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.
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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)