Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation
The properties of Ti41Zr38.3Ni20.7 thin films under radiation-thermal action of hydrogen plasma with a surface heat load of 0.2 MJ/m² was studied at the QSPA Kh-50 quasi-stationary plasma accelerator (NSC KIPT). The phase composition, structural state, and surface morphology were studied using X-ray...
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| Cite this: | Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation / S.V. Malykhin, V.V. Kondratenko, V.A. Makhlai, I.E. Garkusha, I.A. Kopylets, Yu.S. Borisov, S.S. Herashchenko, S.V. Surovitskiy, S.S. Borisova // Problems of Atomic Science and Technology. — 2022. — № 6. — С. 143-148. — Бібліогр.: 30 назв. — англ. |
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Malykhin, S.V. Kondratenko, V.V. Makhlai, V.A. Garkusha, I.E. Kopylets, I.A. Borisov, Yu.S. Herashchenko, S.S. Surovitskiy, S.V. Borisova, S.S. 2023-12-08T11:02:14Z 2023-12-08T11:02:14Z 2022 Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation / S.V. Malykhin, V.V. Kondratenko, V.A. Makhlai, I.E. Garkusha, I.A. Kopylets, Yu.S. Borisov, S.S. Herashchenko, S.V. Surovitskiy, S.S. Borisova // Problems of Atomic Science and Technology. — 2022. — № 6. — С. 143-148. — Бібліогр.: 30 назв. — англ. 1562-6016 PACS: 52.40.HF DOI: https://doi.org/10.46813/2022-142-143 https://nasplib.isofts.kiev.ua/handle/123456789/195908 The properties of Ti41Zr38.3Ni20.7 thin films under radiation-thermal action of hydrogen plasma with a surface heat load of 0.2 MJ/m² was studied at the QSPA Kh-50 quasi-stationary plasma accelerator (NSC KIPT). The phase composition, structural state, and surface morphology were studied using X-ray diffraction and scanning electron microscopy. It was found that the quasicrystalline phase and related crystalline phases, the Laves phase, the α-solid solution, and the 2/1 phase of the Ti-Zr-Ni approximant crystal were stable under irradiation with up to 20 hydrogen plasma pulses. The phase composition did not change. It is shown that the changes in the coatings mainly manifest themselves as changes in the substructure of the observed phases. With an increase in the plasma exposure dose, the structure of the quasicrystalline icosahedral phase improves, and the size of the coherence regions increases. In the films consisting of crystalline phases, a partial phase transformation is observed with a redistribution of components between the 2/1 phase of the approximant crystal and the α-solid solution phase. It was found that thin films of the Ti-Zr-Ni system containing a quasicrystalline icosahedral phase, irradiated with radiation-thermal plasma pulses, are less prone to cracking than coatings with crystalline phases of the same system. На квазістаціонарному плазмовому прискорювачі КСПП Х-50 (ННЦ ХФТІ) досліджено характеристики тонких плівок Ti41Zr38.3Ni20.7 при радіаційно-термічному впливі водневої плазми з тепловим навантаженням на поверхню 0,2 МДж/м². Фазовий склад, структурний стан та морфологія поверхні були досліджені методами рентгенівської дифракції та скануючої електронної мікроскопії. Встановлено, що квазікрісталічна фаза, а також споріднені з нею кристалічні фази: фаза Лавеса, α-твердий розчин і фаза 2/1 кристала-апроксиманта Ti-Zr-Ni-системи виявилися стійкими при опроміненні до 20 імпульсів водневої плазми. Фазовий склад якісно не змінюється. Показано, що зміни, які відбуваються в покриттях, в основному проявляються як зміни в субструктурі спостережуваних фаз. Структура квазікристалічної ікосаедричної фази з накопиченням імпульсів впливу вдосконалюється, і розмір областей когерентності збільшується. У плівках, що складаються з кристалічних фаз, спостерігається часткове фазове перетворення з перерозподілом компонентів між фазою 2/1 кристала-апроксиманта і фазою α-твердого розчину. Встановлено, що тонкі плівки Ti-Zr-Ni-системи, що містять квазікристалічну ікосаедричну фазу, при радіаційно-термічних навантаженнях у сумі 20 імпульсами менш схильні до утворення тріщин, ніж покриття з кристалічними фазами тієї ж системи. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Problems of Atomic Science and Technology Low temperature plasma and plasma technologies Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation Поведінка тонких плівок квазікристалів і апроксімантних фаз системи Ti-Zr-Ni при радіаційно-термічній дії в режимах перехідних процесів Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation |
| spellingShingle |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation Malykhin, S.V. Kondratenko, V.V. Makhlai, V.A. Garkusha, I.E. Kopylets, I.A. Borisov, Yu.S. Herashchenko, S.S. Surovitskiy, S.V. Borisova, S.S. Low temperature plasma and plasma technologies |
| title_short |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation |
| title_full |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation |
| title_fullStr |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation |
| title_full_unstemmed |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation |
| title_sort |
stability of thin quasi-crystalline ti-zr-ni films and related crystalline phases under low-energy transient plasma irradiation |
| author |
Malykhin, S.V. Kondratenko, V.V. Makhlai, V.A. Garkusha, I.E. Kopylets, I.A. Borisov, Yu.S. Herashchenko, S.S. Surovitskiy, S.V. Borisova, S.S. |
| author_facet |
Malykhin, S.V. Kondratenko, V.V. Makhlai, V.A. Garkusha, I.E. Kopylets, I.A. Borisov, Yu.S. Herashchenko, S.S. Surovitskiy, S.V. Borisova, S.S. |
| topic |
Low temperature plasma and plasma technologies |
| topic_facet |
Low temperature plasma and plasma technologies |
| publishDate |
2022 |
| language |
English |
| container_title |
Problems of Atomic Science and Technology |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Поведінка тонких плівок квазікристалів і апроксімантних фаз системи Ti-Zr-Ni при радіаційно-термічній дії в режимах перехідних процесів |
| description |
The properties of Ti41Zr38.3Ni20.7 thin films under radiation-thermal action of hydrogen plasma with a surface heat load of 0.2 MJ/m² was studied at the QSPA Kh-50 quasi-stationary plasma accelerator (NSC KIPT). The phase composition, structural state, and surface morphology were studied using X-ray diffraction and scanning electron microscopy. It was found that the quasicrystalline phase and related crystalline phases, the Laves phase, the α-solid solution, and the 2/1 phase of the Ti-Zr-Ni approximant crystal were stable under irradiation with up to 20 hydrogen plasma pulses. The phase composition did not change. It is shown that the changes in the coatings mainly manifest themselves as changes in the substructure of the observed phases. With an increase in the plasma exposure dose, the structure of the quasicrystalline icosahedral phase improves, and the size of the coherence regions increases. In the films consisting of crystalline phases, a partial phase transformation is observed with a redistribution of components between the 2/1 phase of the approximant crystal and the α-solid solution phase. It was found that thin films of the Ti-Zr-Ni system containing a quasicrystalline icosahedral phase, irradiated with radiation-thermal plasma pulses, are less prone to cracking than coatings with crystalline phases of the same system.
На квазістаціонарному плазмовому прискорювачі КСПП Х-50 (ННЦ ХФТІ) досліджено характеристики тонких плівок Ti41Zr38.3Ni20.7 при радіаційно-термічному впливі водневої плазми з тепловим навантаженням на поверхню 0,2 МДж/м². Фазовий склад, структурний стан та морфологія поверхні були досліджені методами рентгенівської дифракції та скануючої електронної мікроскопії. Встановлено, що квазікрісталічна фаза, а також споріднені з нею кристалічні фази: фаза Лавеса, α-твердий розчин і фаза 2/1 кристала-апроксиманта Ti-Zr-Ni-системи виявилися стійкими при опроміненні до 20 імпульсів водневої плазми. Фазовий склад якісно не змінюється. Показано, що зміни, які відбуваються в покриттях, в основному проявляються як зміни в субструктурі спостережуваних фаз. Структура квазікристалічної ікосаедричної фази з накопиченням імпульсів впливу вдосконалюється, і розмір областей когерентності збільшується. У плівках, що складаються з кристалічних фаз, спостерігається часткове фазове перетворення з перерозподілом компонентів між фазою 2/1 кристала-апроксиманта і фазою α-твердого розчину. Встановлено, що тонкі плівки Ti-Zr-Ni-системи, що містять квазікристалічну ікосаедричну фазу, при радіаційно-термічних навантаженнях у сумі 20 імпульсами менш схильні до утворення тріщин, ніж покриття з кристалічними фазами тієї ж системи.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/195908 |
| citation_txt |
Stability of thin quasi-crystalline Ti-Zr-Ni films and related crystalline phases under low-energy transient plasma irradiation / S.V. Malykhin, V.V. Kondratenko, V.A. Makhlai, I.E. Garkusha, I.A. Kopylets, Yu.S. Borisov, S.S. Herashchenko, S.V. Surovitskiy, S.S. Borisova // Problems of Atomic Science and Technology. — 2022. — № 6. — С. 143-148. — Бібліогр.: 30 назв. — англ. |
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ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142).
