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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Measured space environmental effects to LDEF during retrieval

On the STS-32 shuttle mission, a space flight experiment provided an understanding of the effects of the space environment on the Long Duration Exposure Facility (LDEF) from rendezvous with the shuttle until removal from the payload bay at the Orbiter Processing Facility (OPF) at KSC. The Interim Operational Contamination Monitor (IOCM) is an attached shuttle payload that has been used on two earlier flights (STS 51C and STS 28) to quantify the contamination deposited during the course of the mission. The IOCM can characterize by direct measurement, the deposition of molecular and particulate contamination during any phase of flight. In addition to these principal measurements, the IOCM actively measures the thermophysical properties of thermal control surfaces by calorimetry, the flux of the ambient atomic oxygen environment, the incident solar flux, and the absolute ambient pressure in the payload bay. The IOCM also provides a structure and sample holders for the exposure of passive material samples to the space environment, e.g. thermal cycling, atomic oxygen, and micrometeoroids and/or orbital debris, etc. One of the more salient results from the STS-32 flight suggests that the LDEF emitted a large number of particulates after berthing into the shuttle. The mission atomic oxygen fluence was also calculated. Although the fluence was low by normal standards, the Kapton passive samples exhibited the onset of erosion. Orbital debris and micrometeoroid impacts also occurred during the retrieval mission. The average perforation diameter was approximately 12.5 microns. The largest perforation diameter was measured at 65 microns.

Maag, Carl R.↗
NASA NTRS1992

Human exposure to large solar particle events in space

Whenever energetic solar protons produced by solar particle events traverse bulk matter, they undergo various nuclear and atomic collision processes which significantly alter the physical characteristics and biologically important properties of their transported radiation fields. These physical interactions and their effect on the resulting radiation field within matter are described within the context of a recently developed deterministic, coupled neutron-proton space radiation transport computer code (BRYNTRN). Using this computer code, estimates of human exposure in interplanetary space, behind nominal (2 g/sq cm) and storm shelter (20 g/sq cm) thicknesses of aluminum shielding, are made for the large solar proton event of August 1972. Included in these calculations are estimates of cumulative exposures to the skin, ocular lens, and bone marrow as a function of time during the event. Risk assessment in terms of absorbed dose and dose equivalent is discussed for these organs. Also presented are estimates of organ exposures for hypothetical, worst-case flare scenarios. The rate of dose equivalent accumulation places this situation in an interesting region of dose rate between the very low values of usual concern in terrestrial radiation environments and the high-dose-rate values prevalent in radiation therapy.

Townsend, L. W.↗
NASA NTRS1993

Measured space environmental effects to LDEF during retrieval

Data gathered by the Interim Operational Contamination Monitor (IOCM) with regard to the effect of the space environment on the STS-32 Shuttle mission and on the Long Duration Exposure Facility (LDEF) are reported. IOCM measures the deposition of molecular and particulate contamination during all flight phases. It also measures the thermophysical properties of thermal control surfaces by calorimetry, the flux of the ambient atomic oxygen environment, the incident solar flux, and the absolute ambient pressure in the payload bay. The IOCM also provides a structure and sample holders for the exposure of passive material samples to the space environment. One of the more salient results from the STS-32 flight suggests that the LDEF emitted a large number of particulates after berthing into the Shuttle. The mission atomic oxygen fluence was also calculated. Although the fluence was low by normal standards, the Kapton (trademark) passive samples exhibited the onset of erosion. Orbital debris and micrometeoroid impacts also occurred during the retrieval mission. The average perforation diameter was approximately 1.25 micrometers. The largest perforation diameter was measured at 65 micrometers.

Maag, Carl R.↗
NASA NTRS2000

X-Ray Line Spectroscopy of Massive X-Ray Binaries

Spectra from ASCA have provided the most, detailed view to date of the X-ray spectral properties of stellar winds in massive X-ray binaries. Using detailed atomic models that account for recombination cascade kinetics, we have reexamined archival data from Vela X-1 and Cen X-3 in the context of simple models of their wind geometries and velocity distributions. Our approach emphasizes apparent differential emission measure (DEM) distributions, and their dependence on orbital phase and wind parameters. A grid of theoretical DEM distributions is used to generate model spectra, which are compared to the data. We obtain good fits, and derive constraints oil the stellar wind parameters. We provide a summary of the method, and show that, even though the companion stars in Vela X-1 and Cen X-3 have comparable mass-loss rates, the winds in these two systems are dramatically different, in character.

