Energy characteristics of spherical glow discharge
The ultimate goal of this study is optimization of the modification processes, namely the constructional details’ surface nitriding, based on the using of glow discharge (GD). These processes are studied both experimentally and theoretically in spherical abnormal GD plasma in N2-Ar mixture. The ba...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2011
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irk-123456789-908872016-04-15T13:54:59Z Energy characteristics of spherical glow discharge Zhovtyansky, V.A. Anisimova, O.V. Khomych, V.O. Lelyukh, Yu.I. Nazarenko, V.G. Tkachenko, Ya.V. Низкотемпературная плазма и плазменные технологии The ultimate goal of this study is optimization of the modification processes, namely the constructional details’ surface nitriding, based on the using of glow discharge (GD). These processes are studied both experimentally and theoretically in spherical abnormal GD plasma in N2-Ar mixture. The balance equations for the density of charged particles and Poisson equation added with equation for heat conductivity are taken into account in the theoretical part of investigation. The last equation describes the influence of the hot cathode on the processes in discharge volume. As is shown, the correct account of the anode fall of potential plays a key role to represent adequately the volt-ampere characteristic of the spherical GD. Кінцевою метою цієї роботи є оптимізація процесів модифікації на основі використання жевріючого розряду (ЖР), а саме азотування поверхні конструкційних деталей. Ці процеси вивчені експериментально і теоретично в плазмі аномального сферичного ЖР у суміші N2-Ar. У теоретичній частині роботи розглянуто рівняння балансу концентрації заряджених частинок і рівняння Пуассона, доповнені рівнянням теплопровідності. Останнє з них описує вплив гарячого катода на процеси в розрядному об’ємі. Показано також, що коректне урахування прианодного падіння потенціалу відіграє ключову роль для адекватного моделювання вольт-амперної характеристики сферичного ЖР. Конечной целью данной работы является оптимизация процессов модификации, основанных на использовании тлеющего разряда (ТР), а именно азотирования поверхности конструкционных деталей. Эти процессы изучены экспериментально и теоретически в плазме аномального сферического ТР в смеси N2-Ar. В теоретической части работы рассмотрены уравнения баланса для плотности заряженных частиц и уравнение Пуассона, дополненные уравнением теплопроводности. Последнее из них описывает влияние горячего катода на процессы в разрядном объеме. Показано также, что корректный учет прианодного падения потенциала играет ключевую роль для адекватного моделирования вольт-амперной характеристики сферического ТР. 2011 Article Energy characteristics of spherical glow discharge / V.А. Zhovtyansky, O.V. Anisimova, V.O. Khomych, Yu.I. Lelyukh, V.G. Nazarenko, Ya.V. Tkachenko // Вопросы атомной науки и техники. — 2011. — № 1. — С. 95-97. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 51.50.+v, 52.25.Dg, 52.80.Hc http://dspace.nbuv.gov.ua/handle/123456789/90887 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии |
| spellingShingle |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии Zhovtyansky, V.A. Anisimova, O.V. Khomych, V.O. Lelyukh, Yu.I. Nazarenko, V.G. Tkachenko, Ya.V. Energy characteristics of spherical glow discharge Вопросы атомной науки и техники |
| description |
The ultimate goal of this study is optimization of the modification processes, namely the constructional details’
surface nitriding, based on the using of glow discharge (GD). These processes are studied both experimentally and
theoretically in spherical abnormal GD plasma in N2-Ar mixture. The balance equations for the density of charged
particles and Poisson equation added with equation for heat conductivity are taken into account in the theoretical part of
investigation. The last equation describes the influence of the hot cathode on the processes in discharge volume. As is
shown, the correct account of the anode fall of potential plays a key role to represent adequately the volt-ampere
characteristic of the spherical GD. |
| format |
Article |
| author |
Zhovtyansky, V.A. Anisimova, O.V. Khomych, V.O. Lelyukh, Yu.I. Nazarenko, V.G. Tkachenko, Ya.V. |
| author_facet |
Zhovtyansky, V.A. Anisimova, O.V. Khomych, V.O. Lelyukh, Yu.I. Nazarenko, V.G. Tkachenko, Ya.V. |
| author_sort |
Zhovtyansky, V.A. |
| title |
Energy characteristics of spherical glow discharge |
| title_short |
Energy characteristics of spherical glow discharge |