Series: Plasma Physics (28), p. 143-148. 143
https://doi.org/10.46813/2022-142-143
STABILITY OF THIN QUASI-CRYSTALLINE Ti-Zr-Ni FILMS
AND RELATED CRYSTALLINE PHASES UNDER LOW-ENERGY
TRANSIENT PLASMA IRRADIATION
S.V. Malykhin
1
, V.V. Kondratenko
1
, V.A. Makhlai
1,2,3
, I.E. Garkusha
2,3
, I.A. Kopylets
1
,
Yu.S. Borisov
1
, S.S. Herashchenko
2,3
, S.V. Surovitskiy
1
, S.S. Borisova
1
National Technical University “Kharkiv Polytechnical Institute”, Kharkiv, Ukraine;
2
Institute of Plasma Physics, National Science Center
“Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine;
3
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
E-mail: malykhin@kpi.kharkov.ua
The properties of Ti41Zr38.3Ni20.7 thin films under radiation-thermal action of hydrogen plasma with a surface
heat load of 0.2 MJ/m
2
was studied at the QSPA Kh-50 quasi-stationary plasma accelerator (NSC KIPT). The phase
composition, structural state, and surface morphology were studied using X-ray diffraction and scanning electron
microscopy. It was found that the quasicrystalline phase and related crystalline phases, the Laves phase, the α-solid
solution, and the 2/1 phase of the Ti-Zr-Ni approximant crystal were stable under irradiation with up to 20 hydrogen
plasma pulses. The phase composition did not change. It is shown that the changes in the coatings mainly manifest
themselves as changes in the substructure of the observed phases. With an increase in the plasma exposure dose, the
structure of the quasicrystalline icosahedral phase improves, and the size of the coherence regions increases. In the
films consisting of crystalline phases, a partial phase transformation is observed with a redistribution of components
between the 2/1 phase of the approximant crystal and the α-solid solution phase. It was found that thin films of the
Ti-Zr-Ni system containing a quasicrystalline icosahedral phase, irradiated with radiation-thermal plasma pulses, are
less prone to cracking than coatings with crystalline phases of the same system.
PACS: 52.40.HF
INTRODUCTION
A feature of the structure of icosahedral quasicrystals
(QCs) is the combination of rotational symmetry of the
fifth order with a strict aperiodic long-range order at the
disposal of atoms in the absence of translational
invariance [1]. Therefore, QCs are characterized by
anomalous and unique physical properties, in particular,
high strength and low thermal conductivity [2]. For
icosahedral quasicrystals of the Ti-Zr-Ni system, the
ability to accumulate a large (up to 2 H/at.) amount of
hydrogen in the form of a solid solution is known [2-4].
The lack of periodicity implies increased stability under
radiation and thermal exposure [5-7]. The widespread
use of quasicrystals in bulk and ribbon forms is
hindered by their high fragility. It is believed [8] that the
use of thin-film coatings on metal substrates solves this
problem. We assume that the film quasicrystalline
Ti-Zr-Ni coating can perform the functions of thermal
protection, prevention of hydrogen embrittlement, and
resistance to blistering. Steel elements with
quasicrystalline coatings can be used as structural-
functional elements of a fusion reactor. Previously, we
worked out a laboratory technique for the formation of
coatings with an icosahedral quasicrystalline phase with
a fairly perfect structure. The features of the formation
of thin-film coatings with quasicrystalline and
crystalline phases of the Ti-Zr-Ni system are described
in detail in [9, 10]. According to the first experiments on
the modification of crystalline Ti-Zr-Ni phases, the
formation of the quasicrystalline and crystal-
approximant phases occurs as a result of high-speed
quenching under pulsed action with a heat load of
0.6 MJ/m
2
. The changes in the contents of these phases
as well as in their structure and substructure parameters
were studied during isothermal vacuum annealing at a
temperature of 550 °C and also after irradiation with 5
plasma pulses in the range of heat loads from 0.1 to
0.4 MJ/m
2
. The quasicrystalline phase was found to be
resistant to irradiation with hydrogen plasma [11, 12].
