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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Remote-Sensing Reflectance and Inherent Optical Properties for Optically Deep Waters: A Revisit

Remote-sensing reflectance (r(rs)) is defined as the ratio of upwelling radiance to downwelling irradiance. Relationships between remote-sensing reflectance and inherent optical properties serve as the basis for ocean-color modeling, as well as for spectral deduction of oceanic constituents through analytical/semi-analytical models of ocean color. A decade ago, a simple and concise formula based on Monte Carlo simulations was developed by relating rrs to a property u, the ratio of backscattering (b(b)) to the sum of absorption (a) and backscattering (u = b(b)/(a+b(b))). This relationship generally ignored the shape differences in phase functions between molecular scattering and particle scattering. In this study, the relationship is updated with separate parameters for molecular and particle scattering, based on the Radiative Transfer Equation through use of Hydrolight numerical solutions. The new approach fits r(rs) better than an earlier traditional formula, for both clear and turbid waters.

Lee, Zhong-Ping↗
DOE OSTI2016

Co/Cr co-doped MgGa{sub 2}O{sub 4} nanoparticles: Microstructure and optical properties

Graphical abstract: The Ga 2p{sub 3/2} spectra consist of two peaks, corresponding to Ga{sup 3+} ions placed at octahedral and tetrahedral sites, respectively. The fraction of tetrahedral Ga{sup 3+} ions (∼1117 eV) increases with increasing doping concentration. - Highlights: • Structural and properties of Co{sup 2+}/Cr{sup 3+}: MgGa{sub 2}O{sub 4} nanoparticles were characterized. • The distribution of cations was studied using XPS. • The inversion degree increased with increasing content of doping ions. • The doping concentration has also effect on absorption and emission properties. • Optical properties of nanoparticles were discussed based on the structural results. - Abstract: MgGa{sub 2}O{sub 4} nanoparticles co-doped with Co{sup 2+}/Cr{sup 3+} ions were prepared by a citrate sol–gel method. Their microstructure and optical properties were studied using X-ray powder diffraction (XRD), infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), absorption and fluorescence spectroscopy. MgGa{sub 2}O{sub 4} nanoparticles with the size of 10–30 nm were obtained when the precursor was annealed at 800 °C. Results indicated that Ga{sup 3+} and Mg{sup 2+} cations occupied the octahedral sites as well as the tetrahedral sites in samples. The inversion degree of Ga or Mg increased with increasing content of doping ions. Absorption spectra indicated that Co{sup 2+} and Cr{sup 3+} ions entered both the tetrahedral and octahedral sites of spinel structure by substituting Mg{sup 2+} and Ga{sup 3+} ions, respectively. Emission spectra of the co-doped MgGa{sub 2}O{sub 4} showed a broad emission band peaking at 700 and 680 nm, relevant to the emission characteristic of octahedral Cr{sup 3+} and tetrahedral Co{sup 2+} ions.

36 MATERIALS SCIENCE↗
NASA NTRS2010

Advances in Measuring the Apparent Optical Properties (AOPs) of Optically Complex Waters

This report documents new technology used to measure the apparent optical properties (AOPs) of optically complex waters. The principal objective is to be prepared for the launch of next-generation ocean color satellites with the most capable commercial off-the-shelf (COTS) instrumentation. An enhanced COTS radiometer was the starting point for designing and testing the new sensors. The follow-on steps were to apply the lessons learned towards a new in-water profiler based on a kite-shaped backplane for mounting the light sensors. The next level of sophistication involved evaluating new radiometers emerging from a development activity based on so-called microradiometers. The exploitation of microradiometers resulted in an in-water profiling system, which includes a sensor networking capability to control ancillary sensors like a shadowband or global positioning system (GPS) device. A principal advantage of microradiometers is their flexibility in producing, interconnecting, and maintaining instruments. The full problem set for collecting sea-truth data--whether in coastal waters or the open ocean-- involves other aspects of data collection that were improved for instruments measuring both AOPs and inherent optical properties (IOPs), if the uncertainty budget is to be minimized. New capabilities associated with deploying solar references were developed as well as a compact solution for recovering in-water instrument systems from small boats.

Morrow, John H.↗
DOE OSTI2014

Electronic and optical properties of NbO{sub 2}

In the present study, we combine theoretical and experimental approaches in order to gain insight into the electronic properties of both the high-temperature, rutile (metallic) and low-temperature, body-centered tetragonal (insulating) phase of niobium dioxide (NbO{sub 2}) as well as the optical properties of the low-temperature phase. Theoretical calculations performed at the level of the local density approximation, Hubbard U correction, and hybrid functional are complemented with the spectroscopic ellipsometry (SE) of epitaxial films grown by molecular beam epitaxy. For the rutile phase, the local density approximation (LDA) gives the best description and predicts Fermi surface nesting consistent with wave vectors that lead to niobium-niobium dimerization during the phase transition. For the insulating phase, LDA provides a good quantitative description of the lattice, but only a qualitative description for the band gap. Including a Hubbard U correction opens the band gap at the expense of correctly describing the valence band and lattice of both phases. The hybrid functional slightly overestimates the band gap. Ellipsometric measurement is consistent with insulating behavior with a 1.0 eV band gap. Comparison with the theoretical dielectric functions, obtained utilizing a scissors operator to adjust the LDA band gap to reproduce the ellipsometry data, allows for identification of the SE peak features.

36 MATERIALS SCIENCE↗
NASA NTRS2020

A Flexible Parameterization for Shortwave and Longwave Optical Properties of Ice Crystals and Derived Bulk Optical Properties for Climate Models

We provide a parameterization of the extinction efficiency, single scattering albedo and asymmetry parameter of single ice crystals with any combination of particle volume, projected area, component aspect ratio and crystal distortion at any wavelength between 0.2 and 100 mm. The paramerization is an extension of the one previously published by van Diedenhoven et al. (2014, https://doi.org/10.1175/JAS-D-13-0205.1). In addition, the parameterized optical properties are integrated over size distributions yielding bulk extinction efficiencies, single scattering albedos and asymmetry parameters for large ranges of effective radii, particle component aspect ratios and crystal distortion values. The parameterization of single particle optical properties is evaluated with a reference database. The bulk optical properties are evaluated against the ice model selected for the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 products, for which accurate optical properties are available. Mean absolute errors in parameterized extinction efficiency, asymmetry parameter and single scattering albedo are shown to be 0.0272, 0.00890 and 0.00468, respectively for shortwave wavelengths, while they are 0.0641, 0.0368 and 0.0200 in the longwave. Shortwave and longwave asymmetry parameter and single scattering albedos are shown to vary strongly with particle component aspect ratio and distortion, resulting in substantial variation in shortwave fluxes, but relatively small variations in longwave cloud emissivity. The parameterization and bulk optical properties are made publicly available.

Bastiaan Van Diedenhoven↗
DOE OSTI2015

Surface properties, crystallinity and optical properties of anodised titanium in mixture of β-glycerophosphate (β-GP) and calcium acetate (CA)

Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It had been widely used to deposit the ceramic coatings on the metals surface. This method has been widely used in surface modification of biomaterials especially for dental implants. In this study, the surface morphology, crystallinity and optical properties of titanium foil was modified by anodising in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The experiments were carried out at high voltage (350 V), different anodising time (5 and 10 minutes) and current density (10-70 mA.cm{sup −2}) at room temperature. Anodised titanium was characterised by using field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and UV-Vis spectrometry. The result of the experiment showed that surface morphology, crystallinity and optical properties depended strongly on the current density and anodising time. More porous surface and large amount of anatase and rutile was produced at higher current density and longer anodising time. Apart from that, it is also revealed that the energy band gap of anodised titanium increases as the increase in current density due to the presence of anatase and rutile TiO{sub 2}.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Grain optical properties

The optical properties of small grains provide the link between the infrared observations presented in Chapter 1 and the dust composition described in Chapter 3. In this session, the optical properties were discussed from the viewpoint of modeling the emission from the dust coma and the scattering in order to draw inference about the dust size distribution and composition. The optical properties are applied to the analysis of the infrared data in several ways, and these different uses should be kept in mind when judging the validity of the methods for applying optical constants to real grains.

Hanner, Martha↗
DOE OSTI2014

Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Brush-Coated Nanoparticle Polymer Thin Films: structure-mechanical-optical properties

Our work was devoted to understanding the structure and properties of a class of thin film polymer nanocomposites (PNCs). PNCs are composed of polymer hosts into which nanoparticles (metallic nanoparticles, quantum dots, nanorods, C 60 , nanotubes) are incorporated. PNCs exhibit a diverse range of functional properties (optical, electronic, mechanical, biomedical, structural), determined in part by the chemical composition of the polymer host and the type of nanoparticle. The properties PNCs rely not only on specific functional, size-dependent, behavior of the nanoparticles, but also on the dispersion, and organizational order in some cases, inter-nanoparticle separation distances, and on relative interactions between the nanoparticles and the host. Therefore the scientific challenges associated with understanding the interrelations between the structure and function/properties of PNCs are far more complex than may be understood based only on the knowledge of the compositions of the constituents. The challenges of understanding the structure-function behavior of PNCs are further compounded by the fact that control of the dispersion of the nanoparticles within the polymer hosts is difficult; one must learn how to disperse inorganic particles within an organic host. The goal of this proposal was to develop an understanding of the connection between the structure and the thermal (glass transition), mechanical and optical properties of a specific class of PNCs. Specifically PNCs composed of polymer chain grafted gold nanoparticles within polymer hosts. A major objective was to understand how to develop basic principles that enable the fabrication of functional materials possessing optimized morphologies and combinations of materials properties.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

