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Life Tests of Tungsten and Tantalum Filaments in Ion Gauges

Description: Results of an investigation carried on for the following purposes: (1) To determine the relative life of filaments when operated at low emission (low temperatures) as compared to those operated at high emission values. (2) To determine the nature of the dependence of life upon the initial diameter of the filament. (3) To determine the effect of varying concentrations of water vapor and air upon the life of the filaments. (4) To determine the relative life characteristics of tantalum as compared to tungsten.
Date: August 9, 1949
Creator: Bush, W. E.
Partner: UNT Libraries Government Documents Department

World Survey of Tantalum Ore

Description: Report issued by the U.S. Bureau of Mines discussing the occurrences of tantalum in different areas of the world. The tantalum deposits are described in reference to each individual country that it is found in. This report includes maps, tables, and illustrations.
Date: March 1945
Creator: Baker, James S.
Partner: UNT Libraries Government Documents Department

Investigation of Tantalum in a 3,800 Degrees Fahrenheit Supersonic Airstream

Description: "An investigation of tantalum was made in still air and in high-velocity air to determine its resistance to oxidation at high temperatures. Experiments show that, except for a narrow range of temperature, unprotected tantalum is not suitable for airframe parts exposed to air at high stagnation temperatures, because above this temperature range tantalum oxidizes or burns rapidly" (p. 1).
Date: January 9, 1958
Creator: Trout, Otto F., Jr. & Modisette, Jerry L.
Partner: UNT Libraries Government Documents Department

Isotopic Examination of Tantalum

Description: Introduction: "The ionization region in the Nier mass spectrometer is customarily constructed of copper. Various other metals were tried for this purpose; among them tantalum and molybdenum, with both metals it was found that a spectrum of the fluoride of the metal appeared when uranium hexafluoride was admitted. It was thus possible to produce tantalum fluoride with comparative ease and to make a critical examination of the mass spectrum to set an upper limit of abundance of tantalum isotopes. For positive identification, a line must appear in all ion positions in the same abundance, relative to the main line. It must be shown that any lines which appear are not contributed by other elements or compounds."
Date: January 18, 1946
Creator: Cameron, Alan E. & White, J. R.
Partner: UNT Libraries Government Documents Department

Vapor deposition of tantalum and tantalum compounds

Description: Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition.
Date: April 1996
Creator: Trkula, M.
Partner: UNT Libraries Government Documents Department

Passivation effects of surface iodine layer on tantalum for the electroless copper deposition.

Description: The ability to passivate metallic surfaces under non-UHV conditions is not only of fundamental interests, but also of growing practical importance in catalysis and microelectronics. In this work, the passivation effect of a surface iodine layer on air-exposed Ta for the copper electroless deposition was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Although the passivation effect was seriously weakened by the prolonged air exposure, iodine passivates the Ta substrate under brief air exposure conditions so that enhanced copper wetting and adhesion are observed on I-passivated Ta relative to the untreated surface.
Access: This item is restricted to the UNT Community Members at a UNT Libraries Location.
Date: May 2004
Creator: Liu, Jian
Partner: UNT Libraries

Separation of Tuballoy From Tantalum by Chlorination Distillation Process

Description: Abstract: Tuballoy can be effectively separated from tantalum filaments by chlorination of the filaments and subsequent distillation and condensation of tantalum chloride. Apparatus for chlorination of filaments and distillation separation in one unit is under consideration. Chemical methods of separation of tuballoy from distillation residues are being tested.
Date: February 6, 1946
Creator: Adams, R. H.; Rogers, J. A.; Wagner, E. L. & Miller, A. J.
Partner: UNT Libraries Government Documents Department

Trace Elements Investigations : The Occurrence of Columbium and Tantalum

Description: The following report is the fourth in a series of reports on rare and uncommon elements prepared by the Geological Survey. This report covers columbius and tantalus, two chemical elements belonging to the fifth group of the periodic table and quinquevalent in most of their compounds.
Date: August 8, 1983
Creator: Fleischer, Michael & Harder, James O.
Partner: UNT Libraries Government Documents Department

