Enhanced Thermal Decomposition Properties of CL-20 through Space

Subscriber access provided by Queen Mary, University of London

Article

Enhanced Thermal Decomposition Properties of CL-20 through SpaceConfining in Three-Dimensional Hierarchically Ordered Porous Carbon Jin Chen, Simin He, Bing Huang, Peng Wu, Zhiqiang Qiao, Jun Wang, Liyuan Zhang, Guangcheng Yang, and Hui Huang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b00287 • Publication Date (Web): 08 Mar 2017 Downloaded from http://pubs.acs.org on March 10, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

1

Enhanced Thermal Decomposition Properties of CL-

2

20 through Space-Confining in Three-Dimensional

3

Hierarchically Ordered Porous Carbon

4

Jin Chen, Simin He, Bing Huang, Peng Wu, Zhiqiang Qiao, Jun Wang, Liyuan Zhang,

5

Guangcheng Yang *, and Hui Huang*

6

Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900,

7

China

8

KEYWORDS: CL-20, Thermal decomposition properties, Catalysts, 3D hierarchically ordered

9

porous carbon, Nanocomposites

10

ABSTRACT: High energy and low signature properties are the future trend of solid propellants

11

development. As a new and promising oxidizer, hexanitrohexaazaisowurtzitane (CL-20) is

12

expected to replace the conventional oxidizer ammonium perchlorate (AP) to reach above goals.

13

However, the high pressure exponent of CL-20 hinders its application in solid propellants so that

14

the development of effective catalysts to improve the thermal decomposition properties of CL-20

15

still remains challenging. Here, 3D hierarchically ordered porous carbon (3D HOPC) is

16

presented as catalyst for the thermal decomposition of CL-20 via synthesizing a series of

17

nanostructured CL-20/HOPC composites. In these nanocomposites, CL-20 is homogeneously

18

space-confined into 3D HOPC scaffold as nanocrystals of 9.2-26.5 nm in diameter. The effect of

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 26

19

the pore textural parameters and surface modification of 3D HOPC, as well as CL-20 loading

20

amount on the thermal decomposition of CL-20 is discussed. A significant improvement of the

21

thermal decomposition properties of CL-20 is achieved with remarkable decrease in

22

decomposition peak temperature (from 247.0 to 174.8 °C) and activation energy (from 165.5 to

23

115.3 kJ/mol). The exceptional performance of 3D HOPC could be attributed to its well-

24

connected 3D hierarchically ordered porous structure, high surface area and the confined CL-20

25

nanocrystals. This work clearly demonstrates that 3D HOPC is a superior catalyst for CL-20

26

thermal decomposition, and would open new potential for further applications of CL-20 in solid

27

propellants.

28

INTRODUCTION

29

Composite solid propellants (CSPs) are attractive in the applications of propulsion for tactical

30

missiles, attitude control systems and pressure generators.1-2 The most widely used oxidizer,

31

ammonium perchlorate (AP), for CSPs, now hardly meet the requirements of high energy output

32

and low signature properties for solid propellants due to its low heat release (~ 574.2 J/g), high

33

signature and corrosive products (such as HCl, Cl2) generated during the thermal decomposition

34

process.3-6 It is therefore urgent to find more energetic and environmentally friendly oxidizers for

35

the further development of solid propellants.

36

Hexanitrohexaazaisowurtzitane (CL-20, C6H6N12O12), a three-dimensional caged structure

37

polycyclic nitramine (Figure S1), is the highest energy molecular explosive known to date.7 Due

38

to its high energy output (1500 ± 300 J/g) and halogen-free molecular structure, CL-20 is likely

39

to replace AP to improve the energy and burning rate of solid propellants with minimum

40

signature properties. However, the high pressure exponent caused by the high content of

41

nitramine explosives, may affect the steady-state combustion process of these propellants, and


2

Page 3 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


42

thus, further hinder the application of CL-20 in solid propellants.8-9 It has been reported that the

43

addition of efficient catalysts into oxidizers can decrease the thermal decomposition temperature

44

so that the burning rate can be enhanced and the pressure exponent of solid propellants is

45

reduced as well.10-12 Currently, only few catalysts have been exploited for CL-20 due to its

46

complex multi-step decomposition process, such as organometallic salts, nano-metal oxide,

47

carbon black, carbon nanotubes, etc.13-15 These catalysts are only with decreasing decomposition

48

peak temperature of 2-8 °C and activation energy of 6-12 kJ/mol, and thus, with limited

49

performance. The reason lies in that the lower contact area between the catalysts and the larger

50

particles of CL-20, or less catalytic active sites leads to insufficient reactions. As a result, one of

51

the primary concerns associated with CL-20-based solid propellants is to explore a novel catalyst

52

with higher activity for CL-20 thermal decomposition.

53

Recently, 3D hierarchically ordered porous carbon (3D HOPC) is attractive for catalyst due to

54

their highly ordered porous structure, high surface area, large pore volume, open pore structure,

55

as well as good thermal conductivity. Its multiscale (micro/meso/macro) pores and

56

interconnected framework not only endow this material with plentiful exposed catalytic active

57

sites for the adsorption of reactant during the thermal catalytic process,16-19 but also effect the

58

propagation of the diffusion-controlled exothermic reaction via shortened diffusion paths.20 More

59

importantly, 3D HOPC can impregnate and confine CL-20 into its porous channels to maintain

60

the nanoscale particles during thermal catalytic process.21-25 The nanosized CL-20 presents a

61

higher decomposition rate and a lower decomposition temperature compared with those of larger

62

size.26-28 The above advantages of 3D HOPC may improve the kinetics of CL-20 thermal

63

decomposition at some extents, which is expected to solve the problem existing in the

64

development of CL-20-based solid propellants.


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 26

65

Herein, 3D HOPC is used as a novel catalyst for improving the thermal decomposition

66

properties of CL-20 via synthesizing nanostructured CL-20/HOPC composites. The focus is then

67

on the thermal catalytic performance of 3D HOPC for CL-20 thermal decomposition. To the best

68

of our knowledge, 3D HOPC has never been employed as the catalyst to study the thermal

69

decomposition behavior of oxidizers in solid propellants. In this work, the effect of the pore

70

textural parameters and surface modification of 3D HOPC, as well as CL-20 loading amount on

71

CL-20 thermal decomposition is discussed. For the 3D hierarchical ordered porous structure and

72

the confined CL-20, a significant improvement of the thermal decomposition properties of CL-

73

20 has been achieved. It can be foreseen that 3D HOPC will be a promising catalyst for CL-20-

74

based solid propellants. By taking advantage of 3D HOPC, this concept can be extended to

75

explore high-performance carbon-based catalysts for nitramine explosives based solid

76

propellants.

77

EXPERIMENTAL SECTION

78

Materials. Triblock copolymer Pluronic F127 (EO106PO70EO106, Mw=12600) was purchased

79

from Sigma-Aldrich. Phenol, formaldehyde (37 wt.%), NaOH, tetraethyl orthosilicate (TEOS),

80

ethanol, aqueous ammonia (28 wt.%), hydrofluoric acid, concentrated nitric acid, hydrogen

81

peroxide and acetone were purchased from Sinopharm Chemical Reagent Co. Ltd. CL-20 was

82

provided by Institute of Chemical Materials (ICM), China. All chemicals were analytical grade

83

and used as received without further purification. Deionized water was used in all experiments.

84

The 20 wt.% resol solution in ethanol was prepared by a basic polymerization method.29

85

Preparation of 3D HOPC. 3D hierarchically ordered macro-/mesoporous carbon materials

86

were prepared through a dual-templating approach with silica colloidal crystals as the template,

87

F127 as the structure-directing agents, and resol as the carbon source.29 In brief, firstly,


4

Page 5 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


88

monodisperse silica microspheres were prepared by using the Stöber’s method,30 and then after

89

sedimentation for few days to form silica colloidal crystals. Secondly, a piece of colloidal crystal

90

monolith was immersed in a homogeneous ethanol solution of resol and F127 (mass ratio:

91

resol/F127/ethanol = 2:1:10) for 24 h at 25 °C. After the evaporation of ethanol, the composite

92

monolith was heated at 70 °C for 4 h to further polymerize resol. Finally, the resulting

93

silica/PF/F127 composite was calcined in N2 at 600 °C for 3 h using a heating rate of 3 °C/min to

94

decompose F127. And then the silica was removed by treated with HF solution (10 wt.%). After

95

washing with water and drying at 60 °C in vacuum, the 3D HOPC with macroporosity and

96

mesoporosity was obtained. For comparison, a series of 3D HOPC with different pore textural

97

parameters were prepared by using silica colloidal crystals with mean diameters of 180 nm, 305

98

nm and 430 nm, and were named C-180, C-305 and C-430, respectively.

99

Surface Modification of 3D HOPC. As previously reported, surface oxygen-containing

100

groups within carbon scaffolds present obvious effect on the adsorption process of multi-nitro

101

compounds,31 therefore C-305 sample was treated with oxidative agents for facile introduction of

102

oxygen-containing groups.32 Typically, 100 mg of C-305 sample was treated with mixed solution

103

of concentrated nitric acid (10 mL) and H2O2 (3 mL) in a Teflon autoclave by heating at 60 °C

104

for 30 min. Then, the resulting sample was washed thoroughly with deionized water until the pH

105

was close to 7.0. The obtained product was further dried in vacuum at 80 °C for 24 h and named

106

C-305A.

107

Preparation of CL-20/HOPC Nanocomposites. The CL-20/HOPC nanocomposites were

108

prepared via a solvent evaporation-induced dispersion process.33 For a typical process (Scheme

109

1a), an acetone solution (5 mL) of CL-20 (85 mg) was stirred for 5 min at room temperature with

110

adding 50 mg of 3D HOPC. After that the mixture was left undisturbed at room temperature for


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 26

111

about 4 h to evaporate the solvent. The final product was black solid and dried at 60 °C in

112

vacuum. For comparison, different loadings could be achieved by controlling the ratio of CL-20

113

to 3D HOPC, and the samples were denoted X-1, X-2 and X-3, in which X represented 3D

114

HOPC, and the weight percent of CL-20 in nanocomposites determined by TG analysis were

115

approximately 30 %, 50 % and 60 %, respectively.

116

Characterization and Analysis. The structure and morphology of the as-prepared 3D HOPC

117

and nanocomposites were examined by X-ray diffraction (XRD, Bruker D8 Advance with Cu Kα

118

radiation), field-emission scanning electron microscopy (FESEM, ZEISS SIGMA HD) and

119

transmission electron microscopy (TEM, JEOL 2011). Elemental composition analysis was

120

performed with energy dispersive X-ray spectroscopy (EDS). Nitrogen sorption isotherms were

121

measured at 77 K with a Quantachrome NovaWin analyzer after the samples were degassed in a

122

vacuum at 100 °C for at least 6 h. The specific surface areas (SBET) was estimated by Brunauer-

123

Emmett-Teller (BET) method. The pore volumes and pore size distributions were derived from

124

the adsorption branches of isotherms by using the Barret-Joyner-Halenda (BJH) model, and the

125

total pore volumes (Vt) were determined from the adsorbed amount at P/P0 of 0.988. Fourier

126

transform infrared (FT-IR) spectra were recorded on a Nicolet 6700 Fourier spectrophotometer

127

by using KBr pellets of the solid samples. The catalytic activity of 3D HOPC for CL-20 thermal

128

decomposition was determined by differential scanning calorimetry-thermogravimetry analyses

129

(DSC/TG) using a NETZSCH STA 449C simultaneous thermal analyzer in N2 atmosphere over

130

the temperature range of 50-400 °C with heating rate of 2, 5, 10, 20 °C /min.


