bluuebunny/crossref_metadata_2025_split huggingface dataset:
Void Formation in Neutronand Ion-Irradiated Copper and Nickel
Authors: Shimomura Y. , Mukouda I. 
Published: April 2011

AbstractIn copper which was irradiated by fission neutrons at 300°C in a temperature controlled rig to 0.0003 dpa with the damage production rate of 6 × 10−5 dpa/hr, the number of voids exceeds the number of gas atoms of hydrogen and helium which were generated by the transmutation reaction. The number density of voids was almost the same in as-received and gas-atomremoved copper which was neutron irradiated to 0.0003 dpa. These results suggest that voids can be formed by clustering of only vacancies. In 5 MeV Ni-ion irradiated copper, voids could not be observed in specimens which were irradiated between 200°C and 450°C from 0. 1 dpa to 30 dpa with the damage production rate of 6 dpa/hr. Voids were observed only in copper which was Ni-ion irradiated at 500°C. The difference of void formation on neutron-irradiation and ionirradiation is discussed. It is concluded that the production rate of damage is an important factor on the void formation in irradiated metals.
Plasticity and Microstructure of Irradiated Pd
Authors: Baluc N. , Dai Y. , Victoria M. 
Published: April 2011

AbstractSingle crystalline specimens of pure Pd have been irradiated at ambient temperature with 590 MeV protons to doses ranging between 10−4 and 10−1 dpa. Tensile deformation experiments revealed that irradiation induces hardening and embrittlement, while scanning (SEM) and transmission electron microscopy (TEM) observations showed that plastic deformation of specimens irradiated to a dose ≥ 10−2 dpa is strongly localized and yields the creation of slip bands at the macroscopic scale and of defect-free channels at the microscopic level.
Isotopic Tailoring to Optimize Studies for Radiation Resistance in Fusion Materials: Small Specimen Technology Development
Authors: Ohnuki S. , Shiba K. , Kohno Y. , Kohyama A. , Robertson J. P. , Hamilton M. L. , Gelles D. S. 
Published: April 2011

AbstractSingle variable experiments are being conducted to study effects of H/He/dpa on properties based on isotopically tailored alloys. 54Fe has been used to prepare an isotopically tailored duplicate of the commercial steel F82H, and a small number of TEM disks have been irradiated in order to study radiation embrittlement. From single disk specimens, mechanical properties were obtained using a shear punch technique that produces a 1 mm blank from the 3 mm disk, and microstructural information was obtained from the 1 mm blanks thinned to electron transparency.
Effective Interactions Approach to Phase Stability in Alloys Under Irradiation
Authors: Enrique Raúl A. , Bellon Pascal 
Published: April 2011

AbstractPhase stability in alloys under irradiation is studied considering effective thermodynamic potentials. A simple kinetic model of a binary alloy with phase separation is investigated. Time evolution in the alloy results from two competing dynamics: thermal diffusion, and irradiation induced ballistic exchanges. The dynamical (steady state) phase diagram is evaluated exactly performing Kinetic Monte Carlo simulations. The solution is then com- pared to two theoretical frameworks: the effective quasi-interactions model as proposed by Vaks and Kamishenko, and the effective free energy model as proposed by Martin. New developments of these models are proposed to allow for quantitative comparisons. Both theoretical frameworks yield fairly good approximations to the dynamical phase diagram.
Md Investigation of Thermal Spike Effects on Defect Production and Disordering by Displacement Cascades in Nl3AL
Authors: Gao F. , Bacon D. J. 
Published: April 2011

AbstractMolecular dynamics (MD) simulations are used to obtain detailed information on defect production and disordering produced in the primary cascade state of radiation damage in Ni3AI as a function of irradiation temperature, Tirr Although the number of Frenkel pairs decreases with increasing Tirr, the size of interstitial clusters and the interstitial clustering fraction increase with Tirr. The number of antisites defects per cascade increases by about 20% as Tir increases from 100 to 600K, and then by about 90% from 600 to 900K due to the increase in the intensity and lifetime of the thermal spike. The average size of disordered zones at different Tir, is compared with experimental transmission electron microscopy data and the results are in reasonable agreement. The long-range order parameter in the cascade region is found to be consistent with values obtained experimentally on Ni3A1 irradiated by ions to a similar dose. The chemical short-range order parameter is about 0.6 over the whole range of Tirr, considered, suggesting that the cascade core retains some short-range order at high temperature due to local reordering.
Ceramic SFF by Direct and Indirect Stereolithography
Authors: Chu Gabriel T-M. , Brady G. Allen , Miao Weiguo , Halloran John W. 
Published: April 2011

