Preparation, characterization and catalytic effects of copper oxalate nanocrystals

Article abstract of DOI:10.1016/j.jallcom.2011.10.100

Recent work has described the preparation and characterization of copper oxalate nanocrystals (CONs). It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and electron diffraction pattern (ED). The catalytic activity of CONs on the thermal decomposition of ammonium perchlorate (AP) and composite solid propellants (CSPs) has been done by thermogravimetry (TG), differential scanning calorimetry (DSC) and ignition delay measurements. Burning rate of CSPs was also found to be enhanced in presence of copper oxalate nanocrystals. Kinetics of thermal decomposition of AP with and without CONs has also been investigated. The model free (isoconversional) and model-fitting kinetic approaches have been applied to data for isothermal TG decomposition.

Full text of DOI:10.1016/j.jallcom.2011.10.100

Journal of Alloys and Compounds 513 (2012) 499–505
Contents lists available at SciVerse ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Preparation, characterization and catalytic effects of copper oxalate
ଝ
nanocrystals
∗
Gurdip Singh , Inder Pal Singh Kapoor, Reena Dubey, Pratibha Srivastava
Department of Chemistry, DDU Gorakhpur University, Gorakhpur 273009, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 June 2011
Received in revised form 22 October 2011
Accepted 29 October 2011
Available online 7 November 2011
Recent work has described the preparation and characterization of copper oxalate nanocrystals (CONs). It
was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron
microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and electron diffraction
pattern (ED). The catalytic activity of CONs on the thermal decomposition of ammonium perchlorate (AP)
and composite solid propellants (CSPs) has been done by thermogravimetry (TG), differential scanning
calorimetry (DSC) and ignition delay measurements. Burning rate of CSPs was also found to be enhanced
in presence of copper oxalate nanocrystals. Kinetics of thermal decomposition of AP with and without
CONs has also been investigated. The model free (isoconversional) and model-fitting kinetic approaches
have been applied to data for isothermal TG decomposition.
Keywords:
Copper oxalate nanocrystals
Ammonium perchlorate
Composite solid propellants
Burning rate
© 2011 Elsevier B.V. All rights reserved.
Kinetics
1
. Introduction
Composite solid propellants (CSPs) are the major source of
promise to revolutionize technologies of the future [15–18]. Metal
oxalates are interesting candidates for nanostructured synthesis
because these can be transformed to oxide or metals without los-
ing the ordered structure [19]. A lot of works on the structure,
properties and thermal behavior of metal oxalates are present in
the literature [20]. Available evidence suggest that the oxalates of
chemical energy in space vehicles and missiles [1]. Ammonium
perchlorate (AP) is one of the most common energetic material
and oxidizer in CSPs. The thermal decomposition of AP plays a
significant role in the burning behavior of propellants [2–4]. The
characteristics of the thermal decomposition of AP are believed
to influence the performance of CSPs and remarkably sensitive to
additives [5–8]. The ballistics of CSPs can be improved by adding
a catalyst such as Fe O , CuO, Cr O , and NiO; which acceler-
−
−
divalent transition metals are polymeric, with oxalate ion (C O4
)
2
acting as a quadridentate bridging ligand and most such oxalates
are isomorphous. The thermal decomposition of copper oxalate dif-
fers substantially from that of the other transition metal oxalates
[21].
2
3
2
3
ates the rate of decomposition of AP [9–11]. Recent investigations
have shown that nanoparticles of transition metal [12] and fer-
rites [13,14] can catalyze the burning rate of CSPs. The thermal
decomposition and combustion of CSPs are very complex, it is rea-
sonable to wonder if adding another drop to the voluminous bucket
of literature could possibly make any difference.
Nanocrystalline metal oxides, which represent the most diverse
class of materials because of their unique structural, physical and
chemical characteristics, are suitable for a variety of applications
such as catalysts/photocatalysts, hydrogen storage materials, semi-
conductors, sensors, MRI contrast agents, and biomaterials. They
have attracted tremendous attention because of their definite
The goal of the study is to prepare, characterize copper oxalate
nanocrystals (CONs) and investigate its catalytic effect on the ther-
mal decomposition of AP, CSPs and burning rate of CSPs.