6

Page 7 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


131 132

Scheme 1. Schematic illustration for (a) the preparation of CL-20/HOPC nanocomposites, and (b)

133

the proposed thermal decomposition process of CL-20 inside 3D HOPC scaffold

134

RESULTS AND DISCUSSION

135

FESEM and TEM images (Figure 1a and S2a-c) clearly reveal that the synthesized carbon

136

materials exhibit a 3D hierarchical ordered porous structure, arrayed with face cubic centered

137

structure of macropores (170-410 nm). All the macropores are well-connected to each other by

138

small windows (25-52 nm marked by arrows) caused by the contact area between neighboring

139

silica microspheres after the sintering process and are surrounded by numerous spherical

140

mesopores. In order to study the influence of surface modification on the CL-20 loading and its

141

thermal properties, C-305 sample was treated with HNO3 and H2O2 mixed solution. Although

142

some pore walls are slightly etched, the obtained C-305A sample still displays a well-retained

143

3D hierarchical ordered porous structure after oxidative treatment (Figure S2c). Notably, C-305


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 26

144

sample exhibits the highly ordered porous structure and best pore connectivity among the four

145

samples. a

b

e

Windows

c

d

146 147

Figure 1. FESEM images of (a) C-305, (b) C-305-1, (c) C-305-2 and (d) C-305-3, the inseted

148

TEM images in (a) show the carbon mesostructures. (e) Elemental mapping of C-305-3.

149

FT-IR spectra (Figure S3) were utilized to monitor the introduced oxygen-containing groups

150

on the surface of the C-305A sample. It was clearly seen that several new bands appear after

151

oxidative treatment. First, the weak bands in the region of 1680-1730 cm-1 denote the absorption

152

of stretching and bending vibration of -COOH groups, and the absorption around 1180 cm-1 is

153

caused by the stretching vibration of C-O bonds.34 Second, the band at 1384 cm-1 can be ascribed

154

to carboxyl-carbonate structures.35 Finally, the new bands at 1244 and 1342 cm-1 can be assigned

155

to C-O-C vibrations in ether structures or other single bonded oxo group C-O-R.36 These results

156

indicate that abundant oxygen-containing groups are created in the carbon framework by the

157

oxidative treatment.


8

Page 9 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


158

High-resolution scanning electron microscope observations (Figure 1b-d and S2d-f) show that

159

CL-20 is homogeneously supported on pore walls, and the pores inside the 3D HOPC become

160

small and less with the increase of the loading amount. More evident filling effect is observed in

161

the C-305A-3 sample (Figure S2f), due to the high concentration of surface oxygen-containing

162

groups within C-305A framework which is favor to adsorb the multi-nitro compounds by

163

hydrogen bonds.31 It is worth noting that no obvious aggregation of CL-20 is observed outside

164

the surface of the scaffolds, confirming the successful confinement of CL-20 into the 3D HOPC

165

scaffold at the nanoscale. The mapping image of N element with a continuous distribution

166

further evidences the homogeneous dispersion of CL-20 in the carbon framework (Figure 1e).

167

High dispersion can result in compact interfacial contact and strong interaction between CL-20

168

and the 3D HOPC, which is favored for the thermal catalytic reaction.

169

The pore textural parameters of 3D HOPC and confined CL-20 are generally considered to be

170

two important factors associated with the thermal catalytic performance of 3D HOPC, which

171

have been examined by nitrogen adsorption-desorption isotherms (Figure 2 and S4). The as-

172

prepared 3D HOPC shows typical type IV curves with pronounced H2-type hysteresis loop,

173

being the characteristic of mesopores (9.4-14.8 nm). The small amounts of N2 adsorbed at low

174

relative pressure region suggest the existence of micropores, and the hysteresis loop tails at the

175

region of high relative pressure (P/P0 > 0.95) is ascribed to macropores.37 All the 3D HOPC

176

samples possess high BET surface area (574-1061 m2/g) and large pore volume (0.86-1.76 cm3/g)

177

(Table S1), implying that they may have high catalytic activity. Particularly, the BET surface

178

area and pore volume of C-305A are both lower than those of C-305 after oxidative treatment.

179

Loading CL-20 into 3D HOPC was also studied by nitrogen sorption isotherms. With the

180

increase of the loading amount of CL-20, the N2 sorption amount and mean pore size of CL-


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 26

181

20/HOPC nanocomposites obviously decrease (Figure 2). When the loading amount increases to

182

60 wt.%, the isotherm shows very weak step in the range of capillary condensation, the BET

183

surface area and pore volume also decrease to 65-213 m2/g and 0.23-0.39 cm3/g, respectively

184

(Table S1). The results imply that the micropores and mesopores of 3D HOPC are almost fully

185

filled by CL-20 nanocrystals. a

b

186 187

Figure 2. N2 adsorption-desorption isotherms (a) and pore size distributions (b) of C-305 and its

188

nanocomposites with CL-20.

