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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Atomic and Electronic Structure in MgO–SiO 2

Understanding disordered structure is difficult due to insufficient information in experimental data. Here, we overcome this issue by using a combination of diffraction and simulation to investigate oxygen packing and network topology in glassy (g-) and liquid (l-) MgO–SiO 2 based on a comparison with the crystalline topology. We find that packing of oxygen atoms in Mg 2 SiO 4 is larger than that in MgSiO 3 , and that of the glasses is larger than that of the liquids. Moreover, topological analysis suggests that topological similarity between crystalline (c)- and g-(l-) Mg 2 SiO 4 is the signature of low glass-forming ability (GFA), and high GFA g-(l-) MgSiO 3 shows a unique glass topology, which is different from c-MgSiO 3 . We also find that the lowest unoccupied molecular orbital (LUMO) is a free electron-like state at a void site of magnesium atom arising from decreased oxygen coordination, which is far away from crystalline oxides in which LUMO is occupied by oxygen’s 3s orbital state in g- and l-MgO–SiO 2 , suggesting that electronic structure does not play an important role to determine GFA. We finally concluded the GFA of MgO–SiO 2 binary is dominated by the atomic structure in terms of network topology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2017

Strain Monitoring of Flexible Structures

One of the biggest challenges facing NASA's deep space exploration goals is structural mass. A long duration transit vehicle on a journey to Mars, for example, requires a large internal volume for cargo, supplies and crew support. As with all space structures, a large pressure vessel is not enough. The vehicle also requires thermal, micro-meteoroid, and radiation protection, a navigation and control system, a propulsion system, and a power system, etc. As vehicles get larger, their associated systems also get larger and more complex. These vehicles require larger lift capacities and force the mission to become extremely costly. In order to build large volume habitable vehicles, with only minimal increases in launch volume and mass, NASA is developing lightweight structures. Lightweight structures are made from non-metallic materials including graphite composites and high strength fabrics and could provide similar or better structural capability than metals, but with significant launch volume and mass savings. Fabric structures specifically, have been worked by NASA off and on since its inception, but most notably in the 1990's with the TransHAB program. These TransHAB developed structures use a layered material approach to form a pressure vessel with integrated thermal and micro-meteoroid and orbital debris (MMOD) protection. The flexible fabrics allow the vessel to be packed in a small volume during launch and expand into a much larger volume once in orbit. NASA and Bigelow Aerospace recently installed the first human-rated inflatable module on the International Space Station (ISS), known as the Bigelow Expandable Activity Module (BEAM) in May of 2016. The module provides a similar internal volume to that of an Orbital ATK Cygnus cargo vehicle, but with a 77% launch volume savings. As lightweight structures are developed, testing methods are vital to understanding their behavior and validating analytical models. Common techniques can be applied to fabric materials, such as tensile testing, fatigue testing, and shear testing, but common measurement techniques cannot be used on fabric. Measuring strain in a material and during a test is a critical parameter for an engineer to monitor the structure during the test and correlate to an analytical model. The ability to measure strain in fabric structures is a challenge for NASA. Foil strain gauges, for example, are commonplace on metallic structures testing, but are extremely difficult to interface with a fabric substrate. New strain measuring techniques need to be developed for use with fabric structures. This paper investigates options for measuring strain in fabric structures for both ground testing and in-space structural health monitoring. It evaluates current commercially available options and outlines development work underway to build custom measurement solutions for NASA's fabric structures.

Litteken, Douglas A.↗
DOE OSTI2022

Understanding the Impacts of Support–Polymer Interactions on the Dynamics of Poly(ethyleneimine) Confined in Mesoporous SBA-15

