235 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Tantalum"  
Results: 1 - 24 next
open access

Nickel-like soft x-ray lasers at 44. 8 Angstrom and 43. 1 Angstrom

Description: Predictions for the gains of the 4p-4d laser lines (0-1, 2-1, 1-1) in Nickel-like Ta and W are compared to the results of experiment. Effects which can resolve the discrepancies are pointed out. 11 refs., 3 figs., 1 tab.
Date: January 1, 1990
Creator: Maxon, S.; MacGowan, B.; Dalhed, S.; Osterheld, A.; London, R. A.; Rosen, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Results of the metallographic examination of the Ta crucible used in the M. S. E. runs

Description: A cross section from a Ta crucible used in numerous Molten Salt Extraction (MSE) runs was submitted to metallography to determine the soundness of the crucible wall, type of Pu attack, depth of wall penetration by the Pu and general microstructure. The crucible contained molten Pu and Am, with CaCl{sub 2}, KCl and PuCl{sub 3} salts ran at temperatures of 750{degree}C to 900{degree}C for approximately 10 to 12 hours. This report documents the findings of this study.
Date: October 22, 1990
Creator: Furr, J.S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

[Synthetic and mechanistic investigation of olefin polymerization catalyzed by early transition metal compounds]

Description: During the second year we continued to prepare and characterize organoyttrium and organoscandium compounds for use as catalysts for polymerizing simple olefins and diolefins. Simple, one-component systems are being pursued, suitable for chain initiation, propagation, and termination studies. This document is divided into: dicarbollide derivatives of scandium as potential catalysts; design, synthesis, and characterization of the first isospecific [alpha] olefin polymerization catalysts; polymeri… more
Date: January 1, 1993
Creator: Bercaw, J.E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Short wavelength nickel-like x-ray laser development

Description: Ni-like x-ray lasers have been produced at wavelengths near to, and below the carbon K edge (43.76-{Angstrom}). Recent work has concentrated on the development of the Ni-like Ta amplifier at 44.83-{Angstrom}. Amplification occurs in a laser produced plasma created by irradiating a thin foil of Ta with two beams of the Nova laser. Up to 8 gainlengths have been demonstrated so far, with a gain coefficient of 3.2 cm{sup {minus}1} and a gain duration of 250 psec. The wavelength of 44.83-{Angstrom} … more
Date: January 7, 1991
Creator: MacGowan, B. J.; Da Silva, L. B.; Fields, D. J.; Fry, A. R.; Keane, C. J.; Koch, J. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High rate sputter deposition of wear resistant tantalum coatings

Description: The refractory nature and high ductility of body centered cubic (bcc) phase tantalum makes it a suitable material for corrosion- and wear-resistant coatings on surfaces which are subjected to high stresses and harsh chemical and erosive environments. Sputter deposition can produce thick tantalum films but is prone to forming the brittle tetragonal beta phase of this material. Efforts aimed at forming thick bcc phase tantalum coatings in both flat plate and cylindrical geometries by high-rate tr… more
Date: November 1, 1991
Creator: Matson, D. W.; Merz, M. D. & McClanahan, E. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Study of radionuclides created by sup 181 Ta(. gamma. ,xn yp) reactions for bremsstrahlung photons produced by 150-MeV electrons

Description: Ten radionuclides, including isomers, from {sup 172}Ta to {sup 180}Ta and {sup 180m}Hf were produced by photon interactions with a sample of elemental tantalum and measured by counting photons using a high-resolution detection system. Relative yields of these radionuclides were obtained. In addition, precision half lives were obtained for {sup 175,176,180}Ta and {sup 180m}Hf. Those obtained for the three Ta isotopes agree with previously reported values. For {sup 180m}Hf, the present measuremen… more
Date: December 1, 1991
Creator: Miller, M.A. (Wisconsin Univ., River Falls, WI (United States)) & Dickens, J.K. (Oak Ridge National Lab., TN (United States))
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Organometallic chemistry of bimetallic compounds

Description: This report consists of six sections: heterobimetallic dihydrides, early-late transition metal heterobimetallic compounds, amphiphilic carbene complexes and hydroxycarbene complexes, diiron compounds with bridging hydrocarbon ligands, diphosphine chelates with natural bite angles near 120 degrees, and synthesis and reactions of M=M compounds. (WET)
Date: July 1, 1991
Creator: Casey, C. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Heat resistant materials and their feasibility issues for a space nuclear transportation system

Description: A number of nuclear propulsion concepts based on solid-core nuclear propulsion are being evaluated for a nuclear propulsion transportation system to support the Space Exploration Initiative (SEI) involving the reestablishment of a manned lunar base and the subsequent exploration of Mars. These systems will require high-temperature materials to meet the operating conditions with appropriate reliability and safety built into these systems through the selection and testing of appropriate materials… more
Date: January 1, 1991
Creator: Olsen, C.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

