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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The influence of surface preparation on low temperature HfO{sub 2} ALD on InGaAs (001) and (110) surfaces

Current logic devices rely on 3D architectures, such as the tri-gate field effect transistor (finFET), which utilize the (001) and (110) crystal faces simultaneously thus requiring passivation methods for the (110) face in order to ensure a pristine 3D surface prior to further processing. Scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and correlated electrical measurement on MOSCAPs were utilized to compare the effects of a previously developed in situ pre-atomic layer deposition (ALD) surface clean on the InGaAs (001) and (110) surfaces. Ex situ wet cleans are very effective on the (001) surface but not the (110) surface. Capacitance voltage indicated the (001) surface with no buffered oxide etch had a higher C{sub max} hypothesized to be a result of poor nucleation of HfO{sub 2} on the native oxide. An in situ pre-ALD surface clean employing both atomic H and trimethylaluminum (TMA) pre-pulsing, developed by Chobpattana et al. and Carter et al. for the (001) surface, was demonstrated to be effective on the (110) surface for producing low D{sub it} high C{sub ox} MOSCAPs. Including TMA in the pre-ALD surface clean resulted in reduction of the magnitude of the interface state capacitance. The XPS studies show the role of atomic H pre-pulsing is to remove both carbon and oxygen while STM shows the role of TMA pre-pulsing is to eliminate H induced etching. Devices fabricated at 120 °C and 300 °C were compared.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2002

Enzyme-based CO2 capture for advanced life support

Elevated CO2 levels in air can lead to impaired functioning and even death to humans. Control of CO2 is critical in confined spaces that have little physical or biological buffering capacity (e.g., spacecraft, submarines, or aircraft). A novel enzyme-based contained liquid membrane bioreactor was designed for CO2 capture and certain application cases are reported in this article. The results show that the liquid layer accounts for the major transport resistance. With addition of carbonic anhydrase, the transport resistance decreased by 71%. Volatile organic compounds of the type and concentration expected to be present in either the crew cabin or a plant growth chamber did not influence carbonic anhydrase activity or reactor operation during 1-day operation. Alternative sweep method studies, examined as a means of eliminating consumables, showed that the feed gas could be used successfully in a bypass mode when combined with medium vacuum pressure (-85 kPa) to achieve CO2 separation comparable to that with an inert sweep gas. The reactor exhibited a selectivity for CO2 versus N2 of 1400:1 and CO2 versus O2 is 866:1. The CO2 permeance was 1.44 x 10(-7) mol m-2 Pa-1 s-1 (4.3 x 10(-4) cm3 cm-2 s-1 cmHg-1) at a feed concentration of 0.1% CO2. These data show that the enzyme-based contained liquid membrane is a promising candidate technology that may be suitable for NASA applications to control CO2 in the crew or plant chambers.

NASA Discipline Life Support Systems↗
DOE OSTI2020

Toward lower-diameter large-scale HPC and data center networks with co-packaged optics

We investigate the advantages of using co-packaged optics for building low-diameter, large-scale high-performance computing (HPC) and data center networks. The increased escape bandwidth offered by co-packaged optics can enable high-radix switch implementations of more than 150 switch ports, which can be combined with data rates of up to 400 Gb/s per port. From the network architecture perspective, the key benefits of using co-packaged optics in future fat-tree networks include (a) the ability to implement large-scale topologies of > <#comment/> 11 , 000 end points by eliminating the need for a third switching layer and (b) the ability to provide up to 4 × <#comment/> higher bisection bandwidth compared to existing solutions, reducing at the same time the number of required switch application-specific integrated circuits by > <#comment/> 80 % <#comment/> . From the network operation perspective, both reduced energy consumption and lower packet delays can be achieved since fewer hops are required; i.e., packets need to traverse fewer serializer/deserializer lanes and fewer switch buffers, which reduces the probability of contending with other packets and improves the tolerance of network congestion. The performance of the proposed architecture is evaluated via discrete-event simulations for a wide range of representative HPC synthetic-traffic cases that include both hotspot and non-hotspot scenarios. The simulation results suggest that co-packaged optics form a promising solution to keep up with bandwidth scaling in future networks, while the reduced number of switching layers can lead to significant mean packet delay improvements that start from 30% and reach up to 74% for high-load conditions.

