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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Development of LWR Fuels with Enhanced Accident Tolerance ATF Feasibility Analysis Report Deliverable for the Westinghouse Accident Tolerant Fuel Program

The Westinghouse Electric Company LLC (Westinghouse) accident tolerant fuel (ATF) program utilizes chromium (Cr) coated zirconium alloy cladding with uranium silicide (U 3 Si 2 ) high density/high thermal conductivity fuel for its lead test rod (LTR) program with irradiation beginning in 2019. The lead test assembly (LTA) program will use both SiC/SiC composites and Cr coated zirconium alloy claddings with the high density/high thermal conductivity U 3 Si 2 pellet which will begin in 2022. Over the past several years, Westinghouse has tested the Cr coated zirconium (Zr) and silicon carbide (SiC) claddings in autoclaves and in the Massachusetts Institute of Technology (MIT) reactor and the U 3 Si 2 pellets have been tested in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). High temperature tests at the state-of-the-art Westinghouse facilities in Churchill, PA have been carried out to determine the time and temperature limits for the SiC and Cr coated zirconium claddings. Fuel rod and assembly design in preparation for the LTR and LTA programs is underway as well as licensing efforts with the Nuclear Regulatory Commission (NRC). Finally, accident analyses coupled with economic evaluations for both operating savings as well as fuel savings have been initiated. Cr coated zirconium alloy claddings showed low corrosion rates in both autoclave and in-reactor tests and will be fabricated using commercial processes for the first LTRs for insertion in 2019. Current autoclave results for SiC composite claddings indicate that a corrosion rate of fewer than 2 micrometers per year which meets corrosion requirements may be achieved under normal operating conditions. Modular Accident Analysis Program 5 (MAAP5) calculations indicate that solid fission products can be contained within SiC cladding for up to two hours longer than current Zr based cladding in a station blackout scenario. This additional time is due to the much higher temperature capability of SiC (~2000°C). These two hours can be used to implement additional response options instituted through the FLEX program by reactor operators. While the Cr coated Zr alloy option offers more modest ATF gains (~200°C higher than bare Zr) in similar situations, the coatings do delay the runaway oxidation encountered by uncoated zirconium cladding. Both ATF cladding options also reduce hydrogen production which dramatically reduces primary system and containment pressure and the risk of fission product release beyond containment in the unlikely event of an accident. The lower pressure in the system allows more time to feed cooling water to the core, resulting in the avoidance of fuel melting. The coping time is extended indefinitely as long as the water flow continues. SiC exhibits the highest accident tolerance of any cladding and significant advances in understanding the design, manufacture and accident behavior of SiC cladding have been made. Department of Energy support is needed to continue the on-going experimental work addressing the interaction between U 3 Si 2 and SiC at temperatures >1200°C, the effect of SiC manufacturing methods and manufacturing variability on physical properties, and the ability to predict the mechanical properties of SiC composites based on the composite design. Additionally, experimental work on methods to rapidly fabricate SiC composite structures with high density and reduce the fabrication price of SiC fibers while maintaining a high level of performance is needed. Minimal (<1%) swelling of U 3 Si 2 and subsequent fission gas release has been demonstrated up to 20 MWd/kgU. Irradiation experiments with U 3 Si 2 fuel in ATR to determine these properties at 40 to 50 MWd/kgU are underway. These experiments will provide the data needed to license fuel rod design codes. Research is continuing on production methods for making U 3 Si 2 from UF 6 without going through the U metal step. Oxidation tests of fuel pellets and powder in steam and synthetic air indicate that U 3 Si 2 has a lower oxidation reaction initiation temperature than UO 2 . Options to reduce the U 3 Si 2 oxidation rate are being explored. A hybrid fuel design using pellets with the weight ratio of 30%/70% U 3 Si 2 /UN is currently undergoing testing in the ATR. This approach is being explored to further increase the positive economics of the U 3 Si 2 fuel. In addition to the work supported by the USDOE, research and testing activities are being carried on in a world-wide effort funded by many countries such as Sweden, United Kingdom, Belgium, Netherlands, Spain, Germany, Japan and France. This work is being facilitated through the Westinghouse led Collaboration for Advanced Research on Accident Tolerant Fuel (CARAT) program. Annual meetings are organized by Westinghouse as a venue for presentation of this work and to provide for the cross-fertilization of ideas among the many outstanding researchers in the ATF area. Since SiC, coated cladding and high density fuel options are not currently used in the nuclear industry, support from the government and industry members is needed to further the significant effort of setting new standards. The same is true for the Nuclear Regulatory Commission (NRC) which must review and approve the commercial use of these new fuels since all current regulations are oriented toward Zr/ UO 2 fuel. There are no showstoppers for accident tolerant fuel technologies when considering supply chain, fabrication, enrichment suppliers, production, and licensing. Due to the cost savings from higher density fuel and the accident tolerance of coated claddings, Exelon has identified potential commercial plants to host the LTRs and LTAs. Planning is underway to implement this schedule.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

