Microstructure and Homogeneity of Nanocrystalline Co–Cu Supersaturated Solid Solutions Prepared by Mechanical Alloying

1997 ◽  
Vol 12 (4) ◽  
pp. 936-946 ◽  
Author(s):  
J. Y. Huang ◽  
Y. D. Yu ◽  
Y. K. Wu ◽  
D. X. Li ◽  
H. Q. Ye
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Solid Solutions ◽  
High Resolution Electron Microscopy ◽  
Face Centered Cubic ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Supersaturated Solid Solutions ◽  
Face Centered ◽  
Fcc Phase

Mechanical alloying (MA) has been performed in the CoxCu(100-x) (x = 10, 25, 50, 60, 75, and 90) system. High resolution electron microscopy (HREM) and field emission gun transmission electron microscopy (FEG TEM) were used to characterize the microstructure and homogeneity of the nanocrystalline Co25Cu75 solid solution. After 20 h of MA, all the mixtures show an entirely face-centered cubic (fcc) phase. HREM shows that the ultrafine-grained (UFG) materials prepared by MA contain a high density of defects. Two kinds of typical defects in UFG Co25Cu75 are deformation twins and dislocations. The dislocations are mostly 60° type, and in many cases they dissociate into 30° and 90° partials. The grain boundaries are ordered in structure, curved, and slightly strained, which is similar to that observed in NC–Pd. Nanoscale energy dispersive x-ray spectroscopy (EDXS) shows that the Co concentration in both the interior of grains and the GB's is close to the global composition, which proves that supersaturated solid solutions are indeed formed. In the meantime EDXS revealed that the mixing of Co and Cu in the solid solutions is homogeneous at nanometer scale. MA in the Co–Cu system is suggested to be a diffusion-controlled process, and stress-stimulated diffusion is proposed to be the reason for the formation of supersaturated solid solutions in this immiscible system.

Synthesis of Nanocrystalline Ag-Cu Supersaturated Solid Solution by Mechanical Alloying

2010 ◽  
Vol 92 ◽  
pp. 271-276 ◽  
Author(s):  
Liang Feng Li ◽  
Tai Qiu ◽  
Jian Yang ◽  
Yong Bao Feng
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Mechanical Alloying ◽  
Solid Solutions ◽  
Supersaturated Solid Solution ◽  
Main Peak ◽  
Rich Phase ◽  
Transmission Electron ◽  
Supersaturated Solid Solutions ◽  
Xrd Patterns

Nanocrystalline Ag-28Cu supersaturated solid solution is prepared by mechanical alloying (MA) using a planetary ball mill. The mechanical alloyed powders are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and differential scanning calorimeter (DSC). XRD patterns show that the main peak of Ag-28Cu supersaturated solid solution exists at about 2θ=39° when the milling time is 30h. HRTEM images show that the grain sizes of as-prepared solid solutions have distributions from 10nm to 15nm. The interplanar spacing of (111) plane for fcc Ag-28Cu supersaturated solid solution is about 2.24Å. DSC measurement result indicates that the melting temperature of Ag-28Cu supersaturated solid solution is 783.8°C. The Ag(Cu) supersaturated solid solutions are in metastable state and they will be transformed into Ag-rich phase and Cu-rich phase simultaneously by annealing at 215°C- 415°C.

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.

scholarly journals The Examination of Calcium ion Implanted Alumina with Energy Filtered Transmission Electron Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 413-414
Author(s):  
E.M. Hunt ◽  
J.M. Hampikian ◽  
N.D. Evans
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Pure Aluminum ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Knoop Microhardness ◽  
Aluminum Nanocrystals ◽  
Face Centered

Ion implantation can be used to alter the optical response of insulators through the formation of embedded nano-sized particles. Single crystal alumina has been implanted at ambient temperature with 50 keV Ca+ to a fluence of 5 x 1016 ions/cm2. Ion channeling, Knoop microhardness measurements, and transmission electron microscopy (TEM) indicate that the alumina surface layer was amorphized by the implant. TEM also revealed nano-sized crystals ≈7 - 8 nm in diameter as seen in Figure 1. These nanocrystals are randomly oriented, and exhibit a face-centered cubic structure (FCC) with a lattice parameter of 0.409 nm ± 0.002 nm. The similarity between this crystallography and that of pure aluminum (which is FCC with a lattice parameter of 0.404 nm) suggests that they are metallic aluminum nanocrystals with a slightly dilated lattice parameter, possibly due to the incorporation of a small amount of calcium.Energy-filtered transmission electron microscopy (EFTEM) provides an avenue by which to confirm the metallic nature of the aluminum involved in the nanocrystals.

