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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Interface-induced fast Li+ transport in mixed ionic–electronic conductors

Interfacial instability between lithium metal and solid-state electrolytes limits the performance of all-solid-state lithium metal batteries (ASSLBs), leading to parasitic reactions, non-uniform Li+ flux, and dendrite growth. Here, we develop a composite interlayer composed of the anti-perovskite Li2OHCl0.75Br0.25 (AP) and carbon nanotubes (CNTs) to enhance both interfacial stability and ionic transport. The AP–CNT interlayer exhibits enhanced Li+ conductivity arising from interfacial electron transfer from AP to CNTs, which generates a built-in electric field that facilitates Li+ migration. Lithium symmetric cells incorporating this interlayer achieve a high critical current density of 2.4 mA cm−2 at 55 °C. This design integrates chemical robustness with coupled ion–electron transport, offering a generalizable strategy for safe, dendrite-free, and high-performance ASSLBs.

He, Chenche↗
NASA NTRS1992

Quantum well, beam deflecting surface emitting lasers

This invention relates to surface emitting semiconductor lasers (SELs), with integrated 45 deg. beam deflectors. A SEL is formed on a wafer including vertical mirrors and 45 deg. beam deflectors formed in grooves by tilted ion beam etching. A SEL is a lattice matched, or unstrained, AlGaAs/GaAs GRINSCH SQW SEL. An alternate embodiment is shown, in which a SEL is lattice mismatched, strained or pseudomorphic, or InGaAs/AlGaAs GRINSCH SQW SEL which emits radiation at a wavelength to which its substrate is transparent. Both SELs exhibit high output power, low threshold current density, and relatively high efficiency, and each are processing compatible with conventional large scale integration technology. Such SELs may be fabricated in large numbers from single wafers. The novel features of this invention include the use of tilted ion beam etching to form a pair of grooves each including vertical mirrors and 45 deg. beam deflectors. The embodiment provides substantial circuit design flexibility because radiation may be coupled both up and/or down through the substrate.

Kim, Jae H.↗
NASA NTRS1981

On the theory of coronal heating mechanisms

The present state-of-the-art of two classes of theories of coronal heating is examined: (1) heating by acoustic processes in the 'nonmagnetic' parts of the atmosphere (the shock-wave theory is an example); and (2) heating by electrodynamic processes in the magnetic regions of the corona (beta much less than 1) either by MHD waves or current heating in regions with high electric current densities (flare-type heating). It is concluded that the mechanism of the heating of the solar chromosphere and corona remains an open question, especially in explaining detailed atmospheric structures. The acoustic theory might be correct with little modification for most of the chromosphere, but as soon as the atmosphere shows a high degree of structure as in the corona and transition layer the magnetic field must play a dominant role. It appears that the current heating theories have a small range of applicability, while the MHD-wave theories are the most promising.

Kuperus, M.↗
DOE OSTI2023

Tailoring activity of iron phthalocyanine by edge-nitrogen sites induced electronic delocalization

Fe-N-C catalysts have been recognized as the most satisfactory candidates alternatively to Pt-based catalysts for oxygen reduction reaction (ORR). However, fine-tailoring of their intrinsic ORR catalytic activity still remains a great challenge due to the inferior accessibility and intrinsic activity of FeN x moieties. Herein, one order of magnitude activity enhancement of pristine Fe-N-C through cooperating with nitrogen-doped carbon micro-flower is achieved. The axial coordination effect between Fe active center and nitrogen atoms in support can break the electronic distribution symmetry of FeN x moieties and induce the electron delocalization on Fe active center and the electron localization on N, respectively, which favor the adsorption behavior of *OH intermediate. As a result, the catalyst exhibits a remarkable half-wave potential of 0.9 V and a high kinetic current density of 74.04 mA cm -2 at 0.85 V. In addition, when utilized as a cathode catalyst of liquid Zn-air batteries (ZABs), it possesses excellent electrochemical performance, for example, a high open circuit voltage (OCV) and peak power density of 1.59 V and 170.09 mW cm -2 , respectively. In conclusion, this work provides a new understanding into the activity enhancement mechanism of Fe-N-C catalysts, and inspires electronic delocalization of active sites for adjusting catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Leakage and field emission in side-gate graphene field effect transistors

We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO{sub 2}/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO{sub 2} up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Mitigating Heavy Ion Irradiation‐Induced Degradation in p‐type SnO Thin‐Film Transistors at Room Temperature

