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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 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Gallium phosphide optical metasurfaces for visible light applications

There are few materials that are broadly used for fabricating optical metasurfaces for visible light applications. Gallium phosphide (GaP) is a material that, due to its optical properties, has the potential to become a primary choice but due to the difficulties in fabrication, GaP thin films deposited on transparent substrates have never been exploited. In this article we report the design, fabrication, and characterization of three different amorphous GaP metasurfaces obtained through sputtering. Although the material properties can be further optimized, our results show the potential of this material for visible applications making it a viable alternative in the material selection for optical metasurfaces.

36 MATERIALS SCIENCE↗
NASA NTRS1973

Enriched aluminide coatings for dispersion strengthened nickel materials

Improved aluminide/barrier coating combinations for dispersion strengthened nickel materials were investigated. The barrier materials involved alloys with refractory metal content to limit interdiffusion between the coating and the substrate, thereby minimizing void formation. Improved aluminide coatings involved the dispersion of aluminum-rich compounds. Coatings were tested in argon at 1533 K (2300 F) for 100 hours and in cyclic oxidation at 1422 K (2100 F). Two coatings on TDNiCr completed 300 hours of oxidation testing, none on TDNi. Selected coating combinations were evaluated in Mach 1 burner rig testing using JP-4 fuel and air at 1422 K (2100 F) and 1477 K (2200 F) for 350 and 100 hours, respectively. Static oxidation in 1-hour cycles was conducted at 1533 K (2300 F) for 100 hours. For comparison purposes a physical vapor deposition (PVD) NiCrAlY coating was tested concurrently. Only the NiCrA1Y coating survived the 1477 K (2200 F)/100-hour burner rig test and 275 hours of the 350-hour 1422 K (2100 F) test. Elevated temperature exposure reduced room temperature tensile properties but had little effect on elevated temperature properties.

Levinstein, M. A.↗
NASA NTRS1984

Interaction of atomic oxygen with solid surfaces at orbital altitudes (A0114)

The basic approach to this experiment is to expose a wide variety of material surfaces to the atomic flux in orbit. The experiment is passive and depends on preflight and postflight measurements of the test surfaces in the laboratory. The experiment will also include a reflectometer device to measure atomic beam reflection angles and thus momentum accommodations, and a unique passive spacecraft attitude sensor. Samples consisting of solid disks or thin film coatings on substrate disks will be mounted in a panel. The face of this panel will be flown on Long Duration Exposure Facility normal to the incident stream of oxygen atoms. Each disk will have part of its front surface masked so exposure to the atomic-oxygen reaction will be limited to selected areas, the shadowed areas being used as control surfaces in the measurements. A typical sample is an optically flat quartz disk overcoated with a film of the material of interest. These include Ag, Au, Pt, Nb, Ni, Al, C, Si, Ge, LiF, and a few engineering materials. Some materials for which the expected removal rate is high, such as carbon, will be solid disks rather than thin films.

Gregory, J. C.↗
NASA NTRS1991

Organometallic chemical vapor deposition and characterization of ZnGe(1-x)Si(x)P2-Ge alloys on GaP substrates

In this paper, we report the epitaxial growth of ZnGe(1-x)Si(x)P2-Ge alloys on GaP substrates by open tube OMCVD. The chemical composition of the alloys characterized by energy dispersive X-ray spectroscopy shows that alloys with x up to 0.13 can be deposited on (001) GaP. Epitaxial growth with mirror smooth surface morphology has been achieved for x less than or equals to 0.05. Selected area electron diffraction pattern of the alloy shows that the epitaxial layer crystallizes in the chalcopyrite structure with relatively weak superlattice reflections indicating certain degree of randomness in the cation sublattice. Hall measurements show that the alloys are p-type, like the unalloyed films; the carrier concentration, however, dropped about 10 times from 2 x 10 exp 18 to 2 x 10 exp 17/cu cm. Absorption measurements indicate that the band tailing in the absorption spectra of the alloy has been shifted about 0.04 eV towards shorter wavelength as compared to the unalloyed material.

