Damage Accumulation and Thermal Recovery in SrTiO3 Implanted with Au2+ Ions

1998 ◽  
Vol 540 ◽  
Author(s):  
S. Thevuthasan ◽  
W. Jiang ◽  
W.J. Weber ◽  
D.E. McCready
Keyword(s):  
Single Crystal ◽  
Damage Accumulation ◽  
Rutherford Backscattering Spectrometry ◽  
Recovery Process ◽  
Thermal Recovery ◽  
Broad Temperature Range ◽  
Maximum Temperature ◽  
Recovery Processes ◽  
Annealing Experiments

AbstractDamage accumulation and recovery process have been investigated in single crystal SrTiO3 irradiated with 1.0 MeV Au2+ using in-situ Rutherford Backscattering Spectrometry (RBS) in Channeling geometry. Samples were irradiated at a temperature of 200 K with ion fluences ranging from 5.0×1013 2.5×1014Au2+/cm2 (0.22 – 1.10 dpa at damage peak). Subsequent isochronal annealing experiments were performed to study damage recovery processes up to a maximum temperature of 870 K. At an ion fluence between 2.0–2.5×1014Au2+/cm2 (0.88 – 1.10 dpa), the implanted region, which is just below the surface, becomes amorphous. The recovery processes occur over a broad temperature range, and the damage created by low ion fluences, 5.0×1013 − 1.0×1014 Au2+/cm2, is almost completely recovered after annealing at 870 K.

Accumulation and Recovery of Irradiation Effects in Silicon Carbide

1998 ◽  
Vol 540 ◽  
Author(s):  
W.J. Weber ◽  
W. Jiang ◽  
S. Thevuthasan ◽  
D.E. Mecready
Keyword(s):  
Activation Energy ◽  
Damage Accumulation ◽  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Complete Recovery ◽  
Structural Disorder ◽  
Dose Dependence ◽  
Thermal Recovery ◽  
Recovery Processes ◽  
Wide Range

AbstractSingle crystals of 6H-SiC have been irradiated with a variety of ions over a wide range of fluences and temperatures. The temperature and dose dependence of damage accumulation has been investigated using in-situ Rutherford Backscattering Spectrometry in channeling geometry. At low temperatures, the accumulation of structural disorder exhibits a sigmoidal dependence on dose. At room temperature and higher, simultaneous recovery processes during irradiation significantly reduce the damage accumulation rates by up to a factor of five. Isochronal and isothermal annealing studies have been used to study the damage recovery behavior. For low defect concentrations introduced by 550 keV Si+ irradiation at 160 K, complete recovery is observed at 300 K. However, defects introduced by He+ irradiation on the Si sublattice are more difficult to anneal at room temperature, which suggests trapping of the implanted helium may inhibit defect recombination. Below room temperature, the thermal recovery of defects on the Si sublattice has an activation energy on the order of 0.3 ± 0.1 eV. Defect recovery above 570 K has an activation energy on the order of 1.5 ± 0.3 eV.

Amortization And Dynamic Recovery Of A2BO4 Structure Types During 1.5 MeV Krypton Ion-Beam Irradiation

1993 ◽  
Vol 321 ◽  
Author(s):  
L. M. Wang ◽  
W. L. Gong ◽  
R. C. Ewing
Keyword(s):  
Dynamic Recovery ◽  
Ion Beam ◽  
Recovery Process ◽  
Beam Irradiation ◽  
Ion Beam Irradiation ◽  
Materials Properties ◽  
Recovery Processes ◽  
Rate Of Increase ◽  
A Site

ABSTRACTThe temperature dependence of the critical amorphization dose, Dc, of four A2BO4 compositions, forsterite (Mg2SiO4), fayalite (Fe2SiO4), synthetic Mg2GeO4, and phenakite (Be2SiO4) was investigated by in situ TEM during 1.5 MeV Kr+ion beam irradiation at temperatures between 15 to 700 K. For the Mg- and Fe-compositions, the A-site is in octahedral coordination, and the structure is a derivative hep (Pbnm); for the Be-composition, the A- and B-sites are in tetrahedral coordination, forming corner-sharing hexagonal rings (R3). Although the Dc's were quite close at 15 K for all the four compositions (0.2–0.5 dpa), Dc increased with increasing irradiation temperature at different rates. The Dc-temperature curve is the result of competition between amorphization and dynamic recovery processes. The Dc rate of increase (highest to lowest) is: Be2SiO4, Mg2SiO4, Mg2GeO4, Fe2SiO4. At room temperature, Be2SiO4 amorphized at 1.55 dpa; Fe2SiO4, at only 0.22 dpa. Based on the Dc-temperature curves, the activation energy, Ea, of the dynamic recovery process and the critical temperature, Tc, above which complete amorphization does not occur are: 0.029, 0.047, 0.055 and 0.079 eV and 390, 550, 650 and 995 K for Be2SiO4, Mg2SiO4, Mg2GeO4 and Fe2SiO4, respectively. These results are explained in terms of the materials properties (e.g., bonding and thermodynamic stability) and cascade size which is a function of the density of the phases. Finally, we note the importance of increased amorphization cross-section, as a function of temperature (e.g., the low rate of increase of Dc with temperature for Fe2SiO4).