LASNEX modeling of target expansion in the ETA-II experiment

Description: We have used the hydrodynamics code LASNEX to model the hydro-expansion of the tantalum target for the ETA-II experiment. The electron beam has kinetic energy of 6 MeV and has a total energy ranges from 720 to 1440 J. The electron beam profile resembles that of a Bennett pinch. The radius for the full-width-at-half-maximum ranges from 1 to 3 mm. For all these parameters, simulations show that the electron beam is able to ablate the central portion of the target. The expansion velocity of the target ranges from about 10� to 5 x 105 cm/s. The target is hot enough so that the surrounding low-density air is ionized and is expanding at a considerably higher velocity than the target itself. Therefore, care must be taken during the experiment to ensure that the measurement is for the tantalum and not for the ionized air.
Date: May 20, 1998
Creator: Ho, D D-M
Partner: UNT Libraries Government Documents Department

Micromechanics of spall and damage in tantalum

Description: The authors conducted a series of plate impact experiments using an 80-mm launcher to study dynamic void initiation, linkup, and spall in tantalum. The tests ranged in peak shock pressures so that the effect of peak pressure on the transition from void initiation, incipient spall, and full spall could be studied. Wave profiles were measured using a velocity interferometry system (VISAR), and targets were recovered using {open_quotes}soft{close_quotes} recovery techniques. The authors utilized scanning electron microscopy, metallographic cross-sections, and plateau etching techniques to obtain quantitative information concerning damage evolution in tantalum under spall conditions. The data (wave profiles and micrographs) are analyzed in terms of a new theory and model of dynamic damage cluster growth.
Date: May 1, 1996
Creator: Zurek, A.K.; Thissell, W.R.; Johnson, J.N.; Tonks, D.L. & Hixson, R.
Partner: UNT Libraries Government Documents Department

Evidence for Strong Tantalum-to-Boron Dative Interactions in (silox)3Ta(BH3) and (silox)3Ta(ɳ2-B,CI-BCI2Ph) (silox = tBu3SiO)1

Description: This article discusses strong tantalum-to-boron dative interactions in (silox)3Ta(BH3) and (silox)3Ta(ɳ2-B,CI-BCI2Ph) (silox = tBu3SiO)1.
Date: January 24, 2007
Creator: Bonanno, Jeffrey B.; Henry, Thomas P.; Wolczanski, Peter T.; Pierpont, Aaron W. & Cundari, Thomas R., 1964-
Partner: UNT College of Arts and Sciences

Influence of shockwave obliquity on deformation twin formation in Ta

Description: Energetic loading subjects a material to a 'Taylor wave' (triangular wave) loading profile that experiences an evolving balance of hydrostatic (spherical) and deviatoric stresses. While much has been learned over the past five decades concerning the propensity of deformation twinning in samples shockloaded using 'square-topped' profiles as a function of peak stress, achieved most commonly via flyer plate loading, less is known concerning twinning propensity during non-I-dimensional sweeping detonation wave loading. Systematic small-scale energetically-driven shock loading experiments were conducted on Ta samples shock loaded with PEFN that was edge detonated. Deformation twinning was quantified in post-mortem samples as a function of detonation geometry and radial position. In the edge detonated loading geometry examined in this paper, the average volume fraction of deformation twins was observed to drastically increase with increasing shock obliquity. The results of this study are discussed in light of the formation mechanisms of deformation twins, previous literature studies of twinning in shocked materials, and modeling of the effects of shock obliquity on the evolution of the stress tensor during shock loading.
Date: January 1, 2009
Creator: Gray Iii, George T; Livescu, V; Cerreta, E K; Mason, T A; Maudlin, P J & Bingert, J F
Partner: UNT Libraries Government Documents Department

Tantalum-Rich Alloys of Tuballoy

Description: Report discussing "methods for the manufacture of refractory crucibles for use in high temperature work in general." Additionally, "preliminary experiments with the induction furnace to test the action of tantalum on tantalum carbide at 2900°C are described."
Date: January 15, 1946
Creator: Sausville, J. W. & Larson, C. E.
Partner: UNT Libraries Government Documents Department

Separation of Tuballoy From Metallic Tantalum

Description: Report discussing a method of removing tuballoy (uranium) from metallic tantalum, which involves a double precipitation of tuballoy tetrafluoride obtained by reduction with stannous chloride.
Date: December 28, 1944
Creator: Wagner, E. L.; Gilpatrick, L. O. & Raeuchle, R. F.
Partner: UNT Libraries Government Documents Department

Corrosion Tests on Tantalum, Hastelloy C and Duriron in 234-5 Project Solutions

Description: Introduction: "Room temperature and elevated temperature, static immersion and vapor suspicion, corrosion tests were conducted with Duriron, Hastelloy C, and tantalum in hydriotic acid and 234-5 project process supernatant solution (synthetic environments. The data relevant to these tests are contained herein."
Date: February 25, 1949
Creator: Work, J. B. & Koenig, W. W.
Partner: UNT Libraries Government Documents Department

Tantalum- and ruthenium-based diffusion barriers/adhesion promoters for copper/silicon dioxide and copper/low κ integration.