Xing, G. C.↗
NASA NTRS1997

Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

Wilt, David M.↗
NASA NTRS1997

Electrical and Optical Performance Characteristics of p/n InGaAs Monolithic Interconnected Modules

There has been a traditional trade-off in ThermoPhotoVoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A Monolithic Interconnected Module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual Indium Gallium Arsenide (InGaAs) devices series-connected on a single semi-insulating Indium Phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An InfraRed (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74eV InGaAs, have demonstrated V(sub infinity) = 3.2 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. IR reflectance measurements (greater than 2 microns) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

Wilt, David M.↗
DOE OSTI2023

Solar–Driven CO 2 Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

Photothermal CO 2 reduction is one of the most promising routes to efficiently utilize solar energy for fuel production at high rates. However, this reaction is currently limited by underdeveloped catalysts with low photothermal conversion efficiency, insufficient exposure of active sites, low active material loading, and high material cost. Herein, we report a potassium-modified carbon-supported cobalt (K + –Co–C) catalyst mimicking the structure of a lotus pod that addresses these challenges. As a result of the designed lotus-pod structure which features an efficient photothermal C substrate with hierarchical pores, an intimate Co/C interface with covalent bonding, and exposed Co catalytic sites with optimized CO binding strength, the K + –Co–C catalyst shows a record-high photothermal CO 2 hydrogenation rate of 758 mmol gcat –1 h –1 (2871 mmol gCo –1 h –1 ) with a 99.8 % selectivity for CO, three orders of magnitude higher than typical photochemical CO 2 reduction reactions. Here, we further demonstrate with this catalyst effective CO 2 conversion under natural sunlight one hour before sunset during the winter season, putting forward an important step towards practical solar fuel production.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Comparative study of the oxidation of NiAl(100) by molecular oxygen and water vapor using ambient-pressure X-ray photoelectron spectroscopy

The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2 O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2 O 3 structure that provides improved protection to the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2 O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Scalable Surface Micro-Texturing of LLZO Solid Electrolytes for Battery Applications

A challenge for lithium lanthanum zirconate (LLZO)-based solid-state batteries is to increase the critical current density (CCD) to enable high current cycling. A promising strategy is to modify the LLZO surface morphology to provide a larger contact area with the Li metal. Here, a surface-textured thin LLZO electrolyte was prepared through an easily scalable process. The texturing process is a simple pressing of green LLZO tapes between micro-textured substrates. A variety of textures can be produced, depending on the type of substrate, and texturing can be on either one side or both sides. For this work, after pressing and sintering, several micro-patterns are formed on thin LLZO (~118 μm thick). The properties of the various samples were characterized to investigate the impact of surface texturing, and the most promising ones were selected for electrochemical testing in symmetrical lithium cells and full cells. Li symmetric cells using a coarse ridge-textured LLZO exhibit ~2.5 times increased CCD compared to planar non-textured LLZO, and a solid-state full cell shows stable cycling and improved rate performance. Finally, we believe this process offers a favorable trade-off of processing complexity vs structural optimization to maximize CCD.

25 ENERGY STORAGE↗
DOE OSTI2016

Co/NHPI-mediated aerobic oxygenation of benzylic C–H bonds in pharmaceutically relevant molecules

A simple cobalt(II)/N-hydroxyphthalimide catalyst system has been identified for selective conversion of benzylic methylene groups in pharmaceutically relevant (hetero)arenes to the corresponding (hetero)aryl ketones. The radical reaction pathway tolerates electronically diverse benzylic C–H bonds, contrasting recent oxygenation reactions that are initiated by deprotonation of a benzylic C–H bond. The reactions proceed under practical reaction conditions (1 M substrate in BuOAc or EtOAc solvent, 12 h, 90–100 °C), and they tolerate common heterocycles, such as pyridines and imidazoles. A cobalt-free, electrochemical, NHPI-catalyzed oxygenation method overcomes challenges encountered with chelating substrates that inhibit the chemical reaction. The utility of the aerobic oxidation method is showcased in the multigram synthesis of a key intermediate towards a drug candidate (AMG 579) under process-relevant reaction conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Electrocatalytic cleavage of lignin model dimers using ruthenium supported on activated carbon cloth

