| Dismantling the Deep Earth: Geochemical Constraints from Hotspot Lavas for the Origin and Lengthscales of Mantle Heterogeneity |
FEB 2008 |
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| Authors:
Matthew G. Jackson; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
 | Chapter 1 presents the first published measurements of Sr-isotope variability in olivine-hosted melt inclusions. Melt inclusions in just two Samoan basalt hand samples exhibit most of the total Sr-isotope variability observed in Samoan lavas. Chapter 3 deals with the largest possible scales of mantle heterogeneity, and presents the highest magmatic 3He/4He (33.8 times atmospheric) discovered in Samoa and the southern hemisphere. Along with Samoa, the highest 3He/4He sample from each ... |
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| Species-Specific Sputtering Measurements with Cavity Ring-Down Spectroscopy (Preprint) |
JUL 2007 |
11 pages |
| Authors:
V. K. Surla; L. Tao; A. P. Yalin; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
 | We report sputtering studies using cavity ring-down spectroscopy (CRDS). The high sensitivity of the technique and its non-intrusive nature make it amenable to both in situ device studies as well as basic characterization studies. We provide demonstrative measurements of sputtered particles showing the ability to determine species-specific number density and velocity. We summarize a spatial-scanning approach for differential sputter yield measurements and give a measurement example based on a tantalum ... |
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| Electric-Field Effects in ESR Spectrum of Low-Spin Center Ni3+ in KTaO3 Crystals (Preprint) |
APR 2007 |
7 pages |
| Authors:
L. S. Sochava; S. A. Basun; V. E. Bursian; A. G. Razdobarin; Dean R. Evans; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| Electric-field effects in ESR spectrum of low-spin (S=1/2) tetragonal center Ni3+ was studied in KTaO3 single crystals. Orientation of the centers as well as splitting of the resonance lines was found resulting from the external E-field interaction with the electric dipole moment of the center. The value of the dipole moment was determined to be p=103D=21.4 eAngstrom. An analysis of the experimental results allowed us to make a reasonable choice ... |
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| High Dielectric Constant Oxides for Advanced Micro-Electronic Applications |
29 NOV 2006 |
22 pages |
| Authors:
Roderick A. Devine; NEW MEXICO UNIV ALBUQUERQUE CENTER FOR HIGH TECHNOLOGY MATERIALS
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| A series of mixed oxide compounds have been manufactured and studied with a view to assessing their suitability for applications in advanced microelectronics: ZrO2, Ta2O5, LaAlO3, Sm2O3, Pr2O3, Nd2O3, TiO2, Ti(x)Si(1-x)O2. Although each material has distinct advantages, particularly in terms of the magnitude of the dielectric constant, none of those studied can satisfy all of the requirements for thin films on Si. Consideration of the situation likely to arise under ... |
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| Elastic-Viscoplastic an Isotropic Modeling of Textured Metals and Validation using the Taylor Cylinder Impact Text |
21 NOV 2006 |
23 pages |
| Authors:
B. Plunkett; O. Cazacu; R. A. Lebensohn; F. Barlat; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
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| An elastic-viscoplastic model for describing the anisotropic high-strain rate behavior of both low-symmetry and high symmetry textured materials is proposed. Yielding is described using a recently developed criterion which can capture simultaneously anisotropy and compression-tension asymmetry associated with deformation twinning. The anisotropy coefficients as well as the size of the elastic domain are considered to be functions of the accumulated plastic strain. The specific expressions for the evolution laws are ... |
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| Carcinogenicity and Immunotoxicity of Embedded Depleted Uranium and Heavy-Metal Tungsten Alloy in Rodents |
OCT 2006 |
73 pages |
| Authors:
John F. Kalinich; Alexandra C. Miller; David E. McClain; HENRY M JACKSON FOUNDATION FOR THE ADVANCEMENT OF MILITARY MEDICINE ROCKVILLE MD
|
| This study investigated the carcinogenic and immunotoxic potential of embedded fragments of depleted uranium (DU) and a heavy-metal tungsten alloy (WA) consisting of tungsten, nickel, and cobalt. Male Fisher 344 rats were surgically implanted with pellets of DU, WA, tantalum (inert metal, negative control), or nickel (known carcinogen, positive control). Implanted WA resulted in the rapid formation of tumors, identified as rhabdomyosarcomas, surrounding the pellets. These tumors had, within the ... |
