Ordering in Ni4Mo by TEM and APFIM

1987 ◽  
Vol 45 ◽  
pp. 214-215
Author(s):  
E.A. Kenik ◽  
T.A. Zagula ◽  
M.K. Miller ◽  
J. Bentley
Keyword(s):  
Electron Irradiation ◽  
Low Temperatures ◽  
Short Range ◽  
Atom Probe ◽  
Range Order ◽  
Considerable Time ◽  
Probe Field ◽  
Disordered Phase ◽  
Transmission Electron ◽  
Diffraction Patterns

The state of long-range order (LRO) and short-range order (SRO) in Ni4Mo has been a topic of interest for a considerable time (see Brooks et al.). The SRO is often referred to as 1½0 order from the apparent position of the diffuse maxima in diffraction patterns, which differs from the positions of the LRO (D1a) structure. Various studies have shown that a fully disordered state cannot be retained by quenching, as the atomic arrangements responsible for the 1½0 maxima are present at temperatures above the critical ordering temperature for LRO. Over 20 studies have attempted to identify the atomic arrangements associated with this state of order. A variety of models have been proposed, but no consensus has been reached. It has also been shown that 1 MeV electron irradiation at low temperatures (∼100 K) can produce the disordered phase in Ni4Mo. Transmission electron microscopy (TEM), atom probe field ion microscopy (APFIM), and electron irradiation disordering have been applied in the current study to further the understanding of the ordering processes in Ni4Mo.

Short-range order in amorphous co-sputtered Ta-Al thin films

1986 ◽  
Vol 44 ◽  
pp. 860-861
Author(s):  
J.C. Barry ◽  
R.S. Timsit ◽  
D. Landheer
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electron Microscope ◽  
High Resolution ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Transmission Electron ◽  
Thin Film Resistors ◽  
Diffraction Patterns

Tantalum-aluminium thin films have assumed considerable technological importance since the discovery in the late 1960's that the films are useful in the fabrication of thin film resistors and capacitors. It is generally claimed that these films, when prepared by co-sputtering Ta and Al, are amorphous over a range of Ta concentrations extending approximately from 15 to 75 at%, and are crystalline beyond this range. Diffuse electron diffraction patterns and ‘mottle pattern’ transmission electron micrographs are typical characteristics of the amorphous phase. In this present study we have attempted to identify any atomic short range order in the amorphous Ta-Al films and to follow the changes in this order as the Ta concentration increases across the amorphous/crystalline transition. The co-sputtered Ta-Al films of ≈100A thickness were examined in a high resolution 4000EX electron microscope (top entry, ±15°(x,y) tilt, Cs = 1.0mm ) at 400kV.

Short-Range Order and Nanocrystallization in Amorphous Zr-Ti-Cu-Ni-Al

1999 ◽  
Vol 580 ◽  
Author(s):  
L. Q. Xing ◽  
Xiaofeng Gu ◽  
T. A. Lusby ◽  
A. J. Melmed ◽  
T. C. Hufnagel
Keyword(s):  
Amorphous Alloys ◽  
Short Range ◽  
Short Range Order ◽  
Structural Changes ◽  
Range Order ◽  
Transmission Electron ◽  
Microscope Images ◽  
Diffraction Patterns ◽  
Kinetics Of ◽  
Ti Content

AbstractWe have examined the effect of Ti content on the crystallization kinetics of Zr-based amorphous alloys. In Zr59Ti3Cu20Ni8Al10, annealing above the glass transition temperature produces 50-100 nm crystalline precipitates, as seen in transmission electron microscope images. In contrast, TEM images and diffraction patterns from annealed Zr54.5Ti7.5Cu20Ni8Al10 show no evidence of crystalline phase formation. Structural changes upon annealing do occur in this alloy, however, as revealed by field ion microscopy. The effect of Ti is to favor the formation of clusters of short-range order; this tendency for clustering is apparently the cause of difference in crystallization behavior between the two alloys.

High-resolution x-ray imaging of small copper-rich precipitates in steels

1988 ◽  
Vol 46 ◽  
pp. 528-529
Author(s):  
J. R. Michael ◽  
K. A. Taylor
Keyword(s):  
Electron Microscopy ◽  
Thermomechanical Processing ◽  
Atom Probe ◽  
Ferrite Matrix ◽  
Scanning Transmission Electron Microscope ◽  
Probe Field ◽  
X Ray ◽  
Subsequent Transformation ◽  
Transmission Electron ◽  
Scanning Transmission

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.

scholarly journals Atomic Self-ordering in Heteroepitaxially Grown Semiconductor Quantum Dots due to Relaxation of External Lattice Mismatch Strains

