Formation Mechanism of Anisotropic RDX-TNT Core-Shell Nanoparticles and their Influence onto Nanodiamond Detonation Syntheses
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Mixtures of RDX and TNT or hexolite mixtures are well known precursors for nanodiamond detonation syntheses. In this study diverse nanoscale hexolite mixtures varying in mass ratios of RDX and TNT are synthesized via Spray Flash Evaporation. The hexolite mixtures are characterized by confocal Raman spectroscopy and tip-enhanced Raman spectroscopy (TERS) to obtain information about their molecular structure composition. The marker bands of pristine RDX and TNT enable the identification and distinction of both compounds in the Raman spectra. Confocal Raman spectroscopy indicates an intermixture of RDX and TNT molecules on the nanoscale since both marker bands are detected in all spectra. TERS investigations of single hexolite particles reveal that the particle surfaces are mainly composed of TNT. The comparison of confocal Raman and TERS results suggests that (depending on the mass ratio) hexolite particles are either inhomogeneous patchy RDX/TNT nanoparticles or anisotropic RDX/TNT core-shell nanoparticles. A building mechanism to explain the formation/growth of those nanoparticles is derived from the spectroscopic data and the dynamics of the SFE process. Finally, a correlation between the TNT shell thickness, the symmetry of the anisotropic hexolite precursor nanoparticles, and the resulting nanodiamond sizes is discussed in detail.