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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Bi aliovalent substitution in Li 7 La 3 Zr 2 O 12 garnets: Structural and ionic conductivity effects

We report on the synthesis of cubic-phase garnet-type solid-state electrolytes based on Bi-doped Li 7 La 3 Zr 2 O 12 (LLZO). Bi aliovalent substitution of Zr in LLZO utilizing the Pechini processing method is employed to synthesize Li 7-x La 3 Zr 2-x Bi x O 12 compounds. A strong dependence of the ionic conductivity on Bi content is observed, and under our synthesis and sintering conditions, a >100-fold increase over the un-doped sample is observed for x=0.75. Cubic-phase Li 6 La 3 Zr 1 BiO 12 compounds are generated upon annealing in air in the temperature range 650 °C-900 °C. In contrast, in the absence of Bi, the cubic garnet phase of Li 7 La 3 Zr 2 O 12 is not formed below 700 °C and a transformation to the tetragonal phase is observed at similar to 900 °C for this un-doped compound. The role of Bi in lowering the formation temperature of the garnet cubic phase and in the ionic conductivity improvements is investigated in this work. We ascribe the effect of Bi-doping on ionic conductivity increments to changes in Li + -site occupancy and lattice parameters and the reduction in the formation temperature for the cubic-phase formation to rate enhancements of the solid-state reaction. To identify the site occupancy of Bi in the garnet structure, we employ synchrotron extended x-ray absorption fine structure spectroscopy. Our results indicate that Bi additions occupy the Zr-type sites exclusively, to within the accuracy of the measurements.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Rating aircraft on energy

Questions concerning the energy efficiency of aircraft compared to ground transport are considered, taking into account as energy intensity the energy consumed per passenger statute mile. It is found that today's transport aircraft have an energy intensity potential comparable to that of ground modes. Possibilities for improving the energy density are also much better in the case of aircraft than in the case of ground transportation. Approaches for potential reductions in aircraft energy consumption are examined, giving attention to steps for increasing the efficiency of present aircraft and to reductions in energy intensity obtainable by the introduction of new aircraft utilizing an advanced technology. The use of supercritical aerodynamics is discussed along with the employment of composite structures, advances in propulsion systems, and the introduction of very large aircraft. Other improvements in fuel economy can be obtained by a reduction of skin-friction drag and a use of hydrogen fuel.

Maddalon, D. V.↗
DOE OSTI2019

From natural material to high-performance silicon based anode: Towards cost-efficient silicon based electrodes in high-performance Li-ion batteries

As one of the highest specific capacity anode materials in lithium-ion batteries, the main technical issue for silicon (Si) based electrodes is the rapid capacity fading caused by the huge volume changes. Porous Si materials are reported to efficiently alleviate the side effects of volume fluctuation. However, the expensive precursor and complicated production process in previous reports limited their practical applications. Herein, we report a cost-efficient approach on the fabrication of porous Si via the low temperature aluminothermic reduction of low cost natural raw materials, combining the advantages of low temperature and natural materials. The porous structure of attapulgite-derived Si (Si ATP ) is well retained during the compositing process. The obtained composite electrode Si ATP /graphite@carbon (Si ATP /G@C) exhibits excellent electrochemical performance, with a reversible discharge capacity of 799 mAh g -1 after 100 cycles. To demonstrate the versatility of the approach, another natural ore, mica (MIC), was also utilized to the fabrication of porous Si (SiMIC). As expected, the SiMIC/graphite@carbon composite electrode also exhibits high specific capacity (697 mAh g -1 after 100 cycles), superior capacity retention (81% after 100 cycles based the 4th cycle), and outstanding rate capability.

25 ENERGY STORAGE↗
DOE OSTI2017

Yearlong semi-continuous operation of thermophilic two-stage anaerobic digesters amended with biochar for enhanced biomethane production

This study aimed to scale up an integrated waste-to-energy system for producing pipelinequality biomethane from shake flasks experiments to two-stage digester systems with semicontinuous operation. The yearlong operation was successfully conducted to compare the performance of thermophilic anaerobic digestion (AD) of sewage sludge amended with corn stover biochar (CSBC) and pine biochar (PBC) to the control under various conditions. Both CSBC and PBC promoted the substrate utilization, methane productivity, and process stability of AD, while CSBC showed superior potential. CSBC enhanced methane content in biogas (CH 4 %) and methane production rate (P CH$_4$ ) by up to 25% and 37% respectively in comparison to the control, with maximum CH 4 % of 95% and CH 4 yield of 0.34 L/g volatile solid (VS)-added being achieved at steady state. The biochar supplementation also led to a substantial increase of the macro- and micro-nutrients (P, K, Ca, Mg, Fe) by up to 33 times in the digestate, increasing its fertilizer value. Finally, microbial community structure and dynamics were also investigated and compared, and in particular, CSBC promoted the abundance of Clostridia and Methanosarcina. Collectively, this study proves that pyro-biochar as an effective additive material enhances AD performance with continuous operation and that CSBC shows greater potential.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Enhanced rate performance of Li3V2(PO4)3/C cathode by an improved rheological phase assisted microwave method

Highlights: • Rheological phase assisted microwave can utilize both advantages of two methods. • Polyethylene glycol was used as both rheological medium and carbon precursor. • 101.8 mA h g{sup −1} of specific capacity was obtained at 50 C rates. - Abstract: In this study, high-rate Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite is successfully synthesized via an improved rheological phase assisted microwave method using polyethylene glycol as both rheological medium and carbon precursor. The relatively uniform Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} particles are encapsulated in amorphous carbon architecture to form core-shell structure, providing effective electron and ion transport. When used as a cathode material in lithium ion battery, the Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite displays a maximum discharge capacity of 101.8 mA h g{sup −1} at 50 C charge/discharge rate and still possesses 98.3% of capacity retention after 100 cycles, demonstrating superior rate capability and excellent cycling stability when compared with bare Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}. The observed electrochemical performance could be attributed to uniform coated-carbon pyrolysis from polyethylene glycol rheological phase precursor and small Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} pristine particles synthesized by the fast microwave heating route.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Cross-Scale Catalyst Modeling Applied to H 2 Storage and Release via Formic Acid

Here, we propose the Systems-to-Atoms (S2A) modeling framework that integrates the kinetics of reaction chemistry and structural configurations across various length scales with the aim of establishing a versatile template for multiscale modeling of reactive flow problems and to predict the operando activity of catalyst materials. The approach encompasses a microkinetic model to analyze surface reactions on individual facets of catalyst nanoparticles coupled with the computation of average surface reaction rates for catalyst nanoparticles of specific size distributions. Macro-homogeneous surface reaction kinetics are derived as a function of catalyst loading and used as input parameters for the continuum-scale reactor model. The cross-scale framework enables the optimization of catalyst utilization through reactor design and operating strategy. To demonstrate the framework, we studied the storage and release of hydrogen from formic acid, a promising liquid organic hydrogen carrier (LOHC), over Pd, Pt, and Cu catalysts. The framework predicts observed trends in formic acid dehydrogenation activity for catalysts with comparable weight loadings and metal particle diameters, demonstrating satisfactory quantitative alignment. Finally, the seamless transmission of parameter uncertainties between scales is also discussed.

08 HYDROGEN↗
DOE OSTI2021

Ultrafast optical switching and power limiting in intersubband polaritonic metasurfaces

Highly nonlinear optical materials with fast third-order nonlinear optical response are crucial for the operation of all-optical photonic devices, such as switches for signal processing and computation, power limiters, and saturable absorbers. The nonlinear response of traditional optical materials is weak, thus requiring large light intensities to induce significant changes in their properties. Here we show that optical control of the coupling rate in subwavelength patch antennas coupled to intersubband transitions in multi-quantum-well semiconductor heterostructures can provide a giant third-order nonlinear response, on the order of 3.4 × <#comment/> 10 − <#comment/> 13 m 2 / V 2 , with a response time < <#comment/> 2 p s . We utilize this effect to realize intersubband polaritonic metasurfaces and demonstrate their operation as highly nonlinear saturable and reverse saturable absorbers, enabling optical power limiters and other elements for all-optical modulation and control. Our approach enables a plethora of compact, low-power, highly nonlinear devices with spectral, temporal, and structured wavefront responses tailored by design.

Mann, Sander A. (ORCID:0000000277420615)↗
NASA NTRS2018

New Moon Explorer Robotic Precursor Mission Concept

A low-cost reconnaissance mission concept has been devised of Earth’s ‘New Moon’, the recently discovered Earth orbital companion asteroid 2016HO3. 2016HO3 provides a compelling destination to address science, economic, and asteroid protection objectives and could serve to influence the future direction of human exploration in cis-lunar space by offering an additional destination for human exploration and utilization. Key enabling technologies, solar sail propulsion, thin film power generation and telecommunications capabilities, and small spacecraft technology have reached a development milestone enabling an affordable reconnaissance mission. Leveraging the solar sail technology and mission expertise resident at the National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) resulting from the Human Exploration and Operations Mission Directorate (HEOMD) funded Near Earth Asteroid (NEA) Scout mission, and combining this with the science and instrument expertise at the Goddard Space Flight Center (GSFC), a 12U scale small spacecraft mission can characterize 2016HO3. Spin rate, pole position, shape, structure, mass, density, chemical composition, temperature, thermal inertia, regolith characteristics, and spectral type can be determined using a small, CubeSat form factor within a three year time of flight. This paper outlines the outcome of a concept study for the New Moon Explorer (NME), a solar sail propelled reconnaissance mission of 2016HO3.

