bluuebunny/crossref_metadata_2025_split huggingface dataset:
Damage Response to Irradiation Temperature and Ion Fluence In C+-Irradiated 6H-SiC
Authors: Jiang W. , Weber W.J. , Thevuthasan S. 
Published: April 2011

AbstractIrradiation experiments have been performed 60° off the surface normal for 6H-SiC single crystals at various temperatures (185-870 K) using 550 keV C+ ions over a fluence range from 1×1018 to 5×109 ions/m2. Atomic disorder on the Si sublattice, as determined by in-situ RBS/channeling analysis, ranged from dilute defects to complete amorphization. The critical amorphization dose of ∼0.23 dpa (on the Si sublattice) at 185 K has been determined. Asymmetric shapes in angular yield profiles across the crystallographic axis <0001> emerged above 1.5×1019 C−/m2 (∼0.05 dpa in the near-surface region), which might be associated with the lattice disturbance in the crystal structure. A gradual decrease in half-angular width was observed with the increase of ion fluence in the experiment. The minimum yield exhibits a rather linear relationship with ion dose at the surface. Post-irradiation annealing at the irradiation temperature did not result in measurable recovery for fluences ranging from 4 × 1018 to 2×1019 C+/m2 at 300, 470 and 670 K. Results also show that low fluence (<8×1018 C+/m2) irradiation at 185 K followed by thermal annealing results in similar defect concentrations to irradiation at that same temperature to the same ion fluence. Thus, at low fluences, the accumulated defects are in thermal equilibrium with the structure.
Microstructural Evolution of Radiation Induced Defects In ZnO During Isochronal Annealing
Authors: Brunner S. , Puff W. , Mascher P. , Balogh A.G. 
Published: April 2011

AbstractIn this study we discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing. The nominally undoped samples were irradiated either with 3 MeV protons to a fluence of 1.2× 1018 p/cm2 or with 1 MeV electrons to a fluence of 1×1018 e/cm2. The investigation was performed with positron lifetime and Doppler-broadening measurements. The measurements were done at room temperature and in some cases down to 10 K to investigate the thermal dependence of the trapping characteristics of the positrons.
Ion-Implantation/Annealing-Induced Precipitation of Nanophase Ferromagnetic Particles In Yttrium-Stabilized ZrO2
Authors: Honda S. , Modine F.A. , Meldrum A. , Budai J.D. , Haynes T.E. , Boatner L.A. , Gea L.A. 
Published: April 2011

AbstractIon implantation and thermal processing techniques have been used to form embedded ferromagnetic nanophase precipitates and thereby create magneto-optically active near-surface regions on otherwise inactive materials. Ferromagnetic precipitates were formed by first implanting Fe+ or Ni− into Y0.15Zr0.85O1.93(YSZ) with an implant energy of 140 keV, a fluence of 8.0 × 1016 ions/cm2, and at a temperature of-189°C. After implantation, the specimens were annealed at temperatures ranging from 500 to 1100°C in several types of reducing atmospheres. X-ray diffraction and TEM analysis of the Fe- or Ni-implanted/annealed specimens revealed that crystallographically coherent precipitates of metallic α-Fe, magnetite (Fe3O4), or Ni could be formed in YSZ depending on the annealing conditions. In particular, the cooling rate was established as the critical factor that determined whether Fe or Fe3O4 precipitates were created. Magneto-optical effects arising from ferromagnetic precipitates of Fe, Fe3O4, and Ni in the near-surface region of YSZ were observed and characterized using magnetic circular dichroism (MCD). The magneto-optical response of the α-Fe, Fe3O4, and Ni precipitates was markedly different as indicated by the MCD-detected hysteresis curves. The precipitation mechanism, the chemical nature of the precipitates, and the particle-size distributions resulting from different annealing conditions were investigated and correlated with the precipitate magneto-optical properties.
Low Temperature Ripple Formation: Ion-Induced Effective Surface Diffusion in Ion Sputtering
Authors: Makeev M. A. , Barabási A.-L. 
Published: April 2011

AbstractSurfaces bombarded with energetic ions may develop a rough or a ripple surface morphology. The ripple formation has been successfully described by the instability caused by preferential erosion, the ripple wavelength being determined by the competition between surface erosion and thermally activated diffusion. However, as recent experiments and computer simulations have shown, ripple formation takes place even at the low temperatures, when thermally activated processes are suppressed. In this paper we propose a theory to explain low-temperature ripple formation based on the ion-induced effective surface diffusion.
Ion Beam Irradiation—An Efficient Method to Modify The Subnanometer Scale Microstructure of Polymers In A Controlled Way
Authors: Xu Xinglong , Coleman M. R. , Myler U. , Simpson P. J. 
Published: April 2011

AbstractThe microstructural evolution of polymers induced by ion beam irradiation was investigated using gas permeation measurements with different molecule size gases and positron annihilation spectroscopy (PAS) using variable-energy positron. Simultaneous large increases in gas permeability and permselectivity of polymer-ceramic composite membranes modified by 180 keV H+ ion irradiation indicated that ion irradiation of polymers can modify the microstructure of polymer at sub-nanometer level in a controlled way. PAS results were consistent with the gas permeation results. The results of this work demonstrated ion beam irradiation has a promising application potential in the separation industry.
Light Ion Irradiation Creep of SCS-6 Silicon Carbide Fibers in the Temperature Range 450 – 1100°C
Authors: Scholz R. , Pasic H. 
Published: April 2011

AbstractCreep tests were conducted in torsion on Textron SCS-6™ silicon carbide (SiC) fibers during irradiation with light ions in the temperature range 450-1100°C up to doses of 0.06 dpa. The fibers, produced by chemical vapor deposition (CVD), should be representative of a SiC/SiC composite matrix produced by chemical vapor infiltration (CVI).For temperatures between 450 and 600°C, the irradiation creep curves were characterised by long lasting strain transients during which the creep rate slowed down before reaching approximately steady state values. On a decrease in temperature the creep rate increased.For temperatures between 900 and 1100°C, the transient creep regime was negligible. The creep rates reached constant values shortly after starting the irradiation and increased with temperature. The activation energy was E = 0.55±0.15 eV.The results are discussed in terms of concentration and mobility of point defects and the change of these quantities with temperature.
Effect of Low Temperature ion Irradiation on the Microstructure of Nitride Ceramics
Authors: Zinkle S.J. , Snead L.L. , Eatherly W. S. , Jones J.W. , Hensley D.K. 
Published: April 2011

AbstractCross-section transmission electron microscopy was used to investigate the microstructure of polycrystalline silicon nitride (Si3N4) and aluminum nitride (AIN) following 2 MeV Si ion irradiation at 80 and 400 K up to a fluence of 4×1020ions/m2(maximum damage of ∼ 10 displacements per atom, dpa). A buried amorphous band was observed at both temperatures in Si3N4in the region corresponding to the peaks in the implanted ion and displacement damage. From a comparison of Si3N4specimens irradiated at different fluences, it is concluded that the amorphization is primarily controlled by the implanted Si concentration rather than the displacement damage level. Si3N4 amorphization did not occur in regions well-separated from the implanted ions for doses up to at least 3 dpa at 80 K, whereas amorphization occurred in the ion implanted region (calculated Si concentration >0.01 at.%) for damage levels as low as ∼0.6 dpa. The volumetric swelling associated with the amorphization of Si3N4, is <10%. Amorphization was not observed in any of the irradiated AIN specimens. A moderate density of small (∼3 nm) defect clusters were observed in the crystalline damaged regions of both the Si3N4and AIN specimens at both irradiation temperatures. Aligned network dislocations were also observed in the AIN specimen irradiated to high dose at 80 K.
Bubble formation and growth in glasses
Authors: Chen Xidong , Birtcher Robert C. , Donnelly S.E. 
Published: April 2011

AbstractIn this study, we simulated gas bubble formation in glasses by in-situ ion implantation. Alkali silicate glass and Na-borosilicate glass were implanted in situ with 50 keV Xe ions at temperatures at 200°C in a Hitachi-9000 electron microscope. Bubble formation was studied by transmission electron microscopy images taken during interruptions of the ion beam after discrete implanted-ion dose steps. We present a possible mechanism of bubble formation and growth based on amorphous network structures.
Molecular Dynamics Simulation of Recoil Nucleus Displacement Cascade in Zircon
Authors: Crocombette Jean-Paul , Ghaleb Dominique 
Published: April 2011