Liedahl, D. A.↗
NASA NTRS2010

Space Environment Effects on Silicone Seal Materials

A docking system is being developed by the NASA to support future space missions. It is expected to use redundant elastomer seals to help contain cabin air during dockings between two spacecraft. The sealing surfaces are exposed to the space environment when vehicles are not docked. In space, the seals will be exposed to temperatures between 125 to -75 C, vacuum, atomic oxygen, particle and ultraviolet radiation, and micrometeoroid and orbital debris (MMOD). Silicone rubber is the only class of space flight-qualified elastomeric seal material that functions across the expected temperature range. NASA Glenn has tested three silicone elastomers for such seal applications: two provided by Parker (S0899-50 and S0383-70) and one from Esterline (ELA-SA-401). The effects of atomic oxygen (AO), UV and electron particle radiation, and vacuum on the properties of these three elastomers were examined. Critical seal properties such as leakage, adhesion, and compression set were measured before and after simulated space exposures. The S0899-50 silicone was determined to be inadequate for extended space seal applications due to high adhesion and intolerance to UV, but both S0383-70 and ELA-SA-401 seals were adequate.

deGroh, Henry C., III↗
DOE OSTI2020

Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems

Over the last few years, extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high degree of precision. An appealing and challenging route toward engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind, i.e., to provide a unique framework that allows us to describe non-equilibrium phenomena in molecular complexes, low dimensional materials, and extended systems by accounting for electronic, ionic, and photon quantum mechanical effects within a generalized time-dependent density functional theory. This article aims to present the new features that have been implemented over the last few years, including technical developments related to performance and massive parallelism. We also describe the major theoretical developments to address ultrafast light-driven processes, such as the new theoretical framework of quantum electrodynamics density-functional formalism for the description of novel light–matter hybrid states. Those advances, and others being released soon as part of the Octopus package, will allow the scientific community to simulate and characterize spatial and time-resolved spectroscopies, ultrafast phenomena in molecules and materials, and new emergent states of matter (quantum electrodynamical-materials).

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Monte Carlo simulations of Cu/Ni–Si–Mn co-precipitation in duplex stainless steels

First-Passage Kinetic Monte Carlo (FPKMC) simulations of species migration in duplex stainless steels were performed in order to establish relationships between alloy content, segregation behavior, and the formation of Ni-Si-Mn rich particles in cast duplex stainless steels during thermal aging. The Ni-Si-Mn-rich second phase forms after extended aging at reactor operating temperatures and degrades alloy properties. Simulations of Ni-Si-Mn cluster formation were validated through comparison with experimental results obtained through Atom Probe Tomography (APT) on similar alloy compositions, identifying several trends. First, Cu promotes the formation of Ni-Si-Mn clusters, but only when Ni or Mn prefer segregation to the surface of Cu particles; without the segregation of these species, the critical composition for the clusters to form was not achieved. Second, the width of precipitate-denuded zones near ?/d interfaces increases with decreasing Cu content. This finding was in strong agreement with APT results, further validating our model. Finally, our model predicts that Ni-Si-Mn cluster formation will be the most extensive when the Si:Mn ratio is approximately 1:1 and the least extensive when one of these key elements is less concentrated (Mn = 0.5 at.% or Si = 0.5 at.%). The implications of these results on how to improve alloy properties are discussed.

Cu co-precipitation, Atom probe tomography (APT), ↗
DOE OSTI2022

Accelerated screening of functional atomic impurities in halide perovskites using high-throughput computations and machine learning

The pressing need for novel materials that can serve rising demands in solar cell and optoelectronic technologies makes the nexus of halide perovskites, high-throughput computations, and machine learning, very promising. Ever increasing amounts of data on the structure, fundamental properties, and device performance of halide perovskites provide opportunities for learning chemical rules and design principles that make these materials attractive, and applying them across wide chemical spaces. In this work, we show that impurity properties of halide perovskites computed using density functional theory (DFT) can be combined with machine learning (ML) to deliver predictive models and quick identification of optoelectronically active impurity atoms. Our computation lead to the largest reported dataset of the formation energies and charge transition levels of Pb-site impurities in methylammonium lead halide (MAPbX 3 ) perovskites. Descriptors are defined to uniquely represent any impurity atom in any MAPbX 3 compound and mapped to the computed impurity properties using regression techniques such as Gaussian process regression, neural networks, and random forests. We use the best optimized predictive models to make predictions for hundreds of impurities across 9 MAPbX 3 compounds and create lists of dominating impurities, that is, impurities that can shift the equilibrium Fermi level in the perovskite as determined by native point defects. Finally, this accelerated screening powered by computations and machine learning can guide the identification of problematic impurities that may cause undesired recombination of charge carriers, as well as impurities that can be deliberately introduced to tune the perovskite conductivity and resulting photovoltaic absorption.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Direct Observation of Twin van der Waals Molecular Chains

The van der Waals (vdW) assemblies are the most common structures of materials. However, directly mapping intermolecular electron clouds of a vdW assembly has never been obtained, even though the intramolecular electron clouds were visualized by atomic-resolution techniques. In this report, we unprecedently mapped the intermolecular electron cloud of the assembles of ethanol molecules via ethyl groups with noncontact atomic force microscopy at 5 K, leading to the first visualization of vdW molecular chains, in which ethanol molecules assemble into twin vdW molecular chains in a reverse parallel configuration on Ag(111) plane. Furthermore, spontaneous order-disorder transitions in the chain were dynamically observed, suggesting its unusual properties different from 2D vdW materials. In conclusion, these findings provide an "eye" to see the atomic world of vdW materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2021

MISSE-Flight Facility Polymers and Composites Experiment 1-4 (PCE 1-4)

Spacecraft in low Earth orbit (LEO) are subjected to harsh environmental conditions, including radiation (cosmic rays, ultraviolet (UV), x-ray and charged particle radiation), micrometeoroids and orbital debris, temperature extremes, thermal cycling, and atomic oxygen (AO). These environmental exposures can result in erosion, embrittlement and optical property degradation of susceptible materials threatening spacecraft performance and durability. To increase our understanding of effects such as AO erosion and radiation induced embrittlement of spacecraft materials, NASA Glenn Research Center has developed a series of experiments that are flown as part of the Materials International Space Station Experiment (MISSE) missions on the exterior of the International Space Station (ISS). These experiments have provided critical space environmental durability data such as AO erosion data of polymers and composites, and radiation induced mechanical property degradation of spacecraft insulation materials, after long term space exposure. In continuing these studies, four Glenn experiments have been flown on ISS’s MISSE-Flight Facility (MISSE-FF). These experiments are the Polymers and Composites Experiment-1 (PCE-1) flown as part of the inaugural MISSE-9 mission, the PCE-2 flown as part of the MISSE-10 mission, the PCE-3 being flown as part of the MISSE-12 mission, and the PCE-4 being flown as part of the MISSE-13 mission. This paper provides an overview of space environmental effects on spacecraft materials and Glenn’s PCE 1-4 MISSE-FF experiments.

Atomic oxygen↗
DOE OSTI2020

Molecular Picture of the Transient Nature of Lipid Rafts

In biological membranes, lipid rafts are now thought to be transient and nanoscopic. However, the mechanism responsible for these nanoscopic assemblies remains poorly understood, even in the case of model membranes. Therefore, it has proven extremely challenging to probe the physicochemical properties of lipid rafts at the molecular level. Here, we use all-atom molecular dynamics (MD) simulations and inelastic X-ray scattering (IXS), an intrinsically nanoscale technique, to directly probe the energy transfer and collective short-wavelength dynamics (phonons) of biologically relevant model membranes. We show that the nanoscale propagation of stress in lipid rafts takes place in the form of collective motions made up of longitudinal (compression waves) and transverse (shear waves) molecular vibrations. Importantly, we provide a molecular picture for the so-called van der Waals mediated "force from lipid" [Anishkin, A. et al. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 7898], a key parameter for the ionic channel mechano-transduction and the mechanism for the lipid transfer of molecular level stress [Aponte-Santamaría, C. et al. J. Am. Chem. Soc. 2017, 139, 13588]. Specifically, we describe how lipid rafts are formed and maintained through the propagation of molecular stress, lipid raft rattling dynamics, and a relaxation process. Eventually, the rafts dissipate through the self-diffusion of lipids making up the rafts. We also show that the molecular stress and viscoelastic properties of transient lipid rafts can be modulated through the use of hydrophobic biomolecules such as melatonin and tryptophan. Overall, the herein proposed mechanism describing the molecular interactions for the formation and dissolution of lipid rafts may offer insights as to how lipid rafts enable biological function.

36 MATERIALS SCIENCE↗
NASA NTRS2000

Assessment of Low Cycle Fatigue Behavior of Powder Metallurgy Alloy U720

The fatigue lives of modem powder metallurgy disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary as functions of variables the different steps of materials/component processing: powder atomization, consolidation, extrusion, forging, heat treating, and machining. It is important to understand the relationship between the statistical variations in life and these variables, as well as the change in life distribution due to changes in fatigue loading conditions. The objective of this study was to investigate these relationships in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were performed at 538 C (1000 F) at limited sets of test conditions. Analyses were performed to: (1) assess variations of microstructure, mechanical properties, and LCF failure initiation sites as functions of disk processing and loading conditions; and (2) compare mean and minimum fatigue life predictions using different approaches for modeling the data from assorted test conditions. Significant variations in life were observed as functions of the disk processing variables evaluated. However, the lives of all specimens could still be combined and modeled together. The failure initiation sites for tests performed at a strain ratio R(sub epsilon) = epsilon(sub min)/epsilon(sub max) of 0 were different from those in tests at a strain ratio of -1. An approach could still be applied to account for the differences in mean and maximum stresses and strains. This allowed the data in tests of various conditions to be combined for more robust statistical estimates of mean and minimum lives.

Gabb, Tomothy P.↗
DOE OSTI2023

Fundamental studies of thermal and electrical transport in microporous metal-organic frameworks

In this work, we established porous metal-organic frameworks (MOFs) as designer conductors of electrons and ions relevant to fundamental research and technological applications. MOFs are porous, crystalline materials composed of organic linkers and inorganic nodes. While most MOFs are insulating with respect to ionic and electronic charge carriers, a number of exceptions have been reported in recent years. Electrically conductive MOFs are highly attractive for applications including electrical energy storage, chemiresistive sensing, and optoelectronics because of their high surface areas and tunable chemical properties. Ion-conducting MOFs are desirable for the synthetically tunable size, shape, and polarity of their pore environments, allowing for the tailored development of solid state electrolytes for metal-ion batteries. We developed systematic strategies for the design of MOFs that conduct ions and electrons. For each objective, we leveraged the versatile chemistry of these materials to obtain frameworks with targeted properties towards electronic or ionic charge carriers. We studied the factors that govern electrical transport in MOFs in order to gain fundamental knowledge of this emerging class of materials. We took several approaches to tackle this problem from multiple angles. Namely, we synthesized and characterized new frameworks, investigated post-synthetic modifications to enhance conductivity, and correlated theory and experiment to uncover new mechanistic findings. These results, which put forth new design principles for conductive MOFs, move the field toward one of the DOE Basic Energy Sciences Grand Challenges: to “design and perfect atom- and energy-efficient synthesis of revolutionary new forms of matter with tailored properties.” In addition to investigating the movement of electrons in MOFs, we also studied the movement of other charged species in MOFs, such as protons, lithium, and magnesium. Proton-conducting frameworks could be appealing materials for solid state electrolytes in fuel cells. In addition, they contain crystallographically defined proton-conducting channels, in contrast with state-of-the-art polymer membranes such as Nafion, which are amorphous. Controlling pore size and polarity in MOFs can thus shed light on proton and other ion transport mechanisms, ultimately enabling the design of more advanced electrolyte materials and potentially novel electrical energy storage materials.

36 MATERIALS SCIENCE↗
NASA NTRS2007

Effect of LEO Exposure on Aromatic Polymers Containing Phenylphosphine Oxide Groups

As part of the Materials on The International Space Station Experiment (MISSE), aromatic polymers containing phenylphosphine oxide groups were exposed to low Earth orbit (LEO) for approximately 4 years. All of the aromatic polymers containing phenylphosphine oxide groups survived the exposure despite the high fluence of atomic oxygen that completely eroded other polymer films such as Kapton and Mylar of comparable or greater thