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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Computational exploration of biomedical HfNbTaTiZr and Hf 0.5 Nb 0.5 Ta 0.5 Ti 1.5 Zr refractory high-entropy alloys

Refractory high entropy alloys (RHEAs) have been proven to be a potential candidate in the biomedical field due to their balanced mechanical properties and biocompatible composition. Recent experimental findings show that RHEAs like HfNbTaTiZr and Hf 0.5 Nb 0.5 Ta 0.5 Ti 1.5 Zr have good mechanical properties such as high polarization and wear resistance than others which establish them as potential materials for biomedical application. In this work, we performed first-principles density functional theory calculations on the mechanical and thermal properties of HfNbTaTiZr and Hf 0.5 Nb 0.5 Ta 0.5 Ti 1.5 Zr. The predicted lattice constant, density, Young's modulus, and Vickers hardness are consistent with the available experimental report, which verifies the accuracy of the applied model. The thermal coefficient of linear expansion of both RHEAs has been investigated by utilizing the Debye theory. The present methods could be applied to study other future RHEAs on exploration of their physical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Visual Impact Assessment of the Energetic Materials Complex Construction Project on Manhattan Project–Era Historic Properties, the TA-06-0037 Concrete Bowl, and the TA-22-0001 Quonset Hut

Concern for potential visual effects to historic Manhattan Project–era properties emerged early in the planning and consultation phase for the upcoming Energetic Materials Complex (EMC) construction project. In initial discussions with project managers and design team members, resource managers became aware of the need to consider potential impacts to the viewsheds of two nearby properties that are eligible for inclusion in the Manhattan Project National Historical Park (MAPR). Resource managers recognized that viewshed characteristics important to the integrity of the Concrete Bowl (Technical Area [TA-]06-0037) and the Quonset Hut (TA-22-0001) conceivably faced the prospect of lasting and irreversible visual impacts. A strategy to gather necessary data soon emerged. The approach presented to the New Mexico State Historic Preservation Officer (SHPO) on April 7, 2021, combined gathering baseline information from field visits with a geographic information system (GIS)-supported viewshed analysis. Accordingly, results from the viewshed analysis would help resource managers determine if a more comprehensive visual impact assessment (VIA) would be needed. If necessitated by the outcome of the GIS viewshed analysis, initial consultation with the SHPO specified the production of a VIA that would explore any potential visual adverse impacts to the Concrete Bowl and the Quonset Hut. Cultural resources and GIS specialists with the Laboratory performed a viewshed analysis shortly after consultation with the SHPO. The analysis indicated a high likelihood that at least one of the two Manhattan Project–era properties would experience at least a minimal level of visual impact and that a VIA would be needed. The resulting analysis provides a description of the undertaking, an account of the properties affected along with an evaluation of historical significance, an examination of potential visual impacts, and a determination of effect to the identified historic properties.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

MARSAME Release Report for Replacement Water Lines From TA-48 to TA-55, Revision 2

Environmental Protection and Compliance, Environmental Stewardship (EPC-ES) has determined that only a portion of the soil associated with Replacement Water Lines from Technical Area (TA)-48 to TA 55 (Figure 1) meets the criteria for unrestricted release to the public under Department of Energy (DOE) Order 458.1, Radiation Protection for the Public and the Environment (DOE, 2020). The remaining soil did not meet the criteria for unrestricted release and must be managed appropriately. These conclusions are based on the known history of the area combined with soil sample data collected in 2022; the findings are consistent with DOE Order 458.1 and Los Alamos National Laboratory (LANL) Functional Series Document EPC-ES-FSD-004, Environmental Radiation Protection (LANL, 2021). Sampling and data analysis, as described in this report, were sufficient to meet measurement quality objectives (MQOs) under the Multi-Agency Radiation Survey and Assessment of Materials and Equipment (MARSAME) manual (NUREG, 2009) and LANL procedures (LANL, 2020). Final approvals for waste disposition will come from LANL’s Waste Management Program.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Fundamental Effects of Al and Ta on Microstructure and Phase Transformations in the Al–Cr–Mo–Ta–Ti Refractory Complex Concentrated Alloy System

