Studies on 3,3′-diamino-4,4′-azofurazan (DAAF): Specific heat capacity, enthalpy of formation and detonation properties

Article abstract of DOI:10.1007/s10973-017-6160-4

The specific heat capacity of 3,3′-diamino-4,4′-azofurazan (DAAF) was determined by a differential scanning calorimetry. In the temperature range of 253–373?K, the specific heat capacity (C_p) versus T relationship can be fitted into a linear equation: C_p (J?g^?1?K^?1)?=?0.0028T?+?0.26456. The standard molar heat capacity is 215.53?J?mol^?1?K^?1 at 298.15?K. According to the relationship between the specific heat capacity and thermodynamic functions, enthalpy, entropy, Gibbs free energy increments [H_T–H_298.15], [S_T–S_298.15] and [G_T–G_298.15] of DAAF from 253 to 373?K with temperature interval of 10?K, relative to the standard temperature 298.15?K were calculated. The combustion energy of DAAF was measured by a precise IKA C5000 oxygen-bomb calorimeter to be Δ_cU?=??(13188.43?±?32.77) J?g^?1. The standard molar enthalpy of combustion at 298.15?K was determined to be Δ_cH_m ^θ?=??(2575.68?±?6.42) kJ?mol^?1. The standard molar enthalpy of formation was calculated to be Δ_fH_m ^θ?=?429.98?±?6.44?kJ?mol^?1 in accordance with Hess’s law. The detonation velocity and detonation pressure were calculated as 7.31?km?s^?1 and 23.61?GPa using the Kamlet–Jacobs equations according to the experimental enthalpy of formation.

Full text of DOI:10.1007/s10973-017-6160-4

J Therm Anal Calorim
DOI 10.1007/s10973-017-6160-4
Studies on 3,30-diamino-4,40-azofurazan (DAAF)
Specific heat capacity, enthalpy of formation and detonation properties
Naizhen He1 Yong Zhang2 Ruqin Liu1 Rong Guo1 Zhirong Suo1
•
•
•
•
Received: 25 June 2016 / Accepted: 6 February 2017
´
´
Ó Akademiai Kiado, Budapest, Hungary 2017
Abstract The specific heat capacity of 3,30-diamino-4,40-
azofurazan (DAAF) was determined by a differential
scanning calorimetry. In the temperature range of
253–373 K, the specific heat capacity (Cp) versus T rela-
tionship can be fitted into a linear equation: Cp (J g-1 K-1) =
0.0028T ? 0.26456. The standard molar heat capacity is
215.53 J mol-1 K-1 at 298.15 K. According to the relation-
ship between the specific heat capacity and thermodynamic
functions, enthalpy, entropy, Gibbs free energy increments
[HT–H298.15], [ST–S298.15] and [GT–G298.15] of DAAF from
253 to 373 K with temperature interval of 10 K, relative to
the standard temperature 298.15 K were calculated. The
combustion energy of DAAF was measured by a precise
IKA C5000 oxygen-bomb calorimeter to be DcU =
-(13188.43 32.77) J g-1. The standard molar enthalpy
Introduction
Azofurazan compounds are very important class of fur-
azan-based energetic materials [1–4]. 3,30-Diamino-4,40-
azofurazan (molecular structure: Fig. 1; formula:
C4H4N8O2; DAAF) is a novel high nitrogen content high
energy material (HNC-HEM) with high energy density and
low sensitivity [5]. In many respects, DAAF is insensitive
to drop impact but with a small critical diameter, friction
and resistance to spark [6]. Some explosive and propellant
formulations containing DAAF have also been designed,
and it has found that the addition of DAAF can evidently
decrease the sensitivity of the explosive formulations [7] or
improve the specific impulse of solid propellants [8].
DAAF can be widely used as an energetic additive to
modify the properties of solid rocket propellants and
explosive formulations from the above-mentioned high
performances [9, 10].
of combustion at 298.15 K was determined to be DcHmh
=
-(2575.68 6.42) kJ mol-1. The standard molar enthalpy
of formation was calculated to be DfHhm = 429.98
6.44 kJ mol-1 in accordance with Hess’s law. The deto-
nation velocity and detonation pressure were calculated as
7.31 km s-1 and 23.61 GPa using the Kamlet–Jacobs equa-
tions according to the experimental enthalpy of formation.
