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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

On the penetration of the 660 km phase change by mantle downflows

We present a simple analytic model of the interaction of cold convective downwelling currents with an endothermic phase change. The model describes the ponding and lateral spreading of downflows along the phase transition interface. A simple comparison of the vertical forces on the ponding material provides a necessary condition for a downflow to penetrate the phase boundary. This condition is fundamentally dependent on the geometry of the downflow. For planar downwellings, the model predicts a minimum ponding time before the structure can penetrate the phase boundary. For columnar (axisymmetric) downflows, there is no minimum time of spreading required before penetration can proceed. The model thus provides an explanation for the observation that in numerical models of three-dimensional convection with an endothermic phase change, cylindrical downflows penetrate the phase interface while planar ones do not. Since descending slabs in the Earth's mantle display a wide spectrum of geometries between planar and cylindrical (given various trench curvatures, as well as intersections of two or more subduction zones), this phenomenon may explain, in part, why some slabs appear to extend into the lower mantle while others are deflected at the 660 km discontinuity.

Bercovici, David↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is alpha-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Rb is bonded in a distorted hexagonal planar geometry to six equivalent Rb atoms. There are a spread of Rb–Rb bond distances ranging from 4.58–4.97 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on B2Pb6SO12 by Materials Project

B2Pb6SO12 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.38–1.40 Å. There are four inequivalent Pb+3.33+ sites. In the first Pb+3.33+ site, Pb+3.33+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.20–2.78 Å. In the second Pb+3.33+ site, Pb+3.33+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.31–2.88 Å. In the third Pb+3.33+ site, Pb+3.33+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.22–2.75 Å. In the fourth Pb+3.33+ site, Pb+3.33+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.45–2.52 Å. S2- is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.49–1.52 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Pb+3.33+ and one S2- atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one B3+ and two Pb+3.33+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one B3+ and two Pb+3.33+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one B3+ and two Pb+3.33+ atoms. In the fifth O2- site, O2- is bonded to four Pb+3.33+ atoms to form distorted corner-sharing OPb4 tetrahedra. In the sixth O2- site, O2- is bonded in a single-bond geometry to three Pb+3.33+ and one S2- atom. In the seventh O2- site, O2- is bonded in a trigonal planar geometry to three Pb+3.33+ atoms. In the eighth O2- site, O2- is bonded in a single-bond geometry to one S2- atom.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Liquid phase epitaxy growth of GaAs/GaAlAs multi-quantum well structures

Experiments in liquid phase epitaxial fabrication of thin GaAs/GaAlAs layers over a planar substrates have been carried out. Layer thicknesses smaller than 300 A were routinely obtained, with the best result being 120 A. Interface sharpness between the layers is approximately 10 A, which is comparable to OMCVD results, but the layers' thicknesses are usually not uniform. Of the experimental parameters, the growth time and the cooling rate seem to have the largest effect on the obtained layer thickness, while the growth temperature and the substrate crystallographic orientation produce less noticeable effects. Quantum effects in the grown layers were observed by photoluminescence measurements.

Cser, J.↗
DOE OSTI2020

Materials Data on LaSi2Ru3 by Materials Project

LaRu3Si2 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. La2+ is bonded in a hexagonal planar geometry to six equivalent Si4- atoms. All La–Si bond lengths are 3.29 Å. Ru2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Ru–Si bond lengths are 2.44 Å. Si4- is bonded in a 9-coordinate geometry to three equivalent La2+ and six equivalent Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaSi2Ru3 by Materials Project

LaRu3Si2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. La2+ is bonded in a hexagonal planar geometry to six equivalent Si4- atoms. All La–Si bond lengths are 3.30 Å. Ru2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Ru–Si bond lengths are 2.44 Å. Si4- is bonded in a 6-coordinate geometry to three equivalent La2+ and six equivalent Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NdSi2Ru3 by Materials Project

NdRu3Si2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Nd2+ is bonded in a hexagonal planar geometry to six equivalent Si4- atoms. All Nd–Si bond lengths are 3.26 Å. Ru2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Ru–Si bond lengths are 2.44 Å. Si4- is bonded in a 9-coordinate geometry to three equivalent Nd2+ and six equivalent Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmSi2Ru3 by Materials Project

SmRu3Si2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Sm2+ is bonded in a hexagonal planar geometry to six equivalent Si4- atoms. All Sm–Si bond lengths are 3.24 Å. Ru2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Ru–Si bond lengths are 2.43 Å. Si4- is bonded in a 9-coordinate geometry to three equivalent Sm2+ and six equivalent Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiNO3 by Materials Project

LiNO3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Li1+ is bonded in a hexagonal planar geometry to six equivalent O2- atoms. All Li–O bond lengths are 2.06 Å. N5+ is bonded in a hexagonal planar geometry to six equivalent O2- atoms. All N–O bond lengths are 2.06 Å. O2- is bonded in a 4-coordinate geometry to two equivalent Li1+ and two equivalent N5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2P2PdO7 by Materials Project

PdAg2P2O7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.04 Å) and two longer (2.05 Å) Pd–O bond lengths. Ag1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ag–O bond distances ranging from 2.36–2.76 Å. P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.52–1.63 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Ag1+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P5+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Pd2+, two equivalent Ag1+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Pd2+, one Ag1+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Curvature-induced hydrophobicity at imogolite–water interfaces

Imogolite, a nanotubular aluminosilicate mineral, is commonly found in volcanic soils, where it exerts a control on carbon dynamics. Synthetic imogolites are used for the removal of contaminants from industrial effluents and are considered for a range of other applications including gas adsorption and functionalised heterogeneous catalysts. In spite of their environmental and industrial relevance, the properties of imogolite–water interfaces remain poorly understood. In this work, an experimental and computational study is presented in which the structure and energetics of water are characterized on the curved external surface of imogolite and the hydrophilicity of this surface is contrasted with that of gibbsite, its planar counterpart. Atomic force spectroscopy experiments show that in spite of their identical surface structure, imogolite has a lower hygroscopicity than gibbsite. Molecular dynamics simulations provide an explanation for this observation: the curvature of imogolite prevents the formation of in-plane H-bonds along the directions of the nanotube circumference, lowering the enthalpy of adsorption of water molecules. The different arrangement of surface H-bonds and the resulting differences in hydration properties also affects the acidity constants of surface hydroxyl groups. This ‘nanotube effect’ may be relevant to other nanotubular systems with high curvatures, potentially impacting their wetting properties, their colloidal stability and their affinity towards hydrophobic organic moieties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrLa2Cl8 by Materials Project

SrLa2Cl8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sr2+ is bonded in a distorted square co-planar geometry to four Cl1- atoms. There are two shorter (3.03 Å) and two longer (3.14 Å) Sr–Cl bond lengths. La3+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of La–Cl bond distances ranging from 2.88–2.95 Å. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted water-like geometry to two equivalent La3+ atoms. In the second Cl1- site, Cl1- is bonded in a trigonal non-coplanar geometry to one Sr2+ and two equivalent La3+ atoms. In the third Cl1- site, Cl1- is bonded in a distorted trigonal planar geometry to one Sr2+ and two equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2S by Materials Project

Cu2S crystallizes in the tetragonal P4_32_12 space group. The structure is three-dimensional. Cu1+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. There are a spread of Cu–S bond distances ranging from 2.29–2.32 Å. S2- is bonded in a 6-coordinate geometry to six equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Finite Element Analysis of a Deployable Space Structure

The dynamic characteristics of the Solar Array Flight Experiment (SAFE) structure during deployment and retraction are investigated. The SAFE structure consists of a deployable mast with an attached solar blanket designed with accordion type folds to permit packaging in a small volume. The planar form of the blanket geometry during deployment is maintained by a blanket tension/guidewire system. Structurally, the mast is modeled as an Euler beam column with inplane and out of plane bending and finite torsional stiffness. For out of plane motion, the blanket is modeled as a distributed mass uniformly supported by the three guidewires. For inplane motion the blanket displacements are assumed to vary linearly from the mast base to the mast tip. The mathematical model uses a virtual work formulation, required because the axial loading on the mast is nonconservative, combined with assumed beam modes to derive the differential equations of motion. Consideration of the time dependent boundary conditions results in an infinite set of ODE with time dependent coefficients. Finally, correlation of mast tip accelerations to mast base bending moments for specified modal motions are indicated.