2001 ◽  
Vol 696 ◽  
Author(s):  
Peter Möck ◽  
Teya Topuria ◽  
Nigel D. Browning ◽  
Robin J. Nicholas ◽  
Roger G. Booker
Keyword(s):  
Quantum Dots ◽  
Low Temperatures ◽  
Short Range ◽  
Lattice Mismatch ◽  
Life Time ◽  
Semiconductor Quantum Dots ◽  
Quantum Dot Lasers ◽  
Atomic Order ◽  
Transmission Electron ◽  
Gaas Quantum Dot

AbstractThermodynamic arguments are presented for the formation of atomic order in heteroepitaxially grown semiconductor quantum dots. From thermodynamics several significant properties of these systems can be derived, such as an enhanced critical temperature of the disorder-order transition, the possible co-existence of differently ordered domains of varying size and orientation, the possible existence of structures that have not been observed before in semiconductors, the occurrence of atomic order over time, and the occurrence of short range order when the growth proceeds at low temperatures. Transmission electron microscopy results support these predictions. Finally, we speculate on the cause for the observed increase in life time of (In,Ga)As/GaAs quantum dot lasers [H-Y. Liu et al., Appl. Phys. Lett. 79, 2868 (2001)].

Structural Properties of Amorphous Silicon Produced by Electron Irradiation

1999 ◽  
Vol 557 ◽  
Author(s):  
J. Yamasaki ◽  
S. Takeda
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Distribution Function ◽  
Structural Properties ◽  
Electron Irradiation ◽  
Low Temperatures ◽  
Crystalline Silicon ◽  
Transmission Electron ◽  
Amorphous Si ◽  
Means Of Transmission

AbstractThe structural properties of the amorphous Si (a-Si), which was created from crystalline silicon by 2 MeV electron irradiation at low temperatures about 25 K, are examined in detail by means of transmission electron microscopy and transmission electron diffraction. The peak positions in the radial distribution function (RDF) of the a-Si correspond well to those of a-Si fabricated by other techniques. The electron-irradiation-induced a-Si returns to crystalline Si after annealing at 550°C.

Microstructural Characterization of Rapidly Solidified Ultrahigh Strength Aluminum Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 98-99
Author(s):  
D. H. Ping ◽  
K. Hono ◽  
A. Inoue
Keyword(s):  
Rapid Solidification ◽  
Microstructural Characterization ◽  
Atom Probe ◽  
Probe Field ◽  
Amorphous Phases ◽  
Ultrahigh Strength ◽  
Icosahedral Phases ◽  
Transmission Electron ◽  
Solidification Processes ◽  
Rapidly Solidified

Recently, Inoue et al. succeeded in fabricating ultrahigh-strength Al-based alloys consisting of a nanoscale mixture of α-Al and amorphous phases or a mixture of a-Al, amorphous and icosahedral phases in Al-TM-Ce, Al-TM-Ln (TM: transition metals) and Al-Cr-Co-Ce systems by rapid solidification [1-3]. In order to understand the mechanism of the nanoscale microstructural evolution during the rapid solidification processes in these nanocomposite alloys, we have characterized the microstructures of rapidly solidified Al94.5Cr3Co1.5Ce1 and Al96V4Fe2 alloys by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HREM).TEM investigations have revealed that the as-quenched Al94.5Cr3Co1.5Ce1 alloy is composed of a nanoscale mixture of amorphous and α-Al. A typical TEM bright field micrograph is shown in Fig. 1. The microdiffraction patterns taken at various locations in the darkly contrasted region have shown that the region consists of a few interconnected α-Al grains and many localized amorphous regions which are trapped within the Al grains.

Crystalline to Amorphous Transformation of Fe3B By 1 MeV Electron Irradiation

1981 ◽  
Vol 7 ◽  
Author(s):  
A. Mogro-Campero ◽  
E.L. Hall ◽  
J.L. Walter ◽  
A.J. Ratkowski
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Electron Irradiation ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Rapid Quenching ◽  
Al Alloy ◽  
Bright Field ◽  
Transmission Electron ◽  
Diffraction Patterns

ABSTRACTSpecimens of amorphous Fe75B25 produced by rapid quenching from the melt were annealed to complete crystallization and subjected to 1 MeV electron irradiation in a transmission electron microscope at room temperature and at 130 K. The irradiation was interrupted at various intervals in order to obtain bright field images and diffraction patterns. The Fe3B crystals did not become amorphous at room temperature, even after damage levels of several dpa, whereas at 130 K the crystalline to amorphous transformation was observed to be complete at damage levels below 1 dpa. The results are combined with those of ion irradiation work on Fe3B; qualitative agreement is found between Fe3B and previous work on the Zr3Al alloy concerning their response to displacement damage by electron and ion irradiation.

Kinetics of Short Range Order Formation in Au-Pd under 3 MeV Electron Irradiation

1991 ◽  
Vol 66-69 ◽  
pp. 527-532
Author(s):  
A. Bartels ◽  
D. Bartusel ◽  
K. Lücke ◽  
F. Schwarzer
Keyword(s):  
Electron Irradiation ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Kinetics Of
Sign in / Sign up

Export Citation Format

Share Document