bluuebunny/crossref_metadata_2025_split huggingface dataset:
First Attempt to Develop A Material Model Describing Single Crystal Creep Behavior
Authors: Brehmn Holger , Glatzel Uwe 
Published: April 2011

AbstractA material model is proposed which describes single crystal creep behavior by evolution equations for dislocation densities on individual slip systems. An interaction matrix determines the influence from one glide system to the other. Assuming a face centered cubic crystal, allowing deformation on octahedral glide planes and cube glide planes with a Burgers vector of the type a/2 <110>, nine independent parameters of the interaction matrix can be distinguished. A parameter check of the nine independent parameters has been carried out, showing the influence of parameters on specific orientations of the load axis. If one assumes dislocation interaction of a glide system only with itself a smooth behavior is predicted with a maximum creep rate for [001] orientation, followed by [011] and [111]. If a strong interaction is assumed, the orientation dependent creep behavior is not at all smooth, instead it shows a sharp drop in creep rates mainly in symmetric positions of the standard orientation triangle. The orientations with highest creep rates are in this case those which favor single glide. Highly symmetric orientations, such as [001], [011] and [111] have strongly decreased stationary creep rates.
Coupled Meso-Macro Simulations of Plasticity: Validation Tests
Authors: Lemarchand C. , Devincre B. , Kubin L.P. , Chaboche J.L. 
Published: April 2011

AbstractA new numerical model has been developed in order to study the plastic deformation of mesoscopic crystalline samples under complex boundary conditions. The model is based on the coupling of two types of simulations, a dislocation dynamics and a finite element code. The former accounts for the dislocation-based plastic properties of the material, thus replacing the usual constitutive form, while the latter treats the boundary value problem and cares of the mechanical equilibrium. In order to test the hybrid simulation and examine its accuracy, the self-stress fields of straight dislocations have been computed in a single crystal of finite size and compared with the predictions of the isotropic elasticity theory. The excellent agreement obtained emphasizes the enormous potential of such hybrid methods for a rigorous treatment of meso-macro problems in plasticity.
Thermal Wave Analysis: A Tool for Non-Invasive Testing in Ion Beam Synthesis of Wide Band Gap Materials
Authors: Teichert G. , Schleicher L. , Knedlik Ch. , Voelskov M. , Skorupa W. , Yankov R.A. , Pezoldt J. 
Published: April 2011

AbstractPhotothermal methods provide a valuable complement to the destructive measurement techniques for the detection of the optimal process conditions in ion beam synthesis of wide band gap semiconductor compounds. In addition to their nondestructive and non contact qualities, they are highly sensitive to changes of thermophysical properties due to structural changes. Analyses have been carried out with (SiC)l-x(AIN)x compounds, formed by ion beam synthesis.
Instability of Nanocavities in Disordered and Amorphous Silicon Under Ion Irradiation
Authors: Zhu X. , Williams J.S. , McCallum J.C. 
Published: April 2011

AbstractIt has recently been shown that a band of nanocavities in crystalline silicon is eliminated during amorphization of the silicon surrounding this band [4]. In this study, we examine the effect of irradiation dose on nanocavity stability. Gettering of Au is used as a detector for open volume defects following annealing of irradiated samples. Rutherford backscattering and channeling and cross-sectional transmission electron microscopy have been used to analyse the samples. Cavities are only completely removed when the region surrounding the cavities is totally amorphized up to the surface. Partial amorphization leaves residual open volume defects.
Effect of Electron Beam Irradiation-Enhanced Diffusion on A W-Aluminum Oxide-Ti/Cu Multilayer
Authors: Ohta S. , Takahashi H. 
Published: April 2011

AbstractTungsten, aluminum oxide and Ti films were deposited onto a Cu substrate by means of a rf magnetron sputtering method. TEM thin foils for cross-sectional irradiation were prepared using a focused ion beam (FIB). Electron irradiation was carried out in a Hitachi H- 1300 electron microscope at I MV. The specimen temperatures during irradiation were 300, 473, 623 and 703K. The phases of W, aluminum oxide and Ti films were identified from selected area diffraction patterns as bcc, amorphous and hcp phases, respectively. The phases of W and Ti did not change due to irradiation. However, the amorphous aluminum oxide phase transformed to crystalline γ-Aluminum oxide. Electron irradiation caused no change in the composition of the interface of W/aluminum oxide, but diffusion was enhanced on the interfaces of aluminum oxide/Ti and Ti/Cu.
Radiation-Induced Defects in Electron and Proton Irradiated ZnS
Authors: Brunner S. , Puff W. , Mascher P. , Balogh A.G. 
Published: April 2011

