ANALYSIS OF INTERMEDIATE AND FINAL PRODUCTS OF AN EXPLOSIVE REACTION

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HAL Id: jpa-00226647

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Submitted on 1 Jan 1987

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PRODUCTS OF AN EXPLOSIVE REACTION

A. Pfeil, N. Eisenreich, H. Krause

To cite this version:

A. Pfeil, N. Eisenreich, H. Krause. ANALYSIS OF INTERMEDIATE AND FINAL PRODUCTS OF AN EXPLOSIVE REACTION. Journal de Physique Colloques, 1987, 48 (C4), pp.C4-209-C4-221.

�10.1051/jphyscol:1987415�. �jpa-00226647�

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JOURNAL DE PHYSIQUE

Colloque C4, suppl6ment au n'g, Tome 48, septembre 1987

ANALYSIS OF INTERMEDIATE AND FINAL PRODUCTS OF AN EXPLOSIVE REACTION

A. PFEIL, N. EISENREICH and H. KRAUSE

Fraunhofer-Institut

I.C. T.,

7507 PfinztaZ,

F.R.G.

Rbsum6.- Les produits gazeux du mat6riau 6nerg6tique RDX ont kt6 etudi6s par spectroscopie rapide (TOF, spectroscopie W/VIS r6solue dans le temps, FTIR) apres stimulation thermique impliquant differentes vitesses de transfert dt6nergie (chauffage lent dans

un

analyseur thermique, combustion dans une bombe sous pression, irradiation par breves impulsions laser).

Abstract.- The gas products of the energetic material RDX were studied by fast spectroscopic methods (TOF, time resolved W/VIS spectroscopy, FTIR) after thermal stimulation involving different energy transfer rates (slow heating in a thermal analyzer, combustion in

a

pressurized bomb, irradiation by short laser pulses).

INTRODUCTION

What i s an e x p l o s i v e r e a c t i o n ? T a l k i n g i n h e a t i n g r a t e s a c o m b u s t i o n i s i n t h e o r d e r o f l o 5 K / s a n d a d e t o n a t i o n o v e r 10" K / s . One i s d e a l i n g w i t h v e r y f a s t e v e n t s a n d c o n s i d e r i n g t h e h i g h t e m p e r a t u r e s a n d p r e s s u r e s i n v o l v e d t h e c h e m i s t r y i s d i f f i c u l t t o a s s e s s , e s p e c i a l l y when h u n t i n g " p r i m a r y s p e c i e s " .

We a p p r o a c h t h i s t a s k i n a p p l y i n g s c a l e d h e a t i n g r a t e s c o n t r o l l i n g p r e s - s u r e and t e m p e r a t u r e : ( 1 ) s l o w h e a t i n g w i t h on l i n e E G A b y f a s t F T I R ( h e a t i n g r a t e s i n t h e o r d e r o f 1 K / s ) , ( 2 ) c o m b u s t i o n i n a p r e s s u r i z e d bomb w i t h t i m e r e s o l v e d s p e c t r o s c o p i c o b s e r v a t i o n ( l o 4 t o 1 0 K / s , 5 r a t e s d e t e r m i n e d b y s a m p l e a n d p r e s s u r e ) a n d ( 3 ) i r r a d i a t i o n by s h o r t l a s e r p u l s e s ( e s t i m a t e d r a t e 10'' K / s , t y p i c a l l y l o 8 W/cm 2 1.

As an e x a m p l e r e s u l t s w i l l b e d e s c r i b e d on t h e e n e r g e t i c n i t r a m i n e RDX.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987415

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EXPERIMENTAL

( 1 ) S l o w h e a t i n g .

We r e c o r d w e i g h t l o s s ( T G ) a n d h e a t r e l e a s e (DTA) on a M e t t l e r TA 3 0 0 0 s y s t e m i n an AR a t m o s p h e r e . S a m p l e w e i g h t i s 5 mg.

F i g . 1 shows t h e c r o s s s e c t i o n o f t h e c e l l e m p l o y e d f o r t h e on l i n e I R s p e c t r o s c o p i c a n a l y s i s b y N i c o l e t 60SX F o u r i e r T r a n s f o r m s p e c t r o- m e t e r . The o p t i c a l p a t h i s 2 0 cm a n d t h e t u b e i s e q u i p p e d w i t h a n h e a t i n g w i r e . The c e l l t e m p e r a t u r e c a n b e l i n e a r l y r a i s e d t o 3 0 0

O C

a n d i s a c c u r a t e t o +/- 2 ' ~ .

A1 = a l u m i n u m f o i l H

=

h e a t i n g w i r e s

J =

h e a t i n s u l a t i o n K

=

c u v e t t e

P =

s a m p l e p a n

T i = t h e r m o c o u p l e I n s i d e l a a t h e r m o c o u p l e o u t s i d e

F i g . 1 C r o s s s e c t i o n o f t h e c e l l e m p l o y e d f o r EGA b y FTIR.

( 2 ) C o m b u s t i o n i n a p r e s s u r i z e d bomb.

The s e t - u p o f t h e t i m e - r e s o l v e d s p e c t r o s c o p i c m e a s u r e m e n t s i n t h e bomb

i s shown i n F i g . 2. The bomb has an i n n e r d i a m e t e r o f 80 mm a n d i s

e q u i p p e d w i t h t w o q u a r t z w i n d o w s f o r t h e o p t i c a l o b s e r v a t i o n . P r e s s u r e s

up t o 50 MPa c a n b e a p p l i e d . The d i a m e t e r o f t h e w i n d o w s i s 50 mm a n d

t h e y a l l o w a g o o d v i e w o n t o t h e s a m p l e s .

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The l i g h t e m i t t e d b y t h e f l a m e o f t h e b u r n i n g s a m p l e i s c o l l e c t e d b y s p e c i a l l e n s e s and f o c u s s e d o n t o t h e e n t r a n c e s l i t o f a J a r r e l Ash 27.5 mm s p e c t r o g r a p h . S p e c t r a c a n b e r e c o r d e d i n t h e 250 t o 550 nm s p e c t r a l r a n g e a n d a r e t a k e n a1 ong t h e f l a m e as c l o s e t o t h e b u r n i n g s u r f a c e as p o s s i b l e . The e m i s s i o n i s v i e w e d t h r o u g h a 0.2 mm p i n - h o l e a n d d e t e c t e d

b y a T r a c o r TN-6500 r a p i d s c a n s y s t e m .

The s p a t i a l r e s o l u t i o n o f t h i s s e t - u p i s 2 0 0 pm, t h e t i m e r e s o l u t i o n 10 msec a n d t h e s p e c t r a l r e s o l u t i o n 0 . 1 nm.

Tracor TN - 6500

Rapid Scan Spectrometer Window Bomb

F i g . 2 R e c o r d i n g o f t i m e - r e s o l v e d e m i s s i o n f r o m RDX c o m b u s t i o n .

( 3 ) L a s e r p u l s e h e a t i n g w i t h t i m e - o f - f l i g h t o b s e r v a t i o n .

F i g . 3 d e p i c t s t h e e x p e r i m e n t a l s e t - u p . The p u l s e o f t h e Nd/YAG 1 a s e r ( R I L ) i s c o n d u c t e d by a s e t o f m i r r o r s ( S p ) i n t o t h e s a m p l e c o m p a r t - m e n t o f t h e t i m e - o f - f l i g h t mass s p e c t r o m e t e r (TOF) a n d f o c u s s e d by a s p e c i a l l e n s ( F L ) o n t o t h e s a m p l e s u r f a c e .

The p u l s e g e n e r a t e s a p l u m e o f p y r o l y s i s p r o d u c t s d i r e c t l y i n f r o n t o f t h e e n t r a n c e s l i t o f t h e TOF. The i o n s a r e d e t e c t e d b y t h e i o n s e n s i t i - v e e l e c t r o n mu1 t i p 1 i e r E M 1 9 6 4 3 ( I M T ) a n d a 5 0 0 M H z B i o m a t i o n r e c o r d s t h e g e n e r a t e d s p e c i e s ( T R ) . The d a t a a r e s t o r e d on a f l o p p y d i s c

( F l op 1.

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B

⁸

i r i s , DR = d i f f u s e r e f l e c t o r , DS = d r i f t tube, DV = data p r o c e s s o r , F L = f o c u s s i n g l e n s , FLOP = storage u n i t , He/Ne = p f l o t l a s e r , I F = i n t e r f e r e n c e f i l t e r , I L = ion l e n s , I M T = ion s e n s i t i v e m u l t i p l i e r , NG = neutral d e n s i t y f f l t e r , OK = o c u l a r , OS = $ c o p e , P = sample, PD = photodiode, PF = p o l a r i s a t i o n f i l t e r , R I L = s o l i d s t a t e l a s e r , Sch = recorder, Sp = mirror, S t = beam s p l i t t e r , ?OF = t i m e - o f - f l i g h t mass s p e c t r o - meter, TP = t h e r s o p i l e , TR = t r a n s i e n t recorder.

F i g . 3 Scheme o f t h e l a s e r p y r o l y s i s s e t - u p w i t h TOF o b s e r v a t i o n . The l e n g t h o f t h e d r i f t t u b e i s 2 , 2 6 m a n d t h e a c c e l e r a t i n g v o l t a g e i s a b o u t 3 kV.. D e p e n d i n g on t h e p l u m e p r o p e r t i e s masses up t o 5 0 0 amu c a n b e d e t e c t e d a n d t h e r e s o l u t i o n a t 1 0 0 amu i s 1 amu.

A t h e r m o p i l e ( T P ) m o n i t o r e s t h e o u t p u t o f t h e l a s e r so t h a t i t c a n b e k e p t a t t h e i o n i s a t i o n t h r e s h o l d o f t h e s a m p l e . T y p i c a l power d e n s i - t i e s a r e l o 8 ~ i c m ~ ( 1 0 0 u J e n e r g y , f o c a l d i a m e t e r 30 u, p u l s e

l e n g h t 1 0 n s e c ) . We a c h i e v e d t h i s b y p l a c i n g a s e t o f n e u t r a l d e n s i t y f i l t e r s ( N F ) i n t o t h e l a s e r beam. W a v e l e n g t h o f i r r a d i a t i o n : 532 nm.

Mass n u m b e r s w e r e a s s i g n e d t o t h e TOF s i g n a l s u s i n g t h e e q u a t i o n

t

=

a r o o t ( m + b ) , ( 1 )

w h e r e b y t

=

t i m e , a = i n s t r u m e n t a l c o n s t a n t , m = s i n g l e c h a r g e d mass

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a n d b = t i m e l a g b e t w e e n t r i g g e r p u l s e a n d t h e a c t u a l b e g i n o f t h e p y r o l y s i s . The p a r a m e t e r s a a n d b a r e d e t e r m i n e d b y a l i n e a r r e g r e s - s i o n a n a l y s i s f r o m known TOF s i g n a l s .

RESULTS AND DISCUSSION

(1) T h e r m o a n a l y t i c a l e x p e r i m e n t s

T h e s e e x p e r i m e n t s c h a r a c t e r i z e t h e t h e r m a l r e a c t i v i t y o f R D X b y r e c o r - d i n g TG a n d DTA. B o t h a r e shown i n F i g . 4: L i q u e f a c t i o n p e a k i n g a t 2 0 4

^{O C ,}

t h e n s t r o n g e x o t h e r m i c , l o s s o f w e i g h t s t a r t i n g a t 1 5 0 ~ ~

( h e a t i n g r a t e 5 K / m i n ) .

The k i n e t i c a n a l y s i s b y a f i t t o t h e TG c u r v e b y a n o n - l i n e a r l e a s t - s q u a r e s p r o g r a m g i v e s a 1. o r d e r r e a c t i o n w i t h an a c t i v a t i o n e n e r g y o f 2 3 2 K J I m o l e . The a n a l y s i s i s shown i n F i g . 5.

