Synthesis of Energetic Materials by Rapid Expansion of a Supercritical Solution into Aqueous Solution (RESS-AS) Process

Abstract

Energetic crystalline nanoparticles have many benefits when incorporated into a propellant or explosive. They have been shown to be less sensitive to impact and can also change the energetic performance of a propellant or explosive. In this study, two processes are investigated and compared for producing nano-scale energetic oxidizer particles. Rapid Expansion of a Supercritical Solution (RESS) was investigated and a similar process called the Rapid Expansion of a Supercritical Solution into an Aqueous Solution (RESS-AS) process was used to produce RDX and bis(2,2,2-trinitroethyl)-3,6diaminotetrazine (BTAT) particles. For similar pre-expansion conditions, the RESS process produced RDX particles with an average size of approximately 100 nm and the RESS-AS process produced RDX particles with an average size of 30 nm. The small RDX particles were able to be coated and stabilized from permanent agglomeration in the RESS-AS process with polyvinylpyrrolidone (PVP) and polyethylenimine (PEI). The energetic material BTAT was produced initially in Germany and reprocessed first by the RESS process and nearly spherical particles of around 100 nm were created that were agglomerated. Later, BTAT particles were produced by the RESS-AS process by expanding into an aqueous solution of SDS and water produced small nano-sized rods (width and height around 100 nm) without agglomeration. The synthesized RDX particles were tested in a TGA/DSC and it was found that RESS synthesized RDX experienced nearly no temperature shift in its melting and decomposition temperature in comparison to larger micron-sized RDX. However, the RESS-AS synthesized RDX particles experience a decomposition exotherm about 25° C below the value for conventional RDX. The lowered melting point suggests that RESS-AS synthesized RDX particles have different thermodynamic properties that should be investigated further. One of these properties associated with the nano-sized particles is the ability of storing extra energy on their surface and/or due the high percentage of surface molecules with lower coordination numbers.

The longstanding challenge of the nanocrystallization of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX)

“…After the success of the RESS process, Essel et al developed a new method based on that technique called RESS-AS, which as first reported in 2010 [ 71 ]. RESS-AS uses the versatility of the RESS process, while spraying into an aqueous solution containing a dispersant and/or growth inhibitor [ 72 ]. They reported [ 73 ] the synthesis of 30 nm RDX in a pH 7-stabilized solution.…”

Tuning the Oxygen Balance of Energetic Composites: Crystallization of ADN/Secondary Explosives Mixtures by Spray Flash Evaporation

“…Some authors report the use of milling [7,8] though the risk of unintentional decomposition initiation due to high energy transfer to the energetic compounds remains high. Contrary, bottom-up spray processes like electrospray [9], rapid expansion of supercritical solutions (RESS) [10,11] or spray flash evaporation (SFE) yield better control of heat transfer and reduce thus the risk of unintentional decomposition.…”