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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Atom probe tomography characterization of ion and neutron irradiated Alloy 800H

Alloy 800H is a high temperature and creep resistant alloy, and is considered as a candidate alloy for use in Generation IV nuclear reactor systems. To clarify the alloy's behavior under irradiation, samples were subjected to single ion irradiations up to 20 dpa at 440°C, a dual ion/He irradiation to 17 dpa at 460°C, and a neutron irradiation to 17 dpa at 385°C. The irradiated microstructures were characterized using atom probe tomography to complement previously published transmission electron microscopy studies. Additionally, after single ion irradiation, sparse fine Al and Ti clusters were observed after 1dpa, while high number densities of nanoscale Ni-Al-Ti clusters, Cr-Ti rich carbides, and Si-decorated dislocation loops developed after 10 and 20 dpa. The microstructure formed during single ion irradiation exhibited a strong depth dependence. No significant differences were observed between the single and dual ion irradiations. While Ni-Al-Ti clusters, Cr-Ti rich carbides, and Si-decorated dislocation loops were also observed after neutron irradiation, the neutron-irradiated microstructure differed from those found in the ion-irradiated samples.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Basal Plane Hydrogen Evolution Activity from Mixed Metal Nitride MXenes Measured by Scanning Electrochemical Microscopy

2D early transition metal carbide and nitride MXenes have intriguing properties for electrochemical energy storage and electrocatalysis. These properties can be manipulated by modifying the basal plane chemistry. Here, mixed transition metal nitride MXenes, M-Ti 4 N 3 T x (M = V, Cr, Mo, or Mn; T x = O and/or OH), are developed by modifying pristine exfoliated Ti 4 N 3 T x MXene with V, Cr, Mo, and Mn salts using a simple solution-based method. The resulting mixed transition metal nitride MXenes contain 6–51% metal loading (cf. Ti) that exhibit rich electrochemistry including highly tunable hydrogen evolution reaction (HER) electrocatalytic activity in a 0.5 m H 2 SO 4 electrolyte as follows: V-Ti 4 N 3 T x > Cr-Ti 4 N 3 T x > Mo-Ti 4 N 3 T x > Mn-Ti 4 N 3 T x > pristine Ti 4 N 3 T x with overpotentials as low as 330 mV at -10 mA cm -2 with a charge-transfer resistance of 70 O. Scanning electrochemical microscopy (SECM) reveals the electrochemical activity of individual MXene flakes. The SECM data corroborate the bulk HER activity trend for M-Ti 4 N 3 T x as well as provide the first experimental evidence that HER results from catalysis on the MXene basal plane. These electrocatalytic results demonstrate a new pathway to tune the electrochemical properties of MXenes for water splitting and related electrochemical applications.

2D materials↗
DOE OSTI2022

Superconducting phase of Ti x O y thin films grown by molecular beam epitaxy

Here we investigate the complex relationship between the growth conditions and the structural and transport properties of Ti x O y thin films grown by molecular beam epitaxy. Transport properties ranging from metallicity to superconductivity and insulating states are stabilized by effectively tuning the O/Ti ratio via the Ti flux rate and the O partial pressure P Ox for films grown on (0001)-Al 2 O 3 substrates at 850° C. A cubic c-TiO 1±δ buffer layer is formed for low O/Ti ratios, while a corundum cr-Ti 2 O 3 layer is formed under higher-oxidizing conditions. Metallicity is observed for c-TiO 1-δ buffer layers. The superconducting γ -Ti 3 O 5 Magnéli phase is found to nucleate on a c-TiO 1-δ buffer for intermediate POx conditions, and an insulator-superconducting transition is observed at 4.5 K (T$^{onset}_{C}$ = 6K) for 85 nm thick films. Strain relaxation of γ -Ti 3 O 5 occurs with increasing film thickness and correlates with a thickness-dependent increase in T C observed for Ti x O y thin films.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Materials Data on TiCr2 by Materials Project

TiCr2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ti is bonded in a 12-coordinate geometry to four equivalent Ti and twelve equivalent Cr atoms. All Ti–Ti bond lengths are 2.97 Å. All Ti–Cr bond lengths are 2.85 Å. Cr is bonded to six equivalent Ti and six equivalent Cr atoms to form a mixture of edge, corner, and face-sharing CrTi6Cr6 cuboctahedra. All Cr–Cr bond lengths are 2.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiCr2 by Materials Project

TiCr2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ti is bonded in a 12-coordinate geometry to four equivalent Ti and twelve Cr atoms. There are three shorter (2.97 Å) and one longer (2.98 Å) Ti–Ti bond lengths. There are three shorter (2.81 Å) and nine longer (2.86 Å) Ti–Cr bond lengths. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to six equivalent Ti and six equivalent Cr atoms to form a mixture of edge, corner, and face-sharing CrTi6Cr6 cuboctahedra. All Cr–Cr bond lengths are 2.44 Å. In the second Cr site, Cr is bonded to six equivalent Ti and six Cr atoms to form a mixture of edge, corner, and face-sharing CrTi6Cr6 cuboctahedra. There are two shorter (2.39 Å) and two longer (2.49 Å) Cr–Cr bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiCr2 by Materials Project

TiCr2 is Hexagonal Laves-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are four inequivalent Ti sites. In the first Ti site, Ti is bonded in a 12-coordinate geometry to four Ti and twelve Cr atoms. There are one shorter (2.96 Å) and three longer (2.97 Å) Ti–Ti bond lengths. There are a spread of Ti–Cr bond distances ranging from 2.83–2.86 Å. In the second Ti site, Ti is bonded in a 12-coordinate geometry to four Ti and twelve Cr atoms. There are three shorter (2.97 Å) and one longer (2.98 Å) Ti–Ti bond lengths. There are three shorter (2.81 Å) and nine longer (2.85 Å) Ti–Cr bond lengths. In the third Ti site, Ti is bonded in a 12-coordinate geometry to four Ti and twelve Cr atoms. The Ti–Ti bond length is 2.96 Å. There are a spread of Ti–Cr bond distances ranging from 2.83–2.86 Å. In the fourth Ti site, Ti is bonded in a 12-coordinate geometry to four Ti and twelve Cr atoms. There are three shorter (2.97 Å) and one longer (2.98 Å) Ti–Ti bond lengths. There are three shorter (2.81 Å) and nine longer (2.85 Å) Ti–Cr bond lengths. There are three inequivalent Cr sites. In the first Cr site, Cr is bonded to six Ti and six Cr atoms to form a mixture of edge, face, and corner-sharing CrTi6Cr6 cuboctahedra. There are two shorter (2.41 Å) and four longer (2.43 Å) Cr–Cr bond lengths. In the second Cr site, Cr is bonded to six Ti and six Cr atoms to form a mixture of edge, face, and corner-sharing CrTi6Cr6 cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.38–2.48 Å. In the third Cr site, Cr is bonded to six Ti and six Cr atoms to form a mixture of edge, face, and corner-sharing CrTi6Cr6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti4Cr by Materials Project

Ti4Cr crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. there are two inequivalent Ti sites. In the first Ti site, Ti is bonded in a 2-coordinate geometry to two equivalent Ti and two equivalent Cr atoms. Both Ti–Ti bond lengths are 2.89 Å. Both Ti–Cr bond lengths are 2.45 Å. In the second Ti site, Ti is bonded in a 8-coordinate geometry to ten Ti atoms. There are a spread of Ti–Ti bond distances ranging from 2.80–3.07 Å. Cr is bonded in a 4-coordinate geometry to four equivalent Ti atoms.

36 MATERIALS SCIENCE↗