The Catalytic Effect of CuO-doped Activated Carbon on Thermal

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C: Surfaces, Interfaces, Porous Materials, and Catalysis

The Catalytic Effect of CuO-doped Activated Carbon on Thermal Decomposition and Combustion of AN/Mg/NC Composite Meiram Atamanov, Zhanerke Yelemessova, Aldan Imangazy, Kaster Kamunur, Bakhytzhan Lesbayev, Zulkhair Mansurov, Tang Yue, Ruiqi Shen, and Qi-Long Yan J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b05094 • Publication Date (Web): 28 Aug 2019 Downloaded from pubs.acs.org on August 29, 2019

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The Journal of Physical Chemistry

The Catalytic Effect of CuO–doped Activated Carbon on Thermal Decomposition and Combustion of AN/Mg/NC Composite Meiram Atamanov*1, Zhanerke Yelemessova2,3, Aldan Imangazy2,3, Kaster Kamunur2,3, Bakhytzhan Lesbayev2,3, Zulkhair Mansurov2,3, Tang Yue4, Ruiqi Shen4, Qi-Long Yan*1 1, Science and Technology on Combustion, Internal Flow and Thermo-structure Laboratory, Northwestern Polytechnical University, Xi'an 710072, China; 2, al–Farabi Kаzakh National University, Аlmaty 050040, Каzakhstan; 3, Institute of Combustion Problems, Almaty 050012, Кazakhstan; 4, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China E-mail: [email protected] (M.K. Atamanov) [email protected] (Q.L. Yan)

ABSTRACT: The activated carbon (AC) doped with CuO (AC–CuO) has been prepared and evaluated as a promising catalyst of energetic compositions. The catalytic activity of AC–CuO on ammonium nitrate/magnesium/nitrocellulose (AN/Mg/NC) composite has been investigated as a typical example. It has been shown that AC–CuO could greatly enhance the decomposition and combustion performances of energetic composites. Thermal analyses indicate that the AC– CuO has significant catalytic effects on decomposition of AN/Mg/NC composite by decreasing the decomposition peak temperature from 261.4 to 209.0 °C, with decreased the activation energy from 90.1 kJ mol-1 to 81.5 kJ mol-1. The linear burning rate of AN/Mg/NC composite in presence of AC–CuO increases approximately twice (rb = 20.46 mm s-1 vs. rb = 10.27 mm s-1 at chamber pressure of p0 = 3.5 MPa). 1.

INTRODUCTION

Ammonium nitrate (AN, NH4NO3) is one of the commercially available and widely used compounds mostly as fertilizer or component of civil explosives.1 AN is very safe for handling and storage, and it does not contain harmful products after its thermal decomposition or combustion.2 However, the weak ignitability and low heat of formation, high hygroscopic properties limit its application in the field of energetic compositions.3 The effects of additives on combustion/decomposition characteristics of AN and AN-based compositions have been widely studied by many authors. 4-6 Recently, researchers have reported that transition metal oxides such as MnO2, Fe2O3, TiO2 and CuO could well catalyze the thermal decomposition of AN-based propellants.7-9 Also, the influence of the nanoparticles and nanocatalysts on the combustion/decomposition of AN has also been evaluated.10,11 It was mentioned that the promotion of thermal decomposition process by the nano-sized CuO and NiO shows a strong effect on decreasing the decomposition temperatures of nitramine or AP as oxidizers.12 The carbon nanomaterials including carbon nanotubes (SWCNT, MWCNT)13, graphene sheets (GS, GO, rGO)14–18 and fullerenes19–20 are novel materials that can be used to improve the thermal conductivity, the heat release and reactivity of the various EMs. They help to achieve the desired performances, but certainly they are usually not so cost-effective due to complicated technology for production. Among the possible substitutes for expensive carbon nanomaterials, the most promising one is the activated carbon (AC), which can meet all the requirements for applications in EMs and their compositions. For example, it has been reported that the AC has been used as a technological additive for modifying the burning rate in non– and metalized energetic systems.21 The effects of an AC and its composites (ACs) on the thermal decomposition/combustion of EMs have also been studied in several works.22–26

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The AC with a high specific surface area (~3000 m2/g) based on rice husk (RH) was investigated as a promising additive in this work. RH is a large–scale vegetable unique material, which is a highly cost-effective renewable green material.27 In comparison to the other carbon nanomaterials, ACs have some promising properties (handling, storage, and transportation) and their stocks are huge in rice–growing countries. Therefore, the replacement of expensive carbon nanomaterials with ACs will make these materials widely applied in catalysts industry.28 The main objectives of this study: (i) investigation of catalytic efficiency of AC doped with CuO on combustion of AN/Mg/NC composite. (ii) study of thermal decomposition kinetics of AN/Mg/NC composite in the presence of AC doped with CuO by the DSC-TG analysis at different heating rates; 2.

EXPERIMENTAL PART

2.1

Materials and Propellant Samples

The samples of AC were obtained from the cleared RH. Then the RH was carbonized in an iron reactor in an argon medium. The carbonized RH was placed into a potassium hydroxide solution to remove silicon dioxide, followed by decantation of the solution to remove the base, and transferred to the reactor for activation at 900 °С. Then the synthesized AC was washed with distilled water by the method of boiling - precipitation - decanting with a cycle of 10–15 times to achieve pH value of 7. In all resulting in formation of AC with high specific surface area of 3000 m2/g (by BET analysis) and a high absorption capacity of ~372 ml/g (by the methylene blue in Table S1).26 AN was used as an oxidizer in the condensed composition with a diameter of particles between 212–250µm. AN (NH4NO3) was ≥99% purity (without further purification). Magnesium powder (Mg) was used as a high energetic fuel with partial diameter around 200µм and ≥ 99% purity, melting point ~650 °С and density 1.74 g/ml at 25 °C (lit. Sigma Aldrich). Copper oxide acted as a catalyst was mechanically included on the surface and pores of AC by the mechanical method in the planetary mill (10 min).29-30 The diameter of the basic metal oxide particles was in 60–70 µm range. Nitrocellulose (NC) polymer was used as an energetic binder. It is one of the basic and widely spread components of rocket propellants, fireworks, ammunition systems, mining explosives, etc. NC (12.6% N) used in this study was supplied as a solution in 5% ethanol (purity grade 96%). 2.2

Sample preparation

All components of AN/Mg/NC composite and pure AC or AC doped with CuO was dried (24 hour) and dispersed in the ball mill (15 min). All samples were prepared by a solvent-free milling method. The samples used in burning tests were pressed in a hydraulic machine under the pressure of 5 MPa to the tablets with the diameter of 6 mm with a length of 10 mm. 2.3

Measurement of the Combustion Characteristics

The process of combustion was studied in a nitrogen medium in a chamber. The sample was ignited by nichrome wire. Each of the samples is ignited at initial pressure of 1 to 3.5 MPa. The combustion chamber is equipped with a glass window for observing and recording of the


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burning process by a high speed video camera (scientific model Roper 2000, USA) with a frequency of at 1000 fps and a resolution of 640×488 pixels. The linear burning rate is one of the important ballistic properties of energetic materials. To determine the burning rate, the recorded videos from the high-speed camera were used. This equipment allows for dynamic recording of combustion of the specimens from initiation to complete burnout. The recorded linear rate of sample regression expressed in mm s-1. Measurement accuracy was around ±0.01 mm, and all experiments were repeated three times to get the average burning rate. Figure 1 shows the equipment for the burning experiments.

Figure 1. Scheme of the combustion chamber under pressure: 1 – sample holder; 2 – window; 3 – the light source; 4 – exit valve; 5 – exhaust line; 6 – power supply; 7 – lens; 8 – camera; 9 – video recorder; 10 – PC; 11 – pressure manager; 12 – pressure gauge. The burning rate is strongly affected by the value of initial pressure. The pressure dependence on linear burning rate is described by the Saint Robert's Law expression (Vieille's Law): rb = r0 + a[P(MPa)]n where rb is the linear burning rate, in mm s-1; r0 is a constant (initial burning rate); a is the burning rate coefficient; n is pressure exponent. The values of a and n are empirical parameters, and cannot be theoretically predicted. This expression helps to correlate the linear burning rate as a function of pressure for an application in a wide range of operating conditions.31 3

RESULTS AND DISCUSSION

3.1

Physicochemical Characteristics of AC Based Additives.



The results of elemental analysis (EDAX) of AC–CuO are shown in Figure S1. The presence of a small quantity of metals (potassium, iron, and nickel) on the AC surface associated by the production technology (chemical activation with various active reagents, containers). Analyzes of the Raman spectra in Figure S2 showed the intensity of the G and D bands (ID / IG = 0.63), which allows us to conclude that AC a graphene scales (three or more layers). The morphology of AC doped with CuO particles was studied by scanning electron microscopy (SEM). The results are shown in Figure 2.

Figure 2. The SEM images of AC–CuO composite. Figure 2 presents two SEM micrographs of the surface morphology of AC–CuO composite at different resolutions. AC based on carbonized RH has a developed macro– and microstructure depending on the starting material (RH). Usually, the AC obtained from a rice huck has a honeycomb structure with a set of cells and round shape voids with a size of 3×3 µm (shown in Figure S3). The high specific surface area, porosity, adhesive properties and average inertness make AC perfect support for various metal oxide catalysts. 3.2

Characteristics of thermal decomposition by DSC-TG

The measured DSC curves of AN/Mg/NC composite in the presence of various additives (pure and copper oxide – containing AC) at β = 5 K/min heating rate in a nitrogen medium are presented in Figure 3 and the detailed thermal decomposition parameters are listed in Table 1. Figure 3a shows the DSC curve of AN/Mg/NC (in the ratio: 60/35/5) composite without any additives. Decomposition of the composite was correlated to 2-stage exothermic reactions. First, exothermic peaks are at Tmax = 199.2 °С and at Tmax = 276.4 °С. The first exothermic peak at 199.2 °C corresponds to NC thermal decomposition.32 The pure NC decomposes at 207.8 °C (heating rate 10 K/min, exothermic reaction)33, and similar results were reported in several papers.34,35 The second peak corresponds of the ammonium nitrate decomposition.28 The DSC curve of AN/Mg/NC indicates that, there is initially a small heat absorption peak due to polymorphic transition of AN, accompanied by a weak endothermic peak of water evaporation.


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Table 1. Thermal data in terms of Tonset, Toffset and Tmax obtained from DSC thermograms Sample

AN/Mg/NC

AN/Mg/NC/AC

AN/Mg/NC/AC–CuO

β, K/min

5 10 15 20 5 10 15 20 5 10 15 20

Thermal decomposition 1st step Tonset Toffset Tmax (180 – 230 °C) 173.0 211.3 199.2 176.3 223.5 203.9 187.1 223.9 206.9 186.2 223.5 206.2 (100 – 180 °C) 107.6 172.3 123.1 116.8 176.5 128.1 117.5 179.1 137.0 117.9 186.8 140.5 (100 – 200 °C) 105.3 174.9 126.4 111.8 171.4 131.9 113.0 186.2 136.2 114.5 188.1 134.6

2st step Tonset Toffset (230 – 300 °C) 232.5 269.1 243.0 287.4 245.1 292.8 252.9 307.5 (210 – 270 °C) 214.3 225.1 230.8 245.0 234.0 254.3 239.5 261.9 (200 – 260 °C) 202.7 217.1 215.3 228.5 223.8 240.0 225.1 250.5

Tmax 276.4 279.0 283.5 294.5 219.3 240.6 242.6 248.5 209.1 222.1 229.2 137.9

Figure 3. DSC analysis measured at β = 5 K min–1: a) AN/Mg/NC (top); b) AN/Mg/NC/AC and AN/Mg/NC/AC–CuO mixtures (bottom). The thermal behavior of AN/Mg/NC composite was largely changed by adding 5% of pure AC (Figure 3b: curve 1). There was a significant decrease for both exothermic peaks in comparison with the blank sample (from Tmax = 276.4 °C to Tmax = 219.3 °C). The onset



temperature of the second peak decreases from 232. 5°C to 214.3 °C, if use AC as an additive (heating rate, 5 K/min). Under the effect of AC, the heat release rate (peak height) was also improved from 1.2 mW/mg to 6.4 mW/mg. Also, there is no endothermic peak because evaporation of water was not so apparent due to adsorption properties of AC.36,37 Similar thermal decomposition process of AN/Mg/NC composite can be observed when 5% of AC–CuO was used (Figure 3b: curve 2). The thermal decomposition of AN/Mg/NC composite under the effect of AC–CuO starts with Tonset of 105.3 °C in comparison to 173.0 °C for the pure composite. The DSC parameters show that the addition of AC–CuO leads to faster decomposition rate of the AN/Mg/NC composite than the one under the effect of pure AC. It is shown that the initial decomposition temperature is more than 60 °C lower (209.1 vs. 276.4 °C).

Figure 4. Effect of heating rate on the decomposition of AN/Mg/NC/AC–CuO composite in a nitrogen medium with a flow rate of 300 mlmin−1 in alumina crucibles. Thermal decomposition of the AN/Mg/NC composite in the presence of AC–CuO was conducted at four various heating rates β = 5, 10, 15 and 20 K/min in a nitrogen medium. Figure 4 shows the DCS curves of the AN/Mg/NC/AC–CuO thermal decomposition in the ratio 60/30/5/5 respectively. It is found that with the increasing of heating rate, the composite decomposition temperature weakly shifted to higher temperatures. The presence of AC–CuO reduces the temperature and accelerates the rate of decomposition of AN/Mg/NC composite. These shifts for all investigated samples with onset/offset temperatures and maximum peak temperatures are shown in Table 1 in detail. Figure 5 shows the TG (Thermogravimetry) and DTG (Derivative Thermogravimetry) profiles obtained for the three samples in a nitrogen medium at β = 10 Kmin-1 heating rate.


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Figure 5. TG (a) and DTG (b) curves of the three samples (AN/Mg/NC, AN/Mg/NC/AC and AN/Mg/NC/AC–CuO) in a nitrogen medium (β = 10 K/min) The TG curves showed a continuous mass loss in the temperature range from 60 to 500 °C. The total mass losses measured by TG analysis were around 71%, 74% and 76% w/w of AN/Mg/NC (3), AN/Mg/NC/AC (2) and AN/Mg/NC/AC–CuO (1), respectively. The observed DTG curves have a complex multistep decomposition pathway with more than three processes due to the complicated and multi-component compositions. The residues at the end of TG analysis could mostly be attributed to the remained catalyst, unreacted metal (Mg), and condensed decomposition products of NC and AN. Finally, the TG curves of the samples doped with AC and AC–CuO are different from the blank reference sample with relatively fewer residues due to more complete decomposition. 3.3

Thermal decomposition kinetics

3.3.1 Kinetics by Kissinger method Figure 6 shows thermal decomposition kinetics plots for AN/Mg/NC samples without and with AC or AC–CuO. The correlations of the plots of ln(β/Tp2) vs. 1/Tp are shown in Figure 6. The value of activation energy (Ea) can be determined by multiplication of universal gas constant by the data from the slope of the kinetic plot: ln

( ) = ln( ) ― 𝛽

𝐴𝑅

𝐸𝑎

𝑇2𝑚

𝐸𝑎

𝑅𝑇𝑚

(1)

where ln(β/Tp2) is the logarithm of the heating rate to the square of maximum peak temperature. As it can be seen, plots of ln(β/Tp2) against 1/Tp gives straight lines using peak temperature for the investigated samples, which provides an approximation of -Ea/R and A values from fitted curves. 38,39



