bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of Thin Film Silicon Carbide
Authors: Jackson Kamili M. , Edwards Richard L. , Dirras Guy F. , Sharpe William N.
Published: April 2011

Silicon carbide is a very attractive material for a variety of applications. Originally considered for use in high power and high temperature electronics because of its large bandgap, designers of MEMS are now considering use of silicon carbide because of its stability at high temperatures, resistance to corrosives, high stiffness, and radiation resistance. However, as with any new structural material, its mechanical properties must be measured for design information. This research measures the elastic modulus, strength, and Poisson's ratio of two different silicon carbides using microtensile testing. One material is a 0.5-1νm thick film from Case Western Reserve University. Preliminary results give an average of 420 GPa for elastic modulus, a strength of 1.2 GPa, and a Poisson's ratio of 0.19. The second material is from Massachusetts Institute of Technology with an average thickness of 30 microns. Preliminary results show an elastic modulus of 430 GPa, a strength of 0.49 GPa, and a Poisson's ratio of 0.24. In addition to the most recent results, techniques used to obtain these results, microstructure investigations, and a comparison of the materials are detailed.
Add Ceramic “MEMS” to the Pallet of MicroSystems Technologies
Authors: Wilcox David L. , Burdon Jeremy W. , Changrani Rajnish , Chou Chia-Fu , Dai Steve , Koripella Ramesh , Oliver Manny , Sadler Daniel , Allmen Paul von , Zenhausern Frederic
Published: April 2011

Just as the 40+ years of technology developments associated with the electronic application of semiconductor fabrication processes is “morphing” into a micro-electro- mechanical systems (MEMS) technology in the past dozen years or so, so it seems may the “mature” multilayer ceramic fabrication technology associated with capacitor components and interconnect substrates for the integrated circuit industry, be morphed into MEMS – microsystems technology applications. This paper highlights work underway in Motorola Labs aimed at exploring the potential to develop 3D multilayer ceramic structures to integrate (monolithic and hybrid) multiple functions to create microsystems for wireless, energy and life science applications. By multiple functions, we refer to the ability for a microsystem to perform electronic, fluidic, thermonic, photonic and mechatronic (or actuator) based functions. Current capabilities of the multilayer ceramic materials and processes to achieve integrated functionalities for wireless applications will be described including the development of a new dielectric enabling increased performance for wireless applications. Also to be highlighted will be exploratory microscale fuel cell prototypes exploiting advances in the multilayer ceramic lamination and feature forming technologies enabling the insertion of 3D microchannels for microfluidic functions. These prototypes also feature the ability of the technology to provide thermonic functionality for microreactor devices. Feasibility of a light source that can be integrated into the technology platform hinting at photonic applications will be described. Many materials science and engineering advancements are needed to achieve the potential of this “old” but newly “morphing” technology and some of these will be noted.
Heavy-Ion Damage to Magnesium Diboride Films: Electrical Transport-Current Characterization
Authors: Kerchner H. R. , Cantoni C. , Paranthaman M. , Christen D. K. , Christen H. M. , Thompson J. R. , Miller D. J.
Published: April 2011

The use of magnesium diboride in superconducting magnets, transmission lines, or other large-scale applications depends on the transport-current characteristics of this material in magnetic field, and how they compare to the properties of conventional and high-temperature superconductors. Thin films of boron grown on sapphire substrates during electron-beam evaporation were exposed to Mg vapor to produce 0.5-μm thick layers of the metallic compound MgB2. Four-terminal measurements of their voltagecurrent relations, E(J), were carried out before and after exposure to Bφ =1-T and higher doses of 1-Gev U ions. These doses lowered critical temperatures Tc≈39 K less than 0.1 degree, raised the normal-state resistivity, and reduced the loss-free critical current density, Jc. Higher doses added little. The reduction of current densities was greater in the presence of applied magnetic field greater than 0.1 T.
Structure Characteristics of ISD Coated Conductors
Authors: Tang Y. L. , Miller D. J. , Ma B. , Koritala R. E. , Balachandran U.
Published: April 2011

The inclined-substrate deposition (ISD) method for growth of biaxially textured MgO is of interest due to its applications in coated conductors based on high-temperature superconductor (HTS). The ISD method is especially attractive since it offers the potential to produce a high–quality biaxially textured layer in a simple and efficient process. In this work, Yba2Cu3O7-x (YBCO) coated conductors based on two-step deposited MgO buffer layers (ISD and homoepitaxial) on Hastelloy tapes were examined by high-resolution electron microscopy (HREM) to study both the structure of individual layers and, especially, the interfaces between them. Special attention was paid to the MgO buffer layer because of its importance to biaxial YBCO formation. TEM investigation shows the MgO [111] direction is not parallel to the substrate normal but tilted slightly toward the deposition direction. The second layer of MgO has a good epitaxial relationship with the first layer, while dislocations were found near the interface area of the MgO layers. Twin boundaries, which are in the (111) plane, were found between the ISD MgO columns. The multi-buffer layers gave better growth of epitaxial YBCO.
Spatial Distribution Analyses of Superconducting Transition Temperature in Epitaxial YBa2Cu3O7 Film Using Variable Temperature Scanning Laser Microscopy
Authors: Seo S. , Kwon C. , Park B. H. , Jia Q. X.
Published: April 2011

