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Direct Determination Of γ′ / γ′+γ / γ Phase Boundaries in Ni-Al-Cr System Based on Enthalpy of Formation Results Obtained by Calorimetric Solution Method

Maciąg T., Rzyman K., Węcki B.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 3A

1657--1662

EN

he work is a continuation of the research carried out on a high-temperature calorimeter solution type on alloys from Ni-Al-Cr system. Thanks to the construction innovation introduced by authors the device allows the determination of the formation enthalpy of alloys at ambient and elevated temperatures. Experiments described in this article were carried out at three temperatures: 873K, 996K and 1150K on the alloys of the chemical compositions from the Ni75Al25 ÷ Ni87Cr13 section of the Ni-Al-Cr system. On the basis of changes in the enthalpy of formation with increasing chromium content of the alloys, points corresponding to places of phase boundaries γ′ / γ′+γ / γ in Ni-Al-Cr system were determined. A similar relationship was observed in previous studies of alloys from Ni75Al25÷Ni75Cr25 section. For precise determination of these characteristic points a statistical model was applied.

PL

Praca jest kontynuacją badań prowadzonych na skonstruowanym przez autorów wysokotemperaturowym kalorymetrze typu rozpuszczania. Urządzenie pozwala na określanie entalpii tworzenia stopów w podwyższonej temperaturze. Opisywane badania przeprowadzono w trzech temperaturach: 873K, 996K i 1150K na stopach o składach chemicznych znajdujących się na linii Ni75Al25÷Ni87Cr13 układu Ni-Al-Cr. Na podstawie zmian wartości entalpii tworzenia wraz ze wzrostem zawartości chromu w stopach stwierdzono istnienie punktów odpowiadających miejscom występowania granic międzyfazowych γ′ / γ′+γ / γ w układzie Ni-Al-Cr. Podobną zależność zaobserwowano w poprzednich badaniach dotyczących obszaru Ni75Al25÷Ni75Cr25. Aby precyzyjnie wyznaczyć te charakterystyczne punkty opracowano i zastosowano model statystyczny.

2

Paliwa stałe jako chemiczne molekuły CxHyOz – aspekty termodynamiczne i kinetyczne

Ściążko M., Stępień L.

Chemik

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2013

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Vol. 67, nr 5

379--386

PL

Węgiel jest przykładem złożonej substancji chemicznej o niezidentyfikowanym wzorze podstawowej molekuły. Zarówno energetyczne bilansowanie procesów jak i kinetyczne obserwacje przebiegu reakcji wymagają znajomości w pierwszym przypadku entalpii tworzenia, a w drugim odpowiednich parametrów kinetycznych. Istotne jest również, aby korelowały one z właściwościami danego węgla i pozycjonowały go odpowiednio w systemie klasyfikacyjnym. W pracy zaproponowano metodologię określania entalpii tworzenia węgla oraz jego odpowiednich parametrów kinetycznych.

EN

Coal is an example of complex chemical substance of unidentified formula of the basic molecule. Both the energy balancing of processes and kinetic observation of the reaction course require knowledge – of the formation enthalpy in the former case and of appropriate kinetic parameters in the latter case. It is also important that they would correlate with properties of specific coal and would appropriately position it in the classification system. The paper suggests a methodology for determination of coal formation enthalpy and of appropriate kinetic parameters.

3

Bomb Calorimetric Correlation Study between Chemical Structure and Enthalpy of Formation for a Linear Energetic Polyphosphazene

Bellamy A. J., Contini A. E., Golding P.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 1

3--15

EN

Energetic polyphosphazenes constitute a novel class of insensitive binders which potentially outperform conventional carbon-based systems in terms of their energy-densities and glass transition temperatures. To facilitate the calculation of energetic performance for these materials, we report here on the use of bomb calorimetry to determine the standard enthalpies of combustion (ΔcH°) and formation (ΔfH°) of 2,2,2-trifuoroethan-1-oxy-/2,3-dinitratopropan-1-oxy-polyphosphazene (I) as the proportion of (energetic) 2,3-dinitratopropan-1-oxy substituents (% Energetic Substitution, % ES) is varied between 31% and 78%. Similar data is presented for the parent polymer bis(2,2,2-trifuoroethan-1-oxy)-polyphosphazene (II) (% ES = 0). ΔcH° was found to vary between -2275 kJ·mol-11for the parent polymer II (% ES = 0) and -3415 kJ·mol-1 for I with % ES = 78. The corresponding values for ΔfH° were -3184 kJ·mol-1 and -1566 kJ·mol-1. These data indicate that, as expected, the polymer heats of formation become more favourable – with respect to the energetic performance of the polymer – as the percentage of energetic side chain functionalities (% ES) increases.

4

Some Perspectives on Estimating Detonation Properties of C, H, N, O Compounds

Politzer P., Murray J. S.

Central European Journal of Energetic Materials

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2011

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Vol. 8, nr 3

209-220

EN

We have explored various aspects of the Kamlet-Jacobs equations for estimating detonation velocities and pressures. While the loading density of the explosive compound is certainly an important determinant of these properties, its effect can sometimes be overridden by other factors, such as the detonation heat release and/or the number of moles of gaseous products. Using a gas phase rather than solid phase enthalpy of formation in obtaining a compound's heat release can produce a signifcant error in the calculated detonation velocity. However a negative enthalpy of formation is not necessarily incompatible with excellent detonation properties. Additional evidence is presented to support Kamlet and Jacobs' conclusion that, for C, H, N, O explosives, assuming the detonation product composition to be N2(g)/H2O(g)/CO2(g)/C(s) gives overall quite satisfactory results.

5

Basic Characteristics for Estimation Polynitrogen Compounds Effciency

Smirnov A., Lempert D., Pivina T., Khakimov D.

Central European Journal of Energetic Materials

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2011

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Vol. 8, nr 4

233-247

EN

Basing on analysis of experimental data for physicochemical parameters of 300 energetic compounds from different chemical classes, a set of basic characteristics (enthalpies of formation, molecular crystals densities, detonation parameters, as well as sensitivity to different kinds of impact) has been considered and some calculations schemes have been elaborated to estimate these characteristics for polynitrogen compounds. The limits of physicochemical values for energetic materials (EMs) parameters have been estimated. A large set of compounds has been investigated and some of them seem to be rather effective as explosives or monopropellants. There are about ten powerful compounds (e.g. octanitrocubane, hexanitrohexaazaisowurtzitane, azanitrofurazan, etc.), explosives- oxidizers (such as ammonium dinitroamide and bis(difuroamine-dini troethil) nitroamine) and several hypothetic substances (not synthesized yet), such as octaazacubane, octaazatetraen, tetranitrotetraazacubane etc. Energetic properties were estimated as for individual compounds, as well as for energetic compositions containing these substances together with other ones in the aim to estimate the effectiveness of their use as components of solid composite propellants.

6

Density functional study of Mg2FeH6 complex hydride

Zhang J., Huang Y. N., Long G. G., Zhou D. W., Liu J. S.

Materials Science Poland

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2010

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Vol. 28, No. 1

357--366

EN

Mg2FeH6, which has the highest volumetric hydrogen density, is considered a promising hydrogen storage material. Within the framework of the density functional theory, the crystal structure, physical properties, electronic structure and formation capacity of Mg2FeH6 complex hydride have been investigated. The optimized structural parameters correspond closely with the experimental data from X-ray and neutron powder diffraction measurements. A detailed study of the electronic structures, including the energy band, density of states (DOS) and charge density distribution, reveals the orbital hybridization and bonding characteristics within this hydride. It was shown that Mg2FeH6 is a semiconductor with the energy gap of ca. 2.3347 eV, and that a mixed ionic-covalent bond between Fe and H in FeH6 complexes is embedded in the matrix of Mg2+ cations. The calculated formation enthalpies of Mg2FeH6 , based on the possible synthesis routes, indicate that optimum conditions are achieved if this hydride is fabricated from pure elements, and that the preparation of other compounds would lead to inferior synthesis.

7

Selective removal of Cu(II), Co(II), Zn(II), and Ni(II) with ionizable dibenzo-16-crown-5 and dibenzo-19-crown-6 lariat ethers as ion carriers in polymer inclusion membrane transport

Kozłowski C. A., Walkowiak W.

Ars Separatoria Acta

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2007

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No. 5

19-26

EN

A selective removal of transition metal cations, i.e. Cu(II), Co(II), Zn(II), and Ni(II), with ionizable dibenzo-16-crown-5 and dibenzo-19-crown-6 lariat ethers as ionic carriers in transport across polymer inclusion membrane has been presented. The competitive transport from aqueous nitrate solutions containing metal ions at concentrations of 0.0010 M at pH 4.0 and 7.0 through the cellulose triacetate membrane with 0.5 M lariat ether 1 and 2 (based on a plasticizer) as the ion carrier and o-nitrophenyl pentyl ether (ONPPE) as the plasticizer into 0.5 M hydrochloric solution was performed. For pH = 4.0 and 7.0 of source aqueous phases the selectivity orders were as follows: Cu(II) > Co(II) > Zn(II) > Ni(II), and Cu(II) > Zn(II), Ni(II), Co(II), respectively. The semi-empirical equation was used for calculations of enthalpy formation for complexes of lariat ethers studied with transition metal cations. The two possibilities of metal cation-lariat ether coordination were assumed, i.e. via the crown ether cavity or ionizable carboxylic group. We found that for the both lariat ethers studied at pH 4.0 of source phase the transport rate linearly decreases with the enthalpy of formation increase. This correlation confirms that the observed behavior is connected with the stability of complexes formed by interaction of the lariat ether ring and the transition metal cations studied.