Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin (IV) oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-LaRC on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) achievement of 98% to 100% conversion of a stoichiometric mixture of CO and O2 to CO2 for 318 hours (greater than 1 x 10 to the 6th power seconds), continuous, at a catalyst temperature of 60 C, and (2) development of a technique verified in a 30-hour test, to prevent isotopic scrambling when CO-18 and O-18(2) are reacted in the presence of a common-isotope Pt/Sn O-16(2) catalyst

Batten, Carmen E.

Brown, Kenneth G.

Burney, Lewis G.

Hess, Robert V.

Hoyt, Ronald F.

Miller, Irvin M.

Paulin, Patricia A.

Schryer, David R.

Sidney, Barry D.

Wood, George M.

English

NASA Technical Reports Server

N 8 1 - 2 0 5 3 2  
NASA-LaRC RESEARCH ON 
CATALYSTS FOR LONG-LIFE CLOSED-CYCLE C 0 2  LASERS 
David R .  Schryer ,  Barry D.  Sidney, I rv in  M. M i l l e r ,  Robert V .  Hess, 
George M. Wood, Carmen E .  Bat ten,  Lewis  G.  Burney, Ronald F. Hoyt, 
and P a t r i c i a  A. Paul in  
Langley Research Center 
Hampton, Vi rg in ia  
Kenneth G. Brown and Jacquel ine  Schryer 
Old Dominion Universi ty  
Norfolk,  Vi rg in ia  
B i l l y  T. Upchurch 
Chemicon, Inc  . 
V i r g i n i a  Beach, V i r g i n i a  
SUMMARY 
Long-l i fe ,  closed-cycle ope ra t ion  of pulsed C 0 2  l a s e r s  r equ i r e s  c a t a l y t i c  CO - 
P l a t i n u m  metal on a t i n  (IV) oxide s u b s t r a t e  
0 2  recombination both t o  remove 0 2 ,  which is formed by discharge-induced C 0 2  
decomposition, and t o  regenera te  C 0 2 .  
(Pt/Sn02) has been found t o  be an e f f e c t i v e  c a t a l y s t  for  such recombination in  the  
des i r ed  temperature range of 25°C t o  100°C. This paper p re sen t s  a d e s c r i p t i o n  of 
ongoing research  a t  NASA-LaRC on Pt/SnOp catalyzed CO - 0 2  recombination. 
a r e  s t u d i e s  with ra re- i so tope  gases  s ince  rare- isotope C 0 2  i s  d e s i r a b l e  as a l a s e r  
gas  f o r  enhanced atmospheric t ransmission.  Resul ts  presented include (1)  achieve- 
ment of 98% - 100% conversion of a s to ich iometr ic  mixture of CO and 02 t o  C 0 2  f o r  
318 hours (>  1 x 10 seconds) ,  cont inuous,  at a c a t a l y s t  temperature of 60°C and (2)  
development of a technique v e r i f i e d  i n  a 30-hour t e s t ,  t o  prevent i s o t o p i c  
scrambling when C1*0 and "02 a r e  reacted in  t h e  presence of a common-isotope 
pt /sn1602 c a t a l y s t .  
Included 
6 
INTRODUCTION 
Pulsed C 0 2  l a s e r s  have seve ra l  p o t e n t i a l  remote sensing a p p l i c a t i o n s ,  both 
m i l i t a r y  and non-mi l i t a ry ,  which r equ i r e  long-l i fe  opera t ion  with high conversion- 
e f f i c i e n c y  and good power-s tab i l i ty .  However, two problems a r e  assoc ia ted  with 
such app l i ca t ions .  
One problem i s  t h a t  t h e  e l e c t r i c a l  discharge normally used t o  e x c i t e  pulsed 
C 0 2  l a s e r s  i n e v i t a b l y  decomposes some of the  C 0 2 :  
Elec . 
Disch. 
c02 - co + 1/2  0 2  
113 
https://ntrs.nasa.gov/search.jsp?R=19870011099 2020-03-20T11:14:48+00:00Z
P 
This decomposition i s  harmful t o  long- l i f e  l a s e r  ope ra t ion  both because of t he  l o s s  
of C o p  and because of the bui ldup of 0 2 .  
ing gradual  l o s s  of l a s e r  power. 