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Figure 6. Kinetics plots (ln(β/Tp2) vs. 1/Tp) for the non-isothermal decomposition of AN/Mg/NC composites with and without additives of AC. The kinetic plots suggest that the data could be well fitted with Kissinger Equation (1) to obtain the kinetic parameters, where the correlation for the same AN/Mg/NC/C is the best with higher reliability. The Ea of AN/Mg/NC determined from DSC-TG data by Kissinger method is about 90.1 kJ mol-1 with pre-exponential factor A of 1.5×109, whereas Ea of AN/Mg/NC/AC is about 82.9 kJ mol-1 with A of 1.6×109. In the presence of AC–CuO additive, the value of Ea decreased only by 2 kJ mol-1. In particular, Ea of the AN/Mg/NC decomposition under the effects of AC–CuO is 81.5 kJ mol-1, which is very close to that of AN/Mg/NC/AC composite. The determined kinetic parameters of the observed thermal decomposition of AN/Mg/NC composites are listed in Table 2. Table 2. The kinetic parameters calculated by the Kissinger method Sample AN/Mg/NC This work AN/Mg/NC/AC This work AN/Mg//NC/AC–CuO This work Pure AN Gunawan et al.5 AN and CuO (PSAN) Simoes et al.40 Pure AN Koga et al.41 Pure AN Xu et al.42 Pure AN Brower et al.43

Q, J g−1

R2

48.4

Tmax, oC (β=5K/min) 261.4

A (s-1)

Ea, kJ mol-1

0.9000

ln(β/Tp2) vs. 1/T –10.8327

1.5×109

90.1

54.1

220.4

0.9800

–9.9587

1.6×109

82.9

126.14

209.1

0.9700

–9.8467

1.3×109

81.5

-

293.1

0.9900

-12.8335

4.55×107

102.6

-

242.0

-

-

5.6×105

81.5 ± 0.5

-

260.0

-

-

2.4×106

90.8 ± 0.7

-

278.9

09996

-11.22203

3.02×106

93.3

-

260.0

-

-12.5001

4.1×104

118.0


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It can be seen from Table 2 that the addition of AC and AC–CuO could reduce the thermal decomposition energy barrier of AN/Mg/NC by more than 8 kJ mol-1. Thus, the decomposition with a reaction of AN/Mg/NC would be much easier and faster in the presence of additives. From the results of Ea values, it can be concluded that high surface area of AC loaded with highly active nano-sized CuO has improved catalytic activity compared with pure AC and hence the activation energy of AN/Mg/NC/AC composite is further decreased. In comparison with pure AN, addition of Mg and NC could decrease the Ea due to improved reactivity, as NC could be considered as fuel and AN as oxidizer. By several authors the Ea is observed for decomposition of pure AN and AN with catalysts. According to literature40,41, the Ea of AN under the catalytic effect of CuO could be decreased from 93.3 to 90.8 kJ mol-1 and temperature from 260.0 to 242.0 °C. Overall, the value of 90.1 kJ mol-1 is approximate to the values reported in other works.5,41,44 3.3.2 Kinetics by Friedman method To describe the decomposition process more precisely, one could use a more accurate kinetic evaluation method such as the Friedman isoconversional model45. Based on this method, the basic decomposition kinetic parameters of AN/Mg/NC composites have been obtained at various heating rates. Figure 7 presents a comparison of the dependence of Ea on conversion rate (α) for AN/Mg/NC composite in the presence of pure AC or AC–CuO determined by isoconversional method.

Figure 7. The dependence of Ea on conversion rate for involved materials. (a) DSC curves of AN/Mg/NC composite with pure AC; (b) DSC curves AN/Mg/NC composite with AC doped copper oxide (CuO); Under the effect of AC–CuO catalyst (in comparison with pure AC), the initial Ea of the decomposition process greatly decreases. The Ea of AN/Mg/NC with AC–CuO shows a greatly decreasing of the trend line from α = 0.05 (132 kJ mol-1) to α = 0.05 (57 kJ mol-1), this indicating the catalytic effect CuO particles. In samples with pure AC, the Ea of AN/Mg/NC calculated from DSC curves show a constant trend on all points and Ea of almost independent on the conversion. The samples with pure AC has a constant high Ea value around 192 kJ mol-1. It can



be justified that the AC is inert and has a minor contribution to the heat release of composite thermal decomposition. It's necessary to note that at the decomposition of AN/Mg/NC with pure AC the Ea value has a large spread (25.8 kJ mol-1) near the beginning and the end of the reaction (84.7 kJ mol-1). In comparison, the AN/Mg/NC decomposition in the presence of AC–CuO catalyst, the Ea spread at induction period is approximately smaller (3.2 kJ mol-1) and increase only close to the end of decomposition (8.7 kJ mol-1). It can be seen from Figure 7 and Table 2, in the both of kinetic techniques (Kissinger and Friedman) which were used to determine Ea, the inclusion of pure AC definitely showed lowering of Ea for AN/Mg/NC composite decomposition. 3.4

Combustion of AN/Mg/NC composite with and without AC–CuO

For successful application of EMs, the linear burning rate and the value of pressure exponent should be easily controllable. The value of n must be less than 0.6 for rocket propellants, and higher than 1.0, for gun propellants applications.46 Figure 8 shows the results of combustion experiments: (a) AN/Mg/NC composite (at mass ratio: 60/35/5); (b) an AN/Mg/NC/C (ratio: 60/30/5/5); (c) an AN/Mg/NC/AC–CuO (ratio: 60/30/5/5), at initial pressure p0 = 3.5 MPa in a nitrogen medium.

Figure 8. The flame propagation processes of (a) AN/Mg/NC/AC–CuO, (b) AN/Mg/NC/AC and (c) AN/Mg/NC composites in the combustion chamber at an initial pressure of p0 = 3.5 MPa. Figure 8a shows the combustion wave propagation of the AN/Mg/NC without any additives. The burning rate (rb) of this composite is 10.27 mm s-1 at initial pressure p0 = 3.5 MPa. Combustion occurs with bright light emission related to the fierce burning of magnesium


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particles. Addition of pure AC (Figure 8b) rendered an approximately small effect on the AN/Mg/NC composite combustion behavior, but despite this, the linear burning rate increases up to rb = 17.53 mm s-1 at initial pressure p0 = 3.5 MPa. It is obvious, that the AC promotes the combustion reaction of this composite. The propagation of a combustion front is accompanied by intensive light emission and releasie of a few visible gases. The highest rb was achieved in the samples in presence of AC– CuO catalyst (Figure 8c). Inclusion of catalyst had shown a significant enhancement of the AN/Mg/NC composite combustion behavior. The burning rate has been evidently increased about twice (rb = 20.46 mm s-1) at initial pressure p0 = 3.5 MPa. Figure 9 shows the propagation of combustion wave for the AN/Mg/NC/AC–CuO composite in the chamber at the initial pressures of 1 MPa, 2 MPa and 3 MPa in a nitrogen medium. It is observed that the increase of the initial pressure may enhance the propagation velocity of the combustion wave. At an initial pressure p0 = 1 MPa (Figure 9a), there take place a slowest (rb = 11 mm s-1) uniform combustion with the release of a small amount of visible gases. The increase of the initial pressure to p0 = 2 MPa and 3 MPa (Figure 9b and 9c) enhances the burning rate of AN/Mg/NC/AC–CuO to rb = 14.96 mm s-1 and rb = 17.67 mm s-1, respectively.

Figure 9. Combustion wave propagation in the AN/Mg/NC/AC–CuO: (a) initial pressure p0 = 1 MPa; (b) initial pressure p0 = 2 MPa; (c) initial pressure p0 = 3 MPa. Figure 10 shows comparative data of the linear burning rate as a function of the initial pressure (MPa) for the AN/Mg/NC, AN/Mg/NC/AC and AN/Mg/NC/AC–CuO in a nitrogen medium. In comparison with the initial composite, AN/Mg/NC in the presence of AC burns twice quicker within the whole pressure interval. The highest burning rate (rb = 20.46 mm s-1 at initial pressure p0 = 3.5 MPa) was achieved in the composition in the presence of AC–CuO.



