The crystal structure has a great influence on mechanical sensitivity and detonation performance of energetic materials. An efficient microfluidic platform was applied for size, morphology, and crystallinity controllable preparation of ultrafine HMX. The microfluidic platform has good mixing performance, quick response, and less reagent consumption. The ultrafine γ-HMX was first prepared at room temperature by microfluidic strategy, and the crystal type can be controlled accurately by adjusting the process parameters. With the increase in flow ratio, the particle size decreases gradually, and the crystal type changed from β-HMX to γ-HMX. Thermal behavior of ultrafine HMX shows that γ→δ is easier than β→δ, and the phase stability of HMX is β > γ > δ. Furthermore, the ultrafine β-HMX has higher thermal stability and energy release efficiency than that of raw HMX. The ultrafine HMX prepared by microfluidic not only has uniform morphology and narrow particle size distribution, but also exhibits high density and low sensitivity. This study provides a safe, facile, and efficient way of controlling particle size, morphology, and crystallinity of ultrafine HMX.

1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) is a type of high energy explosive, its application in weapon systems is limited by its high mechanical sensitivity. At the same time, 1,1-diamino-2,2-dinitroethylene (FOX-7) is a famous insensitive explosive. The preparation of RDX@FOX-7 composites can meet the requirements, high energy and low sensitivity, of the weapon systems. It is difficult for the reactor to achieve uniform quality of composite material, which affects its application performance. Based on the principle of solvent-anti-solvent, the recrystallization process was precisely controlled by microfluidic technology. The RDX@FOX-7 composites with different mass ratios were prepared. At the mass ratio of 10%, the RDX@FOX-7 composites are ellipsoid of about 15 μm with uniform distribution and quality. The advantages of microscale fabrication of composite materials were verified. The results of structure characterization showed that there is no new bond formation in RDX@FOX-7, but the distribution of two components on the surface of the composite was uniform. Based on the structure characterization, we established the structure model of RDX@RDX-7 and speculated the formation process of the composites in microscale. With the increase of FOX-7 mass ratios, the melting temperature of RDX was advanced, the thermal decomposition peak of RDX changed to double peaks, and the activation energy of RDX@FOX-7 composite decreased. These changes were more pronounced between 3 and 10% but not between 10 and 30%. The ignition delay time of RDX@FOX-7 was shorter than that of RDX and FOX-7. RDX@FOX-7 burned more completely than RDX indicating that FOX-7 can assist heat transfer and improve the combustion efficiency of RDX.

As a typical high-energy-density material, the sensitivity of CL-20 severely limits its application in explosives and propellants. Adjusting its structure at the microscopic level can effectively solve such problems. In this study, a microfluidic recrystallization technique was used to prepare ε-CL-20 with three different particle sizes, with narrow particle size distributions (D₅₀ = 2.77 μm, 17.22 μm and 50.35 μm). The prepared samples had fewer surface defects compared to the raw material. As the particle size decreased, the density of CL-20 increased and its impact sensitivity was significantly reduced. The activation energy of the CL-20 prepared using microfluidic technology increased with increases in particle size. Laser ignition experiments revealed that smaller CL-20 particles had the highest energy release efficiency, while larger particles exhibited a higher energy density and more stable energy release. The combustion performance and safety of CL-20 can be effectively improved by improving the crystal size distribution and surface morphology. Controllable preparation of multiple particle sizes of CL-20 was achieved using microfluidic recrystallization technology, which provides a reference for the preparation of multiple particle sizes of other energetic materials.

Nitrogen-doped carbon-supported metal nano-particles show great promise as high-performance catalysts for novel energies, organic synthesis, environmental protection, and other fields. The synergistic effect between nitrogen-doped carbon and metal nano-particles enhances the catalytic properties. Thus, how to effectively combine nitrogen-doped carbon with metal nano-particles is a crucial factor for the synthesis of novel catalysts. In this paper, we report on a facile method to prepare nitrogen-doped carbon-supported metal nano-particles by using dimethylgly-oxime as ligand. The nano-particles of Pd, Ni, Cu, and Fe were successfully prepared by the pyrolysis of the corresponding clathrate of ions and dimethylglyoxime. The ligand of dimethylglyoxime is adopted as the source for the nitrogen-doped carbon. The nano-structure of the prepared Pd, Ni, Cu, and Fe particles are confirmed by X-ray diffraction, scanning electron microscopy, and trans-mission electron microscopy tests. The catalytic performances of the obtained metal nano-particles for oxygen reduction reaction (ORR) are investigated by cyclic voltammetry, Tafel, linear sweeping voltammetry, rotating disc electrode, rotating ring disc electrode, and other technologies. Results show that the nitrogen-doped carbon-supported metal nano-particles can be highly efficient catalysts for ORR. The results of the paper exhibit a facile methodology to prepare nitrogen-doped carbon-supported metal nano-particles.

In order to study the curing process of branched polyazide glycidyl ether (BGAP) binder and its propellant slurry at 50 to 70 °C, the rheological properties of BGAP binder and its propellant slurry were studied by chemical rheology. The results show that the viscosity coefficient of the uncured BGAP decreases gradually when the temperature increases, and when the plasticization ratio is 1.1, the viscosity coefficient of BGAP decreases first and then remains unchanged. After adding the curing agent, the chemical rheology method can be used to calculate whether the BGAP curing system still conforms to the power-law equation in a short time. The kinetic equation of the curing reaction, expressed by apparent viscosity, is deduced from the double Arrhenius equation, which can be expressed by η(T,t) = 10.16 exp (−1.72/T) exp [17.27 t exp (−5.21/T)]. After using BGAP as the adhesive to make a propellant slurry with a liquid material component of 25%, the effect of the particle size of Al powder in the solid filler component on the curing process of the slurry was studied, and the 200 nm Al powder could not be made into a slurry under this formulation. The curing kinetics equations of the slurry with Al powder particle sizes of 5 μm, 15 μm, and 29 μm under this formula were obtained by measuring the viscosity of the slurry over time at 50–70 °C. The results showed that the smaller the Al powder particle size, the lower the viscous flow activation energy of the slurry and the higher the curing reaction activation energy.