Investigation of kinetic parameters for ammonium perchlorate thermal decomposition in presence of gCN/CuO by TG-MS analysis and kinetic compensation correction

Article abstract of DOI:10.1016/j.jssc.2021.122301

The desire to develop a benign burn rate modifier for propellants has accentuated polymeric carbon nitride (gCN) as a potential candidate for the thermal decomposition of ammonium perchlorate (AP). Here, we have synthesized composites of leaf-shaped CuO and gCN via a facile sonochemical approach. From DSC analysis, the addition of gCNCuO1 reduced the decomposition temperature of AP by 59°C and increased the heat release by ~ 1.4 times that of pure AP. The kinetics of AP decomposition was well investigated via in-situ TG-MS technique. From evolved gas analysis evolution of NO, Cl, HCl, N₂O/CO₂, NO₂ and Cl₂ fragments were detected. The quantitative interpretation of kinetic parameters for AP decomposition was done using Coats-Redfern method and the normalization of E values were carried out by applying Kinetic Compensation Correction (KCC). After normalization, E values were decreased by 17 ?kJ/mol and 18 ?kJ/mol for the first and second stages respectively.

Full text of DOI:10.1016/j.jssc.2021.122301

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Journal of Solid State Chemistry 301 (2021) 122301
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Investigation of kinetic parameters for ammonium perchlorate thermal
decomposition in presence of gCN/CuO by TG-MS analysis and kinetic
compensation correction
,b,*
Gladiya Mani a, Jisna Jos a, P. Radhakrishnan Nair b, Suresh Mathew a
a School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, 686 560, India
b Advanced Molecular Materials Research Centre (AMMRC), Mahatma Gandhi University, Kottayam, Kerala, 686 560, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
The desire to develop a benign burn rate modifier for propellants has accentuated polymeric carbon nitride (gCN)
as a potential candidate for the thermal decomposition of ammonium perchlorate (AP). Here, we have synthesized
composites of leaf-shaped CuO and gCN via a facile sonochemical approach. From DSC analysis, the addition of
gCNCuO1 reduced the decomposition temperature of AP by 59ꢀC and increased the heat release by ~ 1.4 times
that of pure AP. The kinetics of AP decomposition was well investigated via in-situ TG-MS technique. From
evolved gas analysis evolution of NO, Cl, HCl, N2O/CO2, NO2 and Cl2 fragments were detected. The quantitative
interpretation of kinetic parameters for AP decomposition was done using Coats-Redfern method and the
normalization of E values were carried out by applying Kinetic Compensation Correction (KCC). After normalization,
E values were decreased by 17 kJ/mol and 18 kJ/mol for the first and second stages respectively.
Ammonium perchlorate
Polymeric carbon nitride
Coats-redfern method
Kinetic compensation effect
1. Introduction
involves chemical changes particulary in gas-phase and liquid-phase re-
actions. Even though most of the solid-state reaction kinetic principles
Being one of the most imperative and prevalent energetic material for
rocket propellants and missiles, ammonium perchlorate (AP) has
received ample attention in the world of research. AP accounts for almost
60–75% of the total mass of the propellant [1–3] and it is believed that
were derived from homogeneous systems, it is much challenging to
extent such principles to heterogeneous reactions. AP thermal decom-
position is considered to be one of such complex heterogeneous system.
Recent reports reveal that a 2-dimensional, metal-free and eco-
friendly semiconductor, ‘polymeric carbon nitride’ (gCN) is a potential
candidate for thermal decomposition of AP [6]. Although gCN started to
use as a heterogeneous catalyst only in 2006, it is considered as one of the
oldest reported artificial polymer in the open literature [7]. Chemically,
gCN is a linear polymer of ‘tri-s-triazine’ rings interconnected via sec-
ondary nitrogen [8]. Owing to the structural resemblance with graphite,
gCN possesses strong covalent C–N bonds in each layer which are
bounded by van der Waals forces [9]. The advantageous features of gCN
such as simple composition, presence of basic surface functionalities and
H-bonding motifs [10] have dazzled the research community. Besides the
aforementioned properties, features like high chemical and thermal
stability, high surface area and low bandgap (2.7eV) [11] have opened
the horizon of application in various fields specifically, hydrogen pro-
duction [10,12], biosensing [13], organic reactions [7,14] and fuel cells
[15]. Amid the high cost of metal oxide catalysts for solid propellants,
gCN is of low cost and can be easily synthesized from thermal
the distinctive thermal conduct of ammonium perchlorate has
a
momentous impact on the performance of composite solid propellants
[1]. AP is exceptionally sensitive to additives [4], and these additives
tailor the ballistic properties especially burning rate which inherently
affects the propellant performance. Hence, the development of superior
additives to enhance the propellant burn rate has become a motto behind
modern research on propellants [5]. Ample attention has been devoted to
the quantitative interpretation of kinetic parameters for these decom-
position reactions. Compared to any other homogeneous reaction ki-
netics such as solution or gases, solid-state reactions are more complex
and differ substantially. Many controversies have arisen in interpreting
their kinetic parameters namely activation energy and pre-exponential
factor. Generally, pre-exponential factor gives the no. of collisions that
have enough energy to overcome the activation barrier. It can be used for
significant reaction model kinetics especially inorder to study reaction
engineering or process modelling or optimization of processes that
* Corresponding author. School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, 686 560, India.
E-mail address: sureshmathewmgu@gmail.com (S. Mathew).
https://doi.org/10.1016/j.jssc.2021.122301
Received 18 February 2021; Received in revised form 14 May 2021; Accepted 26 May 2021
Available online 1 June 2021
0022-4596/© 2021 Elsevier Inc. All rights reserved.