However, the combustion process with or without additives has a low burning rate and pressure exponent (n = 0.53 - 0.42), which is responsible for the low sensitivity to mechanical and shock impacts. A combination of AC with CuO can make the AN/Mg/NC composite burn at a speed of over 20 mm s−1, showing a high value of burning rate coefficient (a = 11.46) and low value of pressure exponent n = 0.42).

Figure 10. Dependencies of the burning rates of the AN/Mg/NC, AN/Mg/NC/AC and AN/Mg/NC/AC–CuO composites on the initial pressure. In summary, it can be assumed that inclusion of AC–CuO in to the content of the composite has improved the combustion characteristics of AN/Mg/NC composite. The effect of AC–CuO on combustion of the composite has a catalytic effect. A catalyst speeds up the burning rate due to the impact on the decomposition pathway of reagents (oxidizer and binder) which undoubtedly plays a certain role in increasing the magnesium oxidation rate and burning rate in total. Also, a large specific surface area, many reaction-capable centers on the surface of pores, defects, high heat transfer properties of AC 27, finally promoted the combustion efficiency of the composite. It can be concluded that addition of AC–CuO allows controlling the linear burning rate and pressure exponent values of the investigated composite. 4 Conclusions The effect of AC–CuO on decomposition and combustion of AN/Mg/NC composite has been investigated using a DSC technique and a high-pressure combustion chamber. The following conclusions could be made: (1) The results show that pure AC affected the both exothermic peaks of AN/Mg/NC decomposition. The onset decomposition temperature of the first peak decreases from 173.0 °C to 107.6 °C. Under the effect of AC–CuO, the decomposition behavior of AN/Mg/NC composite largely changed. The onset decomposition temperature of the first peak decreases


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from 173.0 °C (AN/Mg/NC) to 105.3 °C (AN/Mg//NC/AC–CuO) at 5 K/min heating rate. The improved heat release rate and lowering onset temperature indicated the potential catalytic activity of AC–CuO on AN/Mg/NC thermal decomposition. (2) The Ea and the pre-exponential factor of AN/Mg/NC decomposition were determined to be 90.1 kJ mol-1 and 1.5×109 s-1 without the presence of AC–CuO, and 81.5 kJ mol-1 and 1.3×109 s-1 with AC–CuO. Under the effect of pure AC, the Ea of AN/Mg/NC decomposition decreases up to 7.2 kJmol-1 (Ea = 82.9 kJ mol-1 and A = 1.6×109 s-1). (3) The linear burning rates of AN/Mg/NC composite have reached rb = 17.53 mm s-1 in the presence of pure AC and it is 20.46 mm s-1 for AC–CuO, at initial pressure p0 = 3.5 MPa in high pressure chamber. The burning rate of AN/Mg/NC has been twice enhanced by the catalyst effect. Furthermore, based on the burning rate equation, we can conclude that ACCuO catalyst can adjust the combustion parameters of AN/Mg/NC composite, by changing the burning rate coefficient (a = 5.03 vs. 11.46) and the pressure exponent (n = 0.54 vs. 0.42) values. SUPPORTING INFORMATION The Supporting Information is available free of charge on the ACS Publications website SEM, EDAX and Raman spectra results, Kinetic calculation principals and experimental data. AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (M.K. A.) *E-mail: [email protected]. Phone: +86(029) 88492781. Fax: +86(029) 88492781 (Q.-L.Y.). ORCID M.K. Atamanov: 0000-0003-3028-481X Qi-Long Yan: 0000-0002-9401-5056. ACKNOWLEDGMENTS This work has been supported by the National Natural Science Foundation of China (grant number: 51776176). REFERENCES (1) (2) (3)

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The Catalytic Effect of CuO-doped Activated Carbon on Thermal

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