Description: The TaSiO6 films, ~8Å thick, were formed by sputter deposition of Ta onto ultrathin SiO2 substrates at 300 K, followed by annealing to 600 K in 2 torr O2. X-ray photoelectron spectroscopy (XPS) measurements of the films yielded a Si(2p) binding energy at 102.1 eV and Ta(4f7/2) binding energy at 26.2 eV, indicative of Ta silicate formation. O(1s) spectra indicate that the film is substantially hydroxylated. Annealing the film to > 900 K in UHV resulted in silicate decomposition to SiO2 and Ta2O5. The Ta silicate film is stable in air at 300K. XPS data show that sputter-deposited Cu (300 K) displays conformal growth on Ta silicate surface (TaSiO6) but 3-D growth on the annealed and decomposed silicate surface. Initial Cu/silicate interaction involves Cu charge donation to Ta surface sites, with Cu(I) formation and Ta reduction. The results are similar to those previously reported for air-exposed TaSiN, and indicate that Si-modified Ta barriers should maintain Cu wettability under oxidizing conditions for Cu interconnect applications. XPS has been used to study the reaction of tert-butylimino tris(diethylamino) tantalum (TBTDET) with atomic hydrogen on SiO2 and organosilicate glass (OSG) substrates. The results on both substrates indicate that at 300K, TBTDET partially dissociates, forming Ta-O bonds with some precursor still attached. Subsequent bombardment with atomic hydrogen at 500K results in stoichiometric TaN formation, with a Ta(4f7/2) feature at binding energy 23.2 eV and N(1s) at 396.6 eV, leading to a TaN phase bonded to the substrate by Ta-O interactions. Subsequent depositions of the precursor on the reacted layer on SiO2 and OSG, followed by atomic hydrogen bombardment, result in increased TaN formation. These results indicate that TBTDET and atomic hydrogen may form the basis for a low temperature atomic layer deposition (ALD) process for the formation of ultraconformal TaNx or Ru/TaNx barriers. The interactions ...
Date: December 2004
Creator: Zhao, Xiaopeng
Partner: UNT Libraries

Mechanical behavior of tantalum and tantalum-tungsten alloys: texture gradients and macro/micro-response

Description: We have examined the mechanical response of unalloyed Ta and Ta-W alloy annealed plates over a wide range of loadings. It was observed in general that Ta exhibits nonuniform mechanical behavior, for example, hourglassing of compression samples and multiple instabilities during tensile deformation. In contrast, the Ta-W alloys do not exhibit any unusual nonuniform behavior. This work presents data revealing the spatial distribution of texture in Ta and Ta-W alloys. Significant variations in texture both through the thickness and from one area of the plate to another were found to be characteristic of Ta. The dominant feature of the texture variations was found to be enhanced <111> crystal direction fractions at the center of the plate, with a decreasing fraction near the surface. We find that the variation in texture in the Ta-W alloys is substantially less than that seen in Ta with primarily a <100> cube texture throughout. This study suggest that the texture gradients are responsible for the nonuniform mechanical response of Ta and that the uniform behavior of the Ta-W alloys is a consequence of the absence of texture gradients.
Date: November 30, 1996
Creator: Lassila, D.H.; Schwartz, A.J.; LeBlanc, M.M. & Wright, S.I.
Partner: UNT Libraries Government Documents Department

Chemistry modification of high oxygen-carbon powder by plasma melting: Follow up to complete the story

