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  • 1
    Electronic Resource
    Electronic Resource
    The Role of Copper in Resisting Metal Dusting of Ni-Base Alloys (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 522-523 (Aug. 2006), p. 581-588 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present study focuses on a new technique for the prevention of metal dusting in carbonaceousgas environments at intermediate temperature. Preliminary laboratory metal dusting test wasconducted for Ni-x%Cu binary alloys and Ni-Cr alloys with various Si and Cu content in a simulated60%CO-26%H2 -11.5%CO2-2.5%H2O (in vol.%) gas mixture at 650°C. Specimens of the binaryalloys containing low Cu were entirely covered with coke and showed rough metal surfaces due tothe degradation of metal. Alloys of 20% and more Cu, on the contrary, had no coke deposition andsmooth metal surfaces, suggesting alloys with an adequate Cu do not react with CO in the syngasmixture without an oxide scale barrier. Based on these results, we conclude that Cu does not protectby formation of the oxide scale but has a “Surfactant-Mediated Suppression” against metal dusting.This effect can be explained in terms of atomistic interaction of CO with transition-metal surfaces byelectronic structure analyses. For the Ni-Cr alloy, both addition of Si and Cu played a role ofpreventing pit formation in the simulated syngas atmosphere. The concept can be also useful for thepractical material design of Ni-Cr-Si-Cu alloy with excellent metal dusting resistance
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.522-523.581.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Metal Dusting Behaviour of Alloy800H in Laboratory Carbonaceous Environments under High Pressure (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 595-598 (Sept. 2008), p. 649-660 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Metal dusting behaviour of alloy800H was investigated in a laboratory-pressurized reactorwhere CO-H2-CO2-H2O gas mixtures flowed continuously, simulating the gas environments inactual syngas production plant. Four test conditions, having a variety of gas pressures and H2Ocontents, were conducted for a long rod specimen that was imposed thermal gradient of 777°C to454°C in a longitudinal direction. After an exposure of 100h at high pressure, metal dusting hasinitiated with a bell-shape distribution on the test specimens at temperatures between 600°C and700°C. Gas pressure has accelerated metal dusting even if the gas atmospheres had the same gascomposition. On the contrary, metal dusting has been alleviated with increasing the H2O content inthe test gas. Oxide scale characterisations were analyzed by using Raman spectroscopy and XPS atthe test specimen surfaces exposed at different temperature. The ratio of a protective Cr2O3 scale tospinel oxides such as FeCr2O4 and MnCr2O4 has increased with increasing the exposure temperature,with reducing the gas pressure, and with lowering the H2O content. These behaviours have beeninterpreted from thermodynamic indices: carbon activity ac and the oxide scale integrity related tooxygen potential Po2 as a function of temperature
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.595-598.649.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Deformation and Fracture Behavior of Surface Oxide Scale on Fe-13Cr Alloy in Hot-Rolling Process (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 522-523 (Aug. 2006), p. 461-468 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The behavior of the surface oxide scale on steel products during hot rolling processinfluences the surface properties of final products. To investigate the deformation and the fracturebehavior of surface oxide scale of Fe-13Cr alloy, a hot rolling test was carried out. The oxide scalerolled out was observed in detail by using TEM. The specimen was hot-rolled after oxidation at1100[removed info] for 90 minutes in air. The hot rolling tests with two conditions ([removed info]. The hot rolling test ofthe outer scale {=whole layer scale} , [removed info]. The hot rolling test of the inner scale that removed theouter scale) were carried out. The rolling reduction rate was 25, 44, 58, and 68%. The outer scalewas composed of Fe2O3 and F3O4, and the inner scale was composed of Fe3O4, FeCr2O4, and a smallamount of Fe2SiO4. Fe2SiO4 formed along the grain boundaries of the other oxides (Fe3O4, FeCr2O4)was observed by TEM. In the test [removed info], Fe2O3 of the outer scale was pulverized to fine particle thatlooks like red powder, and Fe3O4 of the outer scale was cracked by hot rolling. A ductility-likebehavior was observed in the inner scale (Test [removed info]). That is, it was found by the SEM observationthat porosity and micro cracks of the surface oxide disappeared gradually according to the increasein the rolling reduction. It was thought that the porosity and the micro cracks eased the compressionstress caused by hot rolling. In the case of high reduction rate, FeSi2O4 ,which is a low melting pointoxide, formed on grain boundary caused grain boundary slipping. When the rolling reduction is veryhigh, plastic deformation by dislocation occurred in Fe3O4 and FeCr2O4. However, these oxideswere broken, when their plasticity would not be able to accept considerably high rolling reduction