The study investigates the mitigation of radiation damage on p‐type SnO thin‐film transistors (TFTs) with a fast, room‐temperature annealing process. Atomic layer deposition is utilized to fabricate bottom‐gate TFTs of high‐quality p‐type SnO layers. After 2.8 MeV Au 4+ irradiation at a fluence level of 5.2 × 10 12 ions cm −2 , the output drain current and on/off current ratio ( I on / I off ) decrease by more than one order of magnitude, field‐effect mobility ( μ FE ) reduces more than four times, and subthreshold swing (SS) increases more than four times along with a negative shift in threshold voltage. The observed degradation is attributed to increased surface roughness and defect density, as confirmed by scanning electron microscopy (SEM), high‐resolution micro‐Raman, and transmission electron microscopy (TEM) with geometric phase analysis (GPA). A technique is demonstrated to recover the device performance at room temperature and in less than a minute, using the electron wind force (EWF) obtained from low‐duty‐cycle high‐density pulsed current. At a pulsed current density of 4.0 × 10 5 A cm −2 , approximately four times increase in I on / I off is observed, 41% increase in μ FE , and 20% decrease in the SS of the irradiated TFTs, suggesting effectiveness of the new annealing technique.

Al-Mamun, Nahid Sultan↗
NASA NTRS2018

Exploring Li-Air Batteries for High Specific Energy and High Power Applications: A Simulation Study

Commercialization of lithium-air batteries face many challenges, such as electrolyte decomposition, short cycle life, low energy efficiency, low power density, etc. However, commercialization of Li-air batteries for mass sensitive applications such as electric vehicles, portable power source, and drones is more challenging due to additional constraints of safety, electrolyte evaporation, high specific energy requirements, and reliable discharge times. In this presentation, we will present our finite element simulation results comparing Li-O2 and Li-air batteries using power density, energy density, specific power, and discharge times as metrics to evaluate different electrolytes and electrode geometry to reduce total mass and maximize discharge current. We use a finite element model and a discharge product model developed in which is based on porous electrode and concentrated electrolyte theories and the discharge product is modeled using quantum tunneling; for reaction kinetics and oxygen diffusion, an improved model was used. The electrolyte properties such as ion conductivity and ion diffusion were obtained from Molecular Dynamics (MD) simulations while the other parameters for the finite element model were calibrated to match experiments at high discharge current densities (>1.5 mA/cm2). The mass densities of different electrolytes were computed using MD simulations as well. For this presentation, we examine the practical electrochemical mass of a system at different current ratings, the sensitivity of mass to the use of ambient air as compared to pure oxygen as well as the electrolyte, which affects maximum current density and the total mass associated with the electrolyte (which includes the mass of additional components), and, the optimization of battery geometry for total discharge time, average discharge voltage, maximum discharge current, and minimum electrochemical mass.

Mehta, M.↗
DOE OSTI2021

Advanced manufacturing for electrosynthesis of fuels and chemicals from CO 2

Advanced manufacturing (AM) represents an appealing approach for creating novel electrochemical systems for chemicals synthesis. In this work, we demonstrate AM for rapid development and testing for improved performance for the carbon dioxide reduction reaction across an evolution of vapor-fed reactor designs. In our final design, we observe activation- and mixed-control regimes for a variety of operating conditions via inlet CO 2 flow rate and electrochemical potential. Furthermore, we define a dimensionless number (Da) to identify mass transport regimes by exploring the impact of hypothesized underlying mass transport mechanisms, including consumption of CO 2 via OH - , increased local temperatures, and partial penetration of electrolyte into gas diffusion layer. The accelerated pace of reactor design and development led to high geometric current densities (500 mA cm -2 ), heightened selectivity (85.5% FE C 2+ products), and increased carbon dioxide conversion (16.6%) and cathodic energy efficiency (49.6% CO 2 R). Using AM vapor-fed reactors, we attain high ethylene (3.67%) and record ethanol (3.66%) yields compared to the literature. Finally, this work underscores the promise of AM for accelerating reactor design, understanding of governing phenomena, and improving the performance of catalytic systems.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Laser wavelength dependence of particle acceleration mechanisms in high intensity laser–solid density plasma interactions

We investigate the generation of relativistic electrons and the subsequent ion acceleration due to target-normal sheath acceleration when ultra-intense (⁠ I > 10 18 W/cm 2 ⁠) short pulse (⁠ τ L < 10ps⁠) lasers are incident onto solid density targets as laser wavelength is varied. Scaling laws for the hot electron temperature, T hot ⁠, and the maximum ion energy, E max ⁠, are recast as a function of laser wavelength. These predictions are compared to results from particle-in-cell computer simulations in a variety of geometries, including cases where realistic plasma density profiles as determined by a radiation hydrodynamics code are used. It is found that the wavelength dependence observed in simulation is less pronounced than what is predicted from the well-established scaling laws. An assessment of how switching to longer laser wavelengths, specifically 2 μm Tm:YLF technology, would impact current high energy density science applications and diagnostics is made.

Electromagnetism↗
DOE OSTI2019

The Importance of Water Transport in High Conductivity and High-Power Alkaline Fuel Cells

High ionic conductivity membranes can be used to minimize ohmic losses in electrochemical devices such as fuel cells, flow batteries, and electrolyzers. Very high hydroxide conductivity was achieved through the synthesis of a norbornene-based tetrablock copolymer with an ion-exchange capacity of 3.88 meq/g. The membranes were cast with a thin polymer reinforcement layer and lightly cross-linked with N,N,N',N'-tetramethyl-1,6-hexanediamine. The norbornene polymer had a hydroxide conductivity of 212 mS/cm at 80°C. Light cross-linking helped to control the water uptake and provide mechanical stability while balancing the bound (i.e. waters of hydration) vs. free water in the films. The films showed excellent chemical stability with <1.5% conductivity loss after soaking in 1 M NaOH for 1000 h at 80°C. The aged films were analyzed by FT-IR before and after aging to confirm their chemical stability. A H 2 /O 2 alkaline polymer electrolyte fuel cell was fabricated and was able to achieve a peak power density of 3.5 W/cm 2 with a maximum current density of 9.7 A/cm 2 at 0.15 V at 80°C. The exceptionally high current and power densities were achieved by balancing and optimizing water removal and transport from the hydrogen negative electrode to the oxygen positive electrode. High water transport and thinness are critical aspects of the membrane in extending the power and current density of the cells to new record values.

08 HYDROGEN↗
DOE OSTI2019

High current carrying and thermal conductive copper-carbon conductors

The surging demand for miniaturized compact devices has generated the need for new metal conductors with high current carrying ampacity, electric and thermal conductivity. Herein, we report carbon-metal conductors that exhibit a high breakdown current density (39% higher than copper) and electrical conductivity (e.g. 63% higher than that of copper at 363 K) in a broad temperature range. The mechanistic studies of thermal conductivity through first-principle modeling show that the multilayer graphene percolation networks efficiently decrease the electron-phonon coupling in the copper-graphene composites, even if phonon modes are activated at a high temperature. These results imply that the copper-based composites have the potential to be the next generation metal conductor with high electrical and thermal conductivity, as well as excellent current-carrying ampacity. More importantly, the developed composite can be deployed in the ink form, making it possible to be utilized by the microelectronic fabrication process.

Zhang, Wei↗
DOE OSTI2026

Evaluation of DIII-D plasmas for Future Measurements of the Driven Current Density in the DIII-D High Field Side Lower Hybrid Experiment

High field side (HFS) lower hybrid current drive (LHCD) is a promising method for efficiently driving off-axis current in steady state tokamak power plants. The first test of this technology is underway at the DIII-D tokamak. The initial physics goal is to measure the LH-driven current density profile in order to validate the ray-tracing/Fokker-Plank codes GENRAY/CQL3D and gain confidence in their ability to predict LH deposition in future DIII-D experiments and fusion power plants. DIII-D’s motional Stark effect (MSE) diagnostic will be used to constrain the magnetic equilibrium reconstructions. From these reconstructions, the ohmic, bootstrap, and driven non-inductive components of the current density profile can be extracted. Several recent DIII-D plasmas have been identified in which GENRAY/CQL3D predict measurable amounts of current with only 100 kW of coupled power.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb 3 Sn with and without an O source