2
.
Experimental procedure
2.1. Materials
AP obtained from CECRI, Karaikudi; Cu(NO3)2·2H2O (Merck), oxalic acid (Merck),
HTPB (VSSC, Thiruvanthapuram), IPDI (Merck) and DOA (Merck) were used as
received without further purification.
2
.2. Preparation of copper oxalate nanocrystals (CONs)
In a typical procedure, 0.04 mol/L solutions of Cu(NO3)2·2H2O (0.892 g) and
oxalic acid (0.36 g) in 100 mL acetone were mixed together to obtain a colloidal
suspension of CONs. The suspension was kept under permanent stirring and the
ଝ
Part 78.
∗
◦
Corresponding author. Tel.: +91 551 2200745 (R/H)/2202856 (O);
temperature was regulated to 40 C. The suspension was vacuum filtered, dried at
◦
◦
fax: +91 551 2340459.
80 C for 12 h then washed with ethanol, finally filtered and dried again at 80 C for
12 h [22] to get CuC2O4 nanocrystals.
E-mail address: gsingh4us@yahoo.com (G. Singh).
0
925-8388/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2011.10.100

5
00
G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
3.2.1. Simultaneous TG-DSC
TG-DSC thermogram (Fig. 3) on pure AP and AP with CONs (by
mixing in ratio of 99:1) were recorded on the samples (∼12 mg)
using Perkin Elmer (Pyris Diamond) in the temperature range of
◦
room temperature to 600 C under nitrogen atmosphere (flow rate
2
◦
−1
00 mL/min) at a heating rate of 10 C min in an open alumina
pan.
3.2.2. Non-isothermal TG in static air
Non-isothermal TG studies on AP and HTPB-AP (CSPs) with
and without nanocrystals (wt ∼ 20 mg) were undertaken in static
◦
−1
air at the heating rate of 10 C min using an indigenously fab-
ricated TG apparatus [26]. A round bottom gold crucible was
used as the sample holder. The percentage mass loss has been
◦
plotted against temperature ( C) and the curves are shown
in Fig. 4.
Fig. 1. XRD pattern of CuC2O4 nanocrystals.
3.2.3. Isothermal TG
The isothermal TG of AP with and without CONs (wt ∼ 20 mg)
was taken in static air using the above said TG apparatus at appro-
priate temperatures (Fig. 5).
2.3. Characterizations
XRD (Fig. 1) measurements were performed on a Bruker AXSD8 advance X-
ray diffractometer using Cu K␣ (ꢀ = 1.5418 A˚ ) radiation. The size and morphology
3.2.4. Kinetic analysis of isothermal TG data
of the sample was observed by field emission scanning electron microscope (FE-
SEM) (Fig. 2a) and JEOL JEM transmission electron microscope (TEM) (Fig. 2b), high
resolution transmission electron microscope (HR-TEM) (Fig. 2c) and selected area
diffraction (SAED) pattern (Fig. 2d and e).
Kinetic analysis of thermal decomposition of AP is usually based
on a single-step kinetic equation (1) [27]
d˛
=
k(T)f (˛)
(1)
dt
2
.4. Preparation of CSPs
where t is the time, T is the temperature, ˛ is the extent of con-
version (0 < ˛ < 1), k(T) is the rate constant, and f(˛) is the reaction
model [27], which describes the dependence of the reaction rate
on the extent of reactions. The value of ˛ is experimentally derived
from the global mass loss in TG experiments. The reaction model
may take various forms. The temperature dependence of k(T) can
be satisfactorily described by the Arrhenius equation, when substi-
tution into Eq. (1) yields
CSPs samples were prepared by dry mixing [23] of AP [100–200 mesh] with
CONs (1% by wt) followed by addition of hydroxyl terminated polybutadiene
HTPB). The ratio of AP:HTPB was taken as 3:1. The binder part includes the cur-
(
ing agent isophoron diisocynate (IPDI), in equivalent ratio to HTPB, and plasticizer
dioctyl adipate (DOA), 30% to HTPB. During mixing of the solid components with
HTPB, temperature was maintained at 60 C for 1 h. The propellants were prepared
with and without nanocrystals, casted into aluminum plates having dimensions
1
◦
cm × 3 cm × 10 cm. The samples were cured in an incubator at 70 ◦C for 8–10 days
[11].