The spatial distribution of superconducting properties using variable temperature scanning laser microscope (VTSLM) has been investigated. The superconducting thin film used in this study is an epitaxial YBa2Cu3O7 film photolithographically patterned to a 300 μm-wide bridge. Since the voltage response, δV(x,y) is proportional to dR/dT(x,y), the spatial distribution of superconducting transition can be obtained in VTSLM images. In the resistive transition region, there is a strong correlation between the VTSLM images and the resistance of the sample. With decreasing resistance, the area with large δV(x,y) shifts toward the ends of the bridge. This indicates that the resistive transition is not uniform and both ends of the bridge have lower transition temperature, Tc. Different currents or different output power of lasers do not affect the images. VTSLM technique is a powerful tool to image the local superconducting properties and to identify the weaker superconducting areas.
Thermodynamic Calculations in New Thermoelectric Materials. Application to Processes
Authors: Tedenac J.C. , Record M.C. , Izard V.
Published: April 2011

The processing of electronic materials and devices is an important field of application of thermodynamics. Many growth processes of semi-conductors involve vapour-solid or liquid-solid interfaces which can be considered close to the thermodynamic equilibrium. Performance enhancement of thermoelectric modules can be obtained by a good knowledge of the constitution of the materials involved in their fabrication. Its requires a relevant thermodynamic analysis of the material.Making these optimized thermoelectric materials require at least three elements being thermoelectric materials typically multicomponent systems which are usually studied by a CALPHAD analysis of the relevant systems. All these problems are related to the thermodynamic quantities of species involved in the materials such as activities and free energy functions of electrons, holes and components.

In this paper we present a contribution to a better understanding of antimony based thermoelectric materials by a CALPHAD approach.
Thermoelectric Properties of Eu-doped CoSb3
Authors: Lamberton G. A. , Tedstrom R. H. , Tritt Terry M. , Nolas G. S.
Published: April 2011

Resistivity and thermopower data is presented on Eu-doped CoSb3 skutterudites over the temperature range of 10 K to 700 K. Thermal conductivity is also presented from 10 K to 300 K in order to determine the figure of merit. Eu0.43Co4Sb11.59Ge0.31 and Eu0.42Co4Sb11.37Ge0.50 exhibit an enhanced figure of merit as compared to CoSb3 and Eu0.2CoSb3. Data on a series of Yb-filled CoSb3 is underway and preliminary data is presented.
Synthesis and Thermoelectric Properties of CoP3
Authors: Shields Virgil B. , Caillat Thierry
Published: April 2011

In an effort to expand the range of operation for highly efficient, segmented thermoelectric unicouples currently being developed at the Jet Propulsion Laboratory (JPL), skutterudite phosphides are being investigated as potential high temperature segments to supplement antimonide segments that limit the use of these unicouples at a hot-side temperature of about 873-973 K. We report here on the synthesis and transport properties of one of these phosphide skutterudite materials, CoP3. Large amounts of cobalt triphosphide have been prepared by direct reaction from stochiometric powders at synthesis temperatures ranging from 873 to 1223 K. The synthesized powders were analyzed by x-ray diffractometry and hot pressed at 1273 K. The samples were analyzed by microprobe analysis and electrical conductivity, Seebeck voltage and thermal conductivity measurements were performed. The thermoelectric properties are presented and discussed as a function of temperature up to 1000 K. Initial thermal stability results are presented to assess the potential of this material for high temperature operation.
Reductions in the Lattice Thermal Conductivity of Ball-milled and Shock compacted TiNiSn1−XSbXHalf-Heusler alloys
Authors: Bhattacharya S. , Xia Y. , Ponnambalam V. , Poon S.J. , Thadani N. , Tritt T.M.
Published: April 2011

Half-Heusler alloys are currently being investigated for their potential as thermoelectric materials [1], [2]. They exhibit high negative thermopower (40-250μV/K) and favorable electrical resistivity (0.1-8mW•cm) at room temperature. Attractive power factors (α2σT) of about (0.2-1.0W/m•K) at room temperature and about 4W/m•K at 600K [3] have been reported in these materials. But in order to achieve a high figure-of-merit in the half-Heusler alloys, the relatively high thermal conductivity in these materials (∼ 10 W/m•K) must be reduced. The thermal conductivity in these materials is composed of mainly a lattice contribution, compared to a very small electronic component. The challenge is to reduce the relatively high lattice thermal conductivity in these materials. Reported in this paper is a significant reduction of lattice thermal conductivity (∼1.5 - 3.5W/m•K) in some Ti-based half-Heusler alloys. Samples have been prepared by ball milling and followed by shock-compaction that has resulted into reduced grain sizes in these materials. The effects of the microstructure on the thermal transport properties of the Half-Heusler alloys have been investigated and are presented and discussed herein.
Temperature and Thickness Dependences of Thermoelectric Properties of PbS/EuS Bilayers
Authors: Rogacheva Elena I. , Grigorov Sergey N. , Tavrina Tatyana V. , Nashchekina Olga N. , Vekhov Yegor O. , Sipatov Alexander Yu. , Volobuev Valentine V. , Dresselhaus Mildred S.
Published: April 2011

