bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluorination of Uranium Metal to UF3 and UF4 by Nitrogen Trifluoride: Evidence for Elusive UF2
Authors: McNamara Bruce K , Scheele Randall , Casella Andrew M , Kozelisky Anne E , Neiner Doinita 
Published: August 2010

AbstractWe have recently found that uranium and plutonium metals will react with nitrogen trifluoride (NF3) at temperatures below 120°C. These are the first reported instances of such low temperature fluorination reactions using NF3 and implicate metal catalyzed dissociation of the NF3 bond. We additionally present preliminary evidences for a surface mediated product distribution. Reaction of uranium metal with NF3 promotes products that are apparently determined by the concentration of the fluorinating reagent between temperatures of 60 to 120°C.
Evolution of the Magnetic and Superconducting States in UCoGe With Fe and Ni Substitution
Authors: Hamlin James Jeffrey , Baumbach Ryan Eagle , Huang Kevin , Janoschek Marc , Kanchanavatee Noravee , Zocco Diego A. , Maple M. Brian 
Published: August 2010

AbstractThe very small number of known ferromagnetic superconductors places the study of such compounds at the frontier of superconductivity research. Recently, UCoGe has emerged as a new member of the class of materials exhibiting coexistence of ferromagnetism and superconductivity (Curie temperature TCurie = 3 K; superconducting critical temperature Ts = 0.8 K). This compound has generated much excitement, in part because it has been proposed that the superconductivity derives from spin triplet pairing mediated by ferromagnetic interactions. Therefore, a key question is how changes in the magnetic state of UCoGe affect the superconducting properties. We have carried out a comprehensive study of the UCo1-xFexGe and UCo1-xNixGe series of compounds across the entire range of composition 0 ≤ x ≤ 1. We report the results of x-ray diffraction, electrical resistivity, and magnetization measurements to elucidate the magnetic and superconducting phase diagram of the U[Fe, Co, Ni]Ge system. Substitution of either Ni or Fe into UCoGe initially results in an increase in the Curie temperature. At higher dopant concentrations (x), the ferromagnetic state crosses over to paramagnetism in UCo1-xFexGe and antiferromagnetism in UCo1-xNixGe.
Stability of Cs-Ionsiv in Portland cement blends for radioactive waste disposal
Authors: Hyatt Neil Christian , Jenni Andreas , Stennett Martin Christopher 
Published: August 2010

AbstractThe suitability of Portland cement blends for encapsulation of Cs-Ionsiv in a monolithic wasteform was investigated. No evidence of reaction or dissolution of the Cs-Ionsiv in the cementitious environment was found by scanning electron microscopy and X-ray diffraction. However, a small fraction (≤1.6 wt%) of the Cs inventory was released from the encapsulated Ionsiv during leaching experiments carried out on hydrated samples. Cs release was enhanced by exchange of K and Na present in the cementitious pore water. Cement systems lower in K and Na, such as slag based blends, showed lower Cs release than the fly ash based analogues.
Migration Behavior of Multivalent Radionuclides From Fully Radioactive Waste Glass in Compacted Sodium Bentonite
Authors: Fujiwara Kenso , Iijima Kazuki , Mitsui Seiichiro , Odakura Makoto , Kohara Yukitoshi , Kikuchi Hiroshi 
Published: August 2010