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.522-523.461.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    In Situ Growth-Stress Measurement of Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 Scale Formed on Stainless Steels by Raman Spectroscopy (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 522-523 (Aug. 2006), p. 489-496 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Raman spectroscopy was conducted to evaluate mechanical stress in growing α-Cr2O3scale upon oxidation of austenitic 25mass%Cr-20mass%Ni and ferritic 17mass%Cr stainless steels at1173 K in air for up to 24 h. Sintered α-Cr2O3 pellet was heated to 373-1173 K and examined in orderto obtain the temperature dependence of the wave length of the major Raman peak. For 1.2 mm thick25mass%Cr-20mass%Ni steel specimen, compressive growth stress was indicated for α-Cr2O3 scaleright upon oxidation and the stress increased until oxidation for 3 h, but it saturated and remainedconstant thereafter. The growth stress of α-Cr2O3 scale was 0.7 ± 0.1 GPa at 1173 K. For 1.2 mmthick ferritic 17mass%Cr steel specimen, mechanical stress was compressive, but the saturatedgrowth stress was around 0.2 GPa, considerably smaller than the “strong” 25mass%Cr-20mass%Nisteel specimen. For 0.1mm thick austenitic 25mass%Cr-20mass%Ni steel specimen, the test resultswere similar. These were attributed to the different high-temperature strength of the metal substrate.Hence, for high-temperature oxidation of thin foils and/or ferritic steels of which high-temperaturestrength of the metal substrate is relatively poor, stress relaxation of protective α-Cr2O3 scale canresult and the growth stress of α-Cr2O3 scale may be lowered by the “weak” metal substrate. Ramanspectroscopy can offer useful information on the mechanical stress of protective oxide scale even athigh temperatures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.522-523.489.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Optical and structural characterizations of ZnSe/ZnSSe superlattices grown by metalorganic chemical vapor deposition (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3029-3033 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnSe/ZnSSe superlattices (SLs) grown on GaAs substrates were studied with transmission electron microscopy and x-ray diffraction. Defects were observed in the initial growth stage, but they were recovered with the growth of short-period SL. The temperature dependent decrease of photoluminescence (PL) intensities improved in the short-period SL. Clear excitonic absorption peaks were observed in photocurrent spectra and the blue shift of the absorption peaks by the quantum confinement was in reasonable agreement with the calculated peak shift. In a SL with the well width of 93 A(ring), a biexciton PL peak was observed from the very low excitation power of less than 1 mW/cm2. Details of the biexciton properties are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351512
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  • 6
    Electronic Resource
    Electronic Resource
    Vacancy ordering of Ga2Se3 films by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 567-569 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ga2Se3 films have been grown by molecular beam epitaxy. Single-crystal Ga2Se3 films were obtained for the first time on (001) GaP substrates at a substrate temperature of 550 °C and at a VI/III flux ratio greater than 15. Extra diffraction spots with weak intensity were observed in reflection high-energy electron diffraction patterns of the Ga2Se3 films grown at a VI/III ratio above 150. These extra spots were also observed in the transmission electron diffraction pattern. The extra points are attributed to the ordering of native Ga vacancies in the defect zinc blende structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105388
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  • 7
    Electronic Resource
    Electronic Resource
    Internal-external transition for the oxidation of Fe-Cr-Ni austenitic stainless steels in steam (1989)
    Springer
    Oxidation of metals 32 (1989), S. 13-45 
    Details
    ISSN: 1573-4889
    Keywords: steam oxidation ; external oxidation ; internal oxidation ; grain-size effect of the base metal ; austenitic stainless steels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several Fe-Cr-Ni austenitic stainless steels (Cr wt.%: 13–25, Ni wt.%: 15) were oxidized in steam for 1000 hr at 500–900°C. The oxide scales were examined and categorized with respect to the chromium concentration and the grain size of the base metal. Experiments showed three conditions for the critical bulk Cr concentration and the oxidation temperature at which the oxidation behavior changed drastically. Metallographic examination showed that two of these three conditions resulted from the internal-external transition of Cr2O3 either on the metal surface or along the grain boundaries of the base metal. Attempts were made to interpret these conditions from the available oxidation theories. Atkinson's treatment was employed with some modification to incorporate the grain-boundary diffusion of Cr in the base metal. The calculation basically explained the internal-external transition for the oxidation of these steels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665267
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  • 8
    Electronic Resource
    Electronic Resource
    Deformation of FeO Oxide Scales upon Tensile Tests at 600-1200°C (2001)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 369-372 (Oct. 2001), p. 555-562 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/05/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.369-372.555.pdf
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