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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Superior Performance of a Lithium-Sulfur Battery Enabled by a Dimethyl Trisulfide Containing Electrolyte

The lithium-sulfur (Li-S) battery offers a high theoretical energy density of ≈2600 Wh/kg -1 and low cost, positioning it as a promising candidate for next-generation battery technology. However, problems including disastrous Li polysulfides dissolution and irreversible Li 2 S deposition have severely retarded the development of Li-S batteries. To solve these issues, we recently reported a functional dimethyl disulfide (DMDS)-containing electrolyte that promoted an alternate electrochemical reaction pathway for sulfur cathodes by a formation of dimethyl polysulfides and Li organosulfides as intermediates and reduction products, leading to significantly boosted Li-S cell capacity with improved cycling reversibility and stability. Here in this work, dimethyl trisulfide (DMTS), a primary discharge-charge intermediate in the DMDS-containing electrolyte, which is also a commercially available reagent, was further investigated as a co-solvent in functional electrolytes for Li-S batteries. Due to the higher theoretical capacity of DMTS and its better reactivity with Li 2 S than DMDS, a 25 vol% DMTS-containing electrolyte enables Li-S batteries with even higher cell capacity and improved cycling performance than using previous optimal 50 vol% DMDS-containing electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2011

A Novel Non-Platinum Group Electrocatalyst for PEM Fuel Cell Application

Precious-metal catalysts (predominantly Pt or Pt-based alloys supported on carbon) have traditionally been used to catalyze the electrode reactions in polymer electrolyte membrane (PEM) fuel cells. However as PEM fuel systems begin to approach commercial reality, there is an impending need to replace Pt with a lower cost alternative. The present study investigates the performance of a carbon-supported tantalum oxide material as a potential oxygen reduction reaction (ORR) catalyst for use on the cathode side of the PEM fuel cell membrane electrode assembly. Although bulk tantalum oxide tends to exhibit poor electrochemical performance due to limited electrical conductivity, it displays a high oxygen reduction potential; one that is comparable to Pt. Analysis of the Pourbaix electrochemical equilibrium database also indicates that tantalum oxide (Ta2O5) is chemically stable under the pH and applied potential conditions to which the cathode catalyst is typically exposed during stack operation. Nanoscale tantalum oxide catalysts were fabricated using two approaches, by reactive oxidation sputtering and by direct chemical synthesis, each carried out on a carbon support material. Nanoscale tantalum oxide particles measuring approximately 6nm in size that were sputtered onto carbon paper exhibited a mass-specific current density as high as one-third that of Pt when measured at 0.6V vs. NHE. However because of the two-dimensional nature of this particle-on-paper structure, which limits the overall length of the triple phase boundary junctions where the oxide, carbon paper, and aqueous electrolyte meet, the corresponding area-specific current density was quite low. The second synthesis approach yielded a more extended, three-dimensional structure via chemical deposition of nanoscale tantalum oxide particles on carbon powder. These catalysts exhibited a high ORR onset potential, comparable to that of Pt, and displayed a significant improvement in the area-specific current density. Overall, the highest mass-specific current density of the carbon-powder supported catalyst was ~ 9% of that of Pt.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

High capacity of lithium-sulfur batteries at low electrolyte/sulfur ratio enabled by an organosulfide containing electrolyte

We present that lithium-sulfur (Li-S) battery is a promising energy storage technology to replace lithium ion batteries for higher energy density and lower cost. Dissolution of lithium polysulfide intermediates in conventional Li-S electrolytes is known as one of the key technical barriers to the development of Li-S, because it promotes redistribution and irreversible deposition of Li 2 S, and also forces large amounts of electrolyte to be used, shortening cycling life and driving down cell energy density. Recently, dimethyl disulfide as a functional co-solvent has been demonstrated to show an alternate electrochemical reaction pathway for sulfur cathodes by the formation of dimethyl polysulfides and lithium organosulfides as intermediates and reduction products. In this work, comprehensive studies show that this new pathway not only provides high capacity but also enables excellent capacity retention through a built-in automatic discharge shutoff mechanism by tuning carbon/sulfur ratio in sulfur cathodes to reduce unfavorable Li 2 S formation. Furthermore, this new electrolyte system is also found to enable high capacity of high-sulfur-loading cathodes with low electrolyte/sulfur (E/S) ratios, such as a stable specific capacity of around 1000 mAh g -1 using a low electrolyte amount (i.e, E/S ratio of 5 mL g -1 ) and highsulfur-loading (4 mg cm -2 ) cathodes. This electrolyte system almost doubles the capacity obtained with conventional electrolytes under the same harsh conditions. In conclusion, these results highlight the practical potential of this electrolyte system to enable high-energy-density Li-S batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Use of Ionic Liquids for Hemp Fiber Degumming