Dervan, Jared A.↗
DOE OSTI2023

Optimal Storage Response to Utility Tariff Structures and Potential Use of Capacity Charges

Energy storage is increasingly being deployed in behind-the-meter use cases, partially in response to falling lithium-ion prices and new utility tariff structures. Utilities are grappling with new tariff design in the presence of distributed energy resources (DER), trying to motivate, fairly price the contribution of, and, in some cases, discourage, certain operation of DER. There are opportunities for energy storage under emerging tariff structures, but utility net load management objectives for storage remain unclear. Diverse tariff structures motivate the use of energy storage to provide one or a combination of: energy arbitrage, energy shifting, solar self-consumption, and import shaving. This paper formulates a linear optimization to demonstrate the optimal storage tariff response, examining customer net load metrics under diverse utility tariff structures, such as time-of-use, net metering, feed-in tariffs, zero export tariffs, and demand charges. A key contribution of this paper is the introduction and examination of a capacity charge as mechanism that can both motivate reductions in both peak import, and exports, along with greater load levelling.

behind-the-meter↗
DOE OSTI2020

Virtual storage capability of residential buildings for sustainable smart city via model-based predictive control

This paper evaluates the virtual storage capability of a residential air-conditioning (AC) system by utilizing the building mass as a thermal storage to enable sustainable cities through model-based predictive control (MPC). The control-oriented building model was developed with a grey-box model structure based on the experimental data to predict the indoor air temperature. Based on the model, the operation cost-saving potential of the MPC was investigated in a single house with different comfort levels, electricity prices, and prediction horizons. The cost-saving of the MPC was approximately 10.6 % compared to the conventional control. The MPC was expanded to a residential building cluster considering the peak demand charge. In an hourly shedding and load-up scenario, the performances of the MPC and the heuristic prior-based control (PBC) are promising. When shedding was enforced all day, the peak demand saving of the MPC was 36~38 %, whereas that of the PBC was 25.7 % compared to the baseline. In addition, the monthly electricity bill, including the operation and peak demand cost, was investigated with different demand charge rates and weather conditions. The total saving decreased with a low demand charge rate and hot conditions, and the operation cost saving was compromised with more aggressive demand shedding.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Luminescent Bimetallic Two-Coordinate Gold(I) Complexes Utilizing Janus Carbenes

A series of bimetallic carbene-metal-amide (cMa) complexes have been prepared with bridging biscarbene ligands to serve as a model for the design of luminescent materials with large oscillator strengths and small energy differences between the singlet and triplet states (ΔE ST ). The complexes have a general structure (R 2 N)Au(:carbene—carbene:)Au(NR 2 ). The bimetallic complexes show solvation-dependent absorption and emission that is analyzed in detail. It is found that the molar absorptivity of the bimetallic complexes is correlated with the energy barrier to rotation of the metal–ligand bond. The bimetallic cMa complexes also exhibit short emission lifetimes (τ = 200–300 ns) with high photoluminescence efficiencies (Φ PL > 95%). The radiative rates of bimetallic cMa complexes are 3–4 times faster than that of the corresponding monometallic complexes. Analysis of temperature-dependent luminescence data indicates that the lifetime for the singlet state (τS 1 ) of bimetallic cMa complexes is near 12 ns with a ΔE ST of 40–50 meV. Here the presented compounds provide a general design for cMa complexes to achieve small values for ΔE ST while retaining high radiative rates. Solution-processed organic light-emitting devices (OLEDs) made using two of the complexes as luminescent dopants show high efficiency and low roll-off at high luminance.

14 SOLAR ENERGY↗
DOE OSTI2021

Revisiting Discharge Mechanism of CF x as a High Energy Density Cathode Material for Lithium Primary Battery

Lithium/fluorinated graphite (Li/CFx) primary batteries show great promise for applications in a wide range of energy storage systems due to their high energy density (>2100 Wh kg –1 ) and low self-discharge rate (<0.5% per year at 25 °C). While the electrochemical performance of the CF x cathode is indeed promising, the discharge reaction mechanism is not thoroughly understood to date. In this article, a multiscale investigation of the CF x discharge mechanism is performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, cross-sectional focused ion beam, high-resolution transmission electron microscopy, and scanning transmission electron microscopy with electron energy loss spectroscopy are utilized to investigate this system. Results show no metallic lithium deposition or intercalation during the discharge reaction. Crystalline lithium fluoride particles uniformly distributed with <10 nm sizes into the CF x layers, and carbon with lower sp2 content similar to the hard-carbon structure are the products during discharge. This article deepens the understanding of CF x as a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance.

25 ENERGY STORAGE↗
DOE OSTI2019

Microstructure and Mechanical Properties of Ni-based Superalloy K418 Produced by the Continuous Unidirectional Solidification Process

Adopting effective strategies to control the solidification structure of Ni-based superalloys is a very interesting subject for metallurgists. Despite the achievement of developing and applying the continuous unidirectional solidification process in simple alloys, the utilization of this process for K418 alloys has been ignored. The microstructure and mechanical properties of a K418 alloy ingot produced by the continuous unidirectional solidification process were investigated. We found that the γ dendrites were typically cross-shaped in the transverse section. The orientation of surviving grains along the casting direction was <001> during competitive growth. The secondary dendrite arm spacing was 32.3 ± 2.5 μm at a cooling rate of 1.75 ± 0.35 °C/s from the surface to the center of the K418 alloy ingot. Due to the higher cooling rate than that of the conventional casting process, a more uniform microstructure and finer γ′ precipitation were obtained in the ingot. Thus, compared with the conventional casting, the tensile strength and the elongation are increased by 8.4 and 21.3%, respectively, at 25 °C. The tensile strength and elongation increased by 15.2 and 49.3%, respectively, at 800 °C. In addition, the fracture surfaces exhibited numerous typical dimples and dendritic fracture characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Target preparation of multicomponent composites Au@CdS/g-C3N4 as efficient visible light photocatalysts with the assistance of biomolecules

Highlights: • Au@CdS/g-C{sub 3}N{sub 4} composites were prepared through a novel biomolecules assisted hydrothermal route. • Au@CdS core-shell structure is formed in composites. • The composites exhibit high visible light photocatalytic activity and stability. • The enhanced photocatalytic properties are ascribed to the efficient charges separation. - Abstract: In this work, we aimed to develop a novel method for the target preparation of multicomponent composites Au@CdS/g-C{sub 3}N{sub 4} towards high visible light photocatalytic activity with the assistance of L-cysteine biomolecules. Through the interaction of L-cysteine biomolecules with Au nanoparticles and g-C{sub 3}N{sub 4} bulks, CdS layer were in-situ precipitated on the surface of Au nanoparticles to form core-shell structure Au@CdS and Z-scheme structure Au@CdS-g-C{sub 3}N{sub 4} with good interface bonding in composites. By taking advantage of this feature, the highest reaction rate constant of 8%Au@CdS/g-C{sub 3}N{sub 4} for methyl orange dye and phenol degradation was 3.08- and 1.48-folds higher than pure g-C{sub 3}N{sub 4} bulks, which was ascribed to the strong interaction between different substances for efficient charges transferring and separation as evidenced by the studies of X-ray photoelectron spectroscopy, steady-state and transient photoluminescence spectroscopy. This work highlights the utilization of biomolecules for the target preparation of composites and its application on environmental remediation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1993

Navier-Stokes calculations on multi-element airfoils using a chimera-based solver

A study of Navier-Stokes calculations of flows about multielement airfoils using a chimera grid approach is presented. The chimera approach utilizes structured, overlapped grids which allow great flexibility of grid arrangement and simplifies grid generation. Calculations are made for two-, three-, and four-element airfoils, and modeling of the effect of gap distance between elements is demonstrated for a two element case. Solutions are obtained using the thin-layer form of the Reynolds averaged Navier-Stokes equations with turbulence closure provided by the Baldwin-Lomax algebraic model or the Baldwin-Barth one equation model. The Baldwin-Barth turbulence model is shown to provide better agreement with experimental data and to dramatically improve convergence rates for some cases. Recently developed, improved farfield boundary conditions are incorporated into the solver for greater efficiency. Computed results show good comparison with experimental data which include aerodynamic forces, surface pressures, and boundary layer velocity profiles.

Jasper, Donald W.↗
NASA NTRSDate not supplied

Single-Scattering Properties of Melting Precipitation for GPM Passive Microwave and Radar Remote Sensing Applications

Over the past two decades, detailed computational simulations of the intricate three dimensional structures of ice-phase crystals and aggregates of those crystals have been developed. The microwave single-scattering properties of these simulated ice particles have been computed and used to improve quantitative estimates of snow rates and to better deRne the vertical structure of snow water contents in deep convective systems, as derived from satellite-borne passive microwave and/or radar remote sensing measurements. The same icephase particles have more recently been used as the starting point for simulations of melting precipitation using computational melting methods. In the current study, a heuristic melting method, as well as a physically-based melting procedure based on smoothed-particle hydrodynamics, are applied to ice particle models to describe the full evolution of the particles from dry snow to liquid drops. The discrete dipole approximation is utilized to calculate the single-scattering properties of the mixed-phase particles throughout the melting process. Then, the properties of the particles are “mapped” into simpliRed microphysical simulations of particle size spectra in the melting layers of stratiform, precipitating clouds. The bulk single-scattering properties of the melting layers and the sensitivity of their properties to modeling assumptions are explored, and the implications for combined radar-radiometer precipitation remote sensing from GPM are discussed.

William S Olson↗
DOE OSTI2018

Evaluation of the synergistic effect between slow photons and electron trapping on the photocatalytic properties of TiO2 photonic crystals

Highlights: • We report the preparation of titanium dioxide photonic crystals (PCs) having two pore sizes. • Electronic band gap (BG) and photonic band gap (PBG) were determined with the use of UV–vis spectroscopy. • The position of PBG was affected by the pore size of PC. • Metallic silver (electron trapping centers) were generated on the surface of both types of PCs by a photoreduction of silver Ag{sup +} ions. • Photocatalytic properties of silver-modified TiO{sub 2} photonic crystals were enhanced by synergistic effect caused by overlapping the edges of PBG and BG combined with electron trapping by AgNPs. - Abstract: Titanium dioxide photonic crystals (PCs) were obtained using the sol-gel method and polystyrene (PS) microspheres as a template with two different diameters: 300 nm and 460 nm. The resulting materials were labeled as PC-300 and PC-460. In the following step, PCs were modified with silver nanoparticles (AgNPs) generated by the photoreduction of silver Ag{sup +} ions. The obtained PCs were denoted as AgNPs/PC-300 and AgNPs/PC-460. The size of the AgNPs were 28 nm ± 2 nm for the AgNPs/PC-300 and 21 nm ± 1 nm for AgNPs/PC-460. The characteristic features of TiO{sub 2} PCs, such as electronic band gap (BG), photonic band gap (PBG) and an occurrence of slow photon effect (SPE), were determined with the use of UV–vis spectroscopy. The photocatalytic performance of the prepared PCs was defined by monitoring the photodegradation rates of Rhodamine B (RhB) measured in the presence of PC-300, PC-460, AgNPs/PC-300, AgNPs/PC-460 and non-porous TiO{sub 2} coating (NPC) as reference material. It was found that the appropriate utilization of SPE by overlapping the edge of PBG with semiconductor BG and electron trapping by the presence of AgNPs exerted a strong synergistic effect on the photocatalytic properties of AgNPs/PCs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Microbially mediated iron redox cycling of subsurface sediments from Hanford Site, Washington State, USA

Iron-bearing clay minerals are predominant in soils and sediments, and they undergo oxidation-reduction cycles as a result of natural processes such as wetting/drying cycles and plant root respiration. However, the kinetics and mechanisms of multiple redox cycles of iron in clay-rich sediments and consequences of such cycling on sediment properties are poorly understood. The objective of this study was to understand how multiple redox cycles of Fe in clay-rich sediment affect the rate and extent of Fe bioreduction and the physicochemical properties of the sediment. A natural sediment sample containing Fe-bearing montmorillonite from Hanford, Washington, USA was size-fractionated [2.0 to 0.5 μm (Hanford-C) and 0.5 to 0.02 μm (Hanford-F)] and redox-cycled for four times. Bioreduction was achieved utilizing Geobacter sulfurreducens and re-oxidization was performed with sparged air. Time-course change of total Fe (II) was monitored to measure the rate and extent of Fe (III) bioreduction. Redox-cycled sediments were characterized to determine the physicochemical changes. Both the initial rate and extent of bioreduction fluctuated across the four redox cycles, but they ultimately decreased from 5.3 μmol g -1 h -1 and 22.9% to nearly zero by the fourth cycle. These fluctuation patterns were likely due to a combined effect of reductive dissolution of small/poorly crystalline clay particles (by 3–5%) and clay mineral structural changes, as evidenced by redox induced changes of aqueous chemistry, surface area, cation exchange capacity, mineralogy, and Mössbauer parameters. Once these small/poorly crystalline clay particles were dissolved, structural Fe in residual larger and more crystalline clay particles was largely reversible across additional redox cycles, as revealed by Mössbauer spectroscopy through the first three cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