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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The suitability of PVD films of γ-Al2O3 and of ternary Al-O-N as diffusion barriers between a nickel based superalloy CMSX-4 and NiCoCrAlY for a possible application in gas turbines was investigated. Therefore, an Al2O3 film and, alternatively, an Al-O-N film were deposited on CMSX-4 at 100 °C substrate temperature by means of reactive magnetron sputtering ion plating (MSIP). After characterization of composition and structure of the films by X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (XRD), a NiCoCrAlY coating was deposited onto the diffusion barriers and, for comparison, directly onto CMSX-4 by MSIP as well. The composites were annealed for 4 h at 1100 °C under inert atmosphere. Wavelength dispersive X-ray (WDX) element mappings and line-scans of the cross-sectional cut served to evaluate the suitability of the films as diffusion barriers. After detachment of the coatings from the substrate, the phase stabilities of the two metastable phases γ-Al2O3 and Al-O-N were determined by means of grazing incidence XRD. Without a diffusion barrier, enhanced interdiffusion was observed. Analyses of the composite with the γ-Al2O3 interlayer revealed diffusion of Ti and Ta from the substrate into the NiCoCrAlY coating. No interdiffusion of Ni, Ti, Ta, and Cr could be detected in case of the ternary Al-O-N film. Whereas the ternary Al-O-N film remained in the as-deposited X-ray amorphous structure after annealing, a phase change from the γ to the α modification could be observed in case of the Al2O3 film, presumably responsible for its lower efficiency as a diffusion barrier.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A reactive ionized cluster beam technique (RICB) which was composed of a conventional ICB source and a radical beam source has been used to deposit stable and metastable polycrystalline AlNx (0≤x≤1) films. Using in-situ high energy electron diffraction (HEED) at grazing incidence geometry, crystallographic properties such as structure, preferred orientation and interplanar dspacing values were determined and the relation to deposition parameters investigated. It could be shown that the simultaneous use of the ICB technique and a radical beam source to separately control the kinetic energy of the Al ions and the dissociation rate of molecular nitrogen, allows AlN films to be deposited with variable composition and crystal structures. In-situ HEED used in the transmission mode is an effective tool to investigate the crystallography of growing compound films such as AlNx.
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The kinetics of the reduction of nitric oxide with pure and potassium-doped carbon, NO+C=1/2 N2+CO, were investigated. For the reaction of NO with pure carbon, measurements were made in the temperature range from 1750 K to 2130 K and at initial NO pressures between 5×10−3 Pa and 7×10−2 Pa. The reaction was first order with respect to nitric oxide at NO pressures below 3×10−2 Pa. The activation energy was 54 kJ/mol for temperatures below 2000 K, while at higher temperatures a second (parallel) reaction became noticeable with a definitely higher activation energy. Potassium-doped carbon was prepared by a molecular beam technique. AES studies verified that potassium was intercalated into the graphite surface and that the potassium-to-carbon ratio changed continuously with sample temperature. The reduction of NO with K-doped carbon was investigated in the temperature range from 710 K to 1080 K and at initial NO pressures between 7×10−5 Pa and 6×10−4 Pa while monitoring, in-situ using AES the K/C-ratio of the surface. The NO reduction rate rose linearly with K/C. Compared to pure carbon, the reaction rate for the NO reduction with K-doped carbon increased by a factor in the range of 104. The activation energy for the NO reduction with K-doped carbon was found to be 82 kJ/mol.
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  • 4
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Activity coefficients of nickel and cobalt sulfate have been determined from solubility measurements in the systems NiSO4 · H2O resp. CoSO4 · H2O — (NH4)2SO4 — H2O at 160-300°C by applying the DEBYE-Hückel theory. The logarithmic expression obtained (see “Inhaltsübersicht”) holds for pure solutions and those containing ammonium sulfate at ionic strengths 0 ≤ I ≤ 4 at temperatures ranging from 25 to 300°C.For temperatures between 160 and 300°C, equilibrium constants and standard enthalpies and entropies of solution, ΔH°(T) and ΔS°(T), are given for the equilibria investigated. The thermodynamic data for 25°C (see „Inhaltsübersicht“) have been calculated by extrapolation.The standard entropies of the monohydrates have been found to be S2980 (NiSO4 · H2O) = 33 and S2980 (CoSO4 · H2O) = 43 cal/mole·degree.
