color) are observed. Since the
U-3M torsatron is an unbaked facility, the main
impurity during the plasma discharge cleaning and work
plasma discharges constitutes a water vapor. Therefore,
the formation of oxides is possible under an intense
hydrogen plasma irradiation. Strong oxygen and carbon
lines, which were observed during AES investigations
of the irradiated TiN samples described in Ref. [2],
seem to confirm such a mechanism of the film color
changes.
At a high-power plasma flux density some new
processes can appear, e.g. the flaking (shelling), the
melting, the evaporation etc. A thermal shock can lead
to the shelling and flake formation in regions with a
lower film-substrate adhesion (Fig. 2c). Some pieces of
a film material can be carried over from these parts, and
this so-called “shelling” can be the main reason of the
high erosion values, as observed for the TiN-coated SS
samples during several first plasma pulses. It can also be
a reason of a weak dependence of erosion values on the
energy flux density (Fig. 1a). At high-energy fluxes
(about 5.5 J/cm2) the TiN film is melted (Fig. 2b) and
the film material vapors, and its droplets could give a
considerable contribution to the erosion value increase.
That was not demonstrated in Fig. 1a, and a reason of
that phenomenon could be a screening effect of the
target material vapor, similar to that described in paper
[15]. Taking into account the TiN film surface density
(1238 µg/cm2 [2]) and the particle flux density (about
1017 ions/cm2 per 1µs pulse), one can obtain the
approximate value of the TiN-erosion coefficient equal
to about 10 atoms/ion. This value is considerably higher
than that (about 1atom/ion) measured for bare SS under
the similar experimental conditions.
3.2. Permeability
A low value of hydrogen permeability activation
energy for the TiN film (15 kJ/mole) and a strong
deviation from the known j ~ p0.5 law, usual one for a
metallic system, indicate an important role of surface
stages in the permeability process (adsorption and
dissociation). It also suggests a considerable influence
of film porosity on penetration kinetics, as it was
observed for some metal coatings deposited upon
palladium, by means of the arc sputtering of various
cathodes [11-12]. A low hydrogen permeability of the
TiN-coating makes this material a perspective one to be
atomic mass
in
te
ns
ity
[a
.u
.]
in
te
ns
ity
[a
.u
.]
atomic mass
in
te
ns
ity
[a
.u
.]
in
te
ns
ity
[a
.u
.]
20oC
200oC
(1a) 20oC
20oC 20oC
(2a)
200oC
200oC 200oC
(1b) (2b)
2 18 28 44 2 18 28 44
atomic mass
in
te
ns
ity
[a
.u
.]
atomic mass
in
te
ns
ity
[a
.u
.]
2 18 28 44
20oC
200oC
300oC
20oC
200oC
300oC
2 18 28 44
(1) (2)
159
used not only for a reduction of the arcing process upon
surfaces of some plasma-device components. Such a
coating can also be applied in order to reduce the
hydrogen isotopes trapping and inventory by walls of a
plasma machine vacuum-chamber. Also a TiN-Pd
bimetallic diffusion system, placed inside a plasma
device, should be of interest for research on behavior of
hydrogen isotopes, e.g. the so-called "tokamakium" -
new materials formed upon the internal walls of
tokamaks [16] (in torsatrons they could been called
"torsatronium"). On the other hand, such membranes
could be used for an active control of a hydrogen
isotope density near surfaces exposed to high-energy
fluxes, e.g. in order to perform some kind of the gas
puffing for the surface protection. A potential barrier on
the TiN-film and Pd-substrate boundary might be easily
overcome, because hydrogen in Pd material is in
atomized or partially ionized state, similar to plasma
[17]. So, even films with the high-energy hydrogen
coupling are not resistible for the hydrogen penetration
in such systems.
3.3. Outgassing
The measured outgassing rate value for a TiN-coated
SS surface has been found to be several times higher
than that for the bare SS surface within a range from a
room temperature to 500 K (Fig.4). This outgassing
behavior differs considerably from the results described
in Ref. [4], where the TiN outgassing was estimated to
be considerably lower than that for SS in the whole
temperature range. A reason for this difference could be
a different film composition and structure, caused by
different deposition methods and experimental
conditions. The observed effect of the insignificant
outgassing after a hydrogen inflow (Fig.4, curve 2b), as
described in this paper, might have important
consequences for a base ultimate pressure value, the
particle balance, the hydrogen isotopes recycling and
inventory processes in plasma devices, using large TiN
coated surfaces. For example, the ultimate pressure in
the U-3M torsatron po = 4x10-7 Torr could be reduced
several times down to below 10-7 Torr by the TiN
coating of 100 m2 area of the vacuum chamber wall
surface. As a result of that, one might reduce the out-
pumping speed, accordingly. This problem and the
results of the outgassing behavior experiments in situ U-
3M conditions will be discussed in another paper. This
paper considers only one question, arising when large-
surface TiN-coated components are used in plasma
devices. As it has been shown above, the hydrogen
plasma interaction with TiN films can induce drastic
changes in their outgassing behavior. The net outgassing
rate increases, and a considerable hydrogen amount is
desorbed from the TiN coating in the case considered.
This outgassing behavior, under/after the plasma
irradiation, might lead to changes in plasma
performances during experiments.
To explain the considerable outgassing increase after
a GD plasma treatment one can suggest the following
mechanism. Under a bombardment by neutral atoms and
ions, impurities can be rapidly desorbed into plasma and
after that they can be partially ionized and partially are
pumped out, together with an inflowing hydrogen gas.
During this process the TiN surface can be selectively
sputtered, and the Ti enrichment can take place in the
coating nearest surface layer. Titanium can actively
absorb impurities, and at certain temperatures the
formation of oxides, carbides, and another compounds,
can occur. If a sputtering coefficient is low (this is
usually in order to 10-2 per ion under physical
sputtering [18]), impurities and new composition
materials can be accumulated within the coating surface
layer. It can lead to drastic changes in the TiN
outgassing behavior, and it can cause damages as well
as the film color changes described above.
4. Conclusions
The results of the biased TiN-limiter experiments as
well as the simulation experiments, which were
performed with glow-discharges and plasma
accelerators, confirmed the high arc erosion resistance
of TiN-coated stainless-steel surfaces. One can combine
this effect with the measured low level of the TiN
hydrogen permeability and the observed effect of a
negligible outgassing from TiN under certain
conditions. Hence, one can suppose a wider use of TiN-
coated components for the wall conditioning in plasma
devices, for an active control of the erosion and
recycling processes, and for other technologies. Direct
plasma interactions with the TiN-modificated surfaces
must, however, be excluded in order to eliminate drastic
changes in the outgassing behavior and in the coating
surface-layer composition.
References
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|
| id | nasplib_isofts_kiev_ua-123456789-78559 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T20:33:56Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Glazunov, G.P. Volkov, E.D. Veremeyenko, V.P. Kosik, N.A. Kutsyn, Al.A. Langner, J. Langner, E. Mironov, Yu.K. Nazarov, N.I. Piekoszewski, J. Sadowski, M. Stanislawski, J. Tereshin, V.I. 2015-03-18T19:20:18Z 2015-03-18T19:20:18Z 2000 Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation / G.P. Glazunov, E.D. Volkov, V.P. Veremeyenko, N.A. Kosik, Al.A. Kutsyn, J. Langner, E. Langner, Yu.K. Mironov, N.I. Nazarov, J. Piekoszewski, M. Sadowski, J. Stanislawski, V.I. Tereshin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 155-159. — Бібліогр.: 18 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/78559 533.9 An erosion behavior of TiN-coated stainless-steel (SS) surfaces was investigated during biased-limiter experiments within the Uragan-3M torsatron and during simulation experiments, which were performed with plasma-accelerator and glow-discharge (GD) plasmas. For a TiN-coated SS head-plate of a limiter the arc ignition probability was found to be lower than 10-4 per plasma pulse. Possible physical mechanisms of this effect had been discussed. Within special vacuum stands, using thermal-desorption and mass-spectrometry methods, there were performed measurements of an outgassing rate and hydrogen permeability of TiNcoatings. The negligible outgassing from TiN-coated SS samples, during their heating up to 473 K, was observed after a cleaning procedure with a molecular hydrogen inflow under pressure of about 10-4 Torr, on contrary to the considerable increase of (q) rate for the irradiated samples. Measured values of the TiN-film hydrogen permeability were several times lower, and activation energy of the hydrogen permeation was considerably lower than that for the SS films (15 kJ/mole instead of 19.9 kJ/mole). The use of TiN-coated SS and diffusion membranes, for the reduction of the erosion, recycling, and hydrogen isotope inventory control, as well as for improvement of vacuum conditions, has been considered. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Low temperature plasma and plasma technologies Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation Article published earlier |
| spellingShingle | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation Glazunov, G.P. Volkov, E.D. Veremeyenko, V.P. Kosik, N.A. Kutsyn, Al.A. Langner, J. Langner, E. Mironov, Yu.K. Nazarov, N.I. Piekoszewski, J. Sadowski, M. Stanislawski, J. Tereshin, V.I. Low temperature plasma and plasma technologies |
| title | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| title_full | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| title_fullStr | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| title_full_unstemmed | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| title_short | Erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| title_sort | erosion, permeation and outgassing performances of tin coating under/after hydrogen plasma iffadiation |
| topic | Low temperature plasma and plasma technologies |
| topic_facet | Low temperature plasma and plasma technologies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78559 |
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