Brown Carbon↗
DOE OSTI2019

Optical properties and radiative forcing of fractal-like tar ball aggregates from biomass burning

Tar balls are frequently found in slightly aged biomass burning plumes. They are spherical in shape, have diameters between ~100 and 300 nm, are amorphous and composed mostly of oxygen and carbon. Tar balls are light absorbing and considered to be a component of brown carbon. Tar balls have been typically reported and analyzed as individual spheres; however, in a recent study, we reported the presence of significant fractions of fractal-like tar ball aggregates in fire plumes from different geographical locations. Aggregation affects the optical properties of particles; therefore, we use T-Matrix and Lorenz-Mie simulations to explore the effects of aggregation on the tar balls’ optical properties in the 350 – 1150 nm wavelength range. We also evaluate the effects of different index of refraction values available from the literature, different monomer numbers, and monomer sizes, as these are key factors determining the aggregates optical properties. Furthermore, we estimate the direct radiative forcing for low and high surface albedos. The single scattering albedo of aggregates exceed by up to 77% that of individual tar balls. The hemispherical upscatter fraction of tar ball aggregates are more than 100% larger than for individual tar balls in many cases. The top of the atmosphere simple forcing efficiency over dark surfaces shows large variabilities with differences up to ~53% between the tar ball aggregates and individual tar balls. These results demonstrate that aggregation of tar balls can have a significant impact on their optical properties and radiative forcing.

Tar balls, aggregates, brown carbon, biomass burni↗
DOE OSTI2019

Physical and optical properties of the International Simple Glass

Abstract Radioactive waste immobilization is a means to limit the release of radionuclides from various waste streams into the environment over a timescale of hundreds to many thousands of years. Incorporation of radionuclide-containing wastes into borosilicate glass during vitrification is one potential route to accomplish such immobilization. To facilitate comparisons and assessments of reproducibility across experiments and laboratories, a six-component borosilicate glass (Si, B, Na, Al, Ca, Zr) known as the International Simple Glass (ISG) was developed by international consensus as a compromise between simplicity and similarity to waste glasses. Focusing on a single glass composition with a multi-pronged approach utilizing state-of-the-art, multi-scale experimental and theoretical tools provides a common database that can be used to assess relative importance of mechanisms and models. Here we present physical property data (both published and previously unpublished) on a single batch of ISG, which was cast into individual ingots that were distributed to the collaborators. Properties from the atomic scale to the macroscale, including composition and elemental impurities, phase purity, density, thermal properties, mechanical properties, optical and vibrational properties, and the results of molecular dynamics simulations are presented. In addition, information on the surface composition and morphology after polishing is included. Although the existing literature on the alteration of ISG is not extensively reviewed here, the results of well-controlled static alteration experiments are presented here as a point of reference for other performance investigations.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Tuning optical properties of transparent conducting barium stannate by dimensional reduction

We report calculations of the electronic structure and optical properties of doped n-type perovskite BaSnO 3 and layered perovskites. While doped BaSnO 3 retains its transparency for energies below the valence to conduction band onset, the doped layered compounds exhibit below band edge optical conductivity due to transitions from the lowest conduction band. This gives absorption in the visible for Ba 2 SnO 4 . It is important to minimize this phase in transparent conducting oxide (TCO) films. Ba 3 Sn 2 O 7 and Ba 4 Sn 3 O 10 have strong transitions only in the red and infrared, respectively. Thus, there may be opportunities for using these as wavelength filtering TCO.

36 MATERIALS SCIENCE↗
DOE OSTI2023

MAX-Phase Partial Optical Properties

The optical and electrical properties of MAX-phase materials have been thoroughly studied in the past. We present here a new technique to determine and study the partial contributions to the optical properties. Following the same methodology as the decomposition of the density of states to the partial density of states, we have decomposed the optical properties into the partial optical properties. Using this technique the differences of elemental and layer resolved optical properties are displayed for both the 211 and 312 phase of TiSiC and TiAlC MAX-phase materials.

Weigand, Alysse↗
DOE OSTI2017

Controlled optical properties via chemical composition tuning in molybdenum-incorporated β-Ga 2 O 3 nanocrystalline films

An approach is presented to design refractory-metal incorporated Ga2O3-based materials with controlled structural and optical properties. The molybdenum (Mo)-content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo-content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo-content results in amorphization. Chemically-induced band gap variability (Eg~1 eV) coupled with structure-modification indicates the electronic-structure changes in Ga-Mo-O. The linear relationship between chemical-composition and optical properties suggests that tailoring the optical-quality and performance of Ga-Mo-O films is possible by tuning the Mo-content.

Environmental Molecular Sciences Laboratory↗