t i o n s  (0.1% - 1.0%) of 0 2  molecules can cause rapid power l o s s  and even complete 
l a s e r  f a i l u r e .  
The l o s s  of C 0 2  r e s u l t s  in  a correspond- 
The bui ldup  of even r e l a t i v e l y  small  concentra-  
The second problem has  nothing t o  do wi th  C o p  l a s e r s  themselves;  i t  i s  caused 
by t h e  f a c t  tha t  t he  atmosphere con ta ins  a s i g n i f i c a n t  concen t r a t ion ,  about 300 
ppm, of common-isotope Cop ( l2Cl602) .  I f  common-isotope Cop  i s  used i n  a C 0 2  l a s e r  
intended f o r  atmospheric t ransmiss ion ,  t he  emission f requencies  a v a i l a b l e  t o  t h e  
l a s e r  w i l l  correspond t o  t h e  absorp t ion  f requencies  of the  atmospheric C 0 2  and poor 
t ransmiss ion  w i l l  r e s u l t .  
The so lu t ions  t o  these  two problems are s u p e r f i c i a l l y  q u i t e  s imple:  ( 1 )  
cont inuous ly  remove O2 as i t  i s  formed and r ep len i sh  C 0 2  and (2 )  use some form of 
ra re- i so tope  C02 (such as 12 C 18 02, 13C1602, or 13C'802) i n  a l l  l a s e r s  intended f o r  
a p p l i c a t i o n s  involving atmospheric t ransmiss ion  so t h a t  the  emisson f r e  uenc ies  of 
such lasers w i l l  d i f f e r  from the  absorp t ion  f requencies  of atmospheric C 0 2 .  
Actual implementation of these  two s o l u t i o n s ,  however, i s  f a r  from s i m p l e .  
1 2  16 
Removal of O2 and replenishment of C 0 2  can be achieved i n  c e r t a i n  a p p l i c a t i o n s  
simply by opera t ing  the  laser open-cycle with a cont inuous flow-through of f r e s h  
l a s e r  gas and the consequent removal of d i s s o c i a t i o n  products .  However f o r  
space-based app l i ca t ions  or o the r  a p p l i c a t i o n s  involv ing  weight and/or volume 
c o n s t r a i n t s ,  the amount of gas  requi red  fo r  open-cycle ope ra t ion  would be 
unacceptable  and, i n s t e a d ,  c losed-cycle  l a s e r  ope ra t ion  with r ecyc l ing  of the  l a s e r  
gases  would be imperat ive.  Closed-cycle ope ra t ion  would a l s o  be h igh ly  d e s i r a b l e  
f o r  any app l i ca t ions  where ra re- i so tope  C02 i s  used f o r  enhanced atmospheric 
t ransmiss ion  because of the  expense of t h e  l a r g e  volumes of ra re- i so tope  gas which 
would be required fo r  flow-through ope ra t ion .  
Closed-cycle C02 laser ope ra t ion  with removal of  0 2  and r egene ra t ion  of C 0 2  
can be  achieved, in  p r i n c i p l e ,  s i m p l y  by accomplishing CO-O2 recombination. 
co + 1 / 2  0 2  - c02 
However, t h i s  recombination i s  n e g l i g i b l y  slow a t  s t eady- s t a t e  temperatures  (about 
50°C t o  100°C) achieved by the  gas  mixture  i n  a t y p i c a l  Cop laser .  Thus, a l though 
some recombination can occur i n  the  region of t he  e l e c t r i c  d i scharge  where 
e f f e c t i v e  temperatures a r e  q u i t e  h igh ,  no s i g n i f i c a n t  recombination can occur i n  
t h e  main body of t he  l a s e r  gas  unless  a c a t a l y s t  is  used. Several  materials have 
been found t o  ca t a lyze  CO-OP recombination under va r ious  cond i t ions .  
c a t a l y s t s  u t i l i z e  noble metals ( e s p e c i a l l y  P t  and/or Pd) ,  metal  ox ides ,  or both.  
C a t a l y s t s  cons i s t ing  of Pt  o r  Pd on a t i n  (IV) oxide s u b s t r a t e  (Pt/SnOp, Pd/SnOp) 