189

The formation of CL-20 nanocrystals within 3D HOPC was further confirmed by XRD (Figure

190

3a). There is no obvious peak in the diffraction pattern of 3D HOPC scaffold, implying its

191

amorphous structure. After impregnation, the broadening diffraction peaks are observed for all

192

composites, suggesting the formation of CL-20 nanocrystals. The average particle sizes of CL-20

193

nanocrystals in the confining environment (calculated from Scherrer equation) are in the range of

194

9.2-26.5 nm, much smaller than the previously reported CL-20 nanoparticles.26-28 Note that the

195

size of CL-20 nanocrystals is affected by the macropore size of 3D HOPC and the loading

196

amount of CL-20 (Figure 3b). As the macropore size or/and the loading amount decrease, the

197

size of CL-20 nanocrystals decreases and the decomposition rate increases. Moreover, C-305A-3


10

Page 11 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


198

has the largest CL-20 nanocrystals for the adsorption of the high concentration of surface

199

oxygen-containing groups. a

b

200 201

Figure 3. (a) XRD patterns of raw CL-20, 3D HOPC scaffold and CL-20/HOPC nanocomposites.

202

(b) The average particle sizes of CL-20 nanocrystals under different loading amount and 3D

203

HOPC scaffold.

204

According to FESEM, nitrogen sorption and XRD analysis, we can speculate that the loading

205

of CL-20 inside 3D HOPC scaffold has undergone the following process (Scheme 1a): CL-20

206

acetone solution enters into the carbon scaffold by capillary forces. With the solvent evaporation-

207

induced dispersion process, CL-20 can disperse throughout the whole scaffold and form the

208

nanocrystals. There is a hydrogen bond interaction between the CL-20 molecule and the surface

209

oxygen-containing groups within 3D HOPC scaffold.20 For low CL-20 loading amount,

210

nanocrystals will firstly fill in the micropores and mesopores, but still leave a lot of free space for

211

mesopores. With the increase of the loading amount of CL-20, the nanocrystals gradually grow

212

and almost fill the mesopores, and eventually, have the tendency of outward growth. When the

213

loading amount increases to about 60 wt.%, the nanocrystals grow outside of the mesopores and

214

a continuous CL-20 thin layer is formed on the surface of macropore walls. Throughout the


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 26

215

loading process, CL-20 is really confined in 3D HOPC scaffold at the nanometer scale. It is

216

obvious that the surface modified 3D HOPC scaffold is favorable for CL-20 loading due to the

217

presence of a large number of surface oxygen groups.

218

The thermal catalytic activity of 3D HOPC was first examined by DSC/TG at the heating rate

219

of 10 °C /min. As shown in Figure 4a and Table 1 for all CL-20/HOPC nanocomposites, the

220

decomposition peak temperature decrease by 27.8-72.2 °C compared with that of raw CL-20

221

(247 °C), indicating the pronounced thermal catalytic activity of 3D HOPC for CL-20

222

decomposition. These values are much better than those of reported catalysts.13-15 For the same

223

loading amount, the peak temperatures of CL-20 decomposition shift from 214.3 °C to 201.6 °C

224

with the decreasing macropore size of 3D HOPC scaffold from 430 nm to 180 nm. The C-305A-

225

3 presents a higher peak temperature, 219.2 °C, than that of the 205.5 °C of C-305-3. The peak

226

temperatures are also reduced with decreasing loading amount in the same C-305 scaffold. As

227

loading amount decrease from 60 wt.% for C-305-3, to 30 wt.% for C-305-1, the peak

228

temperatures fall from 205.5 °C to 174.8 °C. These results suggest that the thermal catalytic

229

performance of 3D HOPC are influenced both by their surface area and crystal size of confined

230

CL-20, and follow the order of C-305-1 > C-305-2 > C-180-3 > C-305-3 > C-430-3 > C-305A-3.

231

The same trend has been observed for their surface area and crystal size of confined CL-20 listed

232

in Table S1. It can be explained by the fact that the high surface area can offer abundant catalytic

233

sites for accelerating thermal catalytic reactions, and the nanoscaled crystals can make the

234

molecules more active to decomposition at lower temperature. The exothermic enthalpies (ΔH)

235

of CL-20 decomposition reaction with 3D HOPC are demonstrated in Table 1. A clear trend can

236

be observed that ΔH decreases with the participation of 3D HOPC scaffold as compared to raw

237

CL-20 (1796.4 J/g), and increases with the increasing CL-20 crystal size, from 469.6 J/g for C-


12

Page 13 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


238

305-1, to 1189.2 J/g for C-305A-3. Moreover, the decomposition process of CL-20 with 3D

239

HOPC as catalyst had also been studied by TG measurement, as shown in Figure 4b. The weight

240

loss of CL-20/HOPC nanocomposites take place below 170 °C, while that of raw CL-20 is about

241

220 °C, indicating the apparent catalytic activity of 3D HOPC for CL-20 thermal decomposition,

242

in agreement with their DSC results. Furthermore, the existence of 3D HOPC scaffold did not

243

change the thermal decomposition mechanism of CL-20 for the similar TG curve of raw CL-20

244

and nanocomposites. b

a

245 246

Figure 4. (a) DSC and (b) TG curves of raw CL-20 and CL-20/HOPC nanocomposites at the

247

heating rate of 10 oC/min.

248

To further understand the catalytic performance of 3D HOPC for CL-20 thermal

249

decomposition, raw CL-20 and CL-20/HOPC nanocomposites were investigated by DSC/TG at

250

different heating rates from 2 to 20 °C /min, respectively. As shown in Figure 5 and Table 1, the

251

decomposition temperature of raw CL-20 and nanocomposites is dependent on the heating rate

252

and a slight increase in the temperature is accompanied with the increase of heating rate. Taking

253

C-305-3 as an example, the analysis results show that the peak temperature increases gradually


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 26

254

from 185.7 °C for 2 °C /min, to 196.1 °C for 5 °C /min, 205.5 °C for 10 °C /min and 215.5 °C

255

for 20 °C /min, respectively.

256

To obtain the kinetic parameters of thermal decomposition reaction, including activation

257

energy (Ea) and pre-exponential factor (A), Kissinger’s Eq (1) and Ozawa’s Eq (2)38 are cited and

258

the results are shown in Table 1.