AbstractIn a repository of high-level radioactive waste, radionuclides will leach from the waste glass and migrate into the surrounding bentonite after very long time. These processes occur simultaneously in the bentonite and should be evaluated to confirm the reliability of individual models and data for the performance assessment of high-level radioactive waste repository.Previous study [1] reported the results of the in-diffusion experiments of Cs in compacted sodium bentonite (Kunigel V1®) in contact with fully radioactive waste glass for 15 to 300 days under aerobic conditions. And Cs migration was successfully interpreted using fundamental one dimensional diffusion model. However, migration of other radionuclides in fully radioactive waste glass were extremely slow because of low solubility, low effective diffusivity and high distribution ratio, especially multivalent elements of actinide and lanthanide.In this study, the similar in-diffusion experiment reported by Ashida et al. [1] was carried out for about 15 years to evaluate the migration behavior of multivalent actinide and lanthanide elements. The bentonite was compacted into a stainless steel cell with 20 mm in diameter and 18 mm in length to produce dry densities of 0.5 and 1.0 Mg m-3saturated distilled water. The form of fully radioactive waste glass was borosilicate glass by using vitrified in CPF (Chemical Processing Facility). The glass sample was sliced into the disc with 4 mm in thickness and sandwiched by two pieces of the saturated bentonite sample in the diffusion cell under aerobic conditions. After 15 years, bentonite sample was sliced and immersed into the HNO3 to extract the radionuclides from the bentonite. Then profiles of Cs, Eu, Pu, Am and Cm in the bentonite sample were evaluated. The concentration profile of Cs in the bentonite was constant due to its high diffusivity.The experimental concentrations of Am, Cm and Eu in contact with compacted sodium bentonite were good agreement with the solubilities calculated by thermodynamic data. On the other hand, the profiles of Am and Cm show two parts with different slopes which cannot be fitted by simple one-dimensional diffusion model considering single specie. Leaching and migration behavior of radio nuclides will be discussed based on the one-dimensional diffusion model considering other mechanism of several species.[1] T. Ashida, et al. Migration behavior of cesium released from fully radioactive waste glass in compacted sodium bentonite. PNC Technical Report, TN8410 98-014(1998).
Microstructural modifications in ion-irradiated nuclear materials: characteristic features of fluorite-structured oxides
Authors: Debelle Aurelien , Garrido Frederico , Thome Lionel 
Published: August 2010

AbstractThe behavior of two nuclear materials, namely cubic zirconia and urania, is investigated under different irradiation conditions in the low and medium ion energy range (tens of keV to a few MeV). In each case, these materials display a multi-step damage build-up, as revealed by both RBS/C and XRD measurements. It is demonstrated that each step exhibits characteristic features such as damage fraction, elastic strain, nature of defects, and thus presents a specific microstructure. The transition from one step to the following involves radiation defect re-organization which arises to lower the energy of the system.
Selective Radioactive Decontamination employing Dual Stimuli Responsive N-Aza crown ether containing polymer hydrogels
Authors: Deli Dario , Crouch David J , Law Kathleen , Yeates Stephen G , Livens Francis 
Published: August 2010

AbstractWe report the synthesis and properties of two different hydrogels based on N-isopropylacrylamide/acrylic acid and copolymers of oligo-ethylene glycol methacrylates incorporating N-Aza crown ethers. Both hydrogels show rapid response to environmental stimuli and their size can be tuned by pH and temperature. Swollen states lead to high adsorption of water and high contact surface area with ions whereas in the collapsed state the material releases water and the ions not selectively retained by the polymer.Preliminary autoradiography tests show that these materials strongly bind 90Sr and both pH and temperature can be used to fine tune binding selectivity. This results in such materials being promising candidates for use as smart scavenging agents for radioactive decontamination.
Thermoelectric Properties of CoSb3-based Skutterudite Compounds
Authors: Harnwunggmoung Adul , Kurosaki Ken , Muta Hiroaki , Yamanaka Shinsuke 
Published: August 2010

AbstractCoSb3 is known as a skutterudite compound that could exhibit high thermoelectric figure of merit. However, the thermal conductivity of CoSb3 is relatively high. In order to enhance the thermoelectric performance of this compound, we tried to reduce the thermal conductivity of CoSb3 by substitution of Rh for Co and by Tl-filling into the voids. The polycrystalline samples of (Co,Rh)Sb3 and Tl-filled CoSb3 were prepared and the thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured in the temperature range from room temperature to 750 K. The Rh substitution for Co reduced the lattice thermal conductivity, due to the alloy scattering effect. The minimum value of the lattice thermal conductivity was 4 Wm-1K-1 at 750 K obtained for (Co0.7Rh0.3)Sb3. Also the lattice thermal conductivity rapidly decreased with increasing the Tl-filling ratio. T10.25Co4Sb12 exhibited the best ZT values; the maximum ZT was 0.9 obtained at 600 K.
Effect of (Pb,Ge)Te Addition on the Phase Stability and the Thermoelectric Properties of AgSbTe2
Authors: Aikebaier Yusufu , Kurosaki Ken , Muta Hiroaki , Yamanaka Shinsuke 
Published: August 2010

