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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

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ACS Applied Materials & Interfaces

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Enhanced Thermal Decomposition Properties of CL-

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20 through Space-Confining in Three-Dimensional

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Hierarchically Ordered Porous Carbon

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

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Guangcheng Yang *, and Hui Huang*

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

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China

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

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porous carbon, Nanocomposites

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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propellants.

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INTRODUCTION

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

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

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

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

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

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

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the further development of solid propellants.

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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with higher activity for CL-20 thermal decomposition.

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

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

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

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

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

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

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

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

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

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

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

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development of CL-20-based solid propellants.


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

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

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

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

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

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

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

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

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

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

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

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propellants.

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EXPERIMENTAL SECTION

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

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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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C-305A.

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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decomposition was determined by differential scanning calorimetry-thermogravimetry analyses

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

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


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

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

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RESULTS AND DISCUSSION

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

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

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

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

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

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

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

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

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


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

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samples. a

b

e

Windows

c

d

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

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

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

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

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

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

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

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

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

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

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oxidative treatment.


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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

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

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

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

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filled by CL-20 nanocrystals. a

b

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

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nanocomposites with CL-20.

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

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

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

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

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

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

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

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

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


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

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oxygen-containing groups. a

b

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

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

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HOPC scaffold.

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

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

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

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

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

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

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

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

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

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

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


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

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

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presence of a large number of surface oxygen groups.

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

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

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

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

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

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

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

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

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

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

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

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

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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.

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

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

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

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

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

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

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


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

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

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

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

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

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

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and nanocomposites. b

a

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

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heating rate of 10 oC/min.

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

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

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

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

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

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


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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

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for 20 °C /min, respectively.

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

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

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the results are shown in Table 1.

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

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

(1)

(2)

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

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

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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

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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


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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

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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


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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


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