259

   AR Ea 1 In 2   In  T  Ea R Tp  p 

260

 AEa  E   2.315  0.4567 a lg   lg RT  RG   

(1)

(2)

261

Where T is the absolute temperature in the unit of K, Ea is the apparent activation energy in the

262

unit of kJ/mol, β is the heating rate in the unit of K/min, R is the ideal gas constant, 8.314

263

J/mol·K, Tp is the peak temperature at β in the unit of K, A is pre-exponential factor, α is the

264

extent of conversion in %.


14

Page 15 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


a

b

c

d

e

f

g

h

265 266

Figure 5. DSC curves of (a) raw CL-20, (b) C-305-1, (c) C-305-2, (d) C-305-3, (e) C-305A-3, (f)

267

C-180-3 and (g) C-430-3 at different heating rates. (h) Decomposition peak temperature (10

268

o

C/min) and activation energy of raw CL-20 and CL-20/HOPC nanocomposites.

269

In Kissinger method, the term ln(β/Tp2) varies linearly with 1/T. The activation energy Ea and

270

the pre-exponential factor A can be calculated from the slope of -Ea/R and intercept, respectively.

271

In Ozawa method, there is the approximate same α on the Tp at different heating rate, so Ea and A

272

are derived from the linear relationship between lg(β) and 1/T.

273

Table 1. Comparison of Kinetic Parameters for Raw CL-20 and CL-20/HOPC Nanocomposites

274

at Different Heating Rates in DSC Experiments


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Tp (oC) at β (K/min) sample

Kissinger method

Page 16 of 26

Ozawa method

ΔH (J/g)

2

5

10

20

Ea (kJ/mol)

InA (min-1)

r

Ea (kJ/mol)

r

CL-20

229.0

240.3

247.0

258.9

165.6

33.9

0.9852

166.7

0.9861

1796.4

C-305-1

154.0

168.7

174.8

184.9

115.3

26.5

0.9802

118.2

0.9820

469.6

C-305-2

175.2

185.8

196.9

205.1

126.5

27.9

0.9934

126.9

0.9939

986.0

C-305-3

185.7

196.1

205.5

215.5

135.9

29.8

0.9969

136.4

0.9973

1035.0

C-305A-3

198.8

212.9

219.2

225.9

156.3

33.8

0.9843

156.3

0.9872

1189.2

C-180-3

186.1

195.3

201.6

211.3

163.7

37.2

0.9896

162.8

0.9910

1003.2

C-430-3

195.7

207.1

214.3

222.1

160.9

35.4

0.9950

160.0

0.9955

1069.3

at 10

oC/min

275 276

From Table 1 and Figure S5, it can be seen that the values of Ea obtained by Kissinger method

277

are in good agreement with that obtained by Ozawa’s method, and all the linear correlation

278

coefficients are close to 1, indicating reliable results. For raw CL-20, the activation energy was

279

calculated to be 165.6 kJ/mol, close to the value of previously reported.39 In the presence of CL-

280

20/HOPC nanocomposites, the activation energy of CL-20 decomposition decrease to 115.3-

281

163.7 kJ/mol, implying their improved thermal decomposition kinetics. Furthermore, the values

282

of pre-exponential factor should also be considered to describe the decomposition process, and

283

they increase in order C-305-1 < C-305-2 < C-305-3 < C-305A-3 < C-430-3 < C-180-3. Usually,

284

a smaller value of InA means better catalytic activity of the catalysts. Based on the results of

285

activation energies and pre-exponential factors, it can be deduced that the catalytic performance

286

of 3D HOPC follow the order of C-305-1 > C-305-2 > C-305-3 > C-305A-3 > C-430-3 > C-180-

287

3, in which C-305A-3 has a higher catalytic activity and C-180-3 presents the lowest catalytic

288

activity. This conclusion is slightly different from the previous DSC analysis at the heating rate

289

of 10 °C/min (Figure 5h), indicating that there are other factors contributed to the high activity of

290

3D HOPC in addition to their high surface area and confined CL-20 nanocrystals. Meanwhile,


16

Page 17 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


291

the TG results are also calculated by ASTM E1641 method40 to determine the thermal kinetic

292

parameters of CL-20 and CL-20/HOPC nanocomposites. Activation energies and pre-

293

exponential factors are derived from the Inβ versus 1/T curves, where T is the temperature at

294

constant conversion. As shown in Table S2, the values of Ea and InA exhibit the same variation

295

trend with above DSC results.

296

To gain further insight into the mechanism of the thermal catalytic reaction, the supposed

297

procedure for the decomposition process of CL-20 inside 3D HOPC scaffold is schematically

298

illustrated in Figure 1b. As far as we know, the dominating decomposition reaction of CL-20 is

299

the homolytic cleavage of the N-NO2 bonds, and NO2 is the most significant decomposition

300

product.40 The 3D hierarchically ordered porous structure is beneficial to the fast diffusion of

301

NO2 through the whole scaffold and the reaction between NO2 and active sites in the pore walls,

302

because the macropores interconnected by large windows can provide efficient mass

303

transportation and accessibility, while the micro-/mesopores serve as branched channels to

304

increase the diffusion rate for gaseous molecules. This process may promote the homolysis of the

305

N-NO2 bonds via reducing the concentration of NO2, and a mass of heat released from the

306

reaction of NO2 and 3D HOPC can accelerate the decomposition of residual CL-20 and ensure

307

the continuation of the decomposition. So that the whole thermal decomposition reaction of CL-

308

20/HOPC nanocomposites shifts to low temperature, and the peak temperature and activation

309

energy decrease as well. Moreover, the porous network of 3D HOPC scaffold can significantly

310

suppress the escape of NO2, thus allowing it sufficiently reacts with carbon scaffold. However,