Specific heat capacity, standard molar enthalpy of
combustion and standard molar enthalpy of formation are
some of the most fundamental thermodynamic properties,
closely related to other physical and chemical properties
[11, 12]. The standard molar enthalpy of formation of a
substance is the important data that is used when calcu-
lating enthalpy changes, equilibrium constants and theo-
retical yields of reactions for which the substance is
involved. Since DAAF was firstly synthesized by Russian
scientists in 1981 [13], some works have been focused on
the properties of DAAF, including thermal stability [14],
thermal decomposition [15], sensitivity [16] and so on.
However, the specific heat capacity and thermodynamic
properties of DAAF have not been published in the liter-
ature at all. Thus, in the present work, we studied its
specific heat capacity by differential scanning calorimetry
and calculated the thermodynamic functions. The
Keywords Differential scanning calorimeter Á
3,30-Diamino-4,40-azofurazan Á Specific heat capacity Á
Thermodynamic properties Á Standard molar enthalpy of
formation
& Zhirong Suo
suozhirong@hotmail.com; suozhirong@163.com
1
Analytical and Testing Center, Southwest University of
Science and Technology, Mianyang 621010, China
2
Institute of Chemical Materials, CAEP, Mianyang 621900,
China
123

N. He et al.
The HPLC analysis was carried out with HPLC system
(Dionex UltiMate3000, Thermo Scientific) equipped with
Hypersil GOLD column (250 mm 9 4.6 mm, 5.0 lm), an
UV detector at 236 nm wave length, and the mobile phase
was acetonitrile/water (40/60, volume) with a flow rate of
0.8 mL min-1. The purity of DAAF was 99.37% according
to the HPLC. These results confirmed the reliability of the
sample used in these studies.
O
O
N
N
N
N
H2N
N
N
NH
2
Fig. 1 Molecular structure of DAAF
combustion energy at 298.15 K was determined by the
oxygen-bomb-type combustion calorimeter, and the stan-
dard molar enthalpy of formation at 298.15 K was
obtained. The detonation velocity and detonation pressure
were calculated using the Kamlet–Jacobs equations. These
thermodynamic basic data obtained are available for
exploiting new synthesis method, engineering design and
industry production of DAAF.
Determination of specific heat capacity
The differential scanning calorimetry (DSC Q2000, TA,
American) was utilized to perform the specific heat
capacity measurement in the temperature range of 253–
373 K at the heating rate of 10 K min-1 with flow rate
of 50 mL min-1. Synthetic sapphire (NIST Standard
reference material No. 720) was used as the reference
material. The reference mass for sapphire was 23.25 mg.
The specimen mass for DAAF was 11.52 mg. All the
experiments were performed using sealed aluminum
cells. The calorimeter was calibrated in temperature and
heat flow by indium and sapphire. The temperature was
increased at a rate of 10 K min-1 from 253 to 373 K
with isotherm at 253 and 373 K for 5 min. The specific
heat capacity of the specimen can be calculated
according to Eq. (1):
Experimental
Synthesis and characterization of DAAF
The 3,4-diaminofurazan (DAF, 3 g) and ethyl acetate
(100 mL) were mixed in a 250-mL round-bottomed flask at
room temperature. The solution was stirred and heated to
65 °C, and then potassium permanganate (3 g) was added
in three divided times. Dropped hydrochloric acid (15 mL)
to solution within 40 min after the mixture was stirred for
20 min. After stirring for 3 h, a orange solid precipitated
from the solution. Three-step operation, respectively, was
selected to purify DAAF: Firstly, the crude DAAF was
dissolved in the minimum amount 80 °C dimethyl
sulphoxide and separated out the DAAF crystals with
adding water by solvent–nonsolvent precipitation tech-
nique. Secondly, the DAAF crystals were recrystallized
through tetrahydrofuran. Thirdly, the DAAF crystals were
added to distilled water and boiled for ten minutes to
eliminate soluble impurities and filtered. The product was
air-dried to get pure DAAF.
Ds  mst
Cps ¼ Cpst
ð1Þ
Dst  ms
where Cp is the specific heat capacity, D is the heat flow
difference between the sample (sapphire) and the empty
aluminum crucible, and m is the mass. Subscript s indicates
specimen, and st indicates the standard material sapphire.
The heat flow differences were obtained by subtracting the
baseline heat flow from the heat flow of the sapphire and
the sample.
Calorimetric experiments
The structure of DAAF was verified by Fourier trans-
form infrared spectroscopy (380 FT-IR, Thermo Fisher
Nicolet), nuclear magnetic resonance spectroscopy
(600 MHz, Bruker Corporation) and mass spectrometry
(1200 MS, Varian). The IR (KBr matrix, t) of DAAF
showed characteristic absorption peaks at 3448, 3337,
1628, 1495, 1289, 1039 cm-1. The 1H NMR and 13C NMR
absorption peaks of DAAF were detected at d = 6.91 ppm
(s, 4H, 2NH2), d = 151.13 ppm (s, –C–NH2),
d = 156.23 ppm (s, –C–N). m/z 195.1 [M-H]-, 165.1 [M-
NO]- ions were obtained in the negative mode.
The combustion energy of DAAF was obtained by a pre-
cise IKA C5000 oxygen-bomb combustion calorimeter
conducted in Northwest University. The experimental
procedure and methods can be found in the literature [17].
The calorimeter was calibrated with the standard substance
benzoic acid having a purity of 99.99%, and each sample
was tested with 7 times. The mean value -(26,496 35)
J g-1 is very close to the standard value as -(26,434 3)
J g-1 (T = 298.15 K) [18], indicating that the measuring
system is accurate and reliable.
123

Studies on 3,30-diamino-4,40-azofurazan (DAAF)
Results and discussion
Specific heat capacity
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
In order to obtain precise measurements, good baseline
stability should be guaranteed. The baseline signal was
obtained by heating two empty aluminum crucibles from
253 to 373 K. The results showed that the deviation of heat
flow of the system for three parallel times was within 0.1
mW. The method can provide good results only when there
are no negative effects during DSC experiments and
especially baseline should be very stable. The specific heat
capacities were measured three times, and the average
values are given in Table 1.
260
280
300
320
340
360
380
Temperature/K
Fig. 2 Relationships of Cp versus T for DAAF
functions [HT–H298.15], [ST–S298.15] and [GT–G298.15] of the
DAAF were calculated from the heat capacity in the tem-
perature range from 253 to 373 K with temperature interval
of 10 K. The thermodynamic functions calculated from
Eqs. (2-4) are listed in Table 2.
The values of specific heat capacity can be fitted, and
equation was obtained by using the experimental heat
capacity (Cp) and the experimental temperature
(T) (Fig. 2). In the temperature range of 253–373 K, the
specific heat capacity presents a good linear relationship
with temperature. The specific heat capacity equation is: Cp
(J g-1 K-1) = 0.0028T ? 0.26456. The determination
coefficient of fitting is 0.9992. The standard molar heat
capacity of DAAF is 215.53 J mol-1 K-1 at 298.15 K.
Combustion energy, standard molar enthalpy
of combustion and standard molar enthalpy
of formation
The calculated results of the combustion energy for
DAAF from the seven combustion tests are indicated in
Table 3. The average DcU was determined to be
Thermodynamic properties
-(13,188.43 32.77) J g-1
.
In terms of the polynomial of heat capacity and the ther-
modynamic relationship as Eqs. (2–4), the thermodynamic
The enthalpy of combustion for DAAF was calculated
by following Eq. (5) at 298.15 K:
Z
T
C4H4N8O2ðsÞ þ 4O2ðgÞ ! 4CO2ðgÞ þ 2H2OðlÞ þ 4N2ðgÞ
ð5Þ
The standard molar combustion energy of DAAF can be
changed into standard molar enthalpy of combustion
through the following reaction formula (6) at
T = 298.15 K.