F i g . 6 d e p i c t s t h e F T I R o n - l i n e a n a l y s i s o f t h e g a s e s e v o l v e d . The s p e c t r a w e r e r e c o r d e d i n t h e G C mode w i t h a r e s o l u t i o n o f 4 cm- 1 a n d 6.7 s / s c a n . The t e m p e r a t u r e c h a n g e per s c a n was 0.5

^{O C .}

We i d e n t i f i e d H C N , NO, N20, N H 3 , CH20, CH30H, CO, C02 a n d H20.

The p r o f i l e s ( a b s o r b a n c e v s t e m p e r a t u r e ) a r e shown i n F i g . 7 .

F i g . 4 DTA a n d T G c u r v e s o f RDX ( h e a t i n g r a t e 5 K / m i n ) .

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F i g .

D I G - o C ; / S

F i g .4- Continued

120.00 140.00 160.00 180.00 200. 00 220.00 240.00

a a

-

2

a

2

a

h

9

^a

2

^a

5

0

a a e TEi'lP I C I

TG c u r v e k i n e t i c a n a l y s i s

by

a non-1 i n e a r l e a s t - s q u a r e s f i t .

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C4-215

RD X NEA T Fig . 6 FTI R spectr a o f th e evolve d gase s versu s temperature .

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R D X NEAT

F i g . 7 I R a b s o r b a n c e p r o f i l e s o f t h e m a i n p r o d u c t s o f RDX p y r o l y s i s ( h e a t i n g r a t e 5 K l m i n ) .

H C N , N20 a n d H2C0 h a v e s i m i l a r p r o f i l e s w i t h a maximum a t 2 2 0

O C

a s o p p o s e d t o NO a n d C02 whose c u r v e s l a g b e h i n d a n d w h i c h h a v e t h e m a x i m a l a b s o r b a n c e a t 2 5 0

O C .

W i t h r e s p e c t t o t h e f o r m e r , NO a n d C02 a r e s e c o n d a r y p r o d u c t s g e n e r a t e d a t a l a t e r s t a g e o f RDX d e c o m p o s i - t i o n .

The s y n c h r o n o u s p r o f i l e s p o i n t t o t h e c o m p e t i t i o n o f t w o d e g r a d i n g p a t h w a y s , t h e f o r m a t i o n o f HCN a n d t h e f o r m a t i o n o f N20 a n d H2C0.

R D X may decompose v i a t w o m e c h a n i s m s , one w h i c h p r o d u c e s N20 and CH20 i n v o l v i n g t h e c l e a v a g e o f C-N b o n d s . The o t h e r g e n e r a t e s HCN a n d N O x w h e r e b y N-N b o n d s a r e b r o k e n .

( 2 ) C o m b u s t i o n e x p e r i m e n t s

We i d e n t i f i e d t h e f l a m e s p e c i e s OH, HCN, NH, CHO (CH20) a n d t h e

m e t a l i m p u r i t i e s Na, K, Ca o n RDX c o m b u s t i o n i n a p r e s s u r i z e d bomb.

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The 0 . 1 nm r e t e d i n F i g . 8 s t r u c t u t e i s

s o l v e d emi s s i on s p e c t r a o f O H , C N , N H a t

. The c a l c u l a t i o n o f t h e t e m p e r a t u r e f r o m c u r r e n t l y b e i n g a t t e m p t e d .

LRHOA CNH3

1 b a r a r e d e p i c - t h e r o t a t i o n a l

F i g . 8 D e t a i l s o f O H , C N a n d N H e m i s s i o n f r o m R D X c o m b u s t i o n a t 1 b a t .

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The 1 . 0 nm r e s o l u t i o n s p e c t r a i n f o r m o n t h e d e p e n d e n c e o f t h e e m i s s i o n i n t e n s i t y on t i m e ( d i s t a n c e f r o m t h e b u r n i n g s u r f a c e ) a n d p r e s s u r e . Such p r o f i l e s ( e m i s s i o n i n t e n s i t y v e r s u s t i m e ) a r e d e p i c t e d i n F i g . 9.

