Heats of Formation of Metallic Borides by Fluorine Bomb Calorimetry

Domalski, Eugene S.; Armstrong, George T.

doi:10.21236/ad0625336

Cited by 4 publications

(6 citation statements)

References 18 publications

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“…m, Tenon, g. (m vacuo) The observed heat of combustion for the sample of Teflon was AHfag = -246.84 ± 0.07 kcal. mole"1 for reaction 1. C2F4 (solid, polymer) + 2F2(g) = 2CF,(g) (1) The previously reported value (5) was AHfag = -247,43 ± 0.01 kcal. mole"1.…”

Section: Resultsmentioning

confidence: 97%

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Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Wood¹,

Lagow²,

Margrave³

1967

J. Chem. Eng. Data

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The heat of combustion in fluorine of a Teflon sample whose heat of formation was previously known has been determined as -246.84 ± 0.07 kcal. mole-1. This information combined with other available thermodynamic data gives °[CF4( g) ] = -223 ± 1 kcal. mole -1.In RECENT years numerous workers have determined the heat of formation of CF4(g) both by direct and indirect methods. The early value of zlfí/'[CF4(g) ] reported by von Wartenberg (19) of -162 ± 2 kcal. mole-1 by the direct combination of the elements was in error owing to the formation of higher fluorides. During the period of 1954-65, the reported values for Ai/f[CF4(g)] approached -219.0

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Section: Resultsmentioning

confidence: 97%

“…Perhaps the most obvious method of determining AHf[CF4(g)] is by the direct fluorination of graphite in a reaction bomb. Recently Domalski and Armstrong (5) have reported a heat of fluorination for graphite which yields AJí? [CF4(g)] = -222.87 ± 0.04 kcal.…”

mentioning

confidence: 99%

Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Wood¹,

Lagow²,

Margrave³

1967

J. Chem. Eng. Data

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“…This is, for instance, reflected in the change in formation enthalpies, with the enthalpy values becoming less negative, with increasing W addition to silicides such as the A15 phase [22]. The thermodynamics of borides of tungsten and molybdenum have been studied extensively theoretically and experimentally [43,44], and the formation enthalpies of Molybdenum borides and tungsten borides are similar. Consequently, the partitioning is driven by maximizing Mo-Si bonds at the expense of W-Si bonds.…”

Section: Resultsmentioning

confidence: 99%

Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating

Ray

Thimmaiah

Kramer

et al. 2019

Applied Surface Science

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The oxidation behavior and microstructures of a three phase Mo50W20Si15B15 alloy containing (Mo,W) solid solution, (Mo,W)5Si3 and (Mo,W)5SiB2 were investigated over the 1000 -1300°C temperature range. At 1300°C, the alloy exhibited a large initial mass loss and eventually transitioned to a steady state behavior associated with the development of an amorphous borosilica scale. The oxidation resistance at lower temperature was unsatisfactory due to the pesting of Mo and W. Grazing Incident Angle X-ray Diffraction (GIXRD) measurements during the initial transient stage of oxidation identified the evolution of surface oxide products that were responsible for the large weight loss and pesting behavior. In order to address the large initial weight loss and the low temperature pesting behavior, the alloy was coated with a Mo-Si-B based coating by employing the pack cementation process followed by a conditioning treatment at 1450°C. The microstructures of the coatings and the interlayer between the base alloy and the coating were studied, and the oxidation resistance of the coated alloys was evaluated over the 800 -1300°C temperature range. The coated alloy showed improved oxidation resistance with nearly zero mass change for extended period of time over the entire range of temperatures studied.

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“…The heats of reactions are readily available, either from such compilations as NIST − JANNAF tables (available online as NIST Chemistry webbook), summary by Fischer and Grubelich, and other sources. An overview shown in Figure was prepared using, in addition to the above databases, data from refs . It presents heats of reaction normalized per gram and per cubic centimeter of metal fuels for formation of fluorides, oxides, borides, and carbides.…”

Section: Rsm Compositions Based On the Heat Release And Densitymentioning

confidence: 99%

Reactive Structural Materials: Preparation and Characterization

Hastings

Dreizin

2017

Adv Eng Mater

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Reactive structural materials, which can serve both as structural elements as well as a source of chemical energy released upon initiation have emerged as an important class of metal-based composites for use in various energetic systems. Such materials rely on a variety of exothermic reactions, from oxidation to formation of metal-metalloid and intermetallic phases. The rates of these reactions are as important as the energy that may be released, in order for them to occur at the time scales compatible with the requirements of applications. Therefore, chemical composition, scale at which reactive components are mixed, and the structure and morphology of materials are important and can be controlled by the method of preparation and compaction of the composite materials. Methods of preparation of the composite structures are briefly reviewed as well as methods of characterization of their mechanical and energetic properties. In addition to common thermo-analytical and static mechanical property measurements, dynamic tests of mechanical properties as well as ignition and combustion experiments are necessary to understand the fragmentation, initiation, and heat release expected for these materials when they are stimulated by an impact, shock, or rapid heating. Reaction mechanisms are studied presently for the thin layers and small samples of reactive materials initiated in carefully designed experiments. In other experiments, impact and explosive initiation are characterized for larger material compacts in the conditions imitating practical scenarios. Examples of results describing thermal, impact, and explosive initiation of some of the reactive materials are presented.

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Heats of Formation of Metallic Borides by Fluorine Bomb Calorimetry

Cited by 4 publications

References 18 publications

Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating

Reactive Structural Materials: Preparation and Characterization

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Heats of Formation of Metallic Borides by Fluorine Bomb Calorimetry

Cited by 4 publications

References 18 publications

Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Heat of combustion of Teflon in fluorine. A check on the heat of formation of carbon tetrafluoride

Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating

Reactive Structural Materials: Preparation and Characterization

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Product

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Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating