Coagulation and dynamics nanoparticles in low pressure plasma jets
One of the most promising methods for creating nanostructured films is the use of plasma jets of low pressure with nanoparticles. In this case, it is important to control the size of the nanoparticles, their temperature and energy to optimize the properties of the films. In this paper, using compute...
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irk-123456789-1947122023-11-29T11:17:27Z Coagulation and dynamics nanoparticles in low pressure plasma jets Kravchenko, O.Yu. Maruschak, I.S. Low temperature plasma and plasma technologies One of the most promising methods for creating nanostructured films is the use of plasma jets of low pressure with nanoparticles. In this case, it is important to control the size of the nanoparticles, their temperature and energy to optimize the properties of the films. In this paper, using computer simulations, a study is conducted on coagulation of nanoparticles in a plasma jet that expands into rarefied gas. In our model, we use a hydrodynamic model for describing the dynamics of a plasma with a multidisperse phase, as well as a sectional method for describing the coagulation of nanoparticles. At the entrance to the plasma torch, the plasma parameters were stationary, and the dust particles were considered the same size. Calculations were made at various concentrations of dust particles in the plasma jet. The simulation results show that nanoparticles of various sizes appear in the plasma stream as a result of coagulation. With increasing distance from the inlet, the average modulus charge and the dispersion of the charge of nanoparticles decreases due to the decrease in the temperature of the ions and, consequently, the ion current on the dust particles. Одним з найбільш перспективних методів створення наноструктурованих плівок є використання плазмових струменів низького тиску з наночастинками. При цьому для оптимізації властивостей плівок важливим є контроль за розміром наночастинок, їх температурою та енергією. У цій роботі за допомогою комп’ютерного моделювання проводиться дослідження коагуляції наночастинок у плазмовому струмені, який розширюється в розріджений газ. У нашій моделі використовуються гідродинамічна модель для описання динаміки плазми з мультидисперсною фазою, а також секційний метод для описання коагуляції наночастинок. На вхідному отворі плазмового факела параметри плазми задавалися стаціонарними, а пилові частинки вважалися одного розміру. Розрахунки проводилися при різних концентраціях пилових частинок у плазмовому струмені. Результати моделювання показують, що в потоці плазми внаслідок коагуляції з’являються наночастинки різних розмірів. Зі збільшенням відстані від вхідного отвору зменшуються середній заряд по модулю та дисперсія заряду наночастинок, що пов’язано із зменшенням температури іонів та, відповідно, іонного струму на пилову частинку. Одним из наиболее перспективных методов создания наноструктурированных пленок является использование плазменных струй низкого давления с наночастицами. При этом для оптимизации свойств пленок важным является контроль за размером наночастиц, их температурой и энергией. В работе с помощью компьютерного моделирования проводится исследование коагуляции наночастиц в плазменной струе, которая расширяется в разреженный газ. В нашей модели используются гидродинамическая модель для описания динамики плазмы с мультидисперсною фазой, а также секционный метод для описания коагуляции наночастиц. На входном отверстии плазменного факела параметры плазмы задавались стационарными, а пылевые частицы считались одного размера. Расчеты проводились при различных концентрациях пылевых частиц в плазменной струе. Результаты моделирования показывают, что в потоке плазмы вследствие коагуляции появляются наночастицы различных размеров. С увеличением расстояния от входного отверстия уменьшаются средний заряд по модулю и дисперсия заряда наночастиц, что связано с уменьшением температуры ионов и, соответственно, ионного тока на пылевую частицу. 2019 Article Coagulation and dynamics nanoparticles in low pressure plasma jets / O.Yu. Kravchenko, I.S. Maruschak // Problems of atomic science and technology. — 2019. — № 1. — С. 172-175. — Бібліогр.: 12 назв. — англ. 1562-6016 PACS: 52.27.Lw http://dspace.nbuv.gov.ua/handle/123456789/194712 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies Kravchenko, O.Yu. Maruschak, I.S. Coagulation and dynamics nanoparticles in low pressure plasma jets Вопросы атомной науки и техники |