A hybrid HTS/LTS Superconductor Design for High-Field Accelerator Magnets

High magnetic fields approaching 25 T are needed for significant advances in the physics reach of colliders for high energy physics. Large Hadron Collider (LHC) at CERN needs very high field magnets for planned energy and luminosity upgrades. The envisioned Muon Collider needs such magnets in several areas of the machine. High Temperature Superconductors (HTS) currently offer the best chance of producing hybrid magnets for these applications because HTS has a significantly higher critical current density than any other superconductor at high fields.)

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Facile preparation of porous nickel oxide membrane for flexible supercapacitors electrode via phase-separation method of polymer

Highlights: • Polymer/metal oxide hybrid membrane is fabricated for supercapacitors electrode. • Effects of membrane components on structure and performance are investigated. • The prepared electrode membrane shows high flexible property. • A capacitance of 794 F/g is obtained at a current density of 1.0 A/g. • Symmetric supercapacitor device exhibits an energy density of 39.6 Wh/kg. - Abstract: In this article, a porous flexible membrane electrode of nickel oxide is developed by a facile method based on liquid-liquid phase-separation. The effects of the membrane components on structures and electrochemical behaviors of membrane electrode are investigated. The results reveal that nano NiO and conducting graphite are imbedded into the polymer membrane of polyethersulfone to form a flexible hybrid membrane (M-NiO-G), which shows the highest specific capacitance of 794.0 F/g at a current density of 1.0 A/g. The asymmetrical supercapacitor device based on the as-synthesized of M-NiO-G (positive electrode) and activated carbon membrane (negative electrode) exhibits a high specific capacitance of 154.0 F/g at a current density of 0.2 A/g. The coulombic efficiency remains about 95.0%, and the capacitance retention is 84.8% after 5000 charging-discharging cycles at 1.0 A/g. The energy density of the asymmetrical supercapacitor device reaches 39.6 Wh/kg at a power density of 516.9 W/kg, still remains 20.0 Wh/kg at a high power density of 2567.4 W/kg in the potential window from 0 to 1.36 V in 6 M KOH aqueous solution.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Visible-blind ultraviolet photodetectors on porous silicon carbide substrates

Highlights: • Highly reliable UV detectors are fabricated on porous silicon carbide substrates. • The optical properties of samples are enhanced by increasing the current density. • The optimized sample exhibits enhanced sensitivity to the incident UV radiation. - Abstract: Highly reliable visible-blind ultraviolet (UV) photodetectors were successfully fabricated on porous silicon carbide (PSC) substrates. High responsivity and high photoconductive gain were observed in a metal–semiconductor–metal ultraviolet photodetector that was fabricated on an optimized PSC substrate. The PSC samples were prepared via the UV-assisted photo-electrochemical etching of an n-type hexagonal silicon carbide (6H-SiC) substrate using different etching current densities. The optical results showed that the current density is an outstanding etching parameter that controls the porosity and uniformity of PSC substrates. A highly porous substrate was synthesized using a suitable etching current density to enhance its light absorption, thereby improving the sensitivity of UV detector with this substrate. The electrical characteristics of fabricated devices on optimized PSC substrates exhibited enhanced sensitivity and responsivity to the incident radiation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Interfacial Defect of Lithium Metal in Solid‐State Batteries

Abstract All‐solid‐state battery with Li metal anode is a promising rechargeable battery technology with high energy density and improved safety. Currently, the application of Li metal anode is plagued by the failure at the interfaces between lithium metal and solid electrolyte (SE). However, little is known about the defects at Li–SE interfaces and their effects on Li cycling, impeding further improvement of Li metal anodes. Herein, by performing large‐scale atomistic modeling of Li metal interfaces with common SEs, we discover that lithium metal forms an interfacial defect layer of nanometer‐thin disordered lithium at the Li–SE interfaces. This interfacial defect Li layer is highly detrimental, leading to interfacial failure such as pore formation and contact loss during Li stripping. By systematically studying and comparing incoherent, coherent, and semi‐coherent Li–SE interfaces, we find that the interface with good lattice coherence has reduced Li defects at the interface and has suppressed interfacial failure during Li cycling. Our finding discovered the critical roles of atomistic lithium defects at interfaces for the interfacial failure of Li metal anode, and motivates future atomistic‐level interfacial engineering for Li metal anode in solid‐state batteries.

Yang, Menghao↗
DOE OSTI2021

Interfacial Defect of Lithium Metal in Solid-State Batteries

All-solid-state battery with Li metal anode is a promising rechargeable battery technology with high energy density and improved safety. Currently, the application of Li metal anode is plagued by the failure at the interfaces between lithium metal and solid electrolyte (SE). However, little is known about the defects at Li–SE interfaces and their effects on Li cycling, impeding further improvement of Li metal anodes. Herein, by performing large-scale atomistic modeling of Li metal interfaces with common SEs, we discover that lithium metal forms an interfacial defect layer of nanometer-thin disordered lithium at the Li–SE interfaces. Further, this interfacial defect Li layer is highly detrimental, leading to interfacial failure such as pore formation and contact loss during Li stripping. By systematically studying and comparing incoherent, coherent, and semi-coherent Li–SE interfaces, we find that the interface with good lattice coherence has reduced Li defects at the interface and has suppressed interfacial failure during Li cycling. Our finding discovered the critical roles of atomistic lithium defects at interfaces for the interfacial failure of Li metal anode, and motivates future atomistic-level interfacial engineering for Li metal anode in solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Sub-100 mA/cm 2 CO 2 -to-CO Reduction Current Densities in Hierarchical Porous Gold Electrocatalysts Made by Direct Ink Writing and Dealloying

While most research efforts on CO 2 -to-CO reduction electrocatalysts focus on boosting their selectivity, the reduction rate, directly proportional to the reduction current density, is another critical parameter to be considered in practical applications. This is because mass transport associated with the diffusion of reactant/product species becomes a major concern at a high reduction rate. Nanostructured Au is a promising CO 2 -to-CO reduction electrocatalyst for its very high selectivity. However, the CO 2 -to-CO reduction current density commonly achieved in conventional nanostructured Au electrocatalysts is relatively low (in the range of 1–10 mA/cm 2 ) for practical applications. In this work, we combine direct ink writing-based additive manufacturing and dealloying to design a robust hierarchical porous Au electrocatalyst to improve the mass transport and achieve high CO 2 -to-CO reduction current densities on the order of 64.9 mA/cm 2 with CO partial current density of 33.8 mA/cm 2 at 0.55 V overpotential using an H-cell configuration. Although the current density achieved in our robust hierarchical porous Au electrocatalyst is one order of magnitude higher than the one achieved in conventional nanostructured electrocatalysts, we found that the selectivity of our system is relatively low, namely 52%, which suggests that mass transport remains a critical issue despite the hierarchical porous architecture. We further show that the bulk dimension of our electrocatalyst is a critical parameter governing the interplay between selectivity and reduction rate. In conclusion, the insights gained in this work shed new light on the design of electrocatalysts toward scale-up CO 2 reduction and beyond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Tortuosity Effects in Lithium-Metal Host Anodes

Lithium (Li) metal is the ultimate anode material for Li batteries because of its highest capacity among all candidates. Recent research has focused on stable interphase and host materials to address its low stability and reversibility. Here, we discover that tortuosity is a critical parameter affecting the morphology and electrochemical performances of hosted Li anodes. In three types of hosts—vertically aligned, horizontally aligned, and random reduced graphene oxide (rGO) electrodes with tortuosities of 1.25, 4.46, and 1.76, respectively—we show that high electrode tortuosity causes locally higher current density on the top surface of electrodes, resulting in thick Li deposition on the surface and degraded cycling performance. Low electrode tortuosity in the vertically aligned rGO host enables homogeneous Li transport and uniform Li deposition across the host, realizing greatly improved cycling stability. Furthermore, using this principle of low tortuosity, the designed electrode shows through-electrode uniform morphology with anodic Coulombic efficiency of ~99.1% under high current and capacity cycling conditions.