Biomass lignin is the largest natural source of renewable aromatic compounds, creating an opportunity for its use as a feedstock provided that deconstruction and upgrading methods become available. Valorization of lignin is challenging because its complex structure is naturally recalcitrant to biological degradation. Deconstruction of this amorphous cross-linked polymer requires cleavage of aryl ether bonds, which account for more than half of the linkages between lignin's phenylpropanoid building blocks. High temperature cracking of lignin is possible via pyrolysis, but linkages such as 4-O-5 bonds are resistant to thermal degradation. Electrocatalytic hydrogenation offers a mild alternative; operated at low temperature and atmospheric pressure, it cleaves ether bonds while saturating aromatic rings with in situ generated hydrogen. To investigate the use of catalytic ruthenium supported on activated carbon cloth to cleave 4-O-5 bonds, model compounds that exhibit this linkage were selected, including 3-phenoxyphenol, 4-phenoxyphenol, 3-phenoxyanisole, and 3-phenoxytoluene. The two phenols, 3-phenoxyphenol and 4-phenoxyphenol, were cleaved and hydrogenated to form cyclohexanol. 3-Phenoxyanisole and 3-phenoxytoluene were also cleaved but with lower conversion rates and cyclohexanol yields. Alkaline electrolyte solutions showed the highest cyclohexanol yields for both substrates. Increasing substrate concentrations from 10 mM to 40 mM increased faradaic efficiency to 25%, while decreasing current density from 100 mA (33.33 mA cm -2 ) to 20 mA (6.67 mA cm -2 ) greatly improved the faradaic efficiency to 96%.

09 BIOMASS FUELS↗
DOE OSTI2015

Photocatalytic oxidation of the organic monolayers on TiO{sub 2} surface investigated by in-situ sum frequency generation spectroscopy

In-situ vibrational sum frequency generation (SFG) spectroscopy has been employed to investigate the photocatalytic oxidation of two types of well-ordered organic monolayers, namely, an arachidic acid (AA) monolayer prepared by the Langmuir-Blodgett method and an octadecyltrichlorosilane (OTS) monolayer prepared by the self-assembling method, on a TiO{sub 2} surface under ultraviolet (UV) irradiation. The extremely high sensitivity and unique selectivity of the SFG spectroscopy enabled us to directly probe the structural changes in these monolayers during the surface photocatalytic oxidation and further elucidate their reaction mechanisms at a molecular level. It was revealed that the ordering of the monolayers during the photocatalytic reaction is strongly dependent on their interaction with the substrate; the AA monolayer maintains its ordered conformation until the final oxidation stage, while the OTS monolayer shows a large increase in disordering during the initial oxidation stage, indicating a different photocatalytic reaction mechanism of the two monolayers on the TiO{sub 2} surface.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The nature of catastrophic OLED lighting panel failure

Catastrophic failure due to electrical shorting is currently one of the key reliability challenges for commercial organic light emitting diode (OLED) solid-state lighting panels. Here, we explore the origin of panel-killing shorts through the use of a temperature-selective electroluminescence imaging technique that allows us to locate them early in their life cycle and study their growth over time. We identify two general classes of panel defect, termed bright spots and hot spots, which respectively originate from indium-tin-oxide agglomerations and microscale organic semiconductor dust particles on the substrate. The former are largely benign, whereas the latter can lead to local shunts that grow over time and cause catastrophic failure. We understand the growth process as a self-reinforcing cycle, where shunt-induced heating volatilizes the surrounding organic semiconductor, which in turn expands the shunt and leads to even more heating. Finally based on these results, we identify several practical strategies to arrest the growth of early-stage shorts or prevent them entirely, which could reduce the cost and improve the reliability of OLED lighting.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Gold-tantalum alloy films deposited by high-density-plasma magnetron sputtering

