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  • 1
    Electronic Resource
    Electronic Resource
    The growth and structure of oxide films formed on single crystal (100) and polycrystalline Cr between 550 and 900 °CDedicated to Professor Dr. Alfred Rahmel on the occasion of his 60th birthday (1987)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 38 (1987), S. 575-583 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Wachstum und Gefüge von Oxidschichten auf einkristallinem (100) und polykristallinem Chrom zwischen 550 und 900 °CDie Oxidation von polykristallinem und (100)-Cr bei Temperaturen zwischen 550 und 900°C und Sauerstoffbrücken zwischen 5 × 10-3 und 5 × 10-1 torr (bei Verwendung von Oberflächenvorbehandlungen, welche die ausschließliche Bildung von festhaftendem einheitlichem, porenfreiem polykristallinem α-Cr2O3 gewährleisten) folgt langzeitig einem parabolischen Zeitgesetz mit einer Aktivierungsenergie von etwa 51 kcal mol-1. Die durch aufeinanderfolgende Oxidation in 18O2 und 16O2 erzeugten Oxidschichten konnten mittels polyatomarer SIMS analysiert werden, so daß das Ausmaß des Sauerstofftransports in den wachsenden Oxidschichten und der Wachstumsmechanismus geklärt werden konnten. Die Ergebnisse zeigten, daß der dominierende Wachstumsmechanismus der Kationentransport nach außen ist und nur ein kleiner, jedoch nicht zu vernachlässigender Transport an Sauerstoff entlang der Oxidkorngrenzen nach innen erfolgt. Etwa 1% des Oxids entsteht innerhalb der Zunderschicht durch diese Diffusion nach innen. Die Diffusionskoeffizienten von Sauerstoff waren um mehrere Größenordnungen höher als die Selbstdiffusionskoeffizienten des Sauerstoffs in Cr2O3, doch waren sie immer noch weitaus zu niedrig, um die beobachteten Oxidationsgeschwindigkeiten erklären zu können.
    Notes: The oxidation of polycrystalline and (100) Cr at temperatures from 550-900°C and 5 × 10-3 to 5 × 10-1 torr oxygen pressure, choosing surface pretreatments such that only adherent, uniform, pore-free polycrystalline α-Cr2O3 is produced, show long term parabolic growth kinetics with an activation energy ∽ 51 kcal mol-1. Oxide layers, produced by sequential oxidation in 18O2 and 16O2, were suitable for the application of polyatomic SIMS to elucidate the extent of oxygen transport in the growing oxides and the mechanism for their growth. The data show that the predominant growth mechanism is by outward cation transport, with a small yet significant amount of inward oxygen diffusion down oxide grain boundaries. ∽ 1% of the oxide is created within the film as a result of this inward diffusion. Oxygen diffusion coefficients were found to be orders of magnitude higher than oxygen self diffusion coefficients in Cr2O3 but much too low to account for the observed oxidation rates.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19870381005
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of Y and Zr on the Oxidation of NiAl (1996)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 47 (1996), S. 631-632 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Der Einfluß von Y und Zr auf die Oxidation von NiAl
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19960471107
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  • 3
    Electronic Resource
    Electronic Resource
    A combined approach: Isotopic exposure/SIMS analysis/SEM to Study the Early Stages of oxidation of β-NiAl at 1473 KDedicated to Professor Dr. H. J. Grabke on the occasion of his 60th birthday (1995)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 46 (1995), S. 297-305 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Ein gemeinsamer Ansatz: Isotopische Exposition/SIMS-Analyse/REM zur Untersuchung des Anfangsstadiums der Oxidation von β-NiAL bei 1473 KDas Anfangsstadium der Oxidation von β-NiAl wurde bei 1473 K an unmodifiziertem Material und nach Y-Implantation untersucht. Hierzu wurde die 16O/18O-Zwei-Stufen-Oxidation in Kombination mit hochauflösender Sekundärionenmassenspektrometrie (SIMS) sowie Rasterelektronenmikroskopie (REM) eingesetzt. Es zeigt sich, daß die gebildeten Oxidschichten hinsichtlich der Zusammensetzung und des Gefüges nicht homogen sind. Deswegen war es erforderlich, analytische Methoden (SIMS und REM) mit sehr hoher Ortsauflösung bei höchstmöglicher Empfindlichkeit zu verwenden. Dadurch konnten die unterschiedlichen Wachstumsmechanismen in den einzelnen Bereichen der Oxidschicht auf den beiden verschiedenen Substrattypen identifiziert werden.
    Notes: The early oxidation stages of unmodified and yttrium-implanted β-NiAl have been studied at 1473 K using sequential isotopic exposure (so-called two-stage oxidation) combined with low and high resolution SIMS analysis and SEM characterization.The scales growing on unmodified material comprised typically a cracked morphology with oxide ridges growing outward from the cracks. Some ridges were formed at the reaction temperature during the first oxidation stage and continued growing during the second stage. This resulted in a network of ridges on the outer surface of the scale.Two regions: non-cracked areas and cracked round patches were observed in the scale on yttrium-implanted β-NiAl. No ridges but thin lace-like oxide was formed in cracks and round particles extruded from some crack centres. No network was formed by the lace-like oxide. Inward oxygen transport contributed significantly to the overall matter transport in the patches, while its contribution in the remaining scale was much less pronounced. The very thin outermost layer of most patches was enriched in Cr, which was present at a level of ca. 90 ppm only in the starting material. This finding is discussed in terms of the effect of Cr on the phase transformation of unstable aluminas into the stable β-Al2O3.The results showed that the scales were inhomogeneous regarding both composition and microstructure. Therefore, only analytical methods having respectable sensitivity and resolution might be used to give reliable information regarding the growth mechanisms of scales. This applies to SIMS as well as to the electron microscopy methods.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19950460505
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  • 4
    Electronic Resource
    Electronic Resource
    Segregation studies of oxidized Y and Zr doped NiAlDedicated to Professor Dr. H. J. Grabke on the occasion of his 60th birthday (1995)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 46 (1995), S. 218-222 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Untersuchungen zur Segregation von Y und Zr bei der Oxidation von NiAlKonventionelle, analytische und hochauflösende Transmissionselektronenmikroskopie (TEM) sowie hochauflösende Sekundärionenmassenspektrometrie (SIMS) wurden benutzt, um den Effekt von reaktiven Elementen auf die Oxidation von NiAl zu untersuchen. Polykristalline NiAl-Proben, dotiert mit 0,1 Mas.-% Y oder 0,2 Mas.-% Zr, wurden bei einer Temperatur von 1200°C oxidiert. 18O Tracer-Experimente in Verbindung mit hochauflösenden SIMS-Untersuchungen deuten darauf hin, daß reaktive Elemente die nach außen gerichtete Diffusion von Kationen reduzieren. Energiedispersive Röntgenspektroskopie mit einem dedizierten STEM zeigte, daß die reaktiven Elemente an den Korngrenzen in der Oxidschicht und an der Metall/Oxid-Grenzfläche segregieren. Der Anteil von Y bzw. Zr an den Korngrenzen in der Oxidschicht beträgt 0,2 Monolagen. Demgegenüber wurden an der Metall/Oxid-Grenzfläche 0,15 Monolagen (Zr-dotiert) bzw. 0,07 Monolagen (Y-dotiert) gefunden. In Y-reichen Teilchen im NiAl nahe der Metall/Oxid-Grenzfläche konnte Schwefel nachgewiesen werden.
    Notes: Conventional electron microscopy, analytical electron microscopy, high resolution electron microscopy and high resolution SIMS have been used to investigate the effect of the reactive elements, Yand Zr, on the oxide scale formation on NiAl. Polycrystalline NiAl samples, doped with either 0. 1 wt% Yor 0.2 wt% Zr, were oxidized in air at 1200°C. 18O tracer experiments in conjunction with high resolution SIMS suggest that the reactive elements reduce the outward diffusion of cations. Energy dispersive X-ray spectroscopy on a dedicated STEM showed that the reactive elements segregate to the grain boundaries in the oxide scale and to the metal/oxide interface. The amount at the oxide scale grain boundaries was calculated to be 0.2 monolayers for both Zr and Y doped NiAl. The amounts of segregation were calculated to be 0.15 monolayers (Zr-doped) and 0.07 monolayers (Y-doped) at the metal/oxide interface. The presence of sulfur was detected in Y-rich particles in the NiAl close to the interface.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19950460405
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  • 5
    Electronic Resource
    Electronic Resource
    Sputter reduction of oxides by ion bombardment during Auger depth profile analysis (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 487-497 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Quantification of the magnitude of preferential sputtering of oxygen from metallic oxides has been examined for a large number of 30 nm thick amorphous oxides deposited onto polished silicon substrates. The method of analysis was derivative-mode Auger analysis carried out in a cleaner vacuum system and with cleaner initial surfaces than has been the case usually for data found in the literature. Ion sputtering was primarily with 3 keV xenon ions but the effect of ion energy (1, 3 and 4.5 keV), ion mass (argon or xenon) and sputter rate was also examined. The magnitude of preferential sputtering at 20°C was generally much less than has been reported previously and was not a function of ion energy, mass or sputter rate over the range studied. The results separate into two groups: oxides that reduce appreciably and those that do not. The results agree well with the predictions from the theoretical model of Kelly.1 It must be concluded from the work that most of the data reported in literature are primarily the result of unrecognized and therefore unreported variables. Likely candidates are contaminants within the ion beam and background environment that contribute chemical effects to the sputter process, ion beam and electron beam heating of poorly conducting samples, or redeposition of sputtered material into the analysis area.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740150808
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of Auger and SIMS analysis of a thin passive oxide film on iron - 25% chromium (1987)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 10 (1987), S. 259-261 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A comparison of three surface-analytical methods, viz: variable escape angle Auger electron spectroscopy, Auger sputter profiling and SIMS sputter profiling, is presented for a 1.8 nm-thick ‘passive’ oxide film on Fe-25% Cr alloy. The three techniques give identical results regarding the composition of the film as a function of depth. This means that with the proper choice of sputtering conditions (heavy ions of low energy), sputter mixing and sputter reduction are not a problem. It is evident from the experimental data that SIMS sputter profiling has the best depth resolution of the three techniques for such a thin film.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740100507
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