AbstractAlthough AgSbTe2 exhibits excellent thermoelectric properties, the single phase is unstable and second phases such as Ag2Te and Sb2Te3 are easy to precipitate. In the present study, we tried to stabilize the AgSbTe2 phase by adding a small amount of another phase. Here we chose Pb0.16Ge0.84Te as the adding phase because the crystal structure and the lattice parameter were completely the same as those of AgSbTe2. The samples of (Ag0.5Sb0.5Te1-x(Pb0.16Ge0.84Te)x (x = 0, 0.01, 0.02, 0.05, and 0.1) were prepared and the phase stability and the thermoelectric properties were examined. The AgSbTe2 phase was stabilized in the samples of x = 0.01 and 0.02. All the samples exhibited large thermoelectric figure of merit.
Thermoelectric Properties of SiO2/SiO2+CoSb3Multi Nanolayered Films Modified by Me v Si ions Bombardment
Authors: Budak S. , Smith Cydale , Chacha John , Pugh Marcus , Ogbara Kudus , Heidary Kaveh , Johnson R. B. , Muntele Claudiu , ILA D. 
Published: August 2010

AbstractThe performance of the thermoelectric devices and materials is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ or decreasing K. We have prepared 100 alternating nanolayered films of SiO2/SiO2+CoSb3 using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed using the AAMU Pelletron ion beam accelerator to make quantum clusters in the nanolayered superlattice films at the three different fluences to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. We have characterized 100 alternating nanolayered films of SiO2/SiO2+CoSb3 before and after Si ion bombardments as we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for three different fluences.
Improvement in Contact Resistivity to thin film Bi2Te3
Authors: Gupta Rahul P , Xiong Ka , White John B , Cho Kyeongjae , Gnade Bruce 
Published: August 2010

AbstractA study of the impact of surface preparation and post-deposition annealing on contact resistivity for sputtered Ni and Co contacts to thin film Bi2Te3 is presented. The contact resistance values obtained using the transfer length method (TLM) for Ni is compared to Co as a potential contact metal to Bi2Te3. Post-deposition annealing at 100°C on samples that were sputter cleaned reduces the contact resistivity to < 10-7 Ω-cm2 for both Ni and Co contacts to Bi2Te3. Co provided similar contact resistance values as Ni, but had better adhesion and less diffusion into the thermoelectric (TE) material, making it a suitable candidate for contact metallization to Bi2Te3 based devices.
Thermoelectric Properties of Electrodeposited BiSbTe Nanowires
Authors: Mannam Raja Sekharam , Davis Despina 
Published: August 2010

AbstractBismuth antimony telluride (BiSbTe) nanowires were electrodeposited at constant potentials into polycarbonate templates from a tartaric-nitric acid baths having different electrolyte compositions. Composition analysis of the nanowires showed that Sb deposits at higher potentials compared to BiTe. Maximum seebeck coefficients of -337.7 μV/K and 227.2 μV/K were obtained for n-type and p-type nanowires samples Bi4.6Te5.4 and Bi4.3Sb5 respectively. Nonmonotonic resistance behavior was observed for all the nanowires.
Colloidal nanostructures as building blocks for macroscopic thermoelectric materials with electron-crystal phonon-glass properties
Authors: Scheele Marcus , Oeschler Niels , Meier Katrin , Kornowski Andreas , Klinke Christian , Weller Horst 
Published: August 2010

AbstractWe demonstrate the shape- and size-controlled synthesis of colloidal ∼10 nm bismuth telluride nanoparticles stabilized by organic ligands in solution. Post-synthetic ligand exchange with oleic acid allows for a quick and simple ligand removal by consecutive washing with basic ammonia solution. Mild spark plasma sintering yields a macroscopic nanostructured bulk solid with nanograins unaltered in size and shape. We present the full thermoelectric characterization with an emphasis on the thermal properties of this material. It will be shown that thus prepared nanostructured bulk solids possess significantly altered physical properties typical for materials with high surface-to-volume-ratios. These alterations have the potential to lead to improved thermoelectric performances benefiting from their phonon-glass electron-crystal behavior.
Single-crystal Wires Based on Doped Bi for Anisotropic Thermoelectric Microgenerators
Authors: Nikolaeva Albina Alexandr , Konopko Leonid A , Huber Tito E , Tsurkan Ana K 
Published: August 2010