Gold-tantalum alloy films are of interest for biomedical and magnetically-assisted inertial confinement fusion applications. Here, we systematically study the effects of substrate tilt (0°–80°) and negative substrate bias (0–100 V) on properties of ≲3-μm-thick films deposited by high-power impulse magnetron sputtering (HiPIMS) from a Au–Ta alloy target (with 80 at. % of Ta). Results reveal that, for all the substrate bias values studied, an increase in substrate tilt leads to a monotonic decrease in film thickness, density, residual compressive stress, and electrical conductivity. Larger substrate bias favors the formation of a body-centered cubic phase, with films exhibiting lower column tilt and higher density, electrical conductivity, and residual compressive stress. Furthermore, these changes are attributed to metal atom ionization effects, based on the lack of correlation with distributions of landing energies and incident angles of depositing species as calculated by Monte Carlo simulations of ballistic collisions and gas phase atomic transport. By varying substrate tilt and bias in HiPIMS deposition, properties of Au–Ta alloy films can be controlled in a very wide range, including residual stress from –2 to +0.5 GPa, density from 12 to 17 g/cm 3 , and the electrical resistivity from 50 to 4500 μΩ cm, enabling optimum deposition conditions to be selected for specific applications.

36 MATERIALS SCIENCE↗
NASA NTRS1987

An experimental evaluation of apparent strain from foil strain gauges attached to carbon composite substrates

An experimental evaluation of apparent thermal strains is conducted using various combinations of substrate/gauge/attachment structure and redundant high temperature extensometry. It is found that the extensometry could either confirm independent measurements of the substrate's thermal expansion, or quantify nonzero mechanical strains resulting from uncertain material behavior and boundary conditions. Apparent strain and thermal expansion behavior data can then be used to modify the raw strain measurements in order to determine either stress producing or total strains. Limitation of the correction procedure for the three selected strain gauges is noted which is due to relatively large gauge/attachment variability.

Scott, B. R.↗
DOE OSTI2017

Non-noble metal based electro-catalyst compositions for proton exchange membrane based water electrolysis and methods of making

The invention provides electro-catalyst compositions for an anode electrode of a proton exchange membrane-based water electrolysis system. The compositions include a noble metal component selected from the group consisting of iridium oxide, ruthenium oxide, rhenium oxide and mixtures thereof, and a non-noble metal component selected from the group consisting of tantalum oxide, tin oxide, niobium oxide, titanium oxide, tungsten oxide, molybdenum oxide, yttrium oxide, scandium oxide, cooper oxide, zirconium oxide, nickel oxide and mixtures thereof. Further, the non-noble metal component can include a dopant. The dopant can be at least one element selected from Groups III, V, VI and VII of the Periodic Table. The compositions can be prepared using a surfactant approach or a sol gel approach. Further, the compositions are prepared using noble metal and non-noble metal precursors. Furthermore, a thin film containing the compositions can be deposited onto a substrate to form the anode electrode.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Ultrasensitive biochemical sensing device and method of sensing analytes

Systems and methods biochemically sense a concentration of a ligand using a sensor having a substrate having a metallic nanoparticle array formed onto a surface of the substrate. A light source is incident on the surface. A matrix is deposited over the nanoparticle array and contains a protein adapted to binding the ligand. A detector detects s-polarized and p-polarized light from the reflective surface. Spacing of nanoparticles in the array and wavelength of light are selected such that plasmon resonance occurs with an isotropic point such that -s and -p polarizations of the incident light result in substantially identical surface Plasmon resonance, wherein binding of the ligand to the protein shifts the resonance such that differences between the -S and -P polarizations give in a signal indicative of presence of the ligand.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Weather-detecting devices and related methods

A weather-detecting device (100) can include a substrate (102) and a detection region (106) exposed to an environment within which the weather-detecting device (100) is situated when in use. An array (110) of heating elements (112) can be mounted at a first side of the substrate (102), with at least one surface of each heating element (112) in the array (110) being positioned within the detection region (106). A controller can be electrically coupled to the array (110) of heating elements (112), and the controller can individually address each heating element (112) in the array (110) to selectively pass electrical current through each heating element (112).

Garrett, Timothy John↗