Maniotis, Pavlos (ORCID:0000000244905253)↗
DOE OSTI2018

Machine learning enabled acoustic detection of sub-nanomolar concentration of trypsin and plasmin in solution

Here, we demonstrate a machine learning enabled low-cost acoustic detection of protease which may find application in assuring quality and safety of dairy products, drug screening, molecular profiling, and disease diagnostics. A hydrophilic SiO 2 -coated quartz crystal microbalance (QCM) acts as a substrate to assemble α-, β-, and κ-casein layers (protease reporters) and as a transducer for measuring changes in frequency as casein is removed by protease. We demonstrate that α-, β-, and κ-caseins can form stable assembly on SiO 2 from phosphate-buffered solution (PBS) solution. Exposure to protease results in cleaving of casein which changes the frequency of the 1st–11th odd harmonics of QCM. Monitoring β-casein cleavage allows ~0.2 nM detection of trypsin and ~0.5 nM detection of plasmin and enables differentiation between trypsin and plasmin after <2 min of protease exposure. The casein-coated QCM allows sub-nanomolar detection and classification of protease.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Electrochemical-Reaction-Driven Interfacial Stress in a Solid-Solid Layered Architecture

Reaction-driven interfacial growth causes significant strain in layered architectures accompanied by mass transfer and moving boundaries. We present an analytical construct of the stress generated in a multilayer film, which incorporates the elastic-plastic strain of the growth layer, which suggests its strong dependence on the mechanical properties and thickness. This analytical formalism is further applied to a layered all-solid-state lithium battery architecture. This study demonstrates that mechanical stability can be enhanced by using a positive electrode material with high stiffness, porous hosts for lithium plating, and small external elastic constraints to buffer the volumetric changes in the electrode material. Furthermore, our results also reveal that small surface flaws in the solid electrolyte and high internal hydrostatic pressure can alleviate lithium dendrite growth through surface cracks.

25 ENERGY STORAGE↗
DOE OSTI2024

SQMS science advances impact on Rigetti commercial processors

The collaboration between the Superconducting Quantum Materials and Systems Center (SQMS) and Rigetti Computing produced several advancements in our understanding of the role of materials characteristics in quantum processor performance. This partnership leverages SQMS's extensive characterization infrastructure and cutting-edge research in materials, and Rigetti's expertise in quantum hardware and robust nanofabrication to improve precision and performance of Rigetti's test QPUs. Qubit frequency is determined in large part by the properties of Josephson junctions (JJs) made of amorphous oxide tunnel barriers; the Alternating-Bias Assisted Annealing (ABAA) process allows us to tune JJs to their desired frequency [1]. Work by SQMS researchers in characterizing high-precision JJs post-processed (using ABAA) have yielded crucial information on the nature of the structure and chemical bonding uniformity of the ABAA processed amorphous oxides. Performance has also been improved through a comprehensive series of experiments that tested encapsulation and surface treatment. Encapsulation of the niobium metal layer with tantalum resulted in an T1 improvement of 80%, experimentally confirming the role of Nb surface losses in qubit performance [2]. Pre-treatment of the underlying silicon surface prior to JJ fabrication by replacing a buffered oxide etch (BOE) with hydrofluoric acid (HF) followed by aqueous ammonium fluoride (NH4F) has shown a statistically significant improvement of T1 by 22%, and reduction in the number of strongly-coupled TLS [3]. These examples, as well as many other published and ongoing investigations, demonstrate the mutual benefits that come from Rigetti's involvement in the SQMS collaboration. [1] - Pappas, D.P., et al. (2024). https://doi.org/10.1038/s43246-024-00596-z [2] - Bal, M., et al. (2024). https://doi.org/10.1038/s41534-024-00840-x [3] Kopas, C. J. et al. Preprint at https://doi.org/10.48550/arXiv.2408.02863 (2024).

Lachman, Ella↗
DOE OSTI2015

Gas breakthrough and emission through unsaturated compacted clay in landfill final cover

Highlights: • Explore feasibility of unsaturated clay as a gas barrier in landfill cover. • Gas breakthrough pressure increases with clay thickness and degree of saturation. • Gas emission rate decreases with clay thickness and degree of saturation. • A 0.6 m-thick clay layer may be sufficient to meet gas emission rate limit. - Abstract: Determination of gas transport parameters in compacted clay plays a vital role for evaluating the effectiveness of soil barriers. The gas breakthrough pressure has been widely studied for saturated swelling clay buffer commonly used in high-level radioactive waste disposal facility where the generated gas pressure is very high (in the order of MPa). However, compacted clay in landfill cover is usually unsaturated and the generated landfill gas pressure is normally low (typically less than 10 kPa). Furthermore, effects of clay thickness and degree of saturation on gas breakthrough and emission rate in the context of unsaturated landfill cover has not been quantitatively investigated in previous studies. The feasibility of using unsaturated compacted clay as gas barrier in landfill covers is thus worthwhile to be explored over a wide range of landfill gas pressures under various degrees of saturation and clay thicknesses. In this study, to evaluate the effectiveness of unsaturated compacted clay to minimize gas emission, one-dimensional soil column tests were carried out on unsaturated compacted clay to determine gas breakthrough pressures at ultimate limit state (high pressure range) and gas emission rates at serviceability limit state (low pressure range). Various degrees of saturation and thicknesses of unsaturated clay sample were considered. Moreover, numerical simulations were carried out using a coupled gas–water flow finite element program (CODE-BRIGHT) to better understand the experimental results by extending the clay thickness and varying the degree of saturation to a broader range that is typical at different climate conditions. The results of experimental study and numerical simulation reveal that as the degree of saturation and thickness of clay increase, the gas breakthrough pressure increases but the gas emission rate decreases significantly. Under a gas pressure of 10 kPa (the upper bound limit of typical landfill gas pressure), a 0.6 m or thicker compacted clay is able to prevent gas breakthrough at degree of saturation of 60% or above (in humid regions). Furthermore, to meet the limit of gas emission rate set by the Australian guideline, a 0.6 m-thick clay layer may be sufficient even at low degree of saturation (i.e., 10% like in arid regions)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

The construction of the phase-1 upgrade of the CMS pixel detector

The innermost layers of the original CMS tracker were built out of pixel detectors arranged in three barrel layers and two forward disks in each endcap. The original CMS detector was designed for the nominal instantaneous LHC luminosity of 1×10 34 cm -2 s -1 . Under the conditions expected in the coming years, which will see an increase of a factor two of the instantaneous luminosity, the CMS pixel detector would have seen a dynamic inefficiency caused by data losses due to buffer overflows. For this reason the CMS collaboration has installed a replacement pixel detector during the recent extended end of year shutdown. The phase-1 upgrade of the CMS pixel detector will operate at high efficiency at an instantaneous luminosity of 2×10 34 cm -2 s -1 with increased detector acceptance and additional redundancy for the tracking, while at the same time reducing the material budget. These goals are achieved using a new read-out chip and modified powering and read-out schemes, one additional tracking layer both in the barrel and in the disks, and new detector supports including a CO 2 based evaporative cooling system, that contribute to the reduction of the material in the tracking volume. This contribution will review the design and technological choices of the phase-1 detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Materials properties and dislocation dynamics in InAsP compositionally graded buffers on InP substrates

The properties of InAs{sub x}P{sub 1−x} compositionally graded buffers grown by metal organic chemical vapor deposition are investigated. We report the effects of strain gradient (ε/thickness), growth temperature, and strain initiation sequence (gradual or abrupt strain introduction) on threading dislocation density, surface roughness, epi-layer relaxation, and tilt. We find that gradual introduction of strain causes increased dislocation densities (>10{sup 6}/cm{sup 2}) and tilt of the epi-layer (>0.1°). A method of abrupt strain initiation is proposed which can result in dislocation densities as low as 1.01 × 10{sup 5} cm{sup −2} for films graded from the InP lattice constant to InAs{sub 0.15}P{sub 0.85}. A model for a two-energy level dislocation nucleation system is proposed based on our results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Anisotropic transport in modulation-doped quantum-well structures

Anisotropic electron transport has been observed in GaAs modulation-doped quantum wells grown by molecular-beam epitaxy on a thick (001) Al(0.3)Ga(0.7)As buffer grown at 620 C. Thicker quantum wells (150, 200, and 300 A) show progressively less anisotropy, which vanishes for a 300-A quantum well. The degree of anisotropy is also reduced or eliminated by suspending growth of the Al(0.3)Ga(0.7)As for a period of 300 s prior to growing the GaAs quantum well. Growing the Al(0.3)Ga(0.7)As buffer at higher temperatures (680 C) also reduces the degree of anisotropy. Higher two-dimensional electron gas sheet densities result in less anisotropy.The anisotropy is eliminated by replacing the thick Al(0.3)Ga(0.7)As buffer with a periodic multilayer structure comprising 15 A of GaAs and 200 A of Al(0.3)Ga(0.7)As. The degree of anisotropy is related to the thickness and growth parameters of the Al(0.3)Ga(0.7)As layer grown just prior to the growth of the GaAs.