Defect Accumulation and Recovery in Ion-Implanted 6H-SiC

2002 ◽  
Vol 719 ◽  
Author(s):  
W. Jiang ◽  
W. J. Weber ◽  
C. M. Wangxya
Keyword(s):  
Single Crystal ◽  
Ion Beam ◽  
Irradiation Temperature ◽  
Recovery Processes ◽  
Defect Accumulation ◽  
Different Temperatures ◽  
Induced Defects ◽  
Ion Species ◽  
Irradiation Induced Defects

AbstractSingle crystal wafers of <0001>-oriented 6H-SiC were irradiated at different temperatures using a variety of ion species. The disorder on both the Si and C sublattices has been studied in situ using a combination of ion beam analyses in multiaxial channeling geometry. The fraction of the irradiation-induced defects surviving simultaneous recovery processes decreases with decreasing ion mass and with increasing irradiation temperature. Some of the Si and C defects are well aligned with the <0001> axis and the rate of C disordering is higher than that of Si disordering. Three recovery stages in Au2+-irradiated 6H-SiC have been identified.

A Numerical Simulation Model for Thermal Recovery Processes

1979 ◽  
Vol 19 (01) ◽  
pp. 37-58 ◽  
Author(s):  
R.B. Crookston ◽  
W.E. Culham ◽  
W.H. Chen
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Combustion Zone ◽  
Combustion Process ◽  
Thermal Recovery ◽  
Water Flooding ◽  
Computational Results ◽  
In Situ Combustion ◽  
Recovery Processes

Abstract This paper describes a model for numerically simulating thermal recovery processes. The primary locus is on the simulation of in-situ combustion, but the formulation also represents fire-and-water flooding, steamflooding, hot water flooding, steam stimulation, and spontaneous ignition as well. The simulator describes the flow of water, oil, and gas, and includes gravity and capillary effects. Heat transfer by conduction, convection, and vaporization-condensation of both water and hydrocarbons are included. The rigorous but general nature of the simulator is obtained by employing conservation balance equations for oxygen, inert gases, a light hydrocarbon pseudocomponent, a heavy hydrocarbon pseudocomponent, water, coke, and energy. pseudocomponent, water, coke, and energy. Vaporization-condensation is governed by vaporliquid equilibrium using temperature and pressure-dependent equilibrium coefficients. Four pressure-dependent equilibrium coefficients. Four chemical reactions are accounted for: formation of coke from the heavy hydrocarbon component and the oxidation of coke and both heavy and light hydrocarbon components. Formulation details, numerical solution procedures, and computational results are presented. procedures, and computational results are presented. The computational results include both one- and two-dimensional cross-sectional studies. The simulator represents a major improvement in the ability to simulate thermal recovery processes under complex conditions. Introduction Considerable progress has been made in numerically simulating thermally enhanced oil-recovery processes during the last few years. This is particularly true for-processes involving steam, where we have seen a continual improvement of our ability to treat the problem. The most recent contributions provide an analysis capability for steam displacement and steam stimulation recovery methods, accounting for all the important physical mechanisms of these processes. Progress in simulating the performance of in-situ combustion processes is not so advanced. Initial simulation attempts were concerned primarily with the heat-transfer aspects of combustion. The most sophisticated heat-transfer model was developed by Chu. His numerical model considers the energy effects of vaporization and condensation on the temperature distribution, but neglects the accompanying phase changes by assuming constant fluid saturations. More recent heat transfer or heat-wave models for the in-situ combustion process were proposed by Kuo in 1969 and by Smith and Farouq-Ali in 1971. Kuo's model allows two temperature fronts-one at the combustion zone and one at a heat front. The heat-front position is predicted by gas flow that is allowed to have a velocity different from the velocity of the combustion front. The simulator proposed by Smith and Farouq-Ali is designed for proposed by Smith and Farouq-Ali is designed for predicting sweep efficiencies in confined well predicting sweep efficiencies in confined well patterns. Their numerical model accounts for heat patterns. Their numerical model accounts for heat generation by a combustion zone (assuming fixed fuel content all through the reservoir), heat transfer by conduction and convection (single-phase gas flow) in the reservoir, heat losses by conduction to adjacent formations, and different permeability-to-gas (air) flow on either side of the combustion zone. Special cases of the in-situ combustion process were studied by Gottfried and Khelil. These authors examine the heat transfer and oxygen use in reservoirs composed of an oil-bearing layer and an overlying "clean" porous zone containing only gas. These models were designed primarily to investigate the various transport mechanisms present when combustion is initiated in a reservoir present when combustion is initiated in a reservoir containing a gas cap. Because of the many assumptions invoked and the specialized geometry to which they apply, they do not satisfy the need for a general purpose simulator. SPEJ P. 37

Amorphization and Dynamic Recovery of A2BO4 Structure Types During 1.5 MeV Krypton Ion-Beam Irradiation