In this work, the aim is to analyze and compare the
behavior of thin Ti-Zr-Ni films containing the
quasicrystalline and crystalline phases under low-energy
plasma irradiation.
1. SAMPLES AND INVESTIGATION
TECHNIQUE
Coatings with a thickness of 5.7 μm were prepared
by dc-magnetron sputtering of a
Ti41Zr38.3Ni20.7 (at.%) target. Austenitic steel
12H18N10T was used as a substrate. The substrate
temperature during deposition did not exceed 40...50 ºС.
After deposition, the samples were annealed in a
vacuum chamber with a limiting pressure of about 1∙10
-4
Pa. Two samples were used in the experiment. Sample 1
was annealed at a temperature of 500 ºС for 4 hours,
and sample 2 at a temperature of 700 ºС for 3 hours.
The annealing modes were chosen based on the data of
our previous studies [9, 10] so that the quasicrystalline
phase was formed in the first sample and crystalline
phases – in the second. The samples were irradiated
with fluxes of hydrogen plasma on a QSPA Kh-50
quasi-stationary plasma accelerator (NSC KIPT). The
mailto:malykhin@kpi.kharkov.ua
144 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142)
main parameters of the QSPA plasma fluxes were as
follows: ion energy of about 0.4 keV, a maximum
plasma pressure of 0.32 MPa, and a flux diameter of
about 18 cm. The pulse duration was 0.25 ms. The
maximum number of pulses was 20. The thermal load
on the irradiated surface was chosen equal to 0.2 MJ/m
2
,
which did not imply melting of the sample surface.
The structure and phase composition were
investigated by the XRD method. The measurements
were carried out on a DRON-type apparatus in filtered
Cu-Kα radiation. The spectra were processed using the
New_Profile 3.5 software package. The quasicrystalline
phase was identified and its quasicrystalline parameter
aq was determined according to J.W. Cahn [13].
Crystalline phases were identified using the JCPDS card
index [14] and the PowderCell software package. The
study of surface morphology and elemental
microanalysis were carried out using scanning electron
microscopy (SEM) on a JEOL JSM-6390 device.
2. RESULTS AND DISCUSSION
2.1. CHARACTERIZATION OF THE INITIAL
STATE
The X-ray diffraction patterns of samples in the
initial state are presented in Fig. 1. Processing of
diffraction patterns and subsequent phase analysis
showed that sample № 1 (after annealing at 500 C)
consists of a single icosahedral quasicrystalline phase (i-
phase, i-QC) (Fig. 1,a). Its reflections in the figure are
marked with two indices by J. Kahn. The quasi-
crystallinity parameter is aq = 0.5234 nm, and the half-
width (B) of the (20, 32) reflection is about 17.4 μrad.
One of the proofs that this is really a quasicrystalline
phase is the presence of multiple orders of reflections,
for example (20, 32) and (52, 84), in which the
interplanar distances differ strictly by the “golden
number” = 1.618.
The phase composition of sample № 2 after
annealing at a higher temperature turned out to be more
complex. It was found that the sample contains three
phases. All of them are crystalline. These are the Laves
(L), (Ti,Zr)2Ni phase with the C14structural type, the α-
Ti(Zr) solid solution phase with approximately equal
titanium and zirconium contents, and the 2/1 crystal-
approximant phase (Fig. 1,b). The existence of the first
two phases is in full agreement with the data of the
phase diagram given in [15-17]. The existence of the 2/1
crystal-approximant phase in the system under
consideration was first established by us in [9]. The
crystal lattice parameters of the phases are:
a = 0.310 nm and c = 0.495 nm for the α-phase;
a = 0.5282 nm and c = 0.8304 nm for the L-phase; and
2.3321 nm for the 2/1 approximant phase. In Fig. 1,b,
reflections from phases are labeled as L, α, and 2/1 for
the Laves phase, solid solution, and approximant
respectively.
