bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atom Probe Tomography Characterization of Thin Film Multilayers
Authors: Thompson G. B. , Miller M. K. , Banerjee R. , Fraser H. L. 
Published: April 2011

ABSTRACTAs the individual layer of Ti is reduced in thickness in a Ti/Nb multilayered thin film structure, the Ti layer can undergo a change in phase stability fromhcptobcc. Due to its high spatial resolution, atom probe tomography (APT) is ideally suited to characterize the compositional variations in such thin film structures. A series ofhcpTi /bccNb andbccTi /bccNb multilayers have been sputtered deposited and prepared as APT specimens using a Focus Ion Beam (FIB) milling procedure. The APT results have shown a substantial interdiffusion of Nb into thebccTi layers to a pseudo-equilibrium concentration of approximately Ti-20at%Nb while maintaining a compositionally modulated interface. In contrast, thehcpTi layers indicated little Nb interdiffusion within the layers. Thermodynamic volumetric free energy modeling has indicated that this unexpected Nb interdiffusion facilitated thebccphase stability. The coupling of APT results to the pseudomorphicbccTi phase demonstrates the capability APT has in quantifying the compositional characteristics in these types of multilayered nanocomposite systems.
Structuring of Silicon Wafer Surfaces on the Sub-100 nm Scale by Hydrogen Plasma Treatments
Authors: Job R. , Ma Y. , Ulyashin A. G. 
Published: April 2011

ABSTRACTHydrogen plasma treatments applied on standard Czochralski silicon (Cz Si) wafers cause a structuring of the surface regions on the sub-100 nm scale, i.e. a thin ‘nano-structured’ Si layer is created up to a depth of ∼ 150 nm. The formation of the ‘nano-structures’ and their evolution in dependence on the process conditions was studied. The impact of post-hydrogenation annealing on the morphology of the structural defects was studied up to 1200 °C. The H-plasma treated and annealed samples were analyzed at surface and sub-surface regions by scanning electron microscopy (SEM), atomic force microscopy (AFM), and μ-Raman spectroscopy.
TEM and DOE Optimization Studies of Electrospun Polycarbonate Nanofibers
Authors: Kattamuri Nirupama , Sung Changmo 
Published: April 2011

ABSTRACTElectrospinning of polycarbonate with solvent mixtures of THF (Tetrahydrofuran) and DMF (Dimethylformamide) has been performed. The effect of various process parameters like voltage, concentration, flow rate and distance has been investigated to yield uniform polycarbonate nanofibers with minimal bead densities. The temperature and humidity have also been carefully monitored for all the runs. The Design of Experiment (DOE) has been conducted with the help of Minitab software to find the most significant parameter for obtaining uniform beadless nanofibers. These uniform nanofibers can then be used in future work to produce TiO2 nanotubes.
Preparation of Fe-Pt Nanowires through Anodic Oxidation of Sputtered Aluminum on Glass Surface
Authors: Inoue Satoru , Chu Song-Zhu , Wada Kenji , Kanke Yasushi 
Published: April 2011

ABSTRACTNew process for the preparation of Fe-Pt nanowires has been developed through anodic oxidation and electro deposition technique. Aluminum thin film sputtered on ITO thin film on a glass surface was decomposed into alumina by anodic oxidation technique. The anodic alumina layer possessed nanometer size pore array standing on the glass surface. The barrier layer at the bottom of nanopores was removed by acid etching to attain DC field smooth electro deposition. Fe-Pt components were introduced into nanopores of anodic alumina by electro deposition. The magnetization of Fe-Pt nanowires was investigated. The magnetization perpendicular to the glass surface was very strong and the in-plane magnetization was very small, indicating that the magnetic Fe-Pt nanowires could be potentially applied to ultra high density magnetic recording. The density of the nanowires was estimated to be about 1T bits /inch2.
Flame Retardancy of Laponite- and Montmorillonite-Based Nylon 6 Nanocomposites
Authors: Inan Gunes , Patra Prabir K. , Kim Yong K. , Warner Steven B. 
Published: April 2011

ABSTRACTThe flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.
Topology matters: Some aspects of DNA physics
Authors: Metzler Ralf 
Published: April 2011

ABSTRACTBiological cells, in some sense, are all about topology: Biomembranes separating different volumes from one another, ions or even macromolecules having to cross these membranes in controlled fashion through membrane pores; or certain proteins moving along the DNA to find their target sequence instead of searching for this site in the full 3-dimensional cell volume. Even on the single biopolymer level, topology is an essential ingredient: Intriguingly, in bacteria DNA occurs knotted, i.e., in a state topologically different from a simply connected ring. It is a key question to understand the statistical behaviour of such knotted DNA to understand a number of physiological processes having to overcome this knottedness, or to quantify results from DNA separation techniques such as electrophoresis, in which the knottedness influences the mobility. At the same time, double-stranded DNA continuously opens up floppy single-stranded bubbles, which fluctuate in size, exposing the single Watson-Crick bases to binding proteins. Again, statistical mechanical tools can be employed to examine the bubble dynamics. Here, we introduce some recent results on DNA knots and bubble fluctuations.
Thermal Expansion and Viscosity of Confined Liquids
Authors: Xu Shuangyan , Simmons Gregory C. , Scherer George W. 
Published: April 2011

ABSTRACTThe thermal expansion and viscosity of water and salt solutions in porous silica glasses have been systematically investigated, and the effect of salts on the properties of water in confined geometry has been addressed. A dilatometric method has been devised and utilized to measure the thermal expansion of confined liquids. A beam-bending method that was developed to study the permeability of porous bodies has been used to measure the relative viscosity of salt solutions to water inside the silica pores. This work has demonstrated that water when confined in nanopores shows anomalous behavior and its thermal expansion is higher than bulk water. This work has also suggested that the presence of ions in water could enhance the anomaly of water in confined space and the extent of the ion effect is dependent on the ion charge.
Collective and Molecular Dielectric Relaxation in Confined Liquid Crystals: Effect of Different Layer Thicknesses and Boundary Conditions
Authors: Aliev Fouad M. , Bengoechea Manuel Rivera 
Published: April 2011

ABSTRACTBroadband dielectric spectroscopy was used to study the influence of boundary conditions and layer thickness of liquid crystal (LC) confined to cylindrical pores on low frequency and high frequency relaxation processes. Low frequency measurements provided information on the relaxation of surface polarization that arose at LC – pore wall interface. The dynamics of molecular reorientations were investigated in high frequency experiments. In samples with axial orientation of molecules, the dielectric mode due to reorientation of molecules around their short axis was investigated. The homeotropic alignment of molecules facilitated the investigation of the librational mode. The behavior of this mode was different from the behavior observed in investigations of relaxation due to reorientation of molecules around their short axis. Broadening of the dielectric spectra was observed in confined LC. The broadening increases with decreasing liquid crystal layer thickness.
Mechanical Properties and Filler Distribution as a Function of Filler Content in Silica Filled PDMS Samples
Authors: Hawley M. E. , Wrobleski D. A. , Orler E. B. , Houlton R. , Chitanvis K. E. , Brown G. W. , Hanson D. E. 
Published: April 2011

ABSTRACTAtomic force microscopy (AFM) phase imaging and tensile stress-strain measurements are used to study a series of model compression molded fumed silica filled polydimethysiloxane (PDMS) samples with filler content of zero, 20, 35, and 50 parts per hundred (phr) to determine the relationship between filler content and stress-strain properties. AFM phase imaging was used to determine filler size, degree of aggregation, and distribution within the soft PDMS matrix. A small tensile stage was used to measure mechanical properties. Samples were not pulled to break in order to study Mullins and aging effects. Several identical 35 phr samples were subjected to an initial stress, and then one each was reevaluated over intervals up to 26 weeks to determine the degree to which these samples recovered their initial stress-strain behavior as a function of time. One sample was tested before and after heat treatment to determine if heating accelerated recovery of the stress-strain behavior. The effect of filler surface treatment on mechanical properties was examined for two samples containing 35 phr filler treated or untreated with hexamethyldisilazane (HMDZ), respectively. Fiduciary marks were used on several samples to determine permanent set. 35 phr filler samples were found to give the optimum mechanical properties. A clear Mullins effect was seen. Within experimental error, no change was seen in mechanical behavior as a function of time or heat-treatment. The mechanical properties of the sample containing the HDMZ treated silica were adversely affected. AFM phase images revealed aggregation and nonuniform distribution of the filler for all samples. Finally, a permanent set of about 3 to 6 percent was observed for the 35 phr samples.
Vacancies in electron irradiated 6H silicon carbide studied by positron annihilation spectroscopy
Authors: Lam C. H. , Ling C. C. , Beling C. D. , Fung S. , Weng H. M. , Hang D. S. 
Published: April 2011

ABSTRACTPositron lifetime spectroscopy was employed to study the as-electron-irradiated (10 MeV, 1×1018 cm-2) n-type 6H silicon carbide sample in the measuring temperature range of 15 K to 294 K. Isochronal annealing studies were also performed up to the temperature of 1373 K by carrying out the room temperature positron lifetime measurement. Negatively charged carbon vacancies and VCVSi divacancy were identified as the major vacancy type defects induced by the electron irradiation process. The concentration of the VCVSi divacancy was found to decrease dramatically after the 1973 K annealing.
Irradiated cubic single crystal SiC as a high temperature sensor
Authors: Volinsky Alex A. , Ginzbursky Lev 
Published: April 2011

ABSTRACTRadiation is known to cause point defects formation in different materials. In the case of cubic SiC single crystal radiation flux on the order of 2·1020 neutrons/cm2 at 0.18 MeV causes over 3% volume lattice expansion. Radiation-induced strain (measurable by X-Ray diffraction) can be relieved when the annealing temperature exceeds the temperature of irradiation. Based on this effect the original technology of maximum temperature measurement was developed a while ago. Single crystal SiC sensor small size (200–500 microns), wide temperature range (150–1450 °C), “no-lead” installation, and exceptional accuracy make it very attractive for use in small, rotating and “hard-to-access” parts, including, but not limited to gas turbine blades, space shuttle ceramic tiles, automobile engines, etc. With the advances in X-Ray diffraction measurements, crystal and thin film growth techniques, it is the time to revise and update this technology. Modeling radiation damage, as well as annealing effects are also beneficial.
Properties of Ordered Nanoporous Alumina as a Template for Pattern Transfer by MeV Ion Irradiation
Authors: Razpet Alenka , Possnert Göran , Johansson Anders , Abid Mohamed , Hallén Anders 
Published: April 2011

ABSTRACTOrdered nanoporous alumina has recently been considered as a template for pattern transfer by MeV ion irradiation. Porous alumina of thickness 500 nm has already been used as a mask for low energy heavy ion implantation. However, in order to apply this material as a template for production of structures with higher aspect ratios, lighter ions with MeV energies and larger penetration depth should be used. The aim of this contribution is to examine the transmission of such ions through alumina templates with sufficient thickness to mask ions that are not passing the pores. A careful orientation of the pores in the direction of the incident beam is therefore needed since the acceptance angle for ions passing through the pores decreases with increasing thickness.Typical size of pores in the investigated alumina foils was 70 nm with a repetition frequency of 100 nm. Transmission through the foil and the energy of transmitted MeV ions were measured for aligned alumina foils by standard backscattering technique. It was shown that the sample transmission is a characteristic of each sample, but for some investigated samples the proportion of transmitted ions was the same as the relative area covered by pores. The energy spectra of transmitted ions were used to further evaluate the quality of foil templates for pattern transfer. It was shown that 2 μm thick alumina films can mask 3 MeV O+ ions, which can be used for ion lithography in polymer materials.
Optical and Mechanical Properties of Photoassisted, Self-assembled Nanoparticle Films
Authors: Gaddy G. A. , Miner G. A. , Stoakley Diane M. , Locke Edward P. , Moore Rick L. , Schultz John , Creyts Don , Knotts Michael 
Published: April 2011

