Mesoscale evolution of voids and microstructural changes in HMX-based explosives during heating through the β-δ phase transition

Abstract

HMX-based explosives LX-10 and PBX-9501 were heated through the β-δ phase transition. Ultra-small angle x-ray scattering (USAXS) and molecular diffraction were simultaneously recorded as the HMX was heated. Mesoscale voids and structure dramatically change promptly with the β-δ phase transition, rather than with other thermal effects. Also, x-ray induced damage, observed in the USAXS, occurs more readily at elevated temperatures; as such, the dose was reduced to mitigate this effect. Optical microscopy performed during a similar heating cycle gives an indication of changes on longer length scales, while x-ray microtomography, performed before and after heating, shows the character of extensive microstructural damage resulting from the temperature cycle and solid-state phase transition.

The Microstructural Evolution in HMX Based Plastic-Bonded Explosive During Heating and Cooling Process: an in situ Small-angle Scattering Study

“…The conversion of β-to δ-phase HMX during the heating process is accompanied by a change in crystal morphology and about a 7% volume expansion, which may result in new cracks and voids. In this study, the expected increase of the interfacial surface area induced by the β→δ phase transition is not observed, a difference to Willey's results [14]. The difference may be attributed to the discrepancy in the initial structure and chemical composition of the samples.…”

“…In the SAXS experiments, the defect evolution in thermally treated HMX-PBX was interpreted in terms of the β→δ phase transition of HMX [10,11,14]. In this study, our findings show that significant damage of the thermally treated (above the HMX phase transition temperature) HMX-PBX develops during the after-heating storage process.…”

“…In a recent work, Willey et al [14] studied the microstructural evolution of HMX-PBXs during heating by means of in situ ultra SAXS. They found that the microstructure of the samples dramatically changed with the β→δ phase transition, and the void volume increased when the samples were cooled to RT.…”

Performance and Detonation Characteristics of Polyurethane Matrix Bonded Attractive Nitramines

“…The nitramines were ε-CL20 4,6,8,10,4,6,8,10,, 3,4,imidazole), RDX (1,3,5-trinitro-1,3,5-triazacyclohexane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane). The detonation velocities were measured experimentally.…”

Application of BCHMX in Shaped Charges against RHA Targets Compared to Different Nitramine Explosives

“…Several studies have investigated the effects of explosive type [4,5], explosive particle size [6][7][8], binder system [9][10][11][12], and their physical or/ and chemical compatibility [13,14] on the energetic performance of plastic bonded explosives. Plastic bonded explosives (PBXs) containing ε-HNIW (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, ε-CL-20) have been intensively investigated, since it has an excellent explosive performance [15,16], high energy density, and good thermal stability [13].…”