CP620, Shock Compression of Condensed Matter - 2001
edited by M. D. Furnish, N. N. Thadhani, and Y. Horie
© 2002 American Institute of Physics 0-7354-0068-7/02/$ 19.00
ALUMINISED EXPLOSIVE COMPOSITIONS
BASED ON NQ AND BTNEN
Michael F. Gogulya, Alexander Yu. Dolgoborodov, Michael A. Brazhnikov,
Michael N. Makhov, and Vitaliy I. Arkhipov
N. Semenov Institute of Chemical Physics RAS, Kosygin st. 4, Moscow, 117334, Russia
Abstract. Aluminium containing explosive compositions based on nitroguanidine (NQ) or bistrinitroethylnitramine (BTNEN) were studied. The tested compositions contained Al (15% wt.) of different
particles' size and particles' shape. There were measured the following explosive parameters: detonation velocity, pressure time histories and temperature time histories, velocity of accelerated metal plate,
explosion heat. NQ pressure profile is of the shape predicted by ZND theory, thus C-J pressure was estimated. BTNEN detonation seems to be of more complicated nature. Effect of Al introduction into HE
depends on the nature of HE and Al particles' size and shape as well.
Al. Aluminium content in mixtures was 15% wt.
NQ-crystals with low loose-packed density of 0.2
g/cm3 had needle-like shape and were about 5-10
fim of thick and about 50 j^m in length. BTNEN
particles had needle-like shape with diameter of 1540 jLim and length up to 500 jum. Components of the
mixtures merged in hexane were mixed in a rotating
drum or manually. Then it was evaporated from the
mixture at its boiling point (-70° C). Charges were
pressed to density about 0.90-0.95 TMD.
INTRODUCTION
Aluminium is widely used as an additive enhancing detonation characteristics of HE. However, the
mechanism of Al oxidation in and behind detonation wave is not well understood. This problem attracted new interest after ultra-fine Al (< 0.1 jum)
became available [1]. For study, there were chosen
two HE: BTNEN and NQ. The interest to BTNEN
is due to its high density (1.96 g/cm3) and positive
oxygen balance (OB = +16.5%). NQ, explosive
with negative OB (-30.8%), is of particular interest
as HE with high hydrogen content.
EXPERIMENTAL TECHNIQUES
Detonation velocity (D) was measured with the
aid of a set of contact gauges (0.1 mm of thick)
made of copper foil insulated with a plastic film.
The time interval of detonation front travel was recorded by the frequency meter with an accuracy of
0.01 jus. Pressure histories and temperature ones
were measured with the aid of dual-channel optical
pyrometer (A,=420 and 627 nm) with time resolution
about 10 ns. Indicator technique was used for pressure profile measurements [2]. Bromoform 20 mm-
PREPARATION OF HE/A1 CHARGES
Five Al batches were tested including spherical
particles with size <0.1{0.9}; 7{0.98}; 15(0.99};
150(0.99} M-m and flaked Al with size «lx20x20
jim {0.85}, containing 3.8% stearine,. Here figures
in parentheses indicate content of active Al. The
aforementioned Al batches are referred to below as
Al(0.1), Al(7), Al(15), Al(150) and Al(fl) for flaked
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thick layer was used as an indicator. Temperature
measurements were performed by means of window
technique [3]. LiF plate served as a window. When
measuring D or temperature histories or pressure
ones, HE samples were initiated with a plane wave
generator made of RDX-wax composition. Charges
40 mm in diameter and -100 g in weight were
tested. Plate acceleration technique [4] consists in
measurements of the velocity of a 4-mm steel plate
accelerated by detonation products (DP) in the direction of detonation wave propagation. NQ basic
charge was 35-mm long. The length of BTNEN
charge was 40 mm. The plate velocity was measured with an accuracy of ~1%. Explosion heats
(EH) were measured in a bomb calorimeter made of
steel vessel 5 litre in volume with an accuracy of
-1%. It is placed in a compartment with a distilled
water [5]. For EH measurements, NQ and NQ/A1
mixtures were pressed in charges of 30 mm in diameter and 50-60 g in weight and placed into the
10-mm thick stainless steel casing. BTNEN and
BTNEN/A1 mixtures were pressed in charges of 20
mm in diameter and 40-45 g in weight and placed
into 7-mm thick casing of the same metal. In all
aforementioned tests except EH and metal plate
acceleration measurements hi BTNEN mixtures,
there was used an additional RDX pellet (p0 = 1.68
g/cm3) 10 mm of thick to reinforce the initiation
impulse.
energy release caused by Al oxidation. In addition,
one should concern energy losses through additive
compression and its heating up. Competition of
them controls D value.