311

the existence of carbon scaffold has broken the original oxygen balance of CL-20 and weakened

312

the catalytic action of NO2 on CL-20, so that the decomposition of the whole CL-20 molecule is

313

insufficient, and then the heat release of CL-20/HOPC nanocomposites decrease as compared to


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 26

314

raw CL-20. Consequently, the 3D hierarchically ordered porous structure also contributes to the

315

catalytic performance of 3D HOPC for CL-20 thermal decomposition. Highly ordered porous

316

structure and good pore connectivity mean remarkable catalytic activity. From the previous

317

FESEM and TEM analysis, it can be seen that C-305, even C-305A, possess the highly ordered

318

porous structure and good pore connectivity, which resulting in a lower activation energy for C-

319

305-1, C-305-2, C-305-3 and C-305A-3. By contrast, C-180-3 has higher activation energy

320

because of its poor ordered porous structure and pore connectivity.

321

On the basis of the aforementioned results, the superior thermal catalytic performance of 3D

322

HOPC are attributed to the following factors: 1) its highly ordered porous structure and good

323

pore connectivity can minimize the diffusion resistance to facilitate the efficient transfer of NO2;

324

2) its high surface area and 3D hierarchically porous structure provide plenty of exposed reactive

325

sites for NO2 adsorption or reaction during the thermal catalytic process; 3) the CL-20

326

nanocrystals confined in its porous channels resulting in a higher decomposition rate and a lower

327

decomposition temperature; 4) its outstanding thermal conductivity is beneficial to the heat

328

transfer during the decomposition process of CL-20. Nevertheless, although the surface

329

modification such as oxidative treatment can introduce a large number of oxygen-containing

330

groups to promote the CL-20 loading, the formation of larger CL-20 nanocrystals and the

331

decrease of the specific surface area and pore connectivity caused by structural damage can

332

weaken the catalytic performance of 3D HOPC.

333

CONCLUSION

334

In summary, a highly active and efficient catalyst, 3D HOPC, has been proposed for the

335

thermal decomposition of CL-20 via synthesizing nanostructured CL-20/HOPC composites. A

336

significant improvement of the thermal decomposition properties of CL-20 is achieved with


18

Page 19 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


337

remarkable decrease in decomposition peak temperature (from 247.0 to 174.8 °C) and activation

338

energy (from 165.5 to 115.3 kJ/mol). The outstanding performance of 3D HOPC results from its

339

well-connected 3D hierarchically ordered porous structure, high surface area and the confined

340

CL-20 nanocrystals. All these features indicate that 3D HOPC is an attractive catalyst for the

341

thermal decomposition of CL-20. This work should get deep insights into the role of 3D

342

hierarchically ordered porous structure in thermal catalysis of CL-20 decomposition, and

343

conceptually provides a new insight for designing high-performance carbon-based catalysts for

344

nitramine explosives based solid propellants.

345

ASSOCIATED CONTENT

346

Supporting Information.

347

The following files are available free of charge.

348

Molecular structure of CL-20; TEM images of C-180, C-305A and C-430; FESEM images, N2

349

sorption isotherms and pore size distributions of C-180, C-305A, C-430 and their

350

nanocomposites with CL-20; FT-IR spectra of C-305 and C-305A; Pore textural parameters of

351

3D HOPC materials and CL-20/HOPC nanocomposites; Dimension of the confined CL-20

352

nanocrytals; Dependence of ln(β/Tp2) on 1/Tp and kinetic parameters at the 30% conversion in

353

TG experiments for raw CL-20 and CL-20/HOPC nanocomposites (PDF).

354

AUTHOR INFORMATION

355

Corresponding Authors

356

*E-mail [email protected] (G. Y); Tel +86 816 2480353

357

*E-mail [email protected] (H. H)


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

358

Notes

359

The authors declare no competing financial interest.

360

ACKNOWLEDGMENT

361

Page 20 of 26

This work was supported by the National Science Foundation of China (11372288, 11502242

362

and 11502247).

363

REFERENCES

364

(1) Shioya, S.; Kohga, M.; Naya, T. Burning Characteristics of Ammonium Perchlorate-Based

365

Composite Propellant Supplemented with Diatomaceous Earth. Combust. Flame 2014, 161, 620-

366

630.

367

(2) Zhang, W. J.; Li, P.; Xu, H. B.; Sun, R. D.; Qing, P.H.; Zhang, Y. Thermal Decomposition

368

of Ammonium Perchlorate in the Presence of Al(OH)3·Cr(OH)3 Nanoparticles. J. Hazard. Mater.

369

2014, 268, 273-280.

370 371 372 373

(3) Boldyrev, V. V. Thermal Decomposition of Ammonium Perchlorate. Thermochim. Acta 2006, 443, 1-36. (4) Mallick, L.; Kumar, S.; Chowdhury, A. Thermal Decomposition of Ammonium Perchlorate: A TGA–FTIR–MS Study. Thermochim. Acta 2015, 610, 57-68.

374

(5) Wang, J.; Qiao, Z. Q.; Zhang, L.; Shen, J. P.; Li, R.; Yang, G. C.; Nie, F. D. Controlled

375

Synthesis of Co3O4 Single-Crystalline Nanofilms Enclosed by (111) Facets and Their

376

Exceptional

377

CrystEngComm 2014, 16, 8673-8677.

Activity

for

the

Catalytic

Decomposition


of

Ammonium

Perchlorate.

20

Page 21 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


378

(6) Zhao, Y. J.; Zhang, X. W.; Xu, X. M.; Zhao, Y. Z.; Zhou, H. P.; Li, J. B.; Jin, H. B.

379

Synthesis of NiO Nanostructures and Their Catalytic Activity in the Thermal Decomposition of

380

Ammonium Perchlorate. CrystEngComm 2016, 18, 4836-4843.

381 382 383 384

(7) Lee, J. S.; Jaw, K. S. Thermal Decomposition Properties and Compatibility of CL-20, NTO with Silicone Rubber. J. Therm. Anal. Cal. 2006, 85, 463-467. (8) Bazaki, H.; Kawabe, H.; Miya, H.; Kodama, T. Synthesis and Sensitivity of Hexanitrohexaazaisowurtzitane (HNIW). Propellants, Explos., Pyrotech. 1998, 23, 333-336.

385

(9) Divekar, C. N.; Sanghavi, R. R.; Nair, U. R.; Chakraborthy, T. K.; Sikder, A. K.; Singh, A.

386

Closed-Vessel and Thermal Studies on Triple-Base Gun Propellants Containing CL-20. J.

387

Propul. Power 2010, 26, 120-124.

388

(10) Fu, T. M.; Chen, W. F.; Gu, Z. M.; Liu, L.; Li, F. S.. Preparation of CuO Modified SBA-

389

15 and Applications as Catalyst in AP-HTPB Solid State Propellants. Combust. Sci. Technol.

390

2009, 181, 892-901.

391

(11) Singh, G.; Kapoor, I. P. S.; Dubey, R.; Srivastava, P. Preparation, Characterization and

392

Catalytic Behavior of CdFe2O4 and Cd Nanocrystals on AP, HTPB and Composite Solid

393

Propellants. Thermochim. Acta 2010, 511, 112-118.

394

(12) Styborski, J. A.; Scorza, M. J.; Smith, M. N.; Oehlschlaeger, M. A. Iron Nanoparticle

395

Additives as Burning Rate Enhancers in AP/HTPB Composite Propellants. Propellants, Explos.,

396

Pyrotech. 2015, 40, 253-259.

397 398

(13) Yang, R. J.; An, H. M.; Tan, H. M. Combustion and Thermal Decomposition of HNIW and HTPB/HNIW Propellants with Additives. Combust. Flame 2003, 135, 463-473.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

399 400

Page 22 of 26

(14) Yu, X. F. The Effect of Carbon Nanotubes on the Thermal Decomposition of CL-20. Chin. J. Explos. Propellants 2004, 27, 78-80.

401

(15) Liu, J. B.; Zhao, N. N.; Zhao, F. Q.; Song, J. R.; Ma, H. X. Preparation of Sea Urchin-

402

shaped Nano-MnO2 and Its Effect on Thermal Decomposition Performance of CL-20. Chin. J.

403

Explos. and Propellants 2015, 38, 19-24.

404

(16) Deng, C. W.; Zhong, H. X.; Li, X. F.; Yao, L.; Zhang H. M. A Highly Effecient

405

Electrocatalyst for Oxygen Reduction Reaction: Phosphorus and Nitrogen Co-doped

406

Hierarchically Ordered Porous Carbon Derived from an Iron-Functionalized Polumer. Nanoscale

407

2016, 8, 1580-1587.

408

(17) Luo, W.; Zhao, T.; Li, Y. H.; Wei, J.; Xu, P. C.; Li, X. X.; Wang, Y. W.; Zhang, W. Q.;

409

Elzatahry, A. A.; Alghamdi, A.; Deng, Y. H.; Wang, L. J.; Jiang, W.; Liu, Y.; Kong, B.; Zhao, D.

410

Y. A Micelle Fusion–Aggregation Assembly Approach to Mesoporous Carbon Materials with

411

Rich Active Sites for Ultrasensitive Ammonia Sensing. J. Am. Chem. Soc. 2016, 138, 12586-

412

12595.

413 414

(18) You, B.; Jiang, J. H.; Fan, S. J. Three-Dimensional Hierarchically Porous All-Carbon Foams for Supercapacitor. ACS Appl. Mater. Interfaces 2014, 6, 15302-15308.

415

(19) Guo, Z. Y.; Zhou, D. D.; Dong, X. L.; Qiu, Z. J.; Wang, Y. G.; Xia Y. Y. Ordered

416

Hierarchical Mesoporous/Macroporous Carbon: A High-Performance Catalyst for Rechargeable

417

Li-O2 Batteries. Adv. Mater. 2013, 25, 5668-5672.


22

Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


418

(20) Chen, J.; He, S. M.; Yue, Q.; Wang, M. H.; Deng, Y. H.; Cai, H. Q.; Huang, H. Synthesis

419

and Characterization of Hierarchically Ordered Porous Carbon Based Energetic Nanocomposites.

420

Adv. Porous Mater. 2014, 2, 31-36.

421

(21) Mao, H.; Shen, Y. Y.; Zhang, Q.; Ulaganathan, M.; Zhao, A. L.; Yang, Y. H.; Hng, H. H.

422

Highly Active and Stable Heterogeneous Catalysts Based on the Entrapment of Noble Metal

423

Nanoparticles in 3D Ordered Porous Carbon. Carbon 2016, 96, 75-82.

424

(22) Xue, H. R.; Tang, J.; Gong, H.; Guo, H.; Fan, X. L.; Wang, T.; He, J. P.; Yamauchi, Y.

425

Fabrication of PdCo Bimetallic Nanoparticles Anchored on Three-Dimensional Ordered N-

426

Doped Porous Carbon as an Efficient Catalyst for Oxygen Reduction Reaction. ACS Appl. Mater.

427

Interfaces 2016, 8, 20766-20771.

428

(23) Fan, J. W.; Ran, X. Q.; Ren, Y.; Wang, C.; Yang, J. P.; Teng, W.; Zou, L. Y.; Sun, Y.; Lu,

429

B.; Deng, Y. H.; Zhao, D. Y. Ordered Mesoporous Carbonaceous Materials with Tunable

430

Surface Property for Enrichment of Hexachlorobenzene. Langmuir 2016, 32, 9922-9929.

