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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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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Improvement of Photovoltaic Performance of Polymer Solar Cells by Rational Molecular Optimization of Organic Molecule Acceptors

Abstract Two n‐type organic semiconductor (n‐OS) small molecules m ‐ITIC‐2F and m ‐ITIC‐4F with fluorinated 2‐(2,3‐dihydro‐3‐oxo‐1H‐inden‐1‐ylidene)propanedinitrile (IC) terminal moieties are prepared, for the application as an acceptor in polymer solar cells (PSCs), to further improve the photovoltaic performance of the n‐OS acceptor 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene) indanone) ‐5,5,11,11‐tetrakis(3‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐sindaceno[1,2‐b:5,6‐b′]‐dithiophene ( m ‐ITIC). Compared to m ‐ITIC, these two new acceptors show redshifted absorption, higher molecular packing order, and improved electron mobilities. The power conversion efficiencies (PCE) of the as‐cast PSCs with m ‐ITIC‐2F or m ‐ITIC‐4F as an acceptor and a low‐cost donor–acceptor (D–A) copolymer PTQ10 as a donor reach 11.57% and 11.64%, respectively, which are among the highest efficiency for the as‐cast PSCs so far. Furthermore, after thermal annealing treatment, improved molecular packing and enhanced phase separation are observed, and the higher PCE of 12.53% is achieved for both PSCs based on the two acceptors. The respective and unique advantage with the intrinsic high degree of order, molecular packing, and electron mobilities of these two acceptors will be suitable to match with different p‐type organic semiconductor donors for higher PCE values, which provide a great potential for the PSCs commercialization in the near future. These results indicate that rational molecular structure optimization is of great importance to further improve photovoltaic properties of the photovoltaic materials.

Li, Xiaojun↗
DOE OSTI2023

Density functional modeling of the binding energies between aluminosilicate oligomers and different metal cations

Interactions between negatively charged aluminosilicate species and positively charged metal cations are critical to many important engineering processes and applications, including sustainable cements and aluminosilicate glasses. In an effort to probe these interactions, here we have calculated the pair-wise interaction energies (i.e., binding energies) between aluminosilicate dimer/trimer and 17 different metal cations M n+ (M n+ = Li + , Na + , K + , Cu + , Cu 2+ , Co 2+ , Zn 2+ , Ni 2+ , Mg 2+ , Ca 2+ , Ti 2+ , Fe 2+ , Fe 3+ , Co 3+ , Cr 3+ , Ti 4+ and Cr 6+ ) using a density functional theory (DFT) approach. Analysis of the DFT-optimized structural representations for the clusters (dimer/trimer + M n+ ) shows that their structural attributes (e.g., interatomic distances) are generally consistent with literature observations on aluminosilicate glasses. The DFT-derived binding energies are seen to vary considerably depending on the type of cations (i.e., charge and ionic radii) and aluminosilicate species (i.e., dimer or trimer). A survey of the literature reveals that the difference in the calculated binding energies between different M n+ can be used to explain many literature observations associated with the impact of metal cations on materials properties (e.g., glass corrosion, mineral dissolution, and ionic transport). Analysis of all the DFT-derived binding energies reveals that the correlation between these energy values and the ionic potential and field strength of the metal cations are well captured by 2nd order polynomial functions ( R 2 values of 0.99–1.00 are achieved for regressions). Given that the ionic potential and field strength of a given metal cation can be readily estimated using well-tabulated ionic radii available in the literature, these simple polynomial functions would enable rapid estimation of the binding energies of a much wider range of cations with the aluminosilicate dimer/trimer, providing guidance on the design and optimization of sustainable cements and aluminosilicate glasses and their associated applications. Finally, the limitations associated with using these simple model systems to model complex interactions are also discussed.

Gong, Kai↗
DOE OSTI2022

Spectroscopic evidence of highly correlated electrons in $\mathrm{VSe_2}$

We present detailed high-resolution angle-resolved photoemission experiments on $\mathrm{VSe_2}$ grown under various conditions. The surface electronic structure optimally grown samples can host high-temperature spectral kink, quasiparticle peak, and the Fermi gap. Collective observation of these electronic features refers to the strong electronic correlation and is usually attributed to the characteristics of superconductors. Temperature evolution of the quasiparticle peak and the Fermi gap also follow the trend observed in high-$T_c$ superconductors as progressive quenching of the quasiparticle peak at a lower temperature than the complete Fermi gap closing. As a result, the quasiparticle peak can be observed up to 100 ± 5 K while the Fermi gap persists up to ~ 150 K. Importantly, these realizations can guide future studies to induce high-temperature superconductivity in transition metal dichalcogenides as well as understand the physics behind high-$T_c$ superconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Concurrent Enhancement of Acetylene Uptake Capacity and Selectivity by Progressive Core Expansion and Extra–Framework Anions in Pore–Space–Partitioned Metal–Organic Frameworks

A multi-stage core-expansion method is proposed here as one component of the integrative binding-site/extender/core-expansion (BEC) strategy. The conceptual deconstruction of the partitioning ligand into three editable parts draws our focus onto progressive core expansion and allows the optimization of both acetylene uptake and selectivity. Herein the effectiveness of this strategy is shown through a family of eight cationic pore-partitioned materials containing three different partitioning ligands and various counter anions. The optimized structure, Co 3 -cpt-tph-Cl (Hcpt=4-(p-carboxyphenyl)-1,2,4-triazole, H-tph=(2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene) with the largest surface area and highest C 2 H 2 uptake capacity (200 cm 3 /g at 298 K), also exhibits (desirably) the lowest CO 2 uptake and hence the highest C 2 H 2 /CO 2 selectivity. The successful boost in both C 2 H 2 capacity and IAST selectivity allows Co 3 -cpt-tph-Cl to rank among the best crystalline porous materials, ionic MOFs in particular, for C 2 H 2 uptake and C 2 H 2 /CO 2 experimental breakthrough separation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Construction of the Bioconjugate Py‐Macrodipa‐PSMA and Its In Vivo Investigations with Large 132/135 La 3+ and Small 47 Sc 3+ Radiometal Ions

To harness radiometals in clinical settings, a chelator forming a stable complex with the metal of interest and targets the desired pathological site is needed. Toward this goal, we previously reported a unique set of chelators that can stably bind to both large and small metal ions, via a conformational switch. Within this chelator class, py-macrodipa is particularly promising based on its ability to stably bind several medicinally valuable radiometals including large 132/135 La 3+ , 213 Bi 3+ , and small 44 Sc 3+ . Here, in this study, we report a 10-step organic synthesis of its bifunctional analogue py-macrodipa-NCS, which contains an amine-reactive −NCS group that is amenable for bioconjugation reactions to targeting vectors. The hydrolytic stability of py-macordipa-NCS was assessed, revealing a half-life of 6.0 d in pH 9.0 aqueous buffer. This bifunctional chelator was then conjugated to a prostate-specific membrane antigen (PSMA)-binding moiety, yielding the bioconjugate py-macrodipa-PSMA, which was subsequently radiolabeled with large 132/135 La 3+ and small 47 Sc 3+ , revealing efficient and quantitative complex formation. The resulting radiocomplexes were injected into mice bearing both PSMA-expressing and PSMA-non-expressing tumor xenografts to determine their biodistribution patterns, revealing delivery of both 132/135 La 3+ and 47 Sc 3+ to PSMA+ tumor sites. However, partial radiometal dissociation was observed, suggesting that py-macrodipa-PSMA needs further structural optimization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Synthesis and in silico and in vitro evaluation of trimethoxy-benzamides designed as anti-prion derivatives

Transmissible spongiform encephalopathies (TSEs), also known as prion diseases, are neurodegenerative disorders which affect mammals, including the human species, and arise after the conversion of the monomeric cellular prion protein (PrP{sup C}) into the aggregated scrapie form (PrP{sup Sc}). There is no therapy to treat TSEs and the identification of compounds that bind PrP{sup C}, preventing its conversion into PrP{sup Sc}, is a viable therapeutic strategy. We designed and synthesized six novel trimethoxy-benzamide compounds as anti-prion drug candidates. Molecular docking analyses predicted that all the derivatives bind to a hotspot region located in the PrP globular domain with very similar spatial orientation and interaction mode. Although none of the analogs inhibited in vitro-aggregation of recombinant PrP (rPrP) in a cell-free conversion assay, the RT-QuIC, compound 8a accelerated rPrP conversion into PrP{sup Sc}-like species. STD-NMR and ITC analyses indicated that both 8a and 8b bind to rPrP{sup 90–231}. These analogs were toxic to PrP{sup Sc}-infected cell lines, hence we could not assess their anti-prion activity by using this cellular approach, although this toxicity was cell line-dependent. These results point out that the 4-amino-quinoline trimethoxy-benzamide scaffold described herein represents a novel chemical pattern useful as a starting point for future structural optimization in the design of PrP ligands with improved affinity and safety profiles.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Effective data sampling strategies and boundary condition constraints of physics-informed neural networks for identifying material properties in solid mechanics

Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions. However, material identification is a challenging task, especially when the characteristic of the material is highly nonlinear in nature, as is common in biological tissue. In this work, we identify unknown material properties in continuum solid mechanics via physics-informed neural networks (PINNs). To improve the accuracy and efficiency of PINNs, we develop efficient strategies to nonuniformly sample observational data. We also investigate different approaches to enforce Dirichlet-type boundary conditions (BCs) as soft or hard constraints. Finally, we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space. The estimated material parameters achieve relative errors of less than 1%. As such, this work is relevant to diverse applications, including optimizing structural integrity and developing novel materials.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

FT-IR, Raman, and NMR Spectroscopy and DFT Theory of Glimepiride Molecule as a Sulfonylurea Compound

The glimepiride molecule was experimentally characterized using vibrational (FT-IR and laser-Raman) and NMR chemical shift spectroscopy. The molecule optimized structure, vibrational wavenumbers, and {sup 1}H and {sup 13}C NMR isotropic chemical shifts were theoretically obtained with the DFT/B3LYP method at a 6-311++G(d,p) basis set. The theoretical geometric parameters, vibrational wavenumbers, and NMR chemical shifts were found to be consistent with experimental data and similar spectral results in the literature.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Experimental Study and Fractal Analysis on the Anisotropic Performance of Explosively Welded Interfaces of 304 Stainless Steel/245 Carbon Steel

The mechanical anisotropy of an explosive welding composite plate made of 304 stainless steel/245 steel was studied through shear experiments performed on explosively welded wavy interfaces along several orientation angles. The results indicated that the strength and the fracture energy of samples significantly varied with the orientation angles. The fracture surfaces of all samples were observed using a scanning electron microscope and through three-dimensional structure microscopy. The periodic features of all the fracture surfaces were clearly shown in different fracture modes. The fractal dimension of the fracture surfaces was calculated based on the fractal geometry by the box-counting method in MATLAB. The cohesive element model was used to analyze the fracture energy according to the physical dependence of the fractal dimension on thermodynamic entropy and interface separation energy. The fracture energy was an exponential function of the fractal dimension value, which was in good agreement with the experimental results. All results were validated for effective use in the application of anisotropy analysis to the welded interface and structural optimization of explosively welded composite plates.

36 MATERIALS SCIENCE↗
DOE OSTI2018

An Improved Sub-component Fatigue Testing Method for Material Characterization

In this paper an improved sub-component fatigue testing method is proposed, in which structural optimization is used to obtain specimens in which fatigue failure is precipitated in the designated area away from the boundaries, i.e., load application and fixture points. This is achieved by optimizing the nonlinear beam taper and the dynamic excitation. The major requirement for accurate material characterization through sub-component tests concerns unbiased stress states in the gauge section. However, empiricism shows that many sub-component high-cycle fatigue testing methods suffer from failure in the boundaries rather than the gauge section, which causes bias. The common practice for reinforcing those regions only shifts the issue into new areas of local discontinuities where failure is still caused remotely from the gauge section. An experimental proof of concept demonstrates that optimization of the beam taper can be used to obtain unbiased fatigue test data.