2.2. PLASMA IRRADIATION RESULTS
The change in the shape of the diffraction pattern of
sample № 1 as a result of irradiation with hydrogen
plasma is shown in Fig. 2. Fig. 2,a represent the section
of diffraction patterns obtained for sample № 1 in the
initial state, Fig. 2,b – after irradiation with 0.2 MJ/m
2
with 5 pulses, Fig. 2,c – after10 pulses, and Fig. 2,d – 20
pulses. It can be seen from the figure that the number
and intensity of reflections from the quasicrystalline
phase increase with an increase in the plasma irradiation
dose.
In addition, a redistribution of intensity between
reflections (18, 29) and (20, 32) is observed. The greater
the number of irradiation pulses N, the higher the reflection
intensity (18, 29). This ratio of intensities is consistent with
the theoretical calculation performed in [13], and it is
associated with the number of equivalent crystallographic
planes (repeatability factor). In the literature [18-20],
however, for bulk and ribbon samples, different data are
given for the intensity ratio I(18, 29)/I(20, 32). It can be assumed
that this discrepancy is due to the presence of texture in the
samples associated with the method of preparation. Also,
the redistribution of the intensity between reflections
during cyclic heating-cooling can be associated with
changes in the preferred orientation of quasicrystalline
grains. This is also further evidenced by an increase in the
number of reflections and an increase in their intensities.
We note that irradiation does not lead to the appearance of
reflections not characteristic of the i-phase; that is, the i-
phase turns out to be resistant to irradiation with a thermal
load of 0.2 MJ/m
2
.
Fig. 1. X-ray diffraction patterns recorded in the Cu-Кα
radiation for sample № 1 annealed at a temperature of
500 C (a) and sample № 2 annealed at a temperature
of 700 C (b) in the initial state (before irradiation)
Fig. 2. Section of diffraction patterns from sample № 1
in the initial state (a) and after irradiation with
0.2 MJ/m
2
with 5 pulses (b),
10 pulses (c), and 20 pulses (d)
ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142) 145
With the accumulation of the number of irradiation
pulses, the positions of the reflections shift and their
width decreases. The reflections are displaced towards
larger diffraction angles. The value of the displacement,
recalculated into the change in the value of the
quasicrystallinity parameter, is shown in Fig. 3.
Fig. 3. Change in the quasicrystallinity parameter with
accumulation of the number of pulses under irradiation
with hydrogen plasma of sample № 1
It can be concluded that, with the accumulation of
the number of irradiation pulses, a monotonic and rather
significant decrease in the quasicrystallinity parameter
aq occurs. One of the possible reasons for the decrease
in the parameter could be a change in the elemental
composition of the phase. However, according to the
results of microprobe analysis, changes in the elemental
composition of the films do not exceed ± 2 at.%, which
is comparable with the measurement accuracy. Another
reason for the decrease in the parameter aq may be the
accumulation of vacancies of thermal and deformation
nature [21]. According to calculations [22, 23], the
reason for their formation may be the thermal cycling of
samples in the temperature range from room
temperature to 850...900 C. We believe that the
radiation component does not play a significant role,
and this issue was studied earlier [11].
The changes in the width of (18, 29) and (20, 32)
reflections are shown in Fig. 4, squares and circles
respectively. It can be observed that for a small (up to 5)
number of irradiation pulses N, the width practically
does not change, and at larger values of N, the width of
the reflections decreases. Since the chosen reflections
are located at small diffraction angles and, therefore,
weakly depend on the content of phason defects [13,
24], we assume that the decrease in width is associated
with an increase in the coherence length (CL) as a result
of thermal action. The attainable absolute reflection
width of ≈ 11 μrad corresponds to CL of approximately
15 nm.
