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  • 1
    Digitale Medien
    Digitale Medien
    Comment on "Thermochemistry of gaseous SiO(OH), SiO(OH)2, and SiO2,"[J. Chem. Phys. 101, 6076 (1994)] (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6535-6535 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Previously published data for a gaseous reaction equilibrium involving the species SiO(OH) have been re-interpreted, based on other information suggesting a very weak OSi–OH bond. This reinterpretation leads to a revised value of −85 kcal mol−1 for the standard enthalpy of formation at 298 K of gaseous SiO(OH). © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.476500
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  • 2
    Digitale Medien
    Digitale Medien
    Thermochemistry of gaseous ZrF, ZrF2, and ZrF3 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6349-6352 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Several gaseous reaction equilibria involving the lower-valent Zr–F species were studied by mass spectrometry over parts of the range 1400 – 2400 K, and the derived reaction thermodynamics were used to evaluate the bond dissociation energies, BDE, and standard enthalpies of formation, ΔfH°298, of the gaseous species ZrF, ZrF2, and ZrF3. Emphasis was placed on correlation of the second and third law results as an aid in selecting the proper thermal functions. BDE values at 298 K, measured by reference to the molecule BaF, were found to beD(Zr–F)=149.9±2.5;D(FZr–F)=161.2±2.5;D(F2Zr–F=149.6±4.5; and D(F3Zr–F)=157.9±2.5 kcal mol−1. Corresponding values of ΔfH°298 for the gaseous species were calculated to be ZrF,12.3±2.8;ZrF2,−129.9±3.7 andZrF3,−260.5±2.8 kcal mol-1. The results are discussed in terms of other information in the literature. When all results are evaluated with consistent thermal functions and auxiliary data, there is reasonable agreement among derived thermochemical values.alues.© 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475146
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  • 3
    Digitale Medien
    Digitale Medien
    Thermochemistry of ZnCl(g) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 1337-1338 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The gaseous species Zn, ZnCl, and ZnCl2 were generated in an effusion cell by reaction of Cl2(g) with ZnO(s) near 1400 K, and were identified and monitored by mass spectrometry. Equilibrium constants were evaluated for the gaseous reaction Zn+ZnCl2=2ZnCl from ion intensities measured over the range 1336–1436 K and used to derive the third law enthalpy change ΔH298°=176±8 kJ mol−1 and the dissociation energy D0°(ZnCl)=229±8 kJ mol−1. This result is in good agreement with an earlier value derived from equilibrium measurements made by monitoring the electronic spectrum of ZnCl(g) in equilibrium with gaseous Zn and ZnCl2. The results are useful in estimating the thermochemical properties of gaseous ZnOH and Zn(OH)2 for chemical modeling applications. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.479319
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  • 4
    Digitale Medien
    Digitale Medien
    Thermochemistry of gaseous SiO(OH), SiO(OH)2, and SiO2 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6076-6079 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The gaseous species SiO(OH) and SiO(OH)2 were detected as products of the reaction of SiO2(l) and H2O(g) near 2000 K, using effusion-beam mass spectrometry. No other silicon-containing hydroxides or oxyhydroxides were observed. From third law analysis of equilibrium data, values of ΔfH°298 of SiO(OH) and SiO(OH)2 were evaluated as −118 and −213 kcal mol−1, respectively, both ±4 kcal mol−1. Several equilibrium measurements on gaseous SiO2 yielded a ΔfH°298 value of −67 kcal mol−1, which is 6–10 kcal mol−1 less stable than values given in most compilations. It appears that the new thermochemical data for SiO(OH) and SiO(OH)2, plus a literature estimate for Si2O(OH)6, can be used to model the equilibrium behavior of the silica–steam system over a wide range of temperatures and pressures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467322
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  • 5
    Digitale Medien
    Digitale Medien
    Thermochemical properties of gaseous POBr and some H–P–O species (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8373-8376 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Effusion cell beams containing the gaseous species HPO, HPO2, HPO3, and POBr along with other products were generated by the reaction of H2O(g) or Br2(g) with Ca2P2O7(s). The species were identified by mass spectrometry, and were characterized thermochemically from the study of several reaction equilibria. Reaction enthalpies and standard enthalpies of formation were derived from third law analysis of the equilibrium data, yielding the ΔfH°298 values HPO, −34.2; HPO2, −110.6; HPO3, −168.8; and POBr, −53.5, all in kcal mol−1. Our new result for POBr is in serious disagreement with a value reported in the literature; there are no previous reports on the other species studied here. A preliminary ΔfH°298 value of −60.2 kcal mol−1 was also obtained for POCl(g), this time in reasonable accord with a literature value. The new thermochemical data yield calculated compositions in agreement with measured values for some lamp gas mixtures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466782
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  • 6
    Digitale Medien
    Digitale Medien