The Role of Microstructural Phenomena in Magnetic Thin Films

Description: We have pursued two lines of research during the first year and a half of this work. In the main portion of the project we have performed fundamental investigations of the microstructure and crystallographic texture of Co based alloys deposited on Cr underlayers. This has included atomic resolution electron microscopy of the cross-sections of CoNiCr on Cr thin films, as well as studies of the microstructures and properties of magnetic thin films produced with interlayers of Cr. The other portio… more
Date: January 1, 1991
Creator: Laughlin, D. E. & Lambeth, D. N.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Surface structure and analysis with scanning tunneling microscopy and electron tunneling spectroscopy

Description: This report discusses the following topics: charge-density waves in layer structures; charge-density waves in linear chain compounds; spectroscopy with the STM; STM studies of oxides; and development of atomic force microscopy. (LSP).
Date: January 1, 1992
Creator: Coleman, R. V.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Surface structure and spectroscopy of charge-density wave materials using scanning tunneling microscopy

Description: The Scanning tunneling microscope (STM) has been used to study the effects of Fe doping on the charge-density wave (CDW) structure in NbSe{sub 3} and 1T-TaS{sub 2}. In NbSe{sub 3} small amounts of Fe reduce both CDW gaps by 25--30% and change the relative CDW amplitudes of the high and low temperature CDWs. The CDW amplitudes remain strong on all three chains of the surface unit cell with no evident disorder. In 1T-Fe{sub 0.05}Ta{sub 0.95}S{sub 2} the Fe introduces substantial disorder in the C… more
Date: January 1, 1991
Creator: Coleman, R. V.; Dai, Zhenxi; McNairy, W. W.; Slough, C. G. & Wang, Chen
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Experimental investigation of uranium dicarbide densification and the influence of free carbon diffusion

Description: Because UC{sub 2} fuel is being considered for space reactor applications, an investigation of process parameters and densification mechanisms for this fuel was conducted for the DOE. Uranium dicarbide feed powder was prepared by carbothermic reduction of uranium dicarbide and graphite at 2050 K in vacuum. Uranium dicarbide pellets were prepared by cold pressing at 110 MPa and sintering at 2370 K in contact with niobium, tantalum, or tungsten substrates in argon, argon-hydrogen, and vacuum atmo… more
Date: April 1, 1991
Creator: Chidester, K.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Quantum-limited detection of millimeter waves using superconducting tunnel junctions

Description: The quasiparticle tunneling current in a superconductor-insulator- superconductor (SIS) tunnel junction is highly nonlinear. Such a nonlinearity can be used to mix two millimeter wave signals to produce a signal at a much lower intermediate frequency. We have constructed several millimeter and sub-millimeter wave SIS mixers in order to study high frequency response of the quasiparticle tunneling current and the physics of high frequency mixing. We have made the first measurement of the out-of-p… more
Date: September 1, 1991
Creator: Mears, C.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Neutronics analysis for HYLIFE-II

Description: A preliminary neutronics analysis of the HYLIFE-2 reactor concept gives a tritium breeding ratio of 1.17 and a system energy multiplication factor of 1.14. Modified SS-316 (in which Mn is substituted for Ni) is superior to Hastelloy X and Hastelloy N as a firstwall material considering He generation, dpa-limited lifetime, and shallow-burial index. Since Flibe is corrosive to Mn metals, however, a favorable first-wall material is yet to be decided on. Flibe impurities considered (e.g., inherent … more
Date: December 20, 1990
Creator: Tobin, M.T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Quantum limited quasiparticle mixers at 100 GHz

Description: We have made accurate measurements of the noise and gain of superconducting-insulating-superconducting (SIS) mixers employing small area (1{mu}m{sup 2}) Ta/Ta{sub 2}O{sub 5}/Pb{sub 0.9}Bi{sub 0.1} tunnel junctions. We have measured an added mixer noise of 0.61 +/{minus} 0.31 quanta at 95.0 GHz, which is within 25 percent of the quantum limit of 0.5 quanta. We have carried out a detailed comparison between theoretical predictions of the quantum theory of mixing and experimentally measured noise … more
Date: September 1, 1990
Creator: Mears, C.A; Hu, Qing; Richards, P.L. (Lawrence Berkeley Lab., CA (USA)); Worsham, A.H.; Prober, D.E. (Yale Univ., New Haven, CT (USA). Dept. of Applied Physics) & Raeisaenen, A.V. (Helsinki Univ. of Technology, Espoo (Finland). Radio Lab.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Elastic shear modulus: Fits to data and extrapolation to large compressions and negative pressure

Description: An analytic form for the elastic shear modulus is presented and its fit to data at different compressions is demonstrated for copper and tungsten. When only shear modulus at zero pressure and its logarithmic derivative are known, an approximate procedure is used to generate the parameters for an analytic form for the shear modulus. This procedure is demonstrated, and estimates are provided of the shear modulus as a function of compression, for Al, Cu, Fe, Mo, W, Ta, and U. 5 refs., 3 figs., 3 t… more
Date: December 1, 1990
Creator: Straub, G. K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Thermal conductivities of thin, sputtered optical films

Description: The normal component of the thin film thermal conductivity has been measured for the first time for several advanced sputtered optical materials. Included are data for single layers of boron nitride (BN), aluminum nitride (AIN), silicon aluminum nitride (Si-Al-N), silicon aluminum oxynitride (Si-Al-O-N), silicon carbide (SiC), and for dielectric-enhanced metal reflectors of the form Al(SiO{sub 2}/Si{sub 3}N{sub 4}){sup n} and Al(Al{sub 2}O{sub 3}/AIN){sup n}. Sputtered films of more conventiona… more
Date: May 1, 1991
Creator: Henager, C.H. Jr. & Pawlewicz, W.T.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Amplitude modulation of charge-density-wave domains in 1T-TaS sub 2 at 300 K

Description: Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS{sub 2} at room temperature have been made using a scanning tunneling microscope (STM) operating in the constant current mode. The amplitude profiles are in good agreement with the profile predicated by the CDW domain model of Nakanishi and Shiba. Interference effects between the atomic and CDW lattices have been analyzed and do not modify these profiles significantly. They represent the true CDW amplitude variation con… more
Date: January 1, 1991
Creator: Coleman, R. V.; McNairy, W. W. & Slough, C. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

X-ray characterization of oxidized tantalum nitride

Description: Sputter deposited non-stoichiometric tantalum nitride films are oxidized in air between 200 and 500{degrees}C to form a passive film. The oxidized films have been studied with x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption near edge spectroscopy (EXAFS). Films exposed to KOH formed a non-protective surface layer identified in low angle XANES and EXAFS as KTaO{sub 3}. Auger electron and x-ray photoelectron spectroscopies were also used to characterize these films.
Date: January 1, 1991
Creator: MaSaitis, R.L.; Opila, R.L. (AT and T Bell Labs., Murray Hill, NJ (United States)); Ibidunni, A.O. (AT and T Bell Labs., North Andover, MA (United States)); Davenport, A.J. & Isaacs, H.S. (Brookhaven National Lab., Upton, NY (United States))
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Development of an inert ceramic anode to reduce energy consumption in magnesium production

Description: Raw material (titania doped with Ta[sub 2]O[sub 5])selection, development of clip casting as greenware forming method, and sintering studies have been completed. External side and shape of the ceramic portion of the anode has been set. Wall thickness is controlled by slip and casting time. Sintered tubes have been made with wall thicknesses 2.5-5.0 mm; optimum thickness will be determined. Modeling studies show that the conceptual design should survive the applied stresses. Results of strength … more
Date: January 1, 1992
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Time dependent Monte Carlo calculations of the ORELA (Oak Ridge Electron Linear Accelerator) target neutron spectrum

Description: The time dependent spectrum of neutrons in the water-moderated Oak Ridge Electron Linear Accelerator (ORELA) target has been calculated using a modified version of the MORSE multi-group Monte Carlo code with an analytic hydrogen scattering model. Distributions of effective neutron distance traversed in the target are estimated with a time and energy dependent algorithm from the leakage normal to the target face. These data are used in the resonance shaped analyses of time-of-flight cross sectio… more
Date: January 1, 1990
Creator: Cramer, S.N. & Perey, F.G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Micromechanical strength effects in shock compression of solids

Description: Time-resolved shock-wave measurements and post-shock recovery have long been used for inferring the underlaying micromechanics controlling high-rate deformation of solids; this requires considerable subjective interpretation. In spite of this, progress has been made in experimentation and theoretical interpretation of the shock-compression/release cycle and some of the results are reviewed here for weak shocks. This cycle involves the elements of the elastic precursor, plastic loading wave, pul… more
Date: January 1, 1993
Creator: Johnson, J. N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Ternary superconductor NbTiTa'' for high field superfluid magnets

Description: The possibility exists to obtain a higher Hc{sub 2}' upper critical field in the NbTi system which is normally limited by a spin-orbit coupling term. The introduction of scattering reduces this coupling. The spin-orbit scattering rate is proportional to Z{sup 4} and therefore leads logically to the introduction of a high atomic number element which is more or less similar with respect to all of the other properties, i.e., Tc. Previous studies have shown Tantalum to be an excellent choice. The p… more
Date: June 1990
Creator: McInturff, A. D.; Carson, J.; Larbalestier, D.; Lee, P.; McKinnel, J.; Kanithi, H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen