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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Global Paleoclimatic Data for 6000 Yr B.P.

To determine regional and global climatic variations during the past 6000 years, pollen, lake level, and marine plankton data from 797 stations were compiled to form a global data set. Radiocarbon dating and dated tephras were used to determine the ages of the specimens. The data available for the pollen data are site number, site name, latitude, longitude, elevation, and percentages of various taxa. For lake-level data, the data are site number, site name, latitude, longitude, and lake-level status. And for marine plankton, the data are site number, site name, latitude, longitude, water depth, date, dating control code, depth of sample, interpolated age of sample, estimated winter and summer sea-surface temperatures, and percentages of various taxa. The data are in 55 files: 5 files for each of 9 geographic regions and 10 supplemental files. The files for each region include (1) a FORMAT file describing the format and contents of the data for that region, (2) an INDEX file containing descriptive information about each site and its data, (3) a DATA file containing the data and available climatic estimates, (4) a PUBINDEX file indexing the bibliographic references associated with each site, and (5) a REFERENCE file containing the bibliographic references. The files range in size from 2 to 66 kB.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Moisture outgassing from siloxane elastomers containing surface-treated-silica fillers

Abstract The outgassing kinetics from siloxane elastomers is dominated by moisture desorption from the reinforcing silica filler and can be detrimental in moisture-sensitive applications. In this study, a custom 3D printable siloxane rubber (LL50) was analyzed in three different states: after a high temperature vacuum heat treatment, limited re-exposure to moisture after vacuum heat treatment, and in the as-received condition. The outgassing kinetics were extracted using isoconversional and iterative regression analyses. Moisture release by physisorbed and chemisorbed water from the samples have activation energies in the range of 50 kJ/mol (physisorbed type) to 220 kJ/mol (chemisorbed type). Overall, moisture outgassing from LL50 was 10 times lower than that from traditionally prepared siloxane rubbers. The vastly diminished moisture content in LL50 is attributed to the existence of a finite low level of silanol groups that remain on the fumed silica surface even after hydrophobic treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Rational Design of Hyperbranched Nanowire Systems for Tunable Superomniphobic Surfaces Enabled by Atomic Layer Deposition

A method for tunable control of geometry in hyperbranched ZnO nanowire (NW) systems is reported, which enables the rational design and fabrication of superomniphobic surfaces. Branched NWs with tunable density and orientation were grown via a sequential hydrothermal process, in which atomic layer deposition (ALD) was used for NW seeding, disruption of epitaxy, and selective blocking of NW nucleation. This approach allows for the rational design and optimization of three-level hierarchical structures, in which the geometric parameters of each level of hierarchy can be individually controlled. We demonstrate the coupled relationships between geometry and contact angle for a variety of liquids, which is supported by mathematical models of structural superomniphobicity. The highest performing superomniphobic surface was designed with three levels of hierarchy and achieved the following advancing/receding contact angles, water: 172°/170°, hexadecane: 166°/156°, octane: 162°/145°, and heptane: 160°/130°. Low surface tension liquids were shown to bounce off the surface from a height of 7 cm without breaking through and wetting. This approach demonstrates the power of ALD as an enabling technique for hierarchical materials by design, spanning the macro, micro, and nano length scales.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2017

Electrochemical Growth of Copper Hydroxy Double Salt Films and Their Conversion to Nanostructured p-Type CuO Photocathodes

New electrochemical synthesis methods were developed to produce copper hydroxy double salts (Cu-HDS) films with four different intercalated anions (NO 3 - , SO 4 2- , Cl - , and dodecyl sulfate (DS)) as pure crystalline films as-deposited (Cu 2 NO 3 (OH) 3 , Cu 4 SO 4 (OH) 6 , Cu 2 Cl(OH) 2 , and Cu 2 DS(OH) 3 ). These methods are based on p-benzoquinone reduction, which increases the local pH at the working electrode and triggers the precipitation of Cu 2+ and appropriate anions as Cu-HDS films on the working electrode. The resulting Cu-HDS films could be converted to crystalline Cu(OH) 2 and CuO films by immersing them in basic solutions. Since Cu-HDS films were composed of 2D crystals due to the atomic level layered structure of HDS, the CuO films prepared from Cu-HDS films have unique low dimensional nanostructures, creating high surface areas, which cannot be obtained by direct deposition of CuO that has a 3D atomic level crystal structure. Here, the resulting nanostructures allowed the CuO films to facilitate electron-hole separation and demonstrate great promise for photocurrent generation when investigated as a photocathode for a water splitting photoelectrochemical cell. Electrochemical synthesis of Cu-HDS films and their facile conversion to CuO films will provide new routes to tune morphologies and properties of the CuO electrodes that may not be possible by other synthesis means.

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

Investigation of the electrical conduction mechanisms in P-type amorphous germanium electrical contacts for germanium detectors in searching for rare-event physics

For the first time, electrical conduction mechanisms in the disordered material system is experimentally studied for p-type amorphous germanium (a-Ge) used for high-purity Ge detector contacts. The localization length and the hopping parameters in a-Ge are determined using the surface leakage current measured from three high-purity planar Ge detectors. The temperature dependent hopping distance and hopping energy are obtained for a-Ge fabricated as the electrical contact materials for high-purity Ge planar detectors. As a result, we find that the hopping energy in a-Ge increases as temperature increases while the hopping distance in a-Ge decreases as temperature increases. The localization length of a-Ge is on the order of 2.13$^{-0.05}_{+0.07}$A° to 5.07$^{0.83}_{+2.58}$A°,depending on the density of states near the Fermi energy level within bandgap. Using these parameters, we predict that the surface leakage current from a Ge detector with a-Ge contacts can be much smaller than one yocto amp (yA) at helium temperature, suitable for rare-event physics searches.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

2021 Annual Site Environmental Report

This report provides the U.S. Department of Energy (DOE) and the public with information on the level of radioactive and non-radioactive pollutants (if any) that are added to the environment as a result of Princeton Plasma Physics Laboratory’s (PPPL) operations. The results of PPPL’s 2021 environmental surveillance and monitoring program are presented and discussed. The report also summarizes environmental initiatives, assessments, and community involvement programs that were undertaken in 2021. PPPL’s on-site operations were significantly curtailed in 2021 due to the global coronavirus pandemic. PPPL has engaged in fusion energy research since 1951. The Laboratory’s mission is to develop the scientific knowledge and advanced engineering to enable fusion to power the U.S. and the world, and to developing the understanding of plasmas from the nano- to the astrophysical scale. PPPL’s primary experiment, the National Spherical Torus Experiment-Upgrade (NSTX-U) is a collaboration among national laboratories, universities, and national and international research institutions and is a major element in the US Fusion Energy Sciences Program. Its design tests the physics principles of spherical torus (ST) plasmas, playing an important role in the development of smaller, more economical fusion reactors. Due to previous operational issues, NSTX-U did not operate in 2021. PPPL is engaged in a project to replace key NSTX-U components and systems to enable operation of this international fusion user facility. In 2021, PPPL’s radiological environmental monitoring program measured tritium in the air at the NSTX-U Stack and at onsite sampling stations. Using highly sensitive air monitors, PPPL is capable of detecting small changes in the ambient levels of tritium. The operation of an in-stack monitor located on D-site is used to demonstrate compliance with the National Emission Standard for Hazardous Air Pollutants (NESHAPs) regulations. Also included in PPPL’s radiological environmental monitoring program, are water monitoring – ground, surface, and waste waters. PPPL’s radiological monitoring program characterized the background levels of tritium in the environment and those data are presented in this report. Ground water monitoring continued under New Jersey Department of Environmental Protection’s (NJDEP) Site Remediation Program regulations. PPPL monitored for non-radiological contaminants, mainly volatile organic compounds (components of common degreasing solvents). In 2021, PPPL complied with permit limits for surface and sanitary discharges. PPPL was honored with awards for EPEAT-certified electronics purchasing and use of peracetic acid as an alternative water treatment chemical in its non-potable process water systems an NJDEP recycling award.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