A non-monotonic character of the dependences of the thermoelectric properties of PbS/EuS/(001)KCl heterostructures on the PbS layer thickness d (d = 2 – 200 nm) was detected. Pronounced extrema at d ∼ 15 nm and less distinct extrema at d ∼ 30 nm and d ∼ 100 nm were observed. It is suggested that the complex character of the dependences is caused by the competition between percolation phenomena and size quantization. The critical exponent for the electrical conductivity (t = 1.6 ± 0.15) is determined.
The Performance of a Segmented Thermoelectric Convertor Using Yb-Based Filled Skutterudites and Bi2Te3-Based Materials
Authors: Matsubara Kakuei
Published: April 2011

This paper reports an overview of the current state in our research program started in 1995 in collaboration with industries. This program has been aimed at making sure of the feasibility of a thermoelectric convertor for waste heat recovery of gasoline engine vehicle. Major results obtained include: (1) updated ZT-values for Pd,Pt-doped CoSb3 and partially Yb-filled skutterudite antimonides YbyM4Sb12 (M=Co, Fe, Ni; 0<y<1), (2) the performance of thermoelectric convertor using a segmented module of the skutterudites and Bi2Te3-based alloys, (3) a preliminary test of a thermoelectric stack which is the united device of thermoelectric modules and heat exchanger, when properly installed in a 2000cc class automobile.
Precise control of CVD-ZrO2 film properties based on kinetic information.
Authors: Kawamoto Takashi , Shimogaki Yukihiro
Published: April 2011

ZrO2 films were investigated as high-k gate insulators for possible gate dielectric applications. These thin films were deposited by chemical vapor deposition (CVD). We had investigated kinetics of ZrO2-CVD reaction system and thermal stability of ZrO2 film deposited from zirconium-tetra-tertiary-butoxide (ZTB) and tetrakis-diethylamio-zirconium (TDEAZ) as Zr source. In the case of ZTB, ZTB decomposed into two active intermediate precursors by gas phase reaction. These intermediate precursors also contributed to the film growth. The step coverage, the contents of carbon and oxygen, and film structures depended on the growth precursor contributed to the film growth. Film structures also depended on the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into cubic and then into monoclinic. However, in the case of the films deposited at 300°C, the film structure kept amorphous state after 900°C annealing. On the other hand, in the case of TDEAZ, TDEAZ directly deposited on the growing surface and the decomposition of TDEAZ by gas phase reaction did not exist. The films deposited by TDEAZ contained more carbon than by ZTB. The film structure kept amorphous state independent of the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into monoclinic and then into amorphous again. This structural change resulted from the decrease of the impurity contents of the residual nitrogen and the residual carbon and the increase of the content of silicon diffused from the substrate in the ZrO2 films.
Nanostructured Ultrathin Films of Silicate Clay and Polyelectrolytes: Deposition Parameters and Mechanical Properties by Nanoindentation
Authors: Fan Xiaowu , Advincula Rigoberto C.
Published: April 2011

Recently, we have investigated the electrostatic layer-by-layer (ELBL) deposition of polycation and clay platelet ultrathin films. We have investigated the properties of these films using techniques such as ellipsometry, X-ray diffraction and atomic force microscopy (AFM). In this work, we report our results regarding the formation of this type of hybrid ultrathin films focusing on their mechanical properties as probed by nanoindentation experiments. Structural information such as film thickness, platelet coverage, surface morphology, roughness, etc., is important parameters for their potential use as coatings. We have investigated the relationship of several of these parameters with their mechanical hardness and modulus properties as a function of indentor probe depth in nanoindentation experiments. The ultrathin films have remarkable mechanical properties very different from most polymer ultrathin films.
Cross-sectional phase analysis of single crystalline silicon indented by Rockwell indenter
Authors: Kim Sung-Soon , Oh Han-Seog , Jeong Seong-Min , Lee Hong-Lim
Published: April 2011

This study of the indentation behavior of Si has revealed a complex process of mechanical deformation. As loading time increased, Si-XII and Si-III disappeared and only a-Si appeared in (111) samples. As loading time increased, crack was generated and residual stress was removed. At fast loading rate, the deformation behavior appears predominantly elastic. On the contrary, at slow loading rate, catastrophic plastic deformation occurred during loading stage.

We have observed crack behavior which occurred under spherical indentation in crystalline silicon. Method which was used in our research for cross-sectional observation exaggerated generation and propagation of cracks. Our method prepares to observe crack behavior. But it is not profit to observe to phase transformation
Assessment of Microscale Test Methods of Peeling and Splitting along Surface of Thin-Film/Substrates
Authors: Wei Y.
Published: April 2011

Peel test methods are assessed through being applied to a peeling analysis of the ductile film/ceramic substrate system. Through computing the fracture work of the system using the either beam bend model (BB model) or the general plane analysis model (GPA model), surprisingly, a big difference between both model results is found. Although the BB model can capture the plastic dissipation phenomenon for the ductile film case as the GPA model can, it is much sensitive to the choice of the peeling criterion parameters, and it overestimates the plastic bending effect unable to capture crack tip constraint plasticity. In view of the difficulty of measuring interfacial toughness using peel test method when film is the ductile material, a new test method, split test, is recommended and analyzed using the GPA model. The prediction is applied to a wedge-loaded experiment for Al-alloy double-cantilever beam in literature.
Superlubricity and Wearless Sliding in Diamondlike Carbon Films
Authors: Erdemir Ali
Published: April 2011

Diamondlike carbon (DLC) films have attracted great interest in recent years mainly because of their unusual optical, electrical, mechanical, and tribological properties. Such properties are currently being exploited for a wide range of engineering applications including magnetic hard disks, gears, sliding and roller bearings, scratch resistant glasses, biomedical implants, etc. Systematic studies on carbon-based materials in our laboratory have led to the development of a new class of amorphous DLC films that provide extremely low friction and wear coefficients of 0.001 to 0.005 and 10-11 to 10-10 mm3/N.m, respectively, when tested in inert-gas or high-vacuum environments. These films were produced in highly hydrogenated gas discharge plasmas by a plasma enhanced chemical vapor deposition process at room temperature. The carbon source gases used in the deposition of these films included methane, acetylene, and ethylene. Tribological studies in our laboratory have established a very close correlation between the composition of the plasmas and the friction and wear coefficients of the resultant DLC films. Specifically, the friction and wear coefficients of DLC films grown in plasmas with higher hydrogen-to-carbon ratios were much lower than films derived from source gases with lower hydrogen-to-carbon ratios. Fundamental tribological and surface analytical studies have led us to conclude that hydrogen (within the film, as well as on the sliding surfaces) is extremely important for the superlubricity and wearless sliding behavior of these films. Based on these studies, a mechanistic model is proposed to explain the superlow friction and wear properties of the new DLC films.
Preferential Adhesion of Gold Nanoparticles Using Lithographically Patterned Substrates
Authors: Pihl Johan , Kabir Mohammad S. , Magnus S.H.
Published: April 2011

A method of aligning small amounts of colloidal particles between narrowly spaced electrodes using a combination of conventional nanofabrication and self-assembled monolayers has been developed. Transport measurements were performed on several devices
High Density Hexagonal Nickel Nanowire Arrays with 65 and 100 nm-PERIOD
Authors: Nielsch Kornelius , Wehrspohn Ralf B. , Fischer Saskia F. , Kronmüller Helmut , Barthel Jochen , Kirschner Jürgen , Schweinböck Thomas , Weiss Dieter , Gösele Ulrich
Published: April 2011

Highly ordered alumina pore channel arrays are used as templates for the fabrication of magnetic nanowire arrays. These well-defined templates are based on the approach by Masuda and Fukuda and have an interpore distance of 65 and 100 nm and a monodisperse pore diameter of ≍30 nm. The pore channels are hexagonally arranged in 2D-domains, which extend over more than ten interpore distances. Nearly 100% metal filling of the alumina pore structures is obtained by a novel pulsed electrodeposition technique. Due to the high ordering degree of the nanowires arrays, we detect a squareness of ≍100% and coercive fields of 1200 Oe in the direction of the nanowires. The MFM measurements have been carried out by applying magnetic fields on magnetized and demagnetized samples to study the switching behavior of individual nanowires inside the arrays. Magnetic wires have been locally switched by a strong MFM tip and a variable external magnetic field. The MFM results show a good agreement with the bulk magnetic hysteresis loops.
Chiral Polyalkylthiophenes for Organic Light Emitting Diodes
Authors: Lebon F. , Longhi G. , Abbate S. , Catellani M. , Luzzati S. , Bolognesi A.
Published: April 2011

Chiral polyalkylthiophenes are noncentrosymmetric organic materials which can be used both in second harmonic-generation devices and in polarized light emitting diodes. In this work we present the synthesis and the characterization of a polyalkylthiophene with a chiral center very close to the conjugated backbone: poly(3-[(S)-2-methylbutyl]thiophene) (PMBT). Circular dichroism (CD) measurements have been carried out to ascertain the chirality of these materials. The CD spectra show intense signals both in mixed solvents and in the solid state. The strong Cotton effect can be associated to a highly ordered aggregated phase whose nature is still under investigation. We also present the photo and electroluminescence characterization of single layer light emitting diode (LED) with the following configuration: ITO (Tin Indium Oxide)/PMBT/Al.
Highly Sensitive Optical Sensors Using Electrospun Polymeric Nanofibrous Membranes
Authors: Wang Xianyan , Lee Soo-Hyoung. , Drew Christopher , Senecal Kris J. , Kumar Jayant , Samuelson Lynne A.
Published: April 2011