In this paper we show that addition of Hf to Nb4Ta can significantly improve the high field performance of Nb 3 Sn, making it suitable for dipole magnets for a machine like the 100 TeV Future Circular Collider (FCC). A big challenge of the FCC is that the desired non-Cu critical current density (J c ) target of 1500 A mm –2 (16 T, 4.2 K) is substantially above the best present Nb 3 Sn conductors doped with Ti or Ta (~1300 A mm –2 in the very best sample of the very best commercial wire). Recent success with internal oxidation of Nb–Zr precursor has shown significant improvement in the layer J c of Nb 3 Sn wires, albeit with the complication of providing an internal oxygen diffusion pathway and avoiding degradation of the irreversibility field H Irr . We here extend the Nb1Zr oxidation approach by comparing Zr and Hf additions to the standard Nb4Ta alloy of maximum H c2 and H Irr . Nb4Ta rods with 1Zr or 1Hf were made into monofilament wires with and without SnO 2 and their properties measured over the entire superconducting range at fields up to 31 T. We found that Group IV alloying of Nb4Ta does raise H Irr , though O 2 addition still slightly degrades it. As noted in earlier Nb1Zr work with an O source, the pinning force density F p is strongly enhanced and its peak value shifted to higher field by internal oxidation. A surprising result of this work is that we found better properties in Nb4Ta1Hf without SnO 2 , F pMax achieving 2.35 times that of the standard Nb4Ta alloy, while the oxidized Nb4Ta1Zr alloy achieved 1.54 times that of the Nb4Ta alloy. The highest layer J c (16 T, 4.2 K) of 3700 A mm –2 was found in the SnO 2 -free wire made with Nb4Ta1Hf alloy. Using a standard A15 cross-section fraction of 60% for modern powder-in-tube and rod restack process wires, we estimated that a non-Cu J c of 2200 A mm –2 is obtainable in modern conductors, well above the 1500 A mm –2 FCC specification. Moreover, since the best properties were obtained without SnO 2 , the Nb4Ta1Hf alloy appears to open a straightforward route to enhanced properties in Nb 3 Sn wires manufactured by virtually all the presently used commercial routes employed today.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Organic Additive‐derived Films on Cu Electrodes Promote Electrochemical CO 2 Reduction to C 2+ Products Under Strongly Acidic Conditions

Abstract Electrochemical CO 2 reduction (CO 2 R) at low pH is desired for high CO 2 utilization; the competing hydrogen evolution reaction (HER) remains a challenge. High alkali cation concentration at a high operating current density has recently been used to promote electrochemical CO 2 R at low pH. Herein we report an alternative approach to selective CO 2 R (>70 % Faradaic efficiency for C 2+ products, FE C2+ ) at low pH (pH 2; H 3 PO 4 /KH 2 PO 4 ) and low potassium concentration ([K + ]=0.1 M) using organic film‐modified polycrystalline copper (Modified‐Cu). Such an electrode effectively mitigates HER due to attenuated proton transport. Modified‐Cu still achieves high FE C2+ (45 % with Cu foil /55 % with Cu GDE) under 1.0 M H 3 PO 4 (pH≈1) at low [K + ] (0.1 M), even at low operating current, conditions where HER can otherwise dominate.

Nie, Weixuan↗
DOE OSTI2022

Record >10 MV/cm mesa breakdown fields in Al 0.85 Ga 0.15 N/Al 0.6 Ga 0.4 N high electron mobility transistors on native AlN substrates

The ultra-wide bandgap of Al-rich AlGaN is expected to support a significantly larger breakdown field compared to GaN, but the reported performance thus far has been limited by the use of foreign substrates. In this Letter, the material and electrical properties of Al 0.85 Ga 0.15 N/Al 0.6 Ga 0.4 N high electron mobility transistors (HEMT) grown on a 2-in. single crystal AlN substrate are investigated, and it is demonstrated that native AlN substrates unlock the potential for Al-rich AlGaN to sustain large fields in such devices. We further study how Ohmic contacts made directly to a Si-doped channel layer reduce the knee voltage and increase the output current density. High-quality AlGaN growth is confirmed via scanning transmission electron microscopy, which also reveals the absence of metal penetration at the Ohmic contact interface and is in contrast to established GaN HEMT technology. Two-terminal mesa breakdown characteristics with 1.3 μm separation possess a record-high breakdown field strength of ~11.5 MV/cm for an undoped Al 0.6 Ga 0.4 N-channel layer. The breakdown voltages for three-terminal devices measured with gate-drain distances of 4 and 9 μm are 850 and 1500 V, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Organic Additive–derived Films on Cu Electrodes Promote Electrochemical CO 2 Reduction to C 2+ Products Under Strongly Acidic Conditions