ABSTRACTThis paper presents research funded under the Defense Advanced Research Projects Agency (DARPA) MetaMaterials program for design and development of nanoparticle based, mesoscale electromagnetic and optical materials. Specifically, we present results of formulation and near infrared measurement-model validation for photoassisted, self-assembled multilayer metallic nanoparticle films. The multilayer films may be used as optical filters and absorbers. We demonstrate that nanoparticles can be formed in advanced polymer films that exhibit new electromagnetic constitutive properties. Metal nanoparticle films are produced from a single homogeneous resin containing a soluble precursor. Films cast from doped resins are exposed to UV radiation followed by a controlled thermal cure. The combination of UV exposure and thermal curing creates a multiphase material composed of low volume fractions of dispersed metallic Pd clusters (10–20 nm in size) and high concentrations of Pd nanoparticles which form surface and embedded metallic layers in the films. The layer separation is a function of UV exposure. These materials show significant absorption in the optical and near IR region of the spectrum. Furthermore, these films exhibit mechanical properties similar to bi-metallic layers, specifically, the films display reversible bending with exposure to light and an accompanying rapid temperature increase. This paper presents formulation processes, optical-mechanical measurements and measurement model comparison.
Explosive Crystallization in Eutectic Materials of Phase Change Optical Memory
Authors: Okuda Masahiro , Inaba Hirokazu , Usuda Shouji 
Published: April 2011

ABSTRACTThe excess Sb effect for the dynamics of rapid crystallization in eutectic amorphous films are discussed. This crystallization mechanism describe the propagation with high velocity in the interface separating the crystalline and amorphous phase for InSb and AgInSbTe materials. From these analysis, it is clear that the crystallization is grown up in the boundary of crystalline-amorphous region of eutectic materials, which is different from the stoichiometric GeSbTe media. Also, the quantum effect on the melting, crystallization and solidification of phase change media has been discussed.
Structure analysis of amorphous thin films of GeSbTe compounds by grazing incidence X-ray scattering
Authors: Sato Masugu , Matsunaga Toshiyuki , Kouzaki Takashi , Yamada Noboru 
Published: April 2011

ABSTRACTWe have investigated the structures of amorphous thin films of GeSbTe compounds – the materials used for the recording layer of phase-change optical memory – through grazing incidence X-ray scattering (GIXS) measurements. Thin films with compositions of GeSb2Te4 and Ge2Sb2Te5 were deposited on Si substrates. Electron radial distribution functions (RDFs) derived from the data clearly showed evidence of the medium-range order with three peaks of the atomic pair distribution. The RDFs of both samples were very similar to those of amorphous bulk GeTe compounds reported from previous X-ray scattering experiments. The positions of the first peaks of these RDFs were consistent with the distances of the first nearest neighbor pairs reported from previous EXAFS experiments. A comparison of the RDF of the amorphous phase with that of the crystalline phase suggested that the phase change caused no significant change in the number of atoms included inside or the radius of the second nearest neighbor atomic shell, although it changed the coordination number and the distance of the first nearest neighbor atomic pairs. This may shorten the moving distance of atoms in the phase change and enable high-speed phase change.
Chemical Durability Studies of Waste-Simulant Doped Borosilicate Glasses
Authors: Duddridge Adam , Islam Moinul , Holland Diane , Scales Charlie R. 
Published: April 2011

ABSTRACTA mixed-alkali modified borosilicate base glass used in the vitrification of high-level nuclear waste (HLW) has been doped with a number of waste simulants to between 2 and 12 mol%. The simulants have been chosen to give two distinct series of glasses: one consisting of trivalent ions having the form M2O3(where M is La, Bi, Al or Fe) and the other consisting of divalent simulants of the form MO (where M is Pb, Zn or Ba). An international standard Soxhlet leach test procedure was performed on each glass to study the effect of prolonged, moderate-temperature, dynamic water corrosion. Results of these studies show that, except for BaO, as the amount of simulant is increased, the amount of Na and Li leached decreases showing them to become more chemically resistant. These corrosion tests have been correlated to ionic (D.C.) conductivity measurements, which show a decrease in the conductivity of the glass as the amount of waste simulant is increased, and 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR) studies, which have shown that, as more waste-simulant is loaded into the glasses the rate of conversion of [BO4] to [BO3] units increases. All of the data from these studies reflect the different network forming abilities of the divalent and trivalent cations.
Structural Characterisations of Rare Earth-Rich Glasses for Nuclear Waste Immobilisation
Authors: Bardez I. , Caurant D. , Ribot F. , Loiseau P. , Dussossoy J. L. , Villain F. , Baffier N. , Fillet C. 
Published: April 2011