42 ENGINEERING↗
DOE OSTI2022

Matrimid substrates with bicontinuous surface and macrovoids in the bulk: A nearly ideal substrate for composite membranes in CO 2 capture

Scalable fabrication of thin-film composite (TFC) membrane for post-combustion carbon capture is often limited by the availability of high-performance nanoporous substrate. Ideally, the substrate should allow for fast gas transport at the selective layer/substrate interface as well as in the bulk of the substrate. In this study, highly permeable Matrimid substrates were prepared via vapor- and nonsolvent-induced phase separations. The phase separation mechanism of the Matrimid®/N-methyl-2-pyrrolidone casting solution was modulated by the addition of LiCl to control the solution thermodynamic stability, and nanoporous Matrimid substrates were formed with a bicontinuous surface and macrovoids in the bulk. This hierarchically optimized structure resulted in a CO 2 permeance of 2.60 × 10 5 GPU (1 GPU = 1 × 10 –6 cm 3 (STP) cm –2 s –1 cmHg –1 = 3.349 × 10 –10 mol m –2 s –1 Pa –1 ), which was ca. 11 times more permeable than a benchmark polyethersulfone substrate with cellular pores. The benefit of using this new substrate was demonstrated by coating a 170-nm amine-containing polymer to form a TFC facilitated transport membrane. The membrane exhibited a CO 2 permeance of 932 GPU at 57°C, which was 72 GPU higher than the counterpart coated on the benchmark substrate. Meanwhile, the CO 2 /N 2 selectivity was remained at 158. This permeance improvement could be well explained by the resistance-in-series model, where the improved permeance was attributed to the reductions in substrate and lateral diffusion mass transfer resistances. The upper bound (UB) analysis indicates that the Matrimid substrate is nearly ideal for the state-of-the-art polymers for CO 2 /N 2 separation. Here, the substrate improvement could also reduce the parasitic energy associated with the membrane process due to the reduced membrane cost and flue gas compression requirement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Enhancing durability and activity toward oxygen evolution reaction using single-site Re-doped NiFeO x catalysts at ampere-level

NiFeO x materials are known as among the most active catalysts toward oxygen evolution reaction (OER) for hydrogen generation in alkaline media. Nevertheless, the long-term durability of NiFeO x catalysts for OER is still too far to the industrial application. Herein, we prepared a NiFeReO x catalyst with single-site Re dopants and observed that the single-site Re dopants could significantly enhance the durability without compromising the activity. A cell voltage of 1.82 V without iR correction is noted at the current density of 3000 mA cm –2 in anion-exchange membrane water electrolyzer (AEMWE) with NiFeReO x catalyst, and a very small degradation is observed under 2000 and 1000 mA cm –2 , which remarkably outperforms the pristine NiFeO x . Additionally, the overpotential of 305 mV at 10 mA cm –2 is achieved with the NiFeReO x catalyst, which is lower than 50 mV compared with the pristine NiFeO x catalyst, together with a smaller Tafel slope of 54.3 mV dec -1 . The boosted OER durability and activity of the NiFeReO x catalyst could be attributed to the strong electron-withdrawing property of Re 7+ single atoms leading to the electronic structure optimization and stabilization of Ni/Fe active sites. Our insights propose a new path for designing NiFeO x catalysts with high durability and activity toward OER.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

express: Extensible, high-level workflows for swifter ab initio materials modeling

In this work, we introduce an open-source Julia project, express, an extensible, lightweight, high-throughput, high-level workflow framework that aims to automate ab initio calculations for the materials science community. express is shipped with well-tested workflow templates, including structure optimization, equation of state (EOS) fitting, phonon spectrum (lattice dynamics) calculation, and thermodynamic property calculation in the framework of the quasi-harmonic approximation (QHA). It is designed to be highly modularized so that its components can be reused across various occasions, and customized workflows can be built on top of that. Users can also track the status of workflows in real-time, and rerun failed jobs thanks to the data lineage feature express provides. Finally, two working examples, i.e., all workflows applied to lime and akimotoite, are also presented in the code and this paper.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Oxidation state and coordination environment of Pb in U-bearing minerals