TABLE 1. Detonation Velocity
HE
Po, g/cm3
Al
BTNEN
0
Dex,
g/cm3 km/s
POHE?
(n)
D*,
km/s
-
1.635(0.918) 1.635
7.94
7.94
Al(15)
1.743 (0.929) 1.640
7.94
7.92
Al(fl)
1.720(0.916) 1.616
7.78
7.86
Al(O.l) 1.785(0.951) 1.684
8.13
7.93
1.870(0.954)
-
8.50
1.909(0.974)
-
8.66
8.62
Al(150) 1.965(0.961) 1.875
8.38
1.955(0.956) 1.864
8.30
8.44
1.955(0.956) 1.864
8.28
8.42
8.04
8.35
Al(15)
Al(7)
Al(O.l) 1.914(0.936) 1.820
TABLE 2. D(p) Relationship
b,
a,
HE
(km cm3)/g s
km/s
8.48
POHE*>
g/cm3
Ref.
[7]
NQ
1.44
4.015
1.635
BTNEN
1.24
3.885
1.900
[6f
**Data of the present work are also included for D(POHE)
relationship construction.
EXPERIMENTAL RESULTS
8.6
Detonation velocity data are listed hi Table 1,
where p0 and t| are the absolute and relative charge
density, Dex is experimental D and POHE is the density of HE in mixture. Basing on the relationship Did
= a + bpoHE for pure HE, one can recalculate D
measured at different charge density to those (D*)
would be measured at the same density of HE in the
mixture (POHE*): D*= Dex - b(pOHE - POKE*)- The
coefficients, a and b, and POHE* are given hi Table 2.
D* values are listed in Table 1 and they are plotted
in Fig. 1. For comparison, the data for HMX/A1 are
also presented. The results on D are influenced by a
number of factors. First one is the decreasing of the
number of moles of gaseous DP caused both by the
decreasing of HE amount in the mixture and by the
Al reaction with carbon oxides. Second factor is the
8.4
1
."*- 8-2
Q
8.0
7.8
0
20
40
60
80
100 120 140
FIGURE 1. Detonation velocity versus Al particles' size: o BTNEN/A1; A - NQ/A1 (A - NQ/Al(fl)); • - HMX/A1
hi Fig. 2, 3 there are given pressure histories in DP
for tested mixtures. For NQ, Fig. 2 demonstrates that
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the C-J pressure would fall in interval of (22.1-^21.6)
GPa, with corresponding polytrope index of 3.66
-5-3.77 and the detonation reaction zone of (0.7-fl.O)
mm. Opposite to NQ, BTNEN pressure profile is not
a classical one. The peculiarities seen for BTNEN at
the front during first 0.05 jus retain for BTNEN/A1
mixtures. They are possibly caused by the macroscopic kinetic of BTNEN decomposition.
4400
4000
in
3600
H
3200
£
2800
W
2400
2000
-0.4 0.0
0.4
0.8
1.2 1.6
2.0
2.4
2.8
TIME, microsecond
FIGURE 4. Brightness temperature time histories with LiF used
as the window (A, = 627 nm). 1 - BTNEN; 2 - BTNEN/A1(15); 3 BTNEN/A1(0.1); 4 - NQ; 5 - NQ/Al(fl); 6 - NQ/A1(0.1). The
instant of time pointed as zero corresponding to the detonation
wave entrance DP/LiF interface.
0.0
0.2
0.4
0.6
For NQ and NQ/A1 charges, data on metal plate
acceleration velocity (W) are presented in Fig. 5.
For NQ, the tests were performed at two densities.
0.8
TIME, microsecond
FIGURE 2. Pressure time histories in the DP for NQ and NQ/A1
mixtures. The arrow shows C-J point for NQ.
1.70
1.65
0.0
0.2
0.4
mm
20
30
40
FIGURE 5. Steel plate velocity vs. distance for NQ and NQ/A1.
1 - Al(fl); 2 - Al(O.l); 3 - Al(15); Dash - pure NQ.
