Mechanism investigation for remarkable decreases in sensitivities from micron to nano nitroamine

Abstract

Raw hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was pulverized to nano RDX by mechanical milling, and their micron morphology and surface elements were probed by transmission electron microscope and X-ray photoelectron spectroscopy analyses. Thermal analysis was employed to take a kinetic evaluation on thermal decomposition of raw and nano RDX. The result indicated that activation energy for thermal decomposition of nano RDX is closed to the value of raw RDX, which means nano RDX had similar thermal reactivity as raw RDX. However, the sensitivity tests showed that when raw RDX was pulverized to nanoparticles, its mechanical and shock sensitivities decreased by more than 45%. Since it was impossible to use kinetic evaluation to explain the reason why the difference on sensitivities between raw and nano RDX was so distinct, we recruited classic detonation models to solve the problem. By combining the models of Khasainov's and Merzhanov's, we related the detonation parameters such as temperature of hot spots, critical temperature of hot spots (T C), critical size of hot spots (δ C), and mean size of explosive particles, and concluded that: (a) under the same condition, mean size of hot spot in nano RDX charge was much smaller than that of raw RDX charge; (b) at the same δ C , T C of nano RDX (776 K) was higher than that of raw RDX (459 K); and (c) particle size was not an important factor to affect sensitivities of explosives unless size of explosive particles was less than 400 nm. These results must base on a steady thermal reactivity from micron to nano RDX.

Engineering the Morphology and Particle Size of High Energetic Compounds Using Drop-by-Drop and Drop-to-Drop Solvent–Antisolvent Interaction Methods

“…15 Wang et al have reduced the particle size of RDX successfully from 87 μm to 270 nm by the milling method and analyzed the factors affecting the safety of explosives by combining Khasanov’s and Merzhanov’s models to establish the relationship between the mean particle size, critical temperature, and critical size of hot spots. 16 They concluded that the mean particle size does not affect sensitivity, unless the mean particle size is lower than 400 nm. Their study also revealed that nanoscale level materials had lower sensitivity than the raw materials because of the small hot-spot size and high critical hot-spot temperature.…”

“…Their study also revealed that nanoscale level materials had lower sensitivity than the raw materials because of the small hot-spot size and high critical hot-spot temperature. 16 Guo et al prepared CL20 nanoparticles with a particle size of 200 nm by utilizing ball-milling technology. 17 Liu et al used bidirectional grinding mill technology to convert micron-sized particles of RDX, HMX, and CL-20 to nanosized particles.…”

Mechanochemical fabrication and properties of CL-20/RDX nano co/mixed crystals

“…According to current research in this eld, nanocrystallization and cocrystallization are superior to surface coating and spheroidization in terms of the enhancement of the insensitivity of energetic materials. [3][4][5] In our previous studies, using mechanical milling, we fabricated many kinds of nanoexplosives and investigated their properties. [6][7][8][9] These nanoexplosives were of particle sizes of 100-200 nm.…”

Process Research of Solution‐Enhanced Dispersion by Supercritical Fluids to Prepare Energetic Material Nano‐Capsules

“…The compatibility problem of multiple components in composite energetic materials can be solved by coating the surface of the particles. This process isolates individual components to improve their stability, reduce toxicity, and extend their warranty period [2–4]. Thus, the preparation of the core‐shell structure of microcapsules has become an important research direction in the field of nitramine energetic materials.…”