Laboratory Investigation of the Active Nitridation of Graphite by Atomic Nitrogen

Zhang, Luning; Pejaković, Dušan A.; Marschall, Jochen; Dougherty, Max; Fletcher, Douglas G.

doi:10.2514/1.t3612

Cited by 27 publications

(7 citation statements)

References 30 publications

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“…This point has been recognized in several previous studies. 11,15 As discussed above, the N-C bond is minimally stable in DFTB relative to the asymptote, which is consistent with the simulation results. The underbinding of N in DFTB relative to the DFT results suggests that the nitrogen atom should perhaps be significantly more sticky and reactive than revealed in the current simulations.…”

Section: Discussionsupporting

confidence: 89%

“…14 Another study of mass-loss measurements from samples of purified graphite (TS = 873 -1373 K) exposed to N atoms showed reaction probabilities of 0.2 -9.8 × 10 -3 . 15 To obtain 4 information on the mechanism of the mass loss, products resulting from such reactions have also been detected using various techniques. [16][17][18] It was found that the dominant product was C2N2, which might have been produced via condensation of the nascent CN radicals produced by the reaction of atomic N with the carbon surface.…”

Section: Introductionmentioning

confidence: 99%

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Exploring reactivity and product formation in N(4S) collisions with pristine and defected graphene with direct dynamics simulations

Nieman

Spezia

Jayee

et al. 2020

The Journal of Chemical Physics

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Atomic nitrogen is formed in the high-temperature shock layer of hypersonic vehicles and contributes to the ablation of their thermal protection systems (TPSs). To gain atomic-level understanding of the ablation of carbon-based TPS, collisions of hyperthermal atomic nitrogen on representative carbon surfaces have recently be investigated using molecular beams. In this work, we report direct dynamics simulations of atomic-nitrogen (N( 4 S)) collisions with pristine, defected, and oxidized graphene. Apart from non-reactive scattering of nitrogen atoms, various forms of nitridation of the graphene were observed in our simulations. Furthermore, a number of gaseous molecules, including the experimentally observed CN molecule, have been found to desorb as a result of N-atom bombardment. These results provide a foundation for understanding the molecular beam experiment and for modeling the ablation of carbon based TPSs and for future improvement of their properties.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Exploring reactivity and product formation in N(4S) collisions with pristine and defected graphene with direct dynamics simulations

Nieman

Spezia

Jayee

et al. 2020

The Journal of Chemical Physics

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“…al. 31 on a high-purity graphite clearly shows that this value is too high: the rate for nitridation reaction was found to be 100 times smaller than the one in Park's model. This confirms that a rate in order of magnitude similar to the one used by Driver et al is probably more accurate.…”

Section: A Argon Flow Fieldmentioning

confidence: 81%

Numerical study of spallation phenomenon in an arc-jet environment

Davuluri

Martin

2014

11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

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The spallation phenomenon might affect the aerodynamic heating rates of re-entry vehicles. To investigate spallation effects, a code is developed to compute the dynamics of spalled particles. The code uses a finite-rate chemistry model to study the chemical interactions of the particles with the flow field. The spallation code is one-way coupled to a CFD solver that models the hypersonic flow field around an ablative sample. Spalled particles behavior is numerically studied for argon and air flow field. The chemistry model is compared with that of Park's model which complies with oxidation and sublimation and shows disagreement for nitridation.

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“…Recent experiments conducted by Zhang et al [40] on a high-purity graphite clearly show that this value is too high: the rate for the nitridation reaction was found to be 100 times smaller than that in the Park et al [6,13] and Park and Bogdanoff's [28] model . This confirms that a rate that is an order of magnitude similar to the one used by Driver and MacLean [26] is probably more accurate.…”

Section: Parametermentioning

confidence: 86%

Numerical Study of Spallation Phenomenon in an Arc-Jet Environment

Davuluri

Zhang

Martin

2016

Journal of Thermophysics and Heat Transfer

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It is hypothesized that spallation could affect the aerodynamic heating rates of reentry vehicles using ablative heat shields. To investigate spallation effects, a code is developed to compute the dynamics of spalled particles. The code uses a finite-rate chemistry model to study the chemical interactions of the particles with the flow field. The spallation code is one-way coupled to a computational fluid dynamics solver that models the hypersonic flow field around an ablative sample. Spalled particle behavior is numerically studied in both argon and air flow fields. Nomenclature A p = area of cross section of the particle, m 2 A s = surface area of the particle, m 2 C D = drag coefficient c i = local concentration of species i at particle surface, mol∕m 3 c v = specific heat at constant volume, J∕mol · K d p = diameter of the particle, m E p = internal energy of the particle, J∕kg E R = energy barrier for reaction, J∕mol F D = drag force, N J C i = vapor flux of C i species, kg∕m 2 · s k f = forward reaction rate, m∕s M = Mach number M w = molar weight, kg∕mol m p = mass of the particle, kg _ m C∕i = mass rate of the particle due to reactions, kg∕s Nu = Nusselt number P = vapor pressure, N∕m 2 p drag = drag power, J∕s _ q = heat rate, J∕s R = universal gas constant Re = Reynolds number based on relative velocity S = molecular speed ratio T = temperature, K U = state vector U ∞ = freestream velocity, m∕s u; v; w = velocity components in axial, radial, and z directions, m∕s V r = relative velocity between particle and fluid, m∕s W = source vector x; y; z = position components in axial, radial, and z directions, m Y i = mass fraction, kg∕kg α v = vaporization coefficient γ 0 = reaction efficiency ΔG f = Gibbs free energy of formation, J∕mol Δh = enthalpy of formation, J∕mol ϵ = emissivity of the particle κ = thermal conductivity, W∕m · K μ = dynamic viscosity, kg∕m · s ν = mean thermal speed, m∕s ρ = density, kg∕m 3 σ = Stefan-Boltzmann constantSubscripts conv = convection f = flow field g = gas phase p = particle rad = radiation rxn = chemical reactions s = solid phase (graphite) sub = sublimation tr = translational-rotational energy mode ve = vibrational-electronic energy mode

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Laboratory Investigation of the Active Nitridation of Graphite by Atomic Nitrogen

Cited by 27 publications

References 30 publications

Exploring reactivity and product formation in N(4S) collisions with pristine and defected graphene with direct dynamics simulations

Exploring reactivity and product formation in N(4S) collisions with pristine and defected graphene with direct dynamics simulations

Numerical study of spallation phenomenon in an arc-jet environment

Numerical Study of Spallation Phenomenon in an Arc-Jet Environment

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