0.6
TIME, microsecond
The increase of NQ-charge density by 0.1 g/cm3
results in W increase by ~90 m/s. The curves for
NQ/A1 mixtures were recalculated from the experimental data to NQ porosity in the charge of ~ 8%
basing on the W-p relation for NQ. Increase in
metal plate velocity is of -3.1% for NQ/A1 over
pure NQ at AL = 40 mm. The curves for BTNEN
and BTNEN/A1 are given in Fig. 6. For BTNEN,
the tests were performed at two densities. The increase of BTNEN density by 0.1 g/cm3 results in W
FIGURE 3. Pressure time histories in the DP for BTNEN and
BTNEN/A1 mixtures.
Brightness temperature histories are shown in Fig.
4. For HE/A1, rapid temperature decrease at 1.2 - 1.6
^s is caused by rarefaction entered to the observing
area. NQ/Al(fl) temperature curve can be explained
by peculiarities of component package in the charge.
It is seen that free oxygen of BTNEN DP reacts with
Al more actively.
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increase by -80 m/s. Trajectories for BTNEN/Al
were recalculated in the same manner to BTNEN
porosity in the charge -3%.
Al(7) activity (98% over -90%). EH data are given
in Table 3. EH of BTNEN/A1(7) is the highest due
to the relatively small particles and high pure Al
content. On the condition of the complete Al oxidation in DP of BTNEN, one can estimate the EH as ~
8600 kJ/kg at content of pure Al 15% and that for
DP of NQ as -5600 kJ/kg. The estimation indicates
that for BTNEN (positive OB) there is complete Al
oxidation in DP expanding in calorimetric bomb
only for Al(7) and Al(O.l). For any tested NQ/A1
mixtures, there is no complete Al oxidation by DP
ofNQ.
CONCLUSION
Effect of Al introduction into HE depends on the
nature of HE and Al particles' size and shape as well.
Ultra-fine Al manifests itself as an active powder
among the tested ones. The advantages of ultra-fine
Al caused by lesser particles' sizes are restricted by
lower content of pure Al in powder. Al starts react
with DP in detonation zone or immediately behind it,
but the most part of Al oxidises in expanding DP at
larger times.
1.720
30
40 AL,mm
FIGURE 6. Steel plate velocity vs. distance for BTNEN and
BTNEN/Al: 1 - Al(7); 2 - Al(15); 3 - Al(O.l); 4 - Al(150); dash
line corresponds to pure BTNEN.
It is seen that BTNEN/A1(7) and BTNEN/A1(15)
mixtures provide higher gain in metal plate velocity
than do the mixtures with EH of negative OB, e.g.
HMX [8]. In similar mixture with BTNEN, the plate
velocity augments by nearly 6% at AL = 40 mm.
REFERENCES
1. Gen M. Ya., and Miller A. V., Patents of USSR, No
814432 and No 967029.
2. Gogulya M. F., and Dolgoborodov A. Yu., Chem.
Phys. Rep. 13(12), 2059-2069 (1995).
3. Gogulya M. F., and Brazhnikov M. A., "Radiation of
Condensed Explosives and Its Interpretation (Temperature Measurements)," in Proceedings of the 10-th
International Symposium on Detonation, Boston1993, Office of Naval Research, ONR 33395-12,
1995, pp. 542-548.
4. Arkhipov V. I., Makhov M. N., and Pepekin V. I.,
Sov. Jnl Chem. Phys. 12(12), 2395-2399 (1994).
5. Pepekin V. L, Makhov M. N., Lebedev Yu. A., Dokl.
Akad Nauk, 232(4), 852-855 (1977), (in Russian).
6. Kamlet M. J., and Hurwitz H. J., Chem. Phys., 48(8),
3685-3692 (1968).
7. Price Donna and Clairmont A. R., "Explosive Behavior of Nitroguanidine," in Proc. Twelfth Symp.
(Intern.) on Combustion, The Combustion Institute,
Pittsburgh, Pennsylvania, 1969, pp. 761-770.
8. Arkhipov V. L, Makhov M. N., Pepekin V. L, etal.,
Khim. Fiz., 18(12), 53-57 (1999), (in Russian).
TABLE 3. Explosion Heat
HE
BTNEN
£
AI
po, g/cm3
Q,kJ/kg
-
1.635
3480
Al(15)
1.743
4820
Al(fl)
Al(O.l)
1.720
4930
1.785
4960
-
1.889
5230
Al(150)
1.945
8250
Al(15)
1.955
8450
Al(7)
1.945
8580
Al(O.l)
1.914
8420
Though plate acceleration ability of BTNEN is
lower than that of HMX, the acceleration ability of
BTNEN/Al approaches that of pure HMX at the
same porosity. The advantages of Al(7) over Al(O.l)
in metal plate velocity can be explained by higher
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