Radiation-induced amorphization of intermetallic compounds

1989 ◽  
Vol 47 ◽  
pp. 650-651
Author(s):  
P. R. Okamoto
Keyword(s):  
Intermetallic Compounds ◽  
Brillouin Scattering ◽  
Voltage Electron ◽  
Glass Transformation ◽  
Progressive Loss ◽  
Fundamental Understanding ◽  
Ordered Intermetallic ◽  
Radiation Induced

Many ordered intermetallic compounds become amorphous when irradiated at low temperatures with energetic particles. There is still no fundamental understanding of why some compounds but not others are susceptible to amorphization. However, recent studies indicate that a progressive loss of chemical long-range order (LRO) is a necessary, though not a sufficient condition for the crystal-to-glass transformation. To shed further light on the role of chemical disordering, our work has focused on correlating the structural effects of chemical disorder on the shear modulus of a number of LI2, B2, and A-15 type intermetallic compounds under irradiation conditions where some become amorphous and others remain crystalline.The Brillouin scattering technique was used to measure the change in the velocity of sound (Vs) relative to that of the unirradiated state (Vos) in Zr3Al, FeAl, FeTi, NiAl, and Nb3Ir during irradiation at 298 K with 1-MeV Kr+ ions. The corresponding changes in the Bragg-Williams LRO parameter (S/So), and lattice expansion (Δa/ao) were measured by means of electron diffracting during in-situ irradiation with 1-MeV Kr in the ANL high voltage electron microscope.

Defect clusters of molybdenum alloys bombarded by HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 402-403
Author(s):  
N. Igata ◽  
A. Kohyama ◽  
H. Murakami ◽  
K. Itadani ◽  
H. Tsunakawa
Keyword(s):  
Incident Beam ◽  
In Situ Observation ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Voltage Electron ◽  
Molybdenum Alloys ◽  
Damage Process ◽  
Hot Rolled

As a simulation study of heavy radiation damage by neutrons, in-situ observation of damage process in molybdenum alloys was performed by a high voltage electron microscope. The objectives of this study are to clarify the processes of defect cluster nucleation and growth, and the role of alloying elements on these in the temperature range from 300K to 1300K.The used molybdenum alloys were Mo-(150-1000)at.ppm.C, Mo-(0.06-0.6)at.%Nb, MO-0.29at.%Hf, MO-(0.026-26)at.%Re and Mo-0.56at.%Ni. The used materials were electron-beam melted and hot rolled at 200-400°C and annealing was performed in the vacuum of l×l0-7torr. at 1800°C for 1.0 hr. The standard irradiation conditions were as follows,Accelerating voltage: 1250KV, Beam intensity: l-6×l019 e/cm2 sec, Incident beam direction: <100>, g-vector: {110},The density of defect clusters was determined by the thickness gradient method.The logarithmic density of interstitial dislocation loops, logNi, increased with the reciprocal irradiation temperature, 1/T. The relation between logNiand 1/T was divided into two Arrhenius type relations above and below 500K.

scholarly journals Irradiation-Induced Amorphization and Elastic Shear Instability in Intermetallic Compounds

1989 ◽  
Vol 157 ◽  
Author(s):  
J. Koike ◽  
P. R. Okamoto ◽  
L. E. Rehn ◽  
R. Bhadra ◽  
M. H. Grimsditch ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Structural Information ◽  
Brillouin Scattering ◽  
Shear Instability ◽  
Crystalline Lattice ◽  
Tandem Accelerator ◽  
Voltage Electron ◽  
Elastic Shear ◽  
State Amorphization

