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Materials Science and Engineering

1994

Articles 1 - 6 of 6

Full-Text Articles in Physics

36th Rocky Mountain Conference On Analytical Chemistry Jul 1994

36th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Program, abstracts, and information about the 36th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31 - August 5, 1994.

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Compositional Short-Range Ordering In Metallic Alloys: Band-Filling, Charge-Transfer, And Size Effects From A First-Principles All-Electron Landau-Type Theory, J. B. Staunton, Duane D. Johnson, F. J. Pinski Jul 1994

Compositional Short-Range Ordering In Metallic Alloys: Band-Filling, Charge-Transfer, And Size Effects From A First-Principles All-Electron Landau-Type Theory, J. B. Staunton, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

Using a mean-field statistical description, we derive a general formalism to investigate atomic short-range order in alloys based on a density-functional description of the finite-temperature, grand potential of the random alloy. This ‘‘first-principles,’’ Landau-type approach attempts to treat several contributions (electronic structure, Fermi surface, electrostatics, magnetism, etc.) to the electronic energy on an equal footing. An important ingredient for the statistical averaging is the replacement of the molecular mean fields (Weiss fields) with Onsager cavity fields, which forces the diagonal part of the fluctuation-dissipation theorem to be obeyed. To show its general applicability and usefulness, we apply the theory to …

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First-Principles All-Electron Theory Of Atomic Short-Range Ordering In Metallic Alloys: D022- Versus L12-Like Correlations, Duane D. Johnson, J. B. Staunton, F. J. Pinski Jul 1994

First-Principles All-Electron Theory Of Atomic Short-Range Ordering In Metallic Alloys: D022- Versus L12-Like Correlations, Duane D. Johnson, J. B. Staunton, F. J. Pinski

Duane D. Johnson

We use a ‘‘first-principles’’ concentration-wave approach based on a finite-temperature, electronic density-functional, mean-field, grand potential of the random alloy to investigate the high-temperature atomic short-range order (ASRO) in Ni75V25 and Pd75V25 solid solutions. Experimentally, these similar alloys both develop D022-type long-range order at low temperatures but different ASRO at high temperatures. Our calculations describe the measured ASRO well. We compare these results with those found for a hypothetical Co75Ti25 solid solution. Since this alloy orders directly from the melt into the L12 phase, it should exhibit strong L12-like ASRO, as we find in our calculations. We analyze the features in …

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Surface-Induced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha Jul 1994

Surface-Induced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha

Alexander H. King

The surface-induced ordering in thin films of asymmetric deuterated polystyrene (dPS)- poly(viny1pyridine) (PVP) diblock and triblock copolymers of comparable polymerization index and PVP volume fraction - 0.25) was studied using transmission electron microscopy, atomic force microscopy, secondary ion massspectrometry, and neutron reflectivity. The morphology of both di- and triblock copolymer films was found to be cylindrical except for the layer adjacent to the silicon oxide surface, which due to the strong interaction of silica with PVP, was lamellar. The spacing between adjacent cylindrical layers was found to be consistent with mean field theory predictions. In the triblock copolymer films the …

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The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee Jun 1994

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee

Theses and Dissertations

This study on praseodymium Pr luminescence in AlxGa1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 1012 to 5 x 1013 sq cm into AlxGa1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …

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Models For Water Outgassing From Metal Surfaces, Minxu Li Jan 1994

Models For Water Outgassing From Metal Surfaces, Minxu Li

Dissertations, Theses, and Masters Projects

In this study, the outgassing rate from an electropolished stainless steel surface following exposures to H{dollar}\sb2{dollar}O vapor under various conditions was measured. The results of the experiments showed that the outgassing rate is proportional to {dollar}p\sb0\sp{lcub}n{rcub}{dollar}, where {dollar}p\sb0{dollar} is the H{dollar}\sb2{dollar}O exposure pressure and n is about 0.25. The outgassing rate is not as strongly dependent on the system temperature as one would expect if the temperature is kept the same during exposure and pump-down. The outgassing rate is also a function of the exposure time for the first several hours of exposure, indicating that the adsorption saturation time is …

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