Cocrystallization is a helpful method for explosives improvement. However, lack of knowledge of the formation mechanism leads to low efficiency in cocrystal preparation. In order to enhance the understanding of the cocrystal formation mechanism, the formation process of CL-20/HMX cocrystals are investigated by using the X-ray diffraction qualitative/quantitative analysis and scanning electron microscopy methods in anhydrous acetone, acetone/ H 2 O solvent, and slightly soluble-medium transition experiments. We find that the formation process of CL-20/HMX cocrystal experiences significant phase transition from CL-20 and HMX separated precipitations to CL-20/HMX cocrystal in acetone solvent, and also in slightly soluble medium. The solvent media and tiny active secondary nuclei are necessary in the phase transition process. On the basis of this paper, we have a more profound understanding of the formation mechanism of cocrystals. It is helpful to select more suitable experimental conditions and make access to excellent cocrystals more efficient.

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The host–guest inclusion strategy has become a promising method for developing novel high-energy density materials (HEDMs). The selection of functional guest molecules was a strategic project, as it can not only enhance the detonation performance of host explosives but can also modify some of their suboptimal performances. Here, to improve the propulsion and combustion performances of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW), a novel energetic-energetic host–guest inclusion explosive was obtained by incorporating energetic rocket fuel, hydroxylamine (HA), into the lattice cavities of HNIW. Based on their perfect space matching, the crystallographic density of HNIW-HA was determined to be 2.00 g/cm3 at 296 K, which has reached the gold standard regarding the density of HEDMs. HNIW-HA also showed higher thermal stability (T d = 245.9 °C) and safety (H 50 = 16.8 cm) and superior detonation velocity (D V = 9674 m/s) than the ε-HNIW. Additionally, because of the excellent combustion performance of HA, HNIW-HA possessed higher propulsion performances, including combustion speed (S C = 39.5 mg/s), combustion heat (Q C = 8661 J/g), and specific impulse (I sp = 276.4 s), than ε-HNIW. Thus, the host–guest inclusion strategy has potential to surpass the limitations of energy density and suboptimal performances of single explosives and become a strategy for developing multipurpose intermolecular explosives.

Small-angle X-ray scattering (SAXS) is an effective method to obtain microstructural information of materials. However, due to the influence of crystal surface effects, SAXS has a deviation in the characterization of the crystal microstructure. In order to solve the influence of crystal surface effect on the internal defect signal, the microstructure of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystal was characterized by soaking the sample in the matching solution. We found that the absolute scattering intensity, specific surface and volume fraction of the sample in the matching solution are significantly lower than the initial sample, which solves the influence of the crystal surface effect on the test results. Comparing the scattering results of the samples in different electron density matching solutions, it was found that the best result was obtained when using GPL-107 perfluoropolyether (PFPE) matching solution and the same law was obtained by controlling the experiment with 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) crystal. The fitting density was calculated according to the theoretical density and void volume fraction of the sample, and the calculated results are close to the test results of Particle Density Distribution Analyzer (PDDA). Based on this paper, we provide a method to obtain the correct information of crystal microstructure.