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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Concavity-based local erosion and sphere-size-based local dilation applied to lithium-ion battery electrode microstructures for particle identification

Performance metrics of lithium-ion batteries can be extracted from the analysis of electrode microstructures nanoscale imaging. The characterization workflow can involve a challenging particle identification, or instance segmentation, step. In this work, we propose a new identification method based on an original transformation: a sphere-size-based local dilation followed by a concavity-based local erosion, that is local morphology closing. The new transformation is much more efficient than the global morphology closing, with correct identification achieved with only 1.7 % dilation volume and 2.6 % erosion volume on a test geometry, compared to 39.2 % and more than 50 %, respectively, with its global counterpart. The new method has been then benchmarked versus other identification algorithms (watershed and pseudo coulomb repulsive field) on a real electrode microstructure with equal or better segmentation achieved.

25 ENERGY STORAGE↗
DOE OSTI2018

Hoberman-sphere-inspired lattice metamaterials with tunable negative thermal expansion

Materials with engineered thermal expansion coefficients, capable of avoiding failure or irreversible destruction of structures and devices, are important for aerospace, civil, biomedical, optics, and semiconductor applications. In natural materials, thermal expansion usually cannot be adjusted easily and a negative thermal expansion coefficient is still uncommon. Here we propose a novel architected lattice bi-material system, inspired by the Hoberman sphere, showing a wide range of tunable thermal expansion coefficient from negative to positive, -1.04 x 10 -3 degrees C-1 to 1.0 x 10 -5 degrees C-1. Numerical simulations and analytical formulations are implemented to quantify the evolution of the thermal expansion coefficients and reveal the underlying mechanisms responsible for this unusual behavior. We show that the thermal expansion coefficient of the proposed metamaterials depends on the thermal expansion coefficient ratio and the axial stiffness ratio of the constituent materials, as well as the bending stiffness and the topological arrangement of the constitutive elements. The finding reported here provides a new routine to design architected metamaterial systems with tunable negative thermal expansion for a wide range of potential applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nanocrystal programmable assembly beyond hard spheres (or shapes) and other (simple) potentials

Ligands are the key to almost any strategy in the assembly of programmable nanocrystals (or nanoparticles) and must be accurately considered in any predictive model. Hard Spheres (or Shapes) provide the simplest and yet quite successful approach to assembly, with remarkable sophisticated predictions verified in experiments. There are, however, many situations where hard spheres/shapes predictions fail. This prompts three important questions: In what situations should hard spheres/shapes models be expected to work? and when they do not work, Is there a general model that successfully corrects hard sphere/shape predictions? and given other successful models where ligands are included explicitly, and of course, numerical simulations, can we unify hard sphere/shape models, explicit ligand models and all atom simulations? . Further, the Orbifold Topological Model (OTM) provides a positive answer to these three questions. In this paper, I give a detailed review of OTM, describing the concept of ligand vortices and how it leads to spontaneous valence and nanoparticle “eigenshapes” while providing a prediction of the lattice structure, without fitting parameters, which accounts for many body effects not captured by (two-body) potentials. I present a thorough survey of experiments and simulations and show that, to this date, they are in full agreement with the OTM predictions. I conclude with a discussion on whether NC superlattices are equilibrium structures and some significant challenges in structure prediction.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Spheres of public conversation: Experiences in strategic environmental assessment

This paper draws on earlier research, a national review of Scottish SEA practice and a survey of practitioners and stakeholders engaged in SEA and spatial planning in one Scottish city-region, to explore claims being made in the academic literature for Strategic Environmental Assessment (SEA) as a tool for deliberative plan-making. We consider whether there is evidence that Scottish SEA practice is helping create more inclusive plan-making processes in light of recent legislative changes, thereby fulfilling one of the expectations of Scottish Government. The macro analysis found that although there are opportunities for stakeholders to engage in the Scottish SEA process the level in practice is extremely low, a finding which mirrors experience in England and elsewhere. The more detailed micro analysis reveals a more nuanced picture within the spatial planning system, however, suggesting the existence of two distinct spheres of public conversations, one characterised by active dialogue about the environmental effects of alternative strategies amongst public sector stakeholders and the other involving non-governmental stakeholders and community groups in a much more limited way. The paper concludes with a discussion of possible explanations for this outcome, concerning asymmetric incentive structures and the application of power, and a consideration of the implications in relation to the competing discourses of SEA. -- Highlights: • We examine the extent to which Scottish SEA is helping promote inclusive plan-making. • Low levels of stakeholder engagement generally in Scottish SEA. • Stronger SEA dialogue amongst public agencies than with the wider community. • Importance of incentive structures and power capture in framing SEA public conversations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Migration and accumulation of hydrous mantle incipient melt in the Earth's asthenosphere: Constraints from in-situ falling sphere viscometry measurements

