Shape and Internal Structure of Silver Nanoparticles Embedded in Glass

2005 ◽  
Vol 20 (6) ◽  
pp. 1551-1562 ◽  
Author(s):  
H. Hofmeister ◽  
G.L. Tan ◽  
M. Dubiel
Keyword(s):  
Silver Nanoparticles ◽  
Lattice Structure ◽  
Structural Characteristics ◽  
Hexagonal Lattice ◽  
High Resolution Electron Microscopy ◽  
Size Dependent ◽  
Resolution Electron ◽  
Formation Conditions ◽  
Fringe Patterns

The structural characteristics of silver nanoparticles embedded in glass by various routes of fabrication were studied in detail using high-resolution electron microscopy to find out if they are influenced by interaction with the surrounding glass matrix. Besides the formation conditions, the strength of the interaction between metal and glass governs the size-dependent changes of lattice spacings in such nanoparticles. However, determination of these changes is not straightforward because of complicated particle configurations and the interference nature of the lattice imaging technique. Imaging of lattice plane fringes and careful diffractogram analysis allowed the exclusion of any kind of tetragonal lattice distortion or transformation to hexagonal lattice type that may be deduced at first sight. Instead, the formation of twin faults in these nanoparticles turned out to be the essential structural feature and the main source of confusion about the lattice structure observed. The variety of particle forms is comparable to particles supported on oxide carriers. It is composed of single-crystalline particles of nearly cuboctahedron shape, particles containing single twin faults, multiple twinned particles containing parallel twin lamellae, and multiple twinned particles composed of cyclic twinned segments arranged around axes of 5-fold symmetry. The more twin planes involved in the particle composition, the more complicated is the interpretation of lattice spacings and lattice fringe patterns due to superposition of several twin segments.

Microstructural determination of a metastable phase during rhodium oxidation

1989 ◽  
Vol 47 ◽  
pp. 262-263
Author(s):  
A. David Logan
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Volume Expansion ◽  
Lattice Structure ◽  
Metastable Phase ◽  
Active Surface ◽  
High Resolution Electron Microscopy ◽  
Silica Spheres ◽  
Resolution Electron

In heterogeneous catalysis, oxidation of the catalyst is frequently used as a means of removing impurities from the active surface. However, bulk oxidation severely alters the microstructure of the metal due to atom repositioning and valence changes. Transformation of Rh to Rh2O3 causes the lattice structure to change from fcc to hexagonal with a resulting volume expansion of 90% due to density changes. This is the reported cause for fracturing of crystallites and variations in reactivity. In this study, microstructural changes during progressive oxidation of 5 nm metal Rh particles have been examined.A 2 wt% Rh/Silica catalyst was prepared using Rh(III)-2,4 pentanedionate as a precursor and nonporous silica spheres as a support. The catalyst was then reduced in flowing H2 at 473 K. High resolution electron microscopy (HREM) was performed on a JEM-4000EX having a point resolution of 0.17 nm. The catalyst was oxidized in research purity O2 (Matheson 99.99%) using an all glass volumetric chemisorption system.

scholarly journals Determination of the structural aspects of favored grain boundary reaction sites

1978 ◽  
Vol 36 (1) ◽  
pp. 408-409
Author(s):  
Ronald Gronsky ◽  
Gareth Thomas
Keyword(s):  
Grain Boundary ◽  
Early Stage ◽  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Growth Front ◽  
Grain Boundary Plane ◽  
Nucleation Sites ◽  
Resolution Electron ◽  
Boundary Reaction

Of the techniques which have been employed in the study of grain boundary precipitation reactions, none have demonstrated sufficient resolution to directly reveal the structural characteristics of active nucleation sites. This information is vital since many existing interpretations of conventional TEM data are in conflict.The present paper describes an application of high resolution electron microscopy which distinguishes atomic level details in both the boundary and growth front regions of grain boundary precipitates, and indicates the structure and mechanisms responsible for enhanced reaction kinetics.Experiments were performed on an Al-9.5 at.% Zn alloy aged for 30 mins, at 180°C to encourage heterogeneous nucleation at grain boundaries. Two examples of early stage grain boundary precipitates are shown in Fig. 1, both of which have been nucleated in the lower grain. It is seen that in (b) the precipitate is much more sharply faceted than in (a). Notably the orientation of the grain boundary plane is very near to that of the close-packed {111} matrix planes of the lower grain for precipitate (b), whereas the boundary is sharply inclined to {111} for precipitate (a).

High-resolution electron microscopy of the atomic structure of some grain boundaries in Au

1986 ◽  
Vol 44 ◽  
pp. 414-415
Author(s):  
W. Krakow ◽  
D. A. Smith
Keyword(s):  
Atomic Structure ◽  
High Resolution Electron Microscopy ◽  
Image Features ◽  
Image Feature ◽  
Resolution Electron ◽  
Tilt Boundaries ◽  
Processing Techniques ◽  
Atom Position ◽  
Structure Configuration

The successful determination of the atomic structure of [110] tilt boundaries in Au stems from the investigation of microscope performance at intermediate accelerating voltages (200 and 400kV) as well as a detailed understanding of how grain boundary image features depend on dynamical diffraction processes variation with specimen and beam orientations. This success is also facilitated by improving image quality by digital image processing techniques to the point where a structure image is obtained and each atom position is represented by a resolved image feature. Figure 1 shows an example of a low angle (∼10°) Σ = 129/[110] tilt boundary in a ∼250Å Au film, taken under tilted beam brightfield imaging conditions, to illustrate the steps necessary to obtain the atomic structure configuration from the image. The original image of Fig. 1a shows the regular arrangement of strain-field images associated with the cores of ½ [10] primary dislocations which are separated by ∼15Å.

