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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Fabrication of Low-Cost Large-Volume Ceramic A 2 HfX 6 (A= Cs or Tl, X = Cl, Br, or I) Scintillators for Gamma Ray Detection (SBIR Phase I Final Technical Report)

Scintillator crystals play an important role in the radiation detection field. Widespread use of scintillators as gamma-ray detectors is largely generated by their extensive availability and tunable properties, such high light output, high stopping power (Z eff ), fast decay time, and good proportionality. Additionally, the cost for manufacturing a scintillation detector like NaI:Tl is usually considerably lower than the cost for manufacturing a semiconductor detector like CdZnTe. Because there is no such thing as an ideal scintillation material, an application requiring certain detection characteristics may incorporate a scintillator tailored to its specific properties. The vast variety of applications and requirements necessitates more research into new scintillation materials and/or better methods of producing existing materials.The goal of this project was to grow low cost and environmentally stable inorganic transparent ceramic scintillators with excellent gamma ray resolution, excellent energy proportionality, excellent detection efficiency due to high density (>5 g/cm 3 ) and very high Z eff (55-80), and good light yields (>40,000 ph/MeV). In Phase I Xtallized Intelligence, Inc. (XI, Inc) developed a novel ceramic fabrication technique to produce low cost and environmentally stable highly efficient inorganic transparent ceramic scintillators of various dimensions. XI, Inc., collaborating with Fisk University (Fisk), investigated the scintillation properties of these new ceramic scintillators and compared them to in their single crystal counterparts. The results of this Phase I project show that successful production of high-quality inorganic halide ceramic scintillators Cs 2 HfCl 6 (CHC) and Tl 2 HfCl 6 (THC). Both ceramic CHC and THC scintillators have achieved good performance close to the performance of their single crystal counterparts. Fabricating these inorganic ceramic scintillators mitigate many issues encountered during conventional bulk crystal growth by melt methods. Additional benefits of the ceramic fabrication technique include high production yield, low production cost, fast production time, and no material waste Inorganic transparent ceramic scintillators produced in this project will enhance cost effectiveness at the instrument level based on low projected cost of the proposed compounds, as much smaller crystal sizes would be required to achieve similar efficiency as current radioisotope identification devices (RIID’s) used in homeland security applications as well as spectrometers in high energy physics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Double-Layer Kagome Metals Pt 3 Tl 2 and Pt 3 In 2

The connectivity and inherent frustration of the kagome lattice can produce interesting electronic structures and behaviors in compounds containing this structural motif. Here we report the properties of Pt 3 X 2 (X = In and Tl) that adopt a double-layer kagome net structure related to that of the topologically nontrivial high-temperature ferromagnet Fe 3 Sn 2 and the density wave hosting compound V 3 Sb 2 . We examined the structural and physical properties of single crystal Pt 3 Tl 2 and polycrystalline Pt 3 In 2 using X-ray and neutron diffraction, magnetic susceptibility, heat capacity, and electrical transport measurements, along with density functional theory calculations of the electronic structure. Our calculations show that Fermi levels lie in pseudogaps in the densities of states with several bands contributing to transport, and this is consistent with our Hall effect, magnetic susceptibility, and heat capacity measurements. Although electronic dispersions, characteristic of simple kagome nets with nearest-neighbor hopping, are not clearly seen, likely due to the extended nature of the Pt 5d states, we do observe moderately large and non-saturating magnetoresistance values and quantum oscillations in the magnetoresistance and magnetization associated with the kagome nets of Pt.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Preparation of high T(c) Tl-Ba-Ca-Cu-O thin films by pulsed laser evaporation and Tl2O3 vapor processing

Tl-Ba-Ca-Cu-O superconducting thin films with zero-resistance temperatures up to 115 K have been prepared using a Tl2O3 vapor process on Ba-Ca-Cu-O precursor thin films. The Ba-Ca-Cu-O thin films were made by laser deposition on Y-stabilized ZrO2 substrates. This technique minimizes problems caused by the toxicity of Tl2O3, and its subsequent decomposition to the volatile and toxic Tl2O upon heating. Therefore, it may have practical application in the fabrication of high T(c) Tl-Ba-Ca-Cu-O superconducting thin-film devices.

Johs, B.↗
NASA NTRS1993

Experimental partitioning studies near the Fe-FeS eutectic, with an emphasis on elements important to iron meteorite chronologies (Pb, Ag, Pd, and Tl)

Partitioning coefficients for metal/sulfide liquid, troilite/sulfide liquid, and schreibersite/sulfide liquid were determined for Ag, Au, Mo, Ni, Pd, and Tl (using EMPA and proton-induced X-ray microprobe and ion microprobe analyses) in order to understand the chronometer systems of iron meteorites. In general, the obtained schreibersite/metal and troilite/metal partition coefficients for 'compatible' elements were quite similar to those inferred from natural assemblages, reinforcing an earlier made conclusion that there is a class of elements for which experimental troilite/metal and schreibersite/metal partition coefficients approximate those inferred from natural samples. The consistency between experimental and natural assemblages, however, was not observed for Ag, Pb, and Tl, indicating that the abundances of these elements determined in 'metal' and 'troilite' separates from iron meteorites are influenced by trace minerals that concentrate incompatible elements.

Jones, J. H.↗
NASA NTRS1994

Development of high Tc (greater than 100 K) Bi, Tl and Y-based materials as superconducting circuit elements

Experimental work on this project over the last four years has resulted in establishing processing and characterization techniques for producing both the Bi-based and Tl-based superconductors in their high temperature (2223) forms. In the bulk, dry pressed form, maximum critical temperatures (Tc) of 108.2 K and 117.8 K, respectively, were measured. Results have further shown that the Bi and Tl-based superconducting materials in bulk form are noticeably different from the Y-based 123 material in that superconductivity is considerably harder to achieve, maintain, and reproduce. This is due primarily to the difficulty in obtaining the higher Tc phase in pure form since it commonly co-exists with other undesirable, lower Tc phases. In particular, it has been found that long processing times for calcining and firing (20 - 200 hrs.) and close control of temperatures which are very near the melting point are required in order to obtain higher proportions of the desirable, high Tc (2223) phase. Thus far, the BSCCO bulk materials has been prepared in uniaxially pressed, hot pressed, and tapecast form. The uniaxially pressed material has been synthesized by the mixed oxide, coprecipitation, and melt quenching processes. The tapecast and hot pressed materials have been prepared via the mixed oxide process. In addition, thick films of BSCCO (2223 phase) have been prepared by screen printing on to yttria and magnesia stabilized zirconia with only moderate success; i.e., superconductivity was achieved in these thick films, but the highest Tc obtained in these films was 89.0 K. The Tc's of the bulk hot pressed, tapecast, and screen printed thick film materials were found to be 108.2, 102.4, and 89.0 K, respectively.

Haertling, Gene↗
NASA NTRS1994

A survey of the core-congruential formulation for geometrically nonlinear TL finite elements

This article presents a survey of the core-congruential formulation (CCF) for geometrically nonlinear mechanical finite elements based on the total Lagrangian (TL) kinematic description. Although the key ideas behind the CCF can be traced back to Rajasekaran and Murray in 1973, it has not subsequently received serious attention. The CCF is distinguished by a two-phase development of the finite element stiffness equations. The initial phase developed equations for individual particles. These equations are expressed in terms of displacement gradients as degrees of freedom. The second phase involves congruential-type transformations that eventually binds the element particles of an individual element in terms of its node-displacement degrees of freedom. Two versions of the CCF, labeled direct and generalized, are distinguished. The direct CCF (DCCF) is first described in general form and then applied to the derivation of geometrically nonlinear bar, and plane stress elements using the Green-Lagrange strain measure. The more complex generalized CCF (GCCF) is described and applied to the derivation of 2D and 3D Timoshenko beam elements. Several advantages of the CCF, notably the physically clean separation of material and geometric stiffnesses, and its independence with respect to the ultimate choice of shape functions and element degrees of freedom, are noted. Application examples involving very large motions solved with the 3D beam element display the range of applicability of this formulation, which transcends the kinematic limitations commonly attributed to the TL description.

Felippa, Carlos A.↗
NASA NTRS1993

Performance of two-pole bandpass filters photodefined on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films

The performance of 7.3-GHz two-pole bandpass filters (5% bandwidth) fabricated on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films deposited on LaAlO3 is discussed. At 77 K, the Tl-Ba-Ca-Cu-O and Y-Ba-Cu-O superconducting filters exhibited minimum passband insertion losses of 0.3 and 1.2 dB, respectively. An insertion loss of 3.4 dB was measured for an all-gold filter at 77 K.

TWO POLE BANDPASS FILTERS↗
NASA NTRS1995

Improvement of critical current density in thallium-based (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) superconductors

Epitaxial (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) ((Tl,Bi)-1223) thin films on (100) single crystal LaAlO3 substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field cooled magnetization, and transport critical current density (J(sub c)) were measured. The zero-resistance temperature was 105-111 K. J(sub c) at 77 K and zero field was greater than 2 x 10(exp 6) A/sq cm. The films exhibited good flux pinning properties.

Ren, Z. F.↗
DOE OSTI2020

Materials Data on Tl(FeS)2 by Materials Project

Tl(FeS)2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two thallium molecules and two FeS sheets oriented in the (0, 0, 1) direction. In each FeS sheet, Fe is bonded to four equivalent S atoms to form a mixture of distorted edge and corner-sharing FeS4 tetrahedra. All Fe–S bond lengths are 2.35 Å. S is bonded in a 4-coordinate geometry to four equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(BH)6 by Materials Project

Tl(BH)6 crystallizes in the cubic Fm-3 space group. The structure is zero-dimensional and consists of forty-eight boranediylradical molecules and eight thallium molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(NiSe)2 by Materials Project

TlNi2Se2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ni+1.50+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing NiSe4 tetrahedra. All Ni–Se bond lengths are 2.37 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All Tl–Se bond lengths are 3.41 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Ni+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(CoSe)2 by Materials Project

TlCo2Se2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Co+1.50+ is bonded to four equivalent Se2- atoms to form a mixture of corner and edge-sharing CoSe4 tetrahedra. All Co–Se bond lengths are 2.34 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All Tl–Se bond lengths are 3.44 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Co+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(CoS)2 by Materials Project

TlCo2S2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Co+1.50+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing CoS4 tetrahedra. All Co–S bond lengths are 2.21 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Tl–S bond lengths are 3.37 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Co+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(Cu3S2)2 by Materials Project

TlCu6S4 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Cu+1.17+ sites. In the first Cu+1.17+ site, Cu+1.17+ is bonded to four equivalent S2- atoms to form a mixture of corner and edge-sharing CuS4 tetrahedra. All Cu–S bond lengths are 2.38 Å. In the second Cu+1.17+ site, Cu+1.17+ is bonded to four S2- atoms to form a mixture of corner and edge-sharing CuS4 tetrahedra. There are two shorter (2.28 Å) and two longer (2.51 Å) Cu–S bond lengths. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Tl–S bond lengths are 3.39 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four equivalent Cu+1.17+ and four equivalent Tl1+ atoms. In the second S2- site, S2- is bonded in a body-centered cubic geometry to eight Cu+1.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(NiS)2 by Materials Project

TlNi2S2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ni+1.50+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing NiS4 tetrahedra. All Ni–S bond lengths are 2.25 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Tl–S bond lengths are 3.33 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Ni+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(CuTe)2 by Materials Project

Cu2TlTe2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cu+1.50+ is bonded to four equivalent Te2- atoms to form a mixture of corner and edge-sharing CuTe4 tetrahedra. All Cu–Te bond lengths are 2.64 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent Te2- atoms. All Tl–Te bond lengths are 3.58 Å. Te2- is bonded in a 8-coordinate geometry to four equivalent Cu+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(CuS)2 by Materials Project

TlCu2S2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cu+1.50+ is bonded to four equivalent S2- atoms to form a mixture of corner and edge-sharing CuS4 tetrahedra. All Cu–S bond lengths are 2.35 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Tl–S bond lengths are 3.35 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Cu+1.50+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(V3S4)2 by Materials Project

TlV6S8 crystallizes in the trigonal P-3 space group. The structure is three-dimensional. V+2.50+ is bonded to six S2- atoms to form a mixture of edge, corner, and face-sharing VS6 octahedra. The corner-sharing octahedra tilt angles range from 44–53°. There are a spread of V–S bond distances ranging from 2.32–2.58 Å. Tl1+ is bonded in a 6-coordinate geometry to six equivalent S2- atoms. All Tl–S bond lengths are 3.12 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to four equivalent V+2.50+ and one Tl1+ atom. In the second S2- site, S2- is bonded to six equivalent V+2.50+ atoms to form distorted face-sharing SV6 pentagonal pyramids.

36 MATERIALS SCIENCE↗