The Earth's oceanic lithosphere-asthenosphere boundary (LAB) is marked by a notable decrease in seismic wave velocities and an increase in attenuation. This phenomenon is likely attributed to the accumulation of partial melt at the top of the asthenosphere. Nevertheless, the process involving the upward migration and aggregation of low-degree partial melts, highly likely to be mantle incipient melts in the asthenosphere, remains underexplored. Viscosity is a key factor controlling the flow of melts, thus in this study, we used In-situ X-ray falling sphere viscometry experiments to determine the viscosity of the mantle incipient melt containing 1.8–4.0 wt.% water at 1.5–6 GPa and 2100 K. We found that water and pressure can effectively decrease the viscosity of the mantle incipient melt. Therefore, the mantle incipient melts are highly mobile with a high segregation velocity in the deeper part of the asthenosphere. However, during ascent, their mobility diminishes due to an increase in viscosity and a decrease in water content. In conclusion, these mechanisms potentially contribute to the accumulation of partial melt at the top of the asthenosphere.

58 GEOSCIENCES↗
DOE OSTI2025

Additional considerations in analytical solution for time-dependent heat conduction in a three-dimensional multilayer sphere

This work presents an analytical method to solve the heat conduction equation in three dimensions for problems consisting of multilayer concentric spheres. The method can be used to treat time-varying heat conduction problems where the heat source that drives the transient is time-invariant. Equally applicable to all Poisson-type problems with concentric spherical geometry, the method consists of representing the solution as a summation of weighted eigenfunctions. The weights for each eigenfunction are computed algebraically. Previous work has already established the core constituents of the methodology. The current work augments the existing methods by including consideration of nonzero interface resistance between layers and explicit discussion on the boundary condition homogenization required to treat inhomogeneous problems. Also, two demonstration problems are presented. One demonstration problem is based on the method of manufactured solutions and therefore allows for comparison with exact expressions for the solution temperature distribution. The second, more complex, demonstration problem relies on the finite element method for comparisons. The expected convergence behavior is observed for both demonstration problems.

97 - MATHEMATICS AND COMPUTING↗
DOE OSTI2017

A Lagrangian particle method with remeshing for tracer transport on the sphere

A Lagrangian particle method (called LPM) based on the flow map is presented for tracer transport on the sphere. The particles carry tracer values and are located at the centers and vertices of triangular Lagrangian panels. Remeshing is applied to control particle disorder and two schemes are compared, one using direct tracer interpolation and another using inverse flow map interpolation with sampling of the initial tracer density. Test cases include a moving-vortices flow and reversing-deformational flow with both zero and nonzero divergence, as well as smooth and discontinuous tracers. We examine the accuracy of the computed tracer density and tracer integral, and preservation of nonlinear correlation in a pair of tracers. Here, we compare results obtained using LPM and the Lin–Rood finite-volume scheme. An adaptive particle/panel refinement scheme is demonstrated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Lithiophilic CoF 2 @C hollow spheres towards spatial lithium deposition for stable lithium metal batteries

Lithium metal (LM) is a promising anode for next-generation batteries due to its high theoretical capacity and low electrode potential. Nonetheless, side reactions, volume change, and unwanted lithium dendrite growth seriously limit the practical application of LM. Herein, with the aid of a hard template approach, a novel lithiophilic CoF 2 -carbon hollow sphere (CoF 2 @C-HS) composite material is successfully prepared via a facile in-situ fluorination and etching strategy. The lithiophilic CoF 2 acts as nucleation sites to reduce nucleation overpotential as well as induces the spatial Li deposition and the formation of LiF-rich solid electrolyte interphase (SEI), and the hollow carbon matrix can enhance the electrical conductivity and offer free space for LM deposition. Theoretical simulations reveal that the synergistic effect of lithiophilic CoF 2 and hollow carbon matrix homogenizes the electric field distribution and Li + flux. Benefiting from these advantages, the CoF 2 @C-HS-modified copper substrate electrode delivers an enhanced Coulombic efficiency (CE) of 93.7% for 280 cycles at 1 mA cm –2 and 1 mA h cm –2 . The symmetrical cell using CoF 2 @C-HS can stably cycle more than 1800 h with a low voltage hysteresis of 11 mV at a current density of 0.5 mA cm –2 and an areal capacity of 0.5 mA h cm –2 . Moreover, the Li@CoF 2 @C-HS composite anode enables more than 300 stable cycles at 1 C with a capacity retention of 95% in LiFePO 4 -based full cell and 110 stable cycles at 1 C in LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)-based high-voltage full cell. Finally, this work might shed a new light on designing lithiophilic hosts to spatially confine LM deposition, realizing dendrite-free LM anodes and the practical applications of LM batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Even spheres as joint spectra of matrix models

The Clifford spectrum is a form of joint spectrum for noncommuting matrices. This theory has been applied in photonics, condensed matter and string theory. In applications, the Clifford spectrum can be efficiently approximated using numerical methods, but this only is possible in low dimensional example. In this paper we examine the higher-dimensional spheres that can arise from theoretical examples. We also describe a constructive method to generate five real symmetric almost commuting matrices that have a K-theoretical obstruction to being close to commuting matrices. For this, we look to matrix models of topological electric circuits.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2012

Simple and low-temperature preparation of Co{sub 3}O{sub 4} sphere-like nanoparticles via solid-state thermolysis of the [Co(NH{sub 3}){sub 6}](NO{sub 3}){sub 3} complex

Highlights: ► [Co(NH{sub 3}){sub 6}](NO{sub 3}){sub 3} precursor was used for synthesizing pure Co{sub 3}O{sub 4} nanocrystals. ► Co{sub 3}O{sub 4} nanocrystals were synthesized at low temperature of 200 °C. ► Co{sub 3}O{sub 4} nanocrystals show a weak ferromagnetic behavior at room temperature. ► This simple method is low-cost and suitable for high-scale production of Co{sub 3}O{sub 4}. -- Abstract: In this work, spinel-type Co{sub 3}O{sub 4} spherical nanoparticles were easily prepared via decomposition of the hexamminecobalt(III) nitrate complex, [Co(NH{sub 3}){sub 6}](NO{sub 3}){sub 3}, at low temperature (200 °C). The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV–vis spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) specific surface area measurement and magnetic measurements. The results confirmed that pure single-phase Co{sub 3}O{sub 4} nanoparticles with weak ferromagnetic behavior were obtained by this method. TEM images showed that the Co{sub 3}O{sub 4} nanoparticles are sphere-like with an average diameter size of around 15 nm. The optical spectrum indicated two direct band gaps at 2.15 and 3.56 eV which are blue-shifted relative to reported values for the bulk sample. Using this fast and simple method, Co{sub 3}O{sub 4} nanoparticles can be produced without expensive and toxic solvents or complicated equipment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Flower-like and hollow sphere-like WO{sub 3} porous nanostructures: Selective synthesis and their photocatalysis property

Graphical abstract: -- Abstract: Nanoflake-based flower-like and hollow microsphere-like hydrated tungsten oxide architectures were selectively synthesized by acidic precipitation of sodium tungstate solution at mild temperature. Several techniques, such as X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermalgravimetric analysis, transmission electron microscopy, and Brunauer–Emmett–Teller N{sub 2} adsorption–desorption analyses, were used to characterize the structure and morphology of the products. The experimental results show that the nanoflake-based flower-like and hollow sphere-like WO{sub 3}·H{sub 2}O architectures can be obtained by changing the concentration of sodium tungstate solution. The possible formation process based on the aggregation–recrystallization mechanism is proposed. The corresponding tungsten oxide three-dimensional architectures were obtained after calcination at 450 °C. Finally, the obtained WO{sub 3} three-dimensional architectures were used as photocatalyst in the experiments. Compared with WO{sub 3} microflowers, the as-prepared WO{sub 3} hollow microspheres exhibit superior photocatalytic property on photocatalytic decomposition of Rhodamine B due to their hollow porous hierarchical structures.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Facile fabrication and characterization of amino-functionalized Fe{sub 3}O{sub 4} cluster@SiO{sub 2} core/shell nanocomposite spheres

