bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Radiation-Induced Alteration of the Network Structure of Alkali Borosilicate High-level Waste Glass
Authors: Dewan Leslie , Hobbs Linn W. , Delaye Jean-Marc 
Published: April 2011

ABSTRACTHigh-level nuclear waste glasses are subject to radiation-induced degradation over very long time scales. In such glasses, bond-breakage and atom displacements occur by both radiolysis (principally from energetic beta-decay electrons) and ballistic mechanisms involving collision cascades initiated by energetic fission nuclei and recoil of alpha-emitting actinide nuclei [1]. This study investigates collision-cascade-induced alteration of the glass network in a simplified sodium borosilicate model nuclear waste glass, using molecular dynamics (MD) codes and efficient topological assessment algorithms. Collision cascades were initiated ballistically (4 keV initial kinetic energy, dissipated elastically) and carried out using MD codes incorporating both two-body Buckingham and three-body Stillinger-Weber potentials verified in the GULP atomistic simulation package. Network topologies of the initial and resulting altered glass structures were determined by enumerating the primitive-ring-based local cluster atom complement at each atom site. The topological description is seen to provide a revealing assessment of network structural changes in the simulated radiation environment that can be potentially related to observable macroscopic changes, such as swelling, viscosity changes, and radiation-induced devitrification.
The Effect of Grain-Boundary and Matrix Precipitates on High Temperature Strength in Fe3Al Based Alloys
Authors: Makihara Ryo , Kobayashi Satoru , Takasugi Takayuki 
Published: April 2011

ABSTRACTThe effect of grain boundary (GB) and matrix precipitates on high temperature strength was investigated in Fe3Al base alloys containing Cr, Mo and C. Tensile tests were conducted at 600°C for three types of microstructures consisting of: (I) film-like κ phase precipitates covering GBs and fine M2C particles in the matrix, (II) only fine M2C particles in the matrix and (III) no second-phase particles in the matrix. It was found that κ films on GBs are more than twice as effective as finely dispersed M2C particles for improving the proof stress.
The Formation of A2/L21 Microstructure in Fe-Al-Ti-Cr Alloys
Authors: Hotta Suguru , Kobayashi Satoru , Takasugi Takayuki 
Published: April 2011

ABSTRACTThe composition areas of the A2/L21 two-phase field in the Fe-Al-Ti-Cr quaternary system at 800 ºC and 700 ºC were investigated using a diffusion-multiple (DM) technique for which Fe-30Al-7Ti, Fe-30Cr-7Ti and Fe-7Ti alloys were diffusion-coupled and heat-treated. The A2/L21 two-phase field was found to expand slightly toward lower Al content when the Cr content is increased. The field is slightly shifted toward lower Al content when the temperature is decreased.
Investigations into Demineralized Cortical Bone
Authors: Novitskaya Ekaterina , Castro-Ceseña Ana , Chen Po-Yu , Vasquez Joshua , Urbaniak Robert , Lee Steve , Hirata Gustavo , McKittrick Joanna 
Published: April 2011

ABSTRACTPartially demineralized (DM) bone is of interest due to its promising
osteointegrative properties for advanced bone grafts. Structural features of
partially DM (35 vol.%, 45 vol.% and 55 vol.% reduction), and untreated
cortical bone samples were studied by scanning electron microscopy.
Mechanical properties were investigated by compression testing in three
anatomical directions at different stages of DM. The radial direction
appears to be the stiffest and strongest bone direction for the all DM
stages.
Template-free, low temperature synthesis of binary and ternary metal oxide nanostructures
Authors: Brahma Sanjaya , Arod Pallavi , Shivashankar S.A. 
Published: April 2011

ABSTRACTWe report synthesis of some binary and ternary metal oxide nanostructures using microwave irradiation-assisted chemical synthesis, either in the presence or absence of a surfactant/structure directing agent. The method is simple, inexpensive, and yields nanoparticles of desired metal oxides in minutes, and requires no conventional templating. Nanoparticles of some functionally advanced binary/ternary metal oxides (MnO2, ZnO, CuO, ZnMn2O4 etc) have been synthesized using metal acetylacetonates as the starting precursor material and microwave as the source of energy, in a process developed in detail in our laboratory. The nanoparticle size varies from 7-50 nm. Emphasis has been placed on the synthesis of ZnO nanostructures, particularly ZnO nanoshells, which do not require any surfactant/structure-directing agent for synthesis. There is a systematic variation in the morphology of the ZnO nanostructures with variation of process parameters, such as microwave power, microwave irradiation time, type of solvents, surfactants/structure-directing agents and its type and concentration. The as-prepared powder sample may either need a very brief exposure to heat to remove the surfactant or no post-synthesis processing, and is found to be well-crystallised. Determination of their crystallinity, actual shape, and orientation was made using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
Thermodynamic Modeling and Solidification Simulation of Ti-Al-Cr alloys
Authors: Yang Y. , Bewlay B.P. , Chang Y.A. 
Published: April 2011