HT À H298:15
¼
Z
Cp dT
ð2Þ
ð3Þ
ð4Þ
298:15
T
Cp
ST À S298:15
¼
dT
T
298:15
Z
Z
T
T
Cp
T
GT À G298:15
¼
CpdT À T
dT
298:15
298:15
Table 1 Experimental specific heat capacities of DAAF interval 10 K
Temperature/K
Blank heat flow/mW
Reference heat flow/mW
DAAF heat flow/mW
Cp (sapphire)/J g-1 k-1
Cp (DAAF)/J g-1 k-1
260
270
280
290
300
310
320
330
340
350
360
370
0.0469
0.1318
0.1697
0.1993
0.2291
0.2594
0.2877
0.3152
0.3447
0.3739
0.4027
0.4341
-2.381
-2.442
-2.512
-2.578
-2.635
-2.690
-2.737
-2.782
-2.820
-2.850
-2.876
-2.898
-1.689
-1.699
-1.725
-1.757
-1.787
-1.814
-1.841
-1.866
-1.889
-1.905
-1.920
-1.936
0.6846
0.7102
0.7344
0.7574
0.7792
0.7999
0.8194
0.8380
0.8556
0.8721
0.8878
0.9027
0.9879
1.0196
1.0472
1.0768
1.1070
1.1349
1.1639
1.1911
1.2188
1.2442
1.2694
1.2959
123

N. He et al.
Table 2 Thermodynamic functions of DAAF
T/K
HT–H298.15/kJ mol-1
ST–S298.15/J mol-1 K-1
GT–G298.15/kJ mol-1
260
270
280
290
300
310
320
330
340
350
360
370
-7.8211
-5.8482
-3.8205
-1.7379
0.3996
-28.0363
-20.5913
-13.2175
-5.90989
1.33603
8.52431
15.6586
22.7422
29.7782
36.7693
43.7181
50.6268
-0.5317
-0.2886
-0.1196
-0.0241
-0.0012
-0.0506
-0.1715
-0.3636
-0.6262
-0.959
2.5920
4.8392
7.1414
9.4984
11.9103
14.3770
16.8987
-1.3614
-1.8332
Table 3 Experimental results of energy of combustion for DAAF
No
Mass of sample
W/g
Corrected temperature rise
DcT/K
Combustion energy of sample
-DcU/J g-1
1
0.18029
0.18036
0.18106
0.17966
0.18025
0.18031
0.18000
0.2271
0.2295
0.2312
0.2290
0.2288
0.2283
0.2260
13100
2
13240
3
13291
4
13261
5
13206
6
13167
7
13054
Mean
u
13188.43 32.77
W, mass of sample; DcT, temperature increment; DcU, energy of combustion; the uncertainty quoted for u corresponds to the standard deviation
of seven independent experiments
DcHmh ðDAAF; s; 298:15 KÞ ¼ DcUmh ðDAAF; s; 298:15 KÞ
In Eq. (8), the standard molar enthalpies of formation of
CO2 (g) and H2O (l), DfHhm (CO2, g, 298.15 K) =
þ Dn Á RT
ð6Þ
ð7Þ
-(393.51 0.13) kJ mol-1 and DfHmh (H2O, l,
298.15 K) = -(285.83 0.042) kJ mol-1 were employed
in the calculation of DfHhm (DAAF, s). Finally, the standard
molar enthalpy of formation of the DAAF was 429.98
X
X
Dn ¼
niðproducts; gÞ À
niðreactants; gÞ
P
where
ni is the total amount (in moles) of the gases
present as products or as reactants. R = 8.314 J mol-1 K-1
,
6.44 kJ mol-1
.
T = 298.15 K. The calculated standard molar enthalpy
combustion DcHhm of DAAF is -(2575.68 6.42) kJ mol-1
.
The standard molar enthalpy of formation DfHhm was
calculated by a Hess law according to the following ther-
mochemical Eq. (8):
Explosion properties
Detonation velocity (D) and detonation pressure (P) are the
most important characteristics of energetic materials. Cal-
culation of D, P is performed using M, q, of C–H–N–O
explosives (CaHbNcOd) and DfHhm of DAAF. By substitu-
tion, the values of a, b, c and d in CaHbNcOd = C4H4N8O2,
DfHmh ðDAAF; sÞ ¼ 4DfHmh ðCO2; gÞ þ 2DfHmh ðH2O; lÞ
À DcHmh ðDAAF; sÞ
ð8Þ
123

Studies on 3,30-diamino-4,40-azofurazan (DAAF)
Table 4 Performance comparison between DAAF and TNT
Sample
Melting/
°C
Density/
g cm-3
Nitrogen content/% Oxygen balance/% Impact sensitivity/cm Pressure/
GPa
Velocity/
km s-1
TNT [20] 81.8
DAAF 315
1.650
18.50
57.13
-73.96
-65.31
170
19.50
23.61
6.88
7.31
1.728 [6]
320 [7]
M = 196.05 g/mol,
q = 1.728 g cm-3
,
DfHhm
=
capacity is 215.53 J mol-1 K-1 at 298.15 K. The enthalpy
change, entropy change and Gibbs free energy change of
DAAF were derived in the temperature range from 253 to
373 K with temperature interval of 10 K. The combustion
energy of DAAF was measured with an oxygen-bomb
calorimeter. The combustion energy (DcU), standard molar
enthalpy of combustion (DcHhm) and standard molar
enthalpy of formation (DfHhm) at 298.15 K are -(13,188.43
32.77) J g-1, -(2575.68 6.42) kJ mol-1 and 429.98
6.44 kJ mol-1, respectively. The detonation velocity and
detonation pressure are 7.31 km s-1 and 23.61 GPa.
429.98 kJ mol-1 into Kamlet–Jacobs Eqs. (9–13) [19].
b þ 2c þ 2d
N ¼
ð9Þ
48a þ 4b þ 56c þ 64d
56c þ 88d À 8b
Mg ¼
ð10Þ
ð11Þ
b þ 2c þ 2d
28:9b þ 47:02ðd À b=2Þ þ 0:239DfHmh
Qd ¼
 103
M
ꢀ
ꢁ
D ¼ 1:01 NM1=2Q1d=2 1=2ð1 þ 1:30qÞ
P ¼ 1:558NM1=2Qd1=2q2
ð12Þ
ð13Þ
Acknowledgements Thanks are due to Prof. H. X. Ma, School of
Chemical Engineering, Northwest University, Xi’an 710069, P.
R. China, for their help with combustion calorimetric measurement.
This work was supported by Defence Science and Technology Project
(ProjectJSJL2015212A001).
where P is the detonation pressure (GPa), D is the deto-
nation velocity (km s-1), N is the moles of gaseous deto-
nation products per gram explosive (mol/g), Mg is average
mass of gaseous products (g/mol), and Qd is chemical
energy of detonation (cal/g). The values of D and P are
7.31 km s-1, 23.61 GPa, respectively.
References
In evaluating new energetic materials, they are generally
compared to the most important energetic materials such as
trinitrotoluene (TNT). The properties of TNT and DAAF
are given in Table 4. Compared with the traditional ener-
getic explosives, the introduction of azo into furazan
compound has resulted in a boost in their performance.
DAAF derives a significant amount of energy of detonation
from intrinsically high positive heats of formation, good
thermal stability, high nitrogen content and enough avail-
able oxygen to burn its hydrogen to water. This high
nitrogen material can show remarkable insensitivity toward
electrostatic discharge, friction and impact. Generation of
nitrogen gas as decomposition product of explosive for-
mulation is desired in order to avoid environmental pol-
lution, and DAAF is an environmentally compatible green
energetic materials.
1. Wang LX, Tuo XL, Yi CH, Zou HT, Xu J, Xu WL. Theoretical
study on the trans-cis isomerization and initial decomposition of
energetic azofurazan and azoxyfurazan. J Mol Graph Model.
2009;28:81–7.
2. Martinez H, Zheng Z, Dolbier WR. Energetic materials con-
taining fluorine. Design, synthesis and testing of furazan-con-
taining energetic materials bearing a pentafluorosulfanyl group.
J Fluor Chem. 2012;143:112–22.
3. Zhang J, Shreeve JM. Nitroaminofurazans with azo and azoxy
linkages: a comparative study of structural, electronic, physico-
chemical, and energetic properties. J Phys Chem C. 2015;119:
12887–95.
