Submicrosecond Aggregation during Detonation Synthesis of Nanodiamond

Abstract

Detonation nanodiamond (DND) is known to form aggregates that significantly reduce their unique nanoscale properties and require postprocessing to separate. How and when DND aggregates is an important question that has not been answered experimentally and could provide the foundation for approaches to limit aggregation. To answer this question, timeresolved small-angle X-ray scattering was performed during the detonation of high-explosives that are expected to condense particulates in the diamond, graphite, and liquid regions of the carbon phase diagram. DND aggregation into low fractal dimension structures could be observed as early as 0.1 μs, along with a separate scattering population also observed from an explosive that produces primarily graphitic products. A counterexample is the case of a highexplosive that produces nano-onions, where no hierarchical scattering was observed for at least 10 μs behind the detonation front. These results suggest that DND aggregation occurs on time scales comparable to particle formation.

Raman signatures of detonation soot

“…Representative transmission electron microscopy images of different categories of nanocarbon particulates found in the soot samples are shown in Figure 5. Consistent with previous reports, [ 45,54–57 ] TEM observations revealed a mixture of different carbon allotropes present in the soots of most explosives. Mixtures of nanodiamond and graphite fibers were observed in soots generated by Comp B, HNS IV, TNT, and FOX‐7.…”

“…The major exception to the broad heterogeneity of the soots was DNTF, which produced a soot that was almost completely composed of graphitic, onion‐like carbon, with a very minute fraction of diamond observed. [ 38,39,56,57 ]…”

Kinetics of Carbon Condensation in Detonation of High Explosives: First-Order Phase Transition Theory Perspective

“…However, this assumption would not agree with the experimental observations that at least several hundred nanoseconds are required for the formation of nanometer-sized particles in detonation. 22,24,[26][27][28]30 We thus conclude that the thermal equilibration is very fast at detonation-like conditions and the carbon particles can be assumed to be in thermal equilibrium with the detonation fluid.…”

“…Diamond and graphite-like particles recovered in this way turn out to be almost spherical with the diameter of ∼ 2-6 nm, which corresponds to ∼ 3 × 10 3 -3 × 10 4 carbon atoms, assuming the graphite or diamond density. [8][9][10][21][22][23][24][25][26] The second category -the data on the kinetics of carbon clustering -is rather scarce to date due to experimental complications arising from the need to observe the formation of nanometer-sized particles with nanosecond time resolution in an extreme environment (P ∼ 30 GPa, T ∼ 3000 K). Nevertheless, recent experiments demonstrate the sub-microsecond to few microsecond carbon clustering times and the actual kinetics of the growth of carbon particles in detonation.…”

“…Nevertheless, recent experiments demonstrate the sub-microsecond to few microsecond carbon clustering times and the actual kinetics of the growth of carbon particles in detonation. 22,24,[26][27][28][29][30][31] However, the convoluted nature of the experimental data does not presently allow for the direct parameterization of reactive burn models, so the development of the accurate theory of carbon condensation is required.…”