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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Tunable Dielectric Materials and Devices for Broadband Wireless Communications

Wireless and satellite communications are a rapidly growing industries which are slated for explosive growth into emerging countries as well as countries with advanced economies. The dominant trend in wireless communication systems is towards broadband applications such as multimedia file transfer, video transmission and Internet access. These applications require much higher data transmission rates than those currently used for voice transmission applications. To achieve these higher data rates, substantially larger bandwidths and higher carrier frequencies are required. A key roadblock to implementing these systems at K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) is the need to develop hardware which meets the requirements for high data rate transmission in a cost effective manner. In this chapter, we report on the status of tunable dielectric thin films for devices, such as resonators, filters, phased array antennas, and tunable oscillators, which utilize nonlinear tuning in the control elements. Paraelectric materials such as Barium Strontium Titanate ((Ba, Sr)TiO3) have dielectric constants which can be tuned by varying the magnitude of the electric field across the material. Therefore, these materials can be used to control the frequency and/or phase response of various devices such as electronically steerable phased array antennas, oscillators, and filters. Currently, tunable dielectric devices are being developed for applications which require high tunability, low loss, and good RF power-handling capabilities at microwave and millimeter-wave frequencies. These properties are strongly impacted by film microstructure and device design, and considerable developmental work is still required. However, in the last several years enormous progress has occurred in this field, validating the potential of tunable dielectric technology for broadband wireless communication applications. In this chapter we summarize how film processing techniques, microwave test configurations, and prototype devices have combined to drive the field to its current stage of development.

Mueller, Carl H.↗
NASA NTRS2002

Multi-junction Thin-film Solar Cells on Flexible Substrates for Space Power

The ultimate objective of the thin-film program at NASA GRC is development of a 20 percent AM0 thin-film device technology with high power/weight ratio. Several approaches are outlined to improve overall device efficiency and power/weight ratio. One approach involves the use of very lightweight flexible substrates such as polyimides (i.e., Kapton(Trademark)) or metal foil. Also, a compound semiconductor tandem device structure that can meet this objective is proposed and simulated using Analysis of Microelectronic and Photonic Structures (AMPS). AMPS modeling of current devices in tandem format indicate that AM0 efficiencies near 20 percent can be achieved. And with improvements in materials, efficiencies approaching 25 percent are achievable. Several important technical issues need to be resolved to realize these complex devices: development of a wide bandgap material with good electronic properties, development of transparent contacts, and targeting a 2-terminal device structure (with more complicated processing and tunnel junction) or 4-terminal device. Recent progress in the NASA GRC program is outlined.

Hepp, Aloysius F.↗
NASA NTRS2012

Satellite Ocean Biology: Past, Present, Future

Since 1978 when the first satellite ocean color proof-of-concept sensor, the Nimbus-7 Coastal Zone Color Scanner, was launched, much progress has been made in refining the basic measurement concept and expanding the research applications of global satellite time series of biological and optical properties such as chlorophyll-a concentrations. The seminar will review the fundamentals of satellite ocean color measurements (sensor design considerations, on-orbit calibration, atmospheric corrections, and bio-optical algorithms), scientific results from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate resolution Imaging Spectroradiometer (MODIS) missions, and the goals of future NASA missions such as PACE, the Aerosol, Cloud, Ecology (ACE), and Geostationary Coastal and Air Pollution Events (GeoCAPE) missions.

McClain, Charles R.↗
NASA NTRS2014

Boron Nitride Nanotube: Synthesis and Applications

Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800 C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

Tiano, Amanda L.↗
DOE OSTI2017

Steam Corrosion Investigation of Single Silicon Carbide Nanostructures

Silicon carbide (SiC) has been advanced as an alternative to zircaloy for use as an accident-tolerant fuel cladding material in next-generation water-cooled reactors. This is due, in large part, to the predicted superior corrosion resistance of SiC, as compared to zircaloy, particularly at the high temperatures that are obtained in a nuclear reactor under accident conditions. The other favorable performance metrics of SiC include its enhanced mechanical stability, low neutron absorption, low chemical reactivity, and high radiation stability. Past reports, which include theoretical and isolated experimental activities, have studied the corrosion of bulk-scale SiC in reactor-like conditions. This report will present high-temperature steam corrosion results from single SiC nanofiber-based constructs. The changes in microstructure, and the evolution of oxide thickness and SiC recession with progressive corrosion will be characterized at the atomic-to-nanoscale using transmission electron microscopy (TEM). Furthermore, the corrosion-induced degradation in mechanical properties of the SiC nanofibers will be characterized using three-point bending tests involving an atomic-force microscope (AFM) in the contact mode.

