Wide-temperature-range kinetics of the BO reactions with O2, HCl, and CO2, comparison to AlO reactions

Belyung, David P.; Dalakos, George T.; Rocha, John-David R.; Fontijn, Arthur

doi:10.1016/s0082-0784(98)80409-8

Cited by 5 publications

(11 citation statements)

References 34 publications

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“…It is particularly relevant to note the difference in stability between HBO and HOB, since a possible role for the latter has been mentioned on several occasions. ,,, The data in Table indicate that this is likely to be minimal.…”

Section: Resultsmentioning

confidence: 99%

“…F. Heats of Reaction. Table lists 83 reactions that have been implicated or suggested as being involved, in either the forward or reverse direction, in the ignition and/or combustion of boron. ,,,,,,,, …”

Section: Resultsmentioning

confidence: 99%

“…These include the formation of a protective oxide layer which hinders the ignition of the boron particles, the generation of boron oxyhydride intermediates which impede the combustion process, and a slow rate of condensation to the desired liquid or solid final product. It has been found that improvements in both ignition and combustion efficiency can be realized by the inclusion of fluorine in the formulation, e.g., as NF 2 functional groups on the oxidizers and/or binders. − This does not diminish the potential energy release; for example, the conversion of boron to BF 3 (g) produces about 27 kcal per gram of boron…”

Section: Introductionmentioning

confidence: 99%

“…Extensive efforts are underway to quantitatively model the complex processes of boron ignition and combustion in oxygen/fluorine systems. − These modeling studies require considerable thermodynamic and kinetic data (e.g., heats of reaction, activation barriers, etc. ), not all of which are currently known with sufficient accuracy. ,, In the present work, we have applied high-level computational techniques to obtain enthalpies, free energies, and heats of formation for 66 atoms and molecules that have been implicated in the oxygen/fluorine oxidation of boron. These results can be used to find heats of reaction and equilibrium constants for several hundred possible ignition and combustion steps.…”

Section: Introductionmentioning

confidence: 99%

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Computational Determination of the Energetics of Boron Ignition/Combustion Reactions

1999

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Two computational procedures, the density functional B3PW91/6-311+G(2df,2pd) and the ab initio CBS-Q, have been used to calculate optimized geometries, energy minima at 0 K and enthalpies and free energies at 298 K for atoms and molecules involved in the ignition and/or combustion of boron. Calculated gas-phase heats of formation are presented for 58 atoms and molecules and are used to find heats of reaction for 83 possible ignition/combustion steps. The most exothermic are found to be BO + F f FBO and BO + O f BO 2 . It is shown that ∆H (298 K) and ∆H (2000 K) differ, on the average, by only 1.5 kcal/mol; however, ∆G can change quite considerably over the same temperature range. Relative stabilities and equilibrium constants are given for five pairs of isomers. While the geometries were obtained more accurately by the B3PW91 procedure, the CBS-Q is more reliable for heats of formation and heats of reaction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Computational Determination of the Energetics of Boron Ignition/Combustion Reactions

1999

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“…Because of the large negative enthalpies of formation of both liquid and solid Al 2 O 3 , −387.325 and −400.5 kcal/mol, the oxidation of metallic aluminum to either of these products is accompanied by a heat release of more than 7 kcal/g of aluminum. This potential as an energy source, as well as the ability of aluminum particles to help reduce combustion instability in rocket motors, has led to their frequent use as an ingredient in propellant formulations. , There is accordingly a continuing effort, through extensive experimental and modeling studies, to develop a better quantitative understanding of the processes involved in aluminum ignition and combustion. − Considerable thermodynamic and kinetic data are required as input for the modeling (e.g., heats of formation, activation barriers, etc. ), some of which are not currently available or are not reliable. , For example, Belyung et al have quoted heats of reaction with uncertainties of as much as 22 kcal/mol .…”

Section: Introductionmentioning

confidence: 99%

Energetics of Aluminum Combustion

2001

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Aluminum continues to be of great interest as a fuel in propellant formulations. Quantitative modeling of the multistep ignition and combustion processes requires considerable thermodynamic and kinetic data, some of which are currently not available or not reliable. We have accordingly carried out CBS-QB3 calculations of the enthalpies and free energies, at 298 and 2000 K, of atoms and molecules that are likely to be involved in the combustion of aluminum-based propellants. These have been used to find the respective heats of formation, as well as the heats of reaction and equilibrium constants for numerous possible steps in the ignition/combustion processes. In a few instances, we also determined transition states and activation barriers. Certain interesting aspects of the results are discussed in greater detail.

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