    Thermochemical properties of the gaseous scandium, yttrium, and lanthanum fluorides (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3769-3775 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Equilibria involving the gaseous mono- and difluorides of Sc, Y, and La were studied by effusion-beam mass spectrometry, and reaction enthalpies were derived by second and third law methods. In addition, the sublimation pressures of the crystalline trifluorides ScF3, YF3, and LaF3 and related thermodynamics of the gaseous trifluorides were determined by the torsion-effusion method. Dissociation energies at 298 K in kcal mol−1 for the bonds M–F, FM–F, and F2M–F, respectively, were derived as follows: For Sc, 143.2±3.2, 148.8±4.1, and 155.7±6.4; for Y, 163.8±3.2, 145.6±3.2, and 151.6±4.7; and for La, 157.5±4.1, 153.2±3.2, and 149.2±5.4. These values do not fall into any obvious pattern. The dissociation energies of ScF and YF are in good agreement with the results of high-level theoretical calculations. Spectroscopic and molecular constants of the species are summarized, and the thermochemical results are compared with values in the literature. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.468558
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  • 7
    Digitale Medien
    Digitale Medien
    Thermochemistry of gaseous manganese oxides and hydroxides (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8377-8380 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The reactive vaporization of MnO(c) in the presence of O2 and H2O/D2O has been studied by effusion-beam mass spectrometry, and the new species MnO2, MnOH, Mn(OH)2, and MnO(OH) have been identified. The identities of the hydroxides were confirmed from deuterium isotopic substitution. Reaction enthalpies and standard enthalpies of formation have been derived from equilibrium measurements, yielding the ΔfH°298 values for the gaseous species MnO2, −17.6; MnOH, 0.1; Mn(OH)2, −95.9; and MnO(OH), −41.1, all in kcal mol−1. For use in the analysis, thermal functions were calculated from known or estimated molecular constants. Bond energies derived from the results fall in a logical and consistent sequence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466783
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  • 8
    Digitale Medien
    Digitale Medien
    A new analytical technique of photoluminescence for optimization of organometallic chemical vapor deposition (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3781-3784 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An analytical method for quantitative interpretation of GaAs photoluminescence spectra was developed. Because of various transition mechanisms the photoluminescence spectrum of a sample may vary significantly under different measurement conditions. Based on a proposed scheme of transition priorities, spectra taken at various excitation powers were analyzed. Comparing results of undoped GaAs epitaxial layers grown by organometallic chemical vapor deposition under similar conditions but different V/III ratios, an optimum ratio corresponding to a minimum number of shallow impurities was clearly identified. Carbon and zinc were found to be the major shallow acceptors in most samples. At very low V/III ratios, carbon was the most dominant acceptor. The carbon concentration diminishes with an increasing ratio and the amount of zinc becomes more significant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337543
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  • 9
    Digitale Medien
    Digitale Medien
    Intrinsic stress, island coalescence, and surface roughness during the growth of polycrystalline films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5097-5103 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: During film growth by a variety of techniques, intrinsic tensile stresses can be created by the coalescence of neighboring islands. Experimental results with diamond films produced by chemical vapor deposition are compared with a relatively simple model to demonstrate that a realistic interpretation of these coalescence stresses must account for effects that are associated with surface roughness. First, the interpretation of curvature measurements during the early stages of film growth must account for this surface roughness. Also, the experiments show that tensile stresses are induced by grain boundary formation during continuing growth after the initial island coalescence event. This understanding differs from the traditional interpretation that continuing intrinsic stress is produced by "templated" growth onto an already strained crystalline lattice. A kinetic model of stress evolution during postcoalescence growth is also presented. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1412577
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  • 10
    Digitale Medien
    Digitale Medien
    Lateral oxidation kinetics of AlAsSb and related alloys lattice matched to InP (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2458-2464 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The lateral oxidation kinetics of AlAs0.56Sb0.44 on InP substrates have been investigated to understand the antimony segregation process during oxidation. Oxidation layers were grown between GaAsSb buffer and cap layers on InP substrates by molecular beam epitaxy. Oxidation temperatures between 325 and 500 °C were investigated for AlAsSb layer thicknesses between 100 and 2000 Å. At low oxidation temperatures (Tox≤400 °C), the process is reaction limited with a linear dependence of oxidation depth on time. At intermediate oxidation temperatures (400〈Tox〈450 °C), the oxidation process becomes diffusion limited. At high oxidation temperatures, the oxidation process is termed self-limiting since at 500 °C the process stops entirely after oxidation times on the order of 5 min and distances of 40 μm. It is shown that the antimony float layer lags the oxidation front by a temperature-dependent distance, which suggests that the antimony may change the structure of the oxide at the front and cause self-limiting behavior. The oxidation kinetics of AlxGa1−xAsSb and AlxIn1−xAsSb have also been investigated. Antimony segregation is not suppressed during oxidation of Ga-containing layers and AlInAsSb quaternary alloys do not oxidize laterally at measurable rates in the range 400–525 °C. SiNx cap layers deposited after growth and before oxidation do not affect the Sb segregation or oxidation rate, but do smooth the cap surface by preventing uneven Sb metal segregation to the cap/oxide interface. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1335825
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