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One of the most promising methods for creating nanostructured films is the use of plasma jets of low pressure with nanoparticles. In this case, it is important to control the size of the nanoparticles, their temperature and energy to optimize the properties of the films. In this paper, using computer simulations, a study is conducted on coagulation of nanoparticles in a plasma jet that expands into rarefied gas. In our model, we use a hydrodynamic model for describing the dynamics of a plasma with a multidisperse phase, as well as a sectional method for describing the coagulation of nanoparticles. At the entrance to the plasma torch, the plasma parameters were stationary, and the dust particles were considered the same size. Calculations were made at various concentrations of dust particles in the plasma jet. The simulation results show that nanoparticles of various sizes appear in the plasma stream as a result of coagulation. With increasing distance from the inlet, the average modulus charge and the dispersion of the charge of nanoparticles decreases due to the decrease in the temperature of the ions and, consequently, the ion current on the dust particles. |
format |
Article |
author |
Kravchenko, O.Yu. Maruschak, I.S. |
author_facet |
Kravchenko, O.Yu. Maruschak, I.S. |
author_sort |
Kravchenko, O.Yu. |
title |
Coagulation and dynamics nanoparticles in low pressure plasma jets |
title_short |
Coagulation and dynamics nanoparticles in low pressure plasma jets |
title_full |
Coagulation and dynamics nanoparticles in low pressure plasma jets |
title_fullStr |
Coagulation and dynamics nanoparticles in low pressure plasma jets |
title_full_unstemmed |
Coagulation and dynamics nanoparticles in low pressure plasma jets |
title_sort |
coagulation and dynamics nanoparticles in low pressure plasma jets |
publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2019 |
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Low temperature plasma and plasma technologies |
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http://dspace.nbuv.gov.ua/handle/123456789/194712 |
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Coagulation and dynamics nanoparticles in low pressure plasma jets / O.Yu. Kravchenko, I.S. Maruschak // Problems of atomic science and technology. — 2019. — № 1. — С. 172-175. — Бібліогр.: 12 назв. — англ. |
series |
Вопросы атомной науки и техники |
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AT kravchenkooyu coagulationanddynamicsnanoparticlesinlowpressureplasmajets AT maruschakis coagulationanddynamicsnanoparticlesinlowpressureplasmajets |
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2025-07-16T22:10:56Z |
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2025-07-16T22:10:56Z |
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1837843203070361600 |
fulltext |
ISSN 1562-6016. ВАНТ. 2019. №1(119)
172 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2019, № 1. Series: Plasma Physics (25), p. 172-175.
COAGULATION AND DYNAMICS NANOPARTICLES IN LOW
PRESSURE PLASMA JETS
O.Yu. Kravchenko, I.S. Maruschak
Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
E-mail: kay@univ.kiev.ua
One of the most promising methods for creating nanostructured films is the use of plasma jets of low pressure
with nanoparticles. In this case, it is important to control the size of the nanoparticles, their temperature and energy
to optimize the properties of the films. In this paper, using computer simulations, a study is conducted on
coagulation of nanoparticles in a plasma jet that expands into rarefied gas. In our model, we use a hydrodynamic
model for describing the dynamics of a plasma with a multidisperse phase, as well as a sectional method for
describing the coagulation of nanoparticles. At the entrance to the plasma torch, the plasma parameters were
stationary, and the dust particles were considered the same size. Calculations were made at various concentrations of
dust particles in the plasma jet. The simulation results show that nanoparticles of various sizes appear in the plasma
stream as a result of coagulation. With increasing distance from the inlet, the average modulus charge and the
dispersion of the charge of nanoparticles decreases due to the decrease in the temperature of the ions and,
consequently, the ion current on the dust particles.
PACS: 52.27.Lw
INTRODUCTION
Plasma-assisted technologies represent important
tools for deposition of nanostructured films on substrates.
The growth of thin and ultra-thin films may be achieved
using a large variety of techniques such as chemical
vapour deposition, RF sputtering, pulsed laser deposition
or plasma enhanced chemical vapour deposition [1-3].
Recently, a new process, which uses a plasma torch
operating at low pressure has been developed with the
aim of depositing uniform thin layers on large surfaces
[4, 5]. In this plasma spraying process plasma jets are
used as a heat sources to melt and accelerate the injected
nanoparticles which subsequently impinge and solidify
on a substrate. Modelling the nanoparticles, which create
and assemble the film it is possible to enhance the
physical properties of thin films. As is known,
nanoparticles have the ability to coagulate, resulting in a
change in their size. This process can be significant in
plasma and it must be taken into account when
transporting nanoparticles to a substrate in a plasma jet. It
is important to be able to control the size of the
nanoparticles, their kinetic energy, the temperature and
the magnitude of the flow on the substrate.
The aim of this work is to simulate the dynamics and
coagulation of nanoparticles in a plasma jet expanding
through a round hole into a dilute gas.
1. MODEL AND SIMULATION METHOD
In this paper, the expansion of an axially symmetric
plasma jet with nanoparticles into a rarefied neutral gas is
studied. A hydrodynamic model is used to describe a
problem that takes into account the processes of
coagulation of dust particles. At the initial moment of time,
it is assumed that the plasma flows through a circular hole
into a space filled with neutral gas. The plasma consists of
neutral argon atoms, single charge ions, electrons and dust
particles. It was believed that at the initial moment of time
dust particles were of the same radius 4dr nm . The
plasma flow velocity at the inlet was v0=40 m/s, plasma
pressures were in the range of 4 to 80 mbar.
To describe the problem, a hydrodynamic model is
used, which is described in [6]. This model includes
continuity equations for ions, atoms and dust particles
0,
n
div nw
t
/ ,i
i i d
n
div n w I n e
t
0d
d d
n
div n w
t
,
momentum equations for heavy plasma particles (ions
and atoms) and dust particles
1
,d r
i r
i i i
nu n fP e
div nuw n E
t m r m m
1
,d z
i z
i i i
nv n fP e
div nvw n E
t m z m m
,
d d d d r d
d d d d r
d d d
n u n f qP
div n u w n E
t m r m m
,
d d d d z d
d d d d z
d d d
n v n f qP
div n v w n E
t m z m m
equations for internal energies ions and atoms ,
electrons
e and dust particles
d
,
enei ddiv w Pdiv w Q Q n Q
t
,
e
e e e
ei en d ed
div w P div w divq
t
Q Q n Q
d d
d d d d d ed iddiv w n Q n Q Q
t
.
Here , ,d in n n are the sum of ion and neutral atom
concentrations, dust particles and ion concentrations
respectively; ,w u v and ,d d dw u v are drift
ISSN 1562-6016. ВАНТ. 2019. №1(119) 173
velocities of plasma and dust component; , eP P are
partial pressures of the heavy plasma component and
electrons. In these equations , , Qed idQ Q are the energy
exchanges between a dust particle and neutral atoms,
electrons and ions;
eiQ is the energy exchange between
electrons and ions;
enQ is the energy exchange between
electrons and neutrals [6].
In this model, we believe that all dust particles have
a single hydrodynamic velocity, since they effectively
exchange impulse in collisions. This velocity differs
from the hydrodynamic velocity of the plasma
component. We also note that due to the low plasma
pressure we allow for a difference between the
temperature of the electrons and the temperature of the
heavy plasma particles (ions and neutrals), as well as the
surface temperature of dust particles.
The system of hydrodynamic equations is solved
numerically by the method of large particles [7].
To determine the distribution of nanoparticles by
charge, we use the model proposed in [8, 9]. This model
takes into account the stochastic nature of the charging
of dust particles associated with the chaos of the thermal
motion of electrons and ions. As a result, dust particles
with different charges are present in each elemental
volume of plasma. Nanoparticles in the plasma are
charged because of collisions with electrons and ions.
The electron and ion currents collected by a dust
particle in the nanometer regime can be described by the
orbital-motion-limited (OML) probe theory [10]. A
particle with radius
dr which carries a charge
kZ k e (with e the elementary charge and k an
integer) is charged to a surface potential of
0/ 4k k dZ r , with
0 the vacuum dielectric
constant. Using OML theory, expressions for the
frequency with which a particle with charge
kZ is hit by
electrons and ions, respectively, can be derived
,
, , , ,
,
exp , 0
e i kk
e i e i e i e i k
B e i
q
n Sv q
k T
,
, , , ,
,
1 , 0.
e i kk
e i e i e i e i k
B e i
q
n Sv q
k T
Here 24 dS r is the particle surface area,
1/2
, , ,/ 2e i B e i e iv k T m is the electron (ion) thermal
velocity;
,e in stands for the electron and ion densities,
,e im and
,e iT are the mass and temperature of electrons
and ions, respectively, and
,e iq e is the respective
charge,
Bk is Boltzmann constant.
The charge distribution of particles of a given radius
dr is described by the fraction of particles kF carrying
a charge k e . It is normalized by 1k
k
F . The rate
equation for a charge state k can then be written as
1 1
1 1.
k k k kk
e k e k i k i k
dF
F F F F
dt
It is assumed that the charging of particles is much
faster than coagulation so the charge distribution can be
considered in steady state [9]. This assumption enables
the use of recursive relations for the charge distribution
1 1
k
i
k kk
e
F F
.