2016 Annual Site Environmental Report

This report provides the U.S. Department of Energy (DOE) and the public with information on the level of radioactive and non-radioactive pollutants (if any) that are added to the environment as a result of Princeton Plasma Physics Laboratory’s (PPPL) operations. The results of the 2016 environmental surveillance and monitoring program for PPPL’s are presented and discussed. The report also summarizes environmental initiatives, assessments, and community involvement programs that were undertaken in 2016. PPPL has engaged in fusion energy research since 1951. The vision of the Laboratory is to create innovations to make fusion power a practical reality – a clean, alternative energy source. 2016 marked the eighteenth year of National Spherical Torus Experiment and the first year of NSTX-U (Upgrade) operations. The NSTX-U Project is a collaboration among national laboratories, universities, and national and international research institutions and is a major element in the US Fusion Energy Sciences Program. Its design tests the physics principles of spherical torus (ST) plasmas, playing an important role in the development of smaller, more economical fusion reactors. NSTX-U began operations after its first upgrade that installed the new center stack magnets and second neutral beam, which would allow for hotter plasmas and greater field strength to maintain the fusion reaction longer. Due to operational issues with a poloidal coil, NSTX-U operated briefly in 2016. In 2016, PPPL’s radiological environmental monitoring program measured tritium in the air at the NSTX-U Stack and at on -site sampling stations. Using highly sensitive monitors, PPPL is capable of detecting small changes in the ambient levels of tritium. The operation of an in- stack monitor located on D-site is used to demonstrate compliance with the National Emission Standard for Hazardous Air Pollutants (NESHAPs) regulations. Also included in PPPL’s radiological environmental monitoring program, are water monitoring – ground and surface, and waste waters. PPPL’s radiological monitoring program characterized the background levels of tritium in the environment; the data are presented in this report. Ground water monitoring continued under the New Jersey Department of Environmental Protection’s Site Remediation Program. PPPL monitored for non-radiological contaminants, mainly volatile organic compounds (components of chlorinated degreasing solvents). In 2016, PPPL was in compliance with its permit limits for surface and sanitary discharges, excepting two elevated chlorine-produced oxidant concentration. PPPL was honored with awards for its waste reduction and recycling program, and its “EPEAT” electronics purchasing for the third consecutive year.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Sensing trace levels of molecular species in solution via zinc oxide nanoprobe Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) has potential for unique clinical, environmental, and military applications, among many others, but it is limited by a rapid decrease in signal with distance from the sensing surface. For this reason, much study of SERS-based biosensing involves chemical or physical adsorption of analytes to an active surface. Adsorption, however, limits the types of analytes that can be detected and detection sensitivity. The three-dimensional closely packed architecture of zinc oxide (ZnO) nanowires decorated with silver nanoparticles increases SERS intensity, allowing for adsorption-free biosensing. This approach greatly expands the potential applications of Raman spectroscopy as a biosensing technique. This article demonstrates a significant SERS enhancement from silver nanoparticle-decorated ZnO nanoprobes to the Raman spectra of crystal violet, melamine, and adenine solutions. These enhancements were quantified by comparing the intensity of Raman peaks from each of the three solutions through ZnO nanowires decorated with silver nanoparticles with that through bare ZnO nanowires. Estimated enhancement of the Raman signal accounted for the volume difference between solution affected by SERS and solution sensed by the Raman system. More importantly, the detected SERS signal is from molecules in solution and unadsorbed to the sensing surfaces. This lack of adsorption was confirmed by tracking the SERS enhancement of a crystal violet Raman peak over time. This greatly enhances the value and flexibility of Raman spectroscopy as a detection technique for a wide variety of applications.

42 ENGINEERING↗
DOE OSTI2024

Mean-Field Ring Polymer Rates Using a Population Dividing Surface

Mean-field Ring Polymer Molecular Dynamics (MF-RPMD) offers a computationally efficient method for the simulation of reaction rates in multi-level systems. Previous work has established that, to model a nonadiabatic state-to-state reaction accurately, the dividing surface must be chosen to explicitly sample kinked ring polymer configurations where at least one bead is in a different electronic state than the others. Building on this, we introduce a population difference coordinate and a kink-constrained dividing surface, and we test the accuracy of the resulting mean-field rate theory on a series of bilinear coupling model systems. Here, we demonstrate that this new MF-RPMD rate approach is efficient to implement and quantitatively accurate for models over a wide range of driving forces, coupling strengths, and temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Groundwater and Surface Water Flow (GSFLOW) model files for the East River, Colorado

The data package contains model input files and executables for the East River, Colorado (750 km2) located in the headwaters of the Upper Colorado River Basin. The code applied is the U.S. Geological Survey (USGS) Groundwater and Surface Water Flow (GSFLOW) model. The model contains a 100-m grid resolution to represent topographic complexity and a daily timestep accounts for energy and water partitioning between the snowpack, vegetation, soil zone and bedrock. The land surface model is dynamically linked to a three-dimensional groundwater flow model that allows for streamflow gaining and losing conditions. The groundwater model accounts for nine stratigraphic units and extends 400 m below land surface. Using this modeling framework we explore historical water budgets (water year 1987-2022) and the influence of seasonal warming and associated mechanisms driving groundwater declines and streamflow loss. A Readme_062424.txt file provides instructions on how to download all files. Input and output files are provided for the historical simulation representative of water years 1987 to 2022 (i.e. baseline) and the all-year +4C warming scenario. Instructions are provided to run the seasonal warming scenarios with warming applied only to the autumn, winter, spring or summer months. Modeled output used in figures for Carroll et al., 2024 are also provided with metadata describing where these data were obtained. This dataset additionally includes a file-level metadata (flmd.csv) file that lists each file contained in the dataset with associated metadata; and a data dictionary (dd.csv) file that contains column/row headers used throughout the files along with a definition, units, and data type.Updated on 06-24-2024: The dataset was updated to include model outputs (updated base.zip and 4C.zip files), figure source files (Figure_Source_Files.zip), an updated Readme file (Readme_062424.txt), climate input files (climate_input_files.zip), and the adoption of ESS-DIVE File Level Metadata and CSV reporting formats (inclusion of flmd.csv and dd.csv files).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Spectrum of surface plasmons excited by spontaneous quantum dot transitions

We consider quantum fluctuations of near fields of a quantum emitter (two-level system (TLS) with population inversion sustained by incoherent pumping) in the near-field zone of a plasmon (metallic) nanoparticle. The spectrum of surface plasmons excited by spontaneous transitions in the quantum emitter is obtained below the lasing threshold of such a system (spaser) in the approximation of a small number of plasmons. It is shown that the relaxation rate is the sum of the quantum emitter's rates of relaxation to its thermal reservoir and the plasmon cavity. The resulting dependence of the average number of plasmons on the pump intensity indicates the nonthreshold nature of the process.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Annealing effect on the photoluminescence properties of ZnO nanorod array prepared by a PLD-assistant wet chemical method

Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700 deg. C for 1 h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra, the mechanisms of visible emission were discussed. - Research Highlights: {yields} ZnO nanorod array with good crystallography, low defects concentration and good optical property was obtained after annealed at 700 deg. C for 1 h. {yields} The transition from the conduction band to the O{sub i} level may be responsible for the yellow-green emission. {yields} The yellow emission may originate from the presence of Zn(OH){sub 2} on the surface or the band transition from conduction band to V{sub o}Zn{sub i} level. {yields} The transition from the Zn{sub i} level to the level should produce an orange emission or an orange-red emission.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Gas source molecular beam epitaxy of scandium nitride on silicon carbide and gallium nitride surfaces

Scandium nitride (ScN) is a group IIIB transition metal nitride semiconductor with numerous potential applications in electronic and optoelectronic devices due to close lattice matching with gallium nitride (GaN). However, prior investigations of ScN have focused primarily on heteroepitaxial growth on substrates with a high lattice mismatch of 7%–20%. In this study, the authors have investigated ammonia (NH{sub 3}) gas source molecular beam epitaxy (NH{sub 3}-GSMBE) of ScN on more closely lattice matched silicon carbide (SiC) and GaN surfaces (<3% mismatch). Based on a thermodynamic analysis of the ScN phase stability window, NH{sub 3}-GSMBE conditions of 10{sup −5}–10{sup −4} Torr NH{sub 3} and 800–1050 °C where selected for initial investigation. In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Rutherford backscattering measurements showed all ScN films grown using these conditions were stoichiometric. For ScN growth on 3C-SiC (111)-(√3 × √3)R30° carbon rich surfaces, the observed attenuation of the XPS Si 2p and C 1s substrate core levels with increasing ScN thickness indicated growth initiated in a layer-by-layer fashion. This was consistent with scanning electron microscopy (SEM) images of 100–200 nm thick films that revealed featureless surfaces. In contrast, ScN films grown on 3C-SiC (111)-(3 × 3) and 3C-SiC (100)-(3 × 2) silicon rich surfaces were found to exhibit extremely rough surfaces in SEM. ScN films grown on both 3C-SiC (111)-(√3 × √3)R30° and 2H-GaN (0001)-(1 × 1) epilayer surfaces exhibited hexagonal (1 × 1) low energy electron diffraction patterns indicative of (111) oriented ScN. X-ray diffraction ω-2θ rocking curve scans for these same films showed a large full width half maximum of 0.29° (1047 arc sec) consistent with transmission electron microscopy images that revealed the films to be poly-crystalline with columnar grains oriented at ≈15° to the [0001] direction of the 6H-SiC (0001) substrate. In-situ reflection electron energy loss spectroscopy measurements determined the band-gap for the NH{sub 3}-GSMBE ScN films to be 1.5 ± 0.3 eV, and thermal probe measurements indicated all ScN films to be n-type. The four point probe sheet resistance of the ScN films was observed to increase with decreasing growth temperature and decreased with unintentional oxygen incorporation. Hg probe capacitance–voltage measurements indicated N{sub D}-N{sub A} decreased with decreasing growth temperature from 10{sup 19} to 10{sup 20}/cm{sup 3} for the lowest resistivity films to ≅5 × 10{sup 16}/cm{sup 3} for the highest resistivity films. In-situ ultraviolet photoelectron spectroscopy measurements additionally showed the valence band maximum moving from 1.4 to 0.8 eV below the Fermi level with decreasing growth temperature consistent with the increased resistivity and reduction in carrier concentration. These results suggest that additional reductions in ScN carrier concentrations can be achieved via continued optimization of ScN growth conditions and selection of substrate orientation and surface termination.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Elucidating facet dependent electronic and electrochemical properties of Cu 2 O nanocrystals using AFM/SCEM and DFT

