Synthesis, performance, and thermal behavior of a novel insensitive EDNA/DAT Co-crystal

Article abstract of DOI:10.1002/zaac.201800041

Due to the acidity and the limited applications of 1,4-dinitro-1,4-diazabutane (EDNA), a novel nitrogen rich energetic co-crystal based on EDNA and 1,5-diaminotetrazole (DAT) in a 1:2 molar ratio was synthesized. The formation of the co-crystal was tested by scanning electron microscope (SEM), powder X-ray diffraction (PXRD) and Raman spectroscopy. Based on the elemental analysis and the enthalpy of combustion obtained by the calorimetric bomb, the enthalpy of formation was calculated to be 196.9 kJ·mol^–1. Sensitivity to impact was measured and 50 % probability of initiation was 9.7 J for the co-crystal. In addition, the detonation characteristics were predicted by EXPLO5 Code. The detonation velocity (D) and the detonation pres-sure (P) of the co-crystal are 8254.5 m·s^–1 and 26.7 GPa, respectively. The thermal behavior and decomposition kinetics of the co-crystal and the coformer were described using nonisothermal differential scanning calorimetry (DSC) and thermogravimetry/differential thermogravimetry (TG/DTG) techniques. There is an obvious difference between the thermal behavior of the co-crystal and the coformer. The activation energy of the co-crystal (125.3 kJ·mol^–1) is lower than the coformer. The obtained co-crystal has high nitrogen content and acceptable sensitivity to external stimuli, which makes it promising for expanding the reuse of EDNA in ammunition after overcomeing its acidity problem.

Full text of DOI:10.1002/zaac.201800041

Title: Synthesis, performance and thermal behavior of a novel
insensitive EDNA/DAT cocrystal
Authors: Ahmed K. HUSSEIN, Svatopluk ZEMAN, and Ahmed Elbeih
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To be cited as: Z. anorg. allg. Chem. 10.1002/zaac.201800041
Link to VoR: http://dx.doi.org/10.1002/zaac.201800041

Zeitschrift für anorganische und allgemeine Chemie
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ARTICLE
Synthesis, performance and thermal behavior of a novel
insensitive EDNA/DAT co-crystal
[
a]
[a]
[b]
Ahmed K. HUSSEIN , Svatopluk ZEMAN , Ahmed ELBEIH*
a
Institute of Energetic Materials, Faculty of Chemical Technology, University of Pardubice, Czech Rep
Military Technical College, Kobry Elkobbah, Cairo, Egypt
b
Abstract: Due to the acidity and the limited applications of of 1,4-
adding insensitive compounds such as; phlagmatized
explosives, mixutre of explosives [3a, 3b]or coatings by polymers
dinitro-1,4-diazabutane (EDNA). A novel nitrogen rich energetic co-
crystal based on EDNA and 1,5 diaminotetrazole (DAT) in a 1:2
molar ratio was synthesized. The formation of the co-crystal was
tested by Scanning electron microscope (SEM), powder X-ray
diffraction (PXRD) and Raman spectroscopy. Based on the
elemental analysis and the enthalpy of combustion obtained by the
calorimetric bomb, the enthalpy of formation was calculated to be
“
PBX” [4a, 4b, 4c]. However, all the previously mentioned method
can’t optimize between the main characteristics; high
performance, thermodynamic stability and low sensitivity [5].
Recently, new approach has been introduced “Co-crystal
technique” which succeeds to combine coformers “different
explosive materials” with each other. This technique is one of
the main types of superamolecules which based on the
intermolecular interaction as hydrogen bond, bi-stacking, van
der Waals forces and halogen bonds [5b]. This intermolecular
interaction (Co-crystal) can connect two different molecules
together in one crystal form, which can improve the solubility,
-
1
1
96.9 kJ.mol . Sensitivity to impact was measured and 50%
probability of initiation was 9.7 J for the co-crystal. In addition, the
detonation characteristics were predicted by EXPLO5 Code. The
detonation velocity (D) and the detonation pressure (P) of the co-
[
6]
performance and sensitivity . These technique had been
announced in pharmaceutical systems, it had been succeed with
-
1
crystal are 8254.5 m s and 26.7 GPa respectively. The thermal
behavior and decomposition kinetics of the co-crystal and the
coformer were described using nonisothermal differential scanning
different drugs to improve the bioavailability and the solubility [7]
.
It was also passed down to energetic materials science and
different publication were studied theoretically and were
calorimetry
(DSC)
and
thermogravimetry/differential
performed experimentally by combining two different energetic
materials, as an example; CL-20 co-crystals [8], TNT co-crystal
thermogravimetry (TG/DTG) techniques. There is an obvious
difference between the thermal behavior of the co-crystal and the
[8c, 9]
and HMX co-crystal [8a, 9b, 10] or with inert material such as;
-
1
CL20/ caprolactam [10a] and other more.
coformer. The activation energy of the co-crystal (125.3 kJ.mol ) is
lower than the coformer. The obtained co-crystal has high nitrogen
content and acceptable sensitivity to external stimuli which possess
it to be a promising for expanding the reuse of EDNA in ammunition
after overcomeing its acidity problem.
1,5-diaminotetrazole (DAT) (shown in Fig: 1.a) is one of the
family of Tetrazoles which are the core of aza in the heterocyclic
compounds. The high positive enthalpies of formation and high
nitrogen content of tetrazoles have made their complexes
interesting for energetic materials investigation and research
topics. They are involved in new researches focused on
reducing impact on environment and synthesized green
energetic materials [11]. They are heterocyclic compounds rich in
1. Introduction
electron pairs, and can coordinate with transition-metal ions.
These compounds are thermally stable and yield a large volume
of gas on thermal decomposition, so as to be used as
prospective gas-generating, blowing agents for polymeric
systems and other combustible and thermally decomposition
Energetic materials; explosives, propellants and pyrotechnics,
are used for variety of military purposes and civilian
a
[
1]
applications . However, there are unacceptable explosive
characteristics when using single crystal explosive materials,
among them: low performance, high sensitivity to external
stimuli, the insufficient physical properties of some explosives.
Consequently, programs have been established worldwide to
develop novel energetic materials with higher potential energy
and enhanced insensitivity by synthesizing new energetic
systems. DAT is one of the organic compounds, which has high
content of nitrogen (84.0%) [12], it has a positive heat of
-1
-3
formation (310.37 kJ.mol ), its density is 1.75 g.cm ,and the
detonation velocity is 7570 m.s-1[13]. It has a unique structure and
remarkable properties; It is used in key intermediate in many
organic synthesis, the medicinal and biological applications.
[
2]
materials, preparing nanoscale particles of explosives
or
1
,4-dinitro-1,4-diazabutane (EDNA) also known as Haleite [14]
(
shown in fig. 1.b) was first described as high explosive which
[
[
a]
b]
Ahmed K. Hussein, Svatopluk Zeman.
was used during the WorldWar II in antitank ammunitions. It
was used also in different application as secondary explosive,
booster explosive and in the preparation of cast explosives
such as ednatol (55% EDNA + 45% TNT). It has very
Institute of Energetic Materials, Faculty of Chemical Technology
University of Pardubice, CZ-532 10 Pardubice
Czech Republic
Ahmed Elbeih
interesting properties, possessing
a
high brisance,
Military Technical College, Kobry Elkobbah, Cairo, Egypt
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ARTICLE
comparatively low impact sensitivity and high heat sensitivity. In
contradiction with the above mentioned properties, there is a
problem using EDNA as it has a high chemical acidic reactivity
that drawback its chemical instability. EDNA is highly acidic (pK
a1=5.31 and pK a2 = 6.64) [15]. It is corrosive and can react with
metals and metal salts [14]. In this study, we describe the use of
co-crystallizations to change the acidic affinity of EDNA by
stabilization using the DAT and consequently increase the
durability of EDNA in different applications by adding the high
nitrogen content heterocyclic DAT.
According to the small size of the co-crystal sample and the
limited features of the available single crystal XRD, the co-
crystal was measured by powder XRD. Comparing the XRD
results of the co-crystal with the pure coformer, it has been
confirmed that the formed co-crystal is different from its
components. By comparing XRD spectra with the Mixture, it can
be found that mixture is combing the XRD peaks of pure EDNA
and DAT and different from EDNA/DAT co-crystal which gave
another confirmation of the formation of the co-crystal. The XRD
patterns are shown in Figure 2. The main diffraction angles of
o
o
o
NH2
the EDNA/DAT co-crystal localized at 34.78 , 29.74 , 27.66 ,
H C
NHNO2
2
o
o
o
2
3.38 , 19.74 , and 17.22 are evidently different from the raw
N
H N
N
materials EDNA and DAT and their mixture. In the 2Ɵ range of
2
H C NHNO2
10–40, some of the peaks for EDNA and DAT have disappeared,
such as the peaks at 35.02 , 25.02 for DAT and 16.44 , 26.3 ,
2
N
N
o
o
o
o
o
o
o
o
o
3
0.08 , 33.38 , 35.06 , 37.78 , 42.6 of EDNA and new peaks
(
a)
(b)
localized at 34.78 , 27.66 and 24.74 o are observed in the
diffraction pattern of the co-crystal when compared with the
PXRD pattern of the Mixture. These differences enable easy
distinction between the co-crystal and pure raw DAT or EDNA,
as shown in Figure 2. The unique XRD patterns of the co-crystal
indicate that it is a new substance instead of the separate
crystallization of the raw materials
o
o
Figure 1: Chemical structures of a) DAT and b) EDNA
2
. Results and Discussion
4
.1. Powder XRD
a.
EDNA/DAT Co-crystal
b.
EDNA/DAT Mixture
c.
DAT
d.
EDNA
Figure 2: A comparison of powder XRD Spectra for a. EDNA/DAT Co-crystal, EDNA/DAT Mixture, c. DAT and d. EDNA.
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(a)
(b)
(c)
Figure 3: SEM image of a. EDNA crystal, b. DAT crystal and c. EDNA/DAT Co-crystal
The explosives characteristics were calculated by the EXPLO5
program and listed in Table 2 after the calculation of heat of
formation and the data exist from the elemental analysis.
From the obtained data, the positive heat of formation and high
nitrogen percentage of the coformer DAT provide a positive
influence on the performance characteristics of the produced co-
crystal EDNA/DAT. The detonation velocity of the EDNA/DAT
co-crystal is 8254.5 m.s-1 and the detonation pressure is 26.7
GPa which are slightly lower than of EDNA but it is much higher
than DAT.
4
.2. SEM
The SEM images of coformer EDNA, DAT, and their co-crystal
are shown in Figure 3. In Figure 3 (a), the morphology of raw
EDNA particles presents the shape of polyhedron with uneven
distribution, and the average particle size is about 100 µm. Raw
DAT sample particles in Figure 3(b) are plates and have a rough
surface. The average particle size is about 300 µm. While in
Figure 3(c), the co-crystal micro-particles obtained are
amorphous within range from 50 µm to 100 µm in size
4.5. Impact sensitivity
4
.3. Raman spectroscopy
The impact sensitivity of the involved materials has been
tested by BAM fall hammer method. Each test includes 5
impact energy levels and each level repeated 10 times, from
which the probability will be calculated. The impact curves
obtained for the EDNA/DAT co-crystal and the DAT compound
are shown in Figure 5.
Raman spectroscopy is another useful method for the
characterization of the co-crystal that shows that the vibrational
modes of the co-crystal are different from those of the starting
materials.
Table 1 RAMAN of EDNA, DAT and their cocrystsal:
EDNA
Co-crystal
3326
3247
3008
2970
1668
1549
1400
1315
1145
1112
1027
DAT
3325
3249
3160
1669
1546
1329
1306
1106
1079
792
3240
3008
2972
1447
1405
1317
1142
Figure 4 Raman Spectrum of EDNA/DAT co-crystal
1111
028
1
A full understanding of the effects of the co-crystal formation on
the vibrational modes of motion is obtained by the complete
assignment of the spectra of the starting materials and of the co-
crystal. The Raman spectra of raw EDNA, DAT, and the co-
crystal are shown in Figure 4. While a comparison of the spectra
are presented in Table 1. The results show certain shift in the
band of the co-crystal compared with the coformer which lead
for another confirmation about the formation of the co-crystal.
