Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Pd-V”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Acceleration of Pd-V intermetallic diffusion by hydrogen

Vanadium-based membranes have great potential for hydrogen purification due to their perfect selectivity, high permeability, and relatively low cost. With appropriate surface cleaning, V efficiently permeates hydrogen at elevated temperature, but performance declines due to its affinity to absorb impurities. Here, the application of palladium thin films maintains a clean surface that catalyzes hydrogen dissociation and recombination. Hydrogen permeation in Pd-V-Pd membranes initially reach theoretical permeability, but declines due to Pd-V interdiffusion. The objective of this work was to quantify the intermetallic diffusion process as a function of temperature and ambient. Pd-V composites were subjected to various annealing treatments and characterized using Auger electron spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy, as well as correlated to measurements of membrane permeability. In an inert environment Pd-V interdiffusion was observable as low as 300 °C, and the diffusion coefficient had an activation energy of 44 kJ/mol. Furthermore, the presence of hydrogen at partial pressures > 10 kPa accelerated interdiffusion six-fold at T = 400 °C. Membrane performance degraded with an activation energy 75 kJ/mol, suggesting that intermetallic diffusion leads to both a loss of catalytic activity and as well as degradation of bulk permeability. These findings provide a baseline for evaluating hydrogen permeable interdiffusion barriers to overcome these challenges.

08 HYDROGEN↗
DOE OSTI2022

Density functional theory study of formation and diffusion of hydrogen, deuterium, and tritium in Pd-V intermetallic compounds

Permeation of hydrogen isotopes in palladium/vanadium bimetallic membranes is known to deteriorate over time because of Pd-V interdiffusion. Additionally, intermetallic compounds may form in the interdiffusion region. Density functional theory is employed to study how Pd-V compounds may affect the permeation. Three compounds Pd 8 V, alpha-Pd 2 V, and PdV 4 are explored in this study. Formation and migration energies of hydrogen, deuterium, and tritium are calculated and subsequently compared to the data in pure Pd and V metals. The calculations show that both the formation and migration energies in the compounds are higher than in the pure metals. Thus, the permeation of these isotopes in the compounds is lower than in the pure metals. In addition, the least permeable compound is the one near the middle of the composition range, i.e. the alpha-Pd 2 V. The results provide atomistic insight for the permeation reduction in Pd/V membranes as interdiffusion progresses.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Fusion Blanket and Fuel Cycle Research at PNNL: FY22 Year-end Report

During the reporting period, research at PNNL focused on two tasks within the DOE Fusion Blanket and Fuel Cycle Program. Research on Task 1, Tritium Extraction from Pb-Li and He Using a Vacuum Permeator, focused on atomistic modeling to better understand tritium transport in Pd-coated V vacuum permeators. As a lower cost alternative to Pd permeators, thin coatings of Pd (or other noble metals) can be deposited over a substrate like V. However, the permeation performance of composite metal membranes degrades over time, due to the formation of intermetallics at the coating-substrate interface. Computational studies were performed to better understand tritium transport through these Pd-V intermetallics. The results of the FY22 Pd-V modeling study were recently submitted for publication in Computational Materials Science and presented at the Technology of Fusion Energy conference. Future work in this area will focus on interdiffusion barriers to prevent intermetallic formation that is deleterious to tritium transport. There are opportunities for collaboration with researchers at the Colorado School of Mines, who are manufacturing and testing candidate interdiffusion barriers. Research on Task 3, Solid Breeder Materials, included ion irradiation and post-irradiation characterization of lithium orthosilicate (Li 4 SiO 4 ) and lithium metasilicate (Li 2 SiO 3 ) to improve fundamental understanding of irradiation effects, in combination with atomistic modeling focused on the energetics of He clustering in these two ceramic phases. The results of the study suggested that the Li 4 SiO 4 phase, which is more desirable as a solid breeder due to its higher Li density, was amorphized during ion irradiation while the Li 2 SiO 3 phase appeared to be more resistant to irradiation damage. It is possible that Li loss contributed to the poor irradiation performance of the Li 4 SiO 4 , and some thoughts are provided regarding coatings that could be applied to solid breeders like this to prevent Li loss at elevated temperature while not hindering tritium diffusion. The results of the FY22 ion irradiation study were recently submitted for publication in Journal of Nuclear Materials and presented at the 22nd International Conference on Ion Beam Modification of Materials. Future work in this area will focus on Li-rich ceramics such as Li 5 AlO 4 and Li 8 ZrO 6 that have high Li density and should provide rapid tritium release based on previous work with less Li-rich ceramics.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on VPd2 by Materials Project