The changes in the diffraction patterns of sample
№ 2 with an increase in the number of plasma
irradiation pulses, are shown in Fig. 5, in particular
Fig. 5,a – in the initial state, Fig. 5,b – after irradiation
with 0.2 MJ/m
2
with 2 pulses, Fig. 5,c – after 15 pulses,
and Fig. 5,d – 20 pulses. For the present phases, the
irradiation leads to a relative change in the intensity of
reflections, a shift in their positions, and a change in
width. Reflection indices are given in Fig. 1. The largest
increase in the reflection intensity and width is observed
for the α-Ti (Zr) solid solution phase. For the Laves
phase (L), a relative decrease in the reflection intensity
is observed, while for the phase of the crystal
approximant 2/1, there is a slight increase. Changes in
the positions of the reflections, recalculated into the
parameters of the crystal lattices, are shown in Fig. 6.
Fig. 4. Relative change in the width of reflections
(18, 29) (squares) and (20, 32) (circles) as a result
of plasma irradiation of sample № 1
28 30 32 34 36 38 40 42 44 46 48 50 52 54
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
2
/1
2
/1
(2
0
2
)L
(0
0
4
)L
(1
0
0
)
2
/1
(1
1
2
)L
2
/1
(1
0
1
)
(0
0
2
)
(1
1
0
)L
(1
0
2
)L
(1
0
0
)
2
/1
d
In
te
n
s
it
y
,
p
u
ls
/s
2, deg.
b
a
c
Fig. 5. Sections of diffraction patterns from sample № 2
in the initial state (a) and after irradiation with
0.2 MJ/m
2
: 2 pulses (b), 15 pulses (c), and 20 pulses (d)
It is noticeable that the parameters of the crystal
lattice of the Laves phase do not practically change with
the accumulation of the number of irradiation pulses
(Fig. 6,a). The nature of the change in the lattice
parameters of the solid solution and the 2/1 crystal-
approximant phase turned out to be the same and
nonmonotonic (seFig. 6,b and Fig. 6,c respectively).
A decrease is observed until the number of impulses is
10...15, and then an increase follows. The relative
decrease in a/a was -0.013 for the 2/1 approximant
phase, which coincides with c/c = -0.014. At the same
time, a/a = -0.023 for α-Ti (Zr), which is significantly
higher than the previous values. At the same time,
a/a = -0.023 for α-Ti (Zr), which is significantly
higher than the previous values. We believe that the
changes in the reflection intensities and structure
parameters of the phases indicate the occurrence of
phase transformations stimulated by radiation-thermal
action. In addition to phase changes typical for sample
№ 2, irradiation causes a change in the half-width of
reflections from the phases present. The relative change
in the width B/B with an increase in the number of
irradiation pulses is shown in Fig. 7. It follows from the
figure that, in contrast to sample № 1, with increasing
the number of irradiation pulses N, the width of
reflections increases for all phases (see Fig. 7 curve 1–
4).
146 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142)
The largest change in B/B is characteristic of the
Laves phase (see Fig. 7 curve 1 and curve 4), the
smallest for the solid solution (see Fig. 7 curve 2).
Since the analyzed reflections are located at small
diffraction angles, all broadening is due to the effect of
phase crystallite fragmentation.
0 5 10 15 20
0.510
0.515
0.520
0.525
0.530
0.535
0.820
0.825
0.830
0.835
0.840
0.845
0.850
c
L
,
n
m
a
L
,
n
m
N, pulse a
0 5 10 15 20
0,300
0,305
0,310
0,480
0,485
0,490
0,495
0,500
c
,
n
m
a
,
n
m
N, pulse b
0 5 10 15 20
2,300
2,305
2,310
2,315
2,320
2,325
2,330
2,335
a
2
/1
,
n
m
N, pulse c
Fig. 6. Changes in the lattice periods of the L-phase (a),
phase α-(Ti, Zr) of a solid solution (b),
and phase 2/1 – approximant (c) of sample № 2
depending on the number of plasma pulses
Based on the absolute value of the reflection width,
we find the fragmentation of crystallites of the Laves
phase from the initial 30 nm to 8 nm; the size of the
crystallites of the phase 2/1 approximant reduced from
25 to 12 nm, and the crystallites of the α-phase from
20 nm to 10 nm. Fig. 7 curve 4 also shows the change in
the width of the (302) Laves phase reflection located at
medium diffraction angles, for which the total
broadening includes the contribution of microstrains.
It can be stated that even the first irradiation causes a
sharp jump in B/B and then the increase becomes
flattered in comparison with B/B for the L-phase (202)
reflection (see Fig. 7 curve 1). This means that at the
initial moment of impact, microstresses accumulate,
and, consequently, dislocations randomly located inside
the crystallites; and when the crystallites are
fragmented, they can go into the sinks. According to
[25], such a change in the width, as in Fig. 7, indicates
the actual accumulation of defects of the second class,
such as dislocations and large dislocation loops, the
deformation fields from which propagate over
considerable distances. It is possible that the
accumulation and accompanying annealing of defects is
the reason for the formation of a system of cracks on the
surface of the samples (Fig. 8). The formation of cracks
upon irradiation of materials with hydrogen plasma in
modes simulating transient phenomena in a fusion
reactor is a common phenomenon, and was studied
earlier on tungsten samples [26].
0 5 10 15 20
0
1
2
3
4
B
/B
N, pulse
1
2
3
4
Fig. 7. Relative changes in the width of reflections:
(202) of the L-phase (1); (101) of the α-(Ti, Zr) solid
solution phase (2) ;(821) of the 2/1-approximant
phase (3), and (302) of the L-phase (4) of sample № 2
depending on the number of plasma pulses
Fig. 8 shows that in sample № 2 (Fig. 8,c,d)
containing crystalline phases, the number of cracks per
unit area is greater than in the sample № 1 (Fig. 8,a,b).
The cracks have a sinuous, broken shape, characteristic
of crystalline materials. In sample № 1 the cracks have a
smooth appearance, typical for glass. We observed
similar cracks earlier when coatings were irradiated
with a heat load of up to 0.6 MJ/m
2
[27]. The relief
observed in Fig. 8,b,d qualitatively resembles the
phenomenon of ablation during pulsed thermal action
on materials with poor thermal conductivity.
DISCUSSIONS
According to calculations performed in [22, 23], the
surface of tungsten samples is heated up to 850 C at a
thermal load of hydrogen plasma of 0.2 MJ/m
2
. In the
Ti-Zr-Ni system, the quasicrystalline phase is stable up
to 660 C, and then undergoes a reverse eutectoid
transformation with the formation of the Laves phase
and the solid α-Ti (Zr) solution [16]. However,
according to the above results, the quasicrystalline
phase in sample № 1, like the phases of sample № 2,
turned out to be resistant to the radiation-thermal action
of plasma, and the phase composition did not
qualitatively change after irradiation even with 20 pulses.
ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142) 147
a
b
c
d
Fig. 8. Change in the surface morphology of the film
coating № 1 (a, b) and № 2 (c, d) as a result of
irradiation with 20 hydrogen plasma pulses with a load
of 0.2 MJ/m
2
This means that the bulk of the sample № 1 material
was not heated above 600 C. The reason may be the low
thermal conductivity inherent in quasicrystals [2]. We
assume that all the energy of the plasma beam supplied in
a short time of the pulse is accumulated in a very thin
surface layer and causes its melting.
This can explain the development of the surface relief,
which is observed in Fig. 8,b,d. It is known that when a
material is heated to the melting temperature, excess
vacancies are formed [28], and inhomogeneous heating
creates tensile residual stresses in the surface layers [29,
30], which ensure a flow of vacancies into the inner
layers of the coating. As a manifestation of this effect, we
observe a decrease in the quasicrystallinity parameter as a
result of irradiation. As for sample № 2, we also note
surface melting. In addition, taking into consideration the
changes in the intensities of reflections and the
parameters of the crystal lattices of the phases present, we
admit the occurrence of partial phase transformations
caused by irradiation. In this case, the heating of the
sample should have been above the eutectoid equilibrium
temperature of ≈ 600 C. This equilibrium is shown in the
polythermal section on the three-component diagram of
the Ti-Zr-Ni system given in [16]. According to the
Gibbs phase rule, this equilibrium must be established
between the four phases. In [16], there are only three of
them. We argue that the fourth missing phase is the 2/1
approximant crystal phase. This is an intermediate high-
temperature phase, possibly up to the melting of the
eutectic. The existence of approximant phases with a
number of atoms in the cluster more than in the Bergman
cluster, as well as their position on the phase diagram,
were primarily considered theoretically in [15]. The
straight line of eutectoid equilibrium is actually a section
of a certain plane in space. At temperatures above
600 C, three phases should be in equilibrium, which is
what we observe. It is in the heating – cooling mode
during irradiation that a partial phase transformation
occurs between them. The content of the α-solid solution
phase clearly becomes larger. Even according to [16], if
at 600 C the ratio of the masses of α-Ti (Zr) and the
Laves phase is 1/3, then already at ≈ 800 C, it is ≈ 0.9.