ꢀ
ꢁ
d˛
dt
E
=
A exp
−
· f (a)
(2)
RT
3
. Catalytic activity
where A is pre exponential factor, E activation energy and R the gas
constant.
3.1. Burning rate measurements
3
.2.4.1. Model
fitting
Eq.
method. Rearrangement
for isothermal
and
conditions
The burning rate of CSPs was measured in the manner reported
integration
gives
of
(1)
earlier [11,24,25]. The propellant strands were inhibited by apply-
ing PVC tape to check the side burning. The strands were held
vertically and ignited electrically with the help of a nichrome wire
at the top. The time required for a certain length of burning of the
strand was recorded by a stop watch. The burning rate has been
calculated by taking l/t, where l is length of propellant strand (cm)
and t the time (s) of burning. An average of 3 measurements was
taken within experimental error and results are reported in Table 1.
g (a) = k (T)t
(3)
j
j
ꢂ
˛
−1
where g(˛) =
[f (˛)] d˛ is the integrated form of the reac-
0
tion model. The subscript j has been introduced to emphasize
that substituting a particular reaction model in Eq. (3) results
in evaluating the corresponding rate constant, which is deter-
mined from the slope of a plot of g (˛) verses t. For each
j
reaction model selected, the rate constants are evaluated at
several temperatures Ti and Arrhenius parameters are deter-
mined using the Arrhenius equation (4) in its logarithmic
form
3
.2. Thermal decomposition
Thermal decomposition was investigated as follows.
Ej
ln k (T ) = ln A −
(4)
j
i
j
Table 1
RTi
Burning rate of CSPs with and without CuC2O4 nanocrystals (1 wt%).
Arrhenius parameters were evaluated for isothermal experi-
mental data by the model fitting method.
Additive
Burning rate (mm/s)
rbc/rb*
Nil
CuC2O4
1.15
1.65
1.00
1.43
3.2.4.2. Isoconversional method. This method allows the activation
rb and rb*c = burning rate of propellant with and without CuC2O4 nanocrystals,
respectively.
energy to be evaluated without making any assumptions about the
reaction model. Additionally, the method evaluates the effective

G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
501
Fig. 2. Microstructural image of CONs (a) FE-SEM images, (b) bright field TEM micrographs, (c) HRTEM images, and (d, e) SEAD pattern of CuC2O4 nanocrystals.
activation energy as a function of the extent of conversion which
allows one to explore multistep kinetics.
A˛
E˛
−
ln t˛,i = ln
−
(5)
g(˛)
RTi
The basic assumption of the isoconversional method [28] is that
the reaction model as defined in Eq. (1) is not dependent on temper-
ature or heating rate. Under isothermal conditions, on combining
Eqs. (3) and (4) we get,
where E˛ is evaluated from the slope of the plot of −ln t against
i
evaluated and the E˛ dependencies are shown in Fig. 6.
˛
,i
−
1
T
. Thus, E˛ at various ˛ for AP with and without CNOs have been
i

5
02
G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
Fig. 3. TG-DSC curves of AP with and without 1% CuC2O4 nanocrystals in nitrogen
atm.
3.3. Ignition delay measurements
The ignition delay (D ) measurements were made on 20 mg sam-
i
ples (100–200 mesh) by using a tube furnace technique [29] in the
◦
temperature range 360–420 C. The accuracy of the temperature of
◦
tube furnace was ± 1 C. The sample was taken in an ignition tube
Fig. 5. Isothermal TG of AP and AP + CuC2O4 (1% by wt) on different temperatures.
(
5 cm length × 0.4 cm diameter) and the time interval between the
insertion of the ignition tube into the TF and the moment of appear-
ance of a flame noted with the help of a stop watch with accuracy of
This equation has been found to be obeyed by a large number of
∗
0
.1 s gave the value of ignition delay (D ). The ignition tube clamped
explosives [33–38]. E assessed by above equation along with the
i
a
in a bent wire was inserted manually into the furnace up to a fix
depth (14 cm) just above the probe of the temperature indicator
cum controller (Century, Chandigarh). The time for insertion of the
ignition tube was also kept constant. Each run was repeated three
correlation coefficient (r) are given in Table 2.