1993 ◽  
Vol 316 ◽  
Author(s):  
L.M. Wang ◽  
W.L. Gong ◽  
R.C. Ewing
Keyword(s):  
Dynamic Recovery ◽  
Ion Beam ◽  
Recovery Process ◽  
Beam Irradiation ◽  
Ion Beam Irradiation ◽  
Materials Properties ◽  
Recovery Processes ◽  
Rate Of Increase ◽  
A Site

ABSTRACTThe temperature dependence of the critical amorphization dose, Dc of four A2BO4 compositions, forsterite (Mg2SiO4), fayalite (Fe2SiO4), synthetic Mg2GeO4, and phenakite (Be2SiO4) was investigated by in situ TEM during 1.5 MeV Kr+ ion beam irradiation at temperatures between 15 to 700 K. For the Mg- and Fe-compositions, the A-site is in octahedral coordination, and the structure is a derivative hcp (Pbnm); for the Be-composition, the A- and B-sites are in tetrahedral coordination, forming corner-sharing hexagonal rings (R3). Although the Dc's were quite close at 15 K for all the four compositions (0.2–0.5 dpa), Dc increased with increasing irradiation temperature at different rates. The Dc-temperature curve is the result of competition between amorphization and dynamic recovery processes. The Dc rate of increase (highest to lowest) is: Be2SiO4, Mg2SiO4, Mg2GeO4, Fe2SiO4. At room temperature, Be2SiO4 amorphized at 1.55 dpa; Fe2SiO4, at only 0.22 dpa. Based on the Dc-temperature curves, the activation energy, Ea, of the dynamic recovery process and the critical temperature, Tc, above which complete amorphization does not occur are: 0.029, 0.047, 0.055 and 0.079 eV and 390, 550, 650 and 995 K for Be2SiO4, Mg2SiO4, Mg2GeO4 and Fe2SiO4, respectively. These results are explained in terms of the materials properties (e.g., bonding and thermodynamic stability) and cascade size which is a function of the density of the phases. Finally, we note the importance of increased amorphization cross-section, as a function of temperature (e.g., the low rate of increase of Dc with temperature for Fe2SiO4).

In Situ Study of the Temperature Dependence of Irradiation-Induced Amorphization in A-Sic

1995 ◽  
Vol 398 ◽  
Author(s):  
W. J. Weber ◽  
L. M. Wang ◽  
N. Yu ◽  
N. J. Hess
Keyword(s):  
Damage Accumulation ◽  
Ion Beam ◽  
Amorphous State ◽  
Damage Level ◽  
Ion Channeling ◽  
In Situ Study ◽  
Recovery Processes ◽  
Dual Beam ◽  
Two Stages

ABSTRACTIon-beam-induced amorphization in single crystal α-SiC has been studied as a function of temperature. Specimens have been irradiated with 1.5 MeV Xe+ ions over the temperature range from 20 to 475 K using the HVEM-Tandem Facility (ANL), and the evolution of the amorphous state has been followed in situ in the HVEM. Specimens also have been irradiated at 170, 300, and 370 K with 360 keV Ar+ ions, and the damage accumulation process followed in situ by Rutherford backscattering spectroscopy/channeling using the dual beam facilities at the Ion Beam Materials Laboratory (LANL). At 20 K, the displacement dose for complete amorphization is 0.25 dpa and increases with temperature in two stages. The activation energy associated with the simultaneous recovery processes above 100 K is 0.12 ± 0.02 eV. The critical temperature above which amorphization does not occur is 485 K under the 1.5 MeV Xe+ irradiation conditions. Ion channeling results suggest that the rate of simultaneous recovery increases with temperature only above a critical damage level. Raman spectroscopy indicates that rapid chemical disordering occurs during irradiation.

Damage Accumulation in MgAl2O4 Crystals by Xe Ion Irradiations

1993 ◽  
Vol 316 ◽  
Author(s):  
N. Yu ◽  
M. Nastasi ◽  
M.G. Hollander ◽  
C.R. Evans ◽  
C.J. Maggiore ◽  
...  
Keyword(s):  
Temperature Effect ◽  
Damage Accumulation ◽  
Rutherford Backscattering Spectrometry ◽  
Surface Region ◽  
Irradiation Damage ◽  
Spinel Layer ◽  
Near Surface ◽  
Ion Channeling ◽  
Significant Temperature

ABSTRACTWe have studied the damage kinetics in single crystal MgAl2O4 (spinel) with (100) orientation under 370 keV Xe ion irradiations at temperatures of -100 and 400 C. In-situ Rutherford Backscattering Spectrometry (RBS) and ion channeling have been used to monitor the damage accumulation in spinel following sequential Xe ion irradiations. A significant temperature effect on the irradiation damage has been found. Channeling data show that at -100 C, the irradiated spinel layer reaches the same level as in a random spectrum at a dose of 8×1015 Xe/cm2 (20 DPA for peak damage), while at 400 C, the near surface region (50 nm) remains single-crystalline up to 2×1016 Xe/cm2.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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