36 MATERIALS SCIENCE↗
NASA NTRS1996

Design of intelligent mesoscale periodic array structures utilizing smart hydrogel

Mesoscale Periodic Array Structures (MPAS, also known as crystalline colloidal arrays), composed of aqueous or nonaqueous dispersions of self-assembled submicron colloidal spheres are emerging toward the development of advanced optical devices for technological applications. This is because of their unique optical diffraction properties and the ease with which these intriguing properties can be modulated experimentally. Moreover our recent advancements in this area which include 'locking' the liquid MPAS into solid or semisolid polymer matrices for greater stability with longer life span, and incorporation of CdS quantum dots and laser dyes into colloidal spheres to obtain nonlinear optical (NLO) responses further corroborate the use of MPAS in optical technology. Our long term goal is fabrication of all-optical and electro-optical devices such as spatial light modulators for optical signal processing and flat panel display devices by utilizing intelligent nonlinear periodic array structural materials. Here we show further progress in the design of novel linear MPAS which have the ability to sense and respond to an external source such as temperature. This is achieved by combining the self-assembly properties of polymer colloidal spheres and thermoshrinking properties of smart polymer gels. At selected temperatures the periodic array efficiently Bragg diffracts light and transmits most of the light at other temperatures. Hence these intelligent systems are of potential use as fixed notch filters optical switches or limiters to protect delicate optical sensors from high intensity laser radiation.

Sunkara, H. B.↗
NASA NTRS2008

Predicting Properties of Unidirectional-Nanofiber Composites

A theory for predicting mechanical, thermal, electrical, and other properties of unidirectional-nanofiber/matrix composite materials is based on the prior theory of micromechanics of composite materials. In the development of the present theory, the prior theory of micromechanics was extended, through progressive substructuring, to the level of detail of a nanoscale slice of a nanofiber. All the governing equations were then formulated at this level. The substructuring and the equations have been programmed in the ICAN/JAVA computer code, which was reported in "ICAN/JAVA: Integrated Composite Analyzer Recoded in Java" (LEW-17247), NASA Tech Briefs, Vol. 26, No. 12 (December 2002), page 36. In a demonstration, the theory as embodied in the computer code was applied to a graphite-nanofiber/epoxy laminate and used to predict 25 properties. Most of the properties were found to be distributed along the through-the-thickness direction. Matrix-dependent properties were found to have bimodal through-the-thickness distributions with discontinuous changes from mode to mode.

Chamis, Christos C.↗
DOE OSTI2017

Research Progress towards Understanding the Unique Interfaces between Concentrated Electrolytes and Electrodes for Energy Storage Applications

The electrolyte is an indispensable component in all electrochemical energy storage and conversion devices with batteries being a prime example. While most research efforts have been pursued on the materials side, the progress for the electrolyte is slow due to the decomposition of salts and solvents at low potentials, not to mention their complicated interactions with the electrode materials. The general properties of bulk electrolytes such as ionic conductivity, viscosity, and stability all affect the cell performance. However, for a specific electrochemical cell in which the cathode, anode, and electrolyte are optimized, it is the interface between the solid electrode and the liquid electrolyte, generally referred to as the solid electrolyte interphase (SEI), that dictates the rate of ion flow in the system. The commonly used electrolyte is within the range of 1–1.2 m based on the prior optimization experience, leaving the high concentration region insufficiently recognized. Recently, electrolytes with increased concentration (>1.0 m ) have received intensive attention due to quite a few interesting discoveries in cells containing concentrated electrolytes. The formation mechanism and the nature of the SEI layers derived from concentrated electrolytes could be fundamentally distinct from those of the traditional SEI and thus enable unusual functions that cannot be realized using regular electrolytes. In this article, we provide an overview on the recent progress of high concentration electrolytes in different battery chemistries. The experimentally observed phenomena and their underlying fundamental mechanisms are discussed. New insights and perspectives are proposed to inspire more revolutionary solutions to address the interfacial challenges.