4. Results and discussion
times, and mean D values are reported in Table 2. The D data were
found to be fit in equation [30–32],
i
i
4.1. XRD analysis
ꢀ
ꢁ
∗
Fig. 1 shows the structural characteristics of CONs investigated
by XRD. These studies reveal that the CONs obtained by colloidal
suspension of Cu(NO )·2H O and oxalic acid in acetone are crys-
E
a
D = A exp
(6)
i
RT
3
2
∗
a
where D is a time of ignition (ignition delay), A is constant, E is the
i
energy of activation (ignition) and T is the absolute temperature.
Fig. 4. TG curves of AP and CSPs with and without CuC2O4 nanocrystals.
Fig. 6. Dependencies of activation energy on the extent of conversion ˛.

G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
503
Table 2
Ignition delay (Di), activation energy for ignition (Ea) and correlation coefficient of AP and CSPs with and without CuC2O4 nanocrystals.
Sample
Di (s)
Ea (kJ mol−1)
r (correlation coefficient)
3
60 ± 1 ◦
C
375 ± 1 ◦
C
390 ± 1 ◦
C
405 ± 1 ◦
C
420 ± 1 ◦
C
AP
105
65
95
93
60
82
58
85
52
72
54
71
46
68
45
60
43
59
43
33.7
26.6
27.7
22.3
0.9885
0.9939
0.9930
0.9637
AP + CuC2O4(1 wt%)
HTPB-AP
HTPB-AP + CuC2O4 (1 wt%)
60
talline. The broadening of the peaks indicates nanometer size of
the products and no peak of impurity was observed in XRD pat-
tern. The relative crystalline sizes are determined from the XRD
line broadening using the Scherrer equation,
Fig. 4 clearly indicates that the thermal decomposition of AP
and CSPs is catalyzed by CONs. Burning rate of CSPs has also been
enhanced by this catalyst (Table 1). It is reported [21] that CuC O4
2
incorporates little or no water of crystallization in its crystal lattice,
which makes its decomposition not preceded by the disruption of
the crystal lattice caused by dehydration. The thermal decomposi-
0.9ꢀ
d =
ˇ cos ꢁ
tion of CONs in O atmosphere corresponds to strongly exothermic
2
where d is the crystallite size, ꢀ is the wavelength used in XRD
1.5418 A˚ ), ꢁ the Bragg angle, ˇ is the pure diffraction broadening of
reaction, owing to the reaction of evolved CO with oxygen to form
CO2 and the oxidation of the Cu decomposition product to a copper
oxide. Copper oxalate is anhydrous and the TG curve showed only
(
a peak at half height, i.e., broadening due to crystallite dimensions.
The size of CONs is estimated to be 12.4 nm according to the
Scherrer equation [39–41]. The XRD analysis when compared with
the standard data for CONs (JCPDS No. 21-0297) reveals the pres-
ence of a cubic phase (a = 5.40, b = 5.57, c = 2.54). The most intense
peak (intensity 100) is from the plane which corresponds to an
angle of 2ꢁ = 22.9.
◦
one decomposition step with onset at about 305 C due to breaking
−
−
of a C–O bond and a C–C bond of C2O4
solid slightly soluble in acidic (pH ≈ 6.0) water) as;
on, to form CuO (a black
O
O
CuO(s) + 2CO
2
.
H O
Cu + 0.5 O
2
2
4.2. Microstructural studies
O
O
Cu metal was not found to be formed on thermal decomposition
For microstructural studies the FE-SEM and TEM images of as
prepared CONs are presented in Fig. 2a and b. The FE-SEM image
Fig. 2a) of CONs reveals that the crystals are spherical in shape
of CONs. The X-ray diffraction peaks of residue left after the thermal
decomposition of CONs with AP is quite identical to those of pure
CuO (Fig. 7), which can be indexed as the monoclinic structure CuO
(
with narrow size distribution. Moreover, the particle size was found
to lay in the range 9–25 nm. The size of the particles observed in
the TEM image (Fig. 2b) is in the range of 9–12 nm, which is in
good agreement with that estimated by Scherrer equation. The TEM
images reveal that there is no agglomeration in the crystals of the
CONs. The HRTEM images reveal that the CONs are single crystals.
As shown in Fig. 2d and e, the selected area electron diffraction pat-
tern has many widen diffraction rings made up of many diffraction
spots which also indicate the nanocrystallinity of the CONs.
(
a = 4.68 A˚ , b = 3.42 A˚ , c = 5.12 A˚ ). The diffraction data are in agree-
ment with JCPDS card of CuO (JCPDS file No. 41-0254). According to
the Scherrer equation, the size of nano CuO was found to be 15 nm.
Copper oxide has a finer particle size with a large number of
defects and dislocations in the crystal lattice. Thus, a large number
of active sites would be available for the adsorption of reactants and
consequently increases the rate of reaction. The catalytic activity of
CONs in the thermolysis of AP and CSPs is measured by ignition
delay [11]. Ignition delay data given in Table 2 show that the time
required for ignition and activation energy for thermal ignition is
lowered by adding CONs in AP and CSPs. The process of ignition [46]
can never be treated as steady-state since it is a transient process
prior to sustained combustion.
4
.3. Thermal analysis
The results of TG-DSC (Fig. 3) and TG (Fig. 4) on AP with and
without CONs (1% by wt) shows that rate of decomposition of AP is
increased by CONs. The DSC curve for AP (Fig. 3) shows three events.
◦
The first endothermic DSC peak at 244 C represents the transition
from orthorhombic to cubic AP [42,43]. The second exothermic
◦
peak at 307 C is accompanied by a weight loss of 29% and cor-
responds to the partial decomposition of AP and formation of an
◦
intermediate. The third main exothermic peak at about 414 C is
associated with 70.5% weight loss. This corresponds to the com-
plete decomposition of the intermediate to volatile products. The
DSC curves of AP in presence of CONs show noticeable changes in
the decomposition pattern. From Fig. 3, it is clear that CONs have
◦
no effect on crystallographic transition temperature (244 C) of AP
◦
(
the endotherm), while large decrease of 130 C was observed in
high temperature exothermic peak where two exothermic peaks
of AP were merge to give only one.
The non-isothermal TG on AP (Fig. 4) shows two steps [44,45]. AP
◦
on heating first loses 25% of its mass at around 300 C, i.e., low tem-
perature decomposition (LTD). Beyond this temperature a plateau
◦
is observed; AP loses 80% of its mass at around 450 C, i.e., high tem-
perature decomposition (HTD). Experimental observation indicates
that CONs affect both LTD and HTD of AP.
Fig. 7. XRD pattern of CuO nanocrystals.

5
04
G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
Table 3
Set of reaction models applied to describe thermal decomposition of solids.
Model No.
Reaction model
f(˛)
g(˛)
3
2
1
/4
1/4
1
2
3
4
5
6
7
8
9
Power law
Power law
Power law
Power law
One-dimensional diffusion
Mampel (first order)
Avrami-Erofeev
Avrami-Erofeev
Avrami-Erofeev
Contracting sphere
Three-dimensional diffusion
Contracting cylinder
Prout-Tompkins
Ginstling-Brounshtein
4˛
3˛
2˛
˛
/3
/2
1/3
˛
1/2
˛
−
−
1/2
1
3/2
2/3˛
1/2˛
1 − ˛
˛
2
˛
−ln(1 − ˛)
3
2
1
/4
/3
/2
1/4
1/3
1/2
4(1 − ˛)[−ln(1 − ˛)]
3(1 − ˛)[−ln(1 − ˛)]
2(1 − ˛)[−ln(1 − ˛)]
[−ln(1 − ˛)]
[−ln(1 − ˛)]
[−ln(1 − ˛)]
2
2
/3
/3
1/3
10
11
12
13
14
3(1 − ˛)
1 − (1 − ˛)
2(1 − ˛) [1 − (1 − ˛)1/3]−1
[1 − (1 − ˛)1/3]2
1
/2
1/2
2(1 − ˛)
1 − (1 − ˛)
˛/(1 − ˛)
3/2[(1 − ˛)
ln(˛/1 − ˛)
−
1/3
− 1]−1
2/3
[1 − (2˛/3)] − (1 − ˛)
Table 4
Activation energy (Ea), Arrhenius parameters and correlation coefficient (r) for the isothermal decomposition of AP and AP with copper oxalate nanocrystals.
Model No.
AP
AP + CuC2O4
Ea (kJ mol 1
−
)
r
−ln A
Ea (kJ mol
−1
)
r
−ln A
1
2
3
4
5
6
7
8
9
94.69
95.00
95.60
98.48
99.46
97.97
97.06
95.64
96.29
97.72
100.22
97.59
102.06
88.57
0.9619
0.9622
0.9627
0.9646
0.9648
0.9641
0.9641
0.9626
0.9631
0.9640
0.9625
0.9640
0.9801
0.9288
13.8
14.1
14.3
14.6
14.4
15.1
14.6
14.4
14.7
13.8
12.8
14.2
17.5
10.3
66.42
67.06
68.32
75.53
78.66
74.39
70.85
68.59
70.07
73.60
80.74
73.21
68.57
45.68
0.9166
0.9192
0.9239
0.9407
0.9446
0.9383
0.9344
0.9240
0.9286
0.9371
0.9442
0.9364
0.9389
0.8548
10.8
11.1
11.5
12.6
12.9
13.1
12.0
11.6
12.1
11.7
11.5
11.9
13.4
4.4
1
1
1
1
1
0
1
2
3
4
Fourteen reaction models (Table 3) [27,47] were used to analyze
and AP + CONs has an initial overall activation energy of 140.5 and
◦
−1
isothermal TG data (in the range 300–340 C, Fig. 5) to calculate
the Ea values for thermal decomposition of AP and AP + CONs. The
activation energy (Ea) values, Arrhenius parameters and correla-
tion coefficients are reported in Table 4. The kinetics is analyzed
by choosing a best fit model based on the value of correlation coef-
ficient ‘r’ close to 1. Among the various values of r, calculated for
different models; the highest value of r for AP corresponds to model
3, i.e., Prout-Tompkins and AP with CONs corresponds to model
, i.e., the rate controlling process in the thermal decomposition
respectively being chain growth of nuclei and one-dimensional
122.2 kJ mol , respectively. These values decrease with the extent
−1
of conversion to about 104.5 and 80.8 kJ mol , respectively, for AP
and AP + CONs at the end of reactions.
A number of reactions have been reported [53,54] to be involved
in the decomposition and combustion of AP because of the four
elements and the full range of oxidation states utilized by nitro-
gen and chlorine. The breaking of an N–H bond, then proton
−
1
5
transfer from NH4+ to ClO4 to form an O–H bond leads to
the formation of NH3 and HClO4 in a primary step in condense
phases [55].
diffusion. The corresponding values of Ea calculated for AP and
−1
AP + CONs are 102.1 and 78.7 kJ mol , respectively (Table 4). The
results of kinetic analysis confirm that incorporation of CONs, cause
a noticeable decease in activation energy and consequently CONs
act as catalyst.
+
−
NH4 + ClO4 → NH –H–ClO → NH –HClO → NH (a)
3
4
3
4
3
(I)
(II)
(III)
+
HClO (a) → NH (g) + HClO (g)
4
3
4
The isoconversional method [28,48–51] is known to permit
estimation of the apparent activation energy, independent of the
model, corresponding to extent of conversion of the sample. This
method allows the activation energy to be evaluated without mak-
ing any assumptions about the reaction model. Additionally, the
method evaluates the effective activation energy as a function of
conversion which allows one to explore multistep kinetics. Though,
model fitting method using a set of reaction model applied to
isothermal data but model free approach (isoconversional method)
is a better method of obtaining reliable and consistent kinetic infor-
mation [52].
Further secondary reactions occur at higher temperature
through complex competitive steps to produce gaseous products.
5. Conclusion
The narrow size distribution of CONs is in agreement with the
result of XRD, SEM and TEM. TG-DSC and kinetic studies reveals
that the CONs have good catalytic effect on thermal decomposition
of AP and CSPs. The model free (isoconversional) and model-fitting
kinetic approaches have shown that rate of decomposition of AP
increases with CONs. Ignition delay and burning rate of CSPs were
also found to be enhanced with CONs.
According to Fig. 6, each activation energy has a separate value
at different ˛’s for both AP and AP + CONs. Kinetic analysis per-
formed by the isoconversional method on thermogravimetric data
(
Fig. 6) is consistent with the fact that thermal decomposition of AP

G. Singh et al. / Journal of Alloys and Compounds 513 (2012) 499–505
505
Acknowledgements
[25] R.P. Rastogi, G. Singh, R.R. Singh, Combust. Flame 33 (1978) 305.
[
26] G. Singh, R.R. Singh, Res. Ind. 23 (1978) 92.
27] M.E. Brown, D. Dollimore, A.K. Galway, Comprehensive Chemical Kinetics, vol.
2, Elsevier, Amsterdam, The Netherlands, 1960.
[28] S.V. Vyazovkin, Int. J. Chem. Kinet. 28 (1996) 95.
[
The authors are grateful to Head, Chemistry Department of DDU
Gorakhpur University for laboratory facility and IIT Roorkee for
TG-DSC. Thanks are also due to financial assistance by UGC for pro-
viding Emeritus Fellow to G. Singh and Project Fellowship to Reena
Dubey.
2
[
[
29] G. Singh, S.K. Vasudeva, I.P.S. Kapoor, Indian J. Technol. 29 (1991) 589.
30] N. Semenov, Chemical Kinetics and Chain Reactions, vol. 18, Clarendon Press,
Oxford, UK, 1935.
[31] E.S. Freeman, S. Gordon, J. Phys. Chem. 60 (1956) 867.
[
[
32] J. Zinn, R.N. Rogers, J. Phys. Chem. 66 (1962) 2646.
33] G. Singh, B.P. Baranwal, I.P.S. Kapoor, D. Kumar, C.P. Singh, R. Frohlich, J. Therm.
Anal. Calorim. 91 (3) (2008) 971.
References
[
34] G. Singh, B.P. Baranwal, I.P.S. Kapoor, D. Kumar, R. Frohlich, J. Phys. Chem. A 111
(2007) 12972.
[
[
[
[
[
[
1] P.W.M. Jacob, H.M. Whitehead, Chem. Rev. 69 (1969) 551.
2] V.V. Boldyrev, Thermochim. Acta 443 (2006) 1.
3] V.G. Dedgaonkar, D.B. Sarwade, J. Therm. Anal. 36 (1990) 223.
4] P.R. Patil, V.N. Krishnamurthy, S.S. Joshi, Propell. Explos. Pyrot. 33 (2008) 266.
5] G. Singh, I.P.S. Kapoor, S. Dubey, P.F. Siril, J. Sci. Conf. Proc. 1 (2008) 7.
6] G. Singh, I.P.S. Kapoor, S. Dubey, P.F. Siril, Propell. Explos. Pyrot. 34 (1) (2009)
[35] G. Singh, R.R. Singh, A.P. Rai, I.P.S. Kapoor, J. Therm. Anal. 36 (1990) 2539.
[36] G. Singh, I.P.S. Kapoor, D. Kumar, U.P. Singh, N. Goel, Inorg. Chim. Acta 362
(2008) 4091.
[37] H. Henkin, R. McGill, Ind. Eng. Chem. 44 (1952) 1391.
[38] K. Singh, Trans. Faraday Soc. 55 (1959) 124.
7
2.
[39] X. Lu, X. Wang, J. Zhang, L. Lu, Thermochim. Acta 342 (1999) 97.
[40] L.S. Birks, H. Friedman, J. Appl. Phys. 17 (1946) 687.
[41] E. Lamprecht, G.M. Watkins, M.E. Brown, Thermochim. Acta 446 (2006) 91.