Supported amines are a promising class of CO 2 sorbents offering large uptake capacities and fast uptake rates. Additionally, among supported amines, poly(ethyleneimine) (PEI) physically impregnated in the mesopores of SBA-15 silica is widely used. Within these composite materials, the chain dynamics and morphologies of PEI strongly influence the CO 2 capture performance, yet little is known about chain and macromolecule mobility in confined pores. Here, we probe the impact of the support–PEI interactions on the dynamics and structures of PEI at the support interface and the corresponding impact on CO 2 uptake performance, which yields critical structure–property relationships. The pore walls of the support are grafted with organosilanes with different chemical end groups to differentiate interaction modes (spanning from strong attraction to repulsion) between the pore surface and PEI. Combinations of techniques, such as quasi-elastic neutron scattering (QENS), 1 H T 1 –T 2 relaxation correlation solid-state NMR, and molecular dynamics (MD) simulations, are used to comprehensively assess the physical properties of confined PEI. We hypothesized that PEI would have faster dynamics when subjected to less attractive or repulsive interactions. However, we discover that complex interfacial interactions resulted in complex structure–property relationships. Indeed, both the chain conformation of the surface-grafted chains and of the PEI around the surface influenced the chain mobility and CO 2 uptake performance. By coupling knowledge of the dynamics and distributions of PEI with CO 2 sorption performance and other characteristics, we determine that the macroscopic structures of the hybrid materials dictate the first rapid CO 2 uptake, and the rate of CO 2 sorption during the subsequent gradual uptake stage is determined by PEI chain motions that promote diffusive jumps of CO 2 through PEI-packed domains.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

High Areal Capacity Si/LiCoO 2 Batteries from Electrospun Composite Fiber Mats

Here, freestanding nanofiber mat Li-ion battery anodes containing Si nanoparticles, carbon black, and poly(acrylic acid) (Si/C/PAA) are prepared using electrospinning. The mats are compacted to a high fiber volume fraction (~0.85), and interfiber contacts are welded by exposing the mat to methanol vapor. A compacted+welded fiber mat anode containing 40 wt % Si exhibits high capacities of 1,484 mA h g -1 (3,500 mA h g$-1\atop{Si}$) at 0.1 C and 489 mAh g -1 at 1 C and good cycling stability (e.g., 73% capacity retention over 50 cycles). Post-mortem analysis of the fiber mats shows that the overall electrode structure is preserved during cycling. Whereas many nanostructured Si anodes are hindered by their low active material loadings and densities, thick, densely packed Si/C/PAA fiber mat anodes reported here have high areal and volumetric capacities (e.g., 4.5 mA h cm -2 and 750 mA h cm -3 , respectively). A full cell containing an electrospun Si/C/PAA anode and electrospun LiCoO 2 -based cathode has a high specific energy density of 270 Wh kg -1 . The excellent performance of the electrospun Si/C/PAA fiber mat anodes is attributed to the: (i) PAA binder which interacts with the SiO x surface of Si nanoparticles and (ii) high material loading, high fiber volume fraction, and welded interfiber contacts of the electrospun mats

25 ENERGY STORAGE↗
DOE OSTI2011

A facile method to fabricate porous Co{sub 3}O{sub 4} hierarchical microspheres

Flower-like Co{sub 3}O{sub 4} hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. The first step involves the synthesis of flower-like Co(OH){sub 2} microspheres by a solution route at low temperatures. The second step includes the calcination of the as-prepared Co(OH){sub 2} microspheres at 200 deg. C for 1 h, causing their decomposition to form porous Co{sub 3}O{sub 4} microspheres without destruction of their original morphology. The samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffractormeter and Fourier transform infrared spectroscope. Some experimental factors including solution temperature and surfactant on the morphologies of the final products have been investigated. The magnetic properties of Co{sub 3}O{sub 4} microspheres were also investigated. - Graphical Abstract: Flower-like Co{sub 3}O{sub 4} microspheres are composed of self-assembled nanoplates and these nanoplates appear to be closely packed in the microspheres. These nanoplates consist of a large number of nanocrystallites less than 5 nm in size with a porous structure, in which the connection between nanocrystallites is random. Research Highlights: {yields} Flower-like Co{sub 3}O{sub 4} hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. {yields} Layered Co(OH){sub 2} microspheres were prepared with an appropriate approach under low temperatures for 1 h reaction. {yields} Calcination caused Co(OH){sub 2} decomposition to form porous Co{sub 3}O{sub 4} microspheres without destruction of their original morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Thickness-Dependent Order-to-Order Transitions of Bolaform-like Giant Surfactant in Thin Films

Controlling self-assembled nanostructures in thin films allows the bottom-up fabrication of ordered nanoscale patterns. Here we report the unique thickness-dependent phase behavior in thin films of a bolaform-like giant surfactant, which consists of butyl- and hydroxyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS and DPOSS) cages telechelically located at the chain ends of a polystyrene (PS) chain with 28 repeating monomers on average. In the bulk, BPOSS-PS28-DPOSS forms a double gyroid (DG) phase. Both grazing incidence small angle X-ray scattering and transmission electron microscopy techniques are combined to elucidate the thin film structures. Interestingly, films with thicknesses thinner than 200 nm exhibit an irreversible phase transition from hexagonal perforated layer (HPL) to compressed hexagonally packed cylinders (c-HEX) at 130 °C, while films with thickness larger than 200 nm show an irreversible transition from HPL to DG at 200 °C. The thickness-controlled transition pathway suggests possibilities to obtain diverse patterns via thin film self-assembly.

36 MATERIALS SCIENCE↗
DOE OSTI2024

De novo design of pH-responsive self-assembling helical protein filaments

Abstract Biological evolution has led to precise and dynamic nanostructures that reconfigure in response to pH and other environmental conditions. However, designing micrometre-scale protein nanostructures that are environmentally responsive remains a challenge. Here we describe the de novo design of pH-responsive protein filaments built from subunits containing six or nine buried histidine residues that assemble into micrometre-scale, well-ordered fibres at neutral pH. The cryogenic electron microscopy structure of an optimized design is nearly identical to the computational design model for both the subunit internal geometry and the subunit packing into the fibre. Electron, fluorescent and atomic force microscopy characterization reveal a sharp and reversible transition from assembled to disassembled fibres over 0.3 pH units, and rapid fibre disassembly in less than 1 s following a drop in pH. The midpoint of the transition can be tuned by modulating buried histidine-containing hydrogen bond networks. Computational protein design thus provides a route to creating unbound nanomaterials that rapidly respond to small pH changes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Crystal Structure of MpPR-1i, a SCP/TAPS protein from Moniliophthora perniciosa, the fungus that causes Witches’ Broom Disease of Cacao

The pathogenic fungi Moniliophthora perniciosa causes Witches’ Broom Disease (WBD) of cacao. The structure of MpPR-1i, a protein expressed by M. perniciosa when it infects cacao, are presented. This is the first reported de novo structure determined by single-wavelength anomalous dispersion phasing upon soaking with selenourea. Each monomer has flexible loop regions linking the core alpha-beta-alpha sandwich topology that comprise ~50% of the structure, making it difficult to generate an accurate homology model of the protein. MpPR-1i is monomeric in solution but is packed as a high ~70% solvent content, crystallographic heptamer. The greatest conformational flexibility between monomers is found in loops exposed to the solvent channel that connect the two longest strands. MpPR-1i lacks the conserved CAP tetrad and is incapable of binding divalent cations. MpPR-1i has the ability to bind lipids, which may have roles in its infection of cacao. These lipids likely bind in the palmitate binding cavity as observed in tablysin-15, since MpPR-1i binds palmitate with comparable affinity as tablysin-15. Further studies are required to clarify the possible roles and underlying mechanisms of neutral lipid binding, as well as their effects on the pathogenesis of M. perniciosa so as to develop new interventions for WBD.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an accurate understanding of thermal characteristics at the GB can be formulated by selecting a proper bin size.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Determination of Vanadium Binding Mode on Seawater-Contacted Polyamidoxime Adsorbents

Adsorbents developed for the recovery of uranium from seawater display poor selectivity over other transition metals present in the ocean, with vanadium particularly problematic. To improve selectivity, an indispensable step is the positive identification of metal binding environments following actual seawater deployment. In this work we apply x-ray absorption fine structure (XAFS) spectroscopy to directly investigate the vanadium binding environment on seawater-deployed polyamidoxime adsorbents. Comparison of the x-ray absorption near edge spectra (XANES) reveal marked similarities to recently a reported non-oxido vanadium (V) structure formed upon binding with cyclic imidedioxime, a byproduct of generating amidoxime functionalities. Density functional theory (DFT) calculations provided a series of putative vanadium binding environments for both vanadium (IV) and vanadium (V) oxidation states, and with both amidoxime and cyclic imidedioxime. Fits of the extended XAFS (EXAFS) data confirmed vanadium (V) is bound exclusively by the cyclic imidedioxime moiety in a 1:2 metal:ligand fashion, though a modest structural distortion is also observed compared to crystal structure data and computationally optimized geometries which is attributed to morphology effects from the polymer graft chain and the absence of crystal packing interactions. These results demonstrate that improved selectivity for uranium over vanadium can be achieved by suppressing the formation of cyclic imidedioxime during preparation of polyamidoxime adsorbents for seawater uranium recovery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1965

Wire bundle formed into grids with minute interstices

Deforming the ends of a bundle of closely packed parallel wires to restrict the interstices to substantially uniform and minute dimensions produces grids or filters for ion engines. Porous metal structures made by this process are also used as fuel cell electrodes, diffusion membranes, and catalysts.

Todd, H. H.↗
NASA NTRS1984

Offshore oil in the Alaskan Arctic

Oil and gas deposits in the Alaskan Arctic are estimated to contain up to 40 percent of the remaining undiscovered crude oil and oil-equivalent natural gas within U.S. jurisdiction. Most (65 to 70 percent) of these estimated reserves are believed to occuur offshore beneath the shallow, ice-covered seas of the Alaskan continental shelf. Offshore recovery operations for such areas are far from routine, with the primary problems associated with the presence of ice. Some problems that must be resolved if efficient, cost-effective, environmentally safe, year-round offshore production is to be achieved include the accurate estimation of ice forces on offshore structures, the proper placement of pipelines beneath ice-produced gouges in the sea floor, and the cleanup of oil spills in pack ice areas.

Weeks, W. F.↗
NASA NTRS1989

Transient oxidation of single-crystal beta-NiAl

The transient oxidation of beta-NiAl in air at 800 C and 1100 C has been studied using electron microscopy. The oxide scale consists predominantly of metastable Al2O3 phases. Theta-Al2O3 is the major oxide phase within 10.0 hr of oxidation at 800 C and 0.1 hr at 1100 C. The scales form epitaxially on (001) sub beta and (012) sub beta specimens throughout the transient stage, whereas the degree of preferred oxide orientation decreases with oxidation time on (011) sub beta and (111) sub beta specimens. The orientation relationships reflect the small mismatch between parallel close-packed directions in the metal and in the cation sublattice of the oxides. The correlation of distinctive oxide surface morphologies with internal structural defects indicates the strong tendency of the Al2O3 scale to grow via short-circuit diffusion paths.

Doychak, J.↗
NASA NTRS2012

An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications

At low operating temperatures, commercially available electrode materials for lithium-ion batteries do not fully meet the energy and power requirements for NASA fs exploration activities. The composite cathode under development is projected to provide the required energy and power densities at low temperatures and its usage will considerably reduce the overall volume and weight of the battery pack. The newly developed composite electrode material can provide superior electrochemical performance relative to a commercially available lithium cobalt system. One advantage of using a composite cathode is its higher energy density, which can lead to smaller and lighter battery packs. In the current program, different series of layered-spinel composite materials with at least two different systems in an integrated structure were synthesized, and the volumetric and gravimetric energy densities were evaluated. In an integrated network of a composite electrode, the effect of the combined structures is to enhance the capacity and power capabilities of the material to levels greater than what is possible in current state-of-the-art cathode systems. The main objective of the current program is to implement a novel cathode material that meets NASA fs low temperature energy density requirements. An important feature of the composite cathode is that it has at least two components (e.g., layered and spinel) that are structurally integrated. The layered material by itself is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated, thereby delivering a large amount of energy with stable cycling. A key aspect of the innovation has been the development of a scalable process to produce submicronand micron-scale particles of these composite materials. An additional advantage of using such a composite electrode material is its low irreversible loss (.5%), which is primarily due to the unique activation of the composite. High columbic efficiency (greater than 99%) upon cycling may indicate the formation of a stable SEI (solid-electrolyte interface) layer, which can contribute to long cycle life. The innovation in the current program, when further developed, will enable the system to maintain high energy and power densities at low temperatures, improve efficiency, and further stabilize and enhance the safety of the cell.

Hagh, Nader↗
DOE OSTI2011

A Comparison of Cocrystal Structure Solutions from Powder and Single Crystal Techniques

We demonstrate the effectiveness and accuracy of high resolution powder diffraction for determination of cocrystal structures through a double-blind study. Structures of 10 cocrystals of varying complexity were determined independently using single crystal and powder techniques. The two methodologies give identical molecular packing and hydrogen bond topology, and an rms difference in covalent bond lengths of 0.035 {angstrom}. Powder techniques are clearly sufficient to establish a complete characterization of cocrystal geometry.

