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International Journal of Energetic Materials and Chemical Propulsion

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v6.i1.60
pages 75-87

PRODUCTION OF NANOCRYSTALLINE RDX BY RAPID EXPANSION OF SUPERCRITICAL SOLUTIONS

Victor Stepanov
US Army, RDECOM-ARDEC, Armaments Engineering Technology Center, Picatinny Arsenal, NJ 07806-5000, USA
Inga B. Elkina
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Takuya Matsunaga
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Andrei V. Chernyshev
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Evgeny N. Chesnokov
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Xuyean Zhang
Material Characterization Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Nikolai L. Lavrik
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
Lev N. Krasnoperov
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA

ABSTRACT

A technique of Rapid Expansion of Supercritical Solutions (RESS) to produce nano-crystalline energetic materials was developed and characterized in application to production of nano-scale crystals of cyclotrimethylene-trinitramine (RDX). Nano-crystals of RDX were formed by expansion of supercritical solutions of RDX in carbon dioxide through a 100 μm sapphire nozzle at initial pressures of 150−295 bar and temperatures of 323−363 K. Produced particles were characterized by Field Emission Scanning Electron Microscopy, X-ray diffraction, HPLC, and melting point analysis. The process produced particles with the mean size in the range of 110 - 300 nm with a narrow size distribution.
The product was crystalline, as determined by X-ray diffraction. The effect of process conditions (T, P) on the crystal size distribution was determined. Initial impact sensitivity tests (performed with an ERL, Type 12 impact tester) were performed and compared with the sensitivity of the original (micron scale) material.
In addition to the characterization of the final particles produced by RESS, a technique to monitor particle growth in situ along the supersonic expansion jet was developed and applied to the RESS jet. The technique, based on UV pulsed laser imaging using a gated ICCD camera, allows direct measurements of the particle size distribution down the expanding jet. The same experimental approach utilizing two separated pulses from two lasers is used to characterize the velocity field after the nozzle.