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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Indications of flat bands driving the δ to α volume collapse of plutonium

On cooling from the melt, plutonium (Pu) undergoes a series of structural transformations accompanied by a ≈ 28% reduction in volume from its δ phase to its α phase at low temperatures. While Pu’s partially filled 5 f -electron shells are known to be involved, their precise role in the transformations has remained unclear. By using calorimetry measurements on α -Pu and gallium-stabilized δ -Pu combined with resonant ultrasound and X-ray scattering data to account for the anomalously large softening of the lattice with temperature, we show here that the difference in electronic entropy between the α and δ phases dominates over the difference in phonon entropy. Rather than finding an electronic specific heat characteristic of broad f -electron bands in α -Pu, as might be expected to occur within a Kondo collapsed phase in analogy with cerium, we find it to be indicative of flatter subbands. An important role played by Pu’s 5 f electrons in the formation of its larger unit cell α phase comprising inequivalent lattice sites and varying bond lengths is therefore suggested.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Plutonium Retention by Crystalline Silicotitanate under Hyperalkaline Conditions Relevant to Tank-Side Cesium-Removal at the Hanford Site

Crystalline silicotitanate (CST) is used in Hanford’s Tank-Side Cesium-Removal (TSCR) process to selectively remove Cs-137 from highly caustic, nitrate-rich tank supernatants. Recent testing with actual waste samples suggests that CST can also retain measurable plutonium (Pu), which could affect radiological classification and disposal pathways for spent CST. To quantify this behavior, Pu partitioning to CST was studied under Hanford-relevant conditions using batch-contact experiments in a representative simulant (2 M NaNO3, 0.7 M NaOH). Isotherm data were measured and distribution ratios calculated, with Cs+ uptake used as benchmark. Under low-carbonate conditions, Pu was retained strongly by CST in systems initially contacted with either PuO2 nanoparticles (Pu(IV)) or aqueous Pu(VI), with distribution ratios of ~2,200–3,700 mL/g, generally exceeding those for Cs+ (~400–1,000 mL/g). Increasing carbonate concentration strongly reduced PuO2 nanoparticle retention; at [Na2CO3] = 1 M, distribution ratios decreased by up to one order of magnitude to roughly 100–300 mL/g. Electron microscopy suggests that Pu retention involves a combination of mechanisms such as PuO2 NP aggregation induced by CST leachate components, and association with CST bead surfaces.

Neumann, J.↗
DOE OSTI2024

Indications of flat bands driving the δ to α volume collapse of plutonium

On cooling from the melt, plutonium (Pu) undergoes a series of structural transformations accompanied by a ≈ 28% reduction in volume from its δ phase to its α phase at low temperatures. While Pu’s partially filled 5f -electron shells are known to be involved, their precise role in the transformations has remained unclear. By using calorimetry measurements on α-Pu and gallium-stabilized δ-Pu combined with resonant ultrasound and X-ray scattering data to account for the anomalously large softening of the lattice with temperature, we show here that the difference in electronic entropy between the α and δ phases dominates over the difference in phonon entropy. Rather than finding an electronic specific heat characteristic of broad $f$-electron bands in α-Pu, as might be expected to occur within a Kondo collapsed phase in analogy with cerium, we find it to be indicative of flatter subbands. An important role played by Pu’s 5$f$ electrons in the formation of its larger unit cell α phase comprising inequivalent lattice sites and varying bond lengths is therefore suggested.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Green Biodegradation: Analysis of Potential Polyurethane-degrading Enzymes and Their Secretion in Chlamydomonas reinhardtii

Plastic pollution is a critical global issue, with only 5% of plastics currently recycled. Polyester polyurethane (PU), a widely used plastic, can potentially be broken down using enzymatic biodegradation rather than mechanical processing that generates microplastics. This study focuses on PS5, a potential PU-degrading enzyme with esterase activity, capable of cleaving ester bonds found in PU structures. Researchers investigated the expression and secretion of PS5 in the green microalga Chlamydomonas reinhardtii, a sustainable production platform capable of generating PU precursors such as lipids and diacids while sequestering carbon. Experiments demonstrated that PS5 significantly outperformed commercial lipase in cleaving the FDA substrate, indicating high esterase activity. Algal transformants expressing PS5 also showed halo formation on Impranil®-agar plates, suggesting PU dispersion degradation. These findings highlight C. reinhardtii as a viable chassis for the production and secretion of plastic-degrading enzymes, offering a sustainable route to both upcycle and degrade PU products at the end of their lifecycle.