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.

Silicon-Sapphire Interface: A High Resolution Electron Microscopy Study

1980 ◽  
Vol 2 ◽  
Author(s):  
Fernando A. Ponce
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Silicon Layer ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Resolution Limit ◽  
High Concentration ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTThe structure of the silicon-sapphire interface of CVD silicon on a (1102) sapphire substrate has been studied in crøss section by high resolution transmission electron microscopy. Multibeam images of the interface region have been obtained where both the silicon and sapphire lattices are directly resolved. The interface is observed to be planar and abrupt to the instrument resolution limit of 3 Å. No interfacial phase is evident. Defects are inhomogeneously distributed at the interface: relatively defect-free regions are observed in the silicon layer in addition to regions with high concentration of defects.

Interface structure of face-centered-cubic-Ti thin film grown on 6H–SiC substrate

2000 ◽  
Vol 15 (10) ◽  
pp. 2121-2124 ◽  
Author(s):  
Y. Sugawara ◽  
N. Shibata ◽  
S. Hara ◽  
Y. Ikuhara
Keyword(s):  
Thin Film ◽  
Orientation Relationship ◽  
High Resolution Electron Microscopy ◽  
Electron Beam Evaporation ◽  
Face Centered Cubic ◽  
High Adhesion ◽  
Resolution Electron ◽  
Face Centered ◽  
Relationship Of ◽  
High Degree

A titanium thin film was deposited on the flat (0001) face of a 6H–SiC by electron beam evaporation at room temperature in a vacuum of 5.1 × 10−8 Pa. The Ti film was epitaxially grown on the surface, and the interface between Ti and SiC was characterized by high-resolution electron microscopy. It was found that the structure of the deposited titanium is face-centered cubic (fcc), although bulk titanium metal usually has a hexagonal close-packed or body-centered cubic crystal structure. We believe that the unusual fcc structure of Ti thin film is due to the high adhesion of the film to the substrate and the high degree of coherency between them. The orientation relationship of the fcc-Ti/6H–SiC interface was (111)fcc-Ti//(0001)6H–SiC and [110]fcc-Ti//[1120]6H−SiC. Preliminary calculations indicate that this orientation relationship maximizes the lattice coherency across the interface.

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.

Phase Diagram Determination For Modifications Of The D Phase In The Al-AlCo-AINi System

1998 ◽  
Vol 553 ◽  
Author(s):  
R. Lück ◽  
M. Scheffer ◽  
T. Gödecke ◽  
S. Ritschj ◽  
C. Beelif
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Liquidus Projection ◽  
High Resolution Electron Microscopy ◽  
Reaction Scheme ◽  
Decagonal Phase ◽  
Transmission Electron ◽  
Resolution Electron ◽  
In Situ Experiments ◽  
Projection Surface

AbstractAn extensive investigation into the At-AICo-AlNi ternary subsystem is presented. Observations have used the techniques of differential thermal analysis, magnetothermal analysis, dilatometry, metallography, X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy. Representative graphic documentation, as liquidus projection surface, isothermal sections, temperature-concentration section, and reaction scheme are presented. 11 phases from the binaries Al-Co and Al-Ni and the three ternary phases Y2 (Co2NiAl9), X and the decagonal phase D were found at room temperature. The decagonal phase is formed from the melt peritectically via a critical tie line and its primary formation area dominates at the liquidus projection surface. 45 three-phase regions are present according to the reaction scheme.Several phase variants in the area of the decagonal phase were detected by transmission electron microscopy. Phase fields of the variants were determined from samples quenched from their respective temperatures. In-situ experiments on transformations of variants were performed by dilatometric measurements. The subdivision of the D phase area into the fields of the variants is discussed.

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