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G. Mani et al.
Journal of Solid State Chemistry 301 (2021) 122301
condensation of urea, melamine, dicyandiamide and thiourea [8,16].
Various strategies have been adopted for improving the catalytic activity
of gCN [9,17,18], among which physical compounding of gCN with
metal oxides has drawn wide attention [19–21].
was dissolved gradually in 5.5 ml deionized water with constant stirring
to keep the temperature low. To the above CuSO4 clear solution, NaOH
solution was added very slowly with constant stirring. A bluish-black
precipitate appears suddenly. The reaction flask was heated for 45 min
to 1 h while maintaining the temperature at 80ꢀC and stirring the reac-
tion mixture intermediately. The brownish-black thick precipitate of
copper oxide thus obtained was washed with a sufficient amount of
deionized water and filtered free of alkali. It was then dried to remove
any trace of water. The precipitate was ground using mortar and pestle
and used for further synthesis.
CuO, a covalent p-type semiconductor with a bandgap between 1.21
eV and 1.7 eV [22] is well studied for its catalytic activity in various fields
especially in solid propellants [23–25]. It has been reported that cop-
per(II) oxide nanocrystals are suitable additives for catalytic decompo-
sition of AP, and can significantly reduce the high-temperature
decomposition and increase the heat release during decomposition of AP
[24,26–29]. Synthesis of high-quality CuO nanomaterials with chemical
purity, crystallinity, phase selectivity and size homogeneity via a feasible
cost-effective method is still a challenge in materials synthesis [30].
Increasing awareness towards green chemistry and sustainability has
stimulated a desire to develop an eco-friendly burn rate modifier for
composite solid propellants [6]. As a step closer to it, we have synthe-
sized a burn rate catalyst based on gCN with reduced metal content. To
the best of our knowledge, there are still very few reports on gCN based
burn rate modifiers for composite solid propellants [6,20,31,32]. Earlier,
Hosseini et al. reported the synthesis of CuO nanoparticles on
The reaction of formation of CuO can be summarized as follows:
CuSO4 :5H2O þ 2NaOH → CuðOHÞ2 ↓ þ Na2SO4 þ 5H2 O
(1)
Δ
CuðOHÞ2
CuO þ H2O
!
2.1.3. Synthesis of gCN/CuO (gCNCuO) composite
The gCN/CuO composite was synthesized via a facile sonochemical
approach (Fig. 1). A series of four gCN/CuO composites were synthesized
with varying CuO content. The typical procedure for the synthesis of
gCNCuO1 (1: 1) is as follows: 0.2 g of gCN was well dispersed in 45 ml of
methanol by ultrasonication for 30 min. To this, 0.2 g of CuO was added.
The mixture was sonicated for another 1 h and dried at 60ꢀC for 4 h.
Finally, the blackish-grey powder obtained is calcinated at 300ꢀC for 3 h
in the air to strengthen the interaction between leaf-shaped CuO and gCN
matrix. The other composites were also prepared using the same pro-
cedure by changing the concentration of CuO. The ratios between gCN
and CuO in the other prepared composites were 1: 0.6, 1: 0.3 and 1: 0.15
and are represented as gCNCuO2, gCNCuO3, and gCNCuO4 respectively.
three-dimensional
nitrogen-doped
graphene-based
frameworks
(CuO@3D-(N)GFs) for AP decomposition [33]. Zhang et al. synthesized
microwave-assisted m-g-C3N4/CuO through microwave-pretreatment
and mixing-calcination methods. By using this catalyst the decomposi-
tion temperature of AP was decreased by 136ꢀC and heat release was
increased by seven times [34]. Very recently Chandrababu et al. reported
the decomposition kinetics of AP using (Cu/Cu2O)/g-C3N4 nano-
composite via FWO method. Even though the E values for the decom-
position reactions were not decreased, the reaction rate increased
tremendously [35]. Here, we have undertaken an attempt to quantita-
tively interpret the kinetic parameters for the decomposition of AP in
presence of a gCN-CuO catalyst using the Coats-Redfern (CR) method.
Although kinetic compensation effect has been known for long time, not
much efforts have been undertaken to explain the kinetics of AP
decomposition using kinetic compensation effect. In this work we could
successfully normalize the activation energy by applying Kinetic
Compensation Correction. Thus, an effort to extent homogeneous system
to heterogeneous became sensible. Different from previous results on AP
decomposition using copper oxide doped polymeric carbon nitride
catalyst, for the first time we have made use of in-situ TG-MS for inter-
preting the decomposition pattern of AP via evolved gas analysis. TG-MS
helped us to understand the decomposition products in presence of the
synthesized catalyst and effective interaction between NH3 & HClO4
molecules. In this work, CuO modified gCN binary composites were
synthesized by a facile sonochemical approach.
3. Characterization
The composition and phase purity of the as-synthesized samples were
analyzed by a Rigaku Miniflex 600 powder x-ray diffractometer with
monochromatized Cu-Kα (λ ¼ 1.5425 Å) incident radiation. XRD patterns
were recorded in the range of 10-80ꢀ 2θ. Crystalline phases were iden-
tified by comparing diffraction patterns with JCPDS values. FT-IR spectra
of the samples were recorded by a PerkinElmer 400 Spectrometer in the
range 4000-400 cmꢁ1. Field Emission Scanning Electron Microscopic
(FE-SEM) images and Energy Dispersive X-ray (EDAX) analysis was
recorded on Carl Zeiss instrument model Ultra-55 operating at 20 kV.
High-Resolution Transmission Electron Microscopy (HRTEM) images
were taken using a JEOL JEM-2100 microscope at an accelerating voltage
of 200 kV. The Brunauer-Emmet-Teller (BET) specific surface area, pore
size and pore volumes of the samples were analyzed by a Thermo Fischer
Scientific Surfer particle analyzer. All the samples were degassed at 150
ꢀC for 4 h before nitrogen adsorption measurements were taken. The EPR
spectra of gCNCuO1 was recorded at room temperature using JEOL JES-
FA Series A EPR spectrometer at a working frequency range of 8.75–9.65
GHz.
2. Experimental
The following chemicals were purchased and used as received. Cop-
per Sulphate (Rankem, 99.5%), Sodium Hydroxide pellets (Rankem,
97%), Urea (Spectrum, 99%) and Ammonium Perchlorate (APEP, ISRO,
Aluva, >99%). All the chemicals were of analytical grade.
3.1. Catalytic activity measurement
2.1. Synthesis
To evaluate the catalytic activity of the as-prepared CuO decorated
2.1.1. Synthesis of gCN
gCN composites, ammonium perchlorate (average particle size <100 μm)
gCN was synthesized by the thermal condensation of urea. Typically,
about 5 g of urea was taken in a silica crucible and heated in a muffle
furnace at 530ꢀC for 4 h at a heating rate of 3ꢀC/min. After cooling it to
room temperature naturally, a pale yellow colored gCN powder was
obtained. This was then manually grounded to a fine powder using a
mortar and pestle and used for further analysis.
were thoroughly mixed with the catalysts by a physical grinding method.
i.e. AP was taken in a mortar to which catalysts were added and ground
physically using pestle for 30 min. Thermogravimetric (TG) and differ-
ential scanning calorimetric (DSC) analysis were used to investigate the
thermal decomposition of the mixture (98% AP: 2% catalyst by mass)
from 50ꢀC to 450ꢀC under N2 atmosphere at a heating rate of 5ꢀC/min.
The measurements were performed on a PerkinElmer 8000 TG analyzer
and TA instruments TG-DSC Q600 with a sample mass of 5.7 ꢂ 0.1 mg in
an alumina crucible. The evolved gas analysis was done using TG-GC-MS
coupled technique on a PerkinElmer TGA 8000 coupled PerkinElmer
2.1.2. Synthesis of leaf-shaped CuO
About 4.7 g CuSO4.5H2O was dissolved in 35 ml of deionized water
very slowly to get a greenish-blue solution. Then around 1.7 g of NaOH
2