Degumming or retting to remove pectin, lignin, and hemicellulose is a critical step in the production of high-quality hemp fibers. Current technologies, including traditional water or dew retting, as well as chemical, enzymatic, and physical degumming processes, have inherent environmental risks and produce fibers of varying qualities. Herein we explore the use of an ionic liquid (IL) capable of dissolving pectin, lignin, and hemicellulose, but not cellulose, in combination with different oxidating agents to degum hemp. In this study, we observed that treating raw hemp fibers with the IL choline acetate ([Cho][OAc]), alone or in combination with aqueous H 2 O 2 , led to a reduction in the gummy materials and lignin content of the resulting samples of up to 63 and 78%, respectively. More importantly, the high crystallinity and low reduction in tensile strength of the resulting fibers make these novel and relatively simple IL-based processes promising alternatives toward the sustainable preparation of hemp-based materials suitable for use in the textile industry.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Scale-up of the production of highly reactive biogenic magnetite nanoparticles using Geobacter sulfurreducens

Although there are numerous examples of large-scale commercial microbial synthesis routes for organic bioproducts, few studies have addressed the obvious potential for microbial systems to produce inorganic functional biomaterials at scale. Here we address this by focusing on the production of nanoscale biomagnetite particles by the Fe(III)-reducing bacterium Geobacter sulfurreducens , which was scaled up successfully from laboratory- to pilot plant-scale production, while maintaining the surface reactivity and magnetic properties which make this material well suited to commercial exploitation. At the largest scale tested, the bacterium was grown in a 50 l bioreactor, harvested and then inoculated into a buffer solution containing Fe(III)-oxyhydroxide and an electron donor and mediator, which promoted the formation of magnetite in under 24 h. This procedure was capable of producing up to 120 g of biomagnetite. The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI). The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities.

Science & Technology - Other Topics↗
DOE OSTI2010

Fast, low-dose patient localization on TomoTherapy via topogram registration

Purpose: To investigate a protocol which efficiently localizes TomoTherapy patients with a scout imaging (topogram) mode that can be used with or instead of 3D megavoltage computed tomography (MVCT) imaging. Methods: The process presented here is twofold: (a) The acquisition of the topogram using the TomoTherapy MV imaging system and (b) the generation of a digitally reconstructed topogram (DRT) derived from a standard kV CT simulation data set. The unique geometric characteristics of the current TomoTherapy imaging system were explored both theoretically and by acquiring topograms of anthropomorphic phantoms and comparing these images to DRT images. The performance of the MV topogram imaging system in terms of image quality, dose incurred to the patient, and acquisition time was investigated using ionization chamber and radiographic film measurements. Results: The time required to acquire a clinically usable topogram, limited by the maximum couch speed of 4.0 cm s{sup -1}, was 12.5 s for a 50 cm long field. The patient dose was less than 1% of that delivered by a helical MVCT scan. Further refinements within the current TomoTherapy system, most notably decreasing the imaging beam repetition rate during MV topogram acquisition, would further reduce the topogram dose to less than 25 {mu}Gy per scan without compromising image quality. Conclusions: Topogram localization on TomoTherapy is a fast and low-dose alternative to 3D MVCT localization. A protocol designed that exclusively utilized MV topograms would result in a 30-fold reduction in imaging time and a 100-fold reduction in dose from localization scans using the current TomoTherapy workflow.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

