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481 results on '"Yan, Qi-Long"'

26. Surpassing the Ambient Packing Limit of Energetic Crystals: Squeezing Effect of Molecular Level 'Net-fishing'

Author

Yan, Qi-Long, Yang, Zhi-Jian, He, Guo-Qiang, He, Wei, Lv, Jie-Yao, Huang, Shi, Chen, Jian, Chen, Shu-Wen, Liu, Pei-Jin, Zhang, Qing-Hua, and Nie, Fu-De

Subjects
Condensed Matter - Materials Science
Abstract

High energy density is always a key goal for developments of energy storage or energetic materials (EMs). Except exploring novel EMs with high chemical energy, it is also desirable if the traditional EMs could be assembled at a higher density. However, it is very difficult to surpass their theoretical maximum molecular packing density under ambient conditions, even though a higher density could be achieved under ultra-high pressure (Gigapascals). Such solid-state phase changes are reversible, and hence this high density packing is not able to maintain under ambient conditions. Alternatively, in this research, we demonstrated a molecular level compression effect by stacking of 2-D TAGP, resulting in a higher density packing of the HMX molecules with changed conformation. The HMX crystal formed under compression in the solvent has a unit cell parameter very close to the reported one observed under pressure of 0.2 GPa. It shows that the compressed HMX molecules are trapped in the TAGP layers, resulting in a higher density (e.g. 2.13 g cm-3) and also higher heat of formation. The resulted HMX crystals are free of defects, and unlike the pristine HMX, no polymorphic transition and melting point were observed upon heating. Experiments and relevant calculations show that the best resulted hybrid HMX crystal has a detonation velocity of 10.40 km s-1 and pressure of 53.9 GPa, respectively. Its ground specific impulse reaches about 292 s, even much better than CL-20, making it a promising propellant component for future space explorations.

Published
2018

39. Desensitization of spherical CL-20 composites by embedding insensitive nanosized energetic crystals.

Author

Xue, Zhi-Hua, Xu, Ruixuan, Qin, Jianheng, Wang, Zikangping, Liu, Yu, and Yan, Qi-Long

Abstract

The development of spherical CL-20-based co-particles, which incorporate nanosized nLLM-105@PDA and nFOX-7@PDA crystals at different ratios (1%, 5%, and 10%), has been achieved using a spray drying technique. This innovative approach results in solid spherical co-particles where the nanosized inclusions are tightly integrated in CL-20 based composite crystals, where the outer shell is primarily composed of CL-20. Scanning electron microscopy (SEM) confirms the structural integrity of these co-particles, and nano-computed tomography further elucidates the intricate interfacial structure. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analyses reveal that these co-particles undergo a single-step decomposition process, akin to their energetic co-crystals. This behavior is indicative of a unified and predictable thermal response. Molecular dynamics (MD) simulations, employing a reactive forcefield, have been conducted to track their thermal decomposition products. Although the CL-20 polymorph in both co-LLM-105P/CL-20 and co-LLM-105P/CL-20 co-particles is in the β-phase, their impact initiation energy is approximately 4 to 6 times higher than that of raw ε-CL-20. Moreover, the co-particle formulation does not adversely affect the velocity of detonation (VoD) and detonation pressure (PC–J), showing that the energy density is preserved. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Reactivity Control of Oxidative CL-20@PVDF Composite Microspheres by Using Carbon Nanomaterials as Catalysts.

Author

Chen, Shuwen, Yu, Minghui, Xue, Zhi-Hua, Ding, Yibing, Zhang, Chao, and Yan, Qi-Long

Subjects
CHAIN scission, FLAME temperature, SPRAY drying, POLYVINYLIDENE fluoride, ACTIVATION energy
Abstract

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is one of the high-energy oxidants, but has limited application due to its high sensitivity. In this work, polyvinylidene fluoride (PVDF) was used as a co-oxidizer, which is expected to increase the safety of CL-20. One kind of novel graphene-based carbohydrazide complex (GCCo and GCNi) was employed to modify the properties of dual-oxidant CL-20@PVDF composites by the spray drying method and compared with traditional nanocarbon materials (CNTs and GO). The properties of these composites were investigated using the TGA/DSC technique and impact test. The results show that GCCo and GCNi could increase the activation energy (Ea) of CL-20@PVDF composites, and change the physical model of CL-20@PVDF, which followed the random chain scission model and then the first-order reaction model. In addition, these nanocarbon materials could reduce the impact sensitivity of CL-20@PVDF by their unique structure. Besides that, a dual-oxidant CL-20@PVDF system was used to improve the combustion property of Boron. GCCo and GCNi with the synergetic effect could increase the flame temperature and control the burn rate of CL-20@PVDF@B compared with CNTs and GO. The energetic nanocarbon catalyst-modified oxidant provides a facile method for stabilizing high-energy but sensitive materials to broaden their application. [ABSTRACT FROM AUTHOR]

Published
2024
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