| title_full |
Energy characteristics of spherical glow discharge |
| title_fullStr |
Energy characteristics of spherical glow discharge |
| title_full_unstemmed |
Energy characteristics of spherical glow discharge |
| title_sort |
energy characteristics of spherical glow discharge |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2011 |
| topic_facet |
Низкотемпературная плазма и плазменные технологии |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/90887 |
| citation_txt |
Energy characteristics of spherical glow discharge / V.А. Zhovtyansky, O.V. Anisimova, V.O. Khomych, Yu.I. Lelyukh, V.G. Nazarenko, Ya.V. Tkachenko // Вопросы атомной науки и техники. — 2011. — № 1. — С. 95-97. — Бібліогр.: 11 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-06T19:04:05Z |
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2025-07-06T19:04:05Z |
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1836925474427633664 |
| fulltext |
ENERGY CHARACTERISTICS OF SPHERICAL GLOW DISCHARGE
V.А. Zhovtyansky, O.V. Anisimova, V.O. Khomych, Yu.I. Lelyukh,
V.G. Nazarenko, Ya.V. Tkachenko
Institute of Gas, National Academy of Sciences of Ukraine, Kiev, Ukraine
E-mail: zhovt@ukr.net
The ultimate goal of this study is optimization of the modification processes, namely the constructional details’
surface nitriding, based on the using of glow discharge (GD). These processes are studied both experimentally and
theoretically in spherical abnormal GD plasma in N2-Ar mixture. The balance equations for the density of charged
particles and Poisson equation added with equation for heat conductivity are taken into account in the theoretical part of
investigation. The last equation describes the influence of the hot cathode on the processes in discharge volume. As is
shown, the correct account of the anode fall of potential plays a key role to represent adequately the volt-ampere
characteristic of the spherical GD.
PACS: 51.50.+v, 52.25.Dg, 52.80.Hc
1. ENERGY EFFICIENCY CRITERION
FOR THE NITRIDING PROCESS
The abnormal glow discharges (GD) are widely used
in the processes of metal surface nitriding as they provide
maximal localization of the technological action on a
treated surface. Unfortunately, a lot of publications in this
area are limited, mainly, to empirically obtain general rule
regarding application of plasma as technological
atmospheres. It does not allow making the strict analysis
of energy efficiency parameters. A basis of analytical
methods for optimization mentioned should be the careful
analysis of physical processes in the plasmas as
technological atmospheres.
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2011. № 1. 95
Series: Plasma Physics (17), p. 95-97.
There is no common viewpoint concerning the
mechanism of diffusion saturation of metal surface with
nitrogen. Now, the substantial attention is attracted to
studying the ion-molecular reactions which run in the
processes of surface modification. It was pointed out that
the efficiency of such processes in N2 plasma is mostly
governed by metastable atomic nitrogen N* [1] (see also
papers [2, 3]), having two characteristic radiation lifetimes
of 1.4×105 and 6.1×104 s in their two metastable states.
Therefore, N* is the best agent to transfer the excitation
energy obtained in plasma to the surface of a solid. Really,
a typical free path of neutral particles in N2 atmosphere at
the pressures 0.1…150 Pa changes from about 35 to
2.3×10-2 cm, respectively. Hence, N* has plenty of chances
to get from the plasma region to the surface of a solid
without collisions. Just collisions are able to transit an atom
from a metastable into the ground state.
Thus, as the energy efficiency criterion of nitriding
process the ratio between atomic nitrogen stream
diffusion on a surface of material to be processed and
electric discharge power may be considered. The higher
the ratio, the higher is the energy efficiency of nitriding.
Plasma forming mixes of N2 with Ar impurity have
considerable advantages in nitriding processes as atomic
nitrogen can effectively be generated in this mix [4]. GD
plasma is sharply nonequilibrium and the strict analysis of
atomic nitrogen producing is a challenge. Moreover,
essential meaning have nonlocal effect in near cathode
GD area which are a subject of active research during last
years (see, for example, [5]). In turn, methods of direct
experimental definition of nitrogen atoms density Na in
plasma are difficult enough, as application of vacuum
spectroscopy methods [1] demands. Besides, they do not
allow predicting character of relationship between Na and
GD parameters.
2. EXPERIMENT
The discharge plasma is generated in nitrogen or N2-
Ar mixture at the pressure 50…250 Pа and discharge
current I ≤ 120 mA. The constructional details to be
modified (samples) were placed on the metal plate
(cathode) 5 cm in diameter at the central part of the
vacuum camera (anode) with a volume of 0.1 m3 [3]. The
temperature of cathode was controlled by a thermocouple.
The density of charged particles Ne and the electric field E
were measured by double probes that could be moved
along the radius of the chamber. GD was powered by
rectified voltage U up to 1500 V and the volt-ampere
characteristics (VAC) were measured too.
The process of nitriding was performed after
evacuation of the chamber and preliminary treatment
(cleaning) of the samples at the satellite discharge in pure
argon. Actually nitriding was effected by GD in a N2-Ar
mixture. The temperature of the plate (and, hence, of the
samples) during the process was maintained within
810…820º K due to the energy supply from GD powered
at UI ~ 60 Wt.
This system was approximated as spherical diode in
numerical simulation [6, 7]. The following values of
parameters were considered in calculations: rK = 1.5 cm
and R = 33 cm are the radii of the internal and the
external spheres of diode, respectively. The calculations
were performed for values of the discharge current
density 2…20 mA/cm2 that is corresponding with the
interval of calculations carried out in [8]. In turn, in some
cases for experimental studies spherical cathode of
molybdenum was also used.
3. VAC OF THE SPHERICAL GD
As it is well known, despite the influence of nonlocal
effects, the estimated VAC of GD in fluid model is well
correspond to the real. This is due to the fact that only a
small part of the fast electrons from their total number is
responsible for these effects [5].
mailto:zhovt@ukr.net
Previously we simulated spherical GD, paying special
attention to the problem of adequate description of the
diffusion processes [7]. The role of the latter can be very
significant at low pressures. The system of fluid equations
was solved
( )2
2
1 ( ) 0,e e
d r J E J
r dr
α− = ( )2
2
1 ( ) 0,i e
d r J E J
r dr
α+ =
(1)
,e
e e e e
96
dND N E J
dr
μ− + = ,i
i i i
dN
iD N E J
dr
μ− + =
(2)
( ) ( )2
2
0
1 ,e i
d er E N N
r dr ε
= −
(3)
where Je and Ji are the densities of the electron and ion
flows, respectively (J = e(Ji + Je)); α(E) is the first
Townsend coefficient; De, μe, Di, μi are the diffusion and
mobility coefficients of electrons and ions, respectively; e
is the electron charge, and ε0 is the dielectric constant.
The boundary conditions for problem (1) – (3) were
initially formulated in a manner like [8] as follows:
0),1/(, =+== ϕγγγ Keie JeJJJ , (4)
Ni = 0, eJe = JA, dNe/dr = 0, (5)
at the cathode and the anode, respectively; here JK and JA
are current densities at the cathode and the anode, γ = 0,02
denotes the coefficient of electron secondary emission
from the cathode. The problem (1) – (5) was solved by
modified method of continuation of the solution with
respect to a parameter [6, 7].
The set of solutions of upper equations allows to
determine theoretically obtained VAC of DC and to
compare it with experimental one. As may be seen in
Fig. 1 this comparison demonstrates only slight
quantitative consistency between two groups of VAC.
400
600
800
1000
1200
1400
1600
0 0.02 0.04 0.06 0.08 0.1 0.12
U, V
I, A
1
4
3
5
2
6
Fig. 1. Volt-ampere characteristics of spherical glow
discharge (rc = 1,5 cm): experimentally obtained
(solid lines) and numerically calculated (dotted lines):
p = 50 (1, 4), 120 (2, 5) and 250 Pa (3, 6)
In particular, numerical simulation (1) – (5)
demonstrates a significant level of potential fall on the
positive column GD that is about half of the total voltage
drop on the discharge gap. This contradicts to the results
of experimental determination of potential distribution
along the diode radius by floating probe method. It does
not fix appreciable electric field in the positive column. In
this connection the role of the processes near the anode
was specified by method of numerical experiment. In this
case the principle of minimum power supply in GD was
used in fact [9]. The setting of numerical experiment
become possible due to high efficiency of computational
procedure for GD mathematical model, proposed in [6, 7].
During the numerical experiment was changed last of
the boundary conditions (5) on the anode. Namely,
instead of condition dNe/dr = 0 was introduced value of
electron density on the anode Nea. It was varied during the
process of numerical experiment. The radial distribution
of potential in positive column was radically changed
under threshold value of this condition Nea in simulation
(Nea*~3.8×109 cm-3 at a pressure 133 Pa, jk = 20 mA/cm2).
In this case the electric field was decreased on the order
of value in the positive column and the positive fall of
potential value of several volts took place near the anode.
The nature of this phenomenon is generation of charge
particles in anode fall of potential (AF) [10]. Due to
admitting of ions from AF region into positive column is
providing ionic component of discharge current that is
resulted in the lowering of potential on the GD. The set of
GD VAC is shown in Fig. 2 as illustration of the role of
adequate account of the processes on the anode.
300
500
700
900
1100
1300
1500
0 0.02 0.04 0.06 0.08 0.1 0.12
U, V
I, A
1
2
3
4
5
Fig. 2. Volt-ampere characteristics of spherical glow
discharge at a pressure 100 Pa (rK =1,5 cm):
experimentally obtained (solid line 1) and numerically
calculated (dotted lines): with account AF
(TK = 800 K (2) and TK = 300 K (3))
and without AF (TK = 800 K (4) and TK = 300 K (5))
The reason of the numerical experiment was the fact
that the processes on the anode were presented as the
anode spots located on the sharp edges of vacuum
chamber. This system is quite complex for its formal
description. However, the results obtained during the
numerical experiment reflect adequately the major role
that performs these spots – filling a gap discharge with
positive ions that compensate space charge. All the basic
laws of so introduced AF in our case correspond well to
their experimental study [10].
The influence of the cathode temperature on the
processes in discharge volume might be taken into
account to further improvement in agreement
experimentally obtained and numerically calculated VAC.
For this purpose the set of equation (1) – (5) was added
with equation for heat conductivity:
01 2
2 =⎟
⎠
⎞
⎜
⎝
⎛
dr
dTr
dr
d
r
κ . (6)
Here κ is heat conductivity coefficient [8]:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
Ω
⋅
=
−
R
Mc
M
T p354,0115,010334,8
)2,2(2
4
σ
κ , (7)
where M – molar mass, Ω(2,2) = 1,157(71.4/t)0.1472, σ =
3.68 Aº, R = 8,314 J/(mol K).
97
With account of this equation the temperature of gas
in discharge volume is changed from 810…820 K at the
cathode to 400 K at the distance 5 cm from it.
As may be seen from Fig. 2 by comparing the curves 1
and 2, the system of equation (1) – (2) allows describing
adequately enough real VAC of GD in the process of
nitriding. The further improving may be consisted with
the account of current change of the temperature of
cathode (plate) due to variation of energy supply with
grow of voltage U on the discharge gap.
4. CONCLUSIONS
The complex study of glow discharge presented in this
paper as a whole may be used for optimization of the
modification processes from the view point of energy
efficiency. Strictly speaking the electric discharge power
is not parameter of the technology presented in this paper.
Really, in the process of nitriding energy supply of GD in
maintained on the level of UI ~ 60 Wt to stabilize the
temperature of samples to be processed within
810…820 K. Nevertheless these results allow determining
quantitatively the basic parameters of GD depending of
pressure. The way how to use these parameters as well as
to determine the percentage composition of N2-Ar
mixture as technological atmosphere to optimize the
process of nitriding is presented in paper [11].
REFERENCES
1. T. Nakano, T. Kitajima, S. Samukawa, T. Makabe.
Diagnostics of N2 and O2 dissociation in RF plasmas
by vacuum ultraviolet emission and absorption //
Abstracts of the XXVIII Int. Conf. on Phenomena in
Ionized Gases, Prague 15-20 July, 2007 / Institute of
Plasma Physics AS CR, Prague, 2007, p. 42.
2. V.A. Zhovtyansky. Plasma-chemistry effects and some
fundamental problems of the gas discharge physics //
Ukr. J. Phys. 2008, v. 53, N 5, p. 490 – 496.
3. O.G. Didyk, V.A. Zhovtyansky, V.G. Nazarenko, and
V.A. Khomich. Plasma modification of the surface of
constructional materials // Ukr. J. Phys. 2008, v. 53,
N 5, p. 482-489.
4. Principles of Laser Plasmas / Ed. by G. Bekefi. New
York: “Wiley Interscience”, 1976.
5. A.A. Kudryavtsev, A.V. Morin, L.D. Tsendin. The role
of nonlocal ionization in short glow discharges // Tech.
Phys. 2008, v. 53, p. 1029-1040.
6. V.A. Zhovtyansky, Yu.I. Lelyukh. Mathematical
modelling of plasma in a glow discharge of spherical
geometry // Ukr. J. Phys. 2008, v. 53, N5, p. 497-503.
7. V.A. Zhovtyansky, Yu.I. Lelyukh. Numerical
simulation of stationary processes in glow discharge
plasma // Tech. Phys. Let. 2009, v. 35, p. 725-729.
8. A.S. Petrusev, S.T. Surzhikov, J.S. Shang. Two
dimensional model of glow discharge with account of
the vibration excitation of molecular nitrogen //
Teplofiz. Vys. Temp. 2006, v. 44, p. 814-822 (in
Russian).
9. Yu.P. Raizer. Physics of gas discharge. M.: “Nauka”,
1987 (in Russian).
10. Yu.S. Akishev, A.P. Napartovich, P.I. Peretyat`ko,
N.I. Trushkin. Near electrodes regions of glow
discharge and normal current density on the anode //
Tech. Phys. 1980, v. 18, p. 873-876 (in Russian).
11. V.А. Zhovtyansky, V.G. Nazarenko, V.O. Khomych,
et al. Efficiency of the nitriding process in glow
discharge plasma // This volume, p. 92-94.
Article received 27.10.10
ЭНЕРГЕТИЧЕСКИЕ ХАРАКТЕРИСТИКИ СФЕРИЧЕСКОГО ТЛЕЮЩЕГО РАЗРЯДА
В.А. Жовтянский, O.В. Aнисимова, В.А. Хомыч, Ю.И. Лелюх, В.Г. Назаренко, Я.В. Ткаченко
Конечной целью данной работы является оптимизация процессов модификации, основанных на
использовании тлеющего разряда (ТР), а именно азотирования поверхности конструкционных деталей. Эти
процессы изучены экспериментально и теоретически в плазме аномального сферического ТР в смеси N2-Ar. В
теоретической части работы рассмотрены уравнения баланса для плотности заряженных частиц и уравнение
Пуассона, дополненные уравнением теплопроводности. Последнее из них описывает влияние горячего катода
на процессы в разрядном объеме. Показано также, что корректный учет прианодного падения потенциала
играет ключевую роль для адекватного моделирования вольт-амперной характеристики сферического ТР.
ЕНЕРГЕТИЧНІ ХАРАКТЕРИСТИКИ СФЕРИЧНОГО ЖЕВРІЮЧОГО РОЗРЯДУ
В.А. Жовтянський, O.В. Aнісімова, В.О. Хомич, Ю.І. Лелюх, В.Г. Назаренко, Я.В. Ткаченко
Кінцевою метою цієї роботи є оптимізація процесів модифікації на основі використання жевріючого розряду
(ЖР), а саме азотування поверхні конструкційних деталей. Ці процеси вивчені експериментально і теоретично в
плазмі аномального сферичного ЖР у суміші N2-Ar. У теоретичній частині роботи розглянуто рівняння балансу
концентрації заряджених частинок і рівняння Пуассона, доповнені рівнянням теплопровідності. Останнє з них
описує вплив гарячого катода на процеси в розрядному об’ємі. Показано також, що коректне урахування
прианодного падіння потенціалу відіграє ключову роль для адекватного моделювання вольт-амперної
характеристики сферичного ЖР.
http://www.springerlink.com/content/?Author=A.+A.+Kudryavtsev
http://www.springerlink.com/content/?Author=A.+V.+Morin
http://www.springerlink.com/content/?Author=L.+D.+Tsendin
|