25 ENERGY STORAGE↗
DOE OSTI2023

Conducting Polymers Meet Lithium–Sulfur Batteries: Progress, Challenges, and Perspectives

Lithium–sulfur (Li–S) batteries have attracted increased interest because of the high theoretical energy density, low cost, and environmental friendliness. Conducting polymers (CPs), as one of the most promising materials used in Li–S batteries, can not only facilitate electron transfer and buffer the large volumetric change of sulfur benefiting from their porous structure and excellent flexibility, but also enable stronger physical/chemical adsorption capacity toward polysulfides (LiPSs) when doped with abundant heteroatoms to promote the sulfur redox kinetics and achieve the high sulfur loading. This review firstly introduces the properties of various CPs including structural CPs (polypyrrole (PPy), polyaniline (PANi), polyethylene dioxothiophene [PEDOT]) and compound CPs (polyethylene oxide (PEO), polyvinyl alcohol (PVA) and poly(acrylic acid) [PAA]), and their application potential in Li–S batteries. Furthermore, the research progress of various CPs in different components (cathode, separator, and interlayer) of Li–S batteries is systematically summarized. Finally, the application perspective of the CPs in Li–S batteries as a potential guidance is comprehensively discussed.

Chen, Xin↗
DOE OSTI2017

Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends between each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.

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

KDHE POroject Code: C6-074-00002: Progress and Monitoring Report for the LBD/SVE/AS System at the Former CCC/USDA Grain Storage Facility, Agra, Kansas, in January-June 2016

In 2008-2009, to address the carbon tetrachloride contamination detected on its former property, the CCC/USDA implemented a source area cleanup in accord with the document Interim Measure Work Plan/Design for Agra, Kansas (IMWP/D; Argonne 2008). The cleanup involves five large-diameter boreholes (LDBs) coupled with soil vapor extraction (SVE) and air sparge (AS) systems. The work plan was approved by the Kansas Department of Health and Environment (KDHE) in November 2008 (KDHE 2008b), and operation began in May 2009.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1984

Progress in the study of homologous flares on the sun. II

Studies of groups of homologous flares in active regions in 1980 were performed using a variety of space and ground-based instruments. The properties of three of the groups are described and combined to form a possible sequence of events.

Woodgate, B. E.↗
DOE OSTI2017

Study of the Few Nucleon Systems at $\mathrm{CLAS}$

The study of few nucleon systems with electromagnetic probes is an essential component of the scientific program carried out at the Thomas Jefferson National Accelerator Facility (JLab). Here we present measurements of exclusive reactions on light nuclei using real photon beams with energies up to 3 GeV and the CEBAF Large Acceptance Spectrometer (CLAS), a nearly 4π magnetic spectrometer, in order to study the properties of strongly interacting matter and the transition from hadronic (i.e in terms of nucleons and mesons) to partonic (in terms of quark and gluons) degrees of freedom in nuclear interactions. We discuss the progress made in understanding the relevant degrees of freedom using polarisation observables and cross sections of deuteron and 3 He photodisintegration in the few-GeV photon-energy region. In addition, recent high-statistics experiments with the CLAS detector have provided us with sufficient counting rates to study the effects of initial- and final-state interactions in reactions off the deuteron. Such data allow us to extract a large set of polarisation observables for final-state interactions in hyperon photoproduction and to study the properties of the hyperon–nucleon interaction. Initial-state effects are studied by mapping the dependence of experimental observables on the spectator-nucleon momentum. We also present recent results for polarisation observables for quasi-free K + Λ off the bound proton in a deuteron as well as for final-state interactions in the reaction γd→K + Λn , and will discuss their impact on hyperon–nucleon studies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Dystonia-4 (DYT4)-associated TUBB4A mutants exhibit disorganized microtubule networks and inhibit neuronal process growth

Highlights: • Dystonia-4-associated TUBB4A mutants (R2G) exhibit disorganized tubulin networks. • Dystonia-4-associated TUBB4A mutants (A271T) exhibit disorganized tubulin networks. • Dystonia-4-associated mutants have diminished ability to interact with alpha-type tubulins. • Dystonia-4-associated mutants show inhibited neurite growth in a neuronal cell line. Dystonia-1 (DYT1) is an autosomal dominant early-onset torsion form of dystonia, a neurological disease affecting movement. DYT1 is the prototypic hereditary dystonia and is caused by the mutation of the tor1a gene. The gene product has chaperone functions important for the control of protein folding and stability. Dystonia-4 (DYT4) is another autosomal dominant dystonia that is characterized by onset in the second to third decade of progressive laryngeal dysphonia. DYT4 is associated with the mutation of the tubb4a gene, although it remains to be understood how disease-associated mutation affects biochemical as well as cell biological properties of the gene product as the microtubule component (a tubulin beta subunit). Herein we demonstrate that DYT4-associated TUBB4A missense mutants (Arg2-to-Gly or Ala271-to-Thr) form disorganized tubulin networks in cells. Transfected mutants are indeed expressed in cytoplasmic regions, as observed in wild-type transfectants. However, mutant proteins do not exhibit typical radial tubulin networks. Rather, they have diminished ability to interact with tubulin alpha subunits. Processes do not form in sufficient amounts in cells of the N1E-115 neuronal cell line expressing each of these mutants as compared to parental cells. Together, DYT4-associated TUBB4A mutants themselves form aberrant tubulin networks and inhibit neuronal process growth, possibly explaining progress through the pathological states at cellular levels.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2008

Coronal Heating and the Need for High-Resolution Observations

Despite excellent progress in recent years in understanding coronal heating, there remain many crucial questions that are still unanswered. Limitations in the observations are one important reason. Both theoretical and observational considerations point to the importance of small spatial scales, impulsive energy release, strong dynamics, and extreme plasma nonuniformity. As a consequence, high spatial resolution, broad temperature coverage, high temperature fidelity, and sensitivity to velocities and densities are all critical observational parameters. Current instruments lack one or more of these properties, and this has led to considerable ambiguity and confusion. In this talk, I will discuss recent ideas about coronal heating and emphasize that high spatial resolution observations, especially spectroscopic observations, are needed to make major progress on this important problem.

Klimchuk, James A.↗
DOE OSTI2017

Ionic liquids: Promising green solvents for lignocellulosic biomass utilization

Ionic liquids are effective solvents/media for the utilization of lignocellulosic biomass. The unique properties of ionic liquids enable them to effectively dissolve and/or convert the biomass into various types of products. This review aims to cover the latest progress achieved in applications of ionic liquids on biomass conversion and analysis. Specifically, several recently developed approaches on how to overcome current challenges on the use of ionic liquids in the biomass conversion were highlighted. Here, recent studies addressing the potential applications of ionic liquids for the production of novel biomass-derived chemicals and materials were also discussed.

09 BIOMASS FUELS↗
DOE OSTI2020

Electrocatalytic CO 2 Reduction to Fuels: Progress and Opportunities

The electrochemical reduction of CO 2 continues to be an appealing option for storing renewable energy in a chemical form. In this review, we assess progress in designing catalysts that convert CO 2 to high energy density products. We explain how reaction data can be reported to reflect the intrinsic properties of the catalyst. This analysis shows that limited advances have been made in improving the performance of Cu. We suggest that opportunities remain using bimetallic catalysts that are resistant to dealloying. While aqueous systems are instrumental to developing our understanding of this chemistry, gas-fed systems that operate at high current densities must be developed. Although obstacles remain for practical application of CO 2 reduction, advances in fundamental understanding made over the years give reason for optimism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