AbstractDirect ceramic stereolithography (SLA) is done using UV-curable suspensions of powders in acrylates in a conventional SLA machine. Hydroxyapatite prototypes for bone tissue scaffolds are built from Image-Based Design files, featuring an interior architecture of void passages. Complex alumina objects are built as digital sculptures. Piezoelectric ceramic actuators from PZT, which are difficult to photocure, are built using indirect stereolithography, where SLAbuilt epoxy molds are used to form a thermal-cured suspension of PZT powders. We report on the thermal-curing behavior of the suspensions, and the fundamentals of part building.
A Review of Robocasting Technology
Authors: Cesarano Joseph 
Published: April 2011

AbstractRobocasting is a freeform fabrication technique for dense ceramics and composites that is based on layer-wise deposition of highly loaded colloidal slurries. The process is essentially binderless with less than 1% organics and parts can be fabricated, dried, and completely sintered in less than 24 hours. This review will highlight materials developments for structural applications and modelling of slurry flow. Fabrication of preforms for alumina / metal composites will be discussed as well as techniques for multimaterial deposition in both graded structures and discrete placement of fugitive materials.
New Process and Materials Developments in 3-Dimensional Printing, 3DP™
Authors: Uhland S. A. , Holman R. K. , Cima M. J. , Sachs E. , Enokido Y. 
Published: April 2011

AbstractThe Three-Dimensional Printing (3DP™) process has been modified to incorporate colloidal science for the fabrication of fine ceramic parts. Complex shaped alumina and silicon nitride components have been formed directly from 3-dimensional CAD files using submicron powders. Parts were built using a sequential layering process of the ceramic slurry followed by ink jet printing of a binder system. A well dispersed slurry and optimized printing parameters are required to form a uniform powder bed with a high green density. Liquid-powder bed interactions affect the geometry and internal structure of the component. The redispersion of the unprinted powder bed is critical in order to retrieve the printed components. The slurry and powder bed chemistry are the major factors controlling powder bed redispersion. The process is generic and can be readily adapted for new materials systems. Our research is currently focused on the fabrication of dielectric RF filters. Preliminary results have demonstrated the ability to successfully fabricate cylindrical RF resonators.
Enhanced Infrared Absorptance of Polyethylene Terephthalate via Inorganic Particulate Additives
Authors: Maiorino L. A. , Meyers K. S. , Speyer R. F. 
Published: April 2011

AbstractAmorphous carbon and infrared absorbing glass particulate additives to polyethlene terephthalate increased its infrared absorptance. Significantly lower volume concentrations of carbon were required for a given absorptance increase; however, test bars with glass additive concentrations displaying ˜90% absorptances were largely aesthetically unaltered. Carbon additions to produce the same infrared absorptance resulted in nearly opaque test bars. Heat transfer calculations showed preform heatup time could be reduced from 1 s to 0.6 s with glass particle additions
Cold Spray Direct Fabrication – High Rate, Solid State, Material Consolidation
Authors: Smith M. F. , Brockmann J. E. , Dykhuizen R. C. , Gilmore D. L. , Neiser R. A. , Roemer T. J. 
Published: April 2011

AbstractDirect fabrication of metal near-net shapes from a computer model typically involves melting and solidification, which can cause high residual stresses, undesirable phases, poor microstructures, rough surface finishes, warpage, and other problems. This paper describes a new technology, still under development, that might be used to directly fabricate solid, near-fulldensity, free-form shapes of many metals, and even some composite materials, at or near room temperature without melting and solidification. In this process, tentatively called Cold Spray Direct Fabrication (CSDF), powder particles in a supersonic jet of compressed gas impact a solid surface with sufficient energy to cause plastic deformation and consolidation with the underlying material by a process thought to be analogous to explosive welding. Material deposition by cold spray methods has already been successfully demonstrated by several investigators. This paper presents results of an experimental study to investigate the effects of selected process variables on cold spray particle velocities. In addition, a key technical barrier to the CSDF concept is focusing the spray stream down to dimensions that would permit a useful level of part detail, while still providing practical build rates. This paper presents results of initial research to develop an aerodynamic lens that may provide the required particle stream focusing.
Atomic Displacement Parameters: A Useful Tool in the Search for New Thermoelectric Materials?
Authors: Sales B. C. , Chakoumakos B. C. , Mandrus D. , Sharp J. W. , Dilley N. R. , Maple M. B. 
Published: April 2011

