Synthesis of energetic material particles with controlled morphology
A surfactant-assisted self-assembly method can be used to crystallize energetic materials with controlled morphology. Microparticles of hexanitrohexaazaisowurtzitane (CL-20) formed by this method may have enhanced functional reproducibility due to their monodisperse nature, and decreased shock sensitivity due to their sub-2 μm particle size.
1. A method to synthesize energetic material particles, comprising:
providing a first solution comprising hexanitrohexaazaisowurtzitane and a first solvent;
providing a second solution comprising a second solvent that is immiscible in and has a higher boiling point than the first solvent;
providing a surfactant in the first or the second solution, wherein the surfactant comprises a nonionic surfactant having a hydrophilic-lipophilic balance between 4 and 8;
mixing the first and the second solutions to form an emulsion comprising the first solvent dispersed in the second solvent; and
evaporating the first solvent to form particles of hexanitrohexaazaisowurtzitane.
2. The method of claim 1 , wherein the first solvent comprises a polar aprotic solvent.
3. The method of claim 2 , wherein the polar aprotic solvent comprises ethyl acetate or acetone.
4. The method of claim 1 , wherein the second solvent comprises a hydrocarbon.
5. The method of claim 4 , wherein the hydrocarbon comprises heptane or octane.
6. The method of claim 1 , wherein the surfactant comprises an ionic surfactant.
7. The method of claim 6 , wherein the ionic surfactant comprises cetyl trimethylammonium bromide or sodium dodecyl sulfate.
8. The method of claim 1 , wherein the nonionic surfactant comprises a sorbitan ester, ethoxylated sorbitan ester, or polyethylene glycol alkyl ether.
9. The method of claim 1 , wherein the hexanitrohexaazaisowurtzitane particles are spherical in shape.
10. The method of claim 1 , wherein the hexanitrohexaazaisowurtzitane particles are less than 4 microns in diameter.
11. The method of claim 1 , wherein the hexanitrohexaazaisowurtzitane particles have an orthorhombic β-phase crystal structure.