[42] K. Kishore, K. Sridhara, Solid Propellant Chemistry: Condense Phase Behavior
of Ammonium Perchlorate Based Solid Propellants, DESIDOC, New Delhi, 1999,
p. 10.
[
[
[
7] J. Zhu, D. Li, H. Chan, X. Yang, L. Lu, X. Wang, Mater. Lett. 58 (2004) 3324.
8] L. Liu, F. Li, L. Tan, L. Miang, Y. Yi, Propell. Explos. Pyrot. 1 (2004) 29.
9] A.A. Said, Therm. Anal. 37 (1991) 959.
10] F. Solymosi, E. Krix, J. Catal. 1 (1962) 468.
11] G. Singh, S.P. Felix, Combust. Flame 132 (2003) 422.
12] G. Singh, I.P.S. Kapoor, S. Dubey, J. Alloys Compd. 480 (2009) 270.
13] G. Singh, I.P.S. Kapoor, S. Dubey, S.P. Flix, J.H. Yi, F.Q. Zhao, R.J. Hu, Thermochim.
Acta 477 (2008) 42.
14] P. Srivastava, I.P.S. Kapoor, G. Singh, J. Alloys Compd. 485 (2009) 88.
15] B. O’Regan, M. Gratzel, Nature 353 (1991) 737.
16] A. Fujishima, T.N. Rao, D.A. Tryk, J. Photobiol. C: Photochem. Rev. 1 (2000) 1.
17] T. Rajh, Z. Saponjic, J. Liu, N.M. Dimitrijevic, N.F. Scherer, M. Vega-Arroyo, P.
Zapol, L.A. Curtiss, M.C. Thurnauer, Nano Lett. 4 (2004) 1017.
18] H. Tokuhisa, P.T. Hammond, Adv. Funct. Mater. 13 (2003) 831.
19] L. Cristina Soare, P. Bowen, J. Lemaitre, H. Hofmann, J. Phys. Chem. B 110 (2006)
[
[
[
[
[43] F. Solymosi, Acta Phys. Chem. 20 (1974) 1.
[44] L.L. Bircumshaw, B.H. Newmann, Proc. Roy. Soc., A 227 (1954) 115.
[45] P.W.M. Jacobs, G.S. Pearson, Combust. Flame 13 (1969) 419.
[46] B.L. Hicks, J. Chem. Phys. 66 (1962) 2646.
[47] S. Vyazovkin, I. Dranca, X. Fan, R. Advincula, Macromol. Rapid Commun. 25
(2004) 498.
[
[
[
[
[48] I.P.S. Kapoor, P. Srivastava, G. Singh, U.P. Singh, R. Frohlich, J. Phys. Chem. A 112
(2008) 652.
[
[
[49] S. Vyazovkin, C.A. Wight, Chem. Mater. 11 (1999) 3386.
[50] A.J. Lang, S. Vyazovkin, Combust. Flame 145 (2006) 779.
[51] S. Vyazovkin, C.A. Wight, Thermochim. Acta 340 (1999) 53.
[52] S. Vyazovkin, A.K. Burnham, J.M. Criado, L.A. Perez-Maqueda, C. Popescu, N.
Sbirrazzuali, Thermochim. Acta 520 (2011) 1.
[53] W.A. Rosser, S.H. Inami, H. Wise, Combust. Flame 12 (1968) 427.
[54] N.E. Ermolin, O.P. Korobeinchev, A.G. Tereshenk, V.M. Foomin, Combust. Explos.
Shock Waves 18 (1982) 180.
1
7763.
[
[
[
20] D. Dollimore, Thermochim. Acta 117 (1987) 331.
21] A. Coetzee, D.J. Eve, M.E. Brown, J. Therm. Anal. 39 (1993) 947.
22] J. Romann, V. Chevallier, A. Merien, J.C. Valmalette, J. Phys. Chem. C 113 (2009)
5
068.
[
[
23] S. Krishna, R.D. swami, J. Propul. Power 13 (2) (1997) 207.
24] R.P. Rastogi, G. Singh, B.L. Dubey, C.S. Shukla, J. Catal. 65 (1980) 25.
[55] G. Singh, I.P.S. Kapoor, D.K. Pandey, J. Energy Mater. 20 (2002) 223.