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At least 613 records · Page 34

All sources NASA NTRS DOE OSTI

DOE OSTI2023

Sodium Rich Vanadium Oxy‐Fluorophosphate – Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O – as Advanced Cathode for Sodium Ion Batteries

Abstract Conventional sodium‐based layered oxide cathodes are extremely air sensitive and possess poor electrochemical performance along with safety concerns when operating at high voltage. The polyanion phosphate, Na 3 V 2 (PO 4 ) 3 stands out as an excellent candidate due to its high nominal voltage, ambient air stability, and long cycle life. The caveat is that Na 3 V 2 (PO 4 ) 3 can only exhibit reversible capacities in the range of 100 mAh g −1 , 20% below its theoretical capacity. Here, the synthesis and characterizations are reported for the first time of the sodium‐rich vanadium oxyfluorophosphate, Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O, a tailored derivative compound of Na 3 V 2 (PO 4 ) 3 , with extensive electrochemical and structural analyses. Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O delivers an initial reversible capacity of 117 mAh g −1 between 2.5 and 4.5 V under the 1C rate at room temperature, with 85% capacity retention after 900 cycles. The cycling stability is further improved when the material is cycled at 50 °C within 2.8–4.3 V for 100 cycles. When paired with a presodiated hard carbon, Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O cycled with a capacity retention of 85% after 500 cycles. Cosubstitution of the transition metal and fluorine in Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O as well as the sodium‐rich structure are the major factors behind the improvement of specific capacity and cycling stability, which paves the way for this cathode in sodium‐ion batteries.

25 ENERGY STORAGE↗

DOE OSTI2018

Nonhierarchical Heterostructured Fe2O3/Mn2O3 Porous Hollow Spheres for Enhanced Lithium Storage

High capacity transition-metal oxides play significant roles as battery anodes benefiting from their tunable redox chemistry, low cost, and environmental friendliness. However, the application of these conversion-type electrodes is hampered by inherent large volume variation and poor kinetics. Here, a binary metal oxide prototype, denoted as nonhierarchical heterostructured Fe2O3/Mn2O3 porous hollow spheres, is proposed through a one-pot selfassembly method. Beyond conventional heteromaterial, Fe2O3/Mn2O3 based on the interface of (104)Fe2O3 and (222)Mn2O3 exhibits the nonhierarchical configuration, where nanosized building blocks are integrated into microsized spheres, leading to the enhanced structural stability and boosted reaction kinetics. With this design, the Fe2O3/Mn2O3 anode shows a high reversible capacity of 1075 mA h g-1 at 0.5 A g-1, an outstanding rate capability of 638 mA h g-1 at 8 A g-1, and an excellent cyclability with a capacity retention of 89.3% after 600 cycles.

Ren, Wenhao↗

DOE OSTI2018

A study of microstructural evolution of Fe-18Cr-8Ni, Fe-17Cr-12Ni, and Fe-20Cr-25Ni stainless steels after mechanical alloying and annealing

In this study, high-energy mechanical alloying technique was used to produce nanocrystalline stainless steels of three different compositions from elemental powders. The microstructural evolution (grain growth and phase transformation) as a function of alloy compositions and annealing temperatures were investigated by room and high temperature x-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy. The results revealed that stainless steels with low nickel content (i.e., Fe-18Cr-8Ni) underwent a deformation-induced martensitic transformation during room temperature mechanical alloying. Deformation-induced martensitic transformation with increasing nickel content (i.e., Fe-17Cr-12Ni and Fe-20Cr-25Ni) would not be possible by room temperature milling but was created by high strain rate cryogenic processing, the degree to which was compositional dependent. Post process annealing induced the reverse transformation from martensite-to-austenite the ratio of which was found to be a factor of alloy composition and annealing temperature. The real time in-situ x-ray studies showed that the martensite-to-austenite reverse transformation was completed at around 600 °C and 800 °C for Fe-18Cr-8Ni and Fe-20Cr-25Ni steels, respectively. Microscopy studies revealed a significant enhancement in the resistance to grain growth for Fe-17Cr-12Ni steel over other compositions at elevated temperatures as high as 1200 °C. As such, cryogenic processing following by reverse martensitic transformation of high Ni containing alloys provides a pathway for developing higher heat resistant stainless steel alloys.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Structure and Electrochemical Properties of Bronze Phase Materials Containing Two Transition Metals

