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Review
. 2020 Sep 20;25(18):4311.
doi: 10.3390/molecules25184311.

CL-20-Based Cocrystal Energetic Materials: Simulation, Preparation and Performance

Wei-Qiang Pang  1   2 , Ke Wang  1 , Wei Zhang  3 , Luigi T De Luca  4 , Xue-Zhong Fan  1 , Jun-Qiang Li  1
Affiliations
Review

CL-20-Based Cocrystal Energetic Materials: Simulation, Preparation and Performance

Wei-Qiang Pang et al. Molecules. .

Abstract

The cocrystallization of high-energy explosives has attracted great interests since it can alleviate to a certain extent the power-safety contradiction. 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-isowurtzitane (CL-20), one of the most powerful explosives, has attracted much attention for researchers worldwide. However, the disadvantage of CL-20 has increased sensitivity to mechanical stimuli and cocrystallization of CL-20 with other compounds may provide a way to decrease its sensitivity. The intermolecular interaction of five types of CL-20-based cocrystal (CL-20/TNT, CL-20/HMX, CL-20/FOX-7, CL-20/TKX-50 and CL-20/DNB) by using molecular dynamic simulation was reviewed. The preparation methods and thermal decomposition properties of CL-20-based cocrystal are emphatically analyzed. Special emphasis is focused on the improved mechanical performances of CL-20-based cocrystal, which are compared with those of CL-20. The existing problems and challenges for the future work on CL-20-based cocrystal are discussed.

Keywords: CL-20; characterization; cocrystal energetic materials; molecular dynamic simulation; preparation.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Intermolecular hydrogen bond of CL-20/TNT cocrystal [8], with permission from Han Neng Cai Liao, 2012.
Figure 2
Figure 2
CED (a), vdw (b) andelectrostatic (c) energies of CL-20/TNT cocrystal vs. temperatures [11], with permission from Chemical Journal of Chinese Universities, 2016.
Figure 3
Figure 3
Surface electrostatic potential energy distribution map of CL-20 (a) and TKX-50 (b), and the equilibrium structure of CL-20/TKX-50 cocrystal model (c), CL-20 and TKX-50 models (d) [34], with permission from Huo Zha Yao Xue Bao, 2020.
Figure 4
Figure 4
The primitive cell of CL-20/DNB cocrystal [3], with permission from Han Neng Cai Liao, 2015.
Figure 5
Figure 5
Time evolution of consumption of CL-20 and DNB and main products at various temperatures. (a) CL-20 and DNB; (b) 2000 K; (c) 2500 K; (d) 3000 K; [4], with permission from Han Neng Cai Liao, 2016.
Figure 6
Figure 6
Scanning electron microscope (SEM) photographs of CL-20, TNT and CL-20/TNT cocrystal. (a) CL-20; (b) TNT; (c) CL-20/TNT cocrystal [8], with permission from Han Neng Cai Liao, 2012.
Figure 7
Figure 7
SEM photographs of explosive samples. (a) Raw CL-20 (×100); (b) Raw TNT (×100); (c) CL-20/TNT cocrystal (×900); (d) CL-20/TNT cocrystal (×4200); (e) Spry drying CL-20 [20], with permission from Han Neng Cai Liao, 2015.
Figure 8
Figure 8
Differential scanning calorimetry (DSC) curves of explosive samples [20], with permission from Han Neng Cai Liao, 2015.
Figure 9
Figure 9
SEM photographs of CL-20, HMX and CL-20/HMX cocrystals at different mixing time. (a) CL-20; (b) HMX; (c) CL-20/HMX cocrystals for 5 min; (d) CL-20/HMX cocrystals for 15 min; (e) CL-20/HMX cocrystals for 30 min; (f) CL-20/HMX cocrystals for 45 min; (g) CL-20/HMX cocrystals for 60 min [6], with permission from Han Neng Cai Liao, 2020.
Figure 10
Figure 10
SEM photographs of CL-20/HMX mixture at different milling time. (a) 10 min; (b) 20 min; (c) 30 min; (d) 40 min; (e) 50 min; (f) 60 min; (g) 90 min; (h) 120 min; (i) 180 min; (j) 300 min; (k) 480 min; (l) CL-20; (m) HMX [7], with permission from Initiators & Pyrotechnics, 2018.
Figure 11
Figure 11
SEM photographs and particle size distribution of nano-sized CL-20/HMX cocrystal. (a) 50,000; (b) 20,000; (c) Frequency distribution; (d) Cumulative frequency distribution [9], with permission from Gu Ti Huo Jian Ji Shu, 2018.
Figure 12
Figure 12
SEM images (a–f) of specimens sampled at milling times between 0 and 60 min [36], with permission from Cryst. Eng. Comm, 2015.
Figure 13
Figure 13
SEM photographs of CL-20, TKX-50 and CL-20/TKX-50 cocrystal. (a) raw CL-20; (b) Raw TKX-50; (c) CL-20/TKX-50 cocrystal [34], with permission from Huo Zha Yao Xue Bao, 2020.
Figure 14
Figure 14
DSC curve of the CL-20/TNT cocrystal explosive [8], with permission from Han Neng Cai Liao, 2012.
Figure 15
Figure 15
DSC curves of different samples [6], with permission from Han Neng Cai Liao, 2020.
Figure 16
Figure 16
DSC curves of CL-20, TKX-50, CL-20/TKX-50 mixture and CL-20/TKX-50 cocrystal [34], with permission from Huo Zha Yao Xue Bao, 2020.
Figure 17
Figure 17
DSC curves of CL-20, DNB and CL-20/DNB cocryatal [5], with permission from Chinese Journal of Energetic Materials, 2013.
See this image and copyright information in PMC

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