bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hardness Indentation Studies On Metallic Glasses
Authors: Wesseling Paul , Lowhaphandu Peravudh , Lewandowski John. J. 
Published: April 2011

ABSTRACTVickers micro-hardness indentations have been performed on a number of amorphous metals. The effects of changes in indentation load on the hardness and appearance of indents will be discussed for amorphous Al87Ni7Gd6. In addition, the effects of changes in test temperature on the micro-hardness and appearance of indentations in Vitreloy I are presented. A transition in deformation/flow character was detected with increasing test temperature for the Vitreloy I specimens. In addition, preliminary hardness data obtained at room temperature on an iron based metallic glass exhibited values in excess of 12 GPa without cracking.
Progress in Consolidation of Amorphous Zr-based Powder into Bulk Metallic Glass
Authors: Mathaudhu Suveen N. , Im Jae Taek , Barber Robert E. , Anderson Iver E. , Karaman Ibrahim , Ted K. 
Published: April 2011

ABSTRACTEqual channel angular extrusion (ECAE) is used to consolidate amorphous Vitreloy 106a (Zr58.5Nb2.8Cu15.6Ni12.8Al10.3) powder into bulk metallic glass. Consolidations are performed on gas atomized powder containing 1280 ppmw oxygen encapsulated in copper cans and 780 ppmw oxygen powder encapsulated in nickel cans in a 90° die-angle tool at temperatures above the glass transition temperature (Tg) but below the rapid crystallization temperature (Tx), in the supercooled liquid region (ΔT). Results show that V106a is successfully consolidated to nominal full density after one extrusion pass. Good particle-to-particle bonding and significant particle deformation are observed in the consolidated alloy. A lower oxygen content is beneficial due to the larger undercooled region and the additional time for processing. The low oxygen content material shows little change in thermal stability after being consolidated when compared to the original powder but fine interparticle cracks are observed in some of the consolidates. ECAE appears to be a viable method for consolidating amorphous metal powders into bulk amorphous metal.
Comparison between thermal and deformation-induced structural relaxation in atomic glasses
Authors: Nandagopal Magesh , Utz Marcel 
Published: April 2011

ABSTRACTPlastic yielding in glassy solids has been interpreted as a strain-biased relaxation process, or, equivalently, as a strain-induced glass transition. In the present work, the atomic motions caused by athermal plastic deformation of a binary Lennard-Jones glass are compared to thermal motion in the liquid in terms of the self part of the intermediate structure factor. We find that like at finite temperature, athermal plastic deformation leads to diffusive atomic motion at all length scales beyond about one interatomic distance, effectively promoting structural relaxation. The present approach allows to study the interplay of deformation-induced and thermal relaxation. Preliminary evidence is presented that these two processes occur independently of each other over a wide range of strain rates.
Risks and Uncertainties Associated With High-Level Waste Tank Closure
Authors: Esh David W. , Bradford Anna H. , Banovac Kristina L. , Jennifer Davis B. 
Published: April 2011

ABSTRACTClosure of tanks containing high-level radioactive waste (HLW) is a challenging problem involving potentially competing influences from economic, societal, and technological considerations. The U.S. Department of Energy (DOE) is faced with protecting public health and the environment while making economically responsible decisions. Risk (i.e., annual dose) is becoming more prominent as DOE's metric to evaluate the economic consequences of its decisions. Risks are assessed through modeling and calculations commonly known as performance assessment (PA). In the process of tank closure, the U.S. Nuclear Regulatory Commission (NRC) is typically consulted to perform an independent review of DOE's PAs.The NRC staff developed a generic PA model, applicable to HLW tank closure, which NRC utilizes to complete its independent review. The model was developed using the generic simulation software, GoldSim, because of its probabilistic capabilities and its adaptability to different problems [1]. The NRC staff uses the resultant risk from the generic models to evaluate the reasonableness of performance assessment models submitted by DOE. Large differences in the estimates of risk between the generic PA model and the DOE PA would likely indicate a need for stronger technical basis for processes significantly contributing to annual dose (risk) reduction.
Leaching of americium-241, plutonium-238 and matrix elements from perovskite-based ceramics
Authors: Ochkin A. V. , Chizhevskaya S. V. , Archakova N. E. , Merkushkin A. O. , Petukhova I. A. , Mikhailenko N. P. , Stefanovsky S. V. 
Published: April 2011

