low temperature atmospheric pressure discharge plasma processing.pdf
TRANSCRIPT
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94
T. Oda et aL /Journal of Electrostatics 35 (1995) 93-101
a g a s m i x i n g p o i n t a f te r a c e r a m i c
r e a c t o r a n d g a s m i x i n g s p a c e w i t h
a lo w pr e ss u re l m e r c u r y l am p U V
s o u r c e ) i s n e w l y at t ac h e d . T y p i c a l
e x p e r i m e n t a l p r o c e d u r e i s a s
fo l lows:
a . D I R E C T : p l a s m a p r o c e s s i n g
a f t e r m i x i n g
M i x i n g P o i n t B )
o f c o n t a m i - n a t e d
a i r con tami -
n a n t i s e x p o s e d t o
p l a s m a )
b . I N D I R E C T : m i x i n g o f c o n -
t a m i n a t e d a i r a n d
p l a s m a p r o c e s s e d
c l e a n a i r a t m i x i n g
p o i n t A .
c . U V : p o w e r o n o f a U V
l a m p U V
ir radiat ion) .
The c e r amic r eac to r t e s t ed i s 10
m m i n i n n e r d i a m e t e r a n d 1 1 5 m m
l o n g d r i v e n b y a s t a n d a r d p o w e r
s u p p l y o f 5 K h z .
2 2 S a m p l e G a s e s
As con taminan t s , t yp ica l o rgan ic
m a t e r i a l s d e c o m p o s e d a r e
a
MixingTank Nz
b) total experimental setup
a) cross section o f a reactor
It , UV Lump
,~/Mixing Point A ~
~ e r a m i c Reactor
Fl0wl I Flow[
M et e~ t Mete~
L~
02 Air Tank
F i g . 1 S c h e m a t i c d i a g r a m o f S P C P e x p e r i m e n t a l s e tu p .
t r i ch lo roe thy lene : CICH=CCI2, mo lecu la r w e igh t : 131.39 , spec i f i c g r av i ty : l . 47 , vapor
p ressu re 60 mmHg a t 20 .5~C.
b . t e t r ach lo romethane : CCI4 vapo r p r essu re 89 .5 m m Hg a t 20C. f o rb idden f rom 1996)
c . 1 ,1 ,1 -t r ich lo roe thane : CH3CCI3 , vapo r p r essu re 100 m mH g a t 20C. f o rb idden f rom
1996)
d . 1 ,2 -d ich lo roe thane : CH2CICH2CI va por p r essu re 61 mm Hg a t 20C.
e . d ichlo rom ethan e: CH2C12, 349 m m H g at 20~C
f . ace tone : CH3COCH~, mo lecu la r we igh t :58 .08 , spec i f i c g r av i ty :0 .79 ,
vapor p r essu re :200 mmHg a t 22 .7C.
A g i v e n a m o u n t o f l i q u i d w a s s a m p l e d b y a m i c r o s y r in g e a n d w a s i n j e c t e d i n to a p r e s s u r iz e d
tank con ta in ing d ry compressed a i r was mixed a t up to 6 a tmospher i c p r essu re .
2 3 E x p e r i m e n t a l P r o c e d u r e s
T w o d i f fe r e n t s e r i e s o f e x p e r i m e n t s w e r e d o n e a s f o l l o w s .
2.3.1. Decomposition Mechanism
I n o r d e r t o h a v e a g o o d u n d e r s ta n d i n g o f t h e d e c o m p o s i t io n m e c h a n i s m , a n I N D I R E C T
me thod was n ew ly t e s t ed where the c l ean a ir was in t roduced in to the ce r am ic r eac to r. Af t e r
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1 . Oda e t al . IJourn al of Electrostatics 35 (1995) 93-101 95
plasma processing, the clean air was mixed with other VOC-contaminated air at mixing point
A. A small pen-type low pressure mercury lamp (Hamamatsu Photonics, L937-02, input
power: 5W), is inserted in a mixing gas chamber of contaminated gas and processed air shown
in Fig. 1.
Pure nitrogen or pure oxygen gas are also tested as carrier gas in place of clean dry air.
Trichloroethylene and acetone are tested as contaminants and a large difference of
decomposition performance was recognized. Those data were compared with other typical
data obtained by the standard process (DIRECT method).