have been shown t o  be much more e f f i c i e n t  than P t ,  Pd, or Sn02 a lone  at  moderate 
temperatures  (Refs. 1 and 2 ) .  
Most such 
A t  t he  NASA Langley Research Center (NASA-LaRC) w e  have inves t iga t ed  s e v e r a l  
c a t a l y s t s  f o r  p o t e n t i a l  use with long- l i f e ,  c losed-cycle  C 0 2  l a s e r s  inc luding  
Pt /Sn02,  P t /S i02 ,  unsupported P t ,  Pd/C, and Cu/Cu20/Cu0 (Refs.  2 and 3). 
promising of these c a t a l y s t s  has been found t o  be Pt/Sn02 and so a d e t a i l e d  
i n v e s t i g a t i o n  of t h i s  c a t a l y s t  has  been undertaken and i s  c u r r e n t l y  i n  progress .  
S tud ie s  of t h i s  and o the r  c a t a l y s t s  a r e  being c a r r i e d  out  i n  seve ra l  l abo ra to ry  
r e a c t o r s  as well as i n  a pulsed Cog laser .  
The most 
114 
TEST FACILITIES 
Laboratory Reactors  
Laboratory r e a c t o r s  a r e  used f o r  c a t a l y s t  s tudy under c o n t r o l l e d  cond i t ions .  
Three l a b o r a t o r y  r e a c t o r s  are p resen t ly  ope ra t iona l ,  a l l  of which are flow-through 
r e a c t o r s .  In t h e s e  r e a c t o r s  a tes t -gas  mixture flows through a r e a c t o r  tube 
con ta in ing  a c a t a l y s t  sample which is s i t u a t e d  i n  a temperature-control led oven. 
The gas which ex i t s  t h e  r e a c t o r  tube  is q u a n t i t a t i v e l y  analyzed with e i t h e r  a gas 
chromatograph (GC) or mass spectrometer  (MS) and from t h i s  a n a l y s i s  t h e  amount o f  
CO and 0 2  converted t o  C 0 2  by the  c a t a l y s t  sample i s  determined. The t e s t -gas  
mixtures  used are purchased premixed i n  a high-puri ty  He c a r r i e r ,  t y p i c a l l y  1 .OOZ 
CO and 0.50% O2 p lus  2.00% N e  ( a s  an i n t e r n a l  c a l i b r a t i o n  s tandard  for gas 
a n a l y s i s ) .  
Two of t h e  flow-through r e a c t o r s  are used with common-isotope gases  and use  
G C ' s  f o r  gas  a n a l y s i s .  These G C ' s  a r e  f u l l y  automated so t h a t  tests with 
comon-isotope gases  can be conducted i n  the flow-through r e a c t o r s  around-the-clock 
without  an ope ra to r  p re sen t .  The t h i r d  flow-through r e a c t o r  i s  used with 
r a re - i so tope  gases  and uses  an MS f o r  gas  analysis.  
S tud ie s  performed i n  t h e  flow-through r e a c t o r s  a r e  (1) parametr ic  s t u d i e s  t o  
determine t h e  e f f e c t  of such parameters as c a t a l y s t  mass, temperature ,  r e a c t o r  
res idence- t ime,  e t c . ,  on t h e  performance of a given c a t a l y s t  material, ( 2 )  
comparison of d i f f e r e n t  c a t a l y s t  compositions (such as Pt/Sn02, Pd/Sn02, and P t  + 
Pd/Sn02) and concen t r a t ions  t o  determine the optimum c a t a l y s t  formula t ion ,  (3 )  
long-term performance tests (us ing  the  automated-GC r e a c t o r s )  t o  determine how a 
c a t a l y s t  performs w i t h  long-term exposure t o  t h e  tes t  gases ,  and ( 4 )  i s o t o p i c  
s t u d i e s  (us ing  t h e  MS r e a c t o r )  t o  determine t h e  i n t e r a c t i o n  of a g iven  c a t a l y s t  
wi th  r a re - i so tope  gases.  
A r e c i r c u l a t i n g  r e a c t o r  i s  p resen t ly  being assembled and should be o p e r a t i o n a l  
