Thermodynamic analysis of the combustion of metal powders and their oxides in phosphorus and of the combustion of the phosphides formed in oxygen

Chernogorenko, V. B.; Lynchak, K. A.

doi:10.1007/bf02672721

Cited by 3 publications

(1 citation statement)

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“…Magnesium can react with PTFEP forming both the fluoride (MgF 2 ) and oxide (MgO). In addition reactions with both nitrogen and phosphorus are feasible although the nitride and phosphide have modest enthalpy of formation, D f H-(Mg 3 N 2 ) = À461 kJ mol À1 , D f H(Mg 3 P 2 ) = À450 kJ mol À1 [19] and only low oxidative stability in a combustion environment as was demonstrated earlier [2,3,20]. Hence the magnesium pnictides -though present as transient specieswill not be considered as final combustion products under aerobic conditions.…”

Section: Thermochemical Calculation Of Mg/ptfepmentioning

confidence: 95%

Metal Fluorocarbon Pyrolants, XVI : Theoretical and Experimental Investigation of Poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PTFEP) as Oxidizer in Magnesium Based Pyrolants

Koch

Contini

2014

Propellants Explo Pyrotec

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Consolidated magnesium/poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (MPZ) pyrolants display a stable combustion regime between ξ(Mg) 30–83 wt‐%. The combustion rate increases with increasing magnesium content. Mixtures containing between 15–29 wt‐% Mg do ignite with a butane torch but extinguish rapidly thereafter. The combustion flames for each stoichiometric range exhibit particular features such as luminous carbon particles, after burn luminescence of Mg and burning Mg‐rich ejecta. UV/Vis spectra of the combustion flames show a distinct continuum superimposed from signals for transient CF2, Mg, MgF, MgO, P2+, PH, PN, and PO. The thermochemical calculation using NASA‐CEA indicate the highest adiabatic temperatures 1889 K at ξ(Mg)=35 wt‐%. The aerobic combustion of MPZ yields similar temperatures as common magnesium/polytetrafluoroethylene pyrolants.

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Section: Thermochemical Calculation Of Mg/ptfepmentioning

confidence: 95%

Metal Fluorocarbon Pyrolants, XVI : Theoretical and Experimental Investigation of Poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PTFEP) as Oxidizer in Magnesium Based Pyrolants

Koch

Contini

2014

Propellants Explo Pyrotec

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Semiconductor thermochemistry in density functional calculations

2008

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The local-density and generalized gradient approximations ͑LDA and GGA͒ to density functional theory ͑DFT͒ exhibit incomplete error cancellation when energy differences are taken between chemically dissimilar systems. This energy inconsistency is manifested, e.g., in the tendency to underestimate the heat ͑enthalpy͒ of formation of semiconducting and insulating compounds in LDA and, even more so, in GGA. Considering a set of 61 compounds that can be formed from 14 elements ͑cations: Cu, Mg, Ca, Zn, Cd, Al, Ga, and In; anions: N, P, As, O, S, and Se͒, optimized elemental reference energies are determined by least-squares error minimization of an overdetermined set of linear equations. These elemental energies are "optimally consistent" with the DFT energies of the semiconductor compounds and imply corrections of up to 1 eV compared to the respective LDA or GGA energies. While these "corrections" are not to be understood to yield the correct absolute total energies of the elements, they are proposed to give appropriate bounds for the chemical potentials for thermodynamic processes in semiconductors and insulators, such as, e.g., defect formation, surface reconstruction, or catalytic processes. The present model allows to evaluate thermodynamic processes using DFT energy differences taken only between systems that are expected to show good error cancellation.

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Thermal Decomposition of Calcium Hypophosphite

Верещагин,

Минин,

Бычин

et al. 2024

Южно-Сибирский Научный Вестник

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Термическое разложение гипофосфита кальция изучали методом синхронного термического анализа ДТА/ТГА в диапазоне температур от 25°C до 600 °C со скоростью нагревания 10 град/мин в атмосфере азота и в атмосфере воздуха. В атмосфере азота разложение состоит из обширного экзоэффекта, состоящего из четырех последовательных стадий с максимумами при 368, 386, 400 и 434 °C с суммарным тепловыделением 1,51 кДж/г. При разложении в атмосфере воздуха наблюдается экзоэффект с тепловыделением 9,01 кДж/г.При этом было Экспериментально установлено увеличение массы образца в области 370-400 °С 6 масс.%, что может быть объяснено окислением фосфора. Образующиеся конденсированные продукты термического разложения представляют собой пористую массу красно-коричневого цвета, что может быть объяснено образованием промежуточного продукта разложения - фосфида кальция. Образование фосфида кальция термодинамически предпочтительно при взаимодействии продуктов разложения гипофосфита кальция – оксида кальция и фосфина. Удельная теплота образования оксида кальция в 4,18 раза больше значений удельной теплоты образования фосфида. В связи с этим можно предположить, что образование фосфида, - промежуточного продукта, обусловлено неравновесностью процесса, кинетическим факторами и диффузионными ограничениями, поскольку фосфид кальция термодинамически устойчив до 1000 °С. Ранее эти факторы рассматривались применительно к процессам самораспространяющегося высокотемпературного синтеза фосфидов. К тому же образование оксида кальция и фосфина in suti в процессе термораспада в соответствие с эффектом Хедвала может объяснить высокую скорость образования фосфида кальция и его сохранность. The thermal decomposition of calcium hypophosphite was studied by synchronous DTA/TGA thermal analysis in the temperature range from 25 °C to 600 °C at a heating rate of 10 deg/min in a nitrogen atmosphere and in an air atmosphere. In nitrogen atmosphere, the decomposition consists of an extensive exo-effect consisting of four consecutive stages with maxima at 368, 386, 400 and 434 °C with a total heat release of 1.51 kJ/g. Upon decomposition in an air atmosphere, an exoeffect with a heat release of 9.01 kJ/g was observed. An increase of the sample mass in the region 370-400 °C of 6 wt.% was experimentally found, which can be explained by the oxidation of phosphorus. The formed condensed products of thermal decomposition are a porous mass of red-brown color, which can be explained by the formation of an intermediate product of decomposition - calcium phosphide. Formation of calcium phosphide is thermodynamically preferable in the interaction of calcium oxide and phosphine, the products of decomposition of calcium hypophosphite. The specific heat of formation of calcium oxide is 4.18 times higher than the values of specific heat of formation of phosphide. In this connection it is possible to assume that the formation of phosphide, - an intermediate product, is conditioned by non-equilibrium of the process, kinetic factors and diffusion limitations, since calcium phosphide is thermodynamically stable up to 1000 °С. Previously, these factors were considered in relation to the processes of self-propagating high-temperature synthesis of phosphides. In addition, the formation of calcium oxide and phosphine in suti during thermal decay in accordance with the Headwall effect can explain the high rate of calcium phosphide formation and its preservation.

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Thermodynamic analysis of the combustion of metal powders and their oxides in phosphorus and of the combustion of the phosphides formed in oxygen

Cited by 3 publications

References 1 publication

Metal Fluorocarbon Pyrolants, XVI : Theoretical and Experimental Investigation of Poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PTFEP) as Oxidizer in Magnesium Based Pyrolants

Metal Fluorocarbon Pyrolants, XVI : Theoretical and Experimental Investigation of Poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PTFEP) as Oxidizer in Magnesium Based Pyrolants

Semiconductor thermochemistry in density functional calculations

Thermal Decomposition of Calcium Hypophosphite

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