2 . 3 .2 A N e w S a m p l e T e s t
Decomposition performance of four new halogenated organic compounds Co, c, d, and e
in 2.) was tested to know the applicability of SPCP for halogenated organic contaminant
decomposition. Especially, the two which will be forbidden in the near future.
3.RESULTS AND DISCUSSIONS
3 .1 D I R E C T a n d I N D I R E C T D e c o m p o s i t i o n T e s t s fo r T r i c h l o r o e t h y l e n e a n d A c e t o n e
3 . 1 . 1 T r i c h l o r o e t h y l e n e
3.1.1.1 DIRECT and INDIRECT Effects
The decomposition rates of trichlo- ~
roethylene in air versus discharge elect-tic ;~
power consumption at the reactor are g.
shown in Figs. 2 and 3. Fig. 2 was
recorded with a low flow rate; that is, a
Ca
flow rate of the 1,000 ppm
trichloroethylene in air at 400 ml/min and ~
Q)
the rate of pure air was 712 ml/min.
In the case of INDIRECT, the time
interval after the plasma processing (gas
flow time from the reactor to the mixing
point A) is 0.24 seconds and the final
concent-ration of the trichloroethylene is
360 ppm. At power consumption of only
1 W, the decomposition rate is already 40 ~ 100
%, but it does not increase at higher o
~.~
electric power. At a power of more than ~
10 or 15 W, it decreases drastically to zero ~
in the case of the INDIRECT method.
This tendency is similar to ozone C~
generation. High power causes high
temperature of the reactor wall and the
produced ozone might be decomposed at ~
high temperature. FAN in Fig. 2 means
fan cooling of the reactor with cooling
fins. Cooling by fan increases the
decomposition rate (Fig.3) occurs. In the
case of DIRECT, more than 90 %
100 f ~ - -
80 / --,,- :DIRECT
-i- :INDIRECT
60 -*-:INDIRECT+FAN
40 r,~'m''~:a- -~'*'--
20 ,
0 ' : '.
----' --
0 10 20 30
Power (W)
Fig.2 Decomposition rate of trichloroethylene
in air for the low flow rate.
80 ~ i =
40 : ,IY
.. .
CT
20 ..~-:INDIRECT
d
- t -. : I N D I R E C T F A N
0 10 20 30
Power (W)
Fig.3 Decomposition rate of vichloroethylene in
air for the high flow rate.
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96 T. Oda et aL /dournal o f Electrostatics 35 (1995) 93-101
o~ 100 F Interval Tim e ~ 100 Interval T im e ~.-:10cm(0.08sec)
~ 80 ~ f/ : ' ' ~ [ -*-:10cm(0'24sec) I ~ I ~
.... :70cm (l.68sec) c~ 80 w. :70cm(0.56sec)
6
~
6
8
20 ~ 20
~
0 10 20 30 ~ 0 10 20 30
Power (W) Power (W)
(a) low flow rate (b) high flow rate
Fig . 4 De com posit ion ra te of 1 ,000 ppm tr ichloroethylene in a ir .
deco mp osit ion occu rs a t only 5 W electr ic p owe r. On the other hand, in Fig .3 a t the high
flow rate (1 ,000 ppm tr ichloroethylene: 1 ,172 ml/min and air : 2 ,000 ml/min, f inal
concentra t ion: 370 ppm), the t ime interval is only 0 .08 seconds, and the decomposit ion ra te
gradua lly increases with e lectric p ow er for DIR EC T and an abrupt decrease o f the
decomposit ion ra te ( the maximum is not so high as that for DIRECT) at h igh e lectr ic power
is not so apparent. A slight FA N effect (a few %) is detected. In the case o f f luorocarbon
decomp os i t ion , no decompos i t ion w as de tec ted b y IND IRE CT o r U V i rrad ia tion . 3~
A t ime interval between the plasm a processing and m ixing with contam inated gas at point
A, m ay a f fec t the decomp os i t ion ra te tha t was sugges ted by Y amam oto . ~} Tw o jo in t p ipes o f
d i f fe ren t leng ths o f 0.1 m o r 0 .7 m be tween the ou t le t o f the p lasma reac to r and the mix- ing
point A of two gases was tested to check radical species and their li fe times. Results are
show n in Figs. 4 (a) and (b) where the t ime in parenthesis was the e lapsed t ime before m ixing.
In the shortest case , the decomposit ion ra te is the largest which is in good agreement with
the normal radical o r ozo ne li fe t ime effects . Ho we ver , the effect o f longer t ime is not
apparent and the results suggest that the ozone in the a ir created by SPCP may be the main
decomposit ion source.