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Journal of Solid State Chemistry 301 (2021) 122301
Fig. 1. Schematic diagram of the synthesis of gCNCuO.
Clarus SQ8T GC-MS to understand the decomposition products at a
indicate that the product is crystalline. It should be noted that gCN/CuO
composites show all characteristic peaks of gCN and CuO, indicating the
existence of CuO in the as-prepared composites. Here, it is interesting to
note that, the intensity of diffraction peaks corresponding to CuO is
decreasing as the concentration of CuO in composite decreases. It is also
noteworthy that, the presence of CuO does not make much difference in
the position of XRD peaks of gCN.
temperature range of 100–350ꢀC at a heating rate of 2.5ꢀC/min.
4. Results and discussions
4.1. XRD analysis
The crystalline nature and phase purity of the synthesized samples
merely depend on the synthetic procedure adopted and reaction condi-
tions. Hence, the crystalline features of the synthesized samples were
analyzed using XRD. The XRD patterns of gCN with two distinct
diffraction peaks are shown in Fig. 2a. A sharp peak at 27.3ꢀ corresponds
to the (002) facet and another one at 13.1ꢀ corresponds to the (100) facet
of gCN (JCPDS No: 87–1526) [6]. The intense peak at 27.3ꢀ indexed for
graphite-like material attributes to an interlayer stacking of aromatic
units of distance d ¼ 0.326 nm. The peak at 13.1ꢀ corresponds to in-plane
stacking of aromatic units with d ¼ 0.675 nm features the hole-to-hole
distance of the nitride pores in the crystals [36]. These two diffraction
patterns are consistent with the XRD patterns of gCN reported in the
literature [36,37].
4.2. FT-IR spectra
XRD results obtained were validated by FT-IR investigation. In FT-IR
spectroscopy, the region below 1000 cmꢁ1 is generally associated with
the stretching vibration modes of M ꢁ O bonds which further prove the
metal oxide formation. It also provides information about the compound
purity and structural integrity of the sample [40]. Fig. 3 shows the FT-IR
spectra of all the samples.
Pure gCN shows several bands in the 1200-1650 cmꢁ1 region, typi-
cally at 1237, 1402 and 1643 cmꢁ1 which are ascribed to the charac-
teristic stretching modes of CN heterocycles, demonstrating the
formation of extended networks of C–N–C bonds. A pronounced band at
807 cmꢁ1 corresponds to the breathing vibrations of the tri-s-triazine
units. The broad bands between 3000 and 3400 cmꢁ1 are attributed to
the secondary and primary amines [41,42]. While, the peaks around 603
As shown in Fig. 2b, the diffraction peaks of CuO corresponds to the
monoclinic phase of CuO (JCPDS 48–1548) [38,39]. No diffraction peaks
from any other impurities were observed. The strong and sharp peaks
Fig. 2. XRD patterns of (a) gCN (b) CuO, gCNCuO1, gCNCuO2, gCNCuO3 and gCNCuO4.
3

