Exploration of Processing Parameters of Vacuum Assisted Micelle Confinement Synthesis of Spherical CL-20 Microparticles
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Exploration of Processing Parameters of Vacuum Assisted Micelle Confinement Synthesis of Spherical CL-20 Microparticles Kaifu Bian 1, Leanne Alarid 1, David Rosenberg 1, Hongyou Fan 1,2,* 1
Sandia National Laboratories, Albuquerque, New Mexico 87185, U.S.A.
2
Department of Chemical and Biological Engineering, Center for Micro-Engineered Materials, University of New Mexico, Albuquerque, New Mexico 87123, U.S.A.
ABSTRACT
We recently developed a vacuum assisted micelle confinement synthesis for spherical microparticles of CL-20 with outstanding monodispersity. These microparticles are promising energetic material for explosive devices with enhanced and predictable performances. In this work, to facilitate further development and application of this synthesis, the particle growth process was monitored by in-situ dynamic light scattering measurements. The result was interpreted by a finite element model to obtain critical parameters. These parameters were then used to predict the behavior and product quality of batch synthesis under various operation conditions.
INSTRODUCTION Controlled sensitivity and maximized efficiency of energetic materials have always been a major challenge to improve performance and safety of explosive devices. As an effective route, such optimization can be achieve by tuning the microscopic morphology of energetic materials including particle size, shape, purity and polymorphic phase.[1] Since its first synthesis in 1989,[2] CL-20 has been considered the most powerful energetic material for applications in military grade propellants and explosives.[3-6] To improve packing density, it had been a major challenge to obtain CL-20 particles with uniform regular shapes while existing methods provided less desired irregular particles.[7-10] We recently developed and reported a vacuum-assisted micelle confinement synthesis of micron-sized spherical CL-20 particles of narrow size distribution.[11] Briefly, a CL-20 solution in ethyl acetate (EA) was added into an octane (OCT) solution of Span 80, a nonionic surfactant. Under continuous stirring, vacuum was applied to preferentially remove the low boiling point EA from the binary solvent mixture. As the fraction of good solvent EA decreased to a certain level, CL-20 became oversaturated and precipitated to form microparticles within the micelles due to its preference to a polar environment over the highly hydrophobic OCT. These Downloaded from https://www.cambridge.org/core. Cambridge University Main, 06 shape Jan 2018can at 14:55:13, subject to the Cambridge Core microparticles are desirable because their uniform size on and potentially improve terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2017.642
the performance of explosive devices. For field test and mass production of the CL-20 microparticles, our milligram size synthesis has to be further developed and scaled up. In this work, we first monitored this microparticle formation in a static heterogeneous experiment using in-situ dynamic light scatteri
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