AbstractThe results of molecular simulations of a-recoil nucleus displacement cascades in zircon (ZrSiO4) are presented. The local temperature and pressure are found to increase dramatically during the cascade. The structure of the cascade tracks is amorphous. Its shape has been analyzed in terms of disordered and distorted cations. SiO2 nanophase are found to exist in the tracks consistently with what is observed in the experiments.
Electron Irradiation of Zeolites
Authors: Wang S. X. , Wang L. M. , Ewing R. C. 
Published: April 2011

AbstractThree different zeolites (analcime, natrolite, and zeolite-Y) were irradiated with 200 keV and 400 keV electrons. All zeolites amorphized under a relatively low electron fluence. The transformation from the crystalline-to-amorphous state was continuous and homogeneous. The electron fluences for amorphization of the three zeolites at room temperature were: 7.0× 1019 e/cm2 (analcime), 1.8×1020 e/cm2 (natrolite), and 3.4×1020 e/cm2 (zeolite-Y). The different susceptibilities to amorphization are attributed to the different channel sizes in the structures which are the pathways for the release of water molecules and Na+. Natrolite formed bubbles under electron irradiation, even before complete amorphization. Analcime formed bubbles after amorphization. Zeolite-Y did not form bubbles under irradiation. The differences in bubble formation are attributed to the different channel sizes of the three zeolites. The amorphization dose was also measured at different temperatures. An inverse temperature dependence of amorphization dose was observed for all three zeolites: electron dose for amorphization decreased with increasing temperature. This unique temperature effect is attributed to the fact that zeolites are thermally unstable. A semi-empirical model was derived to describe the temperature effect of amorphization in these zeolites.
The Effect of Temperature and Damage Energy on Amorphization in Zircon
Authors: Weber W. J. , Devanathan R. , Meldrum A. , Boatner L. A. , Ewing R. C. , Wang L. M. 
Published: April 2011

AbstractSeveral groups have irradiated single crystals of synthetic and natural zircon (ZrSiO4) with a wide range of ions (from He to Bi) over a wide range of temperatures. The results of these studies show that amorphization in zircon is controlled by a variety of parameters and is a more complex process than previously thought. The critical dose for amorphization increases with temperature, similar to other materials. However, the critical displacement dose (in dpa) for amorphization is significantly higher at lower temperatures (below 500 K) for very heavy ions, such as Pb and Bi. This unusual dependence on the damage energy density has not been observed previously in other materials. Possible explanations for this behavior in terms of amorphization mechanisms are discussed. In addition, there is a significant difference in the temperature dependence of the critical dose in synthetic and natural zircons, which suggests that the impurities in natural zircons may affect the kinetics of recovery processes.
Tin E' Centers in X-Ray Irradiated Sn-Doped Silica
Authors: Chiodini N. , Meinardi F. , Morazzoni F. , Paleari A. , Scotti R. , Spinolo G. 
Published: April 2011

AbstractSn centers are point defects easily formed by X-ray irradiation of Sn-doped silica. Point defects are a tool for assessing the substitutional character of the dopant in Sn-doped SiO2 glasses with different Sn content (SnO2/SiO2 ratio from 0.01 to 10.0 % w/w) and prepared by two sol-gel methods differing in tin precursors (tin tetraterbutoxide and tin dibutyldiacetate). The former method produced transparent crack-free monolithic glasses of Sn-doped silica with maximum tin content of 0.1 % (SnO2/SiO2 % w/w). The latter method is more efficient and produced transparent glasses with a tin content of 1%.
Modeling of Microstructure Evolution in Austenitic Stainless Steels Irradiated Under Light Water Reactor Conditions
Authors: Gan J. , Was G.S. , Stoller R.E. 
Published: April 2011

AbstractA model for the development of microstructure during irradiation in fast reactors has been adapted for light water reactor (LWR) irradiation conditions (275 ∼ 325 °C, up to ∼ 10 dpa). The original model was based on the rate-theory, and included descriptions of the evolution of both dislocation loops and cavities. The model was modified by introducing in-cascade interstitial clustering, a term to account for the dose dependence of this clustering, and mobility of interstitial clusters. The purpose of this work was to understand microstructural development under LWR irradiation with a focus on loop nucleation and saturation of loop density. It was demonstrated that in-cascade interstitial clustering dominates loop nucleation in neutron irradiation in LWRs. Furthermore it was shown that the dose dependence of in-cascade interstitial clustering is needed to account for saturation behavior as commonly observed. Both quasi-steady-state (QSS) and non-steady-state (NSS) solutions to the rate equations were obtained. The difference between QSS and NSS treatments in the calculation of defect concentration is reduced at LWR temperature when in-cascade interstitial clustering dominates loop nucleation. The mobility of interstitial clusters was also investigated and its impact on loop density is to reduce the nucleation term. The ultimate goal of this study is to combine the evolution of microstructure and microchemistry together to account for the radiation damage in austenitic stainless steels.
Cr-Vacancy Elastic and Chemical Interactions in Irradiated Stainless Steels
Authors: Simonen E. P. , Bruemmer S. M. 
Published: April 2011

AbstractInteractions between point defects and major solute strongly influence grain boundary concentrations during heat treatment, irradiation and annealing of austenitic stainless steels. Previous approaches to nonequilibrium segregation emphasize only elastic defect-solute interactions. The present evaluation of nonequilibrium concentrations at grain boundaries indicates chemical interactions unique to solution annealing and cooling during thermal nonequilibrium segregation (TNES). Subsequent to TNES, radiation-induced segregation and post-irradiation annealing are modeled and compared with measured changes in grain boundary composition. The latter two mechanisms are controlled by exchanges between vacancies and major solute such as Cr.
Evidence for Thermal Spike Effects in Ion-Irradiated Ni3Al
Authors: Jenkins M. L. , Mavani P. , Müller S. , Abromeit C. 
Published: April 2011

AbstractThe influence of the irradiation temperature Tirr on the development of disordered zones produced at displacement cascades in Ni3A1 by heavy-ion irradiation with 50 keV Ta+ and 300 keV Ni+ ions has been investigated. The normalised number density (yield) of disordered zones for 300 keV Ni+ irradiation showed a sharp fall between Tirr= 373 K and 573 K. For 50 keV Ni+ irradiation there was a similar fall between 573 K and 673 K. The mean diameters of the disordered zones produced by 300 keV Ni+ ions decreased by about 2 nm between room temperature and 573 K, and there was a tendency for larger zones to become more regular in shape. For 50 keV Ta+ ions, a similar trend was observed between 573 K and 873 K. An annealing experiment confirmed that disordered zones produced at lower temperatures were stable up to a temperature of about 673 K, showing that these trends cannot be due to thermal annealing of disordered zones. The experimental results are consistent with an increased tendency for reordering at the peripheries of disordered zones, due to the increased lifetimes of thermal spikes at higher irradiation temperatures.
Sink Strength Evolution of Heavy Ion Irradiated Nickel
Authors: Fielitz P. , Macht M.-P. , Naundorf V. , Wollenberger H. 
Published: April 2011

AbstractAtom transport under irradiation is determined by the concentration of freely migrating defects, which depends on the dynamical equilibrium between production and annihilation rates. In order to determine effective values of both of these quantities for the case of ion irradiation, spatially resolved self-diffusion measurements were performed on single crystals of nickel which contained several thin tracer layers at different depths.For fixed depth the radiation-enhanced diffusion coefficient (DK) was determined as function of displacement rate (K0) and fluence (Φ). The DK essentially representing the ratio of the rates of production and annihilation was found to be proportional to K0 for 800 K irradiation temperature and to K00.4for Ni and K00.4for Kr irradiation at 950 K. It is independent of Φ for 800 K and decreases with increasing Φ for 950 K.
Craters Produced on Metals by Single Ion Impacts
Authors: Birtcher R. C. , Donnelly S. E. 
Published: April 2011

summaryThe surface is a major perturbation on displacement cascades resulting from ion impacts. Ion impacts on dense materials result in nanometer sized craters on materials with densities greater than 7.3 g/cm3. Although stable when the irradiation is interrupted, single ion impacts can modify or annihilate existing craters. Single ion impacts can extrude material from the specimen. Flow from the melt zone of cascades is responsible for the observed changes.
Effects of Neutron Irradiation on Tensile Properties of V-Ti-Cr-Si Type Alloys with Pre-Existing Helium
Authors: Satou M. , Chuto T. , Koide H. , Hasegawa A. , Abe K. 
Published: April 2011