Highlights: ► A method developed for the preparation of Fe{sub 3}O{sub 4} clusters@SiO{sub 2} nanocomposites. ► This method permits production of core/shell nanomaterials with high yields. ► Resultant superparamagnetic particles are monodisperse with high magnetizations. - Abstract: We developed a modified straightforward method for the fabrication of uniformly sized silica-coated magnetite clusters core/shell type nanocomposite particles. Proposed simple one-step processing method permits quick production of materials in high yield. The structural, surface, and magnetic characteristics of the nanocomposite particles were investigated by transmission electron microscopy (TEM), scanning electron microscope (SEM), powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Fourier-transform infrared (FTIR). The sphere-shaped particles almost have the average diameter of 120 nm, with a magnetic cluster core of 80 ± 15 nm, and a silica shell of 25 ± 10 nm thickness. The particles are superparamagnetic and present strong magnetization (18 emu/g) due to the fact that they possess core of the magnetic clusters. Subsequently, the silica surface of core/shell particles was amino-functionalized via N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (EDS). Findings of the present work highlight the potential for using amino-functionalized magnetic silica core/shell nanocomposite particles in biological applications since they possess useful magnetic properties and proper structure.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Facile preparation of sphere-like copper ferrite nanostructures and their enhanced visible-light-induced photocatalytic conversion of benzene

Graphical abstract: - Highlights: • Spinel CuFe{sub 2}O{sub 4} nanospheres were successfully synthesized via a facile method. • CuFe{sub 2}O{sub 4} nanospheres showed high photocatalytic activity toward benzene. • Ethyl acetate, carboxylic acid and aldehyde were the intermediate products. - Abstract: Spinel copper ferrite nanospheres with diameters of about 116 nm were synthesized in high yield via a facile solvothermal route. The prepared nanospheres had cubic spinel structure and exhibited good size uniformity and regularity. The band-gap energy of CuFe{sub 2}O{sub 4} nanospheres was calculated to be about 1.69 eV, indicating their potential visible-light-induced photocatalytic activity. The dramatically enhanced photocatalytic activity of the CuFe{sub 2}O{sub 4} nanospheres was evaluated via the photocatalytic conversion of benzene under Xe lamp irradiation. By using the in situ FTIR technique, ethyl acetate, carboxylic acid and aldehyde could be regarded as the intermediate products, and CO{sub 2} was produced as the final product during the reaction process. This study provided new insight into the design and preparation of functional nanomaterials with sphere structure in high yield, and the as-grown architectures demonstrated an excellent ability to remove organic pollutants in the atmosphere.

36 MATERIALS SCIENCE↗
DOE OSTI2013

One step synthesis of Bi@Bi{sub 2}O{sub 3}@carboxylate-rich carbon spheres with enhanced photocatalytic performance

Graphical abstract: Functional groups of sodium gluconate play synergetic roles in the formation of Bi@Bi{sub 2}O{sub 3}@carboxylate-rich carbon core–shell nanosturctures (Bi@Bi{sub 2}O{sub 3}@CRCSs). Bi@Bi{sub 2}O{sub 3}@CRCSs exhibits significant enhanced photocatalytic activity under visible light irradiation. - Highlights: • One step synthesis of Bi@Bi{sub 2}O{sub 3}@carboxylate-rich carbon spheres. • Functional groups of sodium gluconate play synergetic roles in the formation of Bi@Bi{sub 2}O{sub 3}@CRCSs. • Bi@Bi{sub 2}O{sub 3}@CRCSs exhibits enhanced photocatalytic activity under visible light irradiation. - Abstract: Bi@Bi{sub 2}O{sub 3}@carboxylate-rich carbon core-shell nanosturctures (Bi@Bi{sub 2}O{sub 3}@CRCSs) have been synthesized via a one-step method. The core–shell nanosturctures of the as-prepared samples were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Raman spectroscopy. The formation of Bi@Bi{sub 2}O{sub 3}@CRCSs core–shell nanosturctures should attribute to the synergetic roles of different functional groups of sodium gluconate. Bi@Bi{sub 2}O{sub 3}@CRCSs exhibits significant enhanced photocatalytic activity under visible light irradiation (λ > 420 nm) and shows an O{sub 2}-dependent feature. According to trapping experiments of radicals and holes, hydroxyl radicals were not the main active oxidative species in the photocatalytic degradation of MB, but O{sub 2}·{sup −} are the main active oxidative species.

36 MATERIALS SCIENCE↗
DOE OSTI2014

MnO{sub 2}@colloid carbon spheres nanocomposites with tunable interior architecture for supercapacitors

Graphical abstract: - Highlights: • MnO{sub 2}@CSs nanocomposites have been successfully synthesized in room temperature. • The composites exhibited three structures: core–shell, yolk–shell and hollow structure. • The yolk–shell structure exhibited a high specific capacitance and cycling stability. - Abstract: MnO{sub 2}@colloid carbon spheres nanocomposites with tunable interior architecture have been synthesized by a facile and cost-effective strategy at room temperature. The structure and morphology of as-prepared nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption, focused ion beam scanning electron microscopy (FIB/SEM) and high-resolution transmission electron microscopy (HRTEM). The as-obtained composites exhibited a three-dimensional architecture with core–shell, yolk–shell and hollow interior structure. Furthermore, the electrochemical properties of composites were evaluated by cycle voltammetric (CV) and galvanostatic charge–discharge measurements. The yolk–shell structure exhibited the optimized pseudocapacitance performance, revealing a specific capacitance (273 F g{sup −1}) with a good rate and cycling stability, owing to its unique structure and the poor crystallinity of MnO{sub 2} nanofilms. Therefore, this facile synthetic strategy could be useful to design and synthesis of tunable nanostructures with enhanced supercapacitor behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Synthesis of supported silver nano-spheres on zinc oxide nanorods for visible light photocatalytic applications

Highlights: • Synthesis of supported Ag NPs on ZnO nanorods using open vessel microwave reactor. • Use of the Ag/ZnO NPs as an efficient visible light photocatalyst. • Complete degradation of methylene blue in 1 h with 0.5 g/L Ag/ZnO NPs. - Abstract: We report the synthesis of silver (Ag) nano-spheres (NS) supported on zinc oxide (ZnO) nanorods through two step mechanism, using open vessel microwave reactor. Direct reduction of ZnO from zinc nitrates was followed by deposition precipitation of the silver on the ZnO nanorods. The supported Ag/ZnO nanoparticles were then characterized by electron microscopy, X-ray diffraction, FTIR, photoluminescence and UV–vis spectroscopy. The visible light photocatalytic activity of Ag/ZnO system was investigated using a test contaminant, methylene blue (MB). Almost complete removal of MB in about 60 min for doses higher than 0.5 g/L of the Ag/ZnO photocatalyst was achieved. This significant improvement in the photocatalytic efficiency of Ag/ZnO photocatalyst under visible light irradiation can be attributed to the presence of Ag nanoparticles on the ZnO nanoparticles which greatly enhances absorption in the visible range of solar spectrum enabled by surface plasmon resonance effect from Ag nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microporous and hollow carbon spheres derived from soft drinks: Promising CO 2 separation materials

In this work, we demonstrate that a simple hydrothermal treatment followed by pyrolysis of regular and diet soft drinks can generate well-defined carbon structures including solid and hollow spheres with a high degree of microporosity. These materials show high and selective CO 2 adsorption with a capacity up to 4.65 mmol g -1 at 0 °C and 1 bar depending on the particular soft drink used as the precursor. Isosteric heats of adsorption ranged from 22.3 kJ mol -1 to 29.2 kJ mol -1 which suggests a relatively low regeneration energy for ease of re-use. Carbon dioxide adsorption cycles were repeated for ten cycles with no loss of capacity confirming the reusability of the carbon. We also explore the effect of artificial sweeteners on the morphology and CO 2 interaction of the resulting carbon materials. These results show that waste soft drinks can be used to create high-value, porous carbon materials for applications such as carbon capture.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Li 2 S nano spheres anchored to single-layered graphene as a high-performance cathode material for lithium/sulfur cells

Fully lithiated lithium sulfide (Li 2 S) is a promising cathode material for Li/S cells due to its high theoretic capacity (1166 mA h g -1 ) and specific energy (2600 W h kg -1 ). However, low utilization of sulfur and poor rate capability still hinder the practical application of Li/S cells. In this paper, a carbon coated Li 2 S/graphene composite (Li 2 S/G@C) was developed by incorporating Li 2 S nano spheres with single-layered graphene and further forming a durable protective carbon layer on the surface of the Li 2 S particles using a facile CVD method. The high rate capability and remarkable cycle life of the Li 2 S/G@C cathode were demonstrated, which was mainly attributed to the unique structure of the Li 2 S/G@C that can significantly improve not only the electrical conductivity, but also the mechanical stability of the sulfur cathode.

25 ENERGY STORAGE↗