ABSTRACTTitanium aluminide based alloys are candidate materials for high temperature structural applications. They are typically alloyed with elements such as Nb, Ta, Mo, Cr and B for property enhancement. To understand the relationship between microstructure and alloy composition/processing condition, detailed models of phase equilibria in multicomponent Ti-Al based alloys are needed. In this work, we developed thermodynamic models for the phases in the Ti-Al-Cr system based on critically assessed binary models and ternary experimental data in literature, using the CALPHAD approach. Isothermal sections at 1200, 1150, 1000 and 800°C, and the liquidus projection, were calculated from the currently developed thermodynamic models; these are in satisfactory agreement with experimental data. Isopleths were calculated at specified Cr concentrations, and solidification paths were simulated under the Scheil conditions for a range of Ti-Al-Cr alloys. From the calculated phase diagrams and solidification paths, the effect of Cr on the microstructure of Ti-Al alloys can be understood.
Radiation Induced Cavity Formation and Gold Precipitation at the Interfaces of a ZrO2/SiO2/Si Heterostructure
Authors: Edmondson Philip D , Wang Chongmin , Zhu Zihua , Namavar Fereydoon , Weber William J , Zhang Yanwen 
Published: April 2011

ABSTRACTThin films nano-crystalline zirconia of ~ 300 nm thick were deposited on Si substrate, and the samples were irradiated with 2 MeV Au+ ions at temperatures of 160 and 400 K, up to fluences of 35 displacements per atom. The films were then studied using glancing incidence x-ray diffraction, Rutherford backscattering, secondary ion mass spectroscopy and transmission electron microscopy. During the irradiation, cavities were observed to form at the zirconia/silicon interface. The morphology of the cavities was found to be related to the damage state of the underlying Si substrate. Elongated cavities were observed when the substrate is heavily damaged but not amorphized; however, when the substrate is rendered amorphous, the cavities become spherical. As the ion dose increases, the cavities then act as efficient gettering sites for the Au. The concentration of oxygen within the cavities determines the order in which the cavities getter. Following complete filling of the cavities, the interface acts as the secondary gettering site for the Au. The Au precipitates are determined to be elemental in nature due to the high binding free energy for the formation of Au-silicides.
Nanowire Tunnel FETs - Device Structure, Transistor Dimension and Material Choice
Authors: Knoch J. 
Published: April 2011

ABSTRACTThe performance of tunnel FETs is investigated and the impact of device structure and dimension as well as the impact of the transistor material will be studied. For instance, using nanowires with thin diameter providing one-dimensional transport together with a wrap-gate device structure strongly improves the tunnel FET performance. In addition, the use of III-V type II heterostructures is a further performance booster. However, the use of III-V semiconductors with low density of states can be problematic if the device is not designed properly. Here we will give design guidelines and performance predictions of nanowire tunnel FETs based on non-equilibrium Greens functions formalism simulations.
Deep-Level Characterization of Free-Standing HVPE-grown GaN Substrates Using Transparent Conductive Polyaniline Schottky Contacts
Authors: Nakano Yoshitaka , Matsuki Nobuyuki , Lozac’h Mickael , Sakoda Kazuaki , Sumiya Masatomo 
Published: April 2011

ABSTRACTWe have investigated electronic deep levels in free-standing n-GaN substrates grown by hydride vapor phase epitaxy (HVPE), by means of a steady-state photo-capacitance spectroscopy technique, using transparent conductive polyaniline Schottky contacts. Two specific deep levels located at ~1.7 and ~3.1 eV below the conduction band were revealed to be significantly reduced compared to those in n-GaN layers grown by metal-organic chemical vapor deposition. This difference between them is probably due to extremely low concentrations of threading dislocations and residual C impurities in the HVPE-grown n-GaN substrates.
The Effect of Fine M2C (M: Mo, Cr, Fe) Particles on the Recrystallization Temperature and High Temperature Strength of Warm Rolled Fe3Al Based Alloys
Authors: Kobayashi Satoru , Takasugi Takayuki 
Published: April 2011

ABSTRACTThe effect of fine M2C particles on the recrystallization temperature and high temperature strength of warm rolled Fe3Al base alloys was investigated. Fe-27Al-1.2C-2Cr-xMo (x: 0.3, 0.9) alloys (in at.%) were arc melted, warm rolled and annealed. TEM observations have revealed that fine M2C particles were present in the alloy containing 0.9% Mo but not in the alloy with 0.3% Mo after warm rolling. The recrystallization temperature increased from 740 °C to 810 °C when the Mo content is increased from 0.3 to 0.9 due to the presence of fine M2C particles. Tensile tests conducted on annealed samples with fine sub-grained matrix have shown that the introduction of fine M2C particles is effective to enhance the proof stress at 600 °C.
AlN Nanorods synthesized by a Mechanothermal Process
Authors: Rosas G. , Chihuaque J. , Patiño-Carachure C. , Esparza R. , Pérez R. 
Published: April 2011

ABSTRACTWell-crystallized AlN nanorods have been produced by mechanical milling and subsequent annealing treatment of the milling powders (mechanothermal process). High purity AlN powders were used as the starting material. Mechanical milling was carried out in a vibratory SPEX mill for 30 h, using vials and balls of silicon nitride. The annealing treatment was carried out at 1200 ºC for 10 min. The characterization of the samples was performed by X-ray diffractometry and transmission electron microscopy (TEM). TEM observations indicated that the synthesized nanorods consisted of 30 nm in diameter and 100 nm in length. High resolution electron microscopy observations have been used in the structural characterization. AlN nanorods exhibit a well-crystallized structure. The growing direction of the nanorods is close to the [001] direction. The structural configurations have been explored through comparisons between experimental HREM images and theoretically simulated images obtained with the multislice method of the dynamical theory of electron diffraction.
Light Emitting Diode Growth on Curved Gallium Nitride Surfaces
Authors: Rodak L. E. , Lee K. , Kumbham V. , Narang V. , Hornak L. A. , Korakakis D. 
Published: April 2011

ABSTRACTIII-Nitride based Light Emitting Diodes (LEDs) are heavily pursued for various lighting applications due to the ability to engineer the emission through the visible wavelengths by controlling the alloy composition in the multi quantum well. Planar structures are characterized by a Lambertian emission pattern, however, depending on the applications in which the LED is employed, including but not limited to, general lighting, displays, and sensors, the emission profile may need to be more or less directional. As a result, there is significant interest in both improving the efficiency and controlling the emission profile of nitride based devices. Various components such as lenses and photonic crystals are used to improve light extraction and alter the emission profile while growth on semi-polar substrates is being pursued to minimize inherent polarization effects. In this work, curved Gallium Nitride (GaN) structures have been grown utilizing growth kinetics. These as-grown features do not require the extensive additional fabrication and allow for three-dimensional substrates to be employed for LED fabrication. The details of the fabrication and the optical and electrical characterization of Indium Gallium Nitride based LEDs grown on these structures is discussed.
Employing Photo-Assisted Ligand Exchange Technique in Layered
Quantum Dot LEDs
Authors: Hu Wenjia , Gao Shuai , Prasad Paras N. , Wang Jingkang , Xu Jian 
Published: April 2011

AbstractWe presented in this paper a photo-assisted ligand exchange approach whereby
light will be introduced to facilitate the replacement of oleic acid (OA)
ligand molecules over PbSe quantum dots (QDs). The ligand-exchanged QDs were
used to fabricate quantum dot light-emitting-diodes (QD-LEDs), which
outperform the devices comprising the QDs without ligand-replacement.
Nonreciprocal optical Bloch oscillations in garnet/silicon-on-insulator waveguide arrays
Authors: Kumar Pradeep , Levy Miguel 
Published: April 2011

ABSTRACTWe show that nonreciprocal Bloch-like oscillations can emerge in passive optical waveguide arrays with linearly growing effective index in the absence of loss or gain. Spectral asymmetry, a difference in propagation constants and Bloch oscillation periods in opposite propagation directions, are established by imposing different vertical spatial index gradients at the substrate/core, and core/cover interfaces in the presence of transverse magnetization. A model system consisting of an array of transversely magnetized asymmetric garnet/silicon-on-insulator waveguides is presented.
The Effect of Nb Addition on Phase Equilibria in the Ni-Rich Ni-Al-V Ternary System
Authors: Hayashi Eiki , Kobayashi Satoru , Kaneno Yasuyuki , Takasugi Takayuki 
Published: April 2011

ABSTRACTThe effect of Nb addition on phase equilibria among Ni (A1), Ni3Al (L12) and Ni3V (D022) phases was investigated in the Ni-rich Ni-Al-V ternary system. The addition of Nb to the Ni-Al-V ternary system shifts the three-phase coexisting region of A1 + L12 + D022 towards the Ni-rich side at 950 ºC. Nb is partitioned into the D022 phase more strongly than the A1 and L12 phases. These results suggest that the addition of Nb stabilizes the D022 phase against the A1 and L12 phases in the systems. The alloying element raises the temperature of a eutectoid-like reaction (A1→L12+D022) by ~30 ºC in the vertical section of Ni-Al-V ternary system at 75 at. % Ni.
A step by step strategy for solution-processed quantum dots
light emitting diodes
Authors: Bourvon Hélène , Le Calvez Stéphanie , Vaufrey David , Della Gatta Sylvia Meunier 
Published: April 2011

ABSTRACTSolution-based printing and coating processes have the potential to
dramatically reduce the production costs of Organic Light Emitting Diodes.
This is particularly true for Quantum Dots Light Emitting Diode (QDLEDs),
the newborn in the field of LEDs, due to quantum dots price prohibiting
wastage. Here, we report our latest results on the development of
solutionprocessed QDLEDs. We have implemented a layer by layer strategy,
from a whole evaporated small molecule based OLED to a hybrid QDLED
developed by wet deposition techniques for the first layers and by
evaporation for the last ones. Intermediate steps are discussed in this
paper.First, we have worked on a poly(3,4-ethylenedioxythiophene
poly(styrenesulfonate) (PEDOT:PSS) layer. The PEDOT:PSS formulation for
inkjet printing and spin coating were optimised: wettability on an ITO
substrate, jettability of the inkjet formulation and baking conditions were
studied. Additives as surfactant and ethylene glycol were added to the
commercial inkjet grade solution to improve the deposition process. As a
consequence to this study, anisotropic conductivity of PEDOT:PSS was
observed and is reported here. In particular, ethylene glycol demonstrated a
strong ability to increase the parallel conductivity by several orders of
magnitude, but not the vertical one.Then, inkjet-printed and spin-coated device performances are compared to
complete this first study. Hybrid devices with an efficacy of 12cd/A at 4V
were obtained, with 2.17 % of EQE, and a luminance of 4000 cd/m2
at 4V.Finally, we succeeded in the development of our first QDLED based on CdSe
core/ CdSZnS shell quantum dots emitting at a wavelength of 600nm. Quantum
dots were inkjet printed, in order to waste as little as possible this very
expensive material.
Magneto-photonic ring circulator in Bismuth Iron Garnet thin film: design and fabrication
Authors: Magdenko L. , Popova E. , Smigaj W. , Beauvillain P. , Keller N. , Gralak B. , Gogol P. , Megy R. , Vanwolleghem M. , Dagens B. 
Published: April 2011

ABSTRACTMagneto-optical garnet based optical circulator was designed and fabricated with wafer-scale technology. Modeling and simulation strategy is established for the optimization of a new design of circulator based on ring cavity. Wafer-scale technological process is developed and demonstrated allowing fabrication of the optimized BIG/GGG buried ring circulator.
Modeling W-V and W-Ta Alloys for Fusion Applications: Phase Stability, Short-Range Order and Point Defect Properties
Authors: Muzyk M. , Nguyen-Manh D. , Kurzydlowski K.J. , Baluc N.L. , Dudarev S.L. 
Published: April 2011