CN a n d NH h a v e s i m i l a r p r o f i l e s w h i c h d i s p l a y a maximum i n c o n t r a s t t o OH w h i c h r i s e s w i t h i n c r e a s i n g d i s t a n c e f r o m t h e b u r n i n g s u r f a c e . F u r t h e r m o r e , when r a i s i n g t h e p r e s s u r e f r o m 1 t o 2 0 b a t t h e e m i s s i o n i n t e n s i t y r a t i o o f OH t o CN a n d N H i n c r e a s e s . Compared t o t h e CN a n d NH s p e c i e s OH d i s p l a y s a d i f f e r e n t t i m e h i s t o r y , c o m p a r a b l e t o C02 i n t h e s l o w h e a t i n g e x p e r i m e n t .

F i g . 9. I n t e n s i t y p r o f i l e s o f CN, NH, OH a t 5 b a r .

A f u r t h e r i n t e r e s t i n g f e a t u r e i s d i s p l a y e d i n F i g . 10. On i n c r e a s i n g p r e s s u r e a b r o a d b a n d d e v e l o p s c e n t e r e d a t 4 4 5 nm w i t h m a x i m a l i n t e n - s i t y ( w . r . t . CN) a t 1 0 b a r s . We a s s i g n e d t h i s s p e c i e s t o HCO a n d H2C0.

T h e s e p r o d u c t s c h a r a c t e r i z e a C - N b o n d c l e a v a g e f a v o u r e d t o t h e com-

p e t i n g N - N c l e a v a g e b y p r e s s u r e .

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550.00 300.00 350.00 UDO.00 USO.00 500.00 550.00 LAMDR C N M I

F i g . 10 S e q u e n c e o f

R D X

e m i s s i o n s p e c t r a a t 1 0 b a r

( s p e c t r a l r e s o l u t i o n 1 . 0 nm, t i m e i n t e r v a l s 1 0 0 m s ) .

( 3 ) L a s e r p u l s e h e a t i n g e x p e r i m e n t s

T h e c a t i o n w e r e m o r e i n f o r m a t i v e a n d e x a m p l e s o f f r a g m e n t a t i o n p a t t e r n s o f R D X a r e shown i n F i g s . 11 a n d 1 2 .

F i g . 11 TOF s p e c t r u m o f R D X s t i m u l a t e d by 120 m J l a s e t p u l s e .

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A t h i g h e r l a s e r e n e r g i e s ( a b o v e 1 0 0 u J , F i g . 1 1 ) f r a g m e n t s o f l o w e r mass n u m b e r s a p p e a r t y p i c a l l y a t 30 amu (NO) a n d 42 ( t h r e e r i n g members l i k e N-CH2-N a n d CH2-N-CH2). The s p e c i e s a t 7 5 amu i s m o s t i n t e r e s t i n g s i n c e i t c o u l d b e ( p r o t o n a t e d ) N - n i t r o f o r m i m i n e ( H 2 C = ~ ~ 0 2 ) , a h i g h l y d i s c u s s e d i n t e r m e d i a t e i n RDX d e g r a d a t i o n ( 1 ) .

B e l o w 1 0 0 u J ( F i g . 1 2 ) l a r g e r f r a g m e n t s w e r e o b s e r v e d w i t h mass n u m b e r s u p t o 8 4 amu. We a s s i g n e d t h e s e s p e c i e s t o s t r u c t u r a l e l e m e n t s o f t h e r i n g s t r i p p e d o f t h e

N O 2

g r o u p s : 42 amu ( 3 r i n g members, see a b o v e ) , 56 amu ( 4 r i n g m e m b e r s ) , 70 amu ( 5 r i n g m e m b e r s ) a n d 8 4 amu ( 6 membered r i n g ) . The f r a g m e n t s s u g g e s t t h a t t h e N-N c l e a v a g e m e c h a n i s m d o m i n a t e s .

F i g . 1 2 TOF s p e c t r u m o f RDX p y r o l y z e d b y a 76 u J l a s e r p u l s e .