ABSTRACTPreviously we reported a substantial (∼ 50 %) decrease in shear modulus prior to amorphization in Kr irradiated Zr3Al, and proposed that amorphization is triggered when the crystalline lattice becomes unstable against shear stress. In the present work, the relation between amorphization and shear elastic instability has been investigated in two additional compounds (FeTi and NiAl) during room temperature irradiation with 1.7-MeV Kr+. A shear modulus was measured using Brillouin scattering; structural information was obtained in situ in a high voltage electron microscope interfaced to a tandem accelerator.During irradiation of FeTi, chemical disordering and a large (∼40 %) decrease of shear modulus were observed, and an amorphous phase developed subsequently. In contrast, NiAl remained crystalline and chemically ordered during irradiation, and exhibited only a ∼ 10 % decrease in shear modulus. Hence, these two results provide further support that a shear instability triggers irradiation-induced amorphization. The shear instability mechanism may also apply to other solid-state amorphization techniques, e.g. hydrogen charging and mechanical deformation.

The Effect of Temperature on Defect Production in Copper Doped with Beryllium

1984 ◽  
Vol 41 ◽  
Author(s):  
A. C. Baily ◽  
Wayne E. King ◽  
K. L. Mrkle ◽  
M. Meshii
Keyword(s):  
Incident Beam ◽  
Stage I ◽  
Effect Of Temperature ◽  
Defect Production ◽  
Voltage Electron ◽  
Crystallographic Anisotropy ◽  
Crystal Films ◽  
Radiation Induced ◽  
Annealing Experiments

AbstractThe effect of temperature on radiation-induced defect production was investigated in Cu single crystal films doped with ∼ 100 ppm Be. Frenkel pair production was determined at 55K and 190K as a function of electron energy and incident beam direction using in situ electrical resistivity measurements in the high voltage electron microscope. The crystallographic anisotropy of defect production was found to be considerably greater for irradiations at 55K than for irradiations below 10K. This difference is related largely to an observed anisotropy in the stage I defect recovery. It was found in isochronal annealing experiments after irradiation nearthreshold that the resistivity remaining after stage I was nearly twice as large for recoils along <110> as compared to <100>.

scholarly journals Influence of Chemical Operation on the Electrocatalytic Activity of Ba0.5Sr0.5Co0.8Fe0.2O3−δ for the Oxygen Evolution Reaction

2021 ◽  
Author(s):  
Yuta Inoue ◽  
Yuto Miyahara ◽  
Kohei Miyazaki ◽  
Yasuyuki Kondo ◽  
Yuko Yokoyama ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Alkaline Solution ◽  
Oxygen Evolution Reaction ◽  
Time Course ◽  
Potential Cycling ◽  
Leaching Behavior ◽  
Fundamental Understanding ◽  
A Site

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a promising electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. The OER activities of BSCF are gradually enhanced by prolonging the duration of electrochemical operation at OER potentials, but the underlying cause is not fully understood. In this study, we investigated the role of chemical operation, equivalent to immersion in alkaline solution, in the time-course of OER enhancement of BSCF. Interestingly, the time-course OER enhancement of BSCF was promoted not only by electrochemical operation, which corresponds to potential cycling in the OER region, but also by chemical operation. In situ Raman measurements clarified that chemical operation had a lower rate of surface amorphization than electrochemical operation. On the other hand, the leaching behavior of A-site cations was comparable between chemical and electrochemical operations. Since the OER activity of BSCF was stabilized by saturating the electrolyte with Ba2+, “chemical” A-site leaching was key to inducing the time-course OER enhancement on perovskite electrocatalysts. Based on these results, we provide a fundamental understanding of the role of chemical operation in the OER properties of perovskites.

In situ examination of radiation-induced internal stress relaxation in the column of a high-voltage electron microscope

1984 ◽  
Vol 56 (3) ◽  
pp. 147-150 ◽  
Author(s):  
I. I. Novikov ◽  
V. A. Ermishkin ◽  
V. G. Zharkov ◽  
E. N. Samoilov ◽  
I. S. Lupakov ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Stress Relaxation ◽  
Internal Stress ◽  
High Voltage ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Radiation Induced ◽  
In Situ Examination
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