4. Qiu LL, Li YL, Wang Z, Xue M, Xu ZB, Meng ZH, Ma XQ, Yi
D, Lin ZH. Investigation of the solubility of 3,4-diaminofurazan
(DAF) and 3,30-diamino-4,40-azoxyfurazan (DAAF) at tempera-
tures between 293.15 K and 313.15 K. Propellants Explos Pyr-
otech. 2016;41:883–7.
5. Sivabalan R, Talawar MB, Santhosh P, Senthilkumar N, Kavitha
B, Gore GM, Venugopalan S. Electro-analysis of energetic
materials. J Hazard Mater. 2007;14:8573–82.
6. Chavez D, Hill L, Hiskey M, Kinkead S. Preparation and prop-
erties of azo- and azoxy-furazans. J Energ Mater. 2006;18:
219–36.
7. Hiskey MA, Chavez DE, Bishop RL, Kramer JF, Kinkead SA.
Preparation of 3,3-diamino-4,4-azofurazan. US Patent, US655
2201, 2003.
Conclusions
Relationship between the specific heat capacity of DAAF
and temperature was accomplished with differential scan-
ning calorimetry (DSC). The specific heat capacity equa-
tion of DAAF is Cp (J g-1 K-1) = 0.0028T ? 0.26456
(253 K \ T \ 373 K), and the standard molar heat
8. Alain C, Bernard F. Propellants with a high specific impulse,
comprising furazan derivatives. US Patent, US5747729, 1998.
9. Hiskey MA, Chavez DE, Bishop RL, Kramer JF, Kinkead SA.
Use of 3,30-diamino-4,40-azoxyfurazan and 3,30-diamino-4,40-
azofur azan as insensitive high explosive materials. US Patent,
US6358339. 2002.
123

N. He et al.
10. Ghule VD, Radhakrishnan S, Jadhav PM, Tewari SP. Quantum
chemical studies on energetic azo-bridged azoles. J Energ Mater.
2013;31:35–48.
16. Chavez DE, Hill L, Hiskey MA, et al. Preparation and explosive
properties of azo and azoxyfurazans.
2000;18:219–36.
J
Energ Mater.
11. Di YY, Yang WW, Kong YX, Shi Q, Tan ZC. Low-temperature
heat capacities and standard molar enthalpy of formation of L-3-
(3,4-dihydroxyphenyl) alanine (C9H11NO4). J Chem Eng Data.
2008;53:900–4.
12. Li X, Jiang JH, Gu HW, Xiao SX, Li CH, Ye LJ, Li X, Li QG, Xu
F. Calorimetric determination of the standard molar enthalpies of
formation of o-vanillin and trimethoprim. J Therm Anal Calorim.
2015;119:721–6.
13. Solodyuk GD, Boldyrev MD, Gidaspov BV, Nikolaev VD.
Oxidation of 3,4-diaminofurazan by peroxide reagents. Zh Org
Khim. 1981;17:861–5.
14. Depiero S, Koerner J, Maienschein J, Weese R. Small-scale safety
and thermal characterization of 3,30-diamino-4,40-azoxyfurazan.
LLNL Explosives Reference Guide. UCRL-TR-231649, 2007.
15. Wang LX, Tuo XL, Zou HT, Yi CH, Wang XG. Ab initio study
of the molecular structure and thermal cis-trans isomerization of
3,30-diamino-4,40-azofurazan and 3,30-diamino-4,40-azoxyfu-
razan. J Theor Comput Chem. 2009;8:507–17.
17. Dong JX, Li Q, Tan ZC. The standard molar enthalpy of for-
mation, molar heat capacities, and thermal stability of anhydrous
caffeine. J Chem Thermodyn. 2007;39:108–14.
18. Certificate of analysis standard reference material 39j -benzoic
acid calorimetric standard. 2007.
19. Hu RZ, Zhao FQ, Gao HX, Yao EG. Estimation of detonation
performances of explosives using M, q, m, Cp, DfHhm, Tig or b of
C–H–O–N explosives and DfHmh of detonation products. Chin J
Expl Propellants. 2013;36:20–3.
20. Thottempudi V, Gao H, Shreeve JM. Trinitromethyl-substituted
5-nitro- or 3-azo-1,2,4-triazoles: synthesis, characterization, and
energetic properties. J Am Chem Soc. 2011;133:6464–71.
123