Radulescu, D. C.↗
DOE OSTI2021

Mg x Zn 1−x O contact to CuGa 3 Se 5 absorber for photovoltaic and photoelectrochemical devices

Abstract CuGa 3 Se 5 is a promising candidate material with wide band gap for top cells in tandem photovoltaic and photoelectrochemical (PEC) devices. However, traditional CdS contact layers used with other chalcopyrite absorbers are not suitable for CuGa 3 Se 5 due to the higher position of its conduction band (CB) minimum. Mg x Zn 1− x O (MZO) is a transparent oxide with adjustable band gap and CB position as a function of magnesium composition, but its direct application is hindered by CuGa 3 Se 5 surface oxidation. Here, MZO is investigated as a contact (n-type ‘buffer’ or ‘window’) material to CuGa 3 Se 5 absorbers pretreated in Cd 2+ solution, and an onset potential close to 1 V vs reversible hydrogen electrode in 10 mM hexaammineruthenium (III) chloride electrolyte is demonstrated. The Cd 2+ surface treatment changes the chemical composition and electronic structure of the CuGa 3 Se 5 surface, as demonstrated by photoelectron spectroscopy measurements. The performance of CuGa 3 Se 5 absorber with Cd 2+ treated surface in the solid-state test structure depends on the Zn/Mg ratio in the MZO layer. The measured open circuit voltage of 925 mV is promising for tandem PEC water splitting with CuGa 3 Se 5 /MZO top cells.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electrochemical stability, physical, and electronic properties of thermally pre-formed oxide compared to artificially sputtered oxide on Fe thin films in aqueous chloride

Here the electrochemical stability and corrosion behavior of the thermally pre-oxidized and sputter deposited variant of an oxide single-crystalline Fe thin film were compared. Thermal oxides formed Fe 2 O 3 over an inner layer of Fe 3 O 4 while the sputtered oxides were found to have grown Fe 3 O 4 instead of the target stoichiometry of Fe 2 O 3 . Oxide films of both types were stable in pH=9.3 borate buffer solution, however, were altered in pH=9.3, 0.1 M NaCl solution in the case of thermally pre-oxidized Fe thin film. The stability of the oxide differed in pH=4, 0.1 M NaCl where sputtered Fe films were more stable against acidic chemical dissolution than the thermally formed Fe oxide film. These differences were traced by AC/DC electrochemical analysis including electronic defect densities, and molecular identity characterized by ex-situ X-ray photoelectron spectroscopy.

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

Significantly Improved Cyclability of Conversion-Type Transition Metal Oxyfluoride Cathodes by Homologous Passivation Layer Reconstruction

Electrode stabilization by surface passivation has been explored as the most crucial step to develop long-cycle lithium-ion batteries (LIBs). In this work, functionally graded materials consisting of “conversion-type” iron-doped nickel oxyfluoride (NiFeOF) cathode covered with a homologous passivation layer (HPL) are rationally designed for long-cycle LIBs. The compact and fluorine-rich HPL plays dual roles in suppressing the volume change of NiFeOF porous cathode and minimizing the dissolution of transition metals during LIBs cycling by forming a structure/composition gradient. The structure and composition of HPL reconstructs during lithiation/delithiation, buffering the volume change and trapping the dissolved transition metals. As a result, a high capacity of 175 mAh g -1 (equal to an outstanding volumetric capacity of 936 Ah L -1 ) with a greatly reduced capacity decay rate of 0.012% per cycle for 1000 cycles is achieved, which is superior to the NiFeOF porous film without HPL and commercially available NiF 2 -FeF 3 powders. Finally, the proposed chemical and structure reconstruction mechanism of HPL opens a new avenue for the novel materials development for long-cycle LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

SolAero 2020: III-V Metamorphic Graded Buffers (CRADA Final Report)

The effort by the National Renewable Energy Laboratory (NREL) for SolAero Technologies Corp (SolAero) will involve helping with four tasks: 1) Supporting the development, characterization, and optimization of metamorphic grades in III-V multi-junction solar cells, 2) Doping of III-V semiconductor materials and junctions, and 3) Incorporating strain balanced layers into solar cells, and 4) high efficiency germanium based solar cells.

14 SOLAR ENERGY↗
NASA NTRS1988

A fiber optic tactical voice/data network based on FDDI

An asynchronous high-speed fiber optic local area network is described that supports ordinary data packet traffic simultaneously with synchronous Tl voice traffic over a common FDDI token ring channel. A voice interface module was developed that parses, buffers, and resynchronizes the voice data to the packet network. The technique is general, however, and can be applied to any deterministic class of networks, including multi-tier backbones. A conventional single token access protocol was employed at the lowest layer, with fixed packet sizes for voice and variable for data. In addition, the higher layer packet data protocols are allowed to operate independently of those for the voice thereby permitting great flexibility in reconfiguring the network. Voice call setup and switching functions were performed external to the network with PABX equipment.