The effect of aluminum and tantalum concentrations on a refractory metal complex concentrated alloy is reported, particularly with respect to their effect on microstructure and phase composition of the alloy in cast and annealed form. Alloys with an equiatomic composition, (AlCrMoTaTi), an aluminum-lean composition (Al 0.75 CrMoTaTi), and a tantalum-lean composition (AlCrMoTa 0.75 Ti) are produced via arc melting. The alloys exhibit multiphase structures, confirmed by X-ray diffraction, microstructural characterization, and thermal analysis. The minor off-equiatomic adjustments of aluminum and tantalum in this alloy system did not drastically alter the prevalence of the Cr–Ta-based Laves phase. Correlations between thermodynamic predictions and observed phase transformations via thermal analysis are improved upon refinement of calculations removing impractical intermediate phases. As a result, experimental findings provide information for the refinement of thermodynamic modeling and deliver additional insight into the optimization of alloy compositions within this five-component system.

36 MATERIALS SCIENCE↗
DOE OSTI2022

From Protection and Prevention to Research and Discovery: Eligibility Assessment of the Health Research Laboratory (TA-43) and Historic Documentation for TA-43-0001 - Volume 1

The U.S. Department of Energy National Nuclear Security Administration Los Alamos Field Office (NA-LA) requests the New Mexico State Historic Preservation Officer (SHPO) to concur with the National Register of Historic Places (NRHP)–eligibility determinations detailed in this report for the Health Research Laboratory (HRL) complex in Technical Area 43 (TA-43) at the Los Alamos National Laboratory (LANL). As part of the LANL Footprint Reduction Program’s Decommissioning and Demolition (D&D) process, all facilities of the HRL complex are scheduled for characterization and future demolition.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2023

MARSAME Radiological Release Report for Replacement Water Lines from TA-48 to TA-55

Environmental Protection and Compliance, Environmental Stewardship (EPC-ES) has determined that only a portion of the soil associated with Replacement Water Lines from Technical Area (TA)-48 to TA55 (Figure 1) meets the criteria for unrestricted release to the public under Department of Energy (DOE) Order 458.1, Radiation Protection for the Public and the Environment (DOE, 2020). The remaining soil did not meet the criteria for unrestricted release and must be managed appropriately. These conclusions are based on the known history of the area combined with soil sample data collected in 2022; the findings are consistent with DOE Order 458.1 and Los Alamos National Laboratory (LANL) Functional Series Document EPC-ES-FSD-004, Environmental Radiation Protection (LANL, 2021). Sampling and data analysis, as described in this report, were sufficient to meet measurement quality objectives (MQOs) under the Multi-Agency Radiation Survey and Assessment of Materials and Equipment (MARSAME) manual (NUREG, 2009) and LANL procedures (LANL, 2020). Final approvals for waste disposition will come from LANL’s Waste Management Program.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Conditions Assessment and Preservation Work Plan for Portable Guard Shacks (TA-8-172 and TA-18-111)

The purpose of this report is to document the current state of deterioration and propose repairs for TA-8-172 and TA18-111, two portable guard shacks from the Los Alamos National Laboratory (LANL) which have been designated as historic resources. This preservation treatment plan has been prepared by the Historic Preservation Training Center (HPTC), a historic preservation program within the National Park Service, to ensure that the treatments comply with guidelines established in The Secretary of the Interior’s Standards for the Treatment of Historic Properties.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2024

Heterostructural interface engineering for ultrawide-gap nitrides from first principles: Ta C / Al N and Ta C / Ga N rocksalt-wurtzite interfaces

Epitaxial lattice matching is an important condition for the formation of coherent interfaces with low defect densities. However, lattice-matched substrates with the same crystal structure as the active layer are often not available, suggesting opportunities for utilizing heterostructural interfaces. For example, at high Al contents that are interesting for ultrawide-gap applications in power electronics, Al x ⁢Ga 1-x ⁢N semiconductor alloys in the (0001) orientation of the wurtzite (wz) structure become lattice-matched to (111)-oriented rocksalt (rs) Ta⁢C substrates. To predict the expected interface atomic structures under different synthesis conditions, we perform high-throughput density-functional-theory calculations, using an algorithm for systematic sampling of the possible stacking sequences of the atomic layers on the in-plane hexagonal lattice. The approach considers octahedral, tetrahedral, and prismatic coordination motifs, and is generally applicable for the modeling of commensurate rs/wz heterostructural interfaces. Our results provide guidance for synthesis control of substrate-film bonding and the polarity of ultrawide-gap Al x⁢ Ga 1-x⁢ N alloys on Ta⁢C substrates.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta by Materials Project

Ta is beta Uranium structured and crystallizes in the tetragonal P-42_1m space group. The structure is three-dimensional. there are six inequivalent Ta sites. In the first Ta site, Ta is bonded to twelve Ta atoms to form a mixture of corner, edge, and face-sharing TaTa12 cuboctahedra. There are a spread of Ta–Ta bond distances ranging from 2.77–3.09 Å. In the second Ta site, Ta is bonded to twelve Ta atoms to form a mixture of corner, edge, and face-sharing TaTa12 cuboctahedra. There are a spread of Ta–Ta bond distances ranging from 2.81–3.15 Å. In the third Ta site, Ta is bonded in a 6-coordinate geometry to fourteen Ta atoms. There are a spread of Ta–Ta bond distances ranging from 2.74–3.36 Å. In the fourth Ta site, Ta is bonded in a 2-coordinate geometry to fifteen Ta atoms. There are a spread of Ta–Ta bond distances ranging from 3.04–3.40 Å. In the fifth Ta site, Ta is bonded in a 2-coordinate geometry to fourteen Ta atoms. There are one shorter (2.66 Å) and one longer (2.68 Å) Ta–Ta bond lengths. In the sixth Ta site, Ta is bonded in a 2-coordinate geometry to fourteen Ta atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta by Materials Project

Ta crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are four inequivalent Ta sites. In the first Ta site, Ta is bonded in a 8-coordinate geometry to eight Ta atoms. There are four shorter (2.80 Å) and four longer (2.83 Å) Ta–Ta bond lengths. In the second Ta site, Ta is bonded in a 9-coordinate geometry to nine Ta atoms. There are a spread of Ta–Ta bond distances ranging from 2.93–3.02 Å. In the third Ta site, Ta is bonded in a 8-coordinate geometry to eight Ta atoms. There are a spread of Ta–Ta bond distances ranging from 2.72–2.99 Å. In the fourth Ta site, Ta is bonded in a 10-coordinate geometry to ten Ta atoms. There are one shorter (2.69 Å) and four longer (3.06 Å) Ta–Ta bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta(CoTe)2 by Materials Project

Ta(CoTe)2 crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Ta(CoTe)2 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 10-coordinate geometry to eight Co and two equivalent Te atoms. There are four shorter (2.56 Å) and four longer (2.84 Å) Ta–Co bond lengths. Both Ta–Te bond lengths are 2.87 Å. In the second Ta site, Ta is bonded in a 11-coordinate geometry to eight Co and three Te atoms. There are four shorter (2.64 Å) and four longer (2.71 Å) Ta–Co bond lengths. There are one shorter (2.82 Å) and two longer (3.02 Å) Ta–Te bond lengths. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are a spread of Co–Co bond distances ranging from 2.56–2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the second Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.60 Å) and one longer (2.84 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the third Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.56 Å) and one longer (2.60 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the fourth Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.64 Å) and one longer (2.71 Å) Co–Ta bond lengths. The Co–Co bond length is 2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. There are three inequivalent Te sites. In the first Te site, Te is bonded in a 5-coordinate geometry to one Ta and four Co atoms. In the second Te site, Te is bonded in a 6-coordinate geometry to two Ta, two Co, and two equivalent Te atoms. There are one shorter (3.25 Å) and one longer (3.33 Å) Te–Te bond lengths. In the third Te site, Te is bonded in a 4-coordinate geometry to four Co atoms.

36 MATERIALS SCIENCE↗