AbstractIn this work, we have studied the possibility to use a microwire of BiSn to design an anisotropic thermoelectric generator. The glass-coated microwire of pure and Sn-doped bismuth was obtained by the Ulitovsky method; it was a cylindrical single-crystal with orientation (1011) along the wire axis; the C3 axis was deflected at an angle of 70° to the microwire axis. It is found that doping of bismuth wires with tin increases the thermopower anisotropy in comparison with Bi by a factor of 2 – 3 in the temperature range of 200 – 300 K. According to the preliminary results, for a Bi microwire with a diameter of 10 μm with a glass coating of 35 μm, the transverse thermopower is ∼ 150 μV/(K*cm); for BiSn, 300 μV/(K*cm).The design of an anisotropic thermogenerator based on BiSn microwire is proposed. The miniature thermogenerator will be efficient for power supply of devices with low useful current.In addition to the considerable thermopower anisotropy of BiSn wires in a glass coating, they exhibit stable thermoelectric properties, high mechanical strength and flexibility, which allows designing thermoelectric devices of various configurations on their basis.
Microthermocouples of a Glass-Insulated Bifilar Microwire Based on Bi2Te3
Authors: Meglei Dragosh F , Huber Tito E , Dyntu Maria P , Nikolaeva Albina Alexandr 
Published: August 2010

AbstractThe paper presents the results of studies related to the technology for obtaining glass-insulated bifilar microwires (BMWs) of a thermoelectric material based on Bi2Te3 with one wire exhibiting the n-type and the other p-type conduction as well as the study of their mechanical properties by the strain method and the microscopic analysis of the morphology of structural defects with a view to preparing microthermocouples on their basis.Preliminary studies showed that BMWs are more flexible than single microwires of the same material. The rupture strength of BMWs per unit cross section of a sample (together with the glass) ranges within 18-6 kg/mm2 with respect to diameters of 90-120 μm.Microthermocouples with a signal value on the order of 2-12 mV in a temperature range of 23-50°C have been developed. The preparation of thermoelectric microthermocouples of BMWs significantly reduces the number of process operations in the course of their production and considerably increases their resistance to impacts and vibrations. Microthermocouples based on glass-insulated BMWs have smaller sizes and weight; they can be used for measuring temperatures in chemically aggressive media.
Preparation of High Seebeck Coefficient Calcium Cobaltate Thermoelectric Powders
Authors: Lin Sidney , Selig Jiri 
Published: August 2010

AbstractThermoelectric calcium cobalt oxide (Ca1.24Co1.62O3.86) with high Seebeck coefficient was prepared by self-propagating high temperature synthesis (SHS) followed by a short post treatment process. Synthesized samples were analyzed by XRD for their phase purity for samples prepared from different reactants mixtures. A final element model of SHS of calcium cobalt oxide was developed to study the temperature history and reaction rate change during the synthesis. This model can be used to predict reaction temperatures for various initial conditions.
Light Beam Induced Current Mapping of mc-Si Solar Cells: Influence of Grain Boundaries and Intragrain Defects
Authors: Jimenez Juan , Moralejo Benito , Hortelano Vanesa , González Miguel Ángel , Martínez Oscar , Parra Vicente , Avella Manuel 
Published: August 2010

AbstractThe photovoltaic market is currently dominated by multicrystalline silicon. However, this material is characterized by intrinsic structural heterogeneity due to point defects, dislocations and grain boundaries. In order to improve the cell performance the control of the electrical properties of the grain boundaries and dislocations is required. The laser beam induced current technique allows the estimation of the variations of the charge capture rates due to the different trapping centers, and is a powerful tool for the characterization of multicrystalline silicon solar cells. Nevertheless, one has to control the reflected light in order to obtain a reliable estimation of the electrical parameters.
First-principles Study of Back Contact Effects on CdTe Thin Film Solar Cells
Authors: Du Mao-Hua 
Published: August 2010

AbstractForming a chemically stable low-resistance back contact for CdTe thin film solar cells is critically important to the cell performance. This paper reports theoretical study of the effects of the back contact material, Sb2Te3, on the performance of the CdTe solar cells. First-principles calculations show that Sb impurities in p-type CdTe are donors and can diffuse with low diffusion barrier. There properties are clearly detrimental to the solar cell performance. The Sb segregation into the grain boundaries may be required to explain the good efficiencies for the CdTe solar cells with Sb2Te3 back contacts.
Surface Passivation of p-GaTe Layered Crystals for Improved p-GaTe/n-InSe Heterojunction Solar Cells
Authors: Mandal Krishna C. , Das Sandip , Krishna Ramesh , Muzykov Peter G. , Ma Shuguo , Zhao Feng 
Published: August 2010

