Detonation synthesis of carbon nano-onions via liquid carbon condensation

Nature Communications, Sep 2019

Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by high-resolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures.

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Detonation synthesis of carbon nano-onions via liquid carbon condensation

Detonation synthesis of carbon nano-onions via liquid carbon condensation M. Bagge-Hansen S. Bastea J.A. Hammons M.H. Nielsen L.M. Lauderbach R.L. Hodgin P. Pagoria C. May S. Aloni A. Jones W.L. Shaw E.V. Bukovsky N. Sinclair R.L. Gustavsen E.B. Watkins B.J. Jensen D.M. Dattelbaum M.A. Firestone R.C. Huber B.S. Ringstrand J.R.I. Lee T. van Buuren L.E. Fried T.M. Willey Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogenfree explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by highresolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures. - 1, ;:, () 0 9 8 7 6 5 4 3 2 1 S under the high pressures and temperatures (>10 GPa, olid carbon products, such as nanodiamond, are produced > 3000 K) generated during the detonation of many common high explosives (HEs)1–3. This observation, made as early as 19634, has subsequently been exploited for the mass production and broad technical and industrial application of nanodiamond, yet relatively little is certain about how and when these products form during the detonation sequence1,2. By understanding these processes, the technological impact of detonation nanodiamond could be mirrored in other pure and doped nanocarbon materials. More generally, revealing the kinetics of carbon condensation in HE products has profound technological and practical implications, e.g., in enabling more efficient production of other potentially useful carbon nanoallotropes, predicting the energy release behavior, identifying failure mechanisms, and decreasing sensitivity of HEs;5 nevertheless, nanocarbon formation and evolution during detonation remain experimentally underexplored because the violent, dynamic, and opaque nature of detonations of even small quantities of HE material are extremely challenging to interrogate—especially with the nanosecond-scale temporal resolution required to monitor product formation kinetics. Thermochemical modeling of HE detonations has matured somewhat faster than complementary experimental techniques and offers instructive, albeit incomplete, insights into the expected condensation products6–13. Many HEs are relatively simple molecular solids composed of carbon, hydrogen, nitrogen, and oxygen, where a negative oxygen balance leads to excess carbon in the detonation products. During detonation, the product species, which are a complex mixture of molecular gases (e.g., N2, H2O, CO, CO2, etc.), ionic species (e.g., OH−, H+, etc.), and carbon condensates, evolve and reach full chemical equilibrium at the Chapman–Jouguet (C–J) point11,12,14, then cool through adiabatic expansion over several microseconds. The thermodynamic properties of carbon along this expansion path (specific to the HE) are inferred by comparison to the carbon phase diagram; however, the size of the condensates is an important factor since the surface energy of nanoscale carbon clusters is a significant term in determining the chemical potential and leads to substantial differences from bulk behavior15. The effects of initiation defects or hot spots, which likely produce higher initial local temperatures, are negligible as they represent a minor volume fraction of the subsequent products. Only a few HEs, including 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) and benzotrifuroxan (BTF), are predicted to reach detonation pressures and temperatures compatible with stable liquid carbon condensates at early times, but no conclusive experimental evidence is currently available. Nonetheless, evidence of the liquid phase is critical for elucidating the location of the carbon liquidus for carbon nanoparticles and may open new avenues for the detonation synthesis of carbon-based materials. The liquid phase of carbon is very difficult to study experimentally and has been observed above the graphite/diamond/ liquid triple point at ~12 GPa/5000 K using laser or Joule heating of bulk carbon16,17. In detonation literature, however, the liquid state is usually inferred from the size and morphology of nanodiamonds in late time detonation products, notably fo (...truncated)


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M. Bagge-Hansen, S. Bastea, J. A. Hammons, M. H. Nielsen, L. M. Lauderbach, R. L. Hodgin, P. Pagoria, C. May, S. Aloni, A. Jones, W. L. Shaw, E. V. Bukovsky, N. Sinclair, R. L. Gustavsen, E. B. Watkins, B. J. Jensen, D. M. Dattelbaum, M. A. Firestone, R. C. Huber, B. S. Ringstrand, J. R. I. Lee, T. van Buuren, L. E. Fried, T. M. Willey. Detonation synthesis of carbon nano-onions via liquid carbon condensation, Nature Communications, DOI: 10.1038/s41467-019-11666-z