Comparison between Gibbs free energy minimization and mass action law for a multitemperature plasma with application to nitrogen

André, Pascal; Abbaoui, M'Hammed; Bessege, Roger; Lefort, A.

doi:10.1007/bf02766816

Cited by 15 publications

(15 citation statements)

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“…For mixtures containing few components, a composition can be conveniently determined using thermodynamic equilibrium constants for decomposition and ionization reactions, together with the mass conservation law and electrical neutrality, see Ref. [46] and references therein. For more complex mixtures, as we have here, number of chemical reactions between different species becomes very large, and a different approach, based on the minimization of the Gibbs free energy, is more suitable.…”

Section: Methods For Determining Equilibrium Chemical Compositionmentioning

confidence: 99%

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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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Section: Methods For Determining Equilibrium Chemical Compositionmentioning

confidence: 99%

“…This relation is known as the law of mass action 46,83 for a dissociation reaction. Taking into account that N 2 is the major component in the mixture within temperature range considered, and its partial pressure is roughly equal to the total gas pressure p , the following relation for partial pressure of atomic nitrogen is obtained:…”

mentioning

confidence: 99%

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 first generalization from ideal LTE conditions is a two-temperature plasma with electron temperatures higher than heavy particle temperatures. However, the two-temperature model has to be considered already for plasma composition calculations with partition functions of excitation related to the electron temperature and thermal temperatures related to heavy particles [20]. Then in spectra simulation densities can be chosen according to the heavy particle temperature and excitation is determined according to the electron temperature.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Investigation of a Cu—Cr Vacuum Arc

Methling

Gorchakov

Lisnyak

et al. 2015

IEEE Trans. Plasma Sci.

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Experiments on high-current arcs carried out in an ultrahigh vacuum chamber are presented in this paper. For contact separation the lower electrode is moved by a mechanicalpneumatic device simulating the conditions of a vacuum circuit breaker. The arc behavior of the Cu-Cr test electrodes after the electrode separation without application of external magnetic field is observed by a high-speed video camera. Besides the usual electrical measurements, the emission in the gap along the electrode axis is investigated by spatially resolved optical emission spectroscopy. Differences are found in the intensity distribution of atomic and ionic lines along the gap.

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“…The former methods include the two described by Potapov [ 24 ] and van de Sanden et al's [ 25 ] mass action laws, respectively. The latter methods include those of searching minimum Gibbs free energy [ 26 ] and maximum entropy [ 27 ] of a 2T plasma system, respectively. When condensed species are taken into account in the calculation, the latter two methods are preferable due to the modeling simplicity and numerical stability.…”

Section: Methodsmentioning

confidence: 99%

Graphite production in two‐temperature non‐LTE plasmas of C₄F₇N and C₅F₁₀O mixed with CO₂, N₂, and O₂ as eco‐friendly SF₆ replacements: A numerical study

Zhong

2021

Plasma Processes & Polymers

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Many recent works have shown that C4F7N and C5F10O have a great potential to replace SF6 as a greenhouse gas. One of the biggest problems for their application is that condensed species (i.e., graphite) may be produced during gas discharges. However, all the previous works are performed under the assumption of local thermodynamic equilibrium (LTE). Therefore, this study investigates the departure of thermodynamic equilibrium and the corresponding effects on the graphite production in the plasmas of C4F7N, C5F10O, and their mixtures with CO2, N2, and O2, based on the two‐temperature (2T) non‐LTE plasma compositions calculated by the Gibbs free energy minimization. The results show that neglecting the nonequilibrium effect can lead to a very inaccurate description of graphite condensation in the above plasmas.

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Comparison between Gibbs free energy minimization and mass action law for a multitemperature plasma with application to nitrogen

Cited by 15 publications

References 9 publications

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

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

Spectroscopic Investigation of a Cu—Cr Vacuum Arc

Graphite production in two‐temperature non‐LTE plasmas of C₄F₇N and C₅F₁₀O mixed with CO₂, N₂, and O₂ as eco‐friendly SF₆ replacements: A numerical study

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Comparison between Gibbs free energy minimization and mass action law for a multitemperature plasma with application to nitrogen

Cited by 15 publications

References 9 publications

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

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

Spectroscopic Investigation of a Cu—Cr Vacuum Arc

Graphite production in two‐temperature non‐LTE plasmas of C4F7N and C5F10O mixed with CO2, N2, and O2 as eco‐friendly SF6 replacements: A numerical study

Contact Info

Product

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Graphite production in two‐temperature non‐LTE plasmas of C₄F₇N and C₅F₁₀O mixed with CO₂, N₂, and O₂ as eco‐friendly SF₆ replacements: A numerical study