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33 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on K2WCl6 by Materials Project

K2WCl6 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K1+ is bonded to twelve equivalent Cl1- atoms to form KCl12 cuboctahedra that share corners with twelve equivalent KCl12 cuboctahedra, faces with six equivalent KCl12 cuboctahedra, and faces with four equivalent WCl6 octahedra. All K–Cl bond lengths are 3.54 Å. W4+ is bonded to six equivalent Cl1- atoms to form WCl6 octahedra that share faces with eight equivalent KCl12 cuboctahedra. All W–Cl bond lengths are 2.39 Å. Cl1- is bonded in a distorted single-bond geometry to four equivalent K1+ and one W4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TeWCl9 by Materials Project

WTeCl9 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of one WTeCl9 ribbon oriented in the (1, 0, 0) direction. W5+ is bonded to six Cl1- atoms to form WCl6 octahedra that share corners with three equivalent TeCl6 octahedra. The corner-sharing octahedra tilt angles range from 45–57°. There are a spread of W–Cl bond distances ranging from 2.28–2.43 Å. Te4+ is bonded to six Cl1- atoms to form distorted TeCl6 octahedra that share corners with three equivalent WCl6 octahedra. The corner-sharing octahedra tilt angles range from 45–57°. There are a spread of Te–Cl bond distances ranging from 2.33–3.22 Å. There are nine inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 2-coordinate geometry to one W5+ and one Te4+ atom. In the second Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one W5+ and one Te4+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one W5+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one W5+ atom. In the fifth Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the sixth Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one W5+ and one Te4+ atom. In the seventh Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the eighth Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the ninth Cl1- site, Cl1- is bonded in a single-bond geometry to one W5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Preparation of tantalum-based alloys by a unique CVD process

The paper describes a sequential pulsing technique for deposition of refractory alloys and evaluates the technique for the deposition of the tantalum-base alloys Ta-10W (Ta-10 st% W) and T-111 (Ta-8 wt% W-2 wt% Hf). The deposition cycle for Ta-10W was chosen as alternate injections of TaCl5 plus hydrogen and WCl6 plus hydrogen. The cycle for T-111 was chosen as injections of TaCl5 plus hydrogen interspersed with injections of WCl6 plus hydrogen. A temperature range of 900-1300 C was chosen for both alloys. The ability of the pulse process to blanket a uniformly heated section of substrate with a mixture of gases, whose composition varies not with position on the substrate but instead with time of residence in the reactor, allows metal of uniform thickness to be deposited. It is shown that Ta and W can be deposited at high temperature with the formation of a dense columnar grain structure, so that the feasibility of preparing uniformly thick deposits of these elements by a 'pulsing' modification of CVD is demonstrated. A similar attempt to deposit T-111 was unsuccessful due to the difficulty in reducing HfCl4.

Bryant, W. A.↗
DOE OSTI2020

Materials Data on K3W2Cl9 by Materials Project

K3W2Cl9 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine Cl1- atoms. There are three shorter (3.24 Å) and six longer (3.44 Å) K–Cl bond lengths. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to nine Cl1- atoms. There are a spread of K–Cl bond distances ranging from 3.31–3.63 Å. W3+ is bonded to six Cl1- atoms to form face-sharing WCl6 octahedra. There are three shorter (2.42 Å) and three longer (2.54 Å) W–Cl bond lengths. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted see-saw-like geometry to three K1+ and one W3+ atom. In the second Cl1- site, Cl1- is bonded in a 5-coordinate geometry to three K1+ and two equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on W(S4Cl3)2 by Materials Project

WCl6(S)8 is Magnesium tetraboride-like structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two octasulfur molecules and two tungsten(vi) chloride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H32WC8N4Cl7 by Materials Project

WCl6((CH3)2NH2)2C4N2H16Cl is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic P2_12_12 space group. The structure is zero-dimensional and consists of four dimethylazanium molecules, two tungsten(vi) chloride molecules, and two C4N2H16Cl clusters. In each C4N2H16Cl cluster, there are two inequivalent C2- sites. In the first C2- site, C2- is bonded to one N3- and three H1+ atoms to form corner-sharing CH3N tetrahedra. The C–N bond length is 1.49 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the second C2- site, C2- is bonded to one N3- and three H1+ atoms to form corner-sharing CH3N tetrahedra. The C–N bond length is 1.49 Å. All C–H bond lengths are 1.10 Å. N3- is bonded in a tetrahedral geometry to two C2- and two H1+ atoms. There is one shorter (1.04 Å) and one longer (1.06 Å) N–H bond length. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- and one Cl1- atom. The H–Cl bond length is 2.02 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. Cl1- is bonded in a bent 150 degrees geometry to two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on WSe6ICl6 by Materials Project

WCl6(Se)4Se2I crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four selenium molecules, one tungsten(vi) chloride molecule, and one Se2I cluster. In the Se2I cluster, Se+0.33+ is bonded in a single-bond geometry to one I1- atom. The Se–I bond length is 2.79 Å. I1- is bonded in a linear geometry to two equivalent Se+0.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2WCl6 by Materials Project

WCl6(Te)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four tellurium molecules and two tungsten(vi) chloride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2WCl6 by Materials Project

WCl6(Te)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of eight tellurium molecules and four tungsten(vi) chloride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on WCl4 by Materials Project

WCl4 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two WCl4 ribbons oriented in the (0, 1, 0) direction. W4+ is bonded to six Cl1- atoms to form edge-sharing WCl6 octahedra. There are a spread of W–Cl bond distances ranging from 2.31–2.53 Å. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a water-like geometry to two equivalent W4+ atoms. In the second Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent W4+ atoms. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one W4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on WNCl6 by Materials Project

(WCl6)2N2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four ammonia molecules and four tungsten(vi) chloride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tungsten Electrodeposition

Tungsten is a refractory metal with a very high melting point (3422 °C), hardness (7.5 on Mohs hardness scale), and chemical resistance, making it useful in applications with extreme conditions. Electrodeposition is an attractive technique for coating metals because of its scalability and applicability to objects of intricate shape, though tungsten electrodeposition remains difficult. Some multi-step methods first coat either a sacrificial metal such as zinc or a layer of tungsten oxide which is then converted to metallic tungsten with WCl6 immersion (i.e. a redox replacement reaction) or heating in a reducing atmosphere, respectively. Single step deposition would save time and money, making it more viable on an industrial scale. Most reports detailing direct tungsten electrodeposition use molten salts which are energy intensive, hazardous, and difficult to maintain. Few reports have demonstrated single-step, low temperature electrodeposition deposition of tungsten in atmosphere. An article from 1931 reports successful metal tungsten electrodeposition from a highly basic sodium tungstate solution, though the authors reported very low current efficiency (<1%) and required heating to 80+ °C to obtain metallic films. This report outlines our attempts to electroplate tungsten from various solutions on different electrode materials, none of which succeeded. Our intent is to guide future researchers at Los Alamos National Laboratory that would attempt tungsten electrodeposition.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Development and study of chemical vapor deposited tantalum base alloys

A technique for the chemical vapor deposition of alloys was developed. The process, termed pulsing, involves the periodic injection of reactant gases into a previously-evacuated reaction chamber where they blanket the substrate almost instantaneously. Formation of alternating layers of the alloy components and subsequent homogenization allows the formation of an alloy of uniform composition with the composition being determined by the duration and relative numbers of the various cycles. The technique has been utilized to produce dense alloys of uniform thickness and composition (Ta- 10 wt % W) by depositing alternating layers of Ta and W by the hydrogen reduction of TaCl5 and WCl6. A similar attempt to deposit a Ta - 8 wt % W - 2 wt% Hf alloy was unsuccessful because of the difficulty in reducing HfCl4 at temperatures below those at which gas phase nucleation of Ta and W occurred.

Meier, G. H.↗
NASA NTRS1975

Weldability of three forms of chemically vapor deposited tungsten

Methods were developed for electron-beam welding several forms of chemically vapor-deposited tungsten. Weld ductility was evaluated from the results of ductile-brittle transition-temperature determinations. Welds in tungsten produced from WF6 were considerably more ductile than those associated with WCl6-produced tungsten. The larger grain size of the latter material was largely responsible for this behavior.

Bryant, W. A.↗
NASA NTRS2014

Development Status of a CVD System to Deposit Tungsten onto UO2 Powder via the WCI6 Process

Nuclear Thermal Propulsion (NTP) is under development for deep space exploration. NTP's high specific impulse (> 850 second) enables a large range of destinations, shorter trip durations, and improved reliability. W-60vol%UO2 CERMET fuel development efforts emphasize fabrication, performance testing and process optimization to meet service life requirements. Fuel elements must be able to survive operation in excess of 2850 K, exposure to flowing hydrogen (H2), vibration, acoustic, and radiation conditions. CTE mismatch between W and UO2 result in high thermal stresses and lead to mechanical failure as a result UO2 reduction by hot hydrogen (H2) [1]. Improved powder metallurgy fabrication process control and mitigated fuel loss can be attained by coating UO2 starting powders within a layer of high density tungsten [2]. This paper discusses the advances of a fluidized bed chemical vapor deposition (CVD) system that utilizes the H2-WCl6 reduction process.

Mireles, O. R.↗