bluuebunny/crossref_metadata_2025_split huggingface dataset:
Damage Evolution in Xe-Ion Irradiated Rutile (TiO2) Single Crystals
Authors: Li Fuxin , Lu Ping , Sickafus Kurt E. , Evans Caleb R. , Nastasi Michael 
Published: April 2011

AbstractRutile (TiO2) single crystals with (110) orientation were irradiated with 360 keV Xe2+ ions at 300K to fluences ranging from 2×1019 to 1×1020 Xe/m2. Irradiated samples were analyzed using: (1) Rutherford backscattering spectroscopy combined with ion channeling analysis (RBS/C); and (2) cross-sectional transmission electron microscopy (XTEM). Upon irradiation to a fluence of 2×1O19 Xe/m2, the sample thickness penetrated by the implanted ions was observed to consist of three distinct layers: (1) a defect-free layer at the surface (thickness about 12 nm) exhibiting good crystallinity; (2) a second layer with a low density of relatively large- sized defects; and (3) a third layer consisting of a high concentration of small defects. After the fluence was increased to 7×1019 Xe/m2, a buried amorphous layer was visible by XTEM. The thickness of the amorphous layer was found to increase with increasing Xe ion fluence. The location of this buried amorphous layer was found to coincide with the measured peak in the Xe concentration (measured by RBS/C), rather than with the theoretical maXimum in the displacement damage profile. This observation suggests the implanted Xe ions may serve as nucleation sites for the amorphization transformation. The total thickness of the damaged microstructure due to ion irradiation was always found to be much greater than the projected range of the Xe ions. This is likely due to point defect migration under the high stresses induced by ion implantation.
Effect of Stress and Impurities on Preferential Amorphization on Grain Boundaries in Polycrystalline Silicon
Authors: Takeda Mitsuhiro , Ohnuki Somei , Watanabe Seiichi , Abe Hiroaki , Naramoto Hiroshi , Okamoto Paul R. , Lam Nigh Q. 
Published: April 2011

AbstractClarifying the local amorphization on the grain boundaries, the in-situ observation during ion-irradiation was carried out for poly-crystalline Si film. The critical dose of amorphous formation increased exponentially with increasing temperature, where the local amorphization was developed at middle temperature. The critical dose was affected by the doped impurity and the grain size. The preferential amorphization on and near grain boundaries had two processes; first stage with rapid growth rate and second stage with almost constant growth rate. The importance of stress was demonstrated from the acceleration due to the stress on the first stage of amorphization.
Exploring the Excited States of Vacancy Defects in Silica
Authors: Song J. , Corrales L. R. , Jònsson H. 
Published: April 2011

AbstractA study of vacancy defect formation is carried out using a density functional theory molecular dynamics simulation methodology. The objective is to study the effects of electronic excitations in crystalline and non-crystalline silica polymorphs. We present an initial study focusing on the formation energetics of distinct oxygen vacancy defect states in α-quartz.
Radiation Effects in Zircon, Hafnon, and Thorite: Implications for Pu Disposal
Authors: Meldrum A. , Zinkle S.J. , Boatner L.A. , Wu M. , Mu R. , Ueda A. , Henderson D.O. , Ewing R.C. 
Published: April 2011

AbstractSynthetic ZrSiO4, HfSiO4, and ThSiO4 single-crystal specimens were irradiated by 800 keV Kr+ ions, and the microstructural evolution was observed in-situ in a transmission electron microscope. All three compounds were found to become amorphous up to temperatures in excess of 600°C. Using a new model, the activation energies for annealing were found to be in the range of 3.1 to 3.6 eV for these compounds. At temperatures above 600°C, the orthosilicates were observed to decompose into the component oxides (e.g., tetragonal ZrO2 + amorphous SiO2 in the case of zircon). A single-crystal zircon specimen was also irradiated with a pulsed picosecond Nd:YAG laser operated at 355 nm, and the resulting microstructure was investigated by optical absorption, SEM, AFM, and TEM techniques.
Anomalous Small-Angle X-Ray Scattering Characterization of Model Pressure Vessel Alloy Microstructures
Authors: Alexander Dale E. , Kestel B. J. , Jemian P. R. , Odette G. R. , Klingensmith D. , GRAGG D. 
Published: April 2011

AbstractAnomalous small-angle x-ray scattering (ASAXS) experiments were performed at energies near the Mn-K and Fe-K absorption edges on an Fe-0.9 Cu wt.%-1.0 Mn wt.% alloy subjected to either annealing at 450°C, 24 hrs or irradiation with 10 MeV electrons to 0.5 mdpa at 300°C. A Guinier analysis of the net scattered intensity revealed scatterers with radii of 16.5.16.8 Å and 16.4.17.3 Å for the irradiated and annealed foils, respectively. The variation in net scattered intensity with photon energy in the annealed sample was consistent with scattering contrast variations expected for Cu-rich, Cu-Mn precipitates. Minimal variation in net intensity (scattering contrast) with energy determined that Cu-Mn precipitates were not detected in the irradiated sample.
Microchemistry of Proton-Irradiated Austenitic Alloys Under Conditions Relevant to Lwr Core Components
Authors: Was G. S. , Allen T. R. , Busby J. T. , Gan J. , Damcott D. , Carter D. , Atzmon M. , Kenik E. A. 
Published: April 2011

AbstractOver 1200 measurements of grain boundary composition and microstructure have been made on 14 different austenitic Fe-Cr-Ni alloys following proton irradiation in the temperature range 200-600°C and in the dose range 0.1-3.0 dpa. Grain boundary composition measurements revealed that Cr depletes at grain boundaries, Ni enriches and Fe can either enrich or deplete depending on alloy composition. Analysis of temperature and composition dependence of RIS revealed that the magnitude and direction of grain boundary segregation depends on alloy composition because the value of migration enthalpy differs among the alloy constituents, and diffusivities of the alloy constituents are composition-dependent. The dose dependence of segregation revealed ordering in Ni-base alloys and temperature dependence was used to show that RIS occurs by vacancy exchange rather than an interstitial binding mechanism. The dependence of segregation on composition is consistent with all known, relevant neutron data.
The Effect of Low Dose-Rate Irradiation on the Microstructure of 304 Stainless Steel
Authors: Cole J. I. , Allen T. R. 
Published: April 2011

AbstractChanges in mechanical and corrosion properties caused by the development of radiation-induced microstructures have relevance to the aging and lifetime extension of light water reactors (LWR‘s). However, much of the current data related to microstructural development in irradiated metals are generated from studies carried out at much higher dose-rates than encountered in LWR‘s. An opportunity exists to study the influence of low dose-rate irradiation on microstructural development for a variety of structural and surveillance materials extracted from the experimental breeder reactor EBR-lI. In this study, irradiated 304 stainless steel hexagonal “hex” duct material is examined in order to compare microstructures in the dose-rate range of 10−7 - 10−9 dpa/sec. The samples, taken from the reflector locations in EBR-II, experienced a total dose between 10 and 12 dpa at a temperature of ∼375 °C. Transmission electron microscopy (TEM) analysis reveals that there is a moderate dose-rate effect on microstructural development for samples irradiated in the range of 2 × 10−8 to 4 × 10−8. dpa/sec, however a substantial dose-rate effect exists between dose-rates of 2 × 10−8 and 1 × 10−9 dpa/sec Results detail the development of the microstructure in terms of radiation-induced cavities, dislocations, and precipitates.
Origin and Influence of Pre-Existing Segregation on Radiation-Induced Segregation In Austenitic Stainless Steels
Authors: Kenik E. A. , Busby J. T. , Miller M. K. , Thuvander A. M. , Was G. 
Published: April 2011

AbstractThe pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.
Dissolution of Copper Precipitates in An Fe−1·3Wt%Cu Alloy Under Fe+ Ion Irradiation
Authors: Nicol A. C. , Jenkins M. L. , Wanderka N. , Abromeit C. 
Published: April 2011

AbstractThe stability of Cu precipitates in an Fe-1.3wt%Cu alloy under 300 keV Fe+ion irradiation has been investigated using transmission electron microscopy and high-resolution electron microscopy. The irradiations were carried out between room temperature and 550°C at displacement rates of 103 to 10−2 dpa(s)−1 to fluences of up to 30 dpa. Copper precipitates were found to keep their shape but decrease in size under all irradiation conditions. The results are discussed within the framework of a competitive process between irradiation induced ballistic destruction of precipitates by cascades and irradiation-enhanced precipitation.
Modeling the Post-Yield Flow Behavior After Neutron and Electron Irradiation of Steels and Iron-Base Alloys
Authors: Dimelfi R.J. , Alexander D.E. , Rehn L.E. 
Published: April 2011