ABSTRACTWe have performed density-functional theory (DFT) calculations of phase stability, formation energies of radiation defects in tungsten-based binaries W-Ta and W-V. These alloys are candidate for DEMO divertor applications because of their high melting point and expected improved ductility and fracture toughness in comparison with tungsten. We have identified the lowest energy intermetallic compounds, which should form at low temperatures, and calculated the effective inter-atomic interactions. Using Monte-Carlo calculations, we calculated the temperature of order-disorder phase transformations for these alloys. The predicted temperature of order-disorder phase transformations is relatively low and at high temperature it is found that the short-range order is present for both alloys. Ab-initio calculations also show that vanadium atoms strongly trap self-interstitial atom defects in W-V alloys, whereas Ta atoms in W-Ta alloys have very little effect on either the formation energy or thermally activated mobility of self-interstitial atom defects.
The observation of surface-softening in Fe-based metallic glass
Authors: Masood Ansar , Ström V. , Belova L. , Oak J.J. , Ågren J. , Rao K. V. 
Published: April 2011

ABSTRACTDepth sensing nano-indentation investigations have been performed to determine the radial dependence of the hardness through the cross section of a Fe-based bulk glassy rod. We have found the hardness of the material decreases along radius from the centre to the outermost surface. This phenomenon is attributed to the ‘cooling rate induced surface softening’. Furthermore, a significant change (~15 %) in elastic modulus is noticed along the radius as well.
Atomistic to Continuum Constitutive Modeling of Radiation Damage on FCC Metals and its Adaptation for the Generation of New Materials
Authors: Krishna Shree , De Suvranu 
Published: April 2011

ABSTRACTThe paper presents a rate-independent dislocation growth and defect annihilation mechanism to capture the pre- and post-yield material behavior of FCC metals subjected to different doses of neutron radiation. Based on observation from molecular dynamics simulation and TEM experiments, the developed model is capable of capturing the salient features of irradiation induced hardening including increase in yield stress followed by yield drop and non-zero stress offset from the unirradiated stress-strain curve. The key contribution is a model for the critical resolved slip resistance that depends on both dislocation and defect densities which are governed by evolution equations based on physical observations. The result is an orientation-dependent nonhomogeneous deformation model which accounts for defect annihilation on active slip planes. Results for both single and polycrystalline simulations of OFHC copper are presented and are observed to be in reasonably good agreement with experimental data. Extension of the model to other FCC metals is straightforward and is currently being developed for BCC metals giving its way for generation of new materials.
Corrosion behavior of martensitic/ferritic oxide dispersed strengthened steels in nitric media
Authors: Gwinner Benoit , Auroy Martin , Mas Dominique , Saint-Jevin Audrey 
Published: April 2011

ABSTRACTThe corrosion behavior of three martensitic/ferritic oxide dispersed strengthened (ODS) steels with different chromium contents (respectively 9, 14 and 18wt %) has been studied in hot and concentrated nitric acid. Immersion and electrochemical tests have been carried out in different experimental conditions (temperature and nitric acid concentration). In each case, the corrosion kinetics has been characterized by mass loss measurement of samples (immersion tests) and the electrochemical behavior by linear sweep voltammetry techniques. The dependency of the corrosion rate with the chromium content in the steel, the nitric acid concentration and the temperature, has been quantitatively established and qualitatively discussed.
Coming Full Circle: The Application of Microtechnology Techniques to Evaluate Bulk Materials
Authors: Read David , Barbosa Nicholas 
Published: April 2011

ABSTRACTA tensile test procedure that accommodates specimens with gage section 25 μm thick, 70 μm wide and 360 μm long was developed and demonstrated. The instrumentation and technique were adapted from those previously developed and used to test thin films, by increasing both the force capacity of the load cell and the stiffness of the pull rod. Specimens with bow-tie geometry were fabricated by photolithography from nominally 25 μm thick full hard stainless steel 302 foil. A silicon test frame fabricated by bulk micromachining techniques included tapered grips in the form of recesses in its top surface that accepted and retained the specimen grip sections. One grip was on the fixed outer portion of the frame. The other grip was on a plate suspended in the center of the frame by long slender silicon beams. Force was imposed on this plate by pin loading. The force was measured by use of a custom load cell. The displacement was measured by sub-pixel digital image correlation to surface features on the two ends of the gage section, applied to images with a resolution of approximately 0.8 μm per pixel. Yield and ultimate strengths and elongation values consistent with vendor-provided information were obtained. The values of Young’s modulus were scattered but within the range of expected behavior for the specimen material.