Laser Ablation for Low-Cost Multijunction III-V Solar Cell Mesa Isolations

Eliminating photolithography from solar cell processing is a significant opportunity for cost reduction for III-V solar cells. In this work, we test femtosecond laser ablation and scribing as an alternative to contact photolithography and wet chemical etching for mesa isolation, when processing multijunction cells. We demonstrate that upright multijunction solar cells isolated by using the laser as a scribe to cleave through the substrate had virtually no performance loss when compared to a baseline cell processed with photolithography. By contrast, cells isolated by laser ablating through the active layers have performance losses that cannot be fully eliminated with post-processing etches. This demonstration of photolithography-free mesa isolation with no performance losses is promising for less expensive III-V manufacturing.

14 SOLAR ENERGY↗
NASA NTRS1973

Effect of fuel zoning and fuel nozzle design on pollution emissions at ground idle conditions for a double-annular ram-induction combustor

An exhaust emission survey was conducted on a double-annular ram induction combustor at simulated ground idle conditions. The combustor was designed for a large augmented turbofan engine capable of sustained flight speeds up to Mach 3.0. The emission levels of total hydrocarbon (THC), carbon monoxide, carbon dioxide, and nitric oxide were measured. The effects of fuel zoning, fuel nozzle design, and operating conditions (inlet temperature and reference Mach number) on the level of these emissions were determined. At an overall combustor fuel/air ratio of 0.007, fuel zoning reduced THC emissions by a factor of 5 to 1. The reduction in THC emissions is attributed to the increase in local fuel/air ratio provided by the fuel zoning. An alternative method of increasing fuel/air ratio would be to operate with larger-than-normal compressor overboard bleed; however, analysis on this method indicated an increase in idle fuel consumption of 20 percent. The use of air-atomizing nozzles reduced the THC emissions by 2 to 1.

Clements, T. R.↗
NASA NTRS1984

Computer vision for real-time orbital operations. Center directors discretionary fund

Machine vision research is examined as it relates to the NASA Space Station program and its associated Orbital Maneuvering Vehicle (OMV). Initial operation of OMV for orbital assembly, docking, and servicing are manually controlled from the ground by means of an on board TV camera. These orbital operations may be accomplished autonomously by machine vision techniques which use the TV camera as a sensing device. Classical machine vision techniques are described. An alternate method is developed and described which employs a syntactic pattern recognition scheme. It has the potential for substantial reduction of computing and data storage requirements in comparison to the Two-Dimensional Fast Fourier Transform (2D FFT) image analysis. The method embodies powerful heuristic pattern recognition capability by identifying image shapes such as elongation, symmetry, number of appendages, and the relative length of appendages.

Vinz, F. L.↗
NASA NTRS1988

The influence of high thermal gradient casting, hot isostatic pressing and alternate heat treatment on the structure and properties of a single crystal nickel base superalloy

A development program has been conducted to improve the cyclic properties of the PWA 1480 single-crystal superalloy by reducing or entirely eliminating casting porosity at fatigue-initiation sites, through the use of improved casting process parameters and HIPing; potential mechanical property improvements in a high-pressure hydrogen environment were also sought in alternatives to the standard coating and heat-treatment cycle. High thermal gradient casting was found to yield a reduction in overall casting porosity density and pore sizes. The most dramatic mechanical property improvement resulted from HIPing.

Fritzemeier, L. G.↗
NASA NTRS1991

Functional models of power electronic components for system studies

A novel approach to model power electronic circuits has been developed to facilitate simulation studies of system-level issues. The underlying concept for this approach is to develop an equivalent circuit, the functional model, that performs the same functions as the actual circuit but whose operation can be simulated by using larger time step size and the reduction in model complexity, the computation time required by a functional model is significantly shorter than that required by alternative approaches. The authors present this novel modeling approach and discuss the functional models of two major power electronic components, the DC/DC converter unit and the load converter, that are being considered by NASA for use in the Space Station Freedom electric power system. The validity of these models is established by comparing the simulation results with available experimental data and other simulation results obtained by using a more established modeling approach. The usefulness of this approach is demonstrated by incorporating these models into a power system model and simulating the system responses and interactions between components under various conditions.

Tam, Kwa-Sur↗
NASA NTRS1995

Rechargeable Magnesium Power Cells

Rechargeable power cells based on magnesium anodes developed as safer alternatives to high-energy-density cells like those based on lithium and sodium anodes. At cost of some reduction in energy density, magnesium-based cells safer because less susceptible to catastrophic meltdown followed by flames and venting of toxic fumes. Other advantages include ease of handling, machining, and disposal, and relatively low cost.

Koch, Victor R.↗
NASA NTRS2011

Design and Implementation of a Mechanical Control System for the Scanning Microwave Limb Sounder

The Scanning Microwave Limb Sounder (SMLS) will use technological improvements in low noise mixers to provide precise data on the Earth's atmospheric composition with high spatial resolution. This project focuses on the design and implementation of a real time control system needed for airborne engineering tests of the SMLS. The system must coordinate the actuation of optical components using four motors with encoder readback, while collecting synchronized telemetric data from a GPS receiver and 3-axis gyrometric system. A graphical user interface for testing the control system was also designed using Python. Although the system could have been implemented with a FPGA-based setup, we chose to use a low cost processor development kit manufactured by XMOS. The XMOS architecture allows parallel execution of multiple tasks on separate threads-making it ideal for this application and is easily programmed using XC (a subset of C). The necessary communication interfaces were implemented in software, including Ethernet, with significant cost and time reduction compared to an FPGA-based approach. For these reasons, the XMOS technology is an attractive, cost effective, alternative to FPGA-based technologies for this design and similar rapid prototyping projects.

Mars Science Laboratory Robotics↗
NASA NTRS2019

Transparent Conducting Oxides as Cathodes in Li-O2 Batteries: A First Principles Computational Investigation

Li-O2 batteries have traditionally used carbon based electrodes (graphite, buckypaper) as the cathode of choice due toits good electrical conductivity, stability against non-aqueous electrolytes like dimethoxyethane (DME) and ease ofhandling. But, the carbon cathode also leads to formation of carbonate by-products that increase overpotentials duringcharging leading to degradation of the cathode and reduction of cyclability. Recent investigations have focused on using metal-oxides like SnO2, TiO2 as viable cathodes-alternatives in Li-O2 systems. In this paper, we investigate transparent conducting oxides (TCOs) as cathodes with focus on the interface between the TCO surfaces and the discharge product, Li2O2, in the Li-O2 battery using first principles computations.

transparent conducting oxides↗
DOE OSTI2025

Development of Biological and Electrochemical Technologies for the Clean Extraction of Copper and Critical Materials from Low Grade Ores

As we transition toward renewable energy resources and electrification, there will be an increasing demand for critical materials, including copper. While copper is currently mined in the US, processing capacity is not sufficient, and intermediate mining products are shipped to Asia for further processing. The goal of this research was to develop a transformative hydrometallurgical process for the production of copper from low-grade ores that would eliminate the need for smelting and would increase the domestic processing capacity in the US, The project initially focused on the electrochemical reduction of copper concentrate using vanadium, followed by the biological oxidation to produce a stream compatible with existing solvent extraction and electrowinning operations. We discovered an efficient electrochemical process that could produce copper salts from concentrate without the need for biological oxidation, and this technology has been licensed and spun-off into a start-up company. The microbes involved in the current state-of-the-art bioleaching processes were genetically modified to introduced a number of new traits, including increased sulfur oxidation, salt-tolerance, and binding of other critical metals such as cobalt, molybdenum, rhenium, and the rare earth elements. The project was extended to also explore the electrochemical oxidation of copper concentrate using cerium which would potentially eliminate production of hydrogen sulfide that occurs with the reductive leaching process. This technology was found to have slower kinetics, however could it still be developed as an alternative process for domestic copper production and has been found to be applicable to other critical minerals.