Weeks, G. E.↗
NASA NTRS1991

Concepts, analysis and development for precision deployable space structures

Several issues surrounding the development of large Precision Segmented Reflector (PSR) designs are investigated. The concerns include nonlinear dynamics of large unruly masses such as the multi-layer thermal insulation of sunshades for instruments such as the precision pointing 20-m-diameter Large Deployable Reflector (LDR). A study of the residual oscillations after bang-bang reorientation maneuvers of a rigid satellite with a string appendage is presented. Application is made to the design of a sunshade (thermal blanket) for the LDE satellite. Another concern is the development of a deployable truss that has minimum structural redundancy (such as the tetrahedral truss) and that can be configured with planar and doubly curved geometries. A kinematically synchronized articulation scheme for a deployable tetrahedral truss is presented. Called the Tetrapac, this truss is currently limited to a planar configuration that has two rings. The final concern is the development and demonstration of hardware that enables astronauts to attach large, cumbersome, and fragile precision reflector segments to an erectable truss structure. This task must be accomplished with a high degree of precision and with relative ease. A design for a Panel Attachment Device (PAD) was developed and manufactured for neutral buoyancy simulations to be performed by LaRC.

Miller, Richard K.↗
DOE OSTI2025

Lines of Bound States in the Continuum in Monodisperse Microsphere Structures

Incorporating epitaxially grown active semiconductor media into self-assembled microsphere crystals has remained a major challenge as the curved geometry of the spheres is incompatible with conventional planar growth and patterning techniques. As a result, active photonic devices based on such self-assembled structures, which have other desirable properties such as enabling the rapid assembly of large area systems, have been elusive. Here, we numerically demonstrate an alternative route to creating high-Q resonances in microsphere-based nanophotonic assemblies compatible with standard optical gain materials. We show that close-packed layers of monodisperse microspheres can exhibit symmetry bandgaps, regardless of their layer stacking order. Thus, this microsphere environment can be used to create lines of bound states in the continuum (BICs) of an embedded slab made of active material. Using a realistic ZnS@SiO 2 (core-shell) architecture and sphere diameters compatible with scalable colloidal assembly, we predict sharp spectral features in angle-resolved transmission that trace these lines of BICs and persist in the presence of some fabrication disorder. Altogether, in enabling the integration of unpatterned epitaxial gain slabs with large-area colloidal microsphere assemblies, this approach opens a practical path toward active, dynamically reconfigurable photonic devices that leverage BIC physics for narrow-linewidth lasing and enhanced light–matter interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Materials Data on LiFeSiO4 by Materials Project

LiFeSiO4 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. Li1+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of Li–O bond distances ranging from 1.93–1.96 Å. Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.86–1.91 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four equivalent FeO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Li1+, one Fe3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Fe3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Li1+, one Fe3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Rb 4 CuSb 2 Cl 11 and Rb 2 In 0.91(0.2) Sb 0.09 Cl 5 ·H 2 O: Wide Band Gap 0D Metal Halide Semiconductors

Herein, we report the discovery, structural and photophysical characterization of a new zero-dimensional (0D) lead-free all-inorganic halide, Rb 4 CuSb 2 Cl 11 , which adopts a new structure type. Single-crystal X-ray diffraction (SCXRD) shows that the structure consists of isolated, distorted seesaw [SbCl 4 ] − and trigonal planar [CuCl 3 ] 2− units, separated by Rb + cations that provide charge balance. Optoelectronic measurements and density functional theory (DFT) calculations indicate an indirect band gap of 2.89 eV, making it a candidate for wide-bandgap optoelectronic applications. Electrical resistivity was measured at 1.29 × 10 10 Ω·cm, and the trap-state density (n trap ) was found to be 7.44 × 10 10 cm −3 . Attempts to synthesize substitution analogs of Rb 4 CuSb 2 Cl 11 led to the synthesis of Rb 2 In 0.91(0.2) Sb 0.09 Cl 5 ·H 2 O, which was erroneously reported as Rb 2 SbCl 5 O in a previous study. Rb 2 In 0.91(0.2) Sb 0.09 Cl 5 ·H 2 O adopts a vacancyordered perovskite structure and exhibits broad-band yellow emission under UV excitation. The measured photoluminescence quantum yield (PLQY) for Rb 2 In 0.91 (0.2)Sb 0.09 Cl 5 ·H 2 O is 18.2%. These findings add to the growing class of quaternary metal halides with multiple cation and anion compositions, expanding the chemical phase space for the discovery of new materials with functional properties.

Crystal structure↗