Direct Approach to Atomistic Ab Initio Studies of Precipitate Growth in Alloys

2009 ◽  
Vol 1229 ◽  
Author(s):  
Flemming JH Ehlers ◽  
Randi Holmestad
Keyword(s):  
Ab Initio ◽  
Active Role ◽  
Experimental Information ◽  
Host Lattice ◽  
Model System ◽  
Direct Approach ◽  
Conventional View ◽  
Atomistic Modelling ◽  
Transmission Electron ◽  
Precipitate Growth

AbstractA dramatic gain in the knowledge of precipitate formation, composition, and evolution in alloys has been achieved in the recent years with improvement of transmission electron microscopy techniques for direct structural imaging [1]. A detailed understanding of the microstructure is often essential for control and manipulation of materials properties: an important example for metals is the significant hardening of Al alloys by particular precipitates from a sequence strongly dependent on alloying element concentration and the treatment of the material [2]. The wealth of experimental information provides a playground for theory in the context of elucidating precipitate growth mechanisms and influence on the host material. A head-on approach to atomistic modelling of these phenomena using an ab initio based scheme is conventionally deemed highly desired but impractical. The basic argument is that the system of any reasonably sized (i.e. realistic) and well isolated microstructure will simply contain too many atoms. We will challenge this conventional view: it is argued that most of the atoms of the above mentioned system do not play an active role in the growth discussion, hence need not be included in the modelling. Subsequently, a model system is presented which offers a highly accurate description of the interface between the host lattice and a microstructure of an arbitrary size, for the case where this interface is coherent and compositionally abrupt. When used in conjunction with other approaches already available, this model system offers a direct approach to atomistic ab initio studies of microstructure growth. A general introduction to the modelling scheme will be presented, with the particular application being the main hardening precipitate β'' in the Al-Mg-Si alloy. [1] K. W. Urban, Nature Mater. 8, 260 (2009). [2] C. D. Marioara, S. J. Andersen, H. W. Zandbergen, and R. Holmestad, Metal. Mater. Trans. A 36A, 691 (2005).

A standard for transmission electron spectroscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 530-531 ◽  
Author(s):  
Dennis Maher ◽  
David Joy ◽  
Peggy Mochel
Keyword(s):  
Thin Films ◽  
Electron Spectroscopy ◽  
Host Lattice ◽  
Single Element ◽  
Multicomponent Systems ◽  
Transmission Electron ◽  
Major Interest ◽  
Standard Specimens ◽  
Forms Of Carbon ◽  
Electron Energy Loss

A variety of standard specimens is needed in order to systematically investigate the instrumentation, specimen, data reduction and quantitation variables in electron energy-loss spectroscopy (EELS). Pure single element specimens (e.g. various forms of carbon) have received considerable attention to date but certain elements of interest cannot be prepared directly as thin films. Since studies of the first and second row elements in two- or multicomponent systems will be of considerable importance in microanalysis using EELS, there is a need for convenient standards containing these species. For many investigations a standard should contain the desired element, or elements, homogeneously dispersed through a suitable matrix and at an accurately known concentration. These conditions may be met by the technique of implantation.Silicon was chosen as the host lattice since its principal ionization energies, EL23 = 98 eV and Ek = 1843 eV, are well removed from the K-edges of most elements of major interest such as boron (Ek = 188 eV), carbon (Ek = 283 eV), nitrogen (Ek = 400 eV) and oxygen (Ek = 532 eV).

An Ultrastructural Comparison of Hepatocytes from ADH+ and ADH−Peromyscus Maniculatus

1996 ◽  
Vol 54 ◽  
pp. 30-31
Author(s):  
J. T. Ellzey ◽  
D. Borunda ◽  
B. P. Stewart
Keyword(s):  
South Carolina ◽  
Adult Male ◽  
Uranyl Acetate ◽  
Model System ◽  
Deer Mice ◽  
En Bloc ◽  
Genetic Stock ◽  
Hepes Buffer ◽  
Transmission Electron ◽  
Color Scanner

Genetically alcohol deficient deer mice (ADHN/ADHN) (obtained from the Peromyscus Genetic Stock Center, Univ. of South Carolina) lack hepatic cytosolic alcohol dehydrogenase. In order to determine if these deer mice would provide a model system for an ultrastructural study of the effects of ethanol on hepatocyte organelles, 75 micrographs of ADH+ adult male deer mice (n=5) were compared with 75 micrographs of ADH− adult male deer mice (n=5). A morphometric analysis of mitochondrial and peroxisomal parameters was undertaken.The livers were perfused with 0.1M HEPES buffer followed by 0.25% glutaraldehyde and 2% sucrose in 0.1M HEPES buffer (4C), removed, weighed and fixed by immersion in 2.5% glutaraldehyde in 0.1M HEPES buffer, pH 7.4, followed by a 3,3’ diaminobenzidine (DAB) incubation, postfixation with 2% OsO4, en bloc staining with 1% uranyl acetate in 0.025M maleate-NaOH buffer, dehydrated, embedded in Poly/Bed 812-BDMA epon resin, sectioned and poststained with uranyl acetate and lead citrate. Photographs were taken on a Zeiss EM-10 transmission electron microscope, scanned with a Howtek personal color scanner, analyzed with OPTIMAS 4.02 software on a Gateway2000 4DX2-66V personal computer and stored in Excel 4.0.

Atomic and Electronic Structure of Boron-Doped Diamond Grain Boundaries Studied by Arhvtem and ab-Initio Calculation

2003 ◽  
Vol 764 ◽  
Author(s):  
Hiroyuki Togawa ◽  
Hideki Ichinose
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Ab Initio Calculation ◽  
Structure Model ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Transmission Electron ◽  
Diamond Grain ◽  
Electron Energy Loss ◽  
Atomic And Electronic Structure

AbstractAtomic resolution high-voltage transmission electron microscopy and electron energy loss spectroscopy were performed on grain boundaries of boron-doped diamond, cooperated with the ab-initio calculation. Segregated boron in the {112}∑3 boundary was caught by the EELS spectra. The change in atomic structure of the segregated boundary was successfully observed from the image by ARHVTEM. Based on the ARHVTEM image, a segregted structure model was proposed.

scholarly journals Ab Initio Prediction of the Redox Potentials of 3d Transition Metals Embedded in a Semiconducting Host Lattice

2021 ◽  
Vol 125 (7) ◽  
pp. 4267-4276
Author(s):  
William Lafargue-Dit-Hauret ◽  
Camille Latouche ◽  
Stéphane Jobic
Keyword(s):  
Transition Metals ◽  
Ab Initio ◽  
Host Lattice ◽  
Redox Potentials ◽  
Ab Initio Prediction

Structure and Stability of Grain Boundaries in Molybdenum with Segregated Carbon Impurities

1999 ◽  
Vol 578 ◽  
Author(s):  
R. Janisch ◽  
T. Ochs ◽  
A. Merkle ◽  
C. Elsässer
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Carbide Phases ◽  
Carbon Impurities ◽  
Transmission Electron ◽  
Local Density Functional Theory ◽  
Symmetrical Tilt

AbstractThe segregation of interstitial impurities to symmetrical tilt grain boundaries (STGB) in bodycentered cubic transition metals is studied by means of ab-initio electronic-structure calculations based on the local density functional theory (LDFT). Segregation energies as well as changes in atomic and electronic structures at the ΣE5 (310) [001] STGB in Mo caused by segregated interstitial C atoms are investigated. The results are compared to LDFT data obtained previously for the pure Σ5 (310) [001] STGB in Mo. Energetic stabilities and structural parameters calculated ab initio for several crystalline Molybdenum Carbide phases with cubic, tetragonal or hexagonal symmetries and different compositions, MoCx, are reported and compared to recent high-resolution transmission electron microscopy (HRTEM) observations of MoCx, intergranular films and precipitates formed by C segregation to a Σ5 (310) [001] STGB in a Mo bicrystal.

How Does Co-Creation Affect Customer’s Purchase Intention?

2018 ◽  
Vol 03 (01) ◽  
pp. 1850005 ◽  
Author(s):  
Yang Bai
Keyword(s):  
Purchase Intention ◽  
Active Role ◽  
Sales Performance ◽  
Conventional View ◽  
Business System ◽  
The Difference ◽  
End Stage

In a conventional view, customers just purchase the goods or services created by companies. But the role of customers has changed. Now customers are seeking to practice their influence in every part of the business system as a co-creator. What is co-creation? Is it like customization? The answer is yes and no. The difference between co-creation and customization depends on the degree of involvement of the customer in the business. Generally, the customer plays a much more active role in co-creation than customization. Co-creation refers to almost every part of a business, but customization is restricted to the end stage of production. Co-creation can happen in the process of sales support, which can ultimately improve sales performance. This paper illustrates the relationships among co-creation, sales support and sales performance, and designs an experiment to test.

In SituHigh-Resolution Electron Spectroscopic Imaging and Real-Time Image Simulation of Precipitate Growth Mechanisms

1997 ◽  
Vol 3 (S2) ◽  
pp. 627-628
Author(s):  
J. M. Howe ◽  
M. M. Tsai ◽  
A. A. Csontos
Keyword(s):  
Atomic Level ◽  
Interface Motion ◽  
Bonding Structure ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Precipitate Growth ◽  
The Matrix ◽  
Interphase Boundaries ◽  
Transformation Mechanisms ◽  
Kinetics Of

Precipitate interfaces are ideal for studying the relationship between atomic bonding, structure and composition at internal interfaces and the mechanisms and kinetics of their motion as a function of temperature or driving force for reaction. The crystallography between coherent and semicoherent precipitates and the matrix is well-defined and the precipitate interfaces are often planar and grow by a terrace-ledge-kink mechanism, making them well-suited for study by conventional and high-resolution transmission electron microscopy (HRTEM).Motion of precipitate interfaces, or more generally, interphase boundaries, involves a change in lattice, composition or both. In order to understand the mechansims of interfacial motion, it is necessary to determine the structural and compositional changes that occur at the highest possible resolution, i.e., as close to the atomic level as possible, and also, to determine the corresponding kinetics of interface motion. HRTEM is an excellent technique for determining the atomic structure of transformation interfaces and in situhot-stage HRTEM is deal for determining interface dynamics at the atomic level, provided the transformation mechanisms are not altered by the thinness of the TEM foil.

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