Growth and Characterization of β-RDX Single-Crystal Particles

Abstract

Trinitrohexahydro-s-triazine (RDX) single-crystal particles crystallized in the β phase have been successfully grown by sublimation−recrystallization. Synchrotron X-ray diffraction results confirm that the recrystallized products are β-RDX single crystals. Compared to the traditional solution deposition methods, the sublimation method used in this work breaks through the mass limitations during the growth of β-RDX. The distribution of αand β-RDX on different substrates reveals that hydrophilic substrates are prone to grow β-RDX single crystals and that hydrophobic substrates prefer α-RDX single crystals. The sublimation rate dominates the growth of pure β-RDX. The mechanisms of the phase transition from β-RDX to α-RDX during the process of sublimation−recrystallization have been studied. The current results can promote the potential application of β-RDX in the propellant, explosives, and military fields.

Phase Confirmation and Equation of State of β-HMX under 40 GPa

“…Apart from chemical components, crystal properties, including phase structures, grain sizes, and surface and internal defects, are known to have a significant influence on the mechanical strength, sensitivity, and stability of high explosives. − HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) is an eight-membered heterocyclic high-energy explosive that has been widely used for military weapons, aerospace applications, and modern industrial applications − because of its characteristics of high energy density, good thermal stability, high detonation performance, and product cleanliness. By controlling the crystallization rate in the solution, we can observe four crystal structures, including three pure crystallization phases of α, β, and γ and a hydrate γ structure, at ambient conditions. − The β phase is the most thermodynamically stable polymorph that has the highest density and is the only one used in weapons.…”

Pressure-Induced Phase Transition of β-RDX Single Crystals

“…There exists an extensive network of hydrogen-bond interactions because of the short contacts of N···O and H···O (<3 Å), as displayed in Figure S1. Previous investigations have revealed that β-RDX can easily transform into α-RDX by mechanical contact, temperature, concentration, specific solvents, and coming into contact with α-RDX. − Furthermore, the transition could affect the crystal quality and performance by introducing defects . However, the prepared β-RDX single crystals with high quality and less defects in Figure b remain stable during transferring β-RDX into DAC, while the bamboolike β-RDX with more defects are easy to break and transform.…”

“…β-RDX single crystals were prepared by the sublimationrecrystallization method as reported in our previous work. 30 Figure 1a shows the molecular structure of β-RDX. There are two independent molecules in β-RDX.…”

“…In previous works, the purity of β-RDX was poor, and obtaining in-depth insights into the mechanism for the transition from β-RDX to α-RDX is difficult. We obtained pure and high-quality β-RDX single-crystal rods with the method of sublimation-recrystallization . Millar et al proposed the possible reason for the facile transition .…”

“…We obtained pure and high-quality β-RDX single-crystal rods with the method of sublimation-recrystallization. 30 Millar et al proposed the possible reason for the facile transition. 31 In our latest work, we found that the contacting induced self-sustaining phase transition between isomeric crystals of RDX.…”