This study examines the oxidation and coordination of lead (Pb) in the uranium (U) minerals uraninite (UO 2 ), coffinite (USiO 4 ), and brannerite (UTi 2 O 6 ), and minerals that have U as a minor constituent, zircon (ZrSiO 4 ) and titanite (CaTiSiO 5 ). The characterization of Pb was conducted through a combination of micro-synchrotron X-ray fluorescence mapping (µSXRF) and micro-X-ray absorption spectroscopy (µXAS), collected at the Pb L II and L III edge on characterized grains (electron microscopy and X-ray diffraction) from a range of geological settings and ages. For all minerals considered in this study, Pb L II and L III X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicate that Pb exists as Pb 2+ . In the case of uraninite, DFT structure optimization calculations suggest that the substitution of Pb 2+ for U 4+ is facilitated by the stereochemically active electron lone pair indicative of Pb 2+ , which effectively takes the place of an oxygen vacancy (coupled substitution Pb 2+ + = U 4+ + O 2- ). In detail, however, the EXAFS and XANES data, supported by first principle calculations of the XANES associated with Pb 2+ replacing U 4+ in the crystal lattice of uraninite, indicate that Pb 2+ is present in a less distorted coordination than suggested by DFT, which may reflect a yet to be characterized link between interstitial oxygen defects and Pb 2+ incorporation, rather than a simple oxygen vacancy. For coffinite, the XANES data demonstrate that Pb exists mainly as Pb 2+ in the form of galena, indicating limited stability of the isomorphous substitution in coffinite. In contrast, Pb is homogeneously distributed in the metamict mineral brannerite, which displays a distinct XANES spectrum suggestive of Pb 2+ bonded to oxygens in a highly distorted coordination environment. Pb L II XANES indicate that radiogenic Pb exists predominantly as Pb 2+ within the crystal lattice of zircon and as distinct mineral PbO nano-scale inclusions or domains. Additionally, Pb L II XANES measurements also indicate that Pb 2+ exists within titanite although the coordination environment is unclear. Overall, these data suggest that the previous indications of the presence of Pb 4+ in radioactive minerals need to be reconsidered. The nature of radiogenic Pb 2+ incorporation in U-bearing minerals controls the mobilization of Pb in hydrothermal fluids and the utility of a mineral as a geochronometer. The Pb valence and coordination data presented in this study provide fundamental constraints imperative for our understanding of the controls governing the mobilization of radiogenic Pb during water-rock interaction and metamorphism.

58 GEOSCIENCES↗
DOE OSTI2024

Magnetism and finite-temperature effects in UZr 2 : A density functional theory analysis

The structure and the thermophysical properties of d-UZr 2 are investigated using 0 K density functional theory and ab initio molecular dynamics (AIMD). Modeling the true paramagnetic state of this intermetallic compound has been challenging using first-principles calculations. For the first time, we find that the generalized gradient approximation method without applying an on-site Coulomb interaction term (Hubbard U) can result in a ground state that is antiferromagnetic (AFM). We believe that this weak AFM ground state is the closest to the real paramagnetic state. We found that structure optimization at finite temperatures using AIMD is necessary to achieve this ground state instead of the non-magnetic and ferromagnetic states previously reported in the literature. Our findings indicate that applying the Hubbard U on uranium f-orbitals in this metallic system is unnecessary and not recommended, as it leads to a large overestimation of the volume and introduces an unphysical strong spin polarization. Finally, our approach results in atomic volume, thermal expansion, and heat capacities that have strong agreement with experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Reinforcing cycling stability and rate capability of LiNi0.5Mn1.5O4 cathode by dual-modification of coating and doping of a fast-ion conductor

Highlights: • Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} with well-defined octahedral morphology have been controllably obtained. • The combination of the modification of fast ions conductor and solid state method will be an optional method. • The cyclic performance and rate capability of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4}-based materials have been significantly improved. - Abstract: A simple solid state method was utilized to synthesize excellent spinel Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathodes. Dual-modification of coating and doping of fast-ion conductor Li{sub 2}SiO{sub 3} leads to stable crystal structure and additional three-dimensional (3-D) channels for Li{sup +}-ion diffusion, and protects the electrode surface from electrolyte attack. The Li{sub 2}SiO{sub 3}-modified material possesses coexistence of ordered P4{sub 3}32 and disordered Fd-3m phases. As a result of improved structure, morphology and conductivity, the Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} shows more superior cyclic performance, rate capability and high temperature stability than the pristine: capacity retention of 95.17% at 0.1 C after 100 cycles vs. that of 79.23%; rate capability of 130–89.1 mAh g{sup −1} at 0.1–10 C vs. that of 120–57.6 mAh g{sup −1}; and high temperature capacity retention of 99.42% at 0.1 C vs. that of 79.59%. Our study provides a facile approach to stabilize crystal structure, optimize morphology and conductivity, and thus enhance electrochemical performance of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4}-based materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