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| Carcinogenicity and Immunotoxicity of Embedded Depleted Uranium and Heavy-Metal Tungsten Alloy in Rodents |
OCT 2006 |
159 pages |
| Authors:
John F. Kalinich; Alexandra C. Miller; David E. McClain; HENRY M JACKSON FOUNDATION FOR THE ADVANCEMENT OF MILITARY MEDICINE ROCKVILLE MD
|
| This study investigated the carcinogenic and immunotoxic potential of embedded fragments of depleted uranium (DU) and a heavy-metal tungsten alloy (WA) consisting of tungsten, nickel, and cobalt. Male Fisher 344 rats were surgically implanted with pellets of DU, WA, tantalum (inert metal, negative control), or nickel (known carcinogen, positive control). Implanted WA resulted in the rapid formation of tumors, identified as rhabdomyosarcomas, surrounding the pellets. These tumors had, within the ... |
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| Elastic-Viscoplastic Anisotropic Modelling of Textured Metals and Validation Using the Taylor Cylinder Impact Test |
JUN 2006 |
41 pages |
| Authors:
B. Plunket; O. Cazacu; F. Barlat; R. A. Lebensohn; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
| An elastic-viscoplastic model for describing the anisotropic high-strain rate behavior of both low-symmetry and high-symmetry textured materials is proposed. Yielding is described using a recently developed criterion which can capture simultaneously anisotropy and compression-tension asymmetry associated with deformation twinning. The anisotropy coefficients as well as the size of the elastic domain are considered to be fimctions of the accumulated plastic strain. The specific expressions for the evolution laws are determined ... |
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| Experimental Evidence for Linear Metal-Azide Bonds. The Binary Group 5 Azides Nb(N3)5, Ta(N3)5, [Nb(N3)6]- and [Ta(N3)6]-, and 1:1 Adducts of Nb(N3)5 and Ta(N3)5 with CH3CN (PREPRINT) |
20 MAR 2006 |
37 pages |
| Authors:
Ralf Haiges; Jerry A. Boatz; Thorsten Schroer; Muhammed Yousufuddin; Karl O. Christe; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| Whereas the existence of numerous binary transition metal azido-complexes has been reported, no binary Group 5 azides are known. Only a limited number of partially azide-substituted compounds of vanadium, niobium and tantalum have previously been reported. In this paper, we wish to communicate the synthesis and characterization of Nb(N3)5, Ta(N3)5 and their 1:1 adducts with CH3CN, and of the anions [Nb(N3)6]- and [Ta(N3)6]-. The crystal structures of Nb(N3)5-CH3CN and [PPh4][Nb(N3)6] ... |
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| Experimental Evidence for Linear Metal-Azide Coordination: The Binary Group 5 Azides [Nb(N3)5], [Ta(N3)5], [Nb(N3)6], and [Ta(N3)6], and 1:1 Acetonitrile Adducts [Nb(N3)5(CH3CN)] and (Ta(N3)5(CH3CN)) |
20 MAR 2006 |
7 pages |
| Authors:
Ralf Haiges; Thorsten Schroer; Muhammed Yousufuddin; Karl Christe; Jerry A. Boatz; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES LOKER HYDROCARBON RESEARCH INST
|
| Whereas the existence of numerous binary transition metal azido-complexes has been reported, no binary Group 5 azides are known. Only a limited number of partially azide-substituted compounds of vanadium, niobium and tantalum have previously been reported. In this paper, we wish to communicate the synthesis and characterization of Nb(N3)5, Ta(N3)5 and their 1:1 adducts with CH3CN, and of the anions [Nb(N3)6]- and [Ta(N3)6]-. The crystal structures of [Nb(N3)5(CH3CN)] and [PPh4][Nb(N3)6] ... |
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| Polyazide Chemistry: Synthesis and Properties of [Nb(N3)7]2- and [Ta(N3)7]2- (PREPRINT) |
16 MAR 2006 |
39 pages |
| Authors:
Ralf Haiges; Jerry A. Boatz; Muhammed Yousufuddin; Karl O. Christe; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| During the last decade, inorganic polyazido compounds have received much attention. Besides being of academic interest, azides and polyazides are viable candidates for high energy-density materials (HEDM). The azido group is very energetic and polyazides are highly endothermic compounds, whose energy content increases with an increasing number of azido ligands. It is, therefore, not surprising that the synthesis of molecules with a high number of azido groups is very challenging ... |
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| Carcinogenicity and Immunotoxicity of Embedded Depleted Uranium and Heavy-Metal Tungsten Alloy in Rodents |
OCT 2005 |
34 pages |
| Authors:
John F. Kalinich; Alexandra C. Miller; David E. McClain; HENRY M JACKSON FOUNDATION FOR THE ADVANCEMENT OF MILITARY MEDICINE ROCKVILLE MD
|