s h o r t l y .  I n  t h i s  r e a c t o r  a gas mixture  w i l l  be cont inuous ly  r e c i r c u l a t e d  through a 
tempera ture-cont ro l led  r e a c t o r  tube  containing a sample of c a t a l y s t ,  and t h e  
conversion of CO and 02 t o  CO2 monitored as  a func t ion  of t i m e .  
be performed wi th  a GC. This r e a c t o r  w i l l  be used t o  determine t h e  ra te  of CO-OP 
recombination using var ious  c a t a l y s t  m a t e r i a l s  and a l s o  t o  s tudy the  mechanism of 
c a t a l y s i s .  Knowledge of t hese  f a c t o r s  i s  important  fo r  op t imiza t ion  of c a t a l y s t  
performance . 
Gas a n a l y s i s  w i l l  
Also t o  be assembled s h o r t l y  w i l l  be a system t o  q u a n t i t a t i v e l y  measure 
chemisorpt ion of  gases  on a c a t a l y s t  sur face  when some of t he  chemisorbed s p e c i e s  
undergo deso rp t ion  as a product  gas. 
Laser Reactor 
A Lumonics model TEA-820 pulsed C 0 2  laser ( . 7 Jou le /pu l se ,  1-20 pulses/second)  
i s  a v a i l a b l e  f o r  c a t a l y s t  t e s t i n g  under ac tua l  laser ope ra t ing  cond i t ions .  The 
laser i s  opera ted  closed-cycle  wi th  an ex te rna l  c a t a l y s t  bed ( i n  a 
temperature-control led oven) and t h e  results are compared with t h e  open-cycle 
performance of t h e  l a s e r  a t  t h e  same flow r a t e .  It is  intended t h a t  u l t i m a t e l y  t h e  
115 
l a s e r  w i l l  be operated with no hea t ing  of t he  c a t a l y s t  o the r  than by the  l a s e r  
gas .  
w i l l  be used when the laser i s  operated with ra re- i so tope  C o p .  
Gas ana lys i s  i s  performed with a GC i n  cu r ren t  common-isotope tes ts .  An MS 
RESULTS AND ON-GOING RESEARCH 
This  sec t ion  presents  a summary of r e s u l t s  obtained t o  da t e  using t h e  
c u r r e n t l y  opera t iona l  r e a c t o r s  descr ibed i n  t h e  previous s e c t i o n  as w e l l  as a 
synopsis  of work c u r r e n t l y  i n  progress  or planned. 
Labor a t  ory Reactor S tud ie s  
Common-Isotope Gases 
(1)  Conversion of 1% CO and .5% 02 t o  C o p  a t  an e f f i c i e n c y  of 98%-100% has been 
achieved i n  a labora tory  r e a c t o r  with 1.5 grams of 2% Pt/Sn02 a t  60°C and 10 s t d .  
mL/minute flow r a t e .  This e f f i c i e n c y  was maintained f o r  318 hours (> l o 6  seconds 
o r  13 days) .  
of c a t a l y s t  e f f i c i e n c y .  Tes ts  a t  lower temperatures  a r e  i n  progress .  Scheduled 
a r e  laser tes ts  t o  v e r i f y  t h i s  r e s u l t  i n  ac tua l  laser opera t ion ,  and 
labora tory- reac tor  tests involving non-stoichiometric gas mixtures  (both CO and 0 2  
r i c h ) .  
The tes t  was terminated because of a GC f a i l u r e  not  because of a l o s s  
(2 )  A t  a given c a t a l y s t  temperature,  c a t a l y s t  surface-area-to-mass r a t i o ,  and 
gas  flow r a t e , t h e  conversion of CO and 0 2  t o  C 0 2  over a Pt/SnOg c a t a l y s t  appears t o  
be an approximately l i n e a r  func t ion  of c a t a l y s t  m a s s  u n t i l  100% e f f i c i e n c y  is  
achieved. (See F igure  1 )  
( 3 )  The conversion e f f i c i e n c y  p e r  u n i t  mass of Pt/Sn02 has been approximately 
doubled ( o r  the c a t a l y s t  mass halved) by p r e t r e a t i n g  the  c a t a l y s t  with flowing 1% 
CO i n  He f o r  one hour a t  225°C r e l a t i v e  t o  pretreatment  f o r  the  s a m e  t i m e  and 