Cuprous oxide (Cu 2 O) has extensively been studied owing to its excellent optical, magnetic, and catalytic properties. Many of these properties are facet-dependent and have not been well elucidated. This work synthesized cubic, cuboctahedral, octahedral, and rhombic dodecahedral shaped Cu 2 O nanocrystals of ~300 nm in size to evaluate the facet-dependent electrochemical activities. Here, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly used to reveal the average electrochemical activities at the ensemble level. Atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) was further used to assess the electrochemical activities of different Cu 2 O nanocrystals at the facet level. Hexaammineruthenium (III) chloride ({Ru(NH 3 ) 6 }Cl 3 ) was employed as the probe molecules that reacted with four different Cu 2 O nanocrystals under —400mV and yielded ~300 pA current between the probing tip and the nanocrystal surface. The tip-current mapping results indicate that rhombic dodecahedral Cu 2 O exhibits higher electrocatalytic activity than other shaped Cu 2 O, due to the presence of dominant exposed facet of {110} as indicated by the relatively high tip current. Density-functional theory (DFT) calculations confirmed the facet dependence of local surface energy and electronic structure of Cu 2 O nanocrystals. Besides electrochemical activity, the surface work function and adsorptive properties were both observed to vary with the shape and dominant exposed facets of Cu 2 O. This study presented a unique experimental and computational chemistry approach to analyze surface electrochemical properties of Cu 2 O crystals at a crystalline facet level.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Formulation of a Consistent Multi‐Species Canopy Description for Hydrodynamic Models Embedded in Large‐Scale Land‐Surface Representations of Mixed‐Forests

Abstract The plant hydrodynamic approach represents a recent advancement to land surface modeling, in which stomatal conductance responds to water availability in the xylem rather than in the soil. To provide a realistic representation of tree hydrodynamics, hydrodynamic models must resolve processes at the level of a single modeled tree, and then scale the resulting fluxes to the canopy and land surface. While this tree‐to‐canopy scaling is trivial in a homogeneous canopy, mixed‐species canopies require careful representation of the species properties and a scaling approach that results in a realistic description of both the canopy and individual‐tree hydrodynamics, as well as leaf‐level fluxes from the canopy and their forcing. Here, we outline advantages and pitfalls of three commonly used approaches for representing mixed forests in land surface models and present a new framework for scaling vegetation characteristics and fluxes in mixed forests. The new formulation scales fluxes from the tree to canopy level in an energy‐ and mass‐conservative way and allows for a consistent multi‐species/multi‐type canopy description by hydrodynamic models.

Bohrer, G.↗
DOE OSTI2018

CAUSES: Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site

Abstract All the weather and climate models participating in the Clouds Above the United States and Errors at the Surface project show a summertime surface air temperature (T2 m) warm bias in the region of the central United States. To understand the warm bias in long‐term climate simulations, we assess the Atmospheric Model Intercomparison Project simulations from the Coupled Model Intercomparison Project Phase 5, with long‐term observations mainly from the Atmospheric Radiation Measurement program Southern Great Plains site. Quantities related to the surface energy and water budget, and large‐scale circulation are analyzed to identify possible factors and plausible links involved in the warm bias. The systematic warm season bias is characterized by an overestimation of T2 m and underestimation of surface humidity, precipitation, and precipitable water. Accompanying the warm bias is an overestimation of absorbed solar radiation at the surface, which is due to a combination of insufficient cloud reflection and clear‐sky shortwave absorption by water vapor and an underestimation in surface albedo. The bias in cloud is shown to contribute most to the radiation bias. The surface layer soil moisture impacts T2 m through its control on evaporative fraction. The error in evaporative fraction is another important contributor to T2 m. Similar sources of error are found in hindcast from other Clouds Above the United States and Errors at the Surface studies. In Atmospheric Model Intercomparison Project simulations, biases in meridional wind velocity associated with the low‐level jet and the 500 hPa vertical velocity may also relate to T2 m bias through their control on the surface energy and water budget.

54 ENVIRONMENTAL SCIENCES↗