42 ENGINEERING↗
DOE OSTI2017

Drought impacts on photosynthesis, isoprene emission and atmospheric formaldehyde in a mid-latitude forest

Isoprene plays a critical role in air quality and climate. Photosynthesis (gross primary productivity, GPP) and formaldehyde (HCHO) are both related to isoprene emission at large spatiotemporal scales, but neither is a perfect proxy. Here we apply multiple satellite products and site-level measurements to examine the impact of water deficit on the three interlinked variables at the Missouri Ozarks site during a 20-day mild dryness stress in summer 2011 and a 3-month severe drought in summer 2012. Isoprene emission shows opposite responses to the short- and long-term droughts, while GPP was substantially reduced in both cases. In 2012, both remote-sensed solar-induced fluorescence (SIF) and satellite HCHO column qualitatively capture reductions in flux-derived GPP and isoprene emission, respectively, on weekly to monthly time scales, but with muted responses. For instance, as flux-derived GPP approaches zero in late summer 2012, SIF drops by 29–33% (July) and 19–27% (August) relative to year 2011. A possible explanation is that electron transport and photosystem activity are maintained to a certain extent under the drought stress. Similarly, flux tower isoprene emissions in July 2012 are 54% lower than July 2011, while the relative reductions in July for 3 independent satellite-derived HCHO data products are 27%, 12% and 6%, respectively. Finally, we attribute the muted HCHO response to a photochemical feedback whereby reduced isoprene emission increases the oxidation capacity available to generate HCHO from other volatile organic compound sources. Satellite SIF offers a potential alternative indirect method to monitor isoprene variability at large spatiotemporal scales from space, although further research is needed under different environmental conditions and regions. Our analysis indicates that fairly moderate reductions in satellite SIF and HCHO column may imply severe drought conditions at the surface.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Low temperature dry reforming of methane using Ru-Ni-Mg/ceria-zirconia catalysts: Effect of Ru loading and reduction temperature

Dry reforming catalysts, especially those with activity at moderate temperatures, have been intensely investigated to enhance the conversion of biogas. Here, Ru is evaluated as a promoter for Ni-Mg based catalysts. Catalysts based on 1.4 wt%Ni-1.0 wt%Mg-Ce 0.6 Zr 0.4 O 2 with Ru (0.02–0.32 wt%) were prepared using incipient wetness. The reducibility of the catalysts and conversions increased with increasing Ru content. Increases in conversions with increasing Ru loading was attributed to the additional active sites and synergistic effect between Ru and Ni, which weakened Ni-Mg interactions. Samples showed dry reforming activity at low temperatures (450–510 °C). Reaction rates and activation energies of higher loading Ru samples (1.4 wt%Ni-1.0 wt%Mg/Ce 0.6 Zr 0.4 O 2 with 0.16 and 0.32 wt%Ru) decreased when the reduction temperature was raised from 300 to 400 °C. A 20 h TOS study showed stable catalytic activity with minimal coke deposition. Furthermore, the results suggest that Ru is an alternative to Pt in promoting low temperature dry reforming of methane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Alternating salt and freshwater floods of coastal soils impact soil structure, hydraulic properties, and oxygen dynamics

Coastal soils are increasingly impacted by hydrologic intensification in the form of rising sea level and flooding from storm surges and precipitation. Alternating saltwater (SW) and freshwater (FW) exposure has the potential to disperse colloids, which can lead to disintegration of soil structure, clogging of pore spaces, and reduction in ecologically and biogeochemically important functions like infiltration or gas exchange. To investigate how hydrologic intensification affects soil structure and oxygen dynamics, we conducted a series of laboratory-based flood simulations. Intact soil cores of the A and B horizons (22 total) from the toe slope of an upland coastal forest along the western shore of Chesapeake Bay. We subjected the cores to 24 h of saturation with either FW or alternating brackish SW and FW, with a 24-h draining event in between flood events. Oxygen diffusion into soil during draining was reduced by up to 30% for soils flooded alternating SW-FW compared to soils flooded only with FW. We attributed the reduced oxygen diffusion to clogging of smaller pores by colloids, with colloid redistribution observed as an increase in specific surface area down the core profile of up to 59%. After three SW-FW floods (six floods total), there were significant changes in pore size distribution, significant redistribution of colloids, and the A horizon became sodic. We concluded that a small number of SW flooding events can induce a measurable change in soil physical properties that directly impacts the biogeochemical dynamics.

Rod, Kenton A. [Pacific Northwest National Laborat↗