The content of nickel in the α-solid solution increases.
Since the lattice parameters of the Laves phase do not
change, we assume that the main redistribution of the
components occurs between the α-solid solution and the
2/1 crystal-approximant phases, which is manifested in
the behavior of the curves in Fig. 6. We noted earlier that
the largest decrease in the a/a values was observed for
the solid solution. Since this is associated with a change
in the interatomic distance in the most closely packed
plane (000l), we assume that large titanium or zirconium
atoms are replaced in it by smaller nickel atoms, which
pass from the crystal-approximant phase. The relative
content of the solid solution increases.
CONCLUSIONS
It was experimentally established that the
quasicrystalline phase, as well as related crystalline
phases (Laves phase, α-solid solution, and 2/1 crystal-
approximant phase) of the Ti-Zr-Ni system, turned out
to be stable under conditions of radiation-thermal
exposure to hydrogen plasma with a heat load of
0.2 MJ/m
2
at the QSPA Kh-50 quasi-stationary plasma
accelerator.
It is shown that the inherent changes mainly manifest
themselves in the form of a change in the substructure, as
well as a partial phase transformation with a
redistribution of components between the 2/1 crystal-
approximant phase and the α-solid solution phase.
148 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №6(142)
It was found that under radiation-thermal loads in a
total of 20 pulses, thin films of the Ti-Zr-Ni system
containing a quasicrystalline icosahedral phase are less
prone to crack formation than coatings with crystalline
phases of the same system.
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Article received 10.09.2022
ПОВЕДІНКА ТОНКИХ ПЛІВОК КВАЗІКРИСТАЛІВ І АПРОКСІМАНТНИХ ФАЗ СИСТЕМИ
Ti-Zr-Ni ПРИ РАДІАЦІЙНО-ТЕРМІЧНОЇ ДІЇ В РЕЖИМАХ ПЕРЕХІДНИХ ПРОЦЕСІВ
С.В. Малихін, В.В. Кондратенко, В.О. Махлай, І.Є. Гаркуша, І.А. Копилець,
Ю.С. Борисов, С.С. Геращенко, С.В. Суровицький, С.С. Борисова
На квазістаціонарному плазмовому прискорювачі КСПП Х-50 (ННЦ ХФТІ) досліджено характеристики
тонких плівок Ti41Zr38.3Ni20.7 при радіаційно-термічному впливі водневої плазми з тепловим
навантаженням на поверхню 0,2 МДж/м
2
. Фазовий склад, структурний стан та морфологія поверхні були
досліджені методами рентгенівської дифракції та скануючої електронної мікроскопії. Встановлено, що
квазікрісталічна фаза, а також споріднені з нею кристалічні фази: фаза Лавеса, α-твердий розчин і фаза 2/1
кристала-апроксиманта Ti-Zr-Ni-системи виявилися стійкими при опроміненні до 20 імпульсів водневої
плазми. Фазовий склад якісно не змінюється. Показано, що зміни, які відбуваються в покриттях, в
основному проявляються як зміни в субструктурі спостережуваних фаз. Структура квазікристалічної
ікосаедричної фази з накопиченням імпульсів впливу вдосконалюється, і розмір областей когерентності
збільшується. У плівках, що складаються з кристалічних фаз, спостерігається часткове фазове перетворення
з перерозподілом компонентів між фазою 2/1 кристала-апроксиманта і фазою α-твердого розчину.
Встановлено, що тонкі плівки Ti-Zr-Ni-системи, що містять квазікристалічну ікосаедричну фазу, при
радіаційно-термічних навантаженнях у сумі 20 імпульсами менш схильні до утворення тріщин, ніж покриття
з кристалічними фазами тієї ж системи.
|