ABSTRACTPerovskite-based ceramics ABO3 (A = La or Gd; B = Al or Fe) and a pseudobinary system: LaAlO3 + CaZrTi2O7 are promising matrices for immobilization of actinide fraction of HLW. The ceramic samples containing 241Am, 238Pu or 147Pm were prepared by cold pressing in pellets at 100–300 MPa and sintering at 1300–1500 °C. Leach rates of radionuclides and matrix elements (La, Gd, Al and Fe) from powders were measured using Soxhlet unit. Sintered ceramics in the series: LaAl1-xFexO3 were composed of perovskite phase. Ceramics in the compositional series xLaAlO3 + CaZrTi2O7 (0.4 ≤ x ≤ 6) consisted of perovskite, zirconolite, and baddeleyite at x = 0.4 and x = 0.7, and perovskite and baddeleyite at higher x values. Leach rate of radionuclides and matrix elements from all the ceramics were lower than 10-8 g·cm-2·day.
Selection of Matrices for Immobilization of Actinide Fraction of HLW
Authors: Ochkin A. V. , Stefanovsky S. V. , Rovny S. I. 
Published: April 2011

ABSTRACTHLW after the separation of U, Pu and Np contains two major radionuclide groups: fission products and TRU elements. The later ones are the most dangerous and should be separated in the special actinide fraction. This process has been realized at PA “Mayak”.The composition of the actinide fraction depends on a separation method:A. Radionuclides of Am and Cm with minor amounts of U, Np and Pu.B. Radionuclides of Am and Cm with minor amounts of U, Np and Pu and also REEs.C. Radionuclides of Am and Cm with minor amounts of U, Np and Pu and also REEs and perhaps some amount of Zr.The fraction with composition A can be burned off in fast reactors whereas the fractions with compositions B and C should be immobilized in stable matrices. Alpha-Activity of actinide fraction is subsequently determined by 244Cm, 241Am, 244Am, 239Pu and 242Pu during a long-term storage. The storage time depends on conditions and can reach several hundreds of thousands years. The main requirements to matrices are chemical and radiation resistances. The fraction with composition B can be incorporated in perovskite ceramics whereas in case of composition C the additional zirconolite and/or pyrochlore phases are necessary.
Real and Reciprocal Space Imaging of Radiation-Induced Defects in BCC Fe
Authors: Stoller R. E. , Ice G. E. , Barabash R. I. 
Published: April 2011

ABSTRACTIt is important to determine the number and configuration of point defects that survive atomic displacement cascades in irradiated materials since only those defects that escape recombination are able to contribute to radiation induced property changes such as void swelling, hardening, embrittlement, and irradiation creep. Simulations of displacement cascades using molecular dynamics are being used to provide a description of the most probable surviving defects. In the case of interstitial-type defects in iron, these are predicted to be <110> and <111> type dumbbells and <111> crowdions, along with small clusters of these same defects. Diffuse x-ray and neutron scattering provides a direct method for obtaining detailed information on the displacement fields both near to and far away from the defects in addition to information on the particular position of the defect. To analyze such radiation damage with diffuse scattering we have modeled reciprocal space diffraction from crystals with variously oriented dumbbells and small clusters. Diffuse scattering measurements between and close to Bragg reflections are sensitive to the orientation of the dumbbells, and the size and type of the small clusters at sizes that are too small to analyze by electron microscopy. Displacement of the near neighbors induces diffuse scattering in regions between the Bragg peaks, whereas the long range part of the displacement field results in Huang scattering close to the Bragg reflections. Simulation of diffuse scattering by different interstitial defects around (h00), (hh0), (hhh), (3h,h, 0) reflections demonstrates that each defect type leads to distinct isointensity contours. These scattering signatures can be used to determine the type and configuration of the surviving interstitials.
Corrosion and Stress Corrosion Cracking of Alloy 22 in Lead-Containing Solutions
Authors: Pan Yi-Ming , Dunn Darrell S. , Yang Leitai , Cragnolino Gustavo A. 
Published: April 2011

ABSTRACTThe susceptibility of Alloy 22 to localized corrosion and stress corrosion cracking was evaluated in lead-containing solutions. Speciation calculations indicate that aqueous dissolution of PbCl2 resulted in the formation of Pb2+ and Pb-Cl complexes. PbCl2 was selected among several lead compounds for its high solubility and dissociation rate. The total dissolved lead species concentration was measured by inductively coupled plasma-atomic emission spectrometry. Comparative anodic polarization tests were conducted in a range of deaerated, acidified PbCl2 solutions. The presence of lead species in a super-saturated PbCl2 solution with apH of 0.5 promotes the occurrence of apronounced anodic peak and significantly increases the passive current density. Enhanced dissolution of Alloy 22 resulted, as characterized by the presence of randomly distributed etch pits. At an applied potential of -100 mVSCE, which is the potential corresponding to the anodic peak, Alloy 22 was found to be resistant to stress corrosion cracking when tested in super-saturated PbCl2 solutions (pH 0.5) at 95 °C [203 °F]. Moreover, no deleterious effect of lead species on localized corrosion was observed in crevice specimens over a wide range of lead concentrations with the exception of acidified, super-saturated PbCl2 solutions. Provided that these high lead concentrations are not attainable in the anticipated repository environments, Alloy 22 is unlikely to be susceptible to stress corrosion cracking or localized corrosion.
Characteristics of the Oxides Films formed on Alloy C-22
Authors: Szmodis Alan W. , Anderson Kelly L. , Farmer Joseph C. , Lian Tiangan , Orme Christine A. 
Published: April 2011

ABSTRACTThe passive corrosion rate of Alloy C-22 is exceptionally low in a wide range of aqueous solutions, temperatures and electrochemical potentials. Alloy C-22 contains approximately 22% chromium (Cr) by weight; thus, it forms a Cr-rich passive film in most environments. A study of the composition, thickness and other properties of the passive film was undertaken to better understand the role of the protective oxide in preventing corrosion. In general the oxide film is expected to be a function of solution pH, temperature and applied electrochemical potential. In this work we focus on the oxide films that form at pH=8.
U- and Hf-Bearing Pyrochlore and Zirconolite and their Leached Layers Formed in Acidic Solution: Tem Investigation
Authors: Xu Huifang , Wang Yifeng , Zhao Pihong , Bourcier William L. , Van Konynenburg Richard , Shaw Henry F. 
Published: April 2011

ABSTRACTTransmission electron microscopy results from a sintered ceramics with stoichiometry of Ca(U0.5Ce0.25Hf0.25)Ti2O7 show the material contains both pyrochlore and zirconolite phases and structural intergrowth of zirconolite lamellae within pyrochlore. (001) plane of zirconolite is parallel to (111) plane of pyrochlore because of their structural similarities. The pyrochlore is relatively rich in U, Ce, and Ca with respect to the coexisting zirconolite. Average compositions for the coexisting pyrochlore and zirconolite at 1350 °C are Ca1.01(Ce3+0.13Ce4+0.19U0.52Hf0.18)(Ti1.95Hf0.05)O7 (with U/(U+Hf) = 0.72) and (Ca0.91Ce0.09)(Ce3+0.08U0.26Hf0.66Ti0.01)Ti2.00O7 (with U/(U+Hf) = 0.28) respectively. A single pyrochlore (Ca(U,Hf)Ti2O7) phase may be synthesized at 1350 °C if the ratio of U/(U+Hf) is greater than 0.72, and a single zirconolite (Ca(Hf,U)Ti2O7) phase may be synthesized at 1350 °C if the ratio of U/(U+Hf) is less than 0.28. An amorphous leached layer that is rich in Ti and Hf forms on the surface after the ceramics has been leached in pH 4 buffered solution. The thickness of the layer ranges from 5 nm to 15 nm. The leached layer functions as a protective layer and therefore reduces the leaching rate.
Development of Parallel Dip Pen Nanolithography Probe Arrays for High Throughput Nanolithography
Authors: Bullen David A. , Wang Xuefeng , Zou Jun , Chung Sung-Wook , Liu Chang , Mirkin Chad A. 
Published: April 2011

ABSTRACTDip Pen Nanolithography (DPN) is a lithographic technique that allows direct deposition of chemicals, metals, biological macromolecules, and other molecular “inks” with nanometer dimensions and precision. This paper addresses recent developments in the design and demonstration of high-density multiprobe DPN arrays. High-density arrays increase the process throughput over individual atomic force microscope (AFM) probes and are easier to use than arrays of undiced commercial probes. We have demonstrated passive arrays made of silicon (8 probes, 310 μm tip-to-tip spacing) and silicon nitride (32 probes, 100 μm tip-to-tip spacing). We have also demonstrated silicon nitride “active” arrays (10 probes, 100 μm tip-to-tip spacing) that have embedded thermal actuators for individual probe control. An optimization model for these devices, based on a generalized multilayer thermal actuator, is also described.
Characterisation of Collagen Scaffolds using X-ray Microtomography
Authors: Smith Patrick J. , Sachlos Eleftherios , McDonald Samuel , Reis Nuno , Derby Brian , Mummery Paul M. , Czernuszka Jan T. 
Published: April 2011