Bronze phase transition-metal oxides have recently attracted attention as high-rate lithium-ion battery anode materials. Their crystal structures are distinguished by large tunnels and an open framework, facilitating lithium-ion diffusion and high-rate charge–discharge properties. The presence of two transition metals also offers a route to achieve high energy density from multielectron redox. In this paper, we report the chemistry, structure, and electrochemical properties of two different bronze phase compositions having the same stoichiometry: W 3 Nb 2 O 14 and Mo 3 Nb 2 O 14 . These materials provide insight into how the transition metals affect the electrochemical behavior and structural stability of bronze phase materials. Mo 3 Nb 2 O 14 exhibits greater than 1 electron redox per transition metal leading to lithium capacities above 200 mAh g –1 at C/2 but is unable to maintain this high capacity at high rates due to incomplete Mo redox reactions. In contrast, W 3 Nb 2 O14 exhibits reversible redox reactions and retains its open structure on cycling. This study highlights the potential of bronze phase materials containing two transition metals to exhibit fast charging properties with a high energy density.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Engineering Surface Oxygenated Functionalities on Commercial Carbon toward Ultrafast Sodium Storage in Ether-Based Electrolytes

The pursuit of a high-capacity anode material has been urgently required for commercializing sodium-ion batteries with a high energy density and an improved working safety. In the absence of thermodynamically stable sodium intercalated compounds with graphite, constructing nanostructures with expanded interlayer distances is still the mainstream option for developing high-performance carbonaceous anodes. In this regard, a surface-functionalized and pore-forming strategy through a facile CO 2 thermal etching route was rationally adopted to engineer negligible oxygenated functionalities on commercial carbon for boosting the sodium storage process. Benefitted from the abundant ionic/electronic pathways and more active reaction sites in the microporous structure with noticeable pseudocapacitive behaviors, the functionalized porous carbon could achieve a highly reversible capacity of 505 mA h g -1 at 50 mA g -1 , an excellent rate performance of 181 mA h g -1 at 16,000 mA g -1 , and an exceptional rate cycle stability of 176 mA h g -1 at 3200 mA g -1 over 1000 cycles. These outstanding electrochemical properties should be ascribed to a synergistic mechanism, fully utilizing the graphitic and amorphous structures for synchronous intercalations of sodium ions and solvated sodium ion compounds, respectively. Finally, the controllable generation and evolution of a robust but thin solid electrolyte interphase film with the emergence of obvious capacitive reactions on the defective surface, favoring the rapid migration of sodium ions and solvated species, also contribute to a remarkable electrochemical performance of this porous carbon black.

25 ENERGY STORAGE↗

DOE OSTI2015

Understanding the role of NH 4 F and Al 2 O 3 surface co-modification on lithium-excess layered oxide Li 1.2 Ni 0.2 Mn 0.6 O 2

In this work we prepared Li 1.2 Ni 0.2 Mn 0.6 O 2 (LNMO) using a hydroxide co-precipitation method and investigated the effect of co-modification with NH 4 F and Al 2 O 3 . After surface co-modification, the first cycle Coulombic efficiency of Li 1.2 Ni 0.2 Mn 0.6 O 2 improved from 82.7% to 87.5%, and the reversible discharge capacity improved from 253 to 287 mAh g –1 at C/20. Moreover, the rate capability also increased significantly. A combination of neutron diffraction (ND), high-resolution transmission electron microscopy (HRTEM), aberration-corrected scanning transmission electron microscopy (a-STEM)/electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS) revealed the changes of surface structure and chemistry after NH 4 F and Al 2 O 3 surface co-modification while the bulk properties showed relatively no changes. These complex changes on the material s surface include the formation of an amorphous Al 2 O 3 coating, the transformation of layered material to a spinel-like phase on the surface, the formation of nanoislands of active material, and the partial chemical reduction of surface Mn 4+ . Such enhanced discharge capacity of the modified material can be primarily assigned to three aspects: decreased irreversible oxygen loss, the activation of cathode material facilitated with preactivated Mn 3+ on the surface, and stabilization of the Ni-redox pair. In conclusion, these insights will provide guidance for the surface modification in high-voltage-cathode battery materials of the future.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Mitigation of Shuttle Effect in Li–S Battery Using a Self-Assembled Ultrathin Molybdenum Disulfide Interlayer

Lithium–sulfur batteries are promising for low-cost and high-energy storage, but their applications are still limited by poor cycling stability owing to soluble lithium polysulfide shuttling during battery operation. Avoiding shuttle effect is challenging but it is essential to avoid active material loss and prevent performance decay. We use an ultrathin layer of MoS 2 with thickness of 10–40 nm, which is 1–2 orders of magnitude thinner than conventional interlayers, for Li–S batteries to mitigate polysulfide shuttling. The MoS2 layer formed by exfoliated nanoflakes is deposited by the scalable liquid-based self-assembly method. With less than 1% of additional weight in the cathode, the MoS 2 interlayer with complete coverage inhibits polysulfide diffusion across the separator and therefore remarkably improves the battery performances. Reversible specific capacity reaches 1010 and 600 mA h g –1 at 0.5 and 2C rates, respectively, which decay slowly over 400 cycles (0.11% per cycle). Moreover, the MoS 2 films with high density of catalytic active flake edges enable high areal sulfur loading up to 10 mg cm –2 and areal capacity up to 9.7 mA h cm –2 at a current density of 3.2 mA cm –2 .

25 ENERGY STORAGE↗

DOE OSTI2014

Statistically optimal analysis of state-discretized trajectory data from multiple thermodynamic states

We propose a discrete transition-based reweighting analysis method (dTRAM) for analyzing configuration-space-discretized simulation trajectories produced at different thermodynamic states (temperatures, Hamiltonians, etc.) dTRAM provides maximum-likelihood estimates of stationary quantities (probabilities, free energies, expectation values) at any thermodynamic state. In contrast to the weighted histogram analysis method (WHAM), dTRAM does not require data to be sampled from global equilibrium, and can thus produce superior estimates for enhanced sampling data such as parallel/simulated tempering, replica exchange, umbrella sampling, or metadynamics. In addition, dTRAM provides optimal estimates of Markov state models (MSMs) from the discretized state-space trajectories at all thermodynamic states. Under suitable conditions, these MSMs can be used to calculate kinetic quantities (e.g., rates, timescales). In the limit of a single thermodynamic state, dTRAM estimates a maximum likelihood reversible MSM, while in the limit of uncorrelated sampling data, dTRAM is identical to WHAM. dTRAM is thus a generalization to both estimators.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Lipid sponge droplets as programmable synthetic organelles

Living cells segregate molecules and reactions in various subcellular compartments known as organelles. Spatial organization is likely essential for expanding the biochemical functions of synthetic reaction systems, including artificial cells. Many studies have attempted to mimic organelle functions using lamellar membrane-bound vesicles. However, vesicles typically suffer from highly limited transport across the membranes and an inability to mimic the dense membrane networks typically found in organelles such as the endoplasmic reticulum. Here, we describe programmable synthetic organelles based on highly stable nonlamellar sponge phase droplets that spontaneously assemble from a single-chain galactolipid and nonionic detergents. Due to their nanoporous structure, lipid sponge droplets readily exchange materials with the surrounding environment. In addition, the sponge phase contains a dense network of lipid bilayers and nanometric aqueous channels, which allows different classes of molecules to partition based on their size, polarity, and specific binding motifs. The sequestration of biologically relevant macromolecules can be programmed by the addition of suitably functionalized amphiphiles to the droplets. We demonstrate that droplets can harbor functional soluble and transmembrane proteins, allowing for the colocalization and concentration of enzymes and substrates to enhance reaction rates. Droplets protect bound proteins from proteases, and these interactions can be engineered to be reversible and optically controlled. Our results show that lipid sponge droplets permit the facile integration of membrane-rich environments and self-assembling spatial organization with biochemical reaction systems.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2015

Three component vibrational time reversal communication

Time reversal provides an optimal prefilter matched signal to apply to a communication signal before signal transmission. Time reversal allows compensation for wave speed dispersion and can function well in reverberant environments. Time reversal can be used to focus elastic energy to each of the three components of motion independently. A pipe encased in concrete was used to demonstrate the ability to conduct communications of information using three component time reversal. Furthermore, the ability of time reversal to compensate for multi-path distortion (overcoming reverberation) will be demonstrated and the rate of signal communication will be presented. [The U.S. Department of Energy, through the LANL/LDRD Program, is gratefully acknowledged for supporting this work.]

42 ENGINEERING↗

DOE OSTI2019

Scalable Polymer Precursor Based LiPON Type Li-Metal Interface Enabled High Performance Li-Sulfur Battery

The Battery 500 program objective is to research, develop, and demonstrate lithium battery technologies capable of achieving 500 Wh/kg with stable lifetime of 1000 cycles. This Battery 500 seedlings project has demonstrated a new approach and a pathway toward the program’s goals in just one awarded and executed phase. Cells have been assembled, tested, and evaluated. This report details efforts to develop polymer precursor electrolytes that offer properties anticipated to be similar or superior to LiPON glasses. Such precursors offer the potential to be used to process LiPON-like thin glass/ceramic coatings for use in lithium batteries. LiPON glasses provide a design basis for the synthesis of sets of oligomers/polymers by lithiation of OP(NH 2 ) 3-x (NH) x [from OP(NH) 3 ], OP(NH 2 ) 3-x (NHSiMe 3 ) x and [P=N] 3 (NHSiMe 3 ) 6-x (NH) x . Polymer electrolytes impregnated in/on celgard exhibit Li+ conductivities up to ~1×10 -5 S/cm at room temperature and are thermally stable to ≈150 °C. A Li-S battery assembled using a Li 6 SiPON composition polymer electrolyte exhibits an initial reversible capacity of 1500 mAh/g sulfur and excellent cycle performance at 0.25 and 0.5 C rate over 120 cycles, declining to 750 mAh/g at after a 220 h test period. At the same time, computational studies were performed to understand the conduction mechanism of LIPON and its interaction with Li metal. These initial project results provide a foundation for further development of the system to achieve the program goal.

25 ENERGY STORAGE↗

DOE OSTI2019

Polymer precursors for coatings, binder and adhesive applications for solid state electrolytes

We report here efforts to develop polymer precursor electrolytes that offer properties anticipated to be similar or superior to LiPON glasses. Such precursors offer the potential to be used to process LiPON-like thin glass/ceramic coatings for use in ASBs. Here, LiPON glasses provide a design basis for the synthesis of a set of oligomers/polymers by lithiation of OP(NH 2 ) 3-x (NH) x [from OP(NH) 3 ], OP(NH 2 ) 3-x (NHSiMe 3 ) x and [P=N] 3 (NHSiMe 3 ) 6-x (NH) x . The resulting systems have degrees of polymerization ranging from 5-20. Treatment with selected amounts of LiNH 2 provides varying degrees of lithiation and Li + conducting properties commensurate with Li + content. The polymer electrolytes + celgard exhibit Li + conductivities as high as ~1 × 10 -5 S/cm at room temperature. The polymer electrolytes are also thermally stable up to ≈150 °C. A Li-S battery was assembled using a Li 6 SiPON composition polymer electrolyte. This battery exhibits an initial reversible capacity of 1500 mAh/g sulfur and excellent cycle performance at 0.25 and 0.5 C rate over 120 cycles, declining to 750 mAh/g at the end of the 220 h test period.

Temeche, Eleni↗

DOE OSTI2017

Star Formation in Galaxies at z ∼ 4–5 from the SMUVS Survey: A Clear Starburst/Main-sequence Bimodality for Hα Emitters on the SFR–M* Plane

We study a large galaxy sample from the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6 μm fluxes indicative of strong Hα emission at z=3.9--4.9. We find that the percentage of “Hα excess” sources reaches 37%–40% for galaxies with stellar masses log{sub 10}(M{sup ∗}/M{sub ⊙})≈9--10 and decreases to <20% at log{sub 10}(M{sup ∗}/M{sub ⊙})∼10.7. At higher stellar masses, however, the trend reverses, although this is likely due to active galactic nucleus contamination. We derive star formation rates (SFR) and specific SFR (sSFR) from the inferred Hα equivalent widths of our “Hα excess” galaxies. We show, for the first time, that the “Hα excess” galaxies clearly have a bimodal distribution on the SFR–M* plane: they lie on the main sequence of star formation (with log{sub 10}(sSFR/yr{sup −1})<−8.05) or in a starburst cloud (with log{sub 10}(sSFR/yr{sup −1})>−7.60). The latter contains ∼15% of all the objects in our sample and accounts for >50% of the cosmic SFR density at z=3.9--4.9, for which we derive a robust lower limit of 0.066 M{sub ⊙} yr{sup −1} Mpc{sup −3}. Finally, we identify an unusual >50σ overdensity of z=3.9--4.9 galaxies within a 0.20×0.20 arcmin{sup 2} region. We conclude that the SMUVS unique combination of area and depth at mid-IR wavelengths provides an unprecedented level of statistics and dynamic range that are fundamental to revealing new aspects of galaxy evolution in the young universe.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1981

Measurement of sound absorption in the air

The large temperature gradient in each section of the resonance tube resulting from the liquid nitrogen coolant necessitated a design modification to the cooling system. A timer and four solenoid valves were installed so that the coolant flow can be reversed periodically. The hardware and software for controlling the analog to digital converter and conversion rate were completed, and the system is operational. A duty cycle control circit was implemented so that on the sixteenth conversion a relay shuts off the vibration exciter used to generate the sound wave. Thus the starting point of each decay curve is exactly known. This information is necessary for evaluating the g digital decay information. The data acquisition and digital decay evaluation programs are described.

Meredith, R.↗

NASA NTRS1981

New technologies for solar energy silicon - Cost analysis of dichlorosilane process

A reduction in the cost of silicon for solar cells is an important objective in a project concerned with the reduction of the cost of electricity produced with solar cells. The cost goal for the silicon material is about $14 per kg (1980 dollars). The process which is currently employed to produce semiconductor grade silicon from trichlorosilane is not suited for meeting this cost goal. Other processes for producing silicon are, therefore, being investigated. A description is presented of results obtained for the DCS process which involves the production of dichlorosilane as a silicon source material for solar energy silicon. Major benefits of dichlorosilane as a silicon source material include faster reaction rates for chemical vapor deposition of silicon. The DCS process involves the reaction 2SiHCl3 yields reversibly SiH2Cl2 + SiCl4. The results of a cost analysis indicate a total product cost without profit of $1.29/kg of SiH2Cl2.

Yaws, C. L.↗

NASA NTRS1983

Spacelab high density digital recorders

The design and performance of the high-density digital recorder (HDDR) developed for use at the NASA centers (KSC, JSC, and GSFC) and at the JPL to store and retrieve 50-Mb/s PCM data streams from the Spacelab experiments are reported. The recording reproduction, and transport requirements are reviewed; and the design solutions adopted in the final version of the HDDR are described, incuding three-position-modulation and Y-phase encoding, microprocessor-controlled automatic bit synchronization and equalization, cyclic-redundancy-check error detection and correction, clock regeneration, data and clock variations, tape-speed control, and EEE-488 remote control. Reliable performance, with bit error rates 1 in 10 to the 10th forward and 1 in 10 to the 9th reverse or better and packing density up to 50 percent greater than that obtainable using conventional codes, is reported after 1.5 years of service.

Blais, R. A.↗

NASA NTRS1990

Dynamic ground effects

A research program is underway at the NASA Langley Research Center to study the effect of rate of descent on ground effects. A series of powered models were tested in the Vortex Research Facility under conditions with rate of descent and in the 14 x 22 Foot Subsonic Tunnel under identical conditions but without rate of descent. These results indicate that the rate of descent can have a significant impact on ground effects particularly if vectored or reversed thrust is used.

Paulson, John W., Jr.↗

NASA NTRS1993

Intrinsic fatigue crack growth rates for Al-Li-Cu-Mg alloys in vacuum

The influences of microstructure and deformation mode on inert environment intrinsic fatigue crack propagation were investigated for Al-Li-Cu-Mg alloys AA2090, AA8090, and X2095 compared to AA2024. The amount of coherent shearable delta-prime (Al3Li) precipitates and extent of localized planar slip deformation were reduced by composition (increased Cu/Li in X2095) and heat treatment (double aging of AA8090). Intrinsic growth rates, obtained at high constant K(max) to minimize crack closure and in vacuum to eliminate any environmental effect, were alloy dependent; da/dN varied up to tenfold based on applied Delta-K or Delta-K/E. When compared based on a crack tip cyclic strain or opening displacement parameter, growth rates were equivalent for all alloys except X2095-T8, which exhibited unique fatigue crack growth resistance. Tortuous fatigue crack profiles and large fracture surface facets were observed for each Al-Li alloy independent of the precipitates present, particularly delta-prime, and the localized slip deformation structure. Reduced fatigue crack propagation rates for X2095 in vacuum are not explained by either residual crack closure or slip reversibility arguments; the origin of apparent slip band facets in a homogeneous slip alloy is unclear.

Slavik, D. C.↗