100
3.1 .1 .2 Carr ier Gas Dependence
In place o f air, pure nitrog en or :=_ 80
oxygen gas was used as the carr ier gas .
E 60
Figures 5 and 6 show such results . In ~ 40
n i t rogen car rier , the DIR EC T method can
eas i ly decom pose t r i-ch lo roe thy lene up to ~ 20
99%, bu t no t r ich lo roe thy lene can be ~ 0 -
d e c o m p o s e d b y I N D I RE C T a t a ll. 0
Ni t rogen rad ica ls o r h igh energy e lec t rons
in t h e p l a s m a p r o d u c e d b y S P CP m a y
des troy trichloroethylene. The ir life time
may be ve ry smal l (o f mi l l i second o rder
- - - - : D I R E C T
- i v : D I R E C T + U V
- - : I N D I R E C I + F A N
- n - : I N D I R E C T + F A N + U V
- ~ . . . . . . . . . ~ . X X . . . . . . X
10 20 30
Power (W)
Fig . 5 Decom pos i t ion o f t r ich lo roe thy lene in N
for the low f low rate .
) and any ( less than a few percent which is the detect ion l imit) decomposit ion is not detected
b y t h e I N D I RE C T m e th o d.
3 .1 .1 .3 UV Irradiat ion Effects
As the mixing cel l contains a UV lamp, the UV irradiat ion effect is a lso shown in Figs.
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7 . Oda et al./Journal of Electrostatics 35 (1995) 93-101 97
5 and 6 with the mark UV. The
decomposition rate of trichloroethylene is
more than 95 for the low flow rate
(1,116 ml/min in total) or 65 for the
high flow rate (3,172 ml/min) with slight
(weak) UV light irradiation without
plasma discharge. The input power of
the low pressure mercury lump ( source as
calibration) is only 5 W and total UV
light intensity (2553A) may be less than 1
(30mW); that is, the UV decomposition
effect is much stronger than SPCP energy.
In the oxygen carrier, the UV effect is
greater and roughly 80 or 100
trichloroethytene are decomposed by the
very weak UV irradiation. Sometimes,
the UV irradiation effects might be
reduced (decomposit ion rate decreases) by
plasma discharge which is assumed to be
ozone and temperature effects. In a
nitrogen carrier, the UV effect is not so
large and constant; that is, the
decomposition rate is 20 for the low
flow rate and 5 for the
high flow rate.
3.1.2 Acetone
3.1.2.1 DIRECT and INDIRECT
The decomposition performance of
acetone in air by DIRECT or INDIRECT
SPCP is shown in Fig.7 where only the
DIRECT method can decompose 90
acetone at 30 W for the low flow rate
(1,000 ppm acetone in air:400 ml/min +
dry air:716ml/min). The maximum
decomposition rate by INDIRECT method
is less than 20 . For the high flow rate
(1,000 ppm acetone air: 1172ml/min,
air:2,000ml/min), the decomposition
rate is very low and the maximum rate is
only 60 at 30W by DIRECT shown in
Fig.8. For the same high flow, the de-
composition rate by INDIRECT is roughly
1oo ~ . . . ~
s
: - - -0 - - : D I R E C T
4o
- . J ,. : I N D I R E C T * F A N
20 - ~ :INDIRECT+FAN+UV
o
0
0 10 20 3o
Power (W)
Fig. 6 Decomposition of trichloroethylene in
oxygen for the high flow rate.
1 0 0
;~ 80
~
6o
~ 4o
N 20
o
~ o
o
o l i
I n ' - a - D I R E C T + U V
t . . b . I N D I R E C T + F A N
/ - ~ - I N D I R E C T F A N + U V
1 0 2 0 3 0
Power (W)
Fig. 7 Decomposition of acetone in air for the
low flow rate.
100
?-2 80
~ 6
~ 4o
~ 20
~ o
: D I R E C T
- t v : D I R E C T + U V
- - t ,- : I N D I R E C T + F A N
- ~ - : I N D I R E C T + F A N + U V ~ ~ ~ - - . - ~ l
. j r ' -
0 10 20 30
Power (W)
Fig. 8 Decomposition of acetone in air for the
high flow rate.
the same as that for the small flow rate, 20 . All decomposition rates of acetone are much
smaller than rates of trichloroethylene at the same conditions indicating hat the decomposition
of acetone is difficult. For the higher flow rate, the maximum decomposition rate is less than
70 by DIRECT. By gas-chromato-analysis, no apparent difference of processed products
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98 T. Oda et al./Yournal of Electrostatics 35 (1995) 93-101
were de tec ted .
100
3 . 1 .2 . 2 C a r r i e r G a s a n d U V E f f e c t s
: 80
W h e n t h e c a r r i e r g a s i s o x y g e n , t h e ~
d e c o m p o s i t i o n r a t e o f a c e t o n e i s v e r y ~ - 6 0
h i g h c o m p a r e d w i t h t h e a i r c a r r ie r w h i c h ~ 4 0
i s show n in F igs . 9 and 10 . Espe c ia l ly , :~
t h e m a x i m u m d e c o m p o s i t i o n r a te s o f ~ 2 0
a c e t o n e b y I N D I R E C T a r e v e r y h i g h , a s ~ 0
60 % fo r the low f low ra te o r 40 % fo r ~ /
t h e h i g h f l o w r a t e c o m p a r e d w i t h t h e
c a s e i n a i r o r n i tr o g e n . O z o n e o r O
s h o u l d b e v e r y e f f e c t iv e i n d e c o m p o s i n g F i g . 9
a c e t o n e . T h e U V i r ra d i a t i o n e f f ec t i s
v e r y s m a l l , s i m i l a r t o t h e a i r c a r r i e r
a l t h o u g h U V i s v e r y e f f e c t i v e i n
d e c o m p o s i n g t r i c h l o ro e t h y l e n e . T h e ~ 1 00
t im e in te rva l e f f ec t i s sho wn in F ig . 11 . o
Fo r the h igh gas f low ra te , the :~ 80
d e c o m p o s i t i o n r a te f o r a s h o r t p a t h a n d ~ - 6 0
l o w e l e c t r i c a l p o w e r i s v e r y h i g h a t 6 0
40
% , b u t i t r e d u c e s t o t h e s a m e l e v e l f o r a
l o n g g a s p i p e w h e n t h e i n p u t e l e c t r ic 8 2 0
p o w e r i s l a rg e . F o r t h e l o w f l o w r a t e ~ 0
o f ca r r i e r gas , 10 o r 20 % h ighe r ~
d e c o m p o s i t i o n r a te ( c o n s t a n t to b e 6 0 % )
o c u r s i n m o s t p o w e r c o n s u m p t i o n r a n g e.
W h e n t h e c a r r i e r g a s i s n i t r o g e n , th e
d e c o m p o s i t i o n r a t e o f a c e t o n e is l o w . F i g .
C o m p a r e d w i t h t h e a i r c a r r i e r , t h e
d e c o m p o s i t i o n r a te i s 5 o r 1 0 % s m a l l e r
b y D I R E C T s h o w n i n F i g . 1 2 f o r t h e l o w ~ 1 00
f low ra te . Th e r a te i s l e s s than 5 %
( w i t h i n e r r o r l e v e l ) w h i c h i s m u c h :~ 8 0
sm al le r tha n tha t fo r the a i r ca r r i e r by ~ - 60
I N D I R E C T . O x i d a t i o n o f a c e t o n e $
s h o u l d b e t h e e s s e n t i a l f o r :~ 4 0
dec om pos i t io n . ~6 20
)
0
e , :
F o u r N e w H a l o ge n a te d V O C s
F i g u r e 1 3 s h o w s o n e e x a m p l e o f
t e t r a c h l o r o m e t h a n e d e c o m p o s i t i o n
p e r f o r m a n c e v e r s u s e l e c t r i c p o w e r
c o n s u m p t i o n w h e r e t h e r e s i d e n c e t im e i s
c a l c u l a t e d a s t h e r e a c t o r v o l u m e d i v i d e d
[
+ : D I R E C T
~ - i - : D I R E C T + U V
- k . : I N D I R E C T + F A N
- ~ - : IN D I R E C T + U V + F
A N
0 10 20 30
Power (W )
A c e t o n e d e c o m p o s i t i o n i n o x y g e n f o r th e
low f low ra te .
Fig. 11
. a / 9 < , - - x
- - Jr - : I I ~ C T + F M q
- - : l l ~ l l ~ f f r + F . ~ q + l J V
0 10 20 30
Power (W )
1 0 A c e t o n d e c o m p o s i t io n i n o x y g e n f o r th e
h igh f low ra te .
Interval Time
--*- : l)cm(0.08sec)
m. :70cm(0.56sec)
_ r . - -
0 10 20 30
Power (W )
A c e t o n e d e c o m p o s i t i o n i n o x y g e n f o r
d i f f e r e n t m i x i n g t i m e i n t e r v a l .
b y t h e g a s f l o w r a te . A v e r y h i g h d e c o m p o s i t i o n r a t e o f m o r e t h a n 9 5 % i s r e a l i z e d a t
e l e c t r ic a l p o w e r c o n s u m p t i o n o f 3 0 - 4 0 W f o r 1 , 00 0 p p m t e t r a c h l o r o m e t h a n e i n a i r. W h e n
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T . O d a e t a l . I J o u r n a l o f E l e c tr o s t a ti c s 3 5 ( 1 9 9 5 ) 9 3 - 1 0 1 99
t h e c o n c e n t r a t i o n o f c o n t a m i n a n t is 1 0 0
p p m , t h e h i g h e r d e c o m p o s i t i o n r a t e
was r eco rded .
T h e n e c e s s a r y e l e c t r i c p o w e r
c o n s u m p t i o n t o d e c o m p o s e o n e
m o l e o f c o n t a m i n a n t s i s sh o w n i n
F i g . 1 4 w h e r e o r i g i n a l c o n t a m i - n a n t
c o n c e n t r a t i o n fo r e a c h o f t e t r a e t h a n e ,
t r i c h l o r o e t h a n e , d i - c h l o r o e t h a n e o r
d i c h l o r o - m e t h a n e , i s 1 ,0 0 0 p p m . I n
e v e r y c a se , t h e m i n i m u m p o w e r i s 2 -
3 X 1 7 J / m o l e o r d e r. H o w e v e r , t h e
d e c o m p o s e d p r o d u c t a n a l y s i s6) sugges ts
t h a t t h e r e a r e m a n y i n t e r m e d i a t e b y -
p r o d u c t s i n c l u d - i n g p o i s o n o u s m a t e r i a l s
w h e n t h e d e c o m p o s i t i o n r a t e i s l e s s
t h a n 6 0 o r 70 % . I n g e n e r a l , w h e n th e
f l o w r a t e i s l a r g e ( s m a l l r e s i d e n c e
t i m e ) , t h e n e c e s s a r y p o w e r t o
d e c o m p o s e o n e m o l e o f V O C i s s m a l l.
A t t h e d e c o m p o s i t io n
r a t e o f 8 0 % , d i c h l o r o e t h a n e i s t h e
e a s ie s t d e c o m p o s e d a m o n g f o u r V O C s
a n d t r i c h l o r o e t h a n e i s t h e m o s t s t a b l e
( t h e m o s t d i f f i c u l t m a t e r i a l t o
d e c o m p o s e ) . H o w e v e r , t h e d i f f e r e n c e
i s o n l y f a c to r o f 2 o r 3 . A t t h e h i g h
d e c o m p o s i t i o n r a t e , N z O i n c r e a s e s i n
the p roduc t gas es .
4 . C O N C L U S I O N S
100
-
o
:~ 80
60
E
o
40
20
0
0
, f i / - I - : D IR E C T + U V
J --~ ,- : INDIR ECT
? - ~ - :INDIE , _ . , . . _ C I + U V. . . . .
10 20 30
P o w e r ( W )
F i g . 1 2 A c e t o n e d e c o m p o s i t i o n i n n i t r o g e n fo r t h e
l o w f l o w r a t e .
100
0
:.-2_- 80
6 0
E
o
40
20
S P C P d e c o m p o s i t i o n p e r f o r m a n c e ~ 1 00
o f 1 ,0 0 0 p p m v o l a t i l e o r g a n i c . ~ 8 0
c o m p o u n d s ) V O C s ) i n a t m o s p h e r ic 8
-~
p r e s s u r e a i r , o x y g e n o r n i t r o g e n w a s E 6 0
t e st e d . O x y g e n i s f o u n d t o b e t h e 8
40
mo s t des t ruc t ive ca r r i e r gas o f d i lu te c3
V O C s . V O C s i n p u r e n i t r o g e n c a r ri e r , ~ 2 0
e s p e c i a l l y t r i c h l o r o e t h y l e n e , c a n b e
d e c o m p o s e d b y S P C P w h e n t h e
c o n t a m i n a t e d g a s i s d i r e c t l y p r o c e s s e d .
