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Wyszukujesz frazę "enthalpy" wg kryterium: Temat


Tytuł:
Thermochemical and Performance Properties of NO2-Substituted Borazines as New Energetic Compounds with High Thermodynamic Stability
Autorzy:
Zamani, M.
Keshavarz, M. H.
Tematy:
electrostatic potential
enthalpy sublimation
enthalpy formation
density
Pokaż więcej
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:
https://bibliotekanauki.pl/articles/951505.pdf  Link otwiera się w nowym oknie
Opis:
The structural isomers of nitroborazines were optimized at M062X/6-311++G** level of theory. The effects of the NO2 group on the molecular volume, molecular surface area, crystal density, positive, negative and total average potentials, variances, average deviation and electrostatic balance parameter on the molecular surface were considered. In addition, some important thermodynamic properties of these compounds, such as gas phase and condensed phase enthalpies of formation (ΔfH° (g) and ΔfH° (c)), and the enthalpy of sublimation (ΔH° sub), were calculated. It was found that the crystal densities (ρ) are in the range 1.4471.902 g/cm3. These values are slightly smaller than the corresponding values of their carbon analogues (except for the mononitro compounds). Meanwhile, the values of ρ for B-substituted, di- and trinitroborazines are larger than the related N-substituted compounds. The calculated values of ΔH° sub are in the range 20.1-30.4 kcal/mol. The calculated values of ΔfH° (g) and ΔfH° (c) for the B-substituted nitroborazines are more negative than those for the N-substituted ones. The stability sequence of the hydrogen bonded network structures of nitroborazines in the condensed phase is: dinitroborazine > mononitroborazine > trinitroborazine. The detonation pressure and velocity of these compounds were also calculated. Nitroborazines can be introduced as energetic compounds with high thermodynamic stability and relatively low detonation performance.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bomb Calorimetric Correlation Study between Chemical Structure and Enthalpy of Formation for a Linear Energetic Polyphosphazene
Autorzy:
Bellamy, A. J.
Contini, A. E.
Golding, P.
Tematy:
PBX technology
energetic polyphosphazenes
bomb calorimetry
enthalpy of combustion
enthalpy of formation
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Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:
https://bibliotekanauki.pl/articles/358199.pdf  Link otwiera się w nowym oknie
Opis:
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic properties of dilute Co-Fe solid solutions studied by 57Fe Mössbauer spectroscopy
Autorzy:
Konieczny, R.
Idczak, R.
Tematy:
Mössbauer spectroscopy
binding energy
short-range order
enthalpy of solution
enthalpy of mixing
binary alloys
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Wydawca:
Instytut Chemii i Techniki Jądrowej
Powiązania:
https://bibliotekanauki.pl/articles/146524.pdf  Link otwiera się w nowym oknie
Opis:
The Co1–xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = –0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Prediction of the Condensed Phase Enthalpy of Formation of Nitroaromatic Compounds Using the Estimated Gas Phase Enthalpies of Formation by the PM3 and B3LYP Methods
Autorzy:
Oftadeh, M.
Keshavarz, M. H.
Khodadadi, R.
Tematy:
condensed phase enthalpy formation
gas phase enthalpy formation
nitroaromatic compounds
PM3
B3LYP
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Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:
https://bibliotekanauki.pl/articles/951504.pdf  Link otwiera się w nowym oknie
Opis:
A new method is introduced to correlate the condensed phase enthalpies of formation of nitroaromatic compounds with their gas phase enthalpies of formation on the basis of the B3LYP/6-31G* and PM3 methods. For the B3LYP method, the condensed phase enthalpy of formation depends on the number of certain elements, nitro groups and aromatic rings. For the PM3 method the number of N=N or N≡N groups, and the presence or absence of three interconnected rings, in addition to some of the parameters mentioned above, are necessary in order to obtain a reliable correlation. For 72 nitroaromatic compounds, the calculated root mean square (rms) deviations of the condensed phase enthalpies of formation of nitroaromatic compounds using the B3LYP and PM3 methods are 63.63 and 32.17 kJ/mol, respectively. The results predicted on the basis of the PM3 method are compared with the best available experimental data.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A study of thermodynamic properties of dilute Fe-Au alloys by the ⁵⁷Fe Mössbauer spectroscopy
Autorzy:
Konieczny, R.
Idczak, R.
Chojcan, J.