Diaz, Crisandra Jade↗
DOE OSTI2025

Bio-Based Polyurethane Materials: Technical, Environmental, and Economic Insights

Polyurethane (PU) is widely used due to its attractive properties, but the shift to a low-carbon economy necessitates alternative, renewable feedstocks for its production. This review examines the synthesis, properties, and sustainability of bio-based PU materials, focusing on renewable resources such as lignin, vegetable oils, and polysaccharides. It discusses recent advances in bio-based polyols, their incorporation into PU formulations, and the use of bio-fillers like chitin and nanocellulose to improve mechanical, thermal, and biocompatibility properties. Despite promising material performance, challenges related to large-scale production, economic feasibility, and recycling technologies are highlighted. The paper also reviews life cycle assessment (LCA) studies, revealing the complex and context-dependent environmental benefits of bio-based PU materials. These studies indicate that while bio-based PU materials generally reduce greenhouse gas emissions and non-renewable energy use, their environmental performance varies depending on feedstock and formulation. The paper identifies key areas for future research, including improving biorefinery processes, optimizing crosslinker performance, and advancing recycling methods to unlock the full environmental and economic potential of bio-based PU in commercial applications.

Jayalath, Piumi↗
DOE OSTI2020

Materials Data on Pu3Pd4 by Materials Project

Pu3Pd4 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Pu is bonded in a 9-coordinate geometry to nine Pd atoms. There are a spread of Pu–Pd bond distances ranging from 2.90–3.30 Å. There are three inequivalent Pd sites. In the first Pd site, Pd is bonded in a 6-coordinate geometry to six equivalent Pu atoms. In the second Pd site, Pd is bonded in a 6-coordinate geometry to six equivalent Pu atoms. In the third Pd site, Pd is bonded in a 10-coordinate geometry to seven equivalent Pu and three equivalent Pd atoms. There are one shorter (2.87 Å) and two longer (3.02 Å) Pd–Pd bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2InPd2 by Materials Project

Pu2Pd2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent In atoms. There are two shorter (2.84 Å) and four longer (2.99 Å) Pu–Pd bond lengths. All Pu–In bond lengths are 3.41 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Pu, one Pd, and two equivalent In atoms. The Pd–Pd bond length is 2.88 Å. Both Pd–In bond lengths are 3.01 Å. In is bonded to eight equivalent Pu and four equivalent Pd atoms to form a mixture of face and corner-sharing InPu8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2SnPt2 by Materials Project

Pu2Pt2Sn crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Pt and four equivalent Sn atoms. There are two shorter (2.82 Å) and four longer (2.97 Å) Pu–Pt bond lengths. All Pu–Sn bond lengths are 3.39 Å. Pt is bonded in a 6-coordinate geometry to six equivalent Pu, one Pt, and two equivalent Sn atoms. The Pt–Pt bond length is 2.86 Å. Both Pt–Sn bond lengths are 3.01 Å. Sn is bonded to eight equivalent Pu and four equivalent Pt atoms to form a mixture of face and corner-sharing SnPu8Pt4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGa4 by Materials Project

PuGa4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Pu is bonded in a 11-coordinate geometry to thirteen Ga atoms. There are a spread of Pu–Ga bond distances ranging from 2.97–3.13 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 9-coordinate geometry to three equivalent Pu and six Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.58–2.91 Å. In the second Ga site, Ga is bonded to four equivalent Pu and eight Ga atoms to form a mixture of distorted edge, face, and corner-sharing GaPu4Ga8 cuboctahedra. There are four shorter (3.02 Å) and two longer (3.06 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 3-coordinate geometry to three equivalent Pu and eight Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2InRh2 by Materials Project

Pu2Rh2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Rh and four equivalent In atoms. There are two shorter (2.81 Å) and four longer (2.97 Å) Pu–Rh bond lengths. All Pu–In bond lengths are 3.38 Å. Rh is bonded in a 8-coordinate geometry to six equivalent Pu and two equivalent In atoms. Both Rh–In bond lengths are 2.92 Å. In is bonded to eight equivalent Pu and four equivalent Rh atoms to form a mixture of distorted face and corner-sharing InPu8Rh4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2SnPd2 by Materials Project

Pu2Pd2Sn crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent Sn atoms. There are two shorter (2.83 Å) and four longer (3.01 Å) Pu–Pd bond lengths. All Pu–Sn bond lengths are 3.39 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Pu, one Pd, and two equivalent Sn atoms. The Pd–Pd bond length is 2.78 Å. Both Pd–Sn bond lengths are 2.97 Å. Sn is bonded to eight equivalent Pu and four equivalent Pd atoms to form a mixture of face and corner-sharing SnPu8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2Ni2Sn by Materials Project

Pu2Ni2Sn crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 10-coordinate geometry to six equivalent Ni and four equivalent Sn atoms. There are two shorter (2.82 Å) and four longer (2.90 Å) Pu–Ni bond lengths. All Pu–Sn bond lengths are 3.27 Å. Ni is bonded in a 9-coordinate geometry to six equivalent Pu, one Ni, and two equivalent Sn atoms. The Ni–Ni bond length is 2.48 Å. Both Ni–Sn bond lengths are 2.82 Å. Sn is bonded to eight equivalent Pu and four equivalent Ni atoms to form a mixture of corner and face-sharing SnPu8Ni4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2InNi2 by Materials Project

Pu2Ni2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Ni and four equivalent In atoms. There are two shorter (2.72 Å) and four longer (2.80 Å) Pu–Ni bond lengths. All Pu–In bond lengths are 3.24 Å. Ni is bonded in a 6-coordinate geometry to six equivalent Pu, one Ni, and two equivalent In atoms. The Ni–Ni bond length is 2.75 Å. Both Ni–In bond lengths are 2.86 Å. In is bonded to eight equivalent Pu and four equivalent Ni atoms to form a mixture of distorted corner and face-sharing InPu8Ni4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2InPt2 by Materials Project

Pu2Pt2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to six equivalent Pt and four equivalent In atoms. There are two shorter (2.91 Å) and four longer (3.05 Å) Pu–Pt bond lengths. All Pu–In bond lengths are 3.49 Å. Pt is bonded in a 9-coordinate geometry to six equivalent Pu and two equivalent In atoms. Both Pt–In bond lengths are 3.09 Å. In is bonded to eight equivalent Pu and four equivalent Pt atoms to form a mixture of face and corner-sharing InPu8Pt4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuBiPd2 by Materials Project

PuPd2Bi is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a body-centered cubic geometry to eight equivalent Pd and six equivalent Bi atoms. All Pu–Pd bond lengths are 3.00 Å. All Pu–Bi bond lengths are 3.46 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Pu and four equivalent Bi atoms. All Pd–Bi bond lengths are 3.00 Å. Bi is bonded in a distorted body-centered cubic geometry to six equivalent Pu and eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuSbPd2 by Materials Project

PuPd2Sb is Heusler structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Pu is bonded in a distorted body-centered cubic geometry to eight equivalent Pd and six equivalent Sb atoms. There are four shorter (2.95 Å) and four longer (2.96 Å) Pu–Pd bond lengths. There are four shorter (3.41 Å) and two longer (3.42 Å) Pu–Sb bond lengths. Pd is bonded in a body-centered cubic geometry to four equivalent Pu and four equivalent Sb atoms. There are two shorter (2.95 Å) and two longer (2.96 Å) Pd–Sb bond lengths. Sb is bonded in a 8-coordinate geometry to six equivalent Pu and eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2HgBi by Materials Project

Pu2HgBi is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a body-centered cubic geometry to four equivalent Hg and four equivalent Bi atoms. All Pu–Hg bond lengths are 3.32 Å. All Pu–Bi bond lengths are 3.32 Å. Hg is bonded in a body-centered cubic geometry to eight equivalent Pu atoms. Bi is bonded in a body-centered cubic geometry to eight equivalent Pu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2BiAu by Materials Project

Pu2AuBi is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a body-centered cubic geometry to four equivalent Au and four equivalent Bi atoms. All Pu–Au bond lengths are 3.28 Å. All Pu–Bi bond lengths are 3.28 Å. Au is bonded in a body-centered cubic geometry to eight equivalent Pu atoms. Bi is bonded in a body-centered cubic geometry to eight equivalent Pu atoms.

36 MATERIALS SCIENCE↗