In recent years, polymer films have found an increasing role in sensors due to their unique characteristics. It is widely accepted that the sensitivity of a film is proportional to the surface area per unit mass. Thin films with very large surface areas can be easily fabricated by electrospinning, wherein a polymer solution is exposed to a high static voltage, creating sub-micron or nanometer scale fibers collected as a non-woven membrane. Electrospun nanofibrous membranes have surface areas approximately one to two orders of the magnitude higher than those found in continuous thin films. It is expected that their sensitivities are potentially as large. In this paper, the first use of an electrospun membrane as a highly responsive fluorescence quenching-based optical sensor is reported. A new fluorescent polymer, polyacrylic acid - poly (pyrene methanol) (PAA-PM), was synthesized via covalent attachment of the fluorescent indicator, pyrene methanol (PM), onto polyacrylic acid (PAA). Optical chemical sensors were then fabricated by electrospinning PAA-PM and thermal crosslinkable polyurethane latex mixture solutions. The synthesis, characterization, electrospinning fabrication, and comparison of the sensitivities to analytes such as ferric ions, mercury, and 2,4-dinitrotoluene between the electrospun membranes and electrostatically layer-by-layer (ELBL) assembled films are presented.
Growth and Morphology of Pentacene Films on Oxide Surfaces
Authors: Ruiz Ricardo , Feldman Leonard C. , Haglund Richard F. , McKee Rodney A. , Koch Norbert , Nickel Bert A. , Pflaum Jens , Scoles Giacinto , Kahn Antoine
Published: April 2011

Pentacene thin films were grown in ultra high vacuum on amorphous SiO2 and on a high dielectric constant material, crystalline BaTiO3. During pentacene deposition, substrates were held at three different temperatures (-650, 250 and 750 C). In general, three different morphologies were identified: a first closed interfacial layer, a thin film mode composed of faceted grains with single molecule step height, and a volume mode with features substantially higher than those of the thin film mode. Analysis was carried out by atomic force microscopy and in some cases by synchrotron X-ray diffraction.
Photo-Electron Spectroscopy Study of Energy Levels in Conjugated Oligomers
Authors: Veenstra S.C. , Heeres A. , Stalmach U. , Wildeman J. , Hadziioannou G. , Sawatzky G.A. , Jonkman H.T.
Published: April 2011

We report on the valence orbital structure of poly(para-phenylenevinylene) (PPV)-like oligomers. We studied these molecules as isolated oligomers in the gas phase, as well as in thin films deposited on metal substrates. We use a simple model based on a previously reported Hamiltonian that accurately describes the development of the low lying electronic excitations as a function of the number of repeating units. In the study on the thin organic films we report on the energy level alignment at metal / organic and organic / organic interfaces, where the organic layer is either a PPV-like oligomer or C60. The results are important for understanding organic photovoltaic devices.
Fabrication of refractive index and relief gratings in polymer films for DFB lasers
Authors: Kavc T. , Langer G. , Kern W. , Kranzelbinder G. , Toussaere E. , Turnbull G.A. , Samuel I.D.W. , Iskra K.F. , Neger T.
Published: April 2011

A styrene copolymer of 4-vinylbenzyl thiocyanate (PST-co-VBT) was employed as recording material for optical interference patterns with periods ∧ < 1 μm. Using lower intensity laser irradiation (4 mJ cm-2, λ = 266 nm), refractive index gratings were produced in PST-co-VBT by an UV induced photoisomerization SCN - NCS. Subsequent modification of the patterns with gaseous amines yielded surface relief gratings via the formation of derivatives of thiourea. Laser irradiation with higher pulse energies (7 mJ cm-2, λ = 266 nm) directly produced surface relief gratings (modulation depth 30 nm). These gratings were also reactive towards amine reagents and allowed a selective functionalization of the grooves of the relief (“reactive gratings”). Optically inscribed gratings in PST-co-VBT were employed as optical resonators for distributed feedback (DFB) lasing. With a laser dye (DCM) dissolved in PST-co-VBT, optically pumped DFB laser action was observed after inscribing index and relief gratings. The pumping threshold for lasing Ith was 250 nJ cm-2 at λ = 532 nm.
Influence of Thermal Aging on the Mechanical and Corrosion Properties of GTAW Welds of Alloy N06022
Authors: Summers Tammy S. Edgecumbe , Rebak Raúl B. , Palmer Todd A. , Crook Paul
Published: April 2011

The phase stability of C-22 alloy (UNS N06022) gas tungsten arc welds was studied by aging samples at 593, 649, 704, and 760°C for times up to 6,000 hours. The tensile properties and the Charpy impact toughness of these samples were measured in the as-welded condition as well as after aging. The corrosion resistance was measured using standard immersion tests in acidic ferric sulfate (ASTM G 28 A) and 2.5% hydrochloric acid solutions at the boiling point. The microstructures of weld samples were examined using scanning electron microscopy (SEM). Precipitate volume fraction measurements were made using optical microscopy.

Degradation of the mechanical and corrosion properties of C-22 welds due to aging at all temperatures investigated was seen to occur sooner than was seen in C-22 base metal. An evaluation of the kinetics of nucleation and growth of the precipitates forming at these temperatures, however, indicated that no significant changes in TCP phase morphology would occur at temperatures below approximately 300°C.a
Building the Safety Case for a Disposal Facility for Spent Fuel, HLW and Long-lived ILW in Switzerland
Authors: Smith Paul A. , Zuidema Piet , Johnson Lawrence H. , Schneider Jürg W. , Gribi Peter
Published: April 2011

This paper describes a generic methodology for building the safety case for a geological repository, which is currently being applied to a possible facility for spent fuel, vitrified highlevel waste and long-lived intermediate-level waste in the Opalinus Clay of Northern Switzerland. The methodology involves:

1. the identification of certain basic disposal principles,

2. the choice of a disposal system, via a flexible repository development strategy,

3. the derivation of the system concept, based on current understanding of the phenomena that characterise, and may influence, the disposal system and its evolution,

4. the derivation of a safety concept, based on reliable, well understood and effective pillars of safety,

5. the illustration of the radiological consequences of the disposal system through the definition and analysis of a wide range of assessment cases, and

6. the compilation of the arguments and analyses that constitute the safety case, as well as guidance for future stages of the repository programme. A range of measures, including audits, are used to promote completeness of the phenomena considered in the safety case, and to avoid inadvertent bias.
Diffusion and Sorption of Radioactive Cesium and Cobalt in Regolith Materials of Central Australia
Authors: Itakura Takashi , Leo Chin Jian , McOrist Gordon D. , Payne Timothy E.
Published: April 2011

Diffusion and sorption are potentially the most important factors governing the transport of radionuclides in clays and under stationary subsurface environmental conditions. Preliminary studies have been performed to measure the transport of 137Cs and 60Co with no advection, using reconstituted samples of three regolith materials collected from a region in South Australia. The samples were saturated with CaSO4 solution to imitate the pore water chemistry of the in situ environment. A double diffusion cell testing apparatus made of polycarbonate resin was used to measure the transport of the selected radionuclides through the samples. A curve fitting procedure employing one-dimensional contaminant equations with a “stop-start” technique was used to estimate the diffusion (D) and sorption coefficients (Kd) from the measured concentration-time profiles. Results from these experiments are compared with those obtained from batch sorption tests.
The Redox Environment of Deep Groundwaters Associated with the Tono Uranium Deposit, Japan
Authors: Arthur Randy , Iwatsuki Teruki , Hama Katsuhiro , Amano Kenji , Metcalfe Richard , Ota Kunio
Published: April 2011

An unconformity underlying the Tono uranium deposit in central Japan represents the approximate location of a redox front separating relatively oxidizing groundwaters (Eh ≈0 mV) in the weathered, fractured Toki granite (TG) from strongly reducing pore fluids (Eh ≈-360 mV) in sedimentary rocks of the overlying Lower Toki Lignite-bearing Formation (TL). Uranium has been effectively immobilized in the TL during the past 10 million years. Stable and reversible redox potentials measured in-situ in boreholes penetrating the sedimentary rocks and granite appear to be controlled by the Fe(III)-oxyhydroxide – Fe2+ redox couple. A simplified analytical model of front migration suggests that chemical buffering by pyrite alone would limit the propagation velocity of the front into the TL to less than 8x10−6 m yr−1. The model is constrained by Darcy fluxes derived from groundwater flow models and relative 14C groundwater ages, average modal abundances of pyrite in the TL, and the analytical detection limit for dissolved oxygen in TG groundwaters (2 ppm). Model results also suggest that the redox buffering capacity of the TL would be exhausted within 10 million years if an upper bound O2(aq) concentration in TG groundwaters fixed by equilibrium with atmospheric O2(g) (8.5 ppm) is assumed. Immobilization of uranium in the TL is thus attributable to oxidation-reduction reactions that minimize O2(aq) concentrations primarily in the TG, and secondarily in the TL.
Application of the Systems Analysis Approach to a Natural Analogue Project
Authors: Stenhouse M.J. , Arthur R. , Ota K. , Iwatsuki T. , Metcalfe R. , Takase H.
Published: April 2011

The Tono uranium deposit (Gifu Prefecture, central Japan) was formed about 10 million years ago and available evidence suggests that this deposit has remained stable, i.e. uranium has not migrated significantly since then. Substantial field and modeling work is being carried out to better understand the hydrogeological and geochemical processes affecting or governing uranium transport and immobilization in and around the Tono uranium deposit. A systems analysis approach has been applied to the Tono deposit natural analogue project. Application of a systems analysis approach to a generic research project is novel and is different from prevailing applications. Previous applications of a systems analysis approach have been principally concerned with performance and safety assessments for radioactive waste disposal. The systems analysis approach provides a convenient framework for this project, having been used in the Tono Natural Analogue Project (TAP) to:

• define the system to be studied;

• identify features, events and processes (FEPs) associated with this system;

• identify external factors (EFEPs) which are likely to have influenced the Tono area or study site or uranium deposit;

• define interactions between pairs of FEPs; and

• develop credible scenarios for evolution of the area or uranium deposit.

The results from the systems analysis approach allow us to:

• develop possible scenarios for how the Tono area or study site evolved,

• evaluate uncertainty and how it propagates backwards in time,

• link field characterization data with predictive modeling, and

• identify gaps in data and, hence, identify additional characterization needs.
A Solid Solution Model for Sorption of Radionuclides in Cement
Authors: Emrén Allan T.
Published: April 2011

of these two main phases in cement, portlandite is rather compact while the gel phase has a very irregular morphology, probably fractal. This work essentially deals with sorption that takes place as absorption in the gel phase, but the same theory is applicable for any of the phases present in cement. It is also able to handle sorption in any combination of phases in the cement. A model for multi component solid mixtures has been developed, essentially following the Guggenheim excess free enthalpy approach. Measurement of Kd for one gel composition makes it possible to calculate Kd values during the entire process of cement degradation. The main limitation is that the concentration of the radionuclide has to be low enough for all higher terms in the series expansion to be negligible. The model is mostly valid for elements forming cations and it also requires the sorbed element to form a compound of reasonably low solubility with one of the anions in cement (hydroxide or silicate). Kd values for Ni in cement has been taken from the literature and used to illustrate the model.
Mechanical Testing of Electrotextile Cables and Connectors
Authors: Slade Jeremiah , Wilson Patricia , Farrell Brian , Teverovsky Justyna , Thomson Douglas , Bowman Jeremy , Agpaoa-Kraus Marty , Horowitz Wendy , Tierney Edward , Offray C. M. , Winterhalter Carole
Published: April 2011