| This study investigates the carcinogenic and immunotoxic potential of embedded fragments of depleted uranium (DU) and a heavy-metal tungsten alloy (WA). Male Fisher 344 rats were surgically implanted with pellets of DU, WA, tantalum (inert metal, negative control), or nickel (known carcinogen, positive control). We previously reported that implanted WA resulted in the rapid formation of tumors, identified as rhabdomyosarcomas, surrounding the pellets. In Year 4 we found that these ... |
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| A Study to Uncover the Microstructural Basis for the Intrinsic Toughness of Interfaces and Its Relation to the Plastic Work That Accompanies Interface |
07 SEP 2005 |
30 pages |
| Authors:
Vijay Gupta; CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| A fundamental relationship between intrinsic and total toughness of tantalum/sapphire, Al/epoxy, and Si/epoxy joints is established using several novel interface characterization tools. The focus of research was to understand issues related to size effects, energy absorption capacity, and reliability, of joints. A double cantilever beam experiment equipped with a cryogenic cell, and a lasergenerated stress wave technique was used to measure the strength and toughness of interfaces, respectively. Although not ... |
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| Experimental Evidence for Linear Metal-Azide Bonds. The Binary Group 5 Azides Nb(N3)5, Ta(N3)5, [Nb(N3)6]- and [Ta(N3)6]-, and 1:1 Adducts of Nb(N3)5 and Ta(N3)5 with CH3CN |
27 APR 2005 |
39 pages |
| Authors:
Ralf Haiges; Jerry A. Boatz; Thorsten Schroer; Muhammed Yousufuddin; Karl O. Christe; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| Whereas numerous binary transition metal azido-complexes have been reported, no binary Group 5 azides are known. Only a limited number of partially azide-substituted compounds of vanadium, niobium and tantalum have previously been reported. In this paper, we wish to communicate the synthesis and characterization of Nb(N3)5, Ta(N3)5 and their 1:1 adducts with CH3CN, and of the anions [Nb(N3)6]- and [Ta(N3)6]-. We also report the crystal structures of Nb(N3)5 CH3CN and ... |
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| Multiple Explosively Formed Penetrator (MEFP) Warhead Technology Development |
DEC 2004 |
3 pages |
| Authors:
Richard Fong; William Ng; LaMar Thompson; Steve Tang; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL NJ
|
| MEFP Warhead technology was initiated in the 1980's to provide a warhead that could produce many highly effective penetrators for the attack of light materiel targets. Previously, EFP warheads were designed to produce a single rod shaped or ball shaped penetrator for deep armor penetration. With the MEFP warhead concepts, the liner was designed and formed to produce many individual penetrators to attack light materiel area targets. Initial MEFP warhead ... |
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| Direction-Selective Free Expansion of Laser-Plasmas from Planar Targets |
07 APR 2004 |
2 pages |
| Authors:
Th. Muller; B. K. Sinha; S. N. Srivastava; K. P. Rohr; KAISERSLAUTERN UNIV (GERMANY F R)
|
| Direction-selective expansion of laser-plasmas from planar, slab targets of Al, Ni, Mo and Ta are reported. Angular distributions of the particles emitted from the targets, produced by a 130mJ-5nsec, NdLYAG laser, were obtained by means of a retarding potential analyzer and a quartz crystal. It was observed that the angular distribution of the particles was preferentially focussed towards the target normal with the increase in the focal spot size, atomic ... |
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| The Dependence of Dielectric Properties on Composition Variation in Ba(0.6)Sr(0.4)(YTa)(y)Ti(1-2y)O(3) |
03 APR 2003 |
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| Authors:
Daniel Potrepka; Steven Tidrow; Arthur Tauber; Kevin Kirchner; Matthew Ervin; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
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| Ba(0.5)Sr(0.4)(YTa)Ti(1-2y)O3 has been shown to have properties which are promising for tunable applications requiring low dielectric constant 1. Ba(0.6)Sr(0.4)(YTa)(y)Ti(1-2y)O3 with y |
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| Bulk Nanostructured Refractory Metals with Enhanced Mechanical Properties Produced by Equal Channel Angular Pressing |
11 DEC 2002 |
6 pages |
| Authors:
R. Z. Valiev; I. V. Alexandrov; UFA STATE AVIATION TECHNICAL UNIV (RUSSIA) INST OF PHYSICS OF ADVANCED MATERIALS
|
| The air of the present project is to obtain a set of bulk billets 100 mm long with UFG structure made of refractory metals such as tungsten and tantalum. The previous positive experience of refining the tungsten's structure using equal channel angular pressing (ECAP) was taken into account. For the production of bulk billets with UFG structure having a more long-lengthed size than those obtained in earlier works, it has ... |
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| Surface Heating of Molybdenum, Tantalum, and Tungsten Rods by Pulsed Currents |
NOV 2002 |
40 pages |
| Authors:
Charles R. Hummer; John D. Powell; Paul R. Berning; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Measurements of the surface voltage and surface temperature are made for small molybdenum, tantalum, and tungsten rods that have been subjected to pulsed electrical heating. The heating time is from 100 to 200 microseconds. The experimental results are then compared to results obtained from calculations undertaken with a numerical model that accounts for diffusion of current and ohmic heating within the sample. Good agreement between theory and experiment is obtained ... |
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| Carcinogenicity and Immnotoxicity of Embedded Depleted Uranium and Heavy-Metal Tungsten Alloy in Rodents |
OCT 2002 |
17 pages |
| Authors:
Alexandra C. Miller; John F. Kalinich; David E. McClain; HENRY M JACKSON FOUNDATION FOR THE ADVANCEMENT OF MILITARY MEDICINE ROCKVILLEMD
|
| This study investigates the carcinogenic and immunotoxic potential of embedded fragments of depleted uranium (DU) and a heavy-metal tungsten alloy (HMTA) to determine if carcinogenicity and immunotoxicity are correlated with tissue-metal content. We hypothesize that long-term chronic exposure to embedded DU and HMTA initiates changes in normal immune function that will eventually result in a carcinogenic response characterized by both tumor formation at the fragment implantation site (solid-state or foreign-body ... |
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| Inhalation of Uranium Oxide Aerosols: CNS Deposition, Neurotoxicity, and Role in Gulf War Illness |
OCT 2002 |
23 pages |
| Authors:
Johnnye L. Lewis; Graham Bench; Fletcher F. Hahn; NEW MEXICO UNIV ALBUQUERQUE ERIC H WANG CIVIL ENGINEERING RESEARCH FACILITY
|
| This project is investigating the potential for inhaled uranium oxide aerosols to penetrate the nose-brain barrier, directly enter the central nervous system (CNS), diffusely distribute within the CNS, and result in slowly developing neurotoxic responses. The first year of the project has focused on generating aerosols representative of exposure concentrations and particle sizes that reflect exposure atmospheres potentially encountered in very short-term exposures likely in the Gulf War. The research ... |
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| An Algorithm for the Determination of Coating Properties from Laser- Generated and Detected Rayleigh Waves Using Wavelet Analysis: Application to Sputtered Tantalum |
JUL 2002 |
16 pages |
| Authors:
M. A. Doxbeck; M. a. Hussain; J. Rama; A. Abbate; J. Frankel; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| We used single-source and single-detector laser-ultrasonic measurements to generate and detect Rayleigh waves on tantalum sputtered steel substrates. Group velocity dispersion curves were calculated from the single- detected signals using wavelet techniques. Theoretical dispersion curves were calculated via the Achenbach and Keshava analysis. A simplex minimization technique between theory and experiment, using known values for the substrate, allowed us to evaluate the coating parameters. The coating thickness was measured accurately ... |
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| Coating-Bond Evaluation Using Dispersion Curves and Laser-Ultrasonics |
DEC 2001 |
31 pages |
| Authors:
Agostino Abbate; Bryon Knight; Moayyed A. Hussain; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| The dispersion characteristics of Rayleigh surface waves are used to distinguish the quality of the bond between a coating and the metallic substrate. The velocity versus frequency curves for good or 'welded' bonds differ significantly from the correspondent dispersion curves for poorer or 'smooth' bonds. A theoretical dynamic model of the ultrasonic experiments was developed and compared with experimental results. As examples of welded contacts, we used coatings of tantalum ... |
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| Origins of Beta Tantalum in Sputtered Coatings |
NOV 2001 |
15 pages |
| Authors:
C. P. Mulligan; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| The source of beta tantalum formation in sputtered coatings has been a subject of controversy going back over thirty years. For every research paper in which the cause is seemingly identified, there are others, which seem to disprove it. It has been very difficult to find a unifying theory that explains the contradictory results found in these papers. The purpose of this report is to compile the vast amount of ... |
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| Properties of Thick Sputtered Tantalum Used for Protective Gun Tube Coatings |
OCT 2001 |
22 pages |
| Authors:
Dean W. Matson; Edwin D. McClanahan; Sabrina L. Lee; Donald Windover; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET WEAPONS LAB
|
| Thick tantalum coatings were deposited on the bore surfaces of 25-mm inner diameter cylindrical gun steel substrates using a high-rate triode- sputtering apparatus. Sputtering parameters affecting the tantalum phase and microstructure were investigated. Prior work has indicated that the sputtering gas species and substrate temperature during deposition affect the characteristics of the tantalum coatings. In the work presented here, we report on experimental studies aimed at evaluating additional phase and ... |
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| Deposition and Characterization of Barrier Metals |
SEP 2001 |
34 pages |
| Authors:
Kevin D. Leedy; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIRECTORATE
|
| Increasing complexity and shrinking sizes of integrated circuits necessitate the development of new materials and processes to meet current system requirements of high performance and reliability in smaller electronic assemblies. In order to achieve the system performance, materials with incompatible physical and electrical properties are often placed into direct contact with one another. Applications such as area array interconnection of Si devices using lead/tin solders, vias in Si integrated circuits ... |
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| Fabrication of High-Performance Coatings Systems via a Novel In-Situ/Ex- Situ Characterization Technique |
31 JUL 2001 |
21 pages |
| Authors:
John C. Bilello; MICHIGAN UNIV ANN ARBOR DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| This report will briefly outline some of the key findings made during the course of this project and some new work on the phase structure changes concomitant with the delamination behavior of Ta metallizations. Detailed accountants of prior work have been in included in previous "Interim Reports" of this Grant and in the many technical papers that have resulted from the support of this work. A complete list of these ... |
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| Plastic Flow and Shear Banding in Refractory Metals and Martensitic Steels at Very High Shearing Rates |
26 JUN 2001 |
10 pages |
| Authors:
Rodney J. Clifton; BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING
|
| Research is reported on the dynamic shearing response of three metals: OFHC copper, tantalum, and 4340 VAR steel. For OFHC copper the important new result is that the flow stress has been measured at strain rates up to 1, 000,000/sec at temperatures up to 700 deg C. At the elevated temperatures the dynamic plastic response is remarkably stable and the flow stress is considerably higher than predicted by commonly used ... |
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| Multilevel Magnetoresistance in a Structure Consisting of Two Spin-Valves |
APR 2001 |
|
| Authors:
Kebin Li; Yihong Wu; Jinjun Qiu; Guchang Han; Zaibing Guo; NATIONAL UNIV OF SINGAPORE DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| The magnetic and electrical properties as well as the structural characteristics have been studied on a series of samples with structure substrate (Sub)/SV(1)/Al2O35nm/SV(2). Here SV(1) is either CoFe/IrMn based spin-valve (SV) such as Ta5/NiFe2/IrMn8/CoFe2/Cu2.6/CoFe2/Ta5 (thicknesses are in nanometers) bottom SV or Ta5/NiFe2/CoFe1.5/Cu2.6/CoFe2/FeMn10/Ta5 top SV and SV(2) is Ta5/NiFe2/CoFe1.5(or 2)/Cu2.6/CoFe2/IrMn8/Ta5 top SV - SV(1) and SV(2) in the structure are decoupled by a Al2O3 layer with 5 nm in the magnetic ... |
|
| Improvement of Crystallographic Characteristics of CoCrTa Thin Film Using Double Underlayer |
APR 2001 |
|
| Authors:
Y. J. Kim; S. H. Kong; S. Nakagawa; M. Naoe; K. H. Kim; TOYKO INST OF TECH (JAPAN) DEPT OF PHYSICAL ELECTRONICS
|
| High c-axis oriented CoCr-based thin films are expected for ultra-high density recording media in perpendicular magnetic recording system. In order to improve dispersion angle of c-axis of CoCr-based for perpendicular magnetic recording media, we prepared trilayered film with double underlayer using New Facing Targets Sputtering apparatus. The thickness of magnetic layer CoCrTa and double underlayer, such as interlayer Pt, paramagnetic CoCr, underlayer Ti was fixed 50 nm and 20 nm ... |
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| Laser Pulse Heating Simulation of Firing Damage on Coated Gun Bore Surfaces |
MAR 2001 |
19 pages |
| Authors:
P. J. Cote; G. Kendall; M. Todaro; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY CLOSE COMBAT ARMAMENTS CENTER
|
