The Extended Defect as a Mechanism for the Immobilization of HLW Species in Zirconolite, Perovskite and Hollandite

1985 ◽  
Vol 50 ◽  
Author(s):  
T. J. White
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Continuous Solid Solution ◽  
Analytical Electron Microscopy ◽  
Glass Ceramics ◽  
High Resolution Electron Microscopy ◽  
High Level Waste ◽  
Isomorphic Substitution ◽  
Extended Defects ◽  
Extended Defect

AbstractHigh resolution electron microscopy, analytical electron microscopy and selected area electron diffraction are used to establish the crystallochemical mechanisms by which simulated high level waste enters Synroc. It is shown that waste species are incorporated largely as a non-continuous solid solution. In other words, simple isomorphic substitution of waste elements in place of matrix cations, i.e. the classical continuous solid solution, does not operate (or is only significant at very low waste levels of radwaste). Usually, substitution is accompanied by the appearance of coherent extended defects which can take the form of antiphase boundaries, unit cell twinning (both mimetic and polysynthetic), or cation ordering. In this manner, a numb~er of closely related phases appear in response to variations in waste composition and loading. It is believed that the mechanism of structural modification will endow Synroc with considerable flexibility to respond to chemical changes in the wastestream. Other ceramic materials currently being evaluated as possible wasteforms (viz. sphene glass-ceramics and APO4 phosphates), are also likely to possess this capacity.

Application of analytical electron microscopy to studies of equilibrium and non-equilibrium segregation in materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1214-1215
Author(s):  
Edward A Kenik
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Extended Defects ◽  
Probe Diameter ◽  
Specimen Holder ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Solute Atoms ◽  
Equilibrium Segregation ◽  
Non Equilibrium

Segregation of solute atoms to grain boundaries, dislocations, and other extended defects can occur under thermal equilibrium or non-equilibrium conditions, such as quenching, irradiation, or precipitation. Generally, equilibrium segregation is narrow (near monolayer coverage at planar defects), whereas non-equilibrium segregation exhibits profiles of larger spatial extent, associated with diffusion of point defects or solute atoms. Analytical electron microscopy provides tools both to measure the segregation and to characterize the defect at which the segregation occurs. This is especially true of instruments that can achieve fine (<2 nm width), high current probes and as such, provide high spatial resolution analysis and characterization capability. Analysis was performed in a Philips EM400T/FEG operated in the scanning transmission mode with a probe diameter of <2 nm (FWTM). The instrument is equipped with EDAX 9100/70 energy dispersive X-ray spectrometry (EDXS) and Gatan 666 parallel detection electron energy loss spectrometry (PEELS) systems. A double-tilt, liquid-nitrogen-cooled specimen holder was employed for microanalysis in order to minimize contamination under the focussed spot.

Interface structures in polycrystalline ceramic materials

1986 ◽  
Vol 44 ◽  
pp. 468-471
Author(s):  
K. J. Morrissey
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Physical And Mechanical Properties ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Polycrystalline Materials ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Interface Structures

Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.

scholarly journals Analytical High-resolution Electron Microscopy Reveals Organ-specific Nanoceria Bioprocessing

2017 ◽  
Vol 46 (1) ◽  
pp. 47-61 ◽  
Author(s):  
Uschi M. Graham ◽  
Robert A. Yokel ◽  
Alan K. Dozier ◽  
Lawrence Drummy ◽  
Krishnamurthy Mahalingam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Organ Specific

This is the first utilization of advanced analytical electron microscopy methods, including high-resolution transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, electron energy loss spectroscopy, and energy-dispersive X-ray spectroscopy mapping to characterize the organ-specific bioprocessing of a relatively inert nanomaterial (nanoceria). Liver and spleen samples from rats given a single intravenous infusion of nanoceria were obtained after prolonged (90 days) in vivo exposure. These advanced analytical electron microscopy methods were applied to elucidate the organ-specific cellular and subcellular fate of nanoceria after its uptake. Nanoceria is bioprocessed differently in the spleen than in the liver.

Phase relationships in the Fe-rich region of the Ce–Nd–B–Fe quaternary system at 773 K

2021 ◽  
Vol 112 (9) ◽  
pp. 726-734
Author(s):  
Ketong Luo ◽  
Jianlie Liang ◽  
Jinming Zhu ◽  
Xuehong Cui
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Quaternary System ◽  
Continuous Solid Solution ◽  
Rich Region ◽  
Quaternary Compound ◽  
X Ray ◽  
Three Phase ◽  
Scanning Electron ◽  
Phase Relationships

Abstract The Fe-rich corner of the Ce–Nd–B–Fe quaternary system at 773 K has been experimentally investigated by means of X-ray powder diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy techniques. No quaternary compound was observed in this system. Ce2Fe14B and Nd2Fe14B were found to form the continuous solid solution (Ce,Nd)2Fe14B. Ce-Fe4B4 and NdFe4B4 also form the solid solution (Ce,Nd)-Fe4B4. The isothermal section consists of 8 three-phase regions and 2 four-phase regions.

