scholarly journals The type identification of dislocation loops by TEM and the loop formation in pure Fe implanted with H+*

2011 ◽  
Vol 60 (3) ◽  
pp. 036802
Author(s):  
Huang Yi-Na ◽  
Wan Fa-Rong ◽  
Jiao Zhi-Jie
Keyword(s):  
Dislocation Loops ◽  
Loop Formation

Point Defect Absorption and Dislocation Loop Formation at Grain Boundaries in Hvem-Irradiated Zr and Its Alloys:1. Influence of Solute Addition

1985 ◽  
Vol 43 ◽  
pp. 350-351
Author(s):  
R.A. Herring ◽  
M. Griffiths ◽  
M.H Loretto ◽  
R.E. Smallman
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Point Defect ◽  
Reactor Core ◽  
Solute Concentration ◽  
Nuclear Industry ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Component Material ◽  
Impurity Interaction

Because Zr is used in the nuclear industry to sheath fuel and as structural component material within the reactor core, it is important to understand Zr's point defect properties. In the present work point defect-impurity interaction has been assessed by measuring the influence of grain boundaries on the width of the zone denuded of dislocation loops in a series of irradiated Zr alloys. Electropolished Zr and its alloys have been irradiated using an AEI EM7 HVEM at 1 MeV, ∼675 K and ∼10-6 torr vacuum pressure. During some HVEM irradiations it has been seen that there is a difference in the loop nucleation and growth behaviour adjacent to the grain boundary as compared with the mid-grain region. The width of the region influenced by the presence of the grain boundary should be a function of the irradiation temperature, dose rate, solute concentration and crystallographic orientation.

Effect of Formation and Growth of Dislocation Loops and Cavities on Low-Temperature Swelling of Irradiated Uranium-Molybdenum Alloys

1998 ◽  
Vol 540 ◽  
Author(s):  
J. Rest ◽  
G. L. Hofman ◽  
I. I. Konovalov ◽  
A. A. Maslov
Keyword(s):  
Low Temperature ◽  
Rate Theory ◽  
Subgrain Structure ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Molybdenum Alloys ◽  
Fission Gas ◽  
Swelling Mechanism ◽  
Test Reactor ◽  
Low Irradiation

AbstractScanning electron photomicrographs of U–10 wt.% Mo irradiated at low temperature in the Advanced Test Reactor (ATR) to about 40 at.% burnup show the presence of cavities. We have used a rate-theory-based model to investigate the nucleation and growth of cavities during low-temperature irradiation of uranium-molybdenum alloys in the presence of irradiation-induced interstitial-loop formation and growth. Our calculations indicate that the swelling mechanism in the U–10 wt.% Mo alloy at low irradiation temperatures is fission-gas driven. The calculations also indicate that the observed bubbles must be associated with a subgrain structure. Calculated bubble-size-distributions are compared with irradiation data.

The Effect of a Thin Sample on the Extended Defect Evolution in Si+ Implanted Si

1997 ◽  
Vol 490 ◽  
Author(s):  
Jing-Hong Li ◽  
Kevin S. Jones
Keyword(s):  
Dislocation Loop ◽  
Ex Situ ◽  
Dissolution Process ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Thin Sample ◽  
Extended Defect ◽  
Defect Evolution ◽  
Annealing Study

ABSTRACTThe annealing kinetics of implant damage in Si+ implanted Si has been investigated using in-situ and ex-situ annealing of transmission electron microscopy (TEM) samples prepared prior to annealing. The defect evolution at 800°C was studied for a Si wafer implanted with Si+ at 100keV to a dose of 2×1014 cm-2. This implant was above the sub-threshold loop formation threshold allowing one to study simultaneously the {311} defect dissolution and dislocation loop nucleation and growth. In order to study the effect on the defect evolution of using a thin sample for an in-situ annealing experiment, a pair of samples, one thick and one thinned into a TEM sample, were annealed in a furnace simultaneously. It was found that the presence of a second surface 2000Å below the implant damage did not affect the extended defect evolution. For the in-situ annealing study it was found that the {311} dissolution process and sub-threshold dislocation loop formation process was not affected by the TEM electron beam at 160kV as long as an 800°C furnace pre-anneal was done prior to in-situ annealing. The dissolution rate of the {311} defects was used to confirm the TEM holder furnace temperature. The results of both the in-situ the {311} defects is released during the 311 dissolution process and 30% comes to reside in dislocation loops. Thus, the loops appear to contain a significant fraction of the total interstitial concentration introduced by the implant.

A study on sink strength of dislocations through analyses of loop formation process under defect concentration gradient

1990 ◽  
Vol 48 (4) ◽  
pp. 528-529
Author(s):  
Kiyomichi Nakai ◽  
Chiken Kinoshita
Keyword(s):  
Void Formation ◽  
Nucleation And Growth ◽  
Dark Field ◽  
Sink Strength ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Dark Field Microscopy ◽  
Zr Alloy

The behavior of point defects around sinks has been greatly investigated for evaluating their bias effects on void formation and swelling. It is, however, laborious to estimate sink strength connected with the bias, because it depends greatly on the sink character. In the present paper the sink strength for interstitials is confirmed through analyses of nucleation and growth process of dislocation loops around characterized dislocations under electron irradiation.A Nb-40.0wt.%Zr alloy having the interface between bcc structures of βNb and βZr phases was irradiated with 1MeV electrons in the JEM-1000 high-voltage electron microscope at the HVEM Laboratory, Kyushu University.The orientation relationship between βNb and βZr phases follows the cube/cube, and the interfaces are. The interface dislocations run parallel to [111] and at a regular interval and respectively have Burgers vectors of b = 1/2 and 1/2[111]. Misfit between the phases as well as distance between interface dislocations are also confirmed by dark-field microscopy, trace analysis and electron diffraction.

Elucidating “screw dislocation”-driven film formation of sodium thiosulphate with complex hierarchical molecular assembly

2017 ◽  
Vol 204 ◽  
pp. 251-269 ◽  
Author(s):  
Deepak Dwivedi ◽  
Katerina Lepkova ◽  
Thomas Becker ◽  
Matthew R. Rowles
Keyword(s):  
Screw Dislocation ◽  
Materials Science ◽  
Chemical Elements ◽  
Film Formation ◽  
Hierarchical Structures ◽  
Molecular Assembly ◽  
Surface Films ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Sodium Thiosulphate

Sodium thiosulphate (Na2S2O3) films were synthesized on carbon steel substrates through solution deposition, and a film formation growth mechanism is delineated in detail herein. Dislocation-driven film formation took place at the lower concentration of Na2S2O3 (0.1 M) studied, where screw dislocation loops were identified. Interestingly, we observed the co-existence of screw dislocation spiral loops and hierarchically-ordered molecular assembly in the film, and showed the importance of hierarchical morphology in the origin of screw dislocation. The screw dislocation loops were, however, distorted at the higher studied concentration of Na2S2O3 (0.5 M), and no hierarchical structures were formed. The mechanisms of film formation are discussed in detail and provide new insights into our understanding regarding morphology of the hierarchical molecular assembly, screw dislocation loop formation, and the role of chemical elements for their development. The main crystalline and amorphous phases in the surface films were identified as pyrite/mackinawite and magnetite. As sodium thiosulphate is widely used for energy, corrosion inhibition, nanoparticle synthesis and catalysis applications, the knowledge generated in this study is applicable to the fields of corrosion, materials science, materials chemistry and metallurgy.

〈100〉 Dislocation Loop Formation and Characterization in Ferritic Materials: Comparison between Experiments and Modeling

2002 ◽  
Vol 731 ◽  
Author(s):  
Jaime Marian ◽  
Brian D. Wirth ◽  
Robin Schäublin ◽  
J. Manuel Perlado
Keyword(s):  
Atomistic Simulation ◽  
Damage Accumulation ◽  
Atomistic Simulations ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Transmission Electron ◽  
Mechanisms Of Formation ◽  
Fusion Applications ◽  
Modeling And Experiments ◽  
Dynamics Simulations

AbstractTransmission electron microscopy (TEM) observation of irradiated ferritic materials reveals the existence of large, interstitial dislocation loops with Burgers vectors ½ 〈111〉 and 〈100〉. These loops cause hardening of the material by pinning dislocations and impeding their glide during deformation. However, numerous molecular dynamics simulations of collision cascades in α-Fe have evidenced the exclusive formation of small, highly mobile, ½ 〈111〉 clusters. Additionally, continuum dislocation theory and atomistic simulations have shown that ½ 〈111〉 loops are energetically favored. This introduces the need to explain the mechanisms of formation and growth of 〈100〉 loops from small, cascade-produced clusters. The understanding of the physics underlying these phenomena is important for the development of solid damage accumulation models in ferritic materials that are being considered for fusion applications. In this work we propose a comprehensive set of dislocation reactions that explain the nucleation of 〈100〉 loops from ½ 〈111〉 clusters. The growth up to TEM visible sizes of 〈100〉 loops through absorption of one-dimensionally migrating ½ 〈111〉 clusters is also assessed. Finally, a direct comparison of TEM experimental micrographs with atomistic simulation-derived images is presented to show an example of how to help close the gap that exists between modeling and experiments.

The heterogeneous nucleation of tetrahedra in quenched gold

1970 ◽  
Vol 315 (1521) ◽  
pp. 231-238 ◽  
Keyword(s):  
Electron Microscopy ◽  
Carbon Monoxide ◽  
Heterogeneous Nucleation ◽  
Defect Structure ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Aqua Regia ◽  
Reducing Atmosphere ◽  
High Impurity ◽  
Defect Densities

The influence of copper, magnesium, and aluminium impurities on the defect structure of quenched gold has been studied by electron microscopy. Additions of 200/10 6 of magnesium or 150/10 6 of aluminium increase the tetrahedra density, but up to 1500/10 6 of copper have no effect. With 500/10 6 of magnesium, dislocation loops nucleate in place of tetrahedra. The effectiveness of impurities in promoting heterogeneous nucleation is thus found to depend on their valency. These results may be accounted for by a model in which divacancy-impurity atom interactions lead to increased tetravacancy formation, because of enhanced combina­tion of free and trapped divacancies. This model also accounts for loop formation at high impurity concentrations. Defect densities are reported for gold annealed before quenching in air, carbon monoxide, or hydrogen. The model suggests that the high densities observed after quenching from a reducing atmosphere are due to interstitial hydrogen, and this was confirmed by producing high densities in gold etched in aqua regia immediately after quenching.

scholarly journals Production of Defects in Metals by Collision Cascades: Tem Experiments

1994 ◽  
Vol 373 ◽  
Author(s):  
M. A. Kirk
Keyword(s):  
Low Energy ◽  
Recoil Energy ◽  
Dislocation Loops ◽  
Phonon Coupling ◽  
Loop Formation ◽  
Electron Phonon Coupling ◽  
Fast Neutron Irradiation ◽  
Dilute Alloy ◽  
Specific Metal

AbstractI will review our experimental TEM data on the production of dislocation loops by low energy ion bombardment to low doses, as simulations of similar collision cascades produced by fast neutron irradiation, in various metals and alloys. The dependence of vacancy dislocation loop formation on recoil energy, sample temperature, and specific metal or alloy will be examined. Special emphasis will be placed on the effects of dilute alloy additions. A model for cascade melting will be employed to understand these effects, and will require an examination of the role of electron-phonon coupling in cascade cooling and recrystallization. The formation of interstitial dislocation loops as cascade defects, and the influence of the nearby surfaces in these experiments will be briefly discussed.

Correlation of Dislocation Loop Formation and Time Dependent Diffusion of Implanted P-type Dopants in Gallium Arsenide

1991 ◽  
Vol 240 ◽  
Author(s):  
H. G. Robinson ◽  
M. D. Deal ◽  
D. A. Stevenson ◽  
K. S. Jones
Keyword(s):  
Gallium Arsenide ◽  
Time Dependence ◽  
Point Defect ◽  
Dislocation Loop ◽  
Time Dependent ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Interstitial Diffusion ◽  
Order Of Magnitude ◽  
P Type

ABSTRACTRecent experimental results indicate that diffusion of implanted p-type dopants in GaAs is time dependent under certain conditions. For Mg implanted at a dose of 1 × 1014 cm−2, the diffusion is constant for approximately an hour, then decreases by an order of magnitude or more. Be implanted at 1 × 1013 and 1 ×1014 cm−2 exhibits similar behavior, but with a shorter time before the diffusivity decreases. The diffusivity in 1 × 1013 Mg cm−2 implants, in contrast, remains constant for up to 16 hours. TEM micrographs of Be and Mg implants reveal dislocation loops in the higher dose samples, but not in the lower dose ones. During annealing, the loops grow and decrease in density, eventually disappearing completely from the crystal. This annealing of the loops appears to correlate to the time dependence of the diffusion. This behavior can be explained in terms of the substitutional-interstitial diffusion (SID) mechanism and point defect equilibria.

Trapping of Interstitials During Ion Implantation In Silicon

1985 ◽  
Vol 51 ◽  
Author(s):  
R.J. Culbertson ◽  
S.J. Pennycook
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Solid Phase ◽  
Tracer Diffusion ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Group V ◽  
Interstitial Concentration ◽  
Implantation Process ◽  
Dopant Atoms

ABSTRACTThe solid phase epitaxial regrowth of silicon implanted with a group V dopant, such as antimony, results in excellent incorporation of the dopant atoms into silicon lattice sites. However, annealing at higher temperatures or longer times results in transient dopant precipitation with a diffusion coefficient up to five orders of magnitude above that of tracer diffusion and with a reduced activation energy.This precipitation is accompanied by the nucleation of dislocation loops that are interstitial in nature, and the transient ceases as the dislocation loops develop. It is believed that Si interstitials are trapped in a stable defect complex during the implantation process.Although they survive SPE these complexes dissolve at higher temperatures and release a large supply of interstitials which serve to promote dopant migration via an interstitialcy mechanism until they condense to form the observed dislocation loops. By following the Sb implantation with an implantation of B to an equivalent concentration profile the loop formation is efficiently suppressed. For higher B concentrations the Sb precipitation is no longer observed. Results for As implantation are similar to Sb except that As precipitates can not be directly observed. Calculations of the dopant and interstitial concentration depth distributions were also performed.

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