25 ENERGY STORAGE↗
DOE OSTI2015

High performance charge breeder for HIE-ISOLDE and TSR@ISOLDE applications

We report on the development of the HEC{sup 2} (High Energy Compression and Current) charge breeder, a possible high performance successor to REXEBIS at ISOLDE. The new breeder would match the performance of the HIE-ISOLDE linac upgrade and make full use of the possible installation of a storage ring at ISOLDE (the TSR@ISOLDE initiative [1]). Dictated by ion beam acceptance and capacity requirements, the breeder features a 2–3.5 A electron beam. In many cases very high charge states, including bare ions up to Z=70 and Li/Na-like up to Z=92 could be requested for experiments in the storage ring, therefore, electron beam energies up to 150 keV are required. The electron-beam current density needed for producing ions with such high charge states at an injection rate into TSR of 0.5–1 Hz is between 10 and 20 kA/cm{sup 2}, which agrees with the current density needed to produce A/q<4.5 ions for the HIE-ISOLDE linac with a maximum repetition rate of 100 Hz. The first operation of a prototype electron gun with a pulsed electron beam of 1.5 A and 30 keV was demonstrated in a joint experiment with BNL [2]. In addition, we report on further development aiming to achieve CW operation of an electron beam having a geometrical transverse ion-acceptance matching the injection of 1{sup +} ions (11.5 μm), and an emittance/energy spread of the extracted ion beam matching the downstream mass separator and RFQ (0.08 μm normalized / ± 1%)

43 PARTICLE ACCELERATORS↗
NASA NTRS2011

Thermally Conductive Tape Based on Carbon Nanotube Arrays

To increase contact conductance between two mating surfaces, a conductive tape has been developed by growing dense arrays of carbon nanotubes (CNTs, graphite layers folded into cylinders) on both sides of a thermally conductive metallic foil. When the two mating surfaces are brought into contact with the conductive tape in between, the CNT arrays will adhere to the mating surface. The van der Waals force between the contacting tubes and the mating surface provides adhesion between the two mating surfaces. Even though the thermal contact conductance of a single tube-to-tube contact is small, the tremendous amount of CNTs on the surface leads to a very large overall contact conductance. Interface contact thermal resistance rises from the microroughness and the macroscopic non-planar quality of mating surfaces. When two surfaces come into contact with each other, the actual contact area may be much less than the total area of the surfaces. The real area of contact depends on the load, the surface roughness, and the elastic and inelastic properties of the surface. This issue is even more important at cryogenic temperatures, where materials become hard and brittle and vacuum is used, which prevents any gas conduction through the interstitial region. A typical approach to increase thermal contact conductance is to use thermally conducting epoxies or greases, which are not always compatible with vacuum conditions. In addition, the thermal conductivities of these compounds are often relatively low. The CNTs used in this approach can be metallic or semiconducting, depending on the folding angle and diameter. The electrical resistivity of multiwalled carbon nanotubes (MWCNTs) has been reported. MWCNTs can pass a current density and remain stable at high temperatures in air. The thermal conductivity of a MWCNT at room temperature is measured to be approximately 3,000 W/m-K, which is much larger than that of diamond. At room temperature, the thermal conductance of a 0.3 sq cm array of CNTs was measured to be as high as 10 W/K. The high thermal conductivity and the nanoscale size make CNTs ideal as thermal interface materials. The CNT-based thermal tape can be used for the thermal management of microelectronic packages and electronic systems. It also can be integrated with current device technology and packaging. The material would allow for an efficient method to manage excess heat generation without requiring any additional power. Lastly, the CNT tape can be used to enhance thermal contact conductance across two mating surfaces on some NASA missions.

Kashani, Ali↗
DOE OSTI2015

Transmission electron microscopy studying of structural features of NiTi B2 phase formed under pulsed electron-beam impact

By transmission electron microscopy method the evolution of structural-phase states on a depth of close to equiatomic NiTi modified layer has been studied. Modification performed by pulse impact on its surface low-energy high-current electron beam (beam energy density 10 J/sm{sup 2}, 10 pulses, pulse duration 50mks). It is established that during the treatment in the layer thickness of 8–10 μm, the melting of primary B2 phase and contained therein as Ti2Ni phase particles occurs. The result is change in the concentration ratio of titanium and nickel in the direction of increasing titanium content, which was confirmed by X-ray analysis in the form of increased unit cell parameter B2 phase. Analysis of the electron diffraction pattern showed that the modified layer is characterized as a highly distorted structure on the basis of bcc lattice. Lattice distortions are maximal near the surface and extends to a depth of melt. In subjacent layer there is gradual decline lattice distortions is observed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of heat treatments on superconducting properties and connectivity in K-doped BaFe2As2