In addition, in the presented model, coagulation of
dust particles is considered, which is described by the
model proposed in [11,12]. The volume distribution
function of dust particles ( )n v is described by the
general dynamic equation
0
0
( ) 1
( , ) ( ) ( )
2
( , ) ( ) ( ) ,
v
n v
v v v n v n v v dv
t
v v n v n v dv
where v is the volume of the dust particle, ( )dvn v
denotes the particle number density in a volume range
[ , ]v v dv . Coefficient ( , )v v is the frequency for
coagulation between two particles with a volume v and
v´. According to [11], ( , )v v is given
1/2
1/6 1/2
2
1/3 1/3
63 1 1
( , ) ( , )
4
,
B
p
k T
v v v v
v v
v v
where v and v´ are the volumes of the particles
interacting,
p is the density of the particles, and T is
the temperature of the particles. (v, v ) is a coefficient
which describes that the effective cross section for
coagulation depends on the charge of both particles
( , ) ( ) (v )Q(k,k , v, v )k k
k k
v v F v F
with
2
0
2
0
( , , , ) exp , 0
4
1 , 0,
4
s B
s B
kk e
Q k k v v kk
R k T
kk e
kk
R k T
and
1/3
1/3 '1/33
.
4
sR v v
2. RESULTS AND DISCUSSION
Fig. 1 shows distributions on the charge of
nanoparticles of a radius 4dr nm at different
distances from the inlet. Here is the fraction of
particles with charge . As can be seen from the
figure, with increasing the average charge of the
nanoparticles decreases in absolute value.
The obtained results are explained by the fact that
when the distance from the inlet of the plasma jet
increases, the temperature of the ions decreases rapidly,
and the electrons temperature remains practically
unchanged due to their high thermal conductivity. This
leads to an increase in the flow of ions on the surface of
the dust particles and, consequently, to a decrease in its
negative charge.
174 ISSN 1562-6016. ВАНТ. 2019. №1(119)
-10 -5 0
0,0
0,1
0,2
0,3
k
F
z=0
z=0.005 m
z=0.02 m
a
Fig. 1. Distributions by charge of nanoparticles at
different distances from the inlet of plasma jet
-20 -10 0
0,0
0,1
0,2
q
d
/e
z=0.01 m
d0
/
0
=0.05
d0
/
0
=0.2
E
Fig. 2. Distributions by charge of nanoparticles at
z = 0.001 m from the inlet of plasma jet for different
dust densities
Consider now how the concentration of
nanoparticles in the plasma jet affects their charge
distributions. In Fig. 2 depicts the charge distributions
of nanoparticles with a radius rd = 4 nm for two modes:
at d0/0=0.05 and d0/0=0.2. Here d0 is a dust
density, 0 is a plasma density at the inlet of the plasma
torch. The plasma density in these modes was
0=0.122 kg/m
3
. As can be seen, the decrease in the
density of dust particles leads to a shift of the charge
distribution of dust particles in the region of negative
charges. This result is because when the concentration
of negatively charged dust particles increases, the
concentration of electrons decreases (due to the quasi-
neutrality of the plasma). This leads to a decrease in the
electron current to the dust particles.
Consider now the coagulation of nanoparticles in a
plasma jet. Fig. 3 shows axial profiles along the jet axis
of the dust particles densities on a semi-logarithmic
scale for different their radii. In this mode of calculation,
the concentration of nanoparticles at the inlet was
nd = 5∙10
-9
m
-3
, and their radius was rd = 4∙10
-9
m. We can
see that nanoparticles with rd >4 nm appear in the
plasma jet, the maxima of densities which are at a
certain distance from the inlet. This can be explained by
the coagulation of dust particles in the plasma jet. As a
result of this process, the concentration of nanoparticles
with a radius exceeds the concentration of
particles which are injected through the inlet (with a
radius ) at .
0,000 0,025 0,050
10
3
10
8
10
13
10
18
z, m
n
d
, m
-3 r
d
=4 nm
r
d
=4.7 nm
r
d
=5.3 nm
r
d
=7 nm
Fig. 3. Axial profiles on jet axis of the dust densities for
different their radii
Fig. 4 shows the distributions of nanoparticles by
their radius at different distances from the inlet. These
results correspond to the calculation mode presented in
Fig. 3. As can be seen, because of the coagulation, at a
distance from the inlet z = 0.001 m in the plasma appear
particles of different radii. When increasing the distance
to the inlet, the number of particles of larger radii first
increases and then decreases. Decrease in
concentrations of dust particles is due to the expansion
of the plasma jet.