AbstractThe atomic displacement parameters (ADPs) measure the mean-square displacement amplitude of an atom about its equilibrium position in a crystal. It is demonstrated that the ADPs can be used to identify crystalline solids with unusually low lattice thermal conductivties. A low lattice thermal conductivity is essential in the design of thermoelectric materials with improved efficiencies.The atomic displacement parameters (ADPs) have been measured using powder neutron diffraction as a function of temperature for several clathrate-like compounds (RxCo4-yFeySb12, where R= La, Ce, Yb or TI, x=0.22, 0.8, 1, y=0, 1;Tl2SnTe5 and Tl2GeTe5). The ADP data show that in each of the compounds one of the atoms is weakly bound and “rattles” within its atomic cage. This atomic “rattling” severely reduces the ability of these crystals to conduct heat and in some cases the lattice thermal conductivity approaches the theoretical minimum value. In many clathrate-like compounds, the ADP can also be used to estimate the Einstein frequency of the “rattler”, and to predict the existence of localized vibrational modes.
Thermoelectric Properties of Mixed Rhenium Chalcogenides Re6Te15-x Sex (0 ≤ × ≤ 8)
Authors: Dalafave S. Kilibarda , Ziegler J. , Mcallister H. 
Published: April 2011

AbstractReported are the temperature dependencies of the thermoelectric power and electrical resistivity of mixed rhenium chalcogenides Re6Te15-x,Sex (0 ≤ x ≤ 8) in the range 90–420 K. Influence of the partial chalcogen exchange on thermoelectric properties of these compounds is discussed. The samples are prepared by sintering elemental powders inside evacuated and sealed quartz ampoules at 1150 K for 170 hours. X-ray analysis reveals an orthorhombic lattice for samples with x < 8 and a tetragonal lattice for the Re6Te7Se8. sample. The lattice parameters and the unit cell volume decrease with increasing selenium concentration.The measurements indicate p-type semiconducting behavior for all samples. The presence of the energy gap is observed at higher temperatures (T ≥ 180–220 K) for all x. Data suggest hopping conduction at lower temperatures. Room temperature resistivities increase non-linearly from 6.9 to 20.4 Ω m with the increasing selenium content. Initially, the thermoelectric power a increases with temperature for all samples, with the fastest increase in Re6Se8 Te7 and the slowest in Re6Te15. The temperature at which a reaches maximum decreases with the increasing Se content. Above this temperature, a decreases uniformly as the temperature increases, the slowest increase being for Re6Se8Te7 and the fastest for Re6Te15. Such α(T) dependence is also discussed. The temperature dependence of the power factor, α2/ρ, is presented. Comparison of ρ, α, and the power factor in Re6SexTe15-x with currently used state-of-the-art materials is given.
The Nanofabrication of Quantum Wires for the Next Generation of Thermoelectrics
Authors: Demske D. L. , Price J. L. , Guardala N. A. , Lindsey N. , Barkyoumb J. H. , Sharma J. , Kang H. H. , Salamanca-Riba L. 
Published: April 2011

AbstractThe fabrication of a thermoelectric nanocomposite material consisting of nanometer scale bismuth (Bi) wires embedded in a porous mica template host is discussed in detail. In fabricating the mica templates, a positive ion accelerator is employed to irradiate 10 μm thick mica sheets with collimated beams of 15 MeV carbon ions at fluence levels of 1.5 × 1013 ions/cm2. The normally incident beam generates latent nuclear damage tracks in the direction oriented perpendicularly to the mica basal plane. Atomic Force Microscope (AFM) pictures of etched tracks verify that we have fabricated porous templates containing arrays of channels with densities up to 1013/cm2 and diameters as small as 5 nanometers, thus providing pores having an aspect ratio of about 2000:1. Scanning electron micrographs of 50 nm diameter tracks show that these are parallel channels with smooth, non-tapered walls. In addition, to fabricate the wires we have developed a solution-electrodeposition process employing a PC processor-driven potentiostatic/galvanostatic system. Currently, we are electrochemically embedding 10 μm long Bi wires through the nanochannel templates. The potentiostatic electrodeposition behavior of these wires is described. Current-voltage waveforms confirm that the wires are electrically uninterrupted through the mica template. Transmission electron micrographs (TEM) show these wires are single crystals, of well-defined orientation with diameters down to 50 Å. We observe bundles of 80 Å wires with a packing density of about 109/cm2. Energy Dispersive X-ray Spectroscopy (EDS) has corroborated the presence of Bi in the nanochannels. The observation of the bismuth crystal orientation in the porous mica template is examined.
Boundary Effects in Thin-Film Thermoelectrics
Authors: Bartkowiak M. , Mahan G. D. 
Published: April 2011