08 HYDROGEN↗
DOE OSTI2018

Unraveling the Main Chain and Side Chain Effects on Thin Film Morphology and Charge Transport in Quinoidal Conjugated Polymers

Three series of low-bandgap polymers based on a novel quinoidal para -azaquinodimethane ( p -AQM) unit are devised and synthesized, enabling an in-depth study of the impact of structural factors such as polymer main chain, branching point of the side chain, and the length of the branch chains on the thin film morphologies and charge transport properties. Morphological studies reveal that the polymers composed of larger repeating units exhibit a stronger tendency to form edge-on lamella. In contrast, altering the side chain structures of polymers with the same main chain configuration indicates that the branching point position has a more deterministic impact than the branch chain length on the interchain interactions and the crystallite orientation. These results demonstrate a compound odd-even effect of the branching point on the chain packing and morphology, which correlates well with the corresponding field effect transistor performances. The polymer with the branching point at the fourth carbon displays the highest charge carrier mobility over 1.0 cm 2 V-Three series of low-bandgap polymers based on a novel quinoidal para -azaquinodimethane ( p -AQM) unit are devised and synthesized, enabling an in-depth study of the impact of structural factors such as polymer main chain, branching point of the side chain, and the length of the branch chains on the thin film morphologies and charge transport properties. Morphological studies reveal that the polymers composed of larger repeating units exhibit a stronger tendency to form edge-on lamella. On the other hand, altering the side chain structures of polymers with the same main chain configuration indicates that the branching point position has a more deterministic impact than the branch chain length on the interchain interactions and the crystallite orientation. These results reflect a compound odd-even effect of the branching point on the chain packing and morphology, which correlates well with the corresponding field effect transistor performances. The polymer with the branching point at the fourth carbon displays the highest charge carrier mobility over 1.0 cm 2 V -1 s -1 , concurrent with a bimodal texture. This study provides a comprehensive description of the correlations between polymer structures, thin film morphology, and device performances, providing a clear path to desirable bimodal thin film texture for charge transport.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Art and Science of the Cellular Mesoscale

Experimental information from microscopy, structural biology, and bioinformatics may be integrated to build structural models of entire cells with molecular detail. This integrative modeling is challenging in several ways: the intrinsic complexity of biology results in models with many closely packed and heterogeneous components; the wealth of available experimental data is scattered among multiple resources and must be gathered, reconciled, and curated; and computational infrastructure is only now gaining the capability of modeling and visualizing systems of this complexity. We present recent efforts to address these challenges, both with artistic approaches to depicting the cellular mesoscale, and development and application of methods to build quantitative models.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Crystal structure and redox potentials of the tppz-bridged {RuCl(bpy)} + dimer

We report the structural and electrochemical characterization of the binuclear complex [μ-(C 24 H 16 N 6 ){RuCl(C 10 H 8 N 2 )} 2 ](PF 6 ) 2 , which contains the bis-tridentate bridging ligand 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine (tppz), the monodentate ligand Cl − , and the bidentate ligand 2,2′-bipyridine (bpy) {systematic name: μ-2,3,5,6-tetrakis(pyridin-2-yl)pyrazine-bis[(2,2′-bipyridine)chloridoruthenium(II)] bis(hexafluoridophosphate)}. The complete [(bpy)(Cl)Ru(tppz)Ru(Cl)(bpy)] 2+ dication is generated by crystallographic twofold symmetry; the tppz bridging ligand has a significantly twisted conformation, with an average angle of 42.4° between the mean planes of adjacent pyridyl rings. The metal-coordinated chloride ligands are in a trans configuration relative to each other across the {Ru(tppz)Ru} unit. The Ru II ion exhibits a distorted octahedral geometry due to the restricted bite angle [160.6 (3)°] of the tppz ligand. For bpy, the bond lengths of the Ru—N bonds are 2.053 (8) and 2.090 (8) Å, with the shorter bond being opposite to Ru—Cl. For the tridentate tppz, the Ru—N distances involving the outer N atoms trans to each other are 2.069 (8) and 2.072 (9) Å, whereas the Ru—N bond involving the central N atom has the much shorter length of 1.939 (7) Å as a result of the geometric constraints and stronger π-acceptor ability of the pyrazine-centered bridge. The Ru—Cl distance is 2.407 (3) Å and the intramolecular distance between Ru centers is 6.579 (4) Å. In the crystal, weak C—H...Cl and C—H...F interactions consolidate the packing.

36 MATERIALS SCIENCE↗