REFERENCE

( 1 ) C h e m i s t r y o f N i t r a t e E s t e r s amd N i t r a m i n e P r o p e l l a n t s , R. A. F i f e r , F u n d a m e n t a l s o f S o l i d - P r o p e l 1 a n t C o m b u s t i o n , Eds. K. K . K . Kuo a n d M . S u m m e r f i e l d , P r o g r e s s i n A s t r o n a u t i c s a n d A e r o n a u t i c s , P r i n c e t o n N.J., 1 9 8 4 .

Cr i t i c a l A n a l y s i s o f N i t r a m i n e D e c o m p o s i t i o n D a t a : P r o d u c t D i s t r i b u t i o n s f r o m HMX a n d RDX D e c o m p o s i t i o n ,

M.A. Schr o e d e r , R e p o r t 1 9 8 5 , BRL-TR-2659.

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D i s c u s s i o n and ConcZusion -

J . C .

MIALOCQ

U l t r a f a s t P h e n o m e n a - L a s e r S p e c t r o s c o p y - T r a n s i e n t s t a t e s The m i c r o s c o p i c approach t o d e t o n a t i o n l e a d s t o an e s s e n t i a l q u e s t i o n : What i s t h e s t r u c t u r e o f t h e shock wave f r o n t i n condensed phase substances ? To answer t o i t , PRESLES s t u d i e s t h e b e h a v i o u r of o r g a n i c molecules such as n i t r o m e t h a n e under shock wave, i n t h e 80-100 k b a r p r e s s u r e domain. He has evidenced an e l e c t r i c p o l a r i z a t i o n e f f e c t which s h o u l d be due t o t h e appearance o f charged s p e c i e s . Moreover i n o r d e r t o understand t h e energy t r a n s f e r mechanisms i n m o l e c u l a r systems s u b m i t t e d t o a shock wave, he s t u d i e s i t s r i s e t i m e ( l o w e r l i m i t : 10-11 s ) w h i c h i s c e r t a i n l y o f a h i g h importance i n t h e b r e a k i n g o f chemical bonds : t h e method i s based on t h e measurement o f t h e o p t i c a l r e f l e c t i v i t y o f t h e m a t e r i a l (water, n i t r o m e t h a n e ) a t 6 kbar.

DUFORT has p r e s e n t e d i n s t a n t a n e o u s measurements o f t h e t e m p e r a t u r e i n n i t r o m e t h a n e and RDX under s u s t a i n e d shock. These measurements were performed u s i n g Raman Stokes and a n t i - S t o k e s i n t e n s i t i e s ; t h e y i n d i c a t e t h a t t h e r e i s no s p e c t r a l s h i f t i n RDX, b u t t h a t a 10 cm-1 s p e c t r a l s h i f t o c c u r s i n n i t r o m e t h a n e . The e x p e r i m e n t a l r e s u l t s ( p r e s s u r e and t e m p e r a t u r e ) a r e i n b e t t e r agreement w i t h t h e Cowperthwaite and Show s t a t e e q u a t i o n .

Because t h e g e n e r a t i o n o f shock waves u s i n g gas guns o r e x p l o s i v e s meets severe e x p e r i m e n t a l disadvantages, CAnIPILLO makes use o f t h e more p r a c t i c a l l a s e r method.

The e x p e r i m e n t a l setups a r e i n d e e d s m a l l e r and t h e y a l l o w 30 k b a r shocks g e n e r a t i o n a t a h i g h e r r e p e t i t i o n r a t e , 30 s h o t s Der h o u r w i t h a picosecond l a s e r system which d e l i v e r s a 20 mJ energy. CAMPILLO has c h a r a c t e r i z e d t h e l o c a l p r e s s u r e , t h e temper- a t u r e , t h e v i s c o s i t y , t h e c r y s t a l symmetry and t h e chemical n a t u r e o f molecules by s t u d y i n g t h e f l u o r e s c e n t p r o p e r t i e s o f probe dyes which have been d i s s o l v e d i n t h e l i q u i d s t o be s u b m i t t e d t o l a s e r shock.