Today's complex geo-political climate has forced the U.S. armed services into new operational strategies. The prevalence of international terrorism, the threat from chemical and biological weapons, and the pressure to “do more with less” has placed increasing demands on the military. This new operational environment requires highly mobile troops having enhanced decision-making capability provided through the rapid transfer and dissemination of information to each member of the squad. What is missing is the ability to process and use this information via an Intranet at the level of the individual soldier. The purpose of our work has been to develop, evaluate and implement such a wearable conductive network for the dismounted soldier.
Ionic Liquid Based Gel Electrolyte Compositions for Dye Sensitized Solar Cells
Authors: Chittibabu K. G. , Hadjikyriacou S. , Li L.
Published: April 2011

Konarka Technologies has developed efficient electrolyte compositions based on nonvolatile ionic liquids. The electrolyte compositions were subsequently gelled using a metal ion complexation technique, without compromising the photovoltaic performance of the dye sensitized solar cells (DSSCs). The photovoltaic performance of the gel electrolyte incorporated DSSCs is quite stable for extended period of time even in the absence of sealing. Detailed results on performance and stability of the gel electrolyte incorporated DSSCs are presented.
Polymer-on-Polymer Stamping on Micro- and Nano-Scales
Authors: Gourdin Shoshana , Crites Travis , Coe Seth , Bulovic Vladimir , Hammond Paula
Published: April 2011

The goal of the project was to determine whether PDAC (poly (diallyldimethylammonium chloride), also abbreviated PDADMAC) could be printed reproducibly to create patterns with a sub-micron resolution. PDAC was stamped onto bare silicon using PDMS stamps having features only about 150 nm wide. A variety of aqueous PDAC inks were tried, to study the effect of concentration and ionic strength on the pattern produced. In order to get good prints, new stamping techniques were also required. A rigid stamping apparatus was built to ensure steady placement, and the stamps were spin coated with a different ink solution to produce thin, even coats of ink. [1] Using these methods, the pattern transferred.
Effect of Process Variables and Dopants on Characteristics of Electrochemically-Deposited Pedot Films
Authors: Oka Mihir A. , Hardaker Stephen S. , Nazir Farzad , Gregory Richard V. , Brenneman Keith R. , Lessner Philip M.
Published: April 2011

Poly(3,4-ethlyenedioxythiophene), PEDOT, has found wide use in applications such as electrostatic coatings, antistatic layers and electrode materials in electronic devices. Electrochemical deposition of PEDOT is a prominent means of obtaining thin, uniform films. However, the relationship of these films' properties to their morphological structure is still poorly understood. We have prepared PEDOT films by electrochemical oxidation of monomer (3,4-ethylenedioxythiophene), EDOT, under constant current conditions, employing a variety of electrolytes, and processing conditions. We report the effect of using different dopants, deposition time, deposition temperature and current density on the observed conductivity of PEDOT films. Atomic force microscopy studies were carried out to determine the possible effect of the process variables on the resulting film morphology. Also, the effect of residual solvent on the conductivity of the films was studied by thermogravimetric analysis (TGA).
Giant exciton-light coupling in large size semiconductor quantum dots
Authors: Gil Bernard , Kavokin Alexey V.
Published: April 2011

We investigate the strength of the coupling of the electronic states with the electromagnetic field in semiconductor nanospheres, taking into account the retardation effect. We show that the coupling strength is particularly strong: the bulk properties are so enhanced that the radiative decay time can reach some 30 picoseconds for quantum dots sizes of some 30 nm.
Observation of Quantum Confinement Effects in Nanocrystalline Silicon Dot Floating Gate Single Electron Memory Devices
Authors: Huang Shaoyun , Banerjee Souri , Oda Shunri
Published: April 2011

Electron charging and discharging processes in floating gate MOS memory based on nanocrystalline silicon (nc-Si) dots were investigated at room temperature using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Sequential electron discharging processes from nc-Si dots manifest themselves clearly in G-V spectroscopy after charging of the dots. According to the conductance peak structure resulting from the Coulomb blockade as well as quantum confinement effects of nc-Si dots, electron-addition energy is estimated to be 50 meV. Taking the electron-charging energy between the silicon substrate and the floating dot (30 meV) into account, the quantum confinement energy is found to be comparable to the electron charging energy for an nc-Si dot of 8 nm in diameter embedded in the silicon oxide.
Self-assembled Si/Ge quantum dot structures for novel device applications
Authors: Brunner K. , Bougeard D. , Janotta A. , Herbst M. , Tan P. H. , Riedl H. , Stutzmann M. , Abstreiter G.
Published: April 2011

