Non-equilibrium phase formation

1990 ◽  
Vol 48 (4) ◽  
pp. 506-507
Author(s):  
Hiroshi Fujita
Keyword(s):  
Electron Irradiation ◽  
Equilibrium Phase ◽  
General Rule ◽  
High Energy ◽  
Atomic Scale ◽  
Irradiation Effect ◽  
In Situ Experiments ◽  
Equilibrium Phases ◽  
Non Equilibrium

The most important advantage of EM’s is in situ experiments on detailed processes of the same phenomena that occur in bulk materials. In recent years, in situ experiments with HVEM’s, in particular with a 3MV ultra-HVEM , has made it possible to create non-equilibrium phases, which do not exist in nature, or to control and design materials on an atomic scale. Namely, HVEM’s have developed to “Micro-Laboratory”, in which various material-treatments can be done, for natural science from powerful tools for characterization and/or identification of materials.l.The General Rule for Solid Amorphization The author and his cowerkers have succeeded in making amorphous solids of intermetallic compounds by high energy electron irradiation. Using the electron irradiation effect, necessary conditions for the formation of both non-equilibrium phases and extremly supersaturated solid structures[3,4] can be easily and precisely controlled.

Radiation-induced disordering and amorphization—An in situ HVEM study of uranium silicide with comparison to natural processes in zirconolite

1990 ◽  
Vol 48 (4) ◽  
pp. 534-535
Author(s):  
R. C. Birtcher ◽  
L. M. Wang ◽  
C. W. Allen ◽  
R. C. Ewing
Keyword(s):  
Electron Irradiation ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
In Situ Tem ◽  
In Situ Experiments

We present here results of in situ TEM diffraction observations of the response of U3Si and U3Si2 when subjected to 1 MeV electron irradiation or to 1.5 MeV Kr ion irradiation, and observations of damage occuring in natural zirconolite. High energy electron irradiation or energetic heavy ion irradiation were performed in situ at the HVEM-Tandem User Facility at Argonne National Laboratory. In this Facility, a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter have been interfaced to a 1.2 MeV AEI high voltage electron microscope. This allows a wide variety of in situ experiments to be performed with simultaneous ion irradiation and conventional transmission electron microscopy. During the electron irradiation, the electron beam was focused to a diameter of about 2 μ.m at the specimen thin area. The ion beam was approximately 2 mm in diameter and was uniform over the entire specimen. With the specimen mounted in a heating holder, the temperature increase indicated by the furnace thermocouple during the ion irradiation was typically 8 °K.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

scholarly journals An In situ TEM study of the surface oxidation of palladium nanocrystals assisted by electron irradiation

Nanoscale ◽  
2017 ◽  
Vol 9 (19) ◽  
pp. 6327-6333 ◽  
Author(s):  
Dejiong Zhang ◽  
Chuanhong Jin ◽  
He Tian ◽  
Yalin Xiong ◽  
Hui Zhang ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Surface Oxidation ◽  
Atomic Scale ◽  
In Situ Tem

An In situ atomic scale study of the surface oxidation of Pd nanocrystals.

Amorphisation Tendency of Intermetallic Compounds Under Electron Irradiation

1986 ◽  
Vol 74 ◽  
Author(s):  
D. E. Luzzi ◽  
M. Meshii
Keyword(s):  
Crystal Structure ◽  
Intermetallic Compounds ◽  
Electron Irradiation ◽  
Alloy System ◽  
Metal Compounds ◽  
Complex Crystal Structure ◽  
In Situ Experiments ◽  
Binary Alloy System ◽  
Disordered Crystal

AbstractThe chemical disordering model for the electron irradiation induced crystalline to amorphous (C-A) transition was previously developed using in-situ experiments in the intermetallic compounds of the Cu-Ti binary alloy system. In the context of this model, a rule was developed which predicts the amorphisation tendency of these and other binary intertransition metal compounds with an accuracy of 92% in the 38 compounds studied to date. Two aspects of this rule, the composition of the compound and the crystal structure are examined through a first approximation computer comparison of ordered, partially ordered, and disordered crystal structures. It is found that in bcc based compounds and in complex crystal structure compounds, the ability of the chemical disordering to raise the energy of the crystal is severely inhibited at compound compositions away from 50:50. During the disordering process, the greatest increase of the crystal energy occurs during the early stages of chemical disordering. These results mesh well with the concept of an amorphous transition driven by the energy increase due to chemical disordering.

In situ HREM of interface interactions

1993 ◽  
Vol 51 ◽  
pp. 830-831
Author(s):  
Robert Sinclair ◽  
Toyohiko J. Konno
Keyword(s):  
Amorphous Material ◽  
Equilibrium Phase ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Interface Reactions ◽  
Diffusion Controlled ◽  
Resolution Electron

We have applied in situ high-resolution electron microscopy (HREM) to the study of interface reactions, particularly in metal-semiconductor systems. There is contrasting behavior whether or not the manufactured interface undergoes a chemical reaction. The in situ technique allows determination of the reaction mechanisms on an atomic scale.Reactive interfaces are characterized by systems in which new chemical compounds are formed (e.g., silicides for metal-silicon interfaces, metal gallides and arsenides for GaAs, etc.). We found that the equilibrium phase formation is often preceded by a solid-state amorphization reaction. In situ observations allow very precise measurement of the reaction rate in a sufficient temperature range to confirm that this process is diffusion controlled. Crystallization of the amorphous material can be followed as well as the development of any crystallographic orientation relationships. A ledge growth mechanism can easily be distinguished from a random process.It might be expected that non-reactive interfaces are stable upon heating.

scholarly journals In Situ Studies of Light Metals with Synchrotron Radiation and Neutrons

2011 ◽  
Vol 690 ◽  
pp. 192-197
Author(s):  
Peter Staron ◽  
Felix Beckmann ◽  
Thomas Lippmann ◽  
Andreas Stark ◽  
Michael Oehring ◽  
...  
Keyword(s):  
High Energy ◽  
High Time Resolution ◽  
Material Research ◽  
Light Metals ◽  
X Rays ◽  
Friction Stir ◽  
Wide Range ◽  
In Situ Experiments

High-energy X-rays and neutrons offer the large penetration depths that are often required for the determination of bulk properties in engineering material research. In addition, new sources provide very high intensities on the sample, which can be used not only for high spatial resolution using very small beams, but also for high time resolution in combination with a fast detector. This opens up possibilities for a wide range of specific engineering in situ experiments. Typical examples that are already widely used are heating or tensile testing in the beam. However, there are also more challenging experiments in the field of light metals, like e.g. friction stir welding, dilatometry, solidification, or cutting. Selected examples are presented.

Fuel-Matrix Chemical Interaction between U-7wt.%Mo Alloy and Mg

2013 ◽  
Vol 333 ◽  
pp. 199-206 ◽  
Author(s):  
K. Huang ◽  
H. Heinrich ◽  
D.D. Keiser ◽  
Yong Ho Sohn
Keyword(s):  
Electron Microscopy ◽  
Focused Ion Beam ◽  
Chemical Interaction ◽  
Ion Beam ◽  
Equilibrium Phase ◽  
Atomic Scale ◽  
Inert Matrix ◽  
Transmission Electron ◽  
Test Reactor

A solid-to-solid, U-7wt.%Mo vs. Mg diffusion couple was assembled and annealed at 550°C for 96 hours. Themicrostructurein the interdiffusion zone and the development of concentration profiles were examined via scanning electron microscopy, transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. A TEM specimen was prepared at the interface between U-7wt.%Mo andMgusing focused ion beam in-situ lift-out. The U-7wt.%Mo alloy was bonded well tothe Mg at the atomic scale, without any evidence of oxidation, cracks or pores.Despite the good bonding, very little or negligible interdiffusion was observed.This is consistent with the expectation based on negligible solubilities according to the equilibrium phase diagrams. Along with other desirableproperties, Mgis a potential inert matrix or barrier materialfor U-Mo fuel alloy systembeing developed forthe Reduced Enrichment for Research and Test Reactor (RERTR) program.

A Modeling Study of Cyclical Phase Transformations

2005 ◽  
Vol 475-479 ◽  
pp. 3081-3086
Author(s):  
Jong K. Lee
Keyword(s):  
Phase Transitions ◽  
Mechanical Alloying ◽  
Phase Transformations ◽  
Molecular Dynamic ◽  
Dynamic Equilibrium ◽  
Equilibrium Phase ◽  
Two Dimensional ◽  
Lennard Jones ◽  
Equilibrium Phases ◽  
Non Equilibrium

Recent work has shown evidence of cyclical phase transformations taking place during mechanical alloying. Cyclical phase transformations resemble dynamic equilibrium in the sense that both equilibrium and non-equilibrium phases are simultaneously present during milling, but phase fractions vary during cyclical transformations. A brief thermodynamic and kinetic account is first discussed to establish the criteria for cyclical transformations. A two-dimensional molecular dynamic work is then presented to demonstrate cyclical phase transitions between an equilibrium and a non-equilibrium phase during mechanical alloying. A model binary crystal made of 57 Lennard-Jones atoms is studied to illustrate cyclical transitions between an equilibrium rhombus and a non-equilibrium square phase.

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