Description: State of the art melting of tantalum and tantalum alloys has relied on electron beam (EB) or vacuum arc remelting (VAR) for commercial ingot production. Plasma arc melting (PAM) provides an alternative for melting tantalum that contains very high levels of interstitials where other melting techniques can not be applied. Previous work in this area centered on plasma arc melt quality and final interstitial content of tantalum feedstock containing excessive levels of interstitial impurities as a function of melt rate and plasma gas. This report is an expansion of this prior study and provides the findings from the analysis of second phase components observed in the microstructure of the PAM tantalum. In addition, results from subsequent EB melting trials of PAM tantalum are included.
Date: March 1, 1998
Creator: Dunn, P.S.; Korzekwa, D.R.; Garcia, F.G. & Michaluk, C.A.
Partner: UNT Libraries Government Documents Department

Synthetic, Mechanistic, and Structural Studies of Polynuclear Metal Clusters and Hydrazido-Substituted Tantalum(V) Compounds

Description: A combined experimental and computational study on the reversible ortho-metalation exhibited by the triosmium cluster Os3(CO)10(dppm) (dppm = 1,1-bis(diphenylphosphino)methane is reported. The conversion of nonacarbonyl cluster HOs3(CO)9[&#61549;-PhP(C6H4)CH2PPh2] to Os3(CO)10(dppm) is independent of added CO and exhibits a significant inverse equilibrium isotope effect (EIE). Reductive coupling of the C-H bond in HOs3(CO)9[&#61549;-PhP(C6H4)CH2PPh2] leads to the formation of agostic C-H and two distinct aryl-&#960; species prior to the rate-limiting formation of the unsaturated cluster Os3(CO)9(dppm). Heating the unsaturated dimer H2Re2(CO)8 with Cp*Rh(CO)2 (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene) at elevated temperature affords the new trimetallic clusters H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6, and the spiked-triangular cluster HRhRe3Cp*(CO)14. H2Re2(CO)8 reacts with Cp*2Rh2(CO)2 under identical conditions to furnish H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6 as the principal products, in addition to the tetrahedral cluster H2Rh2Re2Cp*2(CO)8. H2RhRe2Cp*(CO)9 undergoes facile fragmentation in the presence of halogenated solvents and the thiols RSH (where R = H, C6H4Me-p) to afford the structurally characterized products Cp*Rh(&#61549;-Cl)3Re(CO)3, S2Rh3Cp*(CO)4, Cp*Rh(&#61549;-Cl)(&#61549;-SC6H4Me-p)2Re(CO)3, and Cp*Rh(&#61549;-SC6H4Me-p)3Re(CO)3. The new hydrazido-substituted compounds TaCl(NMe2)3[N(TMS)NMe2] (TMS = tetramethylsilyl) and Ta(NMe2)4[N(TMS)NMe2] have been synthesized and their structures established by X-ray crystallography. The latter product represents the first structurally characterized octahedral tantalum(V) complex containing a single hydrazido(I) ligand in an all-nitrogen coordinated environment about the metal center. The fluxional properties of the amido and hydrazido ligands in these new compounds have been established by VT 1H NMR spectroscopy (VT = variable temperature). Preliminary data using Ta(NMe2)4[N(TMS)NMe2] as an ALD (ALD = atomic layer deposition) precursor for the preparation of tantalum nitride and tantalum oxide thin films are presented.
Date: December 2010
Creator: Huang, Shih-huang
Partner: UNT Libraries

Dynamic material properties of refractory materials: Tantalum and tantalum/tungsten alloys

Description: We have made a careful set of impact wave-profile measurements (16 profiles) on tantalum and tantalum-tungsten alloys at relatively low stresses (to 15 GPa). Alloys used were Ta{sub 97.5}W{sub 2.5} and Ta{sub 90}W{sub 10} (wt. %) with oxygen contents of 30--70 ppM. Information available from these experiments includes Hugoniot, elastic limits, loading fates, spall strength, unloading paths, reshock structure and specimen thickness effects. Hugoniot and spall properties are illustrated, and are consistent with expectations from earlier work. Modeling the tests with the Steinberg-Lund rate-dependent material model provides for an excellent match of the shape of the plastic wave, although the release wave is not well modeled. There is also a discrepancy between experiments and calculations regarding the relative timing of the elastic and plastic waves that may be due to texture effects.
Date: August 1, 1995
Creator: Furnish, M.D.; Chhabildas, L.C.; Lassila, D.H. & Steinberg, D.J.
Partner: UNT Libraries Government Documents Department