VPd2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. V is bonded to two equivalent V and ten equivalent Pd atoms to form distorted VV2Pd10 cuboctahedra that share corners with two equivalent VV2Pd10 cuboctahedra, corners with ten equivalent PdV5Pd7 cuboctahedra, edges with twelve equivalent VV2Pd10 cuboctahedra, edges with twelve equivalent PdV5Pd7 cuboctahedra, faces with four equivalent VV2Pd10 cuboctahedra, and faces with fourteen equivalent PdV5Pd7 cuboctahedra. Both V–V bond lengths are 2.75 Å. There are eight shorter (2.71 Å) and two longer (2.82 Å) V–Pd bond lengths. Pd is bonded to five equivalent V and seven equivalent Pd atoms to form distorted PdV5Pd7 cuboctahedra that share corners with five equivalent VV2Pd10 cuboctahedra, corners with seven equivalent PdV5Pd7 cuboctahedra, edges with six equivalent VV2Pd10 cuboctahedra, edges with eighteen equivalent PdV5Pd7 cuboctahedra, faces with seven equivalent VV2Pd10 cuboctahedra, and faces with eleven equivalent PdV5Pd7 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.70–2.77 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V3Pd by Materials Project

V3Pd crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. V is bonded in a 6-coordinate geometry to two equivalent V and four equivalent Pd atoms. Both V–V bond lengths are 2.41 Å. All V–Pd bond lengths are 2.69 Å. Pd is bonded to twelve equivalent V atoms to form a mixture of edge and face-sharing PdV12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VPd3 by Materials Project

Pd3V is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. V is bonded to twelve equivalent Pd atoms to form VPd12 cuboctahedra that share corners with twelve equivalent VPd12 cuboctahedra, edges with twenty-four equivalent PdV4Pd8 cuboctahedra, faces with six equivalent VPd12 cuboctahedra, and faces with twelve equivalent PdV4Pd8 cuboctahedra. All V–Pd bond lengths are 2.76 Å. Pd is bonded to four equivalent V and eight equivalent Pd atoms to form distorted PdV4Pd8 cuboctahedra that share corners with twelve equivalent PdV4Pd8 cuboctahedra, edges with eight equivalent VPd12 cuboctahedra, edges with sixteen equivalent PdV4Pd8 cuboctahedra, faces with four equivalent VPd12 cuboctahedra, and faces with fourteen equivalent PdV4Pd8 cuboctahedra. All Pd–Pd bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VPd3 by Materials Project

Pd3V is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. V is bonded to twelve Pd atoms to form VPd12 cuboctahedra that share corners with four equivalent VPd12 cuboctahedra, corners with eight equivalent PdV4Pd8 cuboctahedra, edges with eight equivalent VPd12 cuboctahedra, edges with sixteen equivalent PdV4Pd8 cuboctahedra, faces with four equivalent VPd12 cuboctahedra, and faces with fourteen PdV4Pd8 cuboctahedra. There are four shorter (2.74 Å) and eight longer (2.76 Å) V–Pd bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to four equivalent V and eight Pd atoms to form distorted PdV4Pd8 cuboctahedra that share corners with twelve equivalent PdV4Pd8 cuboctahedra, edges with eight equivalent VPd12 cuboctahedra, edges with sixteen PdV4Pd8 cuboctahedra, faces with four equivalent VPd12 cuboctahedra, and faces with fourteen PdV4Pd8 cuboctahedra. There are four shorter (2.74 Å) and four longer (2.76 Å) Pd–Pd bond lengths. In the second Pd site, Pd is bonded to four equivalent V and eight equivalent Pd atoms to form distorted PdV4Pd8 cuboctahedra that share corners with four equivalent PdV4Pd8 cuboctahedra, corners with eight equivalent VPd12 cuboctahedra, edges with twenty-four PdV4Pd8 cuboctahedra, faces with six equivalent VPd12 cuboctahedra, and faces with twelve PdV4Pd8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VPd3 by Materials Project

Pd3V is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. V is bonded to twelve equivalent Pd atoms to form VPd12 cuboctahedra that share corners with six equivalent VPd12 cuboctahedra, corners with twelve equivalent PdV4Pd8 cuboctahedra, edges with eighteen equivalent PdV4Pd8 cuboctahedra, faces with eight equivalent VPd12 cuboctahedra, and faces with twelve equivalent PdV4Pd8 cuboctahedra. There are six shorter (2.74 Å) and six longer (2.76 Å) V–Pd bond lengths. Pd is bonded to four equivalent V and eight equivalent Pd atoms to form distorted PdV4Pd8 cuboctahedra that share corners with four equivalent VPd12 cuboctahedra, corners with fourteen equivalent PdV4Pd8 cuboctahedra, edges with six equivalent VPd12 cuboctahedra, edges with twelve equivalent PdV4Pd8 cuboctahedra, faces with four equivalent VPd12 cuboctahedra, and faces with sixteen equivalent PdV4Pd8 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.72–2.81 Å.

36 MATERIALS SCIENCE↗