Temperature Dependence of Carbon Deposits within Oxide Scale on CrMoV Steel in Atmospheric and Supercritical CO2

We studied the temperature dependence of the emission and absorption of PbS quantum dots deposited on glass by a supercritical CO2 fluid process. The results show that the emission is ruled by different transitions than the absorption, particularly at cryogenic temperatures. We found indications that these observations can be linked to the PbS concentration used to form the films in conjunction with the capability of the supercritical CO2 method to form dense homogeneous films.

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Enhanced Internal Oxidation as Reason for Breakdown of Protective Chromia Scales on FeCr-Alloys in Water Vapour Containing Gases

Materials Science Forum ◽

10.4028/www.scientific.net/msf.595-598.699 ◽

2008 ◽

Vol 595-598 ◽

pp. 699-706 ◽

Cited By ~ 9

Author(s):

E. Essuman ◽

Gerald H. Meier ◽

J. Zurek ◽

Michael Hänsel ◽

Lorenz Singheiser ◽

...

Keyword(s):

Raman Spectroscopy ◽

Water Vapor ◽

Temperature Dependence ◽

Oxide Scale ◽

Water Vapour ◽

Internal Oxidation ◽

Transport Processes ◽

Oxidation Behaviour ◽

Surface Oxide ◽

Protective Behaviour

The oxidation behaviour of binary Fe-Cr alloys containing 10 and 20 mass % Cr, respectively, was studied in Ar-20%O2, Ar-7%H2O and in Ar-4%H2-7%H2O at temperatures between 800 and 1050°C. Thermogravimetric analyses in combination with analytical studies using SEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is the source of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar-O2 gas. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the surface oxide scale, the present results reveal that the presence of water vapor also affects the transport processes in the alloy. The enhanced internal oxidation, which is likely the result of water vapor increasing the solubility and/or the diffusivity of oxygen in the alloy, explains the frequently observed effect that Fe(Ni)Cr alloys with intermediate Cr contents (e.g. 10-20%, depending on temperature) exhibit protective oxidation in dry gases but breakaway type oxidation in steam. The temperature dependence of the change from protective to non-protective behaviour in Ar-H2O differs quantitatively, but not qualitatively from that in Ar-O2.

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Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053188 ◽

1982 ◽

Vol 40 ◽

pp. 78-79

Author(s):

Kenneth H. Downing ◽

Robert M. Glaeser

Keyword(s):

Electron Beam ◽

Fatty Acid ◽

Inelastic Scattering ◽

Temperature Dependence ◽

Structural Damage ◽

Direct Result ◽

Second Step ◽

Strong Temperature Dependence ◽

Electron Dose ◽

Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

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Structural Imperfections in thin Oxide Films Formed on Some Fe- and Ni-Base Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069545 ◽

1970 ◽

Vol 28 ◽

pp. 510-511

Author(s):

L. P. Lemaire ◽

D. E. Fornwalt ◽

F. S. Pettit ◽

B. H. Kear

Keyword(s):

Oxide Scale ◽

Oxidation Process ◽

Short Circuit ◽

Protective Oxide ◽

Protective Oxide Scale ◽

Thin Oxide Films ◽

Diffusion Paths ◽

Oxidation Resistant ◽

Structural Imperfections ◽

Short Circuit Diffusion

Oxidation resistant alloys depend on the formation of a continuous layer of protective oxide scale during the oxidation process. The initial stages of oxidation of multi-component alloys can be quite complex, since numerous metal oxides can be formed. For oxidation resistance, the composition is adjusted so that selective oxidation occurs of that element whose oxide affords the most protection. Ideally, the protective oxide scale should be i) structurally perfect, so as to avoid short-circuit diffusion paths, and ii) strongly adherent to the alloy substrate, which minimizes spalling in response to thermal cycling. Small concentrations (∼ 0.1%) of certain reactive elements, such as yttrium, markedly improve the adherence of oxide scales in many alloy systems.

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Temperature Dependence of Magnetic Domains and Wall Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009573x ◽

1972 ◽

Vol 30 ◽

pp. 496-497

Author(s):

Sonoko Tsukahara ◽

Tadami Taoka ◽

Hisao Nishizawa

Keyword(s):

Temperature Dependence ◽

Domain Walls ◽

Magnetic Domain ◽

Iron Film ◽

Objective Lens ◽

Lorentz Microscopy ◽

Domain Structures ◽

Wall Structures ◽

Crystal Films ◽

Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

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Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009587x ◽

1972 ◽

Vol 30 ◽

pp. 524-525

Author(s):

C. S. Giggins ◽

J. K. Tien ◽

B. H. Kear ◽

F. S. Pettit

Keyword(s):

Electron Microscopy ◽

Oxide Scale ◽

Oxidation Resistance ◽

Substrate Surface ◽

Morphological Features ◽

Thermally Induced ◽

Oxide Spallation ◽

Oxidation Resistant ◽

Induced Stresses ◽

Substrate Surfaces

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).

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