Short-Range-Ordering and Fe-Clustering in Au-Fe Alloys

1990 ◽  
Vol 205 ◽  
Author(s):  
Chen-Chia Chou ◽  
F.-R. Chen ◽  
C. M. Wayman
Keyword(s):  
Short Range ◽  
Early Stage ◽  
High Resolution Electron Microscopy ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Fe Content ◽  
Resolution Electron ◽  
Short Range Ordering ◽  
Fe Alloys ◽  
Microscopic Techniques

AbstractAs an “archtypal” spin-glass system, the local atomic arrangement in Au-Fe alloys is still a controversial subject. In the present experiment, Au-Fe alloys with Fe content from 10.7 to 33% were studied as to microstructure evolution, through various transmission electron microscopic techniques. Information derived from aging experiments using real and reciprocal spaces appears to suggest the coexistence of short-range-order and Fe-clusters. At early stages of aging, lobe-like and/or rod-shaped strain contrast images, identified as clusters, were revealed after specimens were further cleaned by an ion-miller. The (1 1/2 0) special point diffuse reflections were prominent in the as-quenched condition and/or early stage aging, and the intensifies decrease gradually as aging proceeds. After a certain period, (1 1/2 0) diffuse reflections disappear but strain contrast images still remain similar. This suggests that the strain contrast images are not related to the (1 1/2 0) diffuse reflections. High resolution electron microscopy was also employed. The results are consistent with the arguments derived from aging experiments.

Initial stage Fe-clustering in the Au–Fe spin-glass system

1992 ◽  
Vol 7 (2) ◽  
pp. 321-328 ◽  
Author(s):  
Chen-Chia Chou ◽  
C.M. Wayman
Keyword(s):  
Electron Microscopy ◽  
Early Stage ◽  
Theoretical Calculations ◽  
High Resolution Electron Microscopy ◽  
Initial State ◽  
Transmission Electron ◽  
Initial Stage ◽  
Fe Content ◽  
Resolution Electron ◽  
Fe Alloys

Aging experiments were conducted to study initial state Fe-clustering in Au–Fe alloys with Fe content from 10.7 to 33%. Information derived from experiments using transmission electron microscopy, electron diffraction, and high resolution electron microscopy suggests the coexistence of short-range-order and Fe-clusters. At early stages of aging, lobe-like and/or rod-shaped strain contrast images, identified as clusters, were revealed after specimens were further cleaned by an ion-miller. The (11/20) special point diffuse reflections were prominent in the as-quenched condition and/or early stage aging, and the intensities decrease gradually as aging proceeds. After a certain period, (11/20) diffuse reflections disappear but strain contrast images still remain similar. This suggests that the strain contrast images are not related to the (11/20) diffuse reflections. The cluster characteristics of Au–Fe alloys are differentiated from those of Al–Cu and Cu–Be based upon theoretical calculations.

High resolution observations of short-range ordering in disordered Au4Mn alloys

1984 ◽  
Vol 42 ◽  
pp. 426-427
Author(s):  
Nobuo Tanaka ◽  
Ken-ichi Ohshima ◽  
Jinpei Harada ◽  
J.M. Cowley
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Diffuse Scattering ◽  
Short Range ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
X Ray ◽  
Direct Observations ◽  
Resolution Electron ◽  
Short Range Ordering

Observation of short range ordered (SRO) state in disordered binary alloys is the interesting topic in the point of order-disorder transition. The observation and analysis have been made with X-ray and neutron diffraction techniques which can give the SRO-parameters. These techniques, however, give only the information of an averaged structure. The ordering process is localized, so direct observations in atomic level by high resolution electron microscopy is needed for the detailed analysis.In the present study, disordered Au4Mn alloys were investigated with high resolution electron microscopy for the analysis of the origin of the characteristic SRO diffuse scattering (Fig. 1). The material was prepared by quenching and thinned by electrolytic polishing for microscopic observations. The specimen was observed along <120> direction by JEOL-200CX electron microscope (E=200keV).

The Early Stages of the Spinel-Alumina Phase Transformation

1987 ◽  
Vol 94 ◽  
Author(s):  
Y. Kouh Simpson ◽  
C. B. Carter
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Early Stage ◽  
Spinel Phase ◽  
High Resolution Electron Microscopy ◽  
Solid State Reactions ◽  
Alumina Phase ◽  
Transmission Electron ◽  
Resolution Electron ◽  
In Situ Experiments

ABSTRACTThe initial stage of topotactic growth of Ni-Al spinel into Al2O3 has been examined using transmission electron microscopy. A new experimental approach to the study of solid-state reactions, which may be adapted for in-situ experiments for low-temperature systems, has been used in this study. In its present form, the technique involves heating a thin film of one oxide in the presence of a vapor of the second oxide. In the study of the growth characteristics of Ni-Al spinel phase, the orientation of the Al2O3 substrate has been found to influence greatly both the structural and morphological aspects of the spinel growth. In particular, the topotactic relationship between the spinel and the alumina are very different for (0001) and {1120} substrate orientations. The very early stage of the kinetics of the spinel growth, in which the length and the width of the spinel particles are only a few hundred angstroms, is illustrated with the results obtained from the re-heating experiments. The structure of the spinel-alumina interface has also been studied using high-resolution electron microscopy. These results are discussed in relation to the different models proposed for the spinel-alumina phase transformation.

Atomic Structure of Alloys Close to Phase Transitions

1999 ◽  
Vol 580 ◽  
Author(s):  
G. Van Tendeloo ◽  
D. Schryvers
Keyword(s):  
Phase Transitions ◽  
Short Range ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Domain Formation ◽  
Ordering Effects ◽  
Resolution Electron ◽  
Short Range Ordering ◽  
Transition Effects ◽  
Martensitic Nucleation

AbstractPhase transitions are often accompanied by pre-transition effects. These effects have been studied on an atomic scale by high resolution electron microscopy. For the diffusion controled phase transitions we discuss short range ordering effects in Ni-Mo and Cu-Pd. For the displacive transitions we discuss the martensitic nucleation in Ni-Al and the nanoscale domain formation in the Ni-Ti R phase.

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.

High Resolution Transmission Electron Microscopy of an automobile catalytic converter

1990 ◽  
Vol 48 (4) ◽  
pp. 242-243
Author(s):  
Jan-Olle Malm ◽  
Jan-Olov Bovin
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Catalytic Converter ◽  
Active Material ◽  
Image Intensifier ◽  
High Resolution Electron Microscopy ◽  
Detailed Knowledge ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Atomic Surface

Understanding of catalytic processes requires detailed knowledge of the catalyst. As heterogeneous catalysis is a surface phenomena the understanding of the atomic surface structure of both the active material and the support material is of utmost importance. This work is a high resolution electron microscopy (HREM) study of different phases found in a used automobile catalytic converter.The high resolution micrographs were obtained with a JEM-4000EX working with a structural resolution better than 0.17 nm and equipped with a Gatan 622 TV-camera with an image intensifier. Some work (e.g. EDS-analysis and diffraction) was done with a JEM-2000FX equipped with a Link AN10000 EDX spectrometer. The catalytic converter in this study has been used under normal driving conditions for several years and has also been poisoned by using leaded fuel. To prepare the sample, parts of the monolith were crushed, dispersed in methanol and a drop of the dispersion was placed on the holey carbon grid.

Ultrastructural Immunocytochemistry of Five Rat Pituitary Adenomas

1980 ◽  
Vol 38 ◽  
pp. 724-725
Author(s):  
D. J. McComb ◽  
N. Ryan ◽  
E. Horvath ◽  
K. Kovacs ◽  
E. Nagy ◽  
...  
Keyword(s):  
Pituitary Adenomas ◽  
Pituitary Tumors ◽  
Electron Microscopic ◽  
Electron Microscopic Immunocytochemistry ◽  
Transmission Electron ◽  
Rat Pituitary ◽  
Radiation Induced ◽  
Group 5 ◽  
Group 2 ◽  
Microscopic Techniques

Conventional light and electron microscopic techniques failed to clarify the cellular composition and derivation of spontaneous and induced, intrasellar and transplanted pituitary adenomas in rats (1). In the present work, electron microscopic immunocytochemistry was applied to evaluate five adenohypo-physial tumors using a technique described by Moriarty and Garner (2). Spontaneously occurring pituitary adenomas (group 1) were harvested from aging female Long-Evans rats. R-Amsterdam rats were treated with 2 x 1.0 mg estrone acetate (HogivaI) s.c. weekly for 6 months. Pituitary adenomas in excess of 30 mg were removed from these animals to make up the tumors of group 2. Groups 3 and 4 consisted of estrogen-induced autonomous transplan¬ted pituitary tumors MtT.WlO and MtT.F4. Group 5 was a radiation-induced transplanted autonomous pituitary tumor MtT.W5. The tumors of groups 3,4 and 5 were allowed to proliferate in host rats 6-8 weeks prior to removal for processing. Tissue was processed for transmission electron microscopy (glutaraldehyde fixation, OsO4 postfixation and epoxy resin embedding), and electron microscopic immunocytochemistry (3% paraformaldehyde fixation and Araldite embedding).