AbstractIn this contribution, we present a study aimed at investigating the microstructural changes of ZnS single crystals and CVD (chemical vapour deposition) grown crystals after electron and proton irradiation. Positron lifetime and Doppler-broadening measurements were performed to investigate the stability of the radiation induced defects and possible clustering mechanisms during isochronal annealing. After electron as well as proton irradiation the significant changes in the annihilation characteristics are indications of radiation induced open-volume-type defects. It is found that electron and proton irradiation causes different changes in the positron annihilation characteristics. After electron irradiation a significant defect component is observed which can be attributed to the annihilation in monovacancies. During isochronal annealing agglomerations to divacancy-type defects take place. Proton irradiation reveals a significantly different defect structure. Isochronal annealing causes agglomerations to larger defect complexes. The observed annealing stages are indications of the annealing of variously sized vacancy complexes.
Measurement and Modelling of the Radiation Damage of Silicon by MeV Ag Ions
Authors: Lindner Jörg K.N. , Eder Johann , Stritzker Bernd 
Published: April 2011

AbstractDepth profiles of the radiation damage produced by 4 MeV Ag ions in Si(111) at temperatures of 210-450 K are studied by optical reflectivity depth profiling and TEM for doses between 1012 and 1015 Ag/cm2. For high implantation temperatures, the depth of maximum damage is shown to be dose dependent. Point defect diffusion is shown to result in long tails of defect depth profiles. High-temperature amorphization is observed to proceed via the formation and bridge-like coalescence of isolated amorphous volumina. The damage at the depth of the maximum in the nuclear stopping power is described as a function of dose and temperature by the Hecking model. The model parameters and a comparison with those obtained for lighter ions reflect the particular properties of heavy ion collision cascades.
Amorphisation of Perovskite: the Effect of Composition and Pre-Existing Cation Vacancies
Authors: Smith Katherine L. , Lumpkin Gregory R. , Blackford Mark G. , Vance Eric R. 
Published: April 2011

AbstractEight perovskites of different compositions and pre-existing vacancy contents were irradiated with 1.5 MeV Kr+ ions using the HVEM-Tandem User Facility at Argonne National Laboratory. The critical dose of 1.5 MeV Kr+ ions for amorphisation (Dc) of NaNbO3, SrTiO3 and two natural perovskites varies with composition and may decrease with Na content. The Dc values of 5 members of the solid solution series from SrTiO3 to La0.67TiO3 do not exhibit a simple relationship with vacancy content: In particular, Dc(Sr0.7La0.2TiO3) is extraordinarily high (>170 × 1014 ions cm−2) compared to those of the other (Sr, La)-perovskites in the series, which have Dc, values between 2.4 and 11×1014 ions cm−2.
High-Resolution Electron Microscopy Studies of the Precipitation of Copper Under Neutron Irradiation in An Fe-1.3Wt%Cu Alloy
Authors: Nicol A. C. , Jenkins M. L. , Kirk M. A. 
Published: April 2011

AbstractWe have studied by electron microscopy the copper-rich precipitates in an Fe-1.3wt%Cu model alloy irradiated with neutrons to doses of 8.61 × 10−3dpa and 6.3×10−2 dpa at a temperature of-270°C. In the lower dose material a majority (ca. 60%) of the precipitates visible in high-resolution electron microscopy were twinned 9R precipitates of size ∼ 2−4 nm, whilst ca. 40 % were untwinned. In the higher dose material, a majority (ca. 75%) of visible precipitates were untwinned although many still seemed to have a 9R structure. The average angle α between the herring-bone fringes in the twin variants was measured as 1250, not the 1290 characteristic of precipitates in thermally-aged and electron-irradiated material immediately after the bcc-→9R martensitic transformation. We argue that these results imply that the bcc-→9R transformation of small (< 4 nm) precipitates under neutron irradiation takes place at the irradiation temperature of 270°C rather than after subsequent cooling. Preliminary measurements showed that precipitate sizes did not depend strongly on dose, with a mean diameter of 3.4 ± 0.7 nm for the lower dose material, and 3.0 ± 0.5 rim for the higher dose material. This result agrees with the previous assumption that the lack of coarsening in precipitates formed under neutron irradiation is a consequence of the partial dissolution of larger precipitates by high-energy cascades.
Influence of Initial Grain Boundary Composition on the Evolution of Radiation-Induced Segregation Profiles
Authors: Busby J.T. , Was G.S. , Bruemmer S.M. , Edwards D. J. , Kenik E.A. 
Published: April 2011