ABSTRACTCollagen scaffolds have been produced that incorporate predefined internal channels. The scaffolds were obtained with the aid of sacrificial moulds that have been manufactured using a rapid prototyping technique. A computer aided design file of the mould was created and then realised using an ink-jet printer. A dispersion of collagen was then cast into the mould and frozen. Ethanol was used to dissolve the mould leaving the collagen, which was then freeze dried to produce the final product. The scaffold was then analysed using X-ray microtomography (XMT) to determine whether the desired internal structure was obtained. It was found necessary to add saturated potassium iodide (KI) solution to the scaffold in order to analyse it satisfactorily by XMT. The resultant images indicate that the desired internal structure was obtained.
Poly-SiGe, a superb material for MEMS
Authors: Witvrouw Ann , Gromova Maria , Mehta Anshu , Sedky Sherif , Moor Piet De , Baert Kris , Hoof Chris van 
Published: April 2011

ABSTRACTIn this overview article several MEMS applications of poly-SiGe are discussed: thermal applications, the application as a capping layer for MEMS wafer-level packaging and the use as MEMS structural layer for processing MEMS devices on top of CMOS. For all these applications also different deposition processes have been developed: chemical vapor deposition at reduced pressure (RPCVD), at low pressure (LPCVD) and with plasma enhancement (PECVD). Special techniques to reduce the processing temperature to the absolute minimum are reviewed as well: the use of hydrogenated microcrystalline SiGe, of metal-induced crystallization and of laser annealing. The latter methods are important when one wants to process SiGe MEMS above advanced CMOS with low-permittivity dielectrics.
Optimization of Mesoporous Silicon Microcavities for Proteomic Sensing
Authors: DeLouise L. A. , Miller B. L. 
Published: April 2011

ABSTRACTTo expand the utility of p+ mesoporous silicon devices in proteomic biosensor applications, we have conducted in-depth studies to quantify the impact of employing a strong base post etch process to modify the microstructure of microcavity sensors tuned to operate in the visible spectrum. Changes in the optical response and quality of the cavity are quantified as a function of potassium hydroxide (KOH) exposure and initial porosity. Our results show that an aqueous ethanol solution containing millimolar concentrations of KOH is an effective means not only to increase the porosity and pore size, thereby enhancing pore infiltration of large (40–50kDa) proteins, but also to fine tune the optical properties of a passive optical devices.
A Novel AFM Chip for Fountain Pen Nanolithography - Design and Microfabrication
Authors: Kim Keun-Ho , Moldovan Nicolaie , Ke Changhong , Espinosa Horacio D. 
Published: April 2011

ABSTRACTA novel atomic force microscopy (AFM) probe has been developed to expand the capability and applications of dip-pen nanolithography (DPN) technology. This new probe has integrated microchannels and reservoirs for continuous ink feed, which allow “fountain-pen” writing called “Fountain Pen Nanolithography” (FPN). Ink is transported from the reservoirs through the microchannels and eventually dispensed onto substrates via a volcano-like dispensing tip. Numerical simulations have been performed to select optimal materials and suitable tip shapes providing a stable fluid-air interface in the tip. Microchannel and dispensing tip have been fabricated by surface micromachining, in particular employing 3 layers of thin films. Fluid flow through the microchannels has been experimentally examined. The probe was used to write on a gold substrate.
Electrical Porous Silicon Microarray for dna Hybridization Detection
Authors: Archer Marie , Christophersen Marc , Fauchet Philippe M. , Persaud Deoram , Hirschman Karl D. 
Published: April 2011

ABSTRACTThe sensitivity of Porous Silicon (PSi) to the presence of charged molecules and its large internal surface area represent two important properties that make this material and ideal candidate for electrical biosensor development. We have demonstrated the use of a macroporous silicon electrical sensor for label-free detection of DNA hybridization in real time as well as identification of organic solvents in liquid phase. Binding of DNA inside the PSi matrix induces a change in capacitance and conductance. Having demonstrated the suitability of macroporous silicon layers for real time detection of DNA hybridization on single devices, we have extended our findings to the fabrication of a microarray with individual device electrical addressing capabilities. On a crystalline p-type silicon wafer, process steps such as KOH etching and electrochemical dissolution are employed in selected regions to create a free-standing porous membrane for sensing applications. Individual electrical contacts are made on the front side of the wafer while the infiltration of the probe and target molecules is done from the back avoiding any direct interaction of the molecules with the contact sites. We will report on the design considerations of the electrical porous silicon array and the preliminary results obtained using synthetic DNA as a model molecule.
Ferroelectric Lead Zirconate Titanate and Barium Titanate Nanoshell Tubes
Authors: Luo Yun , Szafraniak Izabela , Nagarajan Valanoor , Wehrspohn Ralf B. , Steinhart Martin , Wendorff Joachim H. , Zakharov Nicolai D. , Ramesh Ramamoorthy , Alexe Marin 
Published: April 2011

ABSTRACTWetting of the pore walls of porous templates is a simple and convenient method to prepare nanoshell tubes. Wafer-scale fabrication of ferroelectric lead zirconate titanate and barium titanate nanoshell tubes was accomplished by wetting porous silicon templates with polymeric precursors. The ferro- and piezoelectric properties of an individual ferroelectric nanoshell tube either of PZT or of BaTiO3 were electrically characterized by measuring the local piezoelectric hysteresis. A sharp switching at the coercive voltage of about 2 V was shown from the hysteresis loop. The corresponding effective remnant piezoelectric coefficient is about 90 pm/V. We have also prepared highly ordered arrays of free-standing ferroelectric nanoshell tubes obtained by partial etching of the silicon template. Such materials might be used as building blocks of miniaturized devices and could have a significant impact in the field of nano-electromechanical systems.
Nanostructured Oxide Films for High-Speed Humidity Sensors
Authors: Steele John J. , Harris Kenneth D. , Brett Michael J. 
Published: April 2011

ABSTRACTMiniaturized thin film humidity sensors were fabricated using nanostructured materials deposited by an advanced technique known as glancing angle deposition (GLAD). These sensors exhibited extremely fast desorption response times of less than 40 ms to steplike changes in humidity. Multiple response time measurements for various initial humidities have shown that the sensors maintain their rapid response at all levels of humidity.
Anomalous Magnetoresistance Behavior of Bismuth Antidot Arrays
Authors: Rabin Oded , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTAntidot arrays were formed in thin films of bismuth by the e-beam evaporation of the metal on the porous surface of porous anodic alumina templates. The magnetoresistance of the antidot array films was measured and compared to that of films deposited on glass slides. A significant difference in magnetoresistance behavior was observed, and this difference was attributed to the enhancement of the two dimensional weak antilocalization effect in the antidot arrays. Scattering rates were obtained by fitting the experimental results to the theoretical expression. The results indicate that the antidot morphology enhances the elastic scattering rate over the inelastic scattering rate.
Percolation in Multi-Wall Carbon Nanotube-Epoxy Composites Influence of processing parameters, nanotube aspect ratio and electric fields on the bulk conductivity
Authors: Sandler Jan K.W. , Windle Alan H. , Martin Christian A. , Schwarz Matthias-Klaus , Bauhofer Wolfgang , Schulte Karl , Shaffer Milo S.P. 
Published: April 2011

ABSTRACTA simple mechanical stirring process leads to charge-stabilised dispersions of aligned, substrate-grown, CVD-grown multi-wall carbon nanotubes in an epoxy resin. Subsequent sample processing, after the addition of the hardener, can be used to induce the nanotube agglomeration necessary to achieve electrically conductive bulk composites at low loading fractions. Both the nanotube percolation threshold and the resulting bulk conductivity can be adjusted by selection of suitable processing parameters and nanotube aspect ratio. This behaviour of aligned CVD-grown multi-wall carbon nanotubes allows lower electrical percolation thresholds than are possible with entangled multi-wall carbon nanotubes, single-wall carbon nanotube bundles, or carbon black in an epoxy matrix. Furthermore, the application of electric fields during composite processing induces the formation of aligned multi-wall carbon nanotube networks between electrodes dipped into the dispersion. Such composites show an electrical conductivity above the anti-static level and retain a degree of optical transmissivity.