    Notes: Aus Löslichkeitsmessungen an den Systemen NiSO4 · H2O bzw. CoSO4 · H2O — (NH4)2 SO4 — H2O im Temperaturbereich von 160-300°C werden die Aktivitätskoeffizienten von Nickel- und Kobaltsulfat mit Hilfe der Debye-Hückelschen Theorie zu \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm lg}\;\gamma _{{\rm NiSO}_{\rm 4} } = {\rm lg}\;\gamma _{{\rm CoSO}_{\rm 4} } = - 4{\rm A}\frac{{\sqrt {\rm I} }}{{{\rm 1 + 1,25}\sqrt {\rm I} }} - 0,041 \cdot {\rm I} $$\end{document} bestimmt. Diese Beziehung ist für reine und Ammoniumsulfat enthaltende Lösungen bei Ionenstärken 0 ≤ I ≤ 4 im Temperaturbereich von 25-300°C gültig. Für 25°C liefert sie Aktivitätskoeffizienten, die mit Angaben der Literatur für Nickelsulfat gut übereinstimmen.Für die untersuchten Gleichgewichte MeSO4 · H2O = Me++ + SO4- + H2O (Me = Ni, Co) werden die Gleichgewichtskonstanten und die Standardlösungsenthalpien ΔH°(T) und -entropien ΔS°(T) zwischen 160 und 300°C angegeben. Durch Extrapolation auf 25°C werden folgende thermodynamische Werte berechnet: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm NiSO}_{\rm 4} \cdot {\rm H}_{\rm 2} {\rm O} = {\rm Ni}^{{\rm + + }} + {\rm SO}_{\rm 4}^{ - - } + {\rm H}_{\rm 2} {\rm O,}} \hfill \\ {\Delta {\rm H}_{{\rm 298}}^{\rm 0} = - 12{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm Mol}}}} \right. \kern-\nulldelimiterspace} {{\rm Mol}}},\;\Delta {\rm S}_{{\rm 298}}^{\rm 0} = - 42{{{\rm cal}} \mathord{\left/ {\vphantom {{{\rm cal}} {{\rm grad\;Mol}}}} \right. \kern-\nulldelimiterspace} {{\rm grad\;Mol}}}.} \hfill \\ {{\rm CoSO}_{\rm 4} \cdot {\rm H}_{\rm 2} {\rm O} = {\rm Co}^{{\rm + + }} + {\rm SO}_{\rm 4}^{ - - } + {\rm H}_{\rm 2} {\rm O,}} \hfill \\ {\Delta {\rm H}_{{\rm 298}}^{\rm 0} = - 13{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm Mol}}}} \right. \kern-\nulldelimiterspace} {{\rm Mol}}},\;\Delta {\rm S}_{{\rm 298}}^{\rm 0} = - 48{{{\rm cal}} \mathord{\left/ {\vphantom {{{\rm cal}} {{\rm gradMol}}}} \right. \kern-\nulldelimiterspace} {{\rm grad\;Mol}}}} \hfill \\\end{array} $$\end{document}.Die Normalentropien der Monohydrate ergeben sich zu \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm S}_{{\rm 298}}^{\rm 0} \left({{\rm NiSO}_{\rm 4} \cdot {\rm H}_{\rm 2} {\rm O}} \right) = 33{\rm \;und\;S}_{{\rm 298}}^{\rm 0} \left({{\rm CoSO}_{\rm 4} \cdot {\rm H}_{\rm 2} {\rm O}} \right) = 43\;{{{\rm cal}} \mathord{\left/ {\vphantom {{{\rm cal}} {{\rm gradMol}}}} \right. \kern-\nulldelimiterspace} {{\rm grad\;Mol}}} $$\end{document}.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 43 (1971), S. 112-116 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Es wurde die Löslichkeit von Kohlenmonoxid und Wasserstoff in Wasser bei Temperaturen bis 300°C und Gesamtdrücken bis 100 atm, entsprechend Molenbrüchen des gelösten Gases bis etwa x1 = 1,2 · 10-3, bestimmt. Die oberhalb 250°C merklich einsetzende Reaktion zwischen gelöstem CO und Wasser wurde bei der Ermittlung des Lösungsgleichgewichts berücksichtigt. Bei Gasgehalten x1 ≤ 4 · 10-4 ließen sich die Löslichkeitsisothermen durch Geraden annähern, deren Steigungen als Löslichkeitskonstanten angegeben wurden. Bei höheren Konzentrationen zeigten die Isothermen eine deutliche, mit steigender Temperatur stärker ausgeprägte Krümmung. Die Anwendbarkeit des Henryschen Gesetzes als praktische Näherungsformel ist also zumindest bei höheren Temperaturen auf kleine Gasgehalte beschränkt.
    Additional Material: 9 Ill.
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