H o w e v e r , t h e V O C s d e c o m p o s i t i o n
p e r fo r m a n c e b y t he I N D I R E C T m e t k o d
( p l a s m a p r o c e s s e d n i t r o g e n g a s i s F i g . 1 3
m i x e d w i t h c o n t a m i n a t e d g a s ) , i s v e r y
p o o r i n d i c a t i n g th e l i f e - t im e o f t h e
at g
/ m'
,. .,-
i , Residence Time
; .. --*- :0.3 9s
; - - :0 .76s
.
--- : 1.65s
10 20 30 40
P o w e r ( W )
(a) 100 ppm
~ A _ , _ . A - . . . . . . . . . A ' . - i . . . . . .
m - . l , - -
, / , . .
# A . -
/ J ~ T i m e
t ' J - -- : 0 .3 9 s
i~ J .... :0.76s
~ / - - : 1 .65s
0 10 20 30 40
P o w e r ( W )
(b) 1 ,000 ppm
D e c o m p o s i t i o n o f t e t ra c h l o ro m e t h a n e f o r
1 0 0 a n d 1 , 0 0 0 p p m i n a i r b y S P C P .
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1O0 T O da et al /Journal f Electrostatics 35 (1995) 93-101
n i t ro g e n r a d i c a l o r h i g h e n e r g y e l e c t ro n p r o d u c e d b y t h e p l a s m a w h i c h m a y d e c o m p o s e V O C s
i s a s s u m e d t o b e v e r y sm a l l . O z o n e o r O r a d i c a l s e e m s t o b e v e r y e f fe c t iv e in d e c o m p o s i n g
V O C s a s o p p o s e d t o t h e f l u o r o c a r b o n d e c o m p o s i t i o n t e s t ( w h e r e n o d e c o m p o s i t i o n w a s f o u n d
b y t h e I N D I R E C T m e t h o d ) . F o r a l l 1 ,0 00 p p m c h lo r o - o r g a n ic c o m p o u n d s i n a i r
( t e tr ach lo romethane , t r ich lo roe thane , d i ch lo roe thane o r d i ch lo romethane) , t he necessa ry e l ec t r ic
p o w e r to d e c o m p o s e 1 m o l e o f V O C s i s f o u n d t o b e 2 - 3 X 107 J / m o l e w h e n t h e
d e c o m p o s i t i o n r a te i s 6 0 o r 7 0 % .
Tr i ch lo roe thy lene was found to de com pose w i th a s l igh t ir r ad ia t ion o f UV l igh t , bu t t he
m e c h a n i s m i s n o t y e t u n d e r s to o d .
M uch fu r the r r esea r ch shou ld be done fo r f u r the r p r ac t i ca l app l i ca t ion o f SPC P gas con t ro l .
R E F E R E N E S
1 ) S . M a s u d a N o n - E q u i l i b r i u m P l a s m a C h e m i c a l P r o c e s s P P C P a n d S P C P f o r C o n t r o l o f
NO x, Sox and Other Gaseo us Po l lu t an t s, P roc .4 th In t .Conf .ESP pp .615-623(1990)
2 ) S . M a s u d a
e t a l ,
A C e r a m i c - B i a s e d O z o n i z e r U s i n g H i g h F r e q u e n c y S u r f ac e D i s c h a rg e ,
IEEE Trans . IA-24 , pp .223-231(1988)
3 ) T . O d a et a l , A t m o s p h e r i c P r e s s u r e D i s c h a rg e P l a s m a P r o c e s s i n g f o r G a s e o u s A i r
Con tam inan t s , IEEE Trans . IA-29 , pp .787-792(1993)
4 ) T . O d a e t a l , D e c o m p o s i t io n o f G a s e o u s O r g a n i c C o n t a m i n a n t s b y S u r f ac e D i s c h a r g e
I n d u c e d P l a s m a C h e m i c a l P r o c e s s i n g - S P C P , C o n f . R e c . o f I E E E / I A S 1 99 2 A n n .
M ee t ing pp . 1570-1574(1992) .
5 ) T . Y a m a m o t o : p r i v a t e c o m m u n i c a t i o n .
6 ) t o be p r esen ted in fu tu r e Confe r ence .
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Rate o f Decom posi t ion (%) Ra te of Decom posi t ion (%)
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