Formation and structure of polymeric carbons

1972 ◽  
Vol 327 (1571) ◽  
pp. 501-517 ◽  
Keyword(s):  
Glassy Carbon ◽  
Molecular Orientation ◽  
Early Stage ◽  
Structural Difference ◽  
Direct Consequence ◽  
High Resolution Electron Microscopy ◽  
Polymer Chains ◽  
Resolution Electron ◽  
Ribbon Structure ◽  
Phenolic Polymer

Glassy carbon has been prepared in the shape of disk and fibre by direct pyrolysis of a phenolic resin. Carbonization studies indicate that the unique structure of the final glassy carbon is a direct consequence of the production of very stable aromatic ribbon molecules by the coalescence of phenolic polymer chains at an early stage of pyrolysis. It is shown that molecular orientation induced in the initial polymer before pyrolysis is 'memorized’ to some extent after carbonization. Molecular orientation imposed in this type of carbon is not an intrinsic structural feature, but a physical characteristic which can be varied by the formation process or by extension at high temperatures; there is no essential structural difference apart from preferred orientation between polymeric units or microfibrils in well-oriented carbon fibres and isotropic glassy carbon. High resolution electron microscopy confirms this directly. We thus identify a new class of ‘polymeric carbons’, that consist of intertwined microfibrils comprising stacks of narrow graphitic ribbons. The fibrils are held together with covalent interfibrillar links of strength lower than that in the ribbons themselves. A ribbon structure has been proposed previously by Ruland (1971) for the specific case of high modulus carbon fibre. The structure is elaborated and extended here to cover all polymeric carbons and the steps in its development during carbonization are decisively detailed.

Transmission electron microscopy observation in a liquid-phase-sintered SiC with oxynitride glass

2001 ◽  
Vol 16 (8) ◽  
pp. 2189-2191 ◽  
Author(s):  
Guo-Dong Zhan ◽  
Mamoru Mitomo ◽  
Young-Wook Kim ◽  
Rong-Jun Xie ◽  
Amiya K Mukherjee
Keyword(s):  
Electron Microscopy ◽  
Liquid Phase ◽  
High Resolution Electron Microscopy ◽  
Nitrogen Atmosphere ◽  
X Ray Diffraction ◽  
Sintering Additive ◽  
Transmission Electron ◽  
High Annealing ◽  
Resolution Electron ◽  
Oxynitride Glass

Using a pure α–SiC starting powder and an oxynitride glass composition from the Y–Mg–Si–Al–O–N system as a sintering additive, a powder mixture was hot-pressed at 1850 °C for 1 h under a pressure of 20 MPa and further annealed at 2000 °C for 4 h in a nitrogen atmosphere of 0.1 MPa. High-resolution electron microscopy and x-ray diffraction studies confirmed that a small amount of β–SiC was observed in the liquid-phase-sintered α–SiC with this oxynitride glass, indicating stability of β–SiC even at high annealing temperature, due to the nitrogen-containing liquid phase.

Structure of InAs Quantum Dots in Si Matrix Investigated by High Resolution Electron Microscopy

1999 ◽  
Vol 571 ◽  
Author(s):  
N. D. Zakharov ◽  
P. Werner ◽  
V. M. Ustinov ◽  
A.R. Kovsh ◽  
G. E. Cirlin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Critical Thickness ◽  
High Resolution Electron Microscopy ◽  
Geometrical Parameters ◽  
Inas Quantum Dots ◽  
Temperature Growth ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTQuantum dot structures containing 2 and 7 layers of small coherent InAs clusters embedded into a Si single crystal matrix were grown by MBE. The structure of these clusters was investigated by high resolution transmission electron microscopy. The crystallographic quality of the structure severely depends on the substrate temperature, growth sequence, and the geometrical parameters of the sample. The investigation demonstrates that Si can incorporate a limited volume of InAs in a form of small coherent clusters about 3 nm in diameter. If the deposited InAs layer exceeds a critical thickness, large dislocated InAs precipitates are formed during Si overgrowth accumulating the excess of InAs.

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