Synthesis of nanoparticles in carbon arc: measurements and modeling

Yatom, Shurik; Khrabry, Alexander; Mitrani, James; Khodak, Andrei; Kaganovich, Igor; Vekselman, V.; Stratton, B. C.; Raitses, Yevgeny

doi:10.1557/mrc.2018.91

Cited by 25 publications

(28 citation statements)

References 51 publications

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“…We also find that these features should be clearly distinguishable from the background signal for particles as small as C 60 at concentrations in excess of 1 particle per million of gas molecules. These concentrations are in excess of estimates based on the measured carbon deposits on a substrate placed in the arc periphery59. Nanoparticles more asymmetric than those considered in our study should be detectable at even lower concentrations.…”

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confidence: 80%

In situ Characterization of Nanoparticles Using Rayleigh Scattering

Santra

Shneider

Car

2017

Sci Rep

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We report a theoretical analysis showing that Rayleigh scattering could be used to monitor the growth of nanoparticles under arc discharge conditions. We compute the Rayleigh scattering cross sections of the nanoparticles by combining light scattering theory for gas-particle mixtures with calculations of the dynamic electronic polarizability of the nanoparticles. We find that the resolution of the Rayleigh scattering probe is adequate to detect nanoparticles as small as C60 at the expected concentrations of synthesis conditions in the arc periphery. Larger asymmetric nanoparticles would yield brighter signals, making possible to follow the evolution of the growing nanoparticle population from the evolution of the scattered intensity. Observable spectral features include characteristic resonant behaviour, shape-dependent depolarization ratio, and mass-dependent line shape. Direct observation of nanoparticles in the early stages of growth with unobtrusive laser probes should give insight on the particle formation mechanisms and may lead to better-controlled synthesis protocols.

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confidence: 80%

In situ Characterization of Nanoparticles Using Rayleigh Scattering

Santra

Shneider

Car

2017

Sci Rep

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“…In Ref. [43], simulations predicted coincidently the same parameters as in ICP system 22 . This result is in agreement with ex-situ TEM image of boron droplets with nanotubes grown on them (see Figure 3 in Ref.…”

Section: Iiif Estimation Of Boron Droplets Size Upon Formation Of Bmentioning

confidence: 61%

Determining the gas composition for the growth of BNNTs using a thermodynamic approach

Khrabry

Kaganovich

Yatom

et al. 2019

Phys. Chem. Chem. Phys.

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A high-yield production of high-quality boron-nitride nanotubes (BNNTs) was reported recently in several publications. A boron-rich material is evaporated by a laser or plasma in a nitrogen-rich atmosphere to supply precursor gaseous species for nucleation and growth of BNNTs. Either hydrogen was added or pressure was increased in the system to achieve high yield and high purity of the synthesized nanotubes. According to the widely-accepted "root grow" mechanism, upon the gas cooling, boron droplets form first, then they adsorb nitrogen from surrounding gas species, and BNNTs grow on their surfaces. However, what are these precursor species that provide nitrogen for the growth is still an open question. To answer this question, we performed thermodynamic calculations of B-N mixture composition considering broad set of gas species. In enhancement of previous studies, the condensation of boron is now taken into account and is shown to have drastic effect on the gas chemical composition. B 2 N molecules were identified to be a major source of nitrogen for growth of BNNTs. Presence of B 2 N molecules in a B-N gas mixture was verified by our spectroscopic measurements during a laser ablation of boron-rich targets in nitrogen. It was shown that the increase of pressure has a quantitative effect on the mixture composition yielding increase of the precursor density. The hydrogen addition might open an additional channel of nitrogen supply to support growth of BNNTs. Nitrogen atoms react with abundant H 2 molecules to form NH 2 and then NH 3 precursor species, instead of just recombining back to inert N 2 molecules, as in the no-hydrogen case. In addition, thermodynamics was applied in conjunction with agglomeration theory to predict the size of boron droplets upon growth of BNNTs. Analytical relations for identification of crucial species densities were derived.

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“…The gas 5 temperature drops rapidly outside the plasma with values of 4500 K at 3 mm and 3500 K at 4 mm. Our work shows that nanomaterial growth occurs primarily in the region outside the plasma core [23]. The in situ diagnostics described in this paper probe both the plasma core and the hot gas region.…”

Section: Arc Plasma Experimental Arrangementmentioning

confidence: 81%

“…The plasma column is confined to the region between the anode and cathode and has a diameter of ~6 mm. The gas temperature in the plasma core is 8000 K [11,23]. The gas 5 temperature drops rapidly outside the plasma with values of 4500 K at 3 mm and 3500 K at 4 mm.…”

Section: Arc Plasma Experimental Arrangementmentioning

confidence: 99%

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In situ diagnostics for nanomaterial synthesis in carbon arc plasma

Stratton

Gerakis

Kaganovich

et al. 2018

Plasma Sources Sci. Technol.

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Developments in the recent application of in situ diagnostics to improve understanding of nanomaterial synthesis processes in carbon arc plasma are summarized. These diagnostics measure the plasma conditions in the arc core and the precursor species to nanoparticle formation and the presence and sizes of nanoparticles in the synthesis region surrounding the hot arc core. They provide information that could not be obtained by the ex situ diagnostics used in previous studies of nanomaterial synthesis in arc plasma. The following diagnostics are covered: Optical Emission Spectroscopy, Planar Laser Induced Fluorescence, Laser Induced Incandescence, Fast Frame Imaging, Coherent Rayleigh Brillouin Scattering, and the Nanomaterial Extractor Probe. The diagnostic measurements are consistent with a recently developed two-dimensional fluid model of nanomaterial synthesis in the arc plasma.

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Synthesis of nanoparticles in carbon arc: measurements and modeling

Cited by 25 publications

References 51 publications

In situ Characterization of Nanoparticles Using Rayleigh Scattering

In situ Characterization of Nanoparticles Using Rayleigh Scattering

Determining the gas composition for the growth of BNNTs using a thermodynamic approach

In situ diagnostics for nanomaterial synthesis in carbon arc plasma

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