Abstract Fe-based superconductors and in particular K-doped BaFe 2 As 2 (K-Ba122) are materials of interest for possible future high-field applications. However the critical current density ( J c ) in polycrystalline Ba122 is still quite low and connectivity issues are suspected to be responsible. In this work we investigated the properties of high-purity, carefully processed, K-Ba122 samples synthesized with two separate heat treatments at various temperatures between 600 and 825 °C. We performed specific heat characterization and T c -distribution analysis up to 16 T and we compared them with magnetic T c and J c characterizations, and transmission-electron-microscopy (TEM) microstructures. We found no direct correlation between the magnetic T c and J c , whereas the specific heat T c -distributions did provide valuable insights. In fact the best J c -performing sample, heat treated first at 750 °C and then at 600 °C, has the peak of the T c -distributions at the highest temperatures and the least field sensitivity, thus maximizing H c2 . We also observed that the magnetic T c onset was always significantly lower than the specific heat T c : although we partially ascribe the lower magnetization T c to the small grain size (< λ , the penetration depth) of the K-Ba122 phase, this behaviour also implies the presence of some grain-boundary barriers to current flow. Comparing the T c -distribution with J c , our systematic synthesis study reveals that increasing the first heat treatment above 750 °C or the second one above 600 °C significantly compromises the connectivity and suppresses the vortex pinning properties. We conclude that high-purity precursors and clean processing are not yet enough to overcome all J c limitations. However, our study suggests that a higher temperature T c -distribution, a larger H c2 and a better connectivity could be achieved by lowering the second heat treatment temperature below 600 °C thus enhancing, as a consequence, J c .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Nanostructured Silicon–Carbon 3D Electrode Architectures for High-Performance Lithium-Ion Batteries

Silicon is an attractive anode material for lithium-ion batteries. However, silicon anodes have the issue of volume change, which causes pulverization and subsequently rapid capacity fade. Herein, we report organic binder and conducting diluent-free silicon–carbon 3D electrodes as anodes for lithium-ion batteries, where we replace the conventional copper (Cu) foil current collector with highly conductive carbon fibers (CFs) of 5–10 μm in diameter. We demonstrate here the petroleum pitch (P-pitch) which adequately coat between the CFs and Si-nanoparticles (NPs) between 700 and 1000 °C under argon atmosphere and forms uniform continuous layer of 6–14 nm thick coating along the exterior surfaces of Si-NPs and 3D CFs. The electrodes fabricate at 1000 °C deliver capacities in excess of 2000 mA h g –1 at C/10 and about 1000 mA h g –1 at 5 C rate for 250 cycles in half-cell configuration. Synergistic effect of carbon coating and 3D CF electrode architecture at 1000 °C improve the efficiency of the Si–C composite during long cycling. Full cells using Si–carbon composite electrode and Li 1.2 Ni 0.15 Mn 0.55 Co 0.1 O 2 -based cathode show high open-circuit voltage of >4 V and energy density of >500 W h kg –1 . Replacement of organic binder and copper current collector by high-temperature binder P-pitch and CFs further enhances energy density per unit area of the electrode. It is believed that the study will open a new realm of possibility for the development of Li-ion cell having almost double the energy density of currently available Li-ion batteries that is suitable for electric vehicles.

25 ENERGY STORAGE↗
DOE OSTI2022

Current advances on Talbot–Lau x-ray imaging diagnostics for high energy density experiments (invited)

Talbot–Lau x-ray interferometry is a refraction-based diagnostic that can map electron density gradients through phase-contrast methods. The Talbot–Lau x-ray deflectometry (TXD) diagnostics have been deployed in several high energy density experiments. To improve diagnostic performance, a monochromatic TXD was implemented on the Multi-Tera Watt (MTW) laser using 8 keV multilayer mirrors (Δθ/θ = 4.5%-5.6%). Copper foil and wire targets were irradiated at 10 14 –10 15 W/cm 2 . Laser pulse length (~10 to 80 ps) and backlighter target configurations were explored in the context of Moiré fringe contrast and spatial resolution. Foil and wire targets delivered increased contrast <30%. The best spatial resolution (<6 μm) was measured for foils irradiated 80° from the surface. Further TXD diagnostic capability enhancement was achieved through the development of advanced data postprocessing tools. The Talbot Interferometry Analysis (TIA) code enabled x-ray refraction measurements from the MTW monochromatic TXD. Additionally, phase, attenuation, and dark-field maps of an ablating x-pinch load were retrieved through TXD. The images show a dense wire core of ~60 μm diameter surrounded by low-density material of ~40 μm thickness with an outer diameter ratio of ~2.3. Attenuation at 8 keV was measured at ~20% for the dense core and ~10% for the low-density material. Instrumental and experimental limitations for monochromatic TXD diagnostics are presented. Enhanced postprocessing capabilities enabled by TIA are demonstrated in the context of high-intensity laser and pulsed power experimental data analysis. Significant advances in TXD diagnostic capabilities are presented. Furthermore, these results inform future diagnostic technique upgrades that will improve the accuracy of plasma characterization through TXD.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compact and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