| Laser pulse heating was used to simulate thermal effects on plated gun bore surfaces during firing. The aim is to provide new insights into the erosion process and develop the method as an evaluation tool for developmental coatings. This report discusses results of cyclic thermal pulsing experiments on high contractile and low contractile chromium plated gun steel, sputtered tantalum coated gun steel, and uncoated steel. |
|
| Characterization of Tantalum Liners Applied to 25-mm and 120-mm Cannon Bore Sections via Explosive Bonding |
FEB 2001 |
23 pages |
| Authors:
G. Vigilante; T. Sage; G. Kendall; P. Cote; S. Lee; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET WEAPONS LAB
|
| A materials forensics analysis was performed on sections of 25-mm rifled and 120-mm smoothbore gun tubes that were explosively bonded with pure tantalum. Characterization tests included liner thickness measurements, profilometry/surface finish, x-ray diffraction, and microstructural analysis including microhardness, scanning electron microscopy, energy dispersive spectroscopy, and adhesion testing. Results indicate that there was good adhesion. However, there was evidence that the explosive bonding process was overly energetic; both adiabatic shear bands ... |
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| Large Deformation Plasticity of Polycrystalline Tantalum |
21 DEC 2000 |
6 pages |
| Authors:
Lallit Anand; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
|
| A physical, crystal mechanics-based theory of thermo-elasto- viscoplasticity which is valid for large strains and high strain rates at low homologous temperatures has been formulated. The theory is able to predict the macroscopic anisotropic stress-strain response, the evolution of crystallographic texture, and the macroscopic shape changes for b.c.c. tantalum. The material functions and parameters in the model were determined by calibrating the model against existing experimental results for tantalum. The ... |
|
| Materials Research Society Symposium Proceedings Volume 653. Multiscale Modeling of Materials - 2000. Symposium Held in Boston, Massachusetts on November 27-December 1, 2000 |
01 DEC 2000 |
259 pages |
| Authors:
Ladislas P. Kubin; Robin L. Selinger; John L. Bassani; Cho Kyeongjae; MATERIALS RESEARCH SOCIETY WARRENDALE PA
|
| Multiscale simulation and modeling of materials phenomena have received much attention in many engineering and scientific disciplines including mechanics physics and materials sciences, with far reaching applications to electronic materials, polymers and biochemical systems. With rapid advances in computing power and multiscale simulation techniques, the hope of modeling material behavior beginning with atomistic simulation and reaching macroscopic phenomena is becoming a realistic goal. This volume contains papers presented at Symposium ... |
|
| Study of Productivity of Tantalum Spallation by Protons for Accumulation of the 178m2Hf Isomeric Nuclei |
25 OCT 2000 |
16 pages |
| Authors:
Ioan-Lovitz Popescu; ROMANIAN CENTER FOR INDUCED GAMMA EMISSION BUCHAREST (ROMANIA)
|
| This report results from a contract tasking Romanian Center for Induced Gamma Emission as follows: The contractor will establish the exact position of the gateway state(s) above the 31 year lifetime, high-K isomeric state in the 178Hf nucleus. |
|
| Carcinogenesis of Depleted Uranium Fragments |
JUN 2000 |
|
| Authors:
Fletcher F. Hahn; DEPARTMENT OF ENERGY ALBUQUERQUE NM ALBUQUERQUE OPERATIONS OFFICE
|
| This study determined the carcinogenicity of depleted uranium DU(Ti) fragments in muscles of rats. Implants of DU(Ti) were compared to implants of tantalum (Ta), as a foreign-body control, and to injections of radioactive Thorotrast(R), a colloid of thorium dioxide, as a radioactive control. The test metals, in four squares (2.5 x 2.5 x 1.5 mm or 5.0 x 5.0 x 1.5 mm) or pellets (2.0 x 1.0 mm diam.) were ... |
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| Experimental Study of Metal Corrosion in Supercritical Brines: Application to Supercritical Water Oxidation of Hazardous Wastes |
31 MAR 2000 |
65 pages |
| Authors:
Scott A. Wood; Leslie L. Baker; IDAHO UNIV MOSCOW DEPT OF GEOLOGY ANDGEOLOGICAL ENGINEERING
|
| The corrosion behavior of Hastelloy C, ticanium, zirconium, niobium, tantalum, and gold have been studied as a function of temperature (200 degrees - 4000 degrees C), acid concentration (0 0.02 mol/Kg), oxygen content (0.1-1 mol %) and NaCi content (0-0.2 mol/Kg). The intent of these experiments was to determine an empirical rate law for corrosion of these metals as a function of the parameters listed above. ... |
|
| Coating Evaluation Using Analytical and Experimental Dispersion Curves |
NOV 1999 |
16 pages |
| Authors:
B. Knight; M. Hussain; J. Frankel; J. F. Cox; J. Braunstein; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET WEAPONS LAB
|
| Well-bonded or "welded" contact and poorly bonded or "smooth" contact bonds were studied. As examples of welded contact bonds, we used sputtered tantalum and electrodeposited high contraction chromium coatings that were deposited onto steel substrates under controlled conditions. In order to simulate smooth contact coatings, thin sheets of nickel and tantalum were epoxied to copper and steel substrates, respectively. We used the method originated by ... |
|
| Analysis of Molten Salt and Sputter-Deposited Coatings on Steel Cylinders |
OCT 1999 |
28 pages |
| Authors:
S. L. Lee; M. Cipollo; D. Windover; C. Rickard; WATERVLIET ARSENAL NY BENET WEAPONS LAB
|
| Prototype tantalum coatings, electrochemically deposited from a molten salt onto 20-mm interior bore steel liners, exhibited superior wear and erosion behavior compared to chromium coatings. The liners were subjected to cyclic exposures of high temperature, pressure, and an aggressive chemical environment. X-ray analysis of the coatings revealed a low-hardness, randomly- oriented, body-centered-cubic, alpha-phase tantalum. Formation of tantalum oxides (predominantly Ta2O5), swaging due to the low-hardness of the coatings, a 2-micrometers ... |
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| Thin-Film Density Determination of Tantalum, Tantalum Oxides, and Xerogels by Multiple Radiation Energy Dispersive X-Ray Reflectivity |
MAY 1999 |
19 pages |
| Authors:
D. Windover; S. L. Lee; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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| X-ray reflectivity provides a nondestructive technique for measuring density in thin films. A conventional laboratory, Bragg-Brentano geometry diffractometer was employed to show the generalized feasibility of this technique. X-ray tubes with chromium, copper, and molybdenum targets were used to provide a large overlap of energies for density fitting. X-ray tube alignmentand sample alignment were explored to find a self-consistent measurement technique. The real and complex indices for tantalum, TaOx, and ... |
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| Evaluation of Electrical Resistivity Characteristics of Metalized 4H-SiC for Application to Electric Guns |
APR 1999 |
30 pages |
| Authors:
Gary L. Katulka; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The experiments described demonstrate the electrical behavior of SiC and metal ohmic-contact layers as a function of thermal stress. It has been determined from these experiments that both titanium (Ti) and tantalum (Ta) metalization structures will provide a stable electrical ohmic-contact with n- type SiC after exposure to elevated temperatures for short bursts of time that are considered relevant for pulsed-powered electric weapon technologies. The Ti- SiC structure investigated exhibited ... |
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| Investigation of K-Mixing in Nuclei with Isomeric States |
1999 |
11 pages |
| Authors:
Ioan-Iovitz Popescu; ROMANIAN CENTER FOR INDUCED GAMMA EMISSION BUCHAREST (ROMANIA)
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| This report results from a contract tasking Romanian Center for Induced Gamma Emission as follows: The contractor will (a) travel to Orsay, France to participate in the data collection; (b) reduce some of the data at RC- IGE in Bucharest; (c) review the data and decide analytical strategies; and (d) review results and develop a sequent publications summarizing the results. |
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| Environmental Effects of Tungsten and Tantalum Alloys |
OCT 1998 |
288 pages |
| Authors:
Arend Meijer; Gregory Wroblicky; Sarah Thuring; Michael W. Marcell; GCX ALBUQUERQUE NM
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| Report developed under SBIR contract (covers Phase I and Phase II studies). The purpose of this study was to evaluate the potential environmental impacts of the testing of tungsten alloy and tantalum penetrator munitions at Test Site C-64 A on Eglin AFB, FL. The tungsten alloys that were investigated in this study contained iron, nickel, cobalt, copper, and/or manganese as alloying elements. Data on physical, chemical, ... |
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| Electrode Conditions and Their Effect on Impedance Collapse |
02 JUL 1998 |
39 pages |
| Authors:
N. R. Pereira; BERKELEY RESEARCH ASSOCIATES INC CA
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| Changes in electrode conditions affect impedance collapse, seen in our 300 kV diode as a rapid increase in current beyond the 1 kA space charge limit. Impedance collapse comes about 100 ns later than the usual 200 ns when the diode's tantalum anode is hot (600 - 1000 K). Covering the carbon fiber ring cathode with cesium iodide delays collapse by another 100 ns. These observations might ... |
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| Phase, Residual Stress, and Texture in Triode-Sputtered Tantalum Coatings on Steel |
JUL 1998 |
23 pages |
| Authors:
S. L. Lee; D. Windover; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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| This work analyzes the unoptimized prototype triode-sputtered. 150 microns thick tantalum coatings deposited with a 2.5 microns niobium under-layer the bore of a large-diameter A723 steel cylinder. The coating was deposited for wear and erosion protection by Pacific Northwest National Laboratory. Our phase determination was based on X ray diffraction analysis, wavelength dispersive X ray fluorescence analysis, energy dispersive X ray analysis, and hardness and ... |
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| Dynamic Behavior of Ductile Materials |
31 DEC 1997 |
33 pages |
| Authors:
S. N. Nemat-Nasser; Marc Meyers; Ken Vecchio; CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF APPLIED MECHANICS AND ENGINEERINGSCIENCES
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| A comprehensive and multidisciplinary research program centered on the fundamental study of the dynamic response and failure modes of a broad class of conventional and advanced ductile materials. This research program is founded on four important areas: a) the unique and novel experimental facilities for dynamic testing established at UCSD; b)a balanced multidisciplinary program with investigators of combined expertise and prominence in the fields of materials, mechanics and computational and ... |
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| Inhibition of Microbiologically Influenced Corrosion |
NOV 97 |
14 pages |
| Authors:
P. M. Natishan; J. Jones-Meehan; G. I. Loeb; N. Gray; B. J. Little; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Two areas of work designed to provide a better understanding on the nature of microbial colonization of surfaces and microbiologically influenced corrosion are discussed. The first approach examined a mechanical sensing model to describe microbial colonization. Results obtained alter the exposure of a group polydimethylsiloxane polymers to an estuary environment provide support for this model. The second approach sought to determine it there is a relationship between microbial colonization' of ... |
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| Single Pulse Emittance Measurement Technique for Intense Relativistic Electron Beam |
16 MAY 1997 |
28 pages |
| Authors:
J. A. Gregor; R. M. Meger; J. A. Antoniades; NAVAL RESEARCH LAB WASHINGTON DC
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| A study of emittance measurements using a slit pinhole type emittance meter is conducted using a 1 MeV, 18 ka electron beam. The beam is passed through titanium foils of varying thickness and the emittance is measured downstream. Two different types of emittance masks are used - one composed of tantalum bars with knife edges and another using cylindrical bars of elkonite. The prototype is used to measure the rms ... |
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| Porous Metal/Organic Polymeric Composites. |
28 APR 1997 |
40 pages |
| Authors:
M. A. Imam; Satya B. Sastri; Tedyy M. Keller; DEPARTMENT OF THE NAVY WASHINGTON DC
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| Metal foams are impregnated with resins. The metal foam/polymer composite formed upon curing has excellent acoustic dampening and structural properties. Foams of various metals, such as aluminum, titanium, nickel, copper, iron, zinc, lead, silver, gold, platinum, tantalum, and alloys based on these metals, may be used. The polymer component may be any polymeric resin, for example, epoxy, natural rubber, acrylic, or phenolic. |
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| Resistivity of Fe.49 Co.49Ta.01 High Strength Laminates from -73C to + 650 C |
07 APR 97 |
10 pages |
| Authors:
Gerard K. Simon; Ronald E. Perrin; Melvin C. Obmer; Timothy L. Peterson; Charles E. Culp; WRIGHT LAB WRIGHT-PATTERSON AFB OH
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| Telcon HS 50 Alloy is a recently developed iron-cobalt soft magnetic alloy (50.41% Fe, 48.75% Co, 0.45% Ta, 0.27% V, 0.08% Si, 0.04% Mn) intended for commercial applications requiring high strength. Its physical, electrical and magnetic properties have not yet been reported over the operating temperatures of interest. This report addresses the resistivity testing of this alloy in . 006' thick strip product form (dry hydrogen annealed) and the subsequent ... |
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Reports by Keyword(s)
TANTALUM