temperature with He alone.  
been more than doubled ( o r  t he  mass more than  halved) by p r e t r e a t i n g  the  c a t a l y s t  
with flowing He a t  225°C f o r  twenty hours r e l a t i v e  t o  pretreatment  with He at  the 
same temperature f o r  only one hour .  Tes ts  a r e  scheduled t o  determine t h e  optimum 
pretreatment  time and temperature t o  achieve maximum c a t a l y s t  e f f i c i e n c y .  Also t o  
be inves t iga t ed  i s  whether combination of extended He pretreatment  with CO 
pre t rea tment  w i l l  f u r the r  increase  c a t a l y s t  e f f i c i e n c y .  
The conversion e f f i c i e n c y  per u n i t  mass of Pt /Sn02 has 
( 4 )  The c a t a l y t i c  e f f i c i e n c y  of 2% Pt/Sn02 a t  100°C has been found t o  be near ly  
twice t h a t  of 1% Pt/Sn02 of equal  sample mass and su r face  a rea .  
loading of noble metal t o  Sn02 w i l l  be determined i n  f u t u r e  t e s t s .  
The optimum 
( 5 )  I n i t i a l  tests comparing 2% Pt/SnOp with 2% Pd/Sn02 and 1% P t  + 1% Pd/Sn02 
have been performed at .75"C.  
achieved with 2% Pt/Sn02 than w a s  achieved with 2% Pd/Sn02. 
conversion e f f i c i e n c y  was achieved with 1% Pt  + 1% Pd/Sn02 than w a s  achieved wi th  
2% Pt/Sn02. 
comparison of Pt/SnOp with o the r  c a t a l y s t s  and comparison of Pt/SnOp prepared a t  
t h i s  labora tory  and by Prof .  Gar Hoflund a t  t he  Un ive r s i ty  of F l o r i d a  with the  
commercially ava i l ab le  products  used i n  our s t u d i e s  t o  d a t e .  
More than twice the  conversion e f f i c i e n c y  was 
A s l i g h t l y  higher  
Comparison of var ious  c a t a l y s t  m a t e r i a l s  w i l l  cont inue inc luding  both 
116 
Rare-Isotope Gases 
(1 )  Exposure of common-isotope P t / S n l 6 0 2  t o  1% C l 8 0  and .5% 1802 a t  100°C 
16 18 y i e l d s  about 85%-90% C l 8 O 2  and 10%-15% of t h e  mixed-isotope spec ie s ,  C 0 0. This  
r e s u l t  tends t o  i m p l y  t h a t  two competing r e a c t i o n s  occur when CO and O2 are 
oxid ized  wi th  a Pt/SnO c a t a l  s t .  
involve r e a c t i o n  of C 0 and "02 on the c a t a l y s t  su r f ace  but no r eac t ion  of these  
s e c i e s  with the  su r face .  
C 
s u r f a c e  by 1802. 
occurrence of two competing r eac t ions  and t o  determine t h e i r  mechanisms in  d e t a i l .  
The r eac t ion  which y i e l d s  C180p appears t o  
18 
The r e a c t i o n  which y i e l d s  C160180 i m p l i e s  ox ida t ion  of 
0 by l 6 O  atoms i n  the  su r face  l a t t i c e  and then,  presumably, reoxida t ion  of t he  !8 
Fur ther  i s o t o p i c  s tud ies  w i l l  be performed t o  v e r i f y  t h e  
( 2 )  A technique has  been developed to prevent formation of the  mixed i so tope  
spec ies  C160180 when C l 8 0  and 1802 a re  recombined using a P t /SnlC02 c a t a l y s t  ( a s  i n  
t h e  preceding i tem).  The technique involves  reducing t h e  c a t a l y s t  s u r f a c e  w i t h  a 
measured q u a n t i t y  of Hp t o  remove a l l  r eac t ive  l60 atoms and then r eox id iz ing  t h e  
su r face  with 1802. 
c a t a l y s t  su r f ace  with '*O atoms so  t h a t  any exchange of oxygen atoms between t h e  
gaseous spec ies  and the c a t a l y s t  sur face  does not r e s u l t  i n  i s o t o p i c  scrambling of 