AbstractEquations describing the resistances to the transport of heat and electricity through boundaries of thin-film thermoelectrics are derived. We show that these boundary resistances obey a boundary form of the Wiedemann-Franz law and cause a new type of thermal instability for short thermoelectric devices. We consider boundary thermal resistances both for phonons (Kapitza resistance) and for electrons, the contact electrical resistance at the junctions, and the boundary thermoelectric effects. It is shown that the Kapitza resistance causes reduction of the effective thermal conductivity of the system only if the electron and phonon subsystems are out of equilibrium. In this case, the thermoelectric figure of merit Z can be increased by reducing the thickness of the film. The electrical contact resistance at the junctions is shown to degrade the performance of the device. However, according to the boundary Wiedemann-Franz law, electrical contact resistance is accompanied by a thermal boundary resistance for the electron subsystem, which can cause an additional enhancement of Z. In some cases, this can lead to a device with ZT as high as 3 at room temperatures.
Preparation and Properties of Porous Bismuth Films
Authors: Shen W. -N. , Dunn B. , Ragot F. , Goorsky M. S. , Moore C. D. , Chen G. , Gronsky R. , Fuller-Mora W. W. , Gillespie D. J. , Ehrlich A. C. 
Published: April 2011

AbstractThe use of chemical solution routes to form inorganic thin films is a relatively new method which represents an alternative to vapor phase routes. The present study involves the use of a chemical solution route, the decomposition of metal carboxylates, to prepare bismuth thin films of controlled porosity. Such morphologies offer the opportunity to disrupt phonon transport without greatly affecting electrical conductivity and bismuth represents a well known system in which to investigate these effects. Porous bismuth thin films have been prepared using bismuth 2-ethylhexanoate (Bi[OOCCH(C2H5)C4H9]3) as the precursor in a solvent of 2-methyl- 1-propanol. The solution is deposited on glass, Kapton, silicon, alumina or magnesia substrates by spin coating and heated to between 250 – 300°C in hydrogen. Heat treatment temperature and time are important for controlling film microstructure as both pore volume (25 to 50%) and preferred orientation depend upon heat treatment conditions. Bismuth films (62 nm thick) with 32% porosity exhibit conductivities in the range of 150 S/cm with Seebeck coefficients comparable to that of bulk materials.
Physical Properties Of Single-Phase Skutterudite Thin-Films (CoSb3 and IrSb3)
Authors: Caylor J. C. , Stacy A. M. , Sands T. , Gronsky R. 
Published: April 2011

AbstractBulk skutterudite phases based on the CoAs3 structure have yielded compositions with a high thermoelectric figure-of-merit (“ZT”) through the use of doping and substitutional alloying. It is postulated that further enhancements in ZT may be attained in artificially structured skutterudites by engineering the microstructure to enhance carrier mobility while suppressing the phonon component of the thermal conductivity. In this work the growth and properties of singlephase CoSb3 and IrSb3 skutterudite thin films are reported. The films are synthesized by pulsed laser deposition (PLD) where the crystallinity can be controlled by the deposition temperature. Powder X-ray diffraction (PXRD), Transmission electron microscopy (TEM) and Rutherford- Back Scattering (RBS) were used to probe phase, structure, morphology and stoichiometry of the films as functions of growth parameters and substrate type. A substrate temperature of 250°C was found to be optimal for the deposition of the skutterudites from stoichiometric targets. Above this temperature the film is depleted of antimony due to its high vapor pressure eventually reaching a composition where the skutterudite structure is no longer stable. However, when films are grown from antimony-rich targets the substrate temperature can be increased to at least 350°C while maintaining the skutterudite phase. In addition, adhesion properties of the films are explored in terms of the growth mode and substrate interaction. Finally, preliminary room temperature electrical and thermal measurements are reported.
Experimental Study of the Effect of the Quantum Well Structures on the Thermoelectric Figure of Merit in Si/Si1-xGex System
Authors: Sun X. , Liu J. , Cronin S. B. , Wang K. L. , Chen G. , Koga T. , Dresselhaus M. S. 
Published: April 2011