Bergman, L. A.↗
DOE OSTI2012

Characteristics of a cylindrical collector mirror for laser-produced xenon plasma soft X-rays and improvement of mirror lifetime by buffer gas

The focusing characteristics of a ruthenium-coated cylindrical mirror were investigated on the basis of its ability to collect and focus broadband 5-17-nm soft X-rays emitted from a laser-produced plasma. Based on the plasmas spectral intensity distribution and the reflectivity function of the mirror, we defined the optimum position of the integrated cylindrical mirror at which the X-ray energy flux transported and focused through the mirror was maximum. A minimum spot diameter of 22 mm at a distance of approximately 200 mm from a soft X-ray source was confirmed. The maximum intensity of the collected soft X-rays was 1.3 mJ/cm{sup 2} at the center of the irradiation zone. Thus, the irradiation intensity was improved by approximately 27 times when compared to that of 47 {mu}J/cm{sup 2} without the mirror. The debris sputtering rate on the reflection surface of the mirror can be reduced to 1/110 by argon gas at 11 Pa, while the attenuation rate of the soft X-rays due to absorption by the buffer gas can be suppressed to less than 10% at the focal point. The focusing property of the mirror is expected to be maintained for 3000 h or longer without significant degradation for a 100 W/320 pps laser shot if the ruthenium layer is thicker than 10 {mu}m. These results suggest that a stand-alone broadband soft X-ray processing system can be realized by using laser-produced plasma soft X-rays.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Bioaugmentation of an Engineered Metal Treatment Wetland with Cupriavidus SRS

There are many chemical methods to remediate copper (Cu) from the environment. However, the use of microorganisms has been identified to be cheaper and more efficient in remediating toxic compounds in a method known as bioremediation. A microorganism, Cupriavidus SRS, is a metal resistant, rod shaped, gram negative bacteria that was isolated from a location with heavy metal contamination. As a predator this isolate has the ability to attack gram-negative and gram-positive bacteria. It is highly tolerant to Cu, and the isolates growth initiation is stimulated by Cu. Wang et al. (2015) determined that efflux pump activity is one of the most important mechanisms of heavy metal tolerance and the Cupriavidus genus demonstrates this behavior. In this study, Cupriavidus SRS will be inoculated to sediment and water from an area with high concentrations of Cu and zinc, to determine the ability of the isolate to grow and survive in a high level Cu wetland as well as the bioremoval efficiency. The H-02 wetland in the AL1 outfall area is an engineered wetland that was constructed to utilize natural processes associated with sediments and microbial communities to remove contaminants from waste waters at the Savannah River Site. Specifically, this wetland treats the building processes and runoff form the Tritium Processing Facility in H-area to prevent Cu and Zn from entering the water before the contaminants go in the Savannah River. Distributions of Cu and Zn follow organic matter levels with higher densities along the shoreline showing that metal concentrations correlate with organic matter content. Cupriavidus SRS Growth: Cupriavidus SRS was isolated at the Savannah River Site from an area with heavy metal contamination. Cultures were grown in R2A medium at 25 deg. C and shaken at 80 rpm for liquid cultures for 5 days. Sediment and Water Collection: All samples were collected from the AL1 Outfall area within the Department of Energy's Savannah River Site. Sediment cores, organic layer samples, and water samples were collected from the Inlet and Outlet cells in triplicate. Only water samples were collected from the basin. Cell Pellet: After centrifugation at 10,000 RPM for 10 minutes the supernatant was removed. 1 mL of phosphate buffer saline was added to the tube, vortexed, and recentrifuged. Inoculation of Sediment and Water: All samples were done in triplicate, vortexed after inoculation, and put on the shaker for 72 hours. Day 0 begins when the samples are removed from the shaker. Experimental Set-Up: All samples were done in triplicate. All sediment samples were centrifuged at 7500 RPM for 10 minutes on Day 0 and Day 5. All the sediment and water samples were filtered with a 0.2 μm nylon filters to obtain approximately 10 mL of supernatant on Day 0 and Day 3. pH was taken 24, 48, and 72 hours after the samples had been on the shaker. Plate Count: Plate counts were done on Day 0 and Day 3 to determine Cupriavidus SRS growth following a quantitative counting method from Seely et al. (1972). This project is ongoing and the goal is to determine if Cupriavidus SRS has the ability to uptake excess Cu out of the environment. These could be some possible results for the experiment: - The isolate uptakes too much Cu, dies, and releases Cu back into the environment. - The isolate is able to uptake Cu, continue to live, but chemically changes the environment introducing new problems. - The isolate is able to uptake Cu, continue to live, and does not disrupt the environment with toxic chemical changes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