AbstractIrradiation hardening is an issue of practical importance as it relates to the remanent life and the nature of failure of reactor components exposed to displacement-producing radiation. Understanding these phenomena requires studies of fundamental microstructural mechanisms of hardening. In this paper, we analyze the tensile behavior of pressure vessel steels (A212B and A350) irradiated by neutrons and electrons. The results show that the post-yield true stress/true strain behavior can provide fingerprints of the different hardening effects that result from irradiation by the two particles, which suggests correspondingly different hardening microstructures for the two particles. Microstructurally-based models for irradiation-induced yield strength increases, combined with a model for strain hardening, are used to make predictions of the different effects of irradiation by the two particles on the entire flow curve that agree well with data.
Examination of Neutron-Irradiated Pressure-Vessel Steel Using Positron Annihilation Lifetime Spectrosopy
Authors: Cumblidge Stephen E. , Motta Arthur T. , Catchen Gary L. 
Published: April 2011

AbstractOn a variety of pressure-vessel (PV) steels, we have observed changes in the average positron lifetime with increasing (near end-of-life) neutron fluences. Samples were irradiated at reactor-temperature and subjected to post-irradiation annealing, and they were examined using positron annihilation lifetime spectroscopy (PALS). The measured average positron lifetimes in high-temperature (2900 C-300° C) irradiated PV steels decrease with increasing neutron damage up to fluences of 8.5×1018 cm−2 and increase again at higher fluences. Annealing of high-fluence, 300° C irradiated ASTM A508 PV steel samples produces an initial decrease in average positron lifetimes with increasing annealing temperatures of up to 400° C, followed by an increase in average positron lifetime with higher annealing temperatures, when samples were annealed in successive 24-hour steps. A sample of weld steel, irradiated to 2.2×1019 cm−2 at 290° C, shows similar behavior in which the minimum lifetime occurs at ≈ 450° C. These trends are similar to those seen in previous studies performed on VVER and other ferritic steels.
A Comparison of the microstructure and tensile behaviour of irradiated fcc and bcc metals
Authors: Baluc N. , Bailat C. , Dai Y. , Luppo M.I. , Schaublin R. , Victoria M. 
Published: April 2011

AbstractAs part of an on-going research program, findings are presented from a comparison of the microstructures and associated tensile properties of fcc and bcc materials after high energy proton irradiation, to fluences between 10−4 and 1 dpa, at 300-320 K. Results for this comparison between Cu, Pd, 304 and 316 stainless steel on one side and Fe and the F82H ferritic-martensitic low activation steel on the other are discussed, showing a strong difference in defect accumulation behaviour between the differing crystal structures. The overall deformation behaviour is similar, with an initial localised deformation taking place in all cases, even though the actual deformation mode itself might be different. Furthermore, a comparison is made with some of the materials that have also been irradiated with fission neutrons, showing no influence of the PKA spectra for these irradiation conditions.
From Molecular Dynamics to Kinetic Rate Theory: A Simple Example of Multiscale Modeling
Authors: Stoller Roger E. , Greenwood Lawrence R. 
Published: April 2011

AbstractRadiation damage formation in iron has been investigated using the method of molecular dynamics simulation. The MD simulations have been used to determine primary defect production parameters for cascade energies up to 50 keV at temperatures from 100 to 900K. The energy dependence of these parameters has been used to determine appropriate neutron-energy- spectrum averaged damage production cross sections for various irradiation environments. Two applications of these effective cross sections are discussed. The first is an evaluation of neutron energy spectrum effects in commercial fission reactor pressure vessels. The second example deals with the use of these cross sections in the source term of a kinetic model used to predict void swelling and microstructural evolution. The simulation of the primary damage event by MD involves times less than 100 ps and a size scale of a few tens of nm, while the kinetic simulation encompasses several years and macroscopic sizes. This use of the MD results to develop an improved source term for rate theory modeling provides a simple example of multiscale modeling.
Exploring The Use of Pulsed Irradiations for Studying the Transient Sink Formed by Cascade Producing Radiation
Authors: Alexander Dale E. 
Published: April 2011