AbstractRadiation-induced segregation (RIS) has been identified as a potential contributor to irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels in reactor core components. The occurrence of grain boundary segregation prior to irradiation influences both the shape and magnitude of RIS profile development during subsequent irradiation. In an effort to better understand the impact of this pre-irradiation enrichment on RIS profile development, the evolution of grain boundary Cr segregation profiles with irradiation dose has been characterized. Commercial purity and high-purity austenitic stainless steels with different initial levels of grain boundary Cr have been irradiated with neutrons (at 275°C) or protons (at 360-400°C) to doses up to ∼5 dpa. Grain boundary composition profiles were measured before and after irradiation using scanning transmission electron microscopy with energy dispersive xray spectroscopy (STEM-EDS). The initial enrichment of Cr is shown to delay radiation-induced Cr depletion and produce a “W-shaped” profile at low irradiation doses. Further irradiation causes the central peak of the W to decrease, eventually resulting in the classical “V-shaped” depletion profile. Possible mechanisms for the pre-irradiation enrichment and its evolution into a “W-shaped” profile will be discussed.
Li-Defect Reactions During Low Dose Ion Implantation of 8LI into ZNSE Single Crystals
Authors: Restle M. , Dalmer M. , Wahl U. , Hofsäss H. 
Published: April 2011

AbstractWe present lattice site location and diffusion studies of ion implanted 8Li in ZnSe single crystals at sample temperatures between 180 K and 550 K using the emission channeling technique. Below 200 K, Li is immobile in ZnSe and occupies tetrahedral interstitial sites. Above 250 K, interstitial Li becomes mobile and for an accumulated dose above 1×1012 cm-2 the majority of the implanted Li atoms occupy substitutional sites, presumably Zn sites. However, for room temperature implantation at doses below 1×1012 cm-2, the majority of implanted Li still occupies interstitial sites. This behavior is explained by recombination processes between Zn interstitials and vacancies, thus reducing the vacancy concentration and maintaining a high fraction of interstitial Li. Substitutional Li is stable up to about 500 K and diffuses out for temperatures above. We calculate 0.5 eV for the migration energy of interstitial Li and 1.38 eV for the binding energy of substitutional Li.
Post-Irradiation Annealing of Dislocation Microstructure and Radiation-Induced Segregation in Proton-Irradiated Stainless Steels
Authors: Busby J.T. , Was G.S. , Kenik E.A. 
Published: April 2011

AbstractBoth microstructural effects (radiation hardening) and microcompositional effects (radiationinduced segregation (RIS)) have been identified as potential contributors to irradiation-assisted stress corrosion cracking (IASCC). However, the importance of each in IASCC is unclear. In an effort to isolate their roles, post-irradiation annealing of proton-irradiated 304L stainless steel samples has been studied. Model simulations of post-irradiation annealing at intermediate temperatures (400-650°C) indicate that microstructural features such as dislocation loops are removed faster than RIS. Simulations also predict that there exist time-temperature combinations that will significantly reduce the dislocation loop population while leaving the grain boundary segregation essentially unaffected. Ultra-high purity (UHP) 304L stainless steel samples have been irradiated with 3.2 MeV protons at 360°C to 1.0 dpa and then annealed in-situ as thinned TEM disks in the temperature range of 500°C- 625°C for times between 20 and 60 minutes. RIS and dislocation loops were characterized before and after annealing in the same areas of each specimen. Post-irradiation anneals at 500TC for 45 minutes or 60 minutes resulted in no appreciable change in dislocation loop population or RIS. Annealing at 600°C for 20 minutes., or 40 minutes and at 625°C for 40 minutes, resulted in decreasing dislocation loop densities and increasing loop size with increasing annealing time or temperature, while the amount of RIS did not change significantly from the pre-annealed condition.
Fabrication of a Simple Materials System for Study of Hg in a Stainless Steel
Authors: Allen Charles W. , Mccormick Anthony W. , Kestel Bernard J. , Baldo Peter M. , Zaluzec Nestor J. , Rehn Lynn E. 
Published: April 2011

AbstractThe Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory, is expected to employ a Hg target encased in a stainless steel. Little is known about the metallurgical behavior of this materials engineering system, which will occur in a service environment involving elevated temperatures and intense radiation. Under normal equilibrium conditions, however, Hg is known to be insoluble in and non-reactive with solid Fe and Cr but to form one or more intermetallics with Ni. Hg has been implanted into alloy 304L. After implantations at 400 and 500 °C to a fluence of 3×1016 cm−2 sub-micron sized precipitates of Hg are formed, as judged, for example, from their solidification behavior on cooling during TEM observation. The formation of such a system of microtargets and possible studies employing them as in situ TEM specimens are discussed, which can provide useful empirical information in conjunction with SNS target development.
Fracture Toughness and Internal Friction of GlidCop®Al-25 Alloy
Authors: Tähtinen S. , Pyykkönen M. , Smuk S. , Hänninen H. , Jagodzinski Y. , Tarasenko O. 
Published: April 2011

AbstractFracture toughness was found to decrease rapidly with increasing temperature in dispersionstrengthened GlidCop®Al-25 copper alloy both in the as-supplied condition and neutron irradiated to a dose of 0.3 dpa. Internal friction study revealed two-component peak. Grain-boundary sliding was recognized to be responsible for the low-temperature component of the peak, which disappears after irradiation and restores after the heating above 900 K. This points out that the changes in the particle — grain boundary interaction, apparently, due to the defects at the interfaces produced by irradiation are responsible for the drop of fracture toughness in A125 alloy.
Comparison Between 590 Mev Proton Irradiation and Neutron Irradiation on the F82H Ferritic/Martensitic Steel
Authors: Schäublin R. , Victoria M. 
Published: April 2011

AbstractThe microstructure of the low activation F82H ferritic/martensitic steel, which is a candidate for future fusion reactor first wall, has been studied in order to determine the differences between 590 MeV proton irradiations and fission neutron irradiations. A range of doses and temperatures are investigated. The present work focuses on the microstructure of irradiation induced defect clusters for cases of proton irradiations to doses up to 1.7 dpa, and for neutron irradiation to a single dose of 2.5 dpa. The irradiation temperatures were 40°C and 250°C in the case of the proton irradiation and 250°C in the case of the neutron irradiation. In the case of the proton irradiation no defects are observed in the transmission electron microscope in the case of the 0.45 dpa dose, while they start to be clearly visible for doses higher than about 1.0 dpa. In the case of the neutron irradiation a high density of defects and small loops is evidenced. These preliminary results are presented here.
Time and Space Instabilities in Binary Alloys at Phase Transitions Under Irradiation
Authors: Mikhailovskiy V. V. , Russell K. C. , Sugakov V. I. 
Published: April 2011

AbstractA manifestation of antisite defects created by nuclear irradiation in binary ordered alloys is investigated. Calculations show that the concentration of such defects can be large at typical values of intensity of irradiation and temperature. The appearance of structural defects can cause the time and space instabilities in crystal during irradiation. Time instabilities are connected with the acceleration of antisite defect relaxation due to the heat that is released during this relaxation. The instability leads to appearance of self-oscillations of defect density and temperature of crystal. Space instability arises due to interaction between defects created by irradiation. It leads to spatial periodical modulation of antisite defect density.
Glissile and Sessile Vacancy and Self-Interstitial Clusters in BCC and FCC Metals
Authors: Osetsky Yu.N. , Gao F. , Bacon D.J. 
Published: April 2011

AbstractThe production bias model of radiation damage has focused attention on the production of glissile clusters (GCs) in the displacement cascades. The formation of glissile SIA clusters in molecular dynamics simulations of cascades has been reported frequently whereas information about sessile clusters (SCs) is rather sparse. Comprehensive models of microstructure evolution in metals under irradiation conditions should include all possible defects (and clusters) and interactions between them. Detailed information of this nature can be obtained by means of atomic-scale computer simulation. In the present paper we review some recent results of atomistic simulation of sessile and glissile defect clusters in metals, dealing with their mechanisms of formation and their properties. In particular, we discuss the formation of SCs and GCs in the cascade region and also their creation in bulk metal as a result of cluster growth.
Monte Carlo Investigation of Cascade Damage Effects in Metals Under Low Temperature Irradiation
Authors: Barashev A.V. , Bacon D.J. , Golubov S.I. 
Published: April 2011

AbstractThe Monte Carlo (MC) method is used to study cascade damage effects in damage accumulation in pure metals at temperatures below stage III, when vacancies and their clusters are immobile. The irradiation is modelled by sequential introduction of collections of defects representing the primary damage state of cascades placed randomly in the simulation volume. The cascades generated in molecular dynamics simulations for recoil energies from 2 to 20keV are used. Concentrations of point defects as well as defect cluster densities are monitored as a function of dose up to 0.02dpa. The results are compared with those obtained in the mean-field approximation. Factors responsible for the difference in damage accumulation under homogeneous and cascade irradiation conditions are revealed. The effects of temperature and recoil energy are studied. Problems in MC modelling of one-dimensional diffusion of interstitial clusters connected with the limited volume of the simulation box are revealed.
Rigidity Constraints in Amorphization of Multiply-Polytopic Multiply-Connected Ceramic Structures
Authors: Hobbs Linn W. , Jesurum C. Esther , Bergert Bonnie 
Published: April 2011

AbstractThe ease with which ceramic structures amorphize under displacive radiation is considered from the point of view of connectivity and the consequent topological constraints which impose rigidity on the original atomic arrangement. These constraints define a measure of topological freedom to rearrange which has been shown previously to correlate with measured energy deposition density during ion-induced amorphization. That earlier assessment of topological freedoms is extended here to include more complex connectivities and is shown to be representable in an analytical form which reflects the progressive destruction of topological constraints.
A Raman Scattering, Ion Channelling and Photoluminescence Study of Argon Ion Radiation Damage in Cu(Ga,In)Se2 - Dose Dependence and Dose Rate Effects
Authors: Lippold G. , Weinert K. , Yakushev M.V. , Pilkington R.D. , Otte K. , Grill W. 
Published: April 2011

AbstractThe ternary chalcopyrite semiconductor CuInSe2 and related ternary compounds are promising materials for the production of high-efficiency thin film solar cells. In this paper we study the dose dependence of ion radiation damage produced by 30 keV and 80 keV Ar ions in single crystals and polycrystalline films of Cu(In,Ga)Se 2 over a wide dose range from 1012 to 1017 cm-2, using Raman spectroscopy and ion channeling measurements. For the first time, we also report on the dose rate dependence with a variation of the beam current density in the range 0.44 to 44 µcm-2. Even for low damage levels no significant dependence of the defect concentration or damage mechanism on the dose rate could be observed. From phonon correlation length considerations we estimate defect densities. They are in agreement with ion channeling data obtained in the 1015 to 1016 dose range, where the breakdown of the lattice structure occurs. In this dose range, the defect density is close to the concentration of implanted atoms. We conclude, that this high impurity concentration is responsible for the amorphization.
Solid Freeform Fabrication using Alumina-Poly(Vinyl Alcohol) Gel-Casting Suspensions
Authors: Morissette S. L. , Lewis J. A. , Cesarano J. , Dimos D. B. 
Published: April 2011

AbstractSolid freeform fabrication of aqueous alumina (Al2O3)-poly(vinyl alcohol) (PVA) gelcasting suspensions was carried out using a computer-controlled extrusion apparatus fitted with a two-nozzle delivery system. The impact of casting parameters (e.g., tip diameter, mixing rate, etc.) and suspension composition on line resolution/uniformity, printability, and as-cast component properties was probed using laser profilometry and optical microscopy. Line uniformity depended on mixing rate (Rmix) and tip diameter (td) for the chamber and paddle geometry utilized. These data were used to establish processing maps that identify optimal print conditions for varying suspension composition.
Direct Ink-Jet Deposition of Ceramic Green Bodies: I - Formulation of Build Materials
Authors: Seerden K. A. M. , Reis N. , Derby B. , Grant P. S. , Halloran J. W. , Evans J. R. G. 
Published: April 2011

AbstractA conventional rapid prototyping technology has been used to build prototypes using direct deposition through a drop-on-demand ink-jet printing system. Al2O3- filled waxes have been developed with viscosity values close to those of the materials used in commercial printing systems. Commercial dispersants based on stearic acid and sterylamine have been studied and stable ceramic suspensions with ceramic volume fractions in the range 20–40 volume% produced with suitable viscosity. A suspension of 20% Al2O3in an alkane wax has been successfully printed.