943
713
697
9
44
792
698
According to the impact data which was calculated at 50%
probability of initiation, the sensitivity of the co-crystal to impact
is 9.7 J which is much lower than the pure DAT (15.4 J). This
result might reflect the effect of EDNA on the sensitivity behavior
of the co-crysral. The impact sensitivity of the co-crystal is
almost similar to the impact sensitivity of the well-known
4.4. Performance results
explosive Hexanitrostilbene (HNS) [16]
.
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Table 2: Explosive characteristics and physical properties of EDNA, DAT and their EDNA/DAT cocrystsal
Det.
Velocity
calculated
Molecular
weight
Heat of
combustion
Heat of
formation
Det.
Impact
sensitivity
Explosive
Density
g.cm-3
Pressure
calculated
GPa
Formula
N %
designation
-
1
kJ.mol-1
kJ.mol-1
(
g.mol )
(J)
m.s-1
DAT
C
1
H
4
N
6
100.1
150.1
1276.6[17]
1540.1[18]
310.4[17]
-104.6[18]
1.57[17]
1.75
7570.0[13]
8422.5
20.7
30.9
15.4
84.0
37.3
EDNA
C
2
H
6
N
4
O
4
8.3[16]
EDNA/DAT
Co-crstal
C
3.88
H
13.63
N
O
15.3 3.9
337.1
2747.6
196.9
1.73
8254.5
26.7
9.7
54.8
Table 3. It was evident from the curves that the thermal behavior
of co-crystal is obviously different from their coformers, and the
differences in thermal stability of these substances further
suggest of the formation of a new crystal.
DAT
100
90
80
70
60
50
40
30
20
10
0
Table 3. Results of non-isothermal DSC data of EDNA, DAT, and the co-
o
-1
crystal at 5 C min heating rate
Endothermic peaks
Exothermic peaks
∆
H
1
∆H
2
Type
o
o
o
o
o
o
e
T
o
/ C
T
p
/ C
T
e
/ C
/
T
i
/ C
T
p
/ C
T
/ C
/
J.g-1
J.g-1
EDNA
DAT
178.3
187.1
180.3
188.8
180.8
190.0
-33 181.0
184.7
241.9
188.0
258.4
1363
0
10
20
30
40
50
60
-257 218.5
1987
1736
Energy [J]
(
a)
EDNA/DAT
Co-crystal
148.6
149.7
150.6
-180 172.8
188.8
213.1
EDNA / DAT Co-crystal
Note: the T
o
, the onset temperature of the peaks; T
p
, the maximum peak
100
Temperature; T
e
, the end temperature for the heat change;∆H
1
, ∆H , the heat
2
90
80
70
60
50
40
30
20
10
0
absorbed, the heat released for the studied sample respectively.
5
7
9
11
13
15
Energy [J]
(b)
EXO
Figure 5: The impact sensitivity curves of a.DAT and b EDNA/DAT co-crystal
4
.6. Thermal analysis of the co-crystal and the
Figure 6: DSC curves for EDNA, DAT and their co-crystal at heating rate of
C min-1
coformer
5
o
For the studied co-crystal, the exothermic peaks at 5 oC.min-1
are well formed; indicating signs of kinetically controlled
decomposition processes. In addition it can be seen that both
the endothermic and exothermic peak are shifted to lower
temperature.
In our study to compare the heat change during the thermal
decomposition of the co-crystal and the coformer, The DSC
curves have been studied under the heating rate of 5.0 C min
as shown in Figure 6. The parameters are summarized in
o
-1
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a
EDNA/DAT co-crystal
b
EDNA
Figure 7 Non-isothermal TG/DTG of the co-crystal of EDNA/DAT and
coformers EDNA, DAT at 1, 2, 3 and 4 oC min heating rate.