The band structure of self-assembled Si/Ge quantum dot structures deposited by molecular beam epitaxy in the Stranski Krastanov growth mode is characterized by optical and electrical spectroscopy. Interband and intraband absorption, photocurrent, photoluminescence, Raman and admittance spectroscopy of structures with quantum dots of about 20 nm lateral size offer insight into the discrete level scheme within the valence band, the optical transitions and the lifetime of localized hole states. The results are discussed with respect to their possible applications in infrared light detection, storage and quantum-logic devices.
Diffusional Coating of Nanoparticles
Authors: Lavine James P.
Published: April 2011

The time-dependent diffusion of particles to an absorbing sphere is investigated with three random walk models. The first uses consecutive independent particles and finds the capture time distributions are exponential for a range of values of the surface absorption probability. The next two models are of the ensemble variety and assume that only a finite number of particles may be absorbed by the sphere. These models investigate depletion effects and concentration dependence. The latter is probed by varying the initial number of diffusing particles. It is found
Two-dimensional Epitaxial Growth of Strained InGaAs on GaAs (001)
Authors: Wen Hong , Wang Zhiming , Salamo G.J.
Published: April 2011

Molecular beam epitaxy growth of lattice mismatched In0.53Ga0.47As / GaAs(100) system is studied by in situ scanning tunneling microscope (STM) and reflection high energy electron diffraction. InGaAs layers with a thickness ranging up to 250 nm do not exhibit a smooth surface when grown under In-rich conditions. RHEED and STM confirm the well-ordered (4×2) reconstruction and mono-layer steps associated with this unique planar growth mode. Large STM scans reveal a characteristic morphology of rectangular shaped islands distributed on large flat terraces which are typically more than 300 nm width but only mono-layer steps.
Fabrication of Si-Ge Compound Nanowires by the FZ Melting Vapor Method
Authors: Hu Quanli , Araki Hiroshi , Suzuki Hiroshi , Ishikawa Nobuhiro , Yang Wen , Noda Tetsuji
Published: April 2011

A simple method, floating zone melting vapor, was used for fabricating nanowires of Si-Ge material. Single-crystalline nanowires were successfully synthesized. TEM images of these nanowires indicated that each nanowire consists of an inner single-crystalline core and an outer layer. An observation using high-resolution transmission electron microscopy (HRTEM) showed that almost all nanowires have a similar growth orientation to the crystalline core: [210]. The coexistence of germanium-self-catalyzed and oxide-assisted mechanisms has also been suggested.
Electrical Properties of Thin Nitrogen-Doped Ultrananocrystalline Diamond Films
Authors: Polyakov V.I. , Rukovishnikov A.I. , Pimenov S.M. , Carlisle J.A. , Gruen D.M.
Published: April 2011

The electrical properties of ultrananocrystalline diamond (UNCD) films of approximately 1μm thickness were studied. UNCD films were deposited on p-type Si substrates from CH4/Ar/N2 gas mixtures using microwave plasma CVD techniques. It was found that the UNCD films with higher nitrogen concentration and higher electron conductivity have substantially higher concentration of shallow levels with activation energy of about 0.05 eV. The change of concentration, activation energy and capture cross-section of nitrogen-induced levels for UNCD films synthesized using different nitrogen concentration in the plasma was studied by charge– based deep level transient spectroscopy.
Direct Synthesis of Silicon Nanowires using Silane and Molten Gallium
Authors: Sharma Shashank , Sunkara Mahendra K. , Dickey Elizabeth C.
Published: April 2011

We report for the first time, bulk synthesis of single crystalline silicon nanowires using molten gallium pools and an activated vapor phase containing silane. The resulting silicon nanowires were single crystalline with <100> growth direction. Nanowires contained an unexpectedly thin, non-uniform oxide sheath determined using high-resolution Transmission Electron Microscopy (TEM). Nanowires were tens of nanometers in diameter and tens to hundreds of microns long. The use of activated gas phase chemistry containing solute of interest over molten metal pools of low-solubility eutectics such as gallium offer a viable route to generate nanowire systems containing abrupt compositional hetero-interfaces.
Microstructure of the Silicon Film Prepared Near the Phase Transition Regime from Amorphous To Nanocrystalline
Authors: Zhang Shibin , Liao Xianbo , Xu Yanyue , Hu Zhihua , Zeng Xiangbo , Diao Hongwei , Luo Muchang , Kong Guanglin
Published: April 2011

A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) near the phase transition regime from amorphous to nanocrystalline. The microstructural properties of the films have been investigated by the micro-Raman and Fourier transformed Infrared (FT-IR) spectra and atom force microscopy (AFM). The obtained Raman spectra show not only the existence of nano-scaled crystallites, but also a notable improvement in the medium-range order of the diphasic films. For the FT-IR spectra of this kind of films, it notes that there is a blueshift in the Si-H stretching mode and a redshift in the Si-H wagging mode in respect to that of typical amorphous silicon film. We discussed the reasons responsible for these phenomena by means of the phase transition, which lead to the formation of a diatomic hydrogen complex, H2* and their congeries.