431

(24) Guo, Y. H.; Wang, M. H.; Xia, G. L.; Ma, X. H; Fang, F.; Deng, Y. H. Advanced H2-

432

Storage System Fabricated Through Chemical Layer Deposition in a Well-designed Porous

433

Carbon Scaffold. J. Mater. Chem. A 2014, 2, 15168-15174.

434

(25) Sun, Z. K.; Sun, B.; Qiao, M. H.; Wei, J.; Yue, Q.; Wang, C.; Deng, Y. H.; Kaliaguine, S.;

435

Zhao, D. Y. A General Chelate-Assisted Co-Assembly to Metallic Nanoparticles-Incorporated

436

Ordered Mesoporous Carbon Catalysts for Fischer-Tropsch Synthesis. J. Am. Chem. Soc. 2012,

437

134, 17653-17660.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

438 439 440 441

Page 24 of 26

(26) Wang, J. Y.; Li, J. L.; An, C. W.; Hou, C. H.; Xu, W. Z.; Li X. D. Study on Ultrasoundand Spray-Assisted Precipitation of CL-20. Propellants, Explos., Pyrotech. 2012, 37, 670-675. (27) Bayat, Y.; Zarandi, M.; Zarei, M. A.; Soleyman, R.; Zeynali, V. A Novel Approach for Preparation of CL-20 Nanoparticles by Microemulsion Method. J. Mol. Liq. 2014, 193, 83-86.

442

(28) Wang, D. J.; Gao, B.; Yang, G. C.; Nie, F. D.; Huang, H. Preparation of CL-20 Explosive

443

Nanoparticles and Their Thermal Decomposition Property. J. Nanomater. 2016, DOI: 10.

444

1155/2016/5462097.

445

(29) Deng, Y. H.; Liu, C.; Yu, T.; Zhang, F. Q.; Wan, Y.; Zhang, L. J.; Wang, C. C.; Tu, B.;

446

Webley, P. A.; Wang, H. T.; Zhao, D. Y. Facile Synthesis of Hierarchically Porous Carbons

447

from Dual Colloidal Crystal-Block Copolymer Template Approach. Chem. Mater. 2007, 19,

448

3271-3277.

449 450

(30) Stöber, W.; Fink, A.; Bohn, E. Controlled Growth of Monodisperse Silica Spheres in the Micron Size Range. J. Colloid Interface Sci. 1968, 26, 62-69.

451

(31) Kim, Y. J.; Kim, M. I.; Yun, C. H.; Chang, J. Y.; Park, C. R.; Inagaki, M. Comparative

452

Study of Carbon Dioxide and Nitrogen Atmospheric Effects on the Chemical Structure Changes

453

during Pyrolysis of Phenol–Formaldehyde Spheres. J. Colloid Interface Sci. 2004, 274, 555-562.

454

(32) Deng, Y. H.; Cai, Y.; Sun, Z. K.; Gu, D.; Wei, J.; Li, W.; Guo, X. H.; Yang, J. P.; Zhao, D.

455

Y. Controlled Synthesis and Functionalization of Ordered Large-Pore Mesoporous Carbons. Adv.

456

Funct. Mater. 2010, 20, 3658-3665.


24

Page 25 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


457

(33) Cai, H. Q.; Yang, R. J.; Yang, G. C.; Huang, H.; Nie, F. D. Host-Guest Energetic

458

Nanocomposites Based on Self-Assembly of Multi-Nitro Organic Molecules in Nanochannels of

459

Mesoporous Materials. Nanotechnology 2011, 22, 305602.

460

(34) Li, H. F.; Xi, H. A.; Zhu, S. M.; Wen, Z. Y.; Wang, R. D. Preparation, Structural

461

Characterization, and Electrochemical Properties of Chemically Modified Mesoporous Carbon.

462

Micropor. Mesopor. Mat. 2006, 96, 357-362.

463 464

(35) Castilla, C. M.; Ramón, M. V. L.; Marín, F. C. Changes in Surface Chemistry of Activated Carbons by Wet Oxidation. Carbon 2000, 38, 1995-2001.

465

(36) Bazuła, P. A.; Lu, A. H.; Nitz, J. J.; Schüth, F. Surface and Pore Structure Modification of

466

Ordered Mesoporous Carbons via a Chemical Oxidation Approach. Micropor. Mesopor. Mat.

467

2008, 108, 266-275.

468

(37) Lee, K. T.; Lytle, J. C.; Ergang, N. S.; Oh, S. M.; Stein, A. Synthesis and Rate

469

Performance of Monolithic Macroporous Carbon Electrodes for Lithium-Ion Secondary Batteries.

470

Adv. Funct. Mater. 2005, 15, 547-556.

471 472

(38) Castello´, M. L.; Dweck, J.; Aranda, D. Kinetic Study of Thermal Processing of Glycerol by Thermogravimetry. J. Therm. Anal. Calorim. 2011, 105, 737-46.

473

(39) Yan, Q. L.; Zeman, S.; Elbeih, A.; Song, Z. W.; Málek, J. The Effect of Crystal Structure

474

on the Thermal Reactivity of CL-20 and its C4 Bonded Explosives (I): Thermodynamic

475

Properties and Decomposition Kinetics. J. Therm. Anal. Calorim. 2013, 112, 823-836.

476 477

(40) Turcotte, R.; Vachon, M.; Kwok, Q. S. M.; Wang, R. P.; Jones, D. E. G. Thermal Study of HNIW (CL-20). Thermochim. Acta 2005, 433, 105-115.


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

478

Page 26 of 26

For Table of Contents Only

479


26

Enhanced Thermal Decomposition Properties of CL-20 through Space

Recommend Documents