AbstractGaTe and GaTe:In single crystals were grown from high purity Ga (7N) and zone refined Te (>7N) precursor materials. InSe thin films were deposited by thermal evaporation onto the sulfur passivated GaTe:In substrates at various substrate temperatures from 450K-550K to fabricate p-GaTe:In/n-InSe heterojunction solar cells. Scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray photoelectron spectroscopy (XPS) were used to characterize GaTe:In crystals and InSe thin film surfaces. The current-voltage characteristics of p-GaTe:In/n-InSe solar cells were measured under dark and under illumination of 75mW/cm2. Dark J-V measurements showed that the reverse saturation current density (J0) decreased from 3.8 x 10-6 A/cm2 to 1.5 x 10-9 A/cm2 and the ideality factor was reduced from 2.04 to 1.15 as a result of surface passivation. Under illumination of 75 mW/cm2, the open-circuit voltage (Voc) increased from 0.54V to 0.68V and short-circuit current density (Jsc) increased from 7.19 mA/cm2 to 8.65 mA/cm2 for solar cells with surface passivated GaTe:In substrates, leading to an increased solar cell efficiency of 5.03%. EPMA measurements revealed that the InSe thin films deposited at 550 K on GaTe:In substrates were near stoichiometric with enhanced grain size contributing also to better solar cell performance.
Pulsed Laser Processing of Electrodeposited CuInSe2 Photovoltaic Absorber Thin Films
Authors: Bhatia Ashish , Dale Phillip , Nowell Matt , Scarpulla Michael 
Published: August 2010

AbstractCuInSe2 (CIS) is commercially processed using energy intensive vacuum processes such as sputtering and thermal evaporation followed by thermal annealing. In order to reduce the cost of fabricating CIS photovoltaic absorber layers we need fast and cheap processing methods. We have investigated the use of non-vacuum electrochemical deposition (ED) followed by ultra violet pulsed laser annealing (UV-PLA). We report here on the results of ns pulsed KrF irradiation of ED CIS films and ED CIS films which were first annealed in a Se atmosphere.
In situ Study of Strain Relaxation Mechanisms During Lattice-mismatched InGaAs/GaAs Growth by X-ray Reciprocal Space Mapping
Authors: Sasaki Takuo , Suzuki Hidetoshi , Sai Akihisa , Takahasi Masamitu , Fujikawa Seiji , Ohshita Yoshio , Yamaguchi Masafumi 
Published: August 2010

AbstractThe in situ X-ray reciprocal space mapping (in situ RSM) of symmetric diffraction measurements during lattice-mismatched InGaAs/GaAs(001) growth were performed to investigate the strain relaxation mechanisms. The evolution of the residual strain and crystal quality were obtained as a function of InGaAs film thickness. Based on the results, the correlation between the strain relaxation and the dislocations during the film growth were evaluated. As a result, film thickness ranges with different relaxation mechanisms were classified, and dominant dislocation behavior in each phase were deduced. From the data obtained in in situ measurements, the quantitative strain relaxation models were proposed based on a dislocation kinetic model developed by Dodson and Tsao. Good agreement between the in situ data and the model ensured the validity of the dominant dislocation behavior deduced from the present study.
Growth of Metamorphic InGaP for Wide-Bandgap Photovoltaic Junction by MBE
Authors: Simon John , Tomasulo Stephanie , Simmonds Paul , Romero Manuel J , Lee Minjoo Larry 
Published: August 2010

AbstractMetamorphic triple-junction solar cells can currently attain efficiencies as high as 41.1%. Using additional junctions could lead to efficiencies above 50%, but require the development of a wide bandgap (2.0-2.2eV) material to act as the top layer. In this work we demonstrate wide bandgap InyGa1-yP grown on GaAsxP1-x via solid source molecular beam epitaxy. Unoptimized tensile GaAsxP1-x buffers grown on GaAs exhibit asymmetric strain relaxation, along with formation of faceted trenches 100-300 nm deep in the [01-1] direction. Smaller grading step size and higher substrate temperatures minimizes the facet trench density and results in symmetric strain relaxation. In comparison, compressively-strained graded GaAsxP1-x buffers on GaP show nearly-complete strain relaxation of the top layers and no evidence of trenches. We subsequently grew InyGa1-yP layers on the GaAsxP1-x buffers. Photoluminescence and transmission electron microscopy measurements show no indication of phase separation or CuPt ordering. Taken in combination with the low threading dislocation densities obtained, MBE-grown InyGa1-yP layers are promising candidates for future use as the top junction of a multi-junction solar cell.