• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • Tagged with
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Diffusion in Metals and Intermetallics: an Overview

Mehrer, Helmut 21 September 2022 (has links)
After a few remarks about the history of diffusion in solids we remind the reader to some basics of diffusion such as tracer diffusion, interdiffusion, high- diffusivity paths, and basic diffusion mechanism in solids. We then summarize self-diffusion in cubic, hexagonal metals and metals with phase transformations. Then we summarize diffusion of substitutional impurities (solutes) in metals and remind the reader to the phenomena of slow solute diffusion in aluminium and of fast solute diffusion in polyvalent metals. We finish the part on solute diffusion with some remarks on interstitial impurities We start the part on intermetallic alloys by reminding the reader to some of the more frequent structures. We consider examples of the influence of order-disorder transformation on diffusion. We then discuss diffusion in cubic B2-structured phases and in B2-, L12 - and DO 3- intermetallics, We then discuss uniaxial L1 0 -intermetallics and C11 b-structured molybdenum disilicide. We finish with some remarks diffusion in the cubic Laves phase Co2 Nb.:1. Introduction – some historical remarks 2. Some basics 2.1 Tracer diffusion 2.2 Interdiffusion 2.2.2 The ‘random alloy’ approximation for interdiffusion 2.2.1 Boltzmann-Matano method 2.3 High-diffusivity paths in solids 2.4 Diffusion mechanisms in solids 3. Self-diffusion in metals 3.1 Cubic metals 3.2 Uniaxial metals 3.3 Metals with phase transitions 4, Impurity diffusion in metals 4.1 Diffusion of substitutional impurities 4.2 Slow impurity diffusion in aluminium 4.3 Fast impurity diffusion in polyvalent metals 4.4 Diffusion of fast diffusing interstitial impurities and of hydrogen 5. Diffusion in Intermetallics 5.1 Some structures of intermetallics 5.2 Influence of order-disorder transitions on diffusionThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/1 5.3 Diffusion in B2 phases and B2-intermetallics 5.4 Diffusion in L12-intermetallics 5.5 Diffusion in DO3-intermetallics 5.5 Diffusion in L10-intermetallics 5.6 Diffusion in C11b-structured molybdenum disilicide 5.6 Diffusion in the Laves phase Co 2Nb
2

Ab-initio study of disorder broadening of core photoemission spectra in random metallic alloys

Marten, Tobias January 2004 (has links)
<p>Ab-initio results of the core-level shift and the distribution about the average for the 3<i>d</i><sub>5/2</sub> electrons of Ag, Pd and 2<i>p</i><sub>3/2</sub> of Cu are presented for the face-centered-cubic AgPd and CuPd random alloys. The complete screening model, which includes both initial and final states effects in the same scheme, has been used in the investigations. </p><p>The alloys have been modeled with a supercell containing 256 atoms. Density-functional theory calculations are carried out using the locally self consistent Green's function approach. </p><p>Results from the calculations clearly shows that the core-level shift distributions characteristic is Gaussian, but the components reveals a substantial difference in the FWHM (Full-Width at Half-Maximum). Comparison between the experimental and the calculated broadening shows a remarkable agreement.</p>
3

Ab-initio study of disorder broadening of core photoemission spectra in random metallic alloys

Marten, Tobias January 2004 (has links)
Ab-initio results of the core-level shift and the distribution about the average for the 3d5/2 electrons of Ag, Pd and 2p3/2 of Cu are presented for the face-centered-cubic AgPd and CuPd random alloys. The complete screening model, which includes both initial and final states effects in the same scheme, has been used in the investigations. The alloys have been modeled with a supercell containing 256 atoms. Density-functional theory calculations are carried out using the locally self consistent Green's function approach. Results from the calculations clearly shows that the core-level shift distributions characteristic is Gaussian, but the components reveals a substantial difference in the FWHM (Full-Width at Half-Maximum). Comparison between the experimental and the calculated broadening shows a remarkable agreement.
4

Influence of Global Composition and Local Environment on the Spectroscopic and Magnetic Properties of Metallic Alloys

Olovsson, Weine January 2005 (has links)
<p>Theoretical investigations of spectroscopic and magnetic properties of metallic systems in the bulk, as well as in nanostructured materials, have been performed within the density functional theory. The major part of the present work studies the differences between binding energies of electrons tightly bound to the atoms, the so-called core electrons (in contrast with the valence electrons), that is, core-level binding energy shift (CLS). </p><p>By comparison between corresponding elemental core-levels for atoms situated in different chemical environments we obtain fundamental understanding of bonding properties of materials. The method of choice was the complete screening picture, which includes initial and final state effects on the same footing. The usefulness of CLS stems from that it is sensitive to differences in the chemical environment of an atom, which can be affected on one hand by the global composition of e.g. disordered materials, surfaces and interfaces, and on the other hand by the very local environment around an atom. Here CLSs have been obtained for both components in the fcc random alloys AgPd, CuPd, CuNi, CuPt, CuAu, PdAu, NiPd and NiPt. Moreover the model was extended to the Auger kinetic energy shift for the LMM Auger transition in AgPd alloys. Studies were also applied to the near surface and interface regions of PdMn nano structures on Pd(100), thin CuPd and AgPd films on inert Ru(0001), and at interfaces. The disorder broadening on CLS due to local environment effects was calculated in selected alloys.</p><p>A part of the thesis concern investigations related to the magnetic ordering in Invar alloys, including the influence of local environment effects. A study was made for the dependence of effective exchange parameter on the electron concentration, volume and local chemical composition.</p>
5

Influence of Global Composition and Local Environment on the Spectroscopic and Magnetic Properties of Metallic Alloys

Olovsson, Weine January 2005 (has links)
Theoretical investigations of spectroscopic and magnetic properties of metallic systems in the bulk, as well as in nanostructured materials, have been performed within the density functional theory. The major part of the present work studies the differences between binding energies of electrons tightly bound to the atoms, the so-called core electrons (in contrast with the valence electrons), that is, core-level binding energy shift (CLS). By comparison between corresponding elemental core-levels for atoms situated in different chemical environments we obtain fundamental understanding of bonding properties of materials. The method of choice was the complete screening picture, which includes initial and final state effects on the same footing. The usefulness of CLS stems from that it is sensitive to differences in the chemical environment of an atom, which can be affected on one hand by the global composition of e.g. disordered materials, surfaces and interfaces, and on the other hand by the very local environment around an atom. Here CLSs have been obtained for both components in the fcc random alloys AgPd, CuPd, CuNi, CuPt, CuAu, PdAu, NiPd and NiPt. Moreover the model was extended to the Auger kinetic energy shift for the LMM Auger transition in AgPd alloys. Studies were also applied to the near surface and interface regions of PdMn nano structures on Pd(100), thin CuPd and AgPd films on inert Ru(0001), and at interfaces. The disorder broadening on CLS due to local environment effects was calculated in selected alloys. A part of the thesis concern investigations related to the magnetic ordering in Invar alloys, including the influence of local environment effects. A study was made for the dependence of effective exchange parameter on the electron concentration, volume and local chemical composition.

Page generated in 0.0256 seconds