AbstractAn approach is suggested for using pulsed irradiation experiments to study attributes of the transient sink formed by cascade producing radiation. As an example, a simple model of radiation enhanced diffusion is proposed for a dual ion beam irradiation in which one of the beams is a pulsed, sink-producing heavy ion. It is demonstrated that by combining this model with diffusivity measurements evaluated as a function of the irradiation pulse wavelength, it is possible to quantitatively determine the transient sink strength and its characteristic lifetime.
On The Mechanism of Interstitial Cluster Migration in α -FE
Authors: Barashev A.V. , Osetsky Yu.N. , Bacon D.J. 
Published: April 2011

AbstractRecent molecular dynamics (MD) computer simulations have shown that clusters consisting of up to a few tens of self-interstitial atoms (SIAs) are highly mobile along closed-packed crystallographic directions in pure copper and iron. This effect has important consequences for microstructure evolution in irradiated metals and so it is desirable to investigate the mechanisms of the cluster motion. In the present paper the results of MD modelling of the thermally-activated motion of clusters of 3, 9 and 17 SIAs in α-Fe in the temperature range from 90 to 1400 K are analyzed. The extensive MD data has enabled the migration of clusters, as well as that of individual SIAs in the clusters, to be treated with high statistical accuracy. The correlation between the motion of the centre of gravity of a cluster and the jumps of individual SIAs in the cluster is revealed. It is found that the SIAs in a cluster jump almost independently and their jump frequency depends on the number of SIAs in the cluster. This leads to a simple relationship between the jump frequency of a cluster and the number of SIAs in it. The cluster jump frequency exhibits a deviation from the Arrhenius relationship. The reason for this is discussed.
Solid Freeform Fabrication of Composites by Direct Deposition and by In Situ Mineralization
Authors: Calvert Paul , Peng Jiong , Souvignier Chad 
Published: April 2011

AbstractFreeform fabrication methods build materials by the repetitive addition of thin layers. This approach can be applied to build parts from epoxy resin which is modified with a gelling agent to solidify the material until curing occurs. High strength and stiffness parts can be obtained through fiber reinforcement but the fiber content is limited by packing effects. We have found that a combination of two types of fibers can be used to achieve higher strength and stiffness than can be obtained from a single fiber type.An alternative route to reinforcement is to form the reinforcing phase after the material is deposited by an in situ reaction. This approach has been applied to the use of freeform fabrication to make bars of mineralized gel and of methacrylate-silica hybrids. Good mechanical properties can be attained in each case, with up to 50 vol.% inorganic phase and bend strengths in the range from 50-100 MPa.
Investigation on Morphology and Microstructure of the SALD SiC
Authors: Sun Lianchao , Crocker James E. , Shaw Leon L. , Marcus Harris L. 
Published: April 2011

AbstractIn this work, the deposition of silicon carbide lines using a tetramethylsilane (TMS) precursor was investigated. Effects of target temperatures on the morphology and crystal structure of the deposits were examined. It was found that the morphology of the SALD SiC depends strongly on the target temperature. The contour of the cross section of the SiC deposits changes from a triangle to trapezoid to volcano shape and the surface morphology of the deposited lines changes from smooth to rough to porous as the target temperature increases. A critical target temperature was found to be about 700°C to initiate deposition of SiC under the current experimental configurations. X-ray diffraction analyses show that the SALD SiC formed at 1000°C contains both crystalline and amorphous phases. The results are briefly discussed.
Modification of Thermoelectric Properties Using Insertion Techniques
Authors: Hatzikraniotis E. , Kyratsi Th. , Chrissafis K. , Paraskevopoulos K. M. 
Published: April 2011

AbstractIn this work is presented the application insertion techniques for the modification of the performance of thermoelectric materials. The results indicate that in cases as in Bi2Se3 compounds where insertion of foreign species in the lattice is possible due to its particular crystal structure, the insertion technique could be proved a valuable easy to apply and cost effective, alternative to doping technique. The techniques can produce homogeneous materials with electronic and thermoelectric properties finely tuned.
Iron Disilicide as a Base for New Improved Thermoelectrics Creation
Authors: Fedorov M. I. , Ivanov Yu. V. , Vedernikov M. V. , Zaitsev V. K. 
Published: April 2011

AbstractIt is well known that the temperature dependence of Seebeck coefficient of β-iron disilicide has unusual shape that cannot be described by an ordinary theory. A theory describing such a shape is suggested. It is shown this shape can be explained by optical phonon drag effect. Very high value of ZT could be achieved in some material on the base of this effect.
Thermoelectric Transport Properties of ReSi1.75 Thin Films
Authors: Kleint C. A. , Heinrich A. , Griessmann H. , Hofmann D. , Vinzelberg H. , Schumann J. , Schlaefer D. , Behr G. , Ivanenko L 
Published: April 2011

AbstractEpitaxial ReSi1.75 thin films of variable thickness between 15nm and 150nm have been prepared in an one step process by Facing Target Sputtering (FTS) onto heated (100) and (111)Si and SOS wafers. The epitaxial relations and film structure have been investigated by Xray diffraction and transmission electron microscopy. Epitaxial growth was found at a substrate temperature of 1070K. Thermoelectric properties were measured between 100K and 450K and compared to the transport behavior of bulk ReSi1.75 and polycrystalline films. A distinct dependence of both the conductivity and thermopower was found on the film thickness, on unintentional doping and on the film structure. The results show that epitaxial ReSi1.75 films prepared by FTS can be a basis for further investigations of thermoelectric silicide/silicon multilayers.
Thermoelectric and Structural Properties of Bi1-xTe1+x Thin Films on CdTe(111)
Authors: Kim Yunki , Cho Sunglae , DiVenere Antonio , Wong George K. , Meyer Jerry R. , Ketterson John B. 
Published: April 2011

AbstractThin films of the hexagonal phase of Bi1-xTe1+x have been grown on CdTe(111) substrates using molecular beam epitaxy (MBE). Analysis of X-ray diffraction patterns (θ-2θ scans and rocking curves) of the films shows that their crystallinity depends upon the compositional deviation from stoichiometric BiTe. Measurements of the temperature-dependent thermoelectric power (TEP) of the films reveals that compositional changes cause the TEP to vary from electron dominant (n-type) to hole dominant (p-type), implying their possible application as a thermoelectric cooler or power generator. Measurements of the temperature-dependent resistivity of the films were conducted, and the analysis shows semimetallic behavior. These results demonstrate that Bi1-xTe1+xis an appropriate model system to study the dependencies of thermoelectric and structural properties on binary composition.
Mbe Growth and Thermoelectric Properties OF Bi2Te3 Thin Films
Authors: Cho Sunglae , Kim Yunki , DiVenere Antonio , Wong George K. L. , Meyer Jerry R. , Ketterson John B. 
Published: April 2011

AbstractWe have grown high quality Bi2Te3 thin films on CdTe(111)B substrates using MBE. Structural properties have been investigated using in-situ reflection high-energy electron diffraction (RHEED) and θ-2θ X-ray diffraction analysis. They show that Bi2Te3films on CdTe(111) grow along the (00.l) in the hexagonal cell with a layer-by-layer growth mode, resulting in a smooth surface, and an X-ray Bragg peak FWHM of 0.2°. The thermopower and electrical conductivity of the stoichiometric Bi2Te3 films were ∼200 μV/K and 103(Ωcm)−1, respectively, comparable to the single crystal bulk values. We have observed the antisite defect effect in Te-rich Bi2Te3films: excess Te occupies Bi lattice sites and behaves as an n-type dopant. Crystallinity and transport properties are strongly affected by non-stoichiometry.
Thermal Conductivity of Fe-Doped Cosb3 Skutterudites
Authors: Stokes Kevin L. , Ehrlich A. C. , Nolas G. S. 
Published: April 2011

AbstractWe investigate the effect of Fe substitution for Co on the lattice thermal conductivity of CoSb3 skutterudites. The polycrystalline materials are formed from uniaxially hot-pressed powders. Three alloys were prepared with 0, 3% and 10% Fe, respectively. Thermal conductivity measurements were made between 80 K to 450 K. The lattice thermal conductivity of 10%Fe:CoSb3 is approximately two times smaller than the lattice thermal conductivity of CoSb3 over the entire temperature range. This effect cannot be accounted for by the phenomenlogical theory considering only the mass difference and strain field due to the alloying (Fe) atom. Other phonon scattering mechanisms are discussed. Comparison is made with the partially-filled skutterudite alloy, La0.65Fe2.8Co1.1Sb12.