4,0x10
-9
6,0x10
-9
8,0x10
-9
1,0x10
-8
10000
1E9
1E14
1E19
n
d
, m
-3
r
d
, m
z=0.001 m
z=0.01 m
z=0.03 m
Fig. 4. Distributions of dust particles by their radius at
different distances from the inlet of plasma jet
CONCLUSIONS
In this work, a sectional model that is
selfconsistently coupled to a plasma fluid model was
used to conduct numerical simulations of a low-pressure
plasma jet in which nanoparticles grow due to
coagulation. The simulation was carried out at different
plasma pressures, and the concentration of dust particles
at the inlet of the plasma torch. As a result of the
calculations, the spatial distributions of the plasma
parameters, size and charge distributions of
nanoparticles in the different points of space have been
obtained. Influence of nanoparticle coagulation on the
parameters of a plasma jet and the dynamics of
nanoparticles is studied. It is shown that due to
coagulation in the jet appear dust particles of larger
radii. The maximum concentrations of these particles
are at some distance from the inlet. We found that with
the increase of the distance from the inlet due
ISSN 1562-6016. ВАНТ. 2019. №1(119) 175
to the decrease of the ion temperature, the average
charge of dust particles per module and the width of
their distribution by charge decreases. When the density
of dust particles in the jet increases, their average charge
decreases modulo due to a decrease of the electron
density in the plasma, which leads to an increase of the
coagulation rate of nanoparticles.
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Article received 15.12.2018
КОАГУЛЯЦИЯ И ДИНАМИКА НАНОЧАСТИЦ В ПЛАЗМЕННЫХ СТРУЯХ
НИЗКОГО ДАВЛЕНИЯ
А.Ю. Кравченко, И.С. Марущак
Одним из наиболее перспективных методов создания наноструктурированных пленок является
использование плазменных струй низкого давления с наночастицами. При этом для оптимизации свойств
пленок важным является контроль за размером наночастиц, их температурой и энергией. В работе с
помощью компьютерного моделирования проводится исследование коагуляции наночастиц в плазменной
струе, которая расширяется в разреженный газ. В нашей модели используются гидродинамическая модель
для описания динамики плазмы с мультидисперсною фазой, а также секционный метод для описания
коагуляции наночастиц. На входном отверстии плазменного факела параметры плазмы задавались
стационарными, а пылевые частицы считались одного размера. Расчеты проводились при различных
концентрациях пылевых частиц в плазменной струе. Результаты моделирования показывают, что в потоке
плазмы вследствие коагуляции появляются наночастицы различных размеров. С увеличением расстояния от
входного отверстия уменьшаются средний заряд по модулю и дисперсия заряда наночастиц, что связано с
уменьшением температуры ионов и, соответственно, ионного тока на пылевую частицу.
КОАГУЛЯЦІЯ І ДИНАМІКА НАНОЧАСТИНОК У ПЛАЗМОВИХ СТРУМЕНЯХ НИЗЬКОГО
ТИСКУ
О.Ю. Кравченко, І.С. Марущак
Одним з найбільш перспективних методів створення наноструктурованих плівок є використання
плазмових струменів низького тиску з наночастинками. При цьому для оптимізації властивостей плівок
важливим є контроль за розміром наночастинок, їх температурою та енергією. У цій роботі за допомогою
комп’ютерного моделювання проводиться дослідження коагуляції наночастинок у плазмовому струмені,
який розширюється в розріджений газ. У нашій моделі використовуються гідродинамічна модель для
описання динаміки плазми з мультидисперсною фазою, а також секційний метод для описання коагуляції
наночастинок. На вхідному отворі плазмового факела параметри плазми задавалися стаціонарними, а пилові
частинки вважалися одного розміру. Розрахунки проводилися при різних концентраціях пилових частинок у
плазмовому струмені. Результати моделювання показують, що в потоці плазми внаслідок коагуляції
з’являються наночастинки різних розмірів. Зі збільшенням відстані від вхідного отвору зменшуються
середній заряд по модулю та дисперсія заряду наночастинок, що пов’язано із зменшенням температури іонів
та, відповідно, іонного струму на пилову частинку.
https://scholar.google.com/citations?view_op=view_citation&hl=ru&user=h4MzsJcAAAAJ&citation_for_view=h4MzsJcAAAAJ:u-x6o8ySG0sC
https://scholar.google.com/citations?view_op=view_citation&hl=ru&user=h4MzsJcAAAAJ&citation_for_view=h4MzsJcAAAAJ:u-x6o8ySG0sC
https://scholar.google.com/citations?view_op=view_citation&hl=ru&user=h4MzsJcAAAAJ&citation_for_view=h4MzsJcAAAAJ:u-x6o8ySG0sC
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