AbstractIn bulk form, Si1-xGex is a promising thermoelectric material for high temperature applications. In this paper, we report results from an experimental study as well as theoretical modeling of the quantum confinement effect on the enhancement of the thermoelectric figure of merit. Si/Si1-xGex, multiple quantum well structures are fabricated using molecular beam epitaxy (MBE) on SOI (Silicon-on-Insulator) substrates in order to eliminate substrate effects, especially on the Seebeck coefficient. A method to eliminate the influence of the buffer layer on the thermoelectric characterization is presented. An enhancement of the thermoelectric figure of merit within the quantum well over the bulk value is observed.
Observed Properties and Electronic Structure of RNiSb Compounds (R = Ho, Er, Tm, Yb and Y). Potential Thermoelectric Materials
Authors: Sportouch S. , Larson P. , Bastea M. , Brazist P. , Ireland J. , Kannewurf C. R. , Mahanti S. D. , Uher C. , Kanatzidis M. G. 
Published: April 2011

AbstractThe RNiSb compounds (R=Ho, Er, Tm, Yb and Y) and some selected solid solution members such as (Zr1-xErx)Ni(Sn1-xSbx) and ErNiSb1-xPnx (Pn=As, Sb, Bi) have been studied. They all crystallize in the MgAgAs structure type, which can be considered as a NaCI structure type in which half of the interstitial tetrahedral sites are occupied by Ni atoms. The measured values of the Seebeck coefficients, at room temperature, are positive for RNiSb (R=Ho, Er, Yb and Y) compounds and ErNiSb1-xPnx (Pn=As, Sb, Bi) solid solutions, but for (Zr1-xErx)Ni(Sn1-xSbx) members vary from negative to positive values when 0 < x < 1. Some of these compounds show metallic conductivity while others exhibit thermally activated charge transport. Solid solutions of these materials have lower thermal conductivities than the pure members, RNiSb (R=Ho, Er, Yb and Y) and ZrNiSn. The electronic structures of RNiSb compounds, where R is Y, La, Lu, and Yb, have been studied with density functional theory. The results of the calculations for these systems, except for the Yb compound, indicate narrow gap semiconductors with large effective masses near the conduction band extrema. The Yb system is expected to show heavy fermion characteristics.
Theoretical Calculation of the Vibrational modes in Ge46 Clathrate and Related MxGayGe46-y Type Clathrates
Authors: Dong Jianjun , Sankey Otto F. , Demkov A. A. , Ramachandran Ganesh K. , Gryko Jan , McMillan Paul , Windl Wolfgang 
Published: April 2011

AbstractWe have calculated theoretically the vibrational modes of the type-I Ge46 clathrate and some related Zintl phase structures MxGayGe46-y using ab initio density functional theory. The vibrational modes of pure Ge46 (without guest species) are compared to the MxGayGe46-y structures, and it is found that small metal atoms (e.g. Na) have vanishing restoring force in the large cage, while the larger alkali-earth metal Ba has a restoring force constant less than 10% of that of the a framework atom. This makes them ideal “rattler” systems.
The Effect of A Graded in Profile on the Figure of Merit of PbTe
Authors: Dashevsky Z. , Shusterman S. , Horowitz A. , Dariel M. P. 
Published: April 2011

AbstractThe present study was aimed at demonstrating the possibility of producing a graded charge carrier concentration in a PbTe crystal by taking advantage of the concentration profile that is set up by the diffusion of In from an external source. Doping by indium generates deep impurity levels lying close to the edge of the conduction band. The Fermi level pinning effect and the electron population of the In impurity levels, which reduces the minority carrier concentration at elevated temperature, significantly improve the thermoelectric behavior of the resulting material. The penetration profiles of In, originating from an external gaseous or liquid source, were determined using Seebeck coefficient measurements in p- and n-type PbTe crystals. In the p-type crystal, the Seebeck coefficient changed sign as the In concentration induced a change from p-type to n-type character. The thermovoltage of a PbTe crystal in which an In concentration profile, generated by In diffiusing from a gaseous source had been established, was determined in the 50 to 430 °C temperature range. The constant Seebeck coefficient that was observed over the whole temperature range provides the experimental support for the underlying premises of this study.