scholarly journals In-Situ Hvem Studies of Radiation-Induced Segregation In Ni-Al Alloys During Simultaneous Irradiation with Electrons and Ions

1995 ◽  
Vol 396 ◽  
Author(s):  
M. J. Giacobbe ◽  
N. Q. Lam ◽  
P. R. Okamoto ◽  
J. F. Stubbins
Keyword(s):  
National Laboratory ◽  
Argonne National Laboratory ◽  
Kirkendall Effect ◽  
Radial Component ◽  
Al Alloy ◽  
Tandem Accelerator ◽  
Accelerator Facility ◽  
Radial Segregation ◽  
Radiation Induced

AbstractThe effects of 75-keV Ne+ and 300-keV Ni+ bombardment on electron radiation-induced segregation (RIS) in a Ni-9at%Al alloy were investigated in-situ using the HVEM (high voltage electron microscope)/Tandem accelerator facility at Argonne National Laboratory. The radial component of defect fluxes generated by a highly-focused 900-keV electron beam was used to induce segregation of Al atoms towards the center of the electron irradiated area via the inverse-Kirkendall effect. The radial segregation rate was monitored by measuring the increase in the diameter of the Al enriched zone within which γ'-νi3αl precipitates form during irradiation. Both dual electron-ion and pre-implanted ion-electron irradiations were performed in an attempt to separate the contributions of energetic displacement cascades and implanted ions acting as defect trapping sites to RIS suppression. It was found that 75-keV Ne implantation has a retarding effect on RIS.

scholarly journals Effects of Ion Implantation and Temperature on Radiation-Induced Segregation In Ni-9Al Alloys

1996 ◽  
Vol 439 ◽  
Author(s):  
M. J. Giacobbe ◽  
N. Q. Lam ◽  
P. R. Okamoto ◽  
N. J. Zaluzec ◽  
J. F. Stubbins
Keyword(s):  
National Laboratory ◽  
Argonne National Laboratory ◽  
Kirkendall Effect ◽  
Implantation Dose ◽  
Accelerator Facility ◽  
Strong Suppression ◽  
Suppression Effect ◽  
Voltage Electron ◽  
Radial Segregation ◽  
Radiation Induced

AbstractThe effects of Ne and Sc implantation on radiation-induced segregation (RIS) in Ni- 9at.%Al were studied in-situ utilizing the high-voltage electron microscopeffandem accelerator facility at Argonne National Laboratory. A highly-focused 900-keV electron beam generated radial defect fluxes which, in turn, induced the transport of Al atoms toward the center of the electronirradiated area via the inverse-Kirkendall effect. The radial segregation rate of Al atoms was monitored by measuring the diameter of the γ′-Ni3Al zone which formed in the Al-enriched area during irradiation. Ne and Sc implantation effects on RIS were investigated at 550°C, while Ne effects were also examined at 625°C to determine the influence of temperature on the ability of Ne to act as defect trapping sites, causing RIS suppression. It was found that the RIS suppression effect of Ne increased with increasing irradiation temperature, and that Sc had a small RIS suppression effect which increased with increasing Sc implantation dose. Ne bubbles which formed during implantation are believed to be responsible for its strong suppression effect.

scholarly journals In-situ investigation of ion-implantation effects on radiation-induced segregation in Ni-Al alloys

1996 ◽  
Vol 54 ◽  
pp. 988-989
Author(s):  
M.J. Giacobbe ◽  
N.Q. Lam ◽  
P.R. Okamoto ◽  
N.J. Zaluzec ◽  
J.F. Stubbins
Keyword(s):  
Electron Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Beam Diameter ◽  
Total Electron ◽  
Radial Segregation ◽  
In Situ Investigation ◽  
In Situ Experiments ◽  
Radiation Induced

In-situ experiments using the HVEM (high voltage electron microscope)/Tandem accelerator facility at Argonne National Laboratory were performed to determine the effects of 400-keV Zr+ and 75-keV Ne+ implantation on electron radiation-induced segregation (RIS) in Ni-9at.%Al at 550°C and 450°C, respectively. The alteration of RIS kinetics by Ne implantation was studied at two different doses. A highly-focused 900-keV electron beam, which produces a radial defect flux away from the beam center, was used to induce segregation of Al atoms in the opposite direction via the inverse-Kirkendall effect. Within the irradiated zone, Al enrichment drives the formation of γ′-Ni3Al precipitates, and the radial segregation rate of Al was monitored by measuring the growth of the precipitate zone.When a thin film is subject to a focused, electron beam, a non uniform defect distribution is produced. The effective beam diameter, D∘, is defined by IT= I∘ (πD∘/2)2 where IT is the total electron current and I∘ is the peak electron flux.

Effects of krypton ion irradiation on the structure and morphology of germanium — An in situ TEM study

1990 ◽  
Vol 48 (4) ◽  
pp. 536-537
Author(s):  
L.M. Wang ◽  
R.C. Birtcher
Keyword(s):  
Ion Irradiation ◽  
Morphological Changes ◽  
Amorphous Material ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
In Situ Tem ◽  
Tandem Accelerator ◽  
Accelerator Facility ◽  
Voltage Electron

Although it was initially thought that irradiation could not further damage an amorphous material, an anomalous ion-induced morphological instability on the surface of amorphous Ge has been reported previously by several authors. In this study, the structural and morphological changes of Ge were monitored during 1.5 MeV Kr ion irradiation by in situ TEM to obtain insight into the damage evolution in ion-irradiated Ge.The in situ study was performed on the HVEM-Tandem Accelerator Facility at Argonne National Laboratory. The facility consists of a modified Kratos/AEI EM7 high voltage electron microscope (HVEM) and a 2 MV tandem ion accelerator. The samples were jet-polished polycrystalline Ge (99.99999 at. % pure) TEM discs with grain size > 5 μm in dimension. The Kr ion irradiation was carried out at room temperature, and the electron energy of the HVEM was 300 kV. According to a TRIM computer simulation, over 99% of the Kr ions penetrate through the electron transparent areas of the Ge sample, and a dose of 1×1015 Kr/cm2 created an average of ∽4 displacements per atom and an average Kr concentration of ∽12 appm in the observation region of the sample.

scholarly journals In Situ TEM Observations of Heavy Ion Damage in Gallium Arsenide

1988 ◽  
Vol 100 ◽  
Author(s):  
M. W. Bench ◽  
I. M. Robertson ◽  
M. A. Kirk
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
In Situ Tem ◽  
Accelerator Facility ◽  
Transmission Electron ◽  
Ion Accelerator

ABSTRACTTransmission electron microscopy experiments have been performed to investigate the lattice damage created by heavy-ion bombardments in GaAs. These experiments have been performed in situ by using the HVEN - Ion Accelerator Facility at Argonne National Laboratory. The ion bcorbardments (50 keV Ar+ and Kr+) and the microscopy have been carried out at temperatures rangrin from 30 to 300 K. Ion fluences ranged from 2 × 1011 to 5 × 1013 ions cm−2.Direct-inpact amorphization is observed to occur in both n-type and semi-insulating GaAs irradiated to low ion doses at 30 K and room temperature. The probability of forming a visible defect is higher for low temperature irradiations than for room temperature irradiations. The amorphous zones formed at low temperature are stable to temperatures above 250 K. Post implantation annealing is seen to occur at room temperature for all samples irradiated to low doses until eventually all visible damage disappears.

The HVEM-tandem user facility at Argonne National Laboratory

1988 ◽  
Vol 46 ◽  
pp. 806-807
Author(s):  
C. W. Allen ◽  
E. A. Ryan ◽  
S. T. Ockers
Keyword(s):  
Radiation Effects ◽  
Ion Irradiation ◽  
Noble Gas ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Western Hemisphere ◽  
Accelerator Facility ◽  
Wide Range ◽  
In Situ Experiments

Established in 1981, the High Voltage Electron Microscope-Tandem Ion Accelerator Facility (HVEM-Tandem) is a user-oriented resource for materials research. It is located at Argonne National Laboratory about 20 miles south of O'Hare International Airport near Chicago. The Facility consists of a modified Kratos/AEI HVEM with accelerating voltages ranging continuously from 0.1-1.2 MeV, interfaced to a 2 MV tandem and a 0.65 MV ion implanter-type accelerator. This combination of instruments offers capability, unique in the western hemisphere, for a wide range of in Situ experiments involving ion irradiation and ion implantation with simultaneous microscopy. During 1987 approximately 75% of microscope time was devoted to this type of experiment (Fig. 1) including studies of solid state phase transformations, such as amorphization, radiation damage and defect structures and the implantation of noble gas and metal ions.In situ experiments of various types account for nearly 90% of usage of the HVEM. In addition to the radiation effects studies, this includes experiments performed in the microscope involving deformation, annealing and environmental effects.

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.

Ion Irradiation of Ternary Pyrochlores

2008 ◽  
Vol 1122 ◽  
Author(s):  
Karl R. Whittle ◽  
Katherine L. Smith ◽  
Mark G. Blackford ◽  
Simon A.T. Redfern ◽  
Elizabeth J. Harvey ◽  
...  
Keyword(s):  
Ion Irradiation ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Structural Disorder ◽  
Critical Temperatures ◽  
High Doses

AbstractSynthetic pyrochlore samples Y2Ti2-xSnxO7 (x=0.4, 0.8, 1.2, 1.6), Nd2Zr2O7, Nd2Zr1.2Ti0.8O7, and La1.6Y0.4Hf2O7, were irradiated in-situ using the IVEM-TANDEM microscope facility at the Argonne National Laboratory. The critical temperatures for amorphisation have revealed a dramatic increase in tolerance with increasing Sn content for the Y2Ti2-xSnxO7 series. This change has also found to be linear with increasing Sn content. Nd2Zr1.2Ti0.8O7 and La1.6Y0.4Hf2O7 were both found to amorphise, while Nd2Zr2O7 was found to be stable to high doses (2.5×10^15 ions cm-2). The observed results are presented with respect to previously published results for irradiation stability predictions and structural disorder.

Amorphization Kinetics of Zr (Cr,Fe)2 Under Ion Irradiation

1992 ◽  
Vol 279 ◽  
Author(s):  
A. T. Motta ◽  
L. M. Howe ◽  
P. R. Okamoto
Keyword(s):  
Neutron Irradiation ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Matrix Interface ◽  
Thin Foils ◽  
Intermetallic Precipitates ◽  
Kinetics Of

ABSTRACTThin foils of Zircaloy-4 were irradiated with 350 KeV 40Ar ions in the dual ion beam/HVEM facility at Argonne National Laboratory at 300 – 650 K. The irradiation-induced araorphization of the intermetallic precipitates Zr (Cr, Fe)2 and Zr2 (Ni, Fe) was studied in situ. For Zr (Cr,Fe)2 precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization which started at the precipitate-matrix interface. For Zr2 (Ni,Fe) precipitates it was found that amorphization occurred at 550 K and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in the context of the previous experimental results of neutron and electron irradiation and likely amorphization mechanisms are proposed.

The local structure of Ta(v) aqua ions in high temperature fluoride- and chloride-bearing solutions: Implications for Ta transport in granite-related postmagmatic fluids

2019 ◽  
Vol 57 (6) ◽  
pp. 843-851
Author(s):  
Alan J. Anderson ◽  
Robert A. Mayanovic ◽  
Thomas Lee
Keyword(s):  
High Temperature ◽  
Local Structure ◽  
Elevated Temperatures ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Acidic Solutions ◽  
Diamond Anvil ◽  
X Ray Absorption ◽  
Photon Source

Abstract The local structure of Ta(V) in high-temperature fluoride- and chloride-bearing acidic solutions was investigated using in situ X-ray absorption spectroscopy (XAS). All XAS spectra were collected from two solutions, designated A and B, at beamline ID-20-C at the Advanced Photon Source, Argonne National Laboratory. Spectra were collected from solution A at 350 and 400 °C and from solution B at 25, 360, and 400 °C after the solutions were sealed in a hydrothermal diamond anvil cell. Solution A was prepared by dissolving Ta2O5 powder in 5% HF solution; solution B consisted of TaCl5 dissolved in 2% HF. The dominant tantalum species in solution A at elevated temperatures was TaF83–. In contrast, TaCl6–, which was the dominant complex in solution B at room temperature, disappeared as hydroxide complexes with an average ligand number between 5 and 7 became the dominant species at 350 and 400 °C. The XAS results confirm the previously recognized effect of fluoride activity on Ta speciation in hydrothermal fluids and suggest that both fluoride and hydroxide complexes play an important role in the transport of Ta in acidic fluoride-bearing solutions involved in the formation of mineralized mica-rich replacement units in granitic pegmatites.

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