Combined Experimentaland Theoretical Determination of the Atomic Structure of the (310) Twin in NB

1991 ◽  
Vol 238 ◽  
Author(s):  
Geoffrey H. Campbells ◽  
Wayne E. King ◽  
Stephen M. Foiles ◽  
Peter Gumbsch ◽  
Manfred Rühle
Keyword(s):  
High Resolution ◽  
Theoretical Models ◽  
High Resolution Electron Microscopy ◽  
Interatomic Potentials ◽  
Image Simulation ◽  
Theoretical Determination ◽  
Atomic Structures ◽  
Resolution Electron ◽  
High Resolution Images

ABSTRACTA (310) twin boundary in Nb has been fabricated by diffusion bonding oriented single crystals and characterized using high resolution electron microscopy. Atomic structures for the boundary have been predicted using different interatomic potentials. Comparison of the theoretical models to the high resolution images has been performed through image simulation. On the basis of this comparison, one of the low energy structures predicted by theory can be ruled out.

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.

The decagonal quasicrystal formed from an Al–Pd–Mn icosahedral quasicrystal

1995 ◽  
Vol 10 (5) ◽  
pp. 1146-1153 ◽  
Author(s):  
W. Sun ◽  
K. Hiraga
Keyword(s):  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Icosahedral Quasicrystal ◽  
Two Phase ◽  
Growth Interface ◽  
Decagonal Quasicrystal ◽  
Resolution Electron ◽  
The Matrix ◽  
Solid State Phase Transformation ◽  
Phase Proceeds

We present a detailed investigation on the decagonal quasicrystal (D-phase) formed from an Al-Pd-Mn icosahedral quasicrystal (I-phase) through a solid-state phase transformation, including its formation, compositional and crystallographical relationships with the matrix I-phase, growth mode, and structural characteristics. The as-melt-spun Al70Pd20Mn10 alloy contains only I-phase. By annealing at 800 °C, the D-phase is found to grow cpitaxially from the I-phase to establish a D/I two-phase equilibrium with distinctly different composition between them. The D-phase exhibits a stepped growth interface, which consists of a facet plane, formed by sharing the tenfold plane with a fivefold plane of the matrix I-phase, and some ledges across it. The growth of the D-phase into the I-phase proceeds through lateral movement of the ledges along the tenfold plane. High-resolution electron microscopy reveals that the structure of the D-phase is constructed by an aperiodic arrangement of decagonal atom clusters with definite linkages and long-range quasiperiodic correlation.

Growth Phenomena of Quantum Dot Structures in the Ingaas System Investigated by Tem Techniques

1999 ◽  
Vol 583 ◽  
Author(s):  
P. Werner
Keyword(s):  
Electron Microscopy ◽  
Lattice Strain ◽  
Lattice Structure ◽  
Imaging Techniques ◽  
High Resolution Electron Microscopy ◽  
3 Dimensional ◽  
Gaas Matrix ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Optical Behavior

AbstractThe contribution is mainly focused on the formation and properties of InGaAs islands (quantum dots, QD) in a GaAs matrix, viz. a system showing properties similar to those of other materials systems. Depending on the growth techniques applied (MBE or MOCVD), the islands/dots differ in size, shape, chemical composition, and lattice strain. These parameters influence strongly the optical properties of QD structures, which might consist of single layers or complex 3-dimensional arrays. To reveal the correlation between the morphology/structure and the optical behavior of such systems different analytical methods are available, more effective in some combined applications. The present paper is mainly focused on the possibilities and limitations of transmission electron microscopy (TEM) to analyze the lattice structure of QDs down to the nm-range. Such TEM investigations imply a general problem: to deconvolute separately information on the QD size, shape (e.g., pyramidal or spherical islands), strain and composition. TEM imaging techniques used for such structural analyses will be described, including conventional diffraction contrast and high-resolution electron microscopy, respective examples of which will be presented. For the chemical analysis energy sensitive techniques (e.g., energy filtered images) are appropriate methods. Applications and limitations of such investigations will be discussed.

Comparative Studies of the Degradation of Several Zeolites Under Electron Irradiation

1987 ◽  
Vol 111 ◽  
Author(s):  
D. R. Acosta ◽  
O. Guzman ◽  
P. Del Angel ◽  
J. Dominguez
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Electron Irradiation ◽  
Comparative Studies ◽  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Degradation Process ◽  
Optical Parameters ◽  
Resolution Electron

High resolution electron microscopy has proven to be a powerful technique to determine structural characteristics of zeolites (l–2),symmetry variations and identification of several kind of defects.Together with ideal projected potential images, the microscopist usually finds in electron micrographs the influence of electro-optical parameters and alterations of the crystallinity of the material under electron irradiation. One of the purposes of this workis to contributetothe understanding of the degradation process of zeolites under electron irradiation in the electron microscope and in this way, discriminate when it is possible, what is reliable information recorded in the images obtained in high resolution conditions.

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