t h e  gases .  This  technique ( f o r  which a Pa ten t  Applicat ion has been f i l e d )  has been 
va l ida t ed  in  a 30-hour t e s t .  
The ne t  e f f e c t  is to r ep lace  a l l  r e a c t i v e  l60 atoms on the 
Laser S tudies  
The Lumonics Model TEA-820 laser has been operated closed-cycle with a 
c a t a l y s t  bed of 150 g of 2% Pt/Sn02 a t  100°C. 
s teady-s ta te  open-cycle power f o r  28 hours (1 x 10 pulses  a t  10 pulses/second) .  
(See F igure  2)  
f o r  1987. 
The l a s e r  achieved 96.5% ( 2  2.5%) of 
6 
A tes t  of lo7 pulses  a t  a catalyst  temperature <lOO"C i s  planned 
CONCLUDING REMARKS 
Pt/SnOp has been shown t o  be an e f f e c t i v e  CO - O2 recombination c a t a l y s t  a t  
I ts  s teady-s ta te  t e m p e r a t u r e s  achieved by the gas  mixture  i n  pulsed CO2 l a s e r s .  
c a t a l y t i c  e f f i c i e n c y  can be enhanced by s u i t a b l e  pretreatment  techniques and 
optimum metal loading.  Even though the  s u b s t r a t e  Sn02 con ta ins  predominantly 
common-isotope oxygen i t  appears t h a t  reduct ion of the  c a t a l y s t  su r f ace  with H2 
and r eox ida t ion  wi th  i802 renders  t he  c a t a l y s t  compatible with ra re- i so tope  C l 8 O 2  
and i ts  ra re- i so tope  d i s s o c i a t i o n  products. A sys temat ic  r e sea rch  p r o j e c t ,  
descr ibed  i n  t h i s  r e p o r t ,  is  i n  progress  a t  NASA-LaRC t o  f u r t h e r  eva lua te  and 
enhance t h e  c a t a l y t i c  p rope r t i e s  of Pt/SnOp and o ther  c a t a l y s t s  for use i n  
long- l i f e ,  closed-cycle C 0 2  lasers. 
11 7 
REFERENCES 
1. Bond, Geoffrey C . ;  Moloy, Leslie R . ;  and F u l l e r ,  Martin J . :  Oxidat ion of  
Carbon Monoxide over Palladium-Tin (VI) Oxide C a t a l y s t :  An Example of 
S p i l l o v e r  Ca ta lys i s .  Journa l  of t h e  Chem. SOC. Chem Comm., 1975, 
pp. 796-797. 
2 .  Brown, K.  G . ;  Sidney, B. D . ;  Schryer ,  D.  R . ;  Upchurch, B. T . ;  M i l l e r ,  I. M . ;  
Wood, G.  M.; Hess, R. V . ;  Ba t ten ,  C . ;  Burney, L.  G . ;  Pau l in ,  P. A . ;  Hoyt, R . ;  
and Schryer,  J . :  C a t a l y t i c  Recombination of D i s soc ia t ion  Products  with 
Pt/Sn02 for Rare and Common Iso tope  Long-Life, Closed-Cycle C 0 2  Lasers. 
Laser Radar Technology and Appl ica t ions ,  Proceedings of SPIE, Vol. 663, 1986, 
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3 .  Rogowski, R.  S . ;  Miller,  I. M . ;  Wood, G . ;  Schryer ,  D.  R . ;  Hess, R. V . ;  and 
Upchurch, B. T.: Evaluat ion of Ca ta lys t  fo r  Closed Cycle Operation of High 
Energy Pulsed C 0 2  Lasers .  Coherent I n f r a r e d  Radar Systems and Appl ica t ions  
11, Proceedings of SPIE, Vol. 415, 1983, pp. 112-117. 
118 
B.E.T. Surface area: 6.7m*/g 
Tem pe ra t u re: 10 Ooc 
1 -  
I I I 
X 
# 
1 
X 
X 
X 
X 
Figure  1. Conversion e f f i c i e n c y  of c a t a l y s t  v e r s u s  sample weight .  
Open cycle (flow through) 
Closed cycle with catalyst (1509 1% Pt/SnOn at 100°C) 
----------------------------- 
(28 hr) 
c 
i 
a, 
In 
((I 
0 
- 
0)  3- 
2- 
E 
io3 i o 4  io5 
Total pulses (pulse rate = 10 p.p.s.) 
Figure  2. Performance of pulsed C02 l a y e r  w i t h  and wi thout  
recombination c a t a l y s t .  
119 


Catalysts for long-life closed-cycle CO2 lasers

Catalysts for long-life closed-cycle CO2 lasers

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