Neutron Study of Multilevel Structures of Diamond Gels

Лебедев, В. Т.; Kulvelis, Yu. V.; Vul, A. Ya.

doi:10.3390/condmat1010010

Cited by 28 publications

(14 citation statements)

References 21 publications

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“…The morphology of DND obtained from the recovered detonation can be directly compared with that obtained in situ by comparing the general features of the USAXS in Figure a with those obtained by TR-SAXS (Figure ). Both the USAXS and TR-SAXS contain a broad Guinier knee that is preceded by a power-law-like decay in intensity and is followed by a steep decay that deviates from Porod decay, similar to the behavior previously reported in the literature. , While it is common in SAS analysis to simply fit a power-law decay to this region and draw conclusions about the surface from the exponent, a distinct approach is adopted in this paper: the deviation from Porod decay is addressed first, followed by a comprehensive model that accounts for both the particle size and surface. To demonstrate the deviation from Porod scattering, the high- q portion of the TR-SAXS data was fit to the equation where the prefactor, B , and flat background, b , are varied to fit the intensity in the q -range: 0.12 Å –1 < q < 0.4 Å –1 .…”

Section: Resultsmentioning

confidence: 68%

Resolving Detonation Nanodiamond Size Evolution and Morphology at Sub-Microsecond Timescales during High-Explosive Detonations

et al. 2019

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Characterization of the initial morphology of detonation nanodiamond (DND) has been the focus of many research studies that aim to develop a fundamental understanding of carbon condensation under extreme conditions. Identifying the pathways of DND formation has the potential for significant impact on many of the controlled synthesis of nanoscale carbon with a tailored functionality; currently, a wide range of possible (and conflicting) mechanisms of nucleation and growth have been proposed, and further research is essential. Building a comprehensive understanding of DND formation is challenging because it requires in situ characterization on the sub-microsecond (sub-μs) timescale during a high-explosive detonation. In this study, time-resolved small-angle X-ray scattering (TR-SAXS) is used to reveal the early-stage DND morphology from <0.1 to 6 μs after the detonation front passes through the X-ray beam path. We address the ambiguity of models previously reported for the analysis of small-angle scattering from DND by comparing (i) in situ, TR-SAXS recorded during early-stage particulate formation and (ii) ex situ SAXS and transmission electron microscopy (TEM) measurements of products recovered from detonation of the same high explosive within a carefully designed ice chamber. The SAXS from both late-time (>1 μs) in situ and recovered DND exhibits consistent features in the I(q) curve. Such a close similarity allows a high-fidelity SAXS model derived from the ex situ SAXS and TEM measurements to be applied to the in situ data, which yields new insight into the early-stage (<1 μs) morphology of DND. Our analysis indicates that the size distribution of DND particles is observed within 0.1 μs postdetonation, which indicates that carbon is condensed within the reaction zone. Between 0.1 and 0.3 μs, the mean size of the diamond particles increases slightly toward 4 nm, and evidence of surface texture is observed. Based on TEM imaging, this surface texture consists of hemispherical protrusions that extend ∼1 nm from the surface. Beyond 0.3 μs, neither the mean size of the diamond core nor the surface texture changes significantly for several microseconds after the detonation. Combined with thermochemical simulations, these results indicate that during detonation of composition B, carbon is condensed into nanoscale diamond much faster than that previously reported in other studies. Furthermore, the surface texture of the DND is shown to arise during condensation rather than via subsequent graphitization.

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Section: Resultsmentioning

confidence: 68%

Resolving Detonation Nanodiamond Size Evolution and Morphology at Sub-Microsecond Timescales during High-Explosive Detonations

et al. 2019

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“…In this mechanism, the DND particles immediately attach when they collide. Interestingly, the mass fractal dimensions, d, are slightly lower than those reported from DND colloids measured ex situ using small-angle neutron scattering 44,45 (SANS) and SAXS, 46 where values of d greater than 2 were found. To understand whether DLA may indeed be the mechanism responsible for the structures inferred from the experimental data, the time needed by a typical DND primary particle to diffuse over the average interparticle distance (L), τ = L 2 /D B , at the Chapman−Jouguet point (D B , primary particle diffusion constant) was estimated.…”

mentioning

confidence: 68%

Submicrosecond Aggregation during Detonation Synthesis of Nanodiamond

Hammons

Nielsen

Bagge‐Hansen

et al. 2021

J. Phys. Chem. Lett.

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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.

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“…Many models exist for small angle scattering from detonation nanodiamond and each has its advantages and limitations. In most cases, detonation nanodiamond is considered to be aggregated spherical particles with a surface that is not necessarily smooth nor well‐defined, as the high‐q scattering does not follow a perfect Porod decay . Here, the model accounts for the departure from Porod scattering by including surface texture, as it mimics the morphology observed by TEM imaging and has been proven to reproduce an accurate size distribution from the SAXS data .…”

Section: Discussionmentioning

confidence: 99%

Observation of Variations in Condensed Carbon Morphology Dependent on Composition B Detonation Conditions

Hammons

Nielsen

Bagge‐Hansen

et al. 2020

Propellants Explo Pyrotec

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Carbon particulates generated during detonation depend upon high explosive type, composition, and detonation conditions. Although explosive composition greatly affects particulates, the focus of this work is on how detonation geometries that induce much higher temperatures and pressures in the high explosive lead to differing particulate morphologies. In this study, two geometries were used: Detonations were initiated in Composition B cylinders at one end in conventional detonations and initiated at both ends to produce colliding detonations. Each of these detonations was observed on the sub‐μs timescale using fast radiography capturing images of the front moving through the cylinder, and colliding detonation fronts in real‐time. These imaging experiments were complemented with time‐resolved small‐angle x‐ray scattering (SAXS) experiments that were able to observe and determine the varying condensed carbon morphologies at different locations and times in each detonation. The detonations could be timed in such a way that the spatial and temporal dependence of the carbon morphology could be superimposed onto radiography images collected at the same point in time. The complementary approach is able to show that the carbon condensates are much larger when formed in the elevated temperature and pressure conditions near the location of colliding detonation fronts. Thermochemical modeling suggests that these larger particulates form either in the diamond phase or on the liquidus line of the carbon phase diagram. The increase in size observed by SAXS may correlate well with the increased residence time deeply in the diamond phase. These particulates can be described as nano‐sized phases with some surface texture or otherwise near‐surface intra‐particle heterogeneity.

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Neutron Study of Multilevel Structures of Diamond Gels

Cited by 28 publications

References 21 publications

Resolving Detonation Nanodiamond Size Evolution and Morphology at Sub-Microsecond Timescales during High-Explosive Detonations

Resolving Detonation Nanodiamond Size Evolution and Morphology at Sub-Microsecond Timescales during High-Explosive Detonations

Submicrosecond Aggregation during Detonation Synthesis of Nanodiamond

Observation of Variations in Condensed Carbon Morphology Dependent on Composition B Detonation Conditions

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