Tematy:
Mössbauer spectroscopy
hyperfine parameters
binding energy
short-range order
enthalpy of solution
enthalpy of mixing
binary alloys
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1054974.pdf  Link otwiera się w nowym oknie
Opis:
The room temperature Mössbauer spectra of ⁵⁷Fe were measured for Fe_{1-x}Au_x with the gold concentration ranging from 1 at.% till 4.8 at.%. They were analysed in terms of hyperfine parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of gold atoms existing in the neighbourhood of iron atoms. Basing on the intensities of the spectrum components we determined binding energy E_b between two gold atoms in the studied materials. The latter was done for properly annealed samples using the extended Hrynkiewicz-Królas idea. It was found that the binding energy is positive or Au atoms interact repulsively. The extrapolated value of E_b for x =0 was used for computation of an enthalpy of solution of Au in Fe. Finally the obtained value of the enthalpy was used to predict the mixing enthalpy for the Fe-Au solid solutions. The results were compared with both the corresponding values resulting from the cellular atomic model of alloys by Miedema and those derived from experimental calorimetric data given in the literature.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enthalpy of isopropanol adsorption on zeolite
Autorzy:
Jabłoński, Maciej
Dzienisz, Alicja
Sawicka, Marta
Wróblewska, Elwira
Lubkowski, Krzysztof
Dąbrowska, Grażyna
Piz, Mateusz
Sreńscek-Nazzal, Joanna
Tematy:
Enthalpy
Adsorption
Zeolite
HiSiv 3000
Isopropanol
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Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Powiązania:
https://bibliotekanauki.pl/articles/779858.pdf  Link otwiera się w nowym oknie
Opis:
The enthalpy of isopropanol adsorption on ZSM-5 (Zeolite Socony Mobil Framework Type MFI) was determined by the static adsorption method at the temperature range from 20°C to 100°C. Langmuir and Huttig models of equilibrium adsorption have been used to calculate the enthalpy of isopropanol adsorption at these conditions. Adsorption isotherms determined by the flow method at 20°C and 30°C have been also used in the calculations. The obtained values of isopropanol adsorption enthalpy were compared with the values of isopropanol evaporation enthalpy and with the results obtained from isopropanol and water desorption measurements with thermogravimetry and differential scanning calorimetry methods.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat effects in the reaction of sulfuric acid with ilmenites influenced by initial temperature and acid concentration
Autorzy:
Jabłoński, Maciej
Lubkowski, Krzysztof
Tylutka, Sandra
Ściążko, Andrzej
Tematy:
ilmenites digestion
sulfuric acid
enthalpy of reaction
Pokaż więcej
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Powiązania:
https://bibliotekanauki.pl/articles/1849318.pdf  Link otwiera się w nowym oknie
Opis:
The influence of temperature and sulfuric acid concentration on the enthalpy and the rate of heat release during the reaction of Norwegian and Australian ilmenites with sulfuric acid was determined. The experimental results obtained from calorimetric measurements were compared with theoretical calculations based on the oxide composition and the phase composition of the raw material. Experimentally determined heat of reaction for Norwegian ilmenite (900–940 kJ/kg) and Australian ilmenite (800–840 kJ/kg) showed good agreement with theoretical calculations based on the phase composition of the raw material. It was found that the enthalpy of ilmenites decomposition reaction does not depend on the concentration of sulfuric acid in the concentration range from 83% to 93%. It was also demonstrated that the temperature and concentration of sulfuric acid have a significant impact on the thermokinetics of the decomposition process, increasing the value of the average rate of temperature change.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measurement the Thermal Profile of Steelmaking Ladle with Subsequent Evaluation the Reasons of Lining Damage
Autorzy:
Vlček, J.
Jančar, D.
Burda, J.
Klárová, M.
Velička, M.
Machovčák, P.
Tematy:
ladle
refractory lining
temperature
enthalpy
ladle lifetime
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/354815.pdf  Link otwiera się w nowym oknie
Opis:
Based on the operational measurement, of which content was to determine ladle thermal profile, there were analysed causes of possible damage of lining in steel ladles by steel breakout through the ladle shell. There exists connection between thermal state of ladle lining during the operation and its lifetime. There were reached to the conclusion that the cause of failure in the lining of ladle is except for high temperature of bath, also wide interval of temperature change during the tap operation, in consequence with possible insufficient pre-heating of ladle, discontinuous operation of aggregate and damage of insulating lining layer, respectively deformation of ladles shell.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of endwall flows and losses in axial turbines. Part I. Formation of endwall flows and losses
Badanie przepływów i strat brzegowych w turbinach osiowych. Część I. Formowanie się przepływów w strefie brzegowej i strat brzegowych
Autorzy:
Lampart, P.
Tematy:
axial turbine
endwall flow
secondary flow
enthalpy loss
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Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/281714.pdf  Link otwiera się w nowym oknie
Opis:
Endwall flows are among the most important sources of loss in turbines. The process of formation of endwall flows and evolution of vorticity from the endwall boundary layers is briefly described in the paper. The resulting endwall losses are discussed. The endwall boundary layer losses are evaluated theoretically by integrating the entropy increase in the boundary layer and assuming a certain model of blade profile load. The endwall losses are also calculated with the help of CFD in a 3D straight turbine cascade of Durham and compared with the results of available experimental data of ERCOFTAC.
Przepływy brzegowe stanowią jedno z głównych źródeł strat w turbinach. W pracy w skrócie wyjaśniono proces formowania się przepływów brzegowych i ewolucję wirowości pochodzącej z brzegowych warstw przyściennych. Przedyskutowano wynikające stąd straty przepływu. Wyznaczono teoretycznie straty przepływu w brzegowej warstwie przyściennej poprzez całkowanie przyrostu entropii wzdłuż warstwy brzegowej i zakładając pewien model obciążenia profilu łopatkowego. Z pomocą programów komputerowych numerycznej mechaniki płynów wyznaczono także przepływ i straty brzegowe w prostej palisadzie turbinowej Durham i porównano otrzymane rezultaty z danymi eksperymentalnymi ERCOFTAC.
Dostawca treści:
Biblioteka Nauki
Artykuł

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