Electrochemical CO 2 reduction (CO 2 R) at low pH is desired for high CO 2 utilization; the competing hydrogen evolution reaction (HER) remains a challenge. High alkali cation concentration at a high operating current density has recently been used to promote electrochemical CO 2 R at low pH. Herein we report an alternative approach to selective CO2R (>70 % Faradaic efficiency for C 2+ products, FE C2+ ) at low pH (pH 2; H 3 PO 4 /KH 2 PO 4 ) and low potassium concentration ([K + ]=0.1 M) using organic film-modified polycrystalline copper (Modified-Cu). Furthermore, such an electrode effectively mitigates HER due to attenuated proton transport. Modified-Cu still achieves high FE C2+ (45 % with Cu foil /55 % with Cu GDE) under 1.0 M H 3 PO 4 (pH≈1) at low [K + ] (0.1 M), even at low operating current, conditions where HER can otherwise dominate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Double sulfur vacancies by lithium tuning enhance CO2 electroreduction to n-propanol

Electrochemical CO 2 reduction can produce valuable products with high energy densities but the process is plagued by poor selectivities and low yields. Propanol represents a challenging product to obtain due to the complicated C 3 forming mechanism that requires both stabilization of *C 2 intermediates and subsequent C 1 –C 2 coupling. Herein, density function theory calculations revealed that double sulfur vacancies formed on hexagonal copper sulfide can feature as efficient electrocatalytic centers for stabilizing both CO* and OCCO* dimer, and further CO–OCCO coupling to form C 3 species, which cannot be realized on CuS with single or no sulfur vacancies. The double sulfur vacancies were then experimentally synthesized by an electrochemical lithium tuning strategy, during which the density of sulfur vacancies was well-tuned by the charge/discharge cycle number. The double sulfur vacancy-rich CuS catalyst exhibited a Faradaic efficiency toward n-propanol of 15.4 ± 1% at -1.05 V versus reversible hydrogen electrode in H-cells, and a high partial current density of 9.9 mA cm -2 at -0.85 V in flow-cells, comparable to the best reported electrochemical CO 2 reduction toward n-propanol. Our work suggests an attractive approach to create anion vacancy pairs as catalytic centers for multi-carbon-products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Vertical Co 9 S 8 hollow nanowall arrays grown on a Celgard separator as a multifunctional polysulfide barrier for high-performance Li–S batteries

Lithium–sulfur (Li–S) batteries have been regarded as one of the most promising next-generation energy-storage devices, due to their low cost and high theoretical energy density (2600 W h kg -1 ). However, the severe dissolution of lithium polysulfides (LiPSs) and the fatal shuttle effect of the sulfur cathode seriously hinder the practical applications of Li–S batteries. To address such issues, we present here, for the first time, a novel metal organic framework (MOF)-derived Co 9 S 8 nanowall array with vertical hollow nanoarchitecture and high electrical conductivity, which is grown in situ on a Celgard separator (Co 9 S 8 –Celgard) via a feasible and scalable liquid-reaction approach, as an efficient barrier for LiPSs in Li–S batteries. Benefiting from the direct in situ growth of vertical Co 9 S 8 hollow nanowall arrays as a multifunctional polar barrier, the Co 9 S 8 –Celgard separator possesses large surface area, excellent mechanical stability, and particularly strong LiPS-trapping ability via chemical and physical interactions. With these advantages, even with a pure sulfur cathode with a high sulfur loading of 5.6 mg cm -2 , the Li–S cells with the Co 9 S 8 –Celgard separator exhibit outstanding electrochemical performance: the initial specific capacity is as high as 1385 mA h g -1 with a retention of 1190 mA h g -1 after 200 cycles. The cells deliver a high capacity of 530 mA h g -1 at a 1C rate (1675 mA g -1 ) even after an impressive number of 1000 cycles with an average capacity fade of only 0.039% per cycle, which is promising for long-term cycling application at high charge/discharge current densities, and pouch-type Li–S cells with the Co 9 S 8 –Celgard separator display excellent cycling performance. When the optimized cathode with the sulfur loading in well-designed yolk–shelled carbon@Fe 3 O 4 (YSC@Fe 3 O 4 ) nanoboxes is employed, the cell with Co 9 S 8 –Celgard delivers a high initial capacity of 986 mA h g -1 at a 1C rate with a capacity retention as high as 83.2% even after a remarkable number of 1500 cycles. In conclusion, this work presents a strategy to grow on the separator a multifunctional polar interlayer with unique nanoarchitecture and high conductivity to chemically and physically trap the LiPSs, thus significantly enhancing the performance of Li–S batteries.

25 ENERGY STORAGE↗