Structure, Composition and Stability of Heterophase Boundaries

1997 ◽  
Vol 3 (S2) ◽  
pp. 673-674
Author(s):  
M. Rühle ◽  
T. Wagner ◽  
S. Bernath ◽  
J. Plitzko ◽  
C. Scheu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Elevated Temperatures ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Advanced Materials ◽  
Bulk Crystals ◽  
Transmission Electron ◽  
Resolution Electron ◽  
The Stability

Heterophase boundaries play an important role in advanced materials since those materials often comprise different components. The properties of the materials depend strongly on the properties of the interface between the components. Thus, it is important to investigate the stability of the microstructure with respect to annealing at elevated temperatures. In this paper results will be presented on the structure and composition of the interfaces between Cu and (α -Al2O3. The interfaces were processed either by growing a thin Cu overlayer on α- Al2O3 in a molecular beam epitaxy (MBE) system or by diffusion bonding bulk crystals of the two constituents in an UHV chamber. To improve the adhesion of Cu to α -Al2O3 ultrathin Ti interlayers were deposited between Cu and α - Al2O3.Interfaces were characterized by different transmission electron microscopy (TEM) techniques. Quantitative high-resolution electron microscopy (QHRTEM) allows the determination of the structure (coordinates of atoms) while analytical electron microscopy (AEM) allows the determination of the composition with high spatial resolution.

Crystal Structure of and Defects in the Pentacene Thin Film Phase

2002 ◽  
Vol 734 ◽  
Author(s):  
Lawrence F. Drummy ◽  
Paul K. Miska ◽  
David C. Martin
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Low Voltage ◽  
Field Effect Transistors ◽  
High Resolution Electron Microscopy ◽  
Orthorhombic Symmetry ◽  
Extended Defects ◽  
X Ray Diffraction ◽  
Voltage Electron ◽  
Resolution Electron

The aromatic hydrocarbon pentacene is currently under investigation for use as the active layer in electronic devices such as thin film field effect transistors. We have used X-Ray Diffraction (XRD), Electron Diffraction (ED), Low Voltage Electron Microscopy (LVEM), High Resolution Electron Microscopy (HREM) and molecular modeling to investigate the thin film phase of pentacene. We will report the orthorhombic symmetry and lattice parameters of the thin film phase measured experimentally from these techniques. The structure of extended defects such as dislocations and grain boundaries will influence the electrical and mechanical characteristics of the films. Here we show a direct image of an edge dislocation in the thin film phase and discuss the way in which the lattice accommodates the defect.

The effect of doping Ag on the microstructure of La2/3Sr1/3MnO3 films

2002 ◽  
Vol 17 (10) ◽  
pp. 2712-2719 ◽  
Author(s):  
Q. Zhan ◽  
R. Yu ◽  
L. L. He ◽  
D. X. Li ◽  
J. Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Doping Level ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Plan View ◽  
Ag Doping ◽  
Low Field ◽  
Resolution Electron ◽  
Magnetic Spin

The microstructure of Ag-doped La2/3Sr1/3MnO3 (LSMO) thin films deposited on (001) LaAlO3 single-crystal substrates was systematically investigated in cross section and plan view by high-resolution electron microscopy and analytical electron microscopy. The results showed that the films deposited at 750 °C were perfectly epitaxial with or without Ag-doping. No Ag in the doped film was detected. On the other hand, the LSMO films deposited at 400 °C were less perfect. With increasing Ag-doping level, the shape of LSMO grains became irregular, and the grain size increased gradually. Large polycrystalline clusters consisting of LSMO, AgO, and Ag grains formed in the doped films, and the amount and size of them increased with increasing Ag-doping level. Ag existed at the LSMO grain boundaries in its elemental state. A growth process for the LSMO-Ag system is discussed based on the experimental results. The enhancement of the magnetic spin disorders at the grain boundaries and interfaces caused by doping Ag could result in an improvement of low-field magnetoresistance.

Local Mechanical Properties of Cu-Co Alloys with Coherent Co Precipitates

2015 ◽  
Vol 662 ◽  
pp. 15-18
Author(s):  
Jiří Buršík ◽  
Vilma Buršíková ◽  
Milan Svoboda
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Solid Solution ◽  
Thermal Treatment ◽  
Analytical Electron Microscopy ◽  
Water Quenching ◽  
Large Area ◽  
Analytical Electron ◽  
Indentation Tests ◽  
Co Alloys

In this work the influence of the thermal treatment on the local mechanical properties of model diluted Cu-Co alloys with Co content of 4 at.% is investigated. The samples underwent annealing at 1273 K followed by water quenching. The further thermal treatment at 1073 K of the oversaturated solid solution generated a fine distribution of Co-rich precipitates. Parameters of microstructure were evaluated by means of analytical electron microscopy. The nanoscale mechanical properties of precipitates, areas adjacent to the precipitates and precipitate-free zones were studied using large area grid indentation tests. Moreover, the modulus mapping capability was applied to obtain quantitative maps of the storage and loss stiffness and modulus.

An investigation of grain boundaries in submicrometer-grained Al-Mg solid solution alloys using high-resolution electron microscopy

1996 ◽  
Vol 11 (8) ◽  
pp. 1880-1890 ◽  
Author(s):  
Zenji Horita ◽  
David J. Smith ◽  
Minoru Furukawa ◽  
Minoru Nemoto ◽  
Ruslan Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Boundary Energy ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Structural Features ◽  
Resolution Electron

High-resolution electron microscopy was used to examine the structural features of grain boundaries in Al–1.5% Mg and Al–3% Mg solid solution alloys produced with submicrometer grain sizes using an intense plastic straining technique. The grain boundaries were mostly curved or wavy along their length, and some portions were corrugated with regular or irregular arrangements of facets and steps. During exposure to high-energy electrons, grain boundary migration occurred to reduce the number of facets and thus to reduce the total boundary energy. The observed features demonstrate conclusively that the grain boundaries in these submicrometer-grained materials are in a high-energy nonequilibrium configuration.

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