Investigation of HMX‐Based Nanocomposites

Abstract

1I ntroductionNanoenergetics, in comparison with traditional energetics, exhibit enhanced performance, insensitivity,a nd mechanical strength, all of which are attributes required for next generation munition systems. Crystal size has as trong influence on the mechanical properties and the void size distribution of an explosive composition. These, in turn, govern the mechanical response of an explosive charge to shock stimuli by affecting the distribution of incident energy and thereby hot spot formation [1][2][3][4][5].I mproved mechanical properties can lead to reduced shock sensitivity in explosives [6,7].T he increased strength and stiffness of explosive compositions due to crystal size reduction, as described by the Hall-Petch relationship [8,9],c ontributes to reduced susceptibility to plastic deformation, which is ak ey precursor to initiation by mechanisms such as shear-band formation [10] and adiabatic void collapse [1]. Furthermore, significant evidence links higher reactivity with smaller crystal size in energetic materials. Some of the demonstrated improvements include:as maller critical diameter [11,12],s horter shock to detonation transition length [13,14],e nhanced sensitivity to initiation by short duration, high amplitude incident shocks [11],a nd improved detonation spreading [15].T hese improvements in performance are largely attributed to the higher number density of hot spots and al arger specific surface area. Gen-erally,i nsensitive explosive materials have low reactivity, as ignificant drawback. Nanoenergetics, therefore, are exciting because they exhibit an apparent paradox of high reactivity and low sensitivity.The key challenges in producing compositions containing HMX and CL-20 is obtaining the target crystal size, while retaining the desired polymorph, and achieving auniform binder coating without ripening the explosive [2,[16][17][18].I nt his study,t he approach used to produce the nano-HMX based compositions was ac ombination of mechanical particle size reduction and spray drying. Mechanical particle size reduction was utilized to achieve the desired crystal size of b-HMX. Am echanical (top down) process was em-Abstract:A dvanced munition systems require explosives which are more insensitive, powerful, and reactive. For this reason, nano-crystalline explosives present an attractive alternative to conventional energetics. In this study,f ormulations consisting of 95 %o ctahydro-1,3,5,7-tetranitro-1,3,5,7tetrazocine (HMX) and 5% polyvinyl alcohol (PVOH) were prepared with mean crystal sizes ranging from 300 nm to 2 mm. The process to create these materials used ac ombination of mechanical particle size reduction and spray drying, which has the advantages of direct control of crystal size and morphology as well as the elimination of ripening of crystals (which occurs during slurry coating of nanomaterials). The basic physical characteristics of these formulations were determined using av ariety of techniques, including scanning electron microscopy and X-ray diffraction. Compressive st...

Facile Fabrication of Nanoparticles Stacked 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) Sub‐microspheres via Electrospray Deposition

“…As one class of them, nano-explosives have attracted much attention due to their potential application in micro thrusters [6] and micro-electromechanical systems [7]. Recently, benefiting from the development of nanotechnology, a variety of nano-explosives such as 1,3,5-trinitro-1,3,5-triazinane (RDX) [8,9], HMX [10,11], 1,1-diamino-2,2-dinitroethene (FOX-7) [12,13], 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazawurt-zitane (CL-20) [14,15] and TATB [16,17] have been successfully prepared by various approaches. With respect to LLM-105, Zhang et al [18] utilized a spray-crystalline method to prepare submicron size LLM-105.…”

Polymeric Stabilization of Nano‐Scale HMX Suspensions During Wet Milling

“…Finally, a milling study was carried out to investigate the impact of the solvent and PVP addition on the HMX particle size. This work may have a significant impact toward the production of large quantities of nanoHMX that can be used to reduce the critical diameter and increase the mechanical strength of energetic formulations [18][19][20].…”

Preparation and Properties of a nRDX-based Propellant

“…Thus, pretreatment of nano-scaled particles should be needed to solve the agglomeration and non-uniformity problem. It is interesting that spray flash-evaporation [27], sol-gel [28], and aerosol techniques [29] can be used to fabricate nanoscaled energetic composite materials, and surface coating technologies are potential to avoid the agglomeration matter. However, undoubtedly these methods will increase processing complexity and cause much extra cost.…”