http://www.sciencemadness.org/talk/files.php?pid=302583&aid=26587

Azole-based energetic salts.

Fabrication of RDX, HMX and CL-20 based microcapsules via in situ polymerization of melamine–formaldehyde resins with reduced sensitivity

Advanced methodologies for cocrystal synthesis.

RDX-based nanocomposite microparticles for significantly reduced shock sensitivity

Energetic materials, including explosives, pyrotechnics, and propellants, are widely used in mining, demolition, automobile airbags, fireworks, ordnance, and space technology. Nanoenergetic materials (nEMs) have a high reaction rate and high energy density, which are both adjustable to a large extent. Structural control over nEMs to achieve improved performance and multifunctionality leads to a fascinating research area, namely, nanostructured energetic materials. Among them, core-shell structured nEMs have gained considerable attention due to their improved material properties and combined multiple functionalities. Various nEMs with core-shell structures have been developed through diverse synthesis routes, among which core-shell structured nEMs associated with explosives and metastable intermolecular composites (MICs) are extensively studied due to their good tunability and wide applications, as well as excellent energetic (e.g., enhanced heat release and combustion) and/or mechanical properties. Herein, the preparation methods and fundamental properties of the abovementioned kinds of core-shell structured nEMs are summarized and the reasons behind the satisfactory performance clarified, based on which suggestions regarding possible future research directions are proposed.

Core–Shell Structured Nanoenergetic Materials: Preparation and Fundamental Properties

Nanoscale crystals of cyclotrimethylenetrinitramine (RDX) were produced by Rapid Expansion of Supercritical Solutions (RESS). The experiments were performed by expansion of supercritical solutions of RDX in carbon dioxide through sapphire nozzles (ID: 100 and 150 mm) at pressures of 15.0 – 29.5 MPa and temperatures of 343 – 348 K. Recrystallized particles were characterized by Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction, HPLC and melting point analysis. The process produced particles with a mean size in the range 110 – 220 nm and a narrow size distribution. The product was crystalline as determined by X-ray diffraction. The effect of process conditions (T, P, nozzle diameter) on the crystal size distribution was determined.

Production of Nanocrystalline RDX by Rapid Expansion of Supercritical Solutions

Energetic nanoscale 2CL-20·HMX, a cocrystal of CL-20 and HMX in a 2 : 1 molar ratio, was prepared by a novel method of bead milling an aqueous suspension of e-CL-20 and β-HMX. The conversion of the coformers to the cocrystal form was monitored by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis of specimens sampled at various milling times. Complete conversion to the cocrystal form was achieved by 60 minutes of milling. Rounded 2CL-20·HMX cocrystal particles with a mean size below 200 nm were produced. A mechanism for the conversion of the coformers to the cocrystalline form is postulated based on the experimental results. As an inherently safe manufacturing method, the aqueous bead milling process has great potential in advancing cocrystal research and applications in the field of energetic materials.

Nanoscale 2CL-20·HMX high explosive cocrystal synthesized by bead milling

The initiation sensitivity of cyclotrimethylenetrinitramine (RDX) was investigated as a function of crystal size. For this study, RDX powders with mean crystal sizes of ca. 200 and 500 nm were prepared by rapid expansion of supercritical solutions (RESS) with carbon dioxide as the solvent. Initiation sensitivity testing to impact, sustained shock, and electrostatic discharge stimuli was performed on uncoated as well as wax-coated specimens. The test data revealed that in a direct comparison to coarser grades the nanocrystalline RDX-based samples were substantially less sensitive to shock and impact stimuli. Furthermore, the 500 nm RDX-based specimens exhibited the lowest sensitivity values, an indication that minima in shock and impact sensitivities with respect to crystal size exist.

Victor Stepanov

Papers

RDX-based nanocomposite microparticles for significantly reduced shock sensitivity

Production of Nanocrystalline RDX by Rapid Expansion of Supercritical Solutions

Nanoscale 2CL-20·HMX high explosive cocrystal synthesized by bead milling

Production and Sensitivity Evaluation of Nanocrystalline RDX‐based Explosive Compositions

Single-step production and formulation of HMX nanocrystals