-1
c
DAT
ᴏ
The EDNA/DAT co-crystal shows melting at 149.7 C with a
decrease about 30 C comparing with EDNA, which can be
Table 4. Results of non-isothermal TG/DTG of the co-crystal EDNA/DAT
TG curve DTG curve
ᴏ
attributed to effect of the formation of new material. Also, it can
be observed that the enthalpy of the co-crystal for both the
endothermic and exothermic peaks are of average value
between the enthalpies of the coformer. TG/DTG curves of the
EDNA, DAT and EDNA/DAT co-crystal under the heating rates
of 1, 2, 3 and 4 oC.min were recorded. Results of the non-
isothermal measurements of the co-crystal are presented in
table 4 and The TG/DTG curve is shown in Figure .7. It has
shown that the only single decomposition process has been
observed which indicate behavior as single crystal. The
characteristic parameters of the TG and DTG curves of the co-
crystal are summarized on Table 4. It was shown from the onset
temperature of thermal decomposition and initial mass loss
temperature increase with the heating rates
ᵝ
/
Mass
loss
/
T
o
L
max
T
p
T
oe
type
/
C
/
/
C
/
o
-
C min
o
-1
o
o
%.min
C
1
%
1
.0
.0
153.1
154.9
76.68
-2.2
165.7
179.2
190.8
-1
2
81.75
-4.3
-6.76
-8.8
202.1
204.6
208.4
Co-crystal
EDNA/DAT
3.0
4.0
1.0
2.0
3.0
4.0
1.0
2.0
3.0
4.0
163.9
172.9
201.9
211.1
216.4
219.6
177.7
178.0
179.8
181.0
84.29
89.76
88.94
93.62
86.52
80.68
93.18
96.51
97.38
98.32
181.6
186.3
220.4
229.4
243.2
237.0
179.7
181.5
183.7
185.3
-2.98
-5.46
-8.48
238.2
249.8
253.2
257.0
182.6
186.1
190.6
193.6
DAT
4.7. Estimation of the decomposition Kinetics:
-10.47
-21.02
-27.18
-32.30
-38.71
According to the recommendation of International Confederation
of Thermal Analysis and Calorimetry (ICTAC) [19], the
dependence of the activation energy on the degree of
conversion, the modified Kissinger-Akahira-Sunose (KAS)
isoconversional method was used for the studied sample. For
this study, the activation energies at conversion rates from 5 to
90% were determined. However, it is recommended to take the
mean values at α interval from 0.3 to 0.85 due to the increased
of inaccuracy from the tail peak of DTG. The calculated results
are summarized in Table 5.
EDNA
ᵝ, the heating rate; T
maximium mass loss rate, T
onset temperature of the end decomposition
o
, onset temperature of the decomposition; Lmax, the
p
; the peak temperature of mass loss rate; Toe
,
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Table 5 Kinetic parameters of EDNA, DAT and their co-crystal by modified isoconversional KAS method
.
EDNA
Log A
DAT
Log A
EDNA/DAT co-crystal
α reacted
E
a
R2
E
a
R2
E
a
Log A
s
R2
kJ.mol-
1
s
-1
kJ.mol
-1
s
-1
kJ.mol
-1
-1
0.05
581.1
78.7
0.9936
175.7
30.7
0.9625
159.0
30.52
0.9892
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
578.8
517.4
501.3
460.8
431.1
404.4
379.9
357.5
337.6
322.0
284.6
267.8
254.4
257.3
245.6
238.8
78.4
71.2
69.2
64.5
61.0
57.9
55.0
52.4
50.1
48.2
43.8
41.8
40.3
40.6
39.2
38.3
0.9949
0.9989
0.9999
0.9999
0.9996
0.9987
0.9969
0.9956
0.9968
0.9962
0.9819
0.9741
0.9737
0.9893
0.9892
0.9853
170.0
168.7
172.3
161.9
163.5
164.9
166.2
160.2
161.5
152.3
153.3
154.2
155.5
156.5
148.4
149.6
29.8
29.5
29.8
28.6
28.7
28.8
28.8
28.1
28.2
27.2
27.2
27.3
27.4
27.4
26.5
26.6
0.9965
0.9986
0.9978
0.9936
0.9993
0.9993
0.9993
0.9965
0.9965
0.9933
0.9997
0.9933
0.9933
0.9997
0.9982
0.9982
131.8
144.1
136.2
129.4
130.0
131.2
123.8
124.9
126.0
121.3
122.5
123.6
125.3
120.9
123.6
130.8
26.93
28.29
27.23
26.33
26.33
26.41
25.48
25.54
25.62
24.99
25.07
25.14
25.25
24.64
24.82
25.49
0.9859
0.9823
0.9859
0.9858
0.9862
0.9862
0.9843
0.9841
0.9843
0.9804
0.9804
0.9804
0.9804
0.9830
0.9873
0.9620
0.90
229.8
37.2
0.9809
151.4
26.7
0.9983
125.7
24.67
0.861
Mean
value
315.1±19.2
47.4±2.21
157.2±1.7
26.6±0.54
125.3±1.09
26.04±0.17
≠
-1
-1
∆
S /JK mol
685.2
2758.7
2149.6
*
The mean value for the activation energy was taken from the range of α = 0.25 to 0.85 as it is the main decomposition peak of the studied materials
energies from the RMM aplication on the different tetrazole
derivatives move in the range of 158 – 177 kJ mol-1 and
[
21]
corresponding logarithms of preexponents of 13.5-15.4
From comparing of these facts with results in Table 5 the relative
real E values for DAT and EDNA/DAT co-crystal are possible to
.
a
obtain, but preexponents are fairly high. This might be due to the
different applied technique of measurements. Therefore, another
evaluation was obtained on the basis of calculated values of the
activation entropy (see in Table 5). The obtained values
indicating that it corresponds to very low molecular complexity
about this see also [ ) and primary step of decomposition of
22]
(
the coformers and co-crystal should be radical process. The
comparison between the dependence of activation energy of
EDNA, DAT and their co-crystal on the extent of conversion are
also represented in Figure 8. From this relationship we can
evaluate the tendency of the activation energy to be effective or
composite value which help in making reliable kinetic prediction
to have information about the mechanism of the decomposition.
The full decomposition mechanism of the co-crystal will be
discussed in more detail in further work.
Figure 8
:
Dependence of activation energy of EDNA, DAT and their co-
crystal on extent of conversion by isoconversional modified KAS method
For the EDNA thermal decomposition the temperature region of
its melting point. Fig. 6 shows that decomposition reaction
should be very high it is also indication of high values of
Arrhenius parameters. From the literature, decomposition of
EDNA in the solid state (temperature region 393-418 K) was
studied by means of the Russian Manometric Method (RMM)
For the DAT and the co-crystal, the activation energies are not
dependent on temperature. It has different behavior compared
with EDNA.
= 186.2 kJ mol-1 and log A = 18.0 [20]. Activation
with E
a
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.201800041
ARTICLE
3
. Conclusion
Ar laser (λ = 514.5 nm) and a semiconductor laser (λ= 785 nm).
The maximum output power is 1.7 mW of the light spot of the
-1
Crystallization of the 1,4-dinitro-1,4-diazabutane (EDNA) and
,5-diaminotetrazole (DAT) from acetonitrile, in the molar ration
of 1:2, led to new co-crystal which was confirmed by the Powder
XRD. The formed EDNA/DAT co-crystal has promising
Raman spectrometer and the spectral resolution is 1 cm .
1
4.4. Elemental Analysis
a
detonation characteristics, the detonation velocities (D) and the
detonation pressure (P) are 8254.5 m s-1 and 26.7 GPa
respectively. It has good impact sensitivity of 9.7 J which in the
level of 2,2’,4,4’,6,6’-hexanitrostilbene (HNS) and so is lower
compared with the coformer EDNA. The thermal analysis of this
co-crystal and its coformers, lead to high values of Arrhenius
Fisons – EA-1108 CHNS-O elemental analyzer was used for the
determination of C, H, and N in the prepared co-crystal. The
results of the elemental analysis were recalculated to match the
nitrogen content to the individual explosive and reported in Table
1 as a hypothetical formula. By this way, the calculated formula
was used as if it is individual explosive and it was used in the
detonation parameters calculations.
parameters of the EDNA decomposition (E
a
= 315.1 kJ mol-1 and
log A= 47.4; which correspond to the temperature region of the
EDNA melting point). While, the other values of activation
energies are expectational, i.e. E
a
= 157.2 and 125.3 kJ mol-1 for
4.5. Heat of Combustion
DAT and EDNA/DAT respectively. Corresponding activation
entropies show, that coformers and co-crystal should
decompose by radical primary mechanism. This co-crystal
possesses a promising future for expanding the reuse of EDNA,
it might be used in ammunition because of overcoming the
acidity problem. In addition, the higher nitrogen content and
acceptable sensitivity to external stimuli.
An automatic high pressure Bomb calorimeter, model BCA 500,
OZM research s.r.o, Czech republic, was used to measure the
heat of combustion of the co-crystal. The co-crystal was placed
[25]
in a closed bomb filled with an excess of oxygen
and ignited.
The output data was used for calculation of the enthalpy of
formation Table 1 of the co-crystal that was used for determining
the detonation characteristics.
4.6. Calculation of the detonation properties
4. Experimental work
The theoretical detonation characteristics (detonation velocity, D,
heat of detonation, Q, and detonation pressure, P) of the Co-
4.1. Materials and preparation of the co-crystal
crystal, as well as those of the individual explosives, were
calculated by the EXPLO5 code version 5.04 [26]. The following
Becker-Kistiakowsky-Wilson equation of state (BKW EOS) was
used with BKWN set of parameters α = 0.5, β = 0.176, κ = 14.71,
Θ = 6620 [26]. The detonation heat is the heat released in a
constant volume explosion and is determined by subtracting the
heats of formation of the explosive (reactants) from the sum of
the heats of formation of the detonation products. The
theoretical calculation and the error between the experimental
results are listed on Table 1
EDNA was prepared according to reference [23], DAT was
obtained by a reaction of thiosemicarbazide, sodium azide, and
lead oxide in dimethylformamide according to ref. [24]. Acetonitrile
were purchased from Penta Reagent Factory, Czech Republic.
The co-crystal was carried out by dissolving EDNA and DAT in
molar ratio of 1:2 in Acetonitrile at 45 ᴏC for 2 hours with
constant stirring. After complete dissolving of the coformers.
Ethanol was used as antislovent and used for precipitation at the
same temperature. After that, the mixture of precipitate will be
stirred for another hour during cooling and after the temperature
decrease d to normal temperature, filterating the new fine
slightly yellow cocrystal and dried.
4.7. Sensitivity to impact
The standard impact tester with exchangeable drop weight of
4
.2. powder X-ray diffraction (PXRD)
[27]
BAM impact sensitivity instrument
was used ; the amount of
3
substance tested was 50 mm , and drop hammers of 2 and 5
Kg weight were used. The probability analysis was used to
determine the probability levels of the initiation. Only the 50%
probability of initiation (H50) is used in this article and is reported
in Table 1.
The powder X-ray diffraction (PXRD) patterns were recorded to
identify EDNA, DAT and the prepared co-crystal sample by sixth
generation MiniFlex X-ray diffractometer (XRD), (Cu Kβ, λ=
0.15406 nm, 40 kV, 15 mA, Miniflex, Rigaku, Japan). Images
were integrated from 2 to 50 with a 0.05 step size using PDXL
full-function powder diffraction analysis software suite.
4.8. Thermal analysis
4.3.
SEM and Raman spectroscopy
The co-crystal and the coformer were studied with regard to the
kinetics of thermal decomposition, using different heating rate
The crystal morphology of the prepared co-crystal and the
coformer were studied by scanning electron microscope (SEM)
JSM-5500LV, JEOL, Japan. While, Raman spectra were
measured with Nicolet Is50Raman, Thermo scientific, using an
TG (Netzsch 209F3 instrument, Al
heating rate of 1, 2, 3 and 4 C.min (with data collecting rate of
2
O
3
crucible) and under a
o
-1
4
3
0 points per Kelvin). The test temperature range for TG was
0–350 ᴏC, with the sample mass of about 2.0 mg under
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Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.201800041
ARTICLE
3
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properties were also evaluated by the technique of DSC
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