To study the effect of particle size on the internal pore structure of micro/nano energetic materials, three kinds of micro/nano explosives 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) with different particle sizes were selected as the research objects. The internal pore structure information, including porosity, pore volume distribution and fractal characteristics of micro/nano LLM‐105 were characterized by contrast variation small‐angle X‐ray scattering (CV‐SAXS). The scattering results show that the power‐law index of three samples with different particle sizes is between 3 and 4 in the measured q range (the surface fractal dimension Ds of 200 nm LLM‐105 is 2.16, Ds of 500 nm LLM‐105 is 2.20, and Ds of 3 μm LLM‐105 is 2.76). With the decrease of particle size, the interface between the internal pores and matrix becomes smooth. The pore volume per unit mass of LLM‐105 increases with the decrease of the particle size. The increase of pore volume per unit mass when the particle size decreases from 3 μm to 500 nm is much larger than that when the particle size decreases from 500 nm to 200 nm. The number of 2.5 nm–40 nm internal pores in LLM‐105 increases with the decrease of particle size. Especially for the pores of 11 nm, the number of pores increases most obviously with the decrease of particle size.

In order to improve the safety of hexanitrohexaazaisowurtzitane , submicron CL-20 particles were prepared by a siphon ultrasonic-assisted spray refining experimental device. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), and the impact sensitivity of the samples was tested.The results show that the particle size of siphon-refined CL-20 is about 800 nm~1 μm, which is more smooth, mellow, and dense than that of CL-20 prepared by a traditional pressure-refined method. The peak diffraction angle of pressure-and siphon-refined CL-20 is basically the same as that of raw CL-20, and their crystal forms are ε type. The peak strength of pressure-and siphon-refined CL-20 decreased obviously. The apparent activation energy of pressure-refined CL-20 and siphon-refined CL-20 is 13.3 kJ/mol and 11.95 kJ/mol higher than that of raw CL-20, respectively. The thermal stability of CL-20 is improved. The activation enthalpy (ΔH # ) is significantly higher than that of raw CL-20, and the characteristic drop is 70.4% and 82.7% higher than that of raw CL-20. The impact sensitivity of siphon-refined CL-20 is lower than that of pressure-refined CL-20, so the safety performance of an explosive is improved obviously.

Ultrafine explosives show high safety and reliable initiation and have been widely used in aerospace, military, and industrial systems. The outstanding performance of ultrafine explosives is largely given by the unique void defects according to the simulation results. However, the structures and effects of internal nano-voids in ultrafine explosive particles have been rarely investigated experimentally. In this work, contrast-variation small angle X-ray scattering was verified to reliably measure the structures of internal nano-voids in ultrafine explosive 2,6diamino-3,5-dinitropyrazine-1-oxide (LLM-105) and 2,2′,4,4′,6,6′-hexanitro diphenylethylene (HNS). The size of nano-voids is around 10 nm, and the estimated number of nanovoids in a single particle is considerable. Moreover, the thermal stability of ultrafine LLM-105 was improved via changing the structures of nano-voids. This work provides a methodology for the study of nano-void defects in ultrafine organic particles and may pave the path to enhance the performance of ultrafine explosives via defect engineering.

C12H17N9O8, orthorhombic, Pna21 (no. 33), a = 11.376(4) Å, b = 7.966(2) Å, c = 19.076(6) Å, V = 1728.6(9) Å3, Z = 4, R gt (F) = 0.0373, wR ref (F 2) = 0.0908, T = 296 K.