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G. Mani et al.
Journal of Solid State Chemistry 301 (2021) 122301
Fig. 3. FT-IR spectra of gCN, CuO and gCN/CuO composites.
Fig: 4. FE-SEM images of gCN with pores (a), leaf-shaped CuO particles (b–c), gCN/CuO composite (d) and EDAX image confirms the presence of Cu, O, C and N in the
composite (e).
cmꢁ1, 502 cmꢁ1 and 462 cmꢁ1 refer to CuO. The absorption band at 603
dependent. Hence, detailed morphological and crystallographic proper-
ties of the as-prepared gCN, CuO and gCN/CuO samples were investi-
gated by FE-SEM, TEM, EDAX and selected area electron diffraction
(SAED). The textural structure and morphological features of gCN are
shown in Fig. 4a. The image at high magnification clearly shows that gCN
has a porous sheet-like structure. The SEM images given in Fig. 4b-c
demonstrates that the synthesized CuO nanoparticles have leaf
morphology. The high magnification image (Fig. 4d) exhibits the proper
dispersion of CuO nanoparticles over gCN sheets to give the desired
composite. EDAX image given in Fig: 4e endorse the presence of Cu, O, C
and N in the composite.
cmꢁ1 corresponds to Cu–O stretching vibration along (ı01) direction and
ꢀ
the peak at 502 cmꢁ1 is because of stretching vibration along the (101)
plane [43]. Notably, for the gCN/CuO composite, all of the peaks of gCN
and CuO can be observed, suggesting the formation of the composite.
4.3. Field Emission-Scanning Electron Microscopy and Energy Dispersive
X-Ray analysis
For nanomaterials, all its characteristic features such as catalytic ac-
tivity, optical properties, and magnetic properties are morphology
4