AbstractHelium effect on loss of uniform elongation after low-temperature neutron irradiation of the V-Ti-Cr-Si-Al-Y alloy was studied. Helium implantation to about 30 atomic ppm was carried out before neutron irradiation to 50 dpa at 406°C. The yield stress of the irradiated specimen with helium pre-implantation was slightly smaller than that of irradiated specimens without helium. The uniform elongation and the increase in yield stress of the irradiated specimens were not affected by helium pre-implantation at ambient temperature. It might be possible that the helium effect appears after lower temperature irradiation such as 300°C or lower, which corresponds to the temperature range where the loss of uniform elongation of the alloy is particularly pronounced.
Effect of Formation and Growth of Dislocation Loops and Cavities on Low-Temperature Swelling of Irradiated Uranium-Molybdenum Alloys
Authors: Rest J. , Hofman G. L. , Konovalov I. I. , Maslov A. A. 
Published: April 2011

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.
Kinetic Monte Carlo Simulations of Fecu Alloys
Authors: Domain C. , Becquart C.S. , Van Duysen J.C. 
Published: April 2011

AbstractThe steel vessels of pressurized water reactors are embrittled by neutron irradiation. It is well known that copper atoms play an important role in the embrittlement and that different Cu- containing defects such as Cu-rich clusters (sometimes called atmospheres), Cu precipitates and Cu-vacancy complexes have been identified experimentally. It is still difficult to link the formation of these defects to the primary damage resulting from the neutron inducing displacement cascades. Therefore, we investigate the evolution of the primary damage in FeCu alloys using kinetic Monte Carlo simulations based on a vacancy diffusion mechanism. The calculations rely on adapted, phenomenological, n-body potentials that satisfactorily reproduce properties of FeCu. At room temperature, experimentally identified defects such as Cu-vacancy complexes (one Cu atom bound to three or four vacancies) form in the course of our simulations. Furthermore, it appears that complex defects such as a Cu atom linked to two vacancies are very mobile and are responsible for the formation of small Cu clusters.
Orientation and Temperature Dependence of Electron-Induced Crystallization in Si and Ge
Authors: Hollar E. P. , Robertson I. M. , Jeničič I. 
Published: April 2011

AbstractSi and Ge samples of different substrate orientations were implanted with 50 keV Xe+ ions to a dose around 1011 ions/cm2 where the amorphous zones, created by individual ions, remained spatially isolated. The samples were subsequently irradiated at either 90 or 300K with electrons having energies from 25 to 300 keV in a transmission electron microscope (TEM). At all electron energies and at both temperatures a significant fraction of amorphous zones crystallized, showing that this effect is not due to a temperature increase and occurs at energies below the threshold displacement energy. Preliminary results show that in Ge the crystallization rate depends on the substrate orientation, while in Si this effect was not observed. The results are discussed in terms of possible explanations for epitaxial growth.
Point Defect Cluster Formation in Iron Displacement Cascades UP to 50 keV
Authors: Stoller Roger E. 
Published: April 2011

AbstractThe results of molecular dynamics displacement cascade simulations in iron at energies up to 50 keV and temperatures of 100, 600, and 900K are summarized, with a focus on the characterization of interstitial and vacancy clusters that are formed directly within the cascade. The fraction of the surviving point defects contained in clusters, and the size distributions of these in-cascade clusters have been determined. Although the formation of true vacancy clusters appears to be inhibited in iron, a significant degree of vacancy site correlation was observed. These well correlated arrangements of vacancies can be considered nascent clusters, and they have been observed to coalesce during longer term Monte Carlo simulations which permit short range vacancy diffusion. Extensive interstitial clustering was observed. The temperature and cascade energy dependence of the cluster size distributions are discussed in terms of their relevance to microstructural evolution and mechanical property changes in irradiated iron-based alloys.