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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Evaluation of GLAMR-Based Calibration for SI-Traceable Field Reflectance Retrievals

The reflected solar instrument that is part of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission is being formulated with a goal of providing SI-traceable measurement of radiance that is an order of magnitude more accurate than the current imaging sensors. The Goddard Laser for Absolute Measurement of Radiance (GLAMR) is a key element to reaching such accuracy along with transferring the laboratory calibration to on-orbit measurements. Results from field reflectance retrievals using three separate instruments all of which have been calibrated using GLAMR are shown. The instruments include a commercial field spectrometer and a portable version of CLARREO's calibration demonstration system. The third instrument is NASA Goddard's Lidar, Hyperspectral and Thermal Imager (G-LiHT) which is an airborne system. All three were operated during a March 2013 measurement campaign at Red Lake Playa, Arizona as part of the on-orbit commissioning phase of Landsat 8. Reflectance is derived from near-coincident measurements by the three sensors for a small area of the playa. The retrieved results are SI-traceable and demonstrate the ability to transfer the GLAMR calibration to the field. Use of the G-LiHT data in the calibration of Landsat-7 and -8 sensors permits them both to be placed on the GLAMR-scale as well.

Angal, Amit↗
NASA NTRS2017

Solidification and Morphological Evolution of Al-Si Eutectics in Convector-Diffusive Conditions

The Al-Si material system is an important and has been studied for over half century with a focus on industrial applications in high strength and high conductivity alloys. A great deal of researches have been focused on controlling the morphology and hence performance through the addition of small impurities and by processing conditions. Most of the structure-property correlations are based on the post solidified micromorphology and growth conditions. This material system is unique and has been explored for heat spreader, controlling coefficient of expansion by adjusting composition of silicon and in designing composites. The Al-Si system is very interesting system for understanding the dendritic (Al-rich side) eutectic transition. Recently this system has been of great interest because of its applications in designing heat spreader, low temperature flux to grow SiC large substrates and in controlling the coefficient of expansion of Al-based alloys. We have performed extensive experiments to understand eutectic transition and to understand the morphological evolution in presence of impurities. We will discuss the results of dendritic transition into faceted long grains in convector-diffusive conditions. In this presentation we will present morphological transition in presence of carbon impurity and development of novel morphology.

Singh, N. B.↗
NASA NTRS2018

Microscale Fracture Testing of HfO2-Si Environmental Barrier Coatings

Environmental barrier coatings (EBCs) play a vital role in protecting advanced turbine components constructed from ceramic matrix composites. EBC performance is evaluated based on many factors such as mechanical and thermal properties and chemical stability. This study focuses on the mechanical properties of individual phases within a HfO2-Si EBC through the combined use of chevron-notched microcantilevers and finite element modeling. The Si- and HfO2-rich phases were found to have fracture toughness K(sub IC) values of 1.36+/-0.07 MPa·m1/2 and 1.99+/-0.36 MPa·m1/2, respectively. Despite irregular notch geometry, calculated K(sub IC) values agreed reasonably with literature values of monolithic samples for the respective phases. The relatively large scatter in the HfO2-rich samples is attributed to heterogeneity in fracture feature size and distribution of the HfO2 and HfSiO4 phases. Comparisons with bulk single-edge V-notched beams suggest bulk behavior is dictated by the fracture behavior of the Sirich phase with no contribution from the HfO2-rich phase.

Robertson, Andrew L.↗
NASA NTRS2018

Development of Large Bandgap Materials Using Reactive Growth in Al-SI Eutectic for Optical and RF Applications

Carbon was utilized as reactive element to modify the microstructure using forced mixing during crystallization of the Al-Si alloy by rotation and stirring. We nucleated the material on SiC substrates while the Al-Si melt was rotated with a speed of 30rpm in a graphite crucible. Several experiments were performed and parameters such as time of mixing, soaking temperature, rotation rate of the substrate and rate of cooling during the solidification was changed. We observed dendrite and cell morphologies during the solidification of rotating melt. The microstructure was characterized by optical microscopy and SEM-EDX and compositional spectroscopy. The effect of carbon impurities was studied on the solidifying microstructure. When we used the longer soak time of the melt in presence of carbon impurities we observed the destruction of dendritic morphology and the formation of cellular and colony structures. Similar approach has been used for Ga2O3, a novel large bandgap material also.

Singh, N. B.↗
NASA NTRS2019

Uncooled Doped-Si Thermopiles for Thermal Land Imaging Applications

Sustained and enhanced land imaging is crucial for providing high-quality science data on change in land use, forest health, environment, and climate. Future thermal land imaging instruments operating in the 10-12 micron band will provide essential information for furthering our hydrologic understanding at scales of human influence, and producing field-scale moisture information through accurate retrievals of evapotranspiration (ET). To address the need for cost-effective future thermal land imaging missions we are developing novel uncooled doped-silicon thermopile detectors, an extension of a detector design originally developed at NASA-Goddard for planetary science applications (Lakew et al. 2016). These doped-Si thermopile detectors have the potential to offer superior performance in terms of sensitivity, speed and customizability, when compared to current commercial-off-the-shelf uncooled detector technologies. Because cryocooling technology does not need to be fielded on the instrument, these and other uncooled detectors offer the benefit of greatly reduced instrument cost, mass, and power at the expense of some acceptable loss in detector sensitivity. We present an overview of our thermal imaging instrument concept, our doped-Si thermopile detector concept, and performance expectations and comparisons. We also provide an update on the current status of this detector technology development

Barrentine, Emily M.↗
NASA NTRS2019

Uncooled Doped-Si Thermopiles for Thermal Land Imaging Applications

Sustained and enhanced land imaging is crucial for providing high-quality science data on change in land use, forest health, environment, and climate. Future thermal land imaging instruments operating in the 10-12 micron band will provide essential information for furthering our hydrologic understanding at scales of human influence, and producing field-scale moisture information through accurate retrievals of evapotranspiration (ET). To address the need for cost-effective future thermal land imaging missions we are developing novel uncooled doped-silicon thermopile detectors, an extension of a detector design concept originally developed at NASA-Goddard for planetary science applications. These doped-Si thermopile detectors have the potential to offer superior performance in terms of sensitivity, speed, and customization, when compared to current commercial-off-the-shelf uncooled detector technologies. Because cryocooler technology does not need to be fielded on the instrument, these and other uncooled detectors offer the benefit of greatly reduced instrument cost, mass, and power at the expense of some acceptable loss in detector sensitivity. We present the motivation for an uncooled thermal imaging instrument, our doped-Si thermopile detector concept, and performance expectations and comparisons. We also provide an update on the current status of this detector technology development.

Thermopiles↗
NASA NTRS2024

Effects of CMAS Application on the Isothermal and Gradient Thermal Cycling Behavior of a Yb 2 Si 2 O 7 EBC

Environmental barrier coatings (EBCs) are critical to the continued advancement of gas turbine hot section materials technology. EBCs are required to protect Si-based ceramics such as silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMCs) from oxidation and corrosion in the combustion environment. One of the current challenges concerning EBC lifetime is the thermochemical reactions between calcium-magnesium-aluminosilicate (CMAS) deposits and the EBC that leads to changes in both composition and stress state. These changes can severely reduce the integrity of the EBC leading to crack formation, delamination, and spallation. Current techniques for evaluating CMAS in the laboratory rely on the pre-application of CMAS. Two commonly used application methods to deposit CMAS on EBC materials are tape-casting and air spray. In both methods, the CMAS is applied to the EBC surface at ambient temperature, and then subject to a heat treatment process for binder burnout. The purpose of this study is to compare the tape-cast and air spray methods on the CMAS corrosion of an ytterbium disilicate (Yb 2 Si 2 O 7 ) EBC subject to isothermal, and gradient thermal cycling. The results highlight if any differences exist in the CMAS infiltration kinetics between the two application methods.

Environmental barrier coatings (EBCs)↗
NASA NTRS2026

Global Model Estimates of Atmospheric Al, Ca, Fe, Si, and Ti from Dust and Non-Dust Aerosols Informed by EMIT Surface Mineralogy and Evaluated Against Observations

Atmospheric deposition of micro-nutrients like Fe has been shown to be important for ocean biogeochemistry. The largest source of atmospheric Fe and other elements (e.g., Ca, Al, Si, and Ti) is desert dust, although there are significant non-dust sources in some regions. However, past estimates of these elements have been substantially uncertain due to limited information about the composition of the desert source regions. Here we use elemental distributions estimated from new Earth Surface Mineral Dust Source Investigation (EMIT) observations, which provide mineralogical composition at the surface of the Earth based on imaging spectroscopy measurements from the International Space Station. We add in other sources of these elements (anthropogenic and natural) and compare to a compilation of available surface concentration data from stations over land and from shipborne observations. Our results suggest that the modeled distribution is similar to available observations, but discrepancies still exist in both natural desert dust regions as well as regions dominated by anthropogenic sources. Global budgets for the elements Ca, Al, Fe, Si, and Ti suggest that desert dust remains the dominant source for these elements but anthropogenic or volcanic sources are also important for these elements. Changes in elemental distributions since preindustrial times were also estimated.

aerosols↗
DOE OSTI2021

Dopant diffused Si surface passivation by H 2 S gas reaction and quinhydrone-methanol treatment

Phosphorus (n + ) and boron (p + ) diffused n-type textured Cz Si wafers are passivated by two different methods: gas phase H 2 S reaction and quinhydrone-methanol (QH-MeOH) solution. The dopant diffused surface passivation quality, quantified by saturation current density (J 0 ), strongly depends on the diffusion type and the passivation method. H 2 S reaction at 550ºC passivates n + diffused surface as good as state-of-the-art Si oxide/silicon nitride stack (SiO 2 /SiN X ), while QH-MeOH passivates p + diffused surface to the same level as state-of-the-art atomic layer deposited aluminum oxide / silicon nitride stack (Al 2 O 3 /SiN X ).

Das, Ujjwal↗
DOE OSTI2023

Loss Analysis and Performance Optimization Pathways of 729-mV VocSi Solar Cells with Poly-Si on Locally-Etched Dielectric Passivating Contacts

In this article, the performance analysis of a 22.5% efficient polysilicon on silicon oxide (poly-Si/SiOx) passivated contact solar cells with deliberately introduced pinholes using metal-assisted chemical etching (MACE) has been performed with the help of optical analysis using Sunsolve and electrical analysis using Quokka3. The power loss is maximum due to recombination and resistive losses in the bulk (~0.76 mW/cm2 ) followed by power loss due to rear contact recombination (~0.35 mW/cm2 ). Recombination at the front surface also contributes to 0.24 mW/cm2. The effect of improving the bulk lifetime and lowering the recombination current density at the rear side on Voc, FF and efficiency has been investigated.

MACE↗
DOE OSTI2020

Materials Data on Si(Hg2S3)2 by Materials Project

Hg4SiS6 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Hg–S bond distances ranging from 2.58–3.30 Å. In the second Hg2+ site, Hg2+ is bonded to four S2- atoms to form HgS4 tetrahedra that share corners with two equivalent HgS4 tetrahedra and corners with two equivalent SiS4 tetrahedra. There are a spread of Hg–S bond distances ranging from 2.57–2.68 Å. In the third Hg2+ site, Hg2+ is bonded to four S2- atoms to form HgS4 tetrahedra that share corners with two equivalent HgS4 tetrahedra and corners with two equivalent SiS4 tetrahedra. There are a spread of Hg–S bond distances ranging from 2.56–2.74 Å. In the fourth Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Hg–S bond distances ranging from 2.56–2.70 Å. Si4+ is bonded to four S2- atoms to form SiS4 tetrahedra that share corners with four HgS4 tetrahedra. There are a spread of Si–S bond distances ranging from 2.12–2.16 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded to four Hg2+ atoms to form corner-sharing SHg4 tetrahedra. In the second S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the third S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to three Hg2+ and one Si4+ atom. In the fifth S2- site, S2- is bonded to four Hg2+ atoms to form corner-sharing SHg4 tetrahedra. In the sixth S2- site, S2- is bonded in a 3-coordinate geometry to two Hg2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(Hg2Se3)2 by Materials Project

Hg4SiSe6 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Hg–Se bond distances ranging from 2.71–3.49 Å. In the second Hg2+ site, Hg2+ is bonded to four Se2- atoms to form HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with five HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.66–2.83 Å. In the third Hg2+ site, Hg2+ is bonded to four Se2- atoms to form HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with five HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.69–2.85 Å. In the fourth Hg2+ site, Hg2+ is bonded to four Se2- atoms to form distorted HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with six HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.69–2.84 Å. Si4+ is bonded to four Se2- atoms to form SiSe4 tetrahedra that share corners with six HgSe4 tetrahedra. There are a spread of Si–Se bond distances ranging from 2.28–2.31 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Hg2+ atoms to form distorted corner-sharing SeHg4 trigonal pyramids. In the second Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the third Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Hg2+ and one Si4+ atom. In the fifth Se2- site, Se2- is bonded to four Hg2+ atoms to form corner-sharing SeHg4 tetrahedra. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to two Hg2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(NiO2)2 by Materials Project

Ni2SiO4 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ni2+ is bonded to six equivalent O2- atoms to form NiO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with six equivalent NiO6 octahedra. All Ni–O bond lengths are 2.08 Å. Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with twelve equivalent NiO6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Si–O bond lengths are 1.67 Å. O2- is bonded in a rectangular see-saw-like geometry to three equivalent Ni2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(NiO2)2 by Materials Project

Ni2SiO4 is Ilmenite-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with eight NiO6 octahedra, corners with four equivalent SiO4 tetrahedra, edges with two equivalent NiO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–61°. There are a spread of Ni–O bond distances ranging from 2.06–2.19 Å. In the second Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with four equivalent NiO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with four NiO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are four shorter (2.09 Å) and two longer (2.13 Å) Ni–O bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six NiO6 octahedra and edges with three NiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ni2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(Bi3O5)4 by Materials Project

Bi12SiO20 crystallizes in the cubic I23 space group. The structure is three-dimensional. Si4+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Si–O bond lengths are 1.67 Å. Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.11–2.68 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Bi3+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Si4+ and three equivalent Bi3+ atoms. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three equivalent Bi3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(PbSe2)2 by Materials Project

SiPb2Se4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Pb–Se bond distances ranging from 2.90–3.67 Å. In the second Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Pb–Se bond distances ranging from 2.95–3.74 Å. Si4+ is bonded in a tetrahedral geometry to four Se2- atoms. There are three shorter (2.30 Å) and one longer (2.31 Å) Si–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted single-bond geometry to three Pb2+ and one Si4+ atom. In the second Se2- site, Se2- is bonded in a distorted single-bond geometry to four Pb2+ and one Si4+ atom. In the third Se2- site, Se2- is bonded in a distorted single-bond geometry to four Pb2+ and one Si4+ atom. In the fourth Se2- site, Se2- is bonded in a distorted single-bond geometry to three Pb2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(CN2)2 by Materials Project

SiC2N4 crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Si4+ is bonded in a tetrahedral geometry to four equivalent N3- atoms. All Si–N bond lengths are 1.69 Å. C4+ is bonded in a linear geometry to two equivalent N3- atoms. Both C–N bond lengths are 1.21 Å. N3- is bonded in a linear geometry to one Si4+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si(PbS2)2 by Materials Project

SiPb2S4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Pb–S bond distances ranging from 2.84–3.38 Å. In the second Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Pb–S bond distances ranging from 2.80–3.51 Å. Si4+ is bonded in a tetrahedral geometry to four S2- atoms. There are a spread of Si–S bond distances ranging from 2.13–2.15 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted single-bond geometry to four Pb2+ and one Si4+ atom. In the second S2- site, S2- is bonded in a distorted single-bond geometry to three Pb2+ and one Si4+ atom. In the third S2- site, S2- is bonded in a distorted single-bond geometry to three Pb2+ and one Si4+ atom. In the fourth S2- site, S2- is bonded in a distorted single-bond geometry to four Pb2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