ABSTRACTNew glassy matrices, able to incorporate new highly concentrated radioactive liquid wastes (HLW), are being studied. Investigations were performed on rare earth-rich glasses, known as very durable matrices. The selected basic glass composition was (wt. %): 51.0 SiO2 – 8.5 B2O3–12.2 Na2O – 4.3 Al2O3 – 4.8 CaO – 3.2 ZrO2 – 16.0 Nd2O3. To determine both the environment around the rare earth in this glass and its evolution according to its concentration (1.3 – 30 wt. % Nd2O3), EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy at the LIII-edge of neodymium and optical absorption spectroscopy were used. By coupling these two characterisation methods, several hypotheses are proposed about the nature of the rare earth neighbouring in the glass.
Vapour Phase Hydration of Blended Oxide - Magnox Waste Glasses
Authors: Hyatt Neil C. , Lee William E. , Hand Russell J. , Abraitis Paul K. , Scales Charlie R. 
Published: April 2011

ABSTRACTVapour phase hydration studies of a blended Oxide / Magnox simulant high level waste glass were undertaken at 200°C, over a period of 5 – 25 days. The alteration of this simulant waste glass is characterised by a short incubation time of less than 5 days, leading to the formation of an alteration layer several microns thick. Following the incubation period, the alteration proceeds at a constant rate of 0.15(1)μmd−1. The distribution of key glass matrix (Si, Na) and waste (Cs, Zr, Nd, Mo) elements was found to vary significantly across the alteration layer. Vapour phase hydration leads to formation of surface alteration products, identified as smectite, zirconium silicate and alkaline-earth molybdate phases.
Synthesis of Actinide-Doped Ceramics: from Laboratory Experiments to Industrial Scale Technology
Authors: Kitsay Alexander A. , Garbuzov Vladimir M. , Burakov Boris E. 
Published: April 2011

ABSTRACTThe experience of the Laboratory of Applied Mineralogy and Radiogeochemistry of the V.G.Khlopin Radium Institute on synthesis of Pu-Am-doped ceramics is summarized. During the last 5 years, dozens of actinide doped polycrystalline samples and single crystals have been successfully synthesized such as zircon, hafnon, cubic zirconia, monazite, Ti-pyrochlore, perovskite and garnet. Actinide loading has been varied as follows:-239Pu - from 5–6 wt.% in zircon (polycrystalline and single crystals), hafnon, garnet and perovskite to 10 wt.% in Ti-pyrochlore and up to 37 wt.% in zirconia;- 238Pu - from 2.5 wt.% in zircon single crystals to 5 wt. % in polycrystalline zircon and 10 wt.% in monazite and cubic zirconia;- 243Am - 20–23 wt.% in cubic zirconia and monazite.The weight of each single ceramic pellet varied from 0.2 to 2.0 grams. Special furnaces developed in KRI for ceramic synthesis allowed obtaining up to 7 ceramic pellets simultaneously during the same experiment. The highest amounts of actinides used under glove-box conditions in the same experiment were: 1.5–2.0 g for 239Pu, 0.6 g for 238Pu and 0.3 g for 243Am. Most experiments on synthesis of ceramics and single crystals doped with 239Pu, 238Pu and 243Am carried out at the KRI did not lead to contamination of internal walls of glove boxes. No release of Pu-Am-aerosols was observed as a result of sintering or melting at 1300–1600°C. These results allowed us to conclude that at the present the KRI has developed the experimental basis for transferring laboratory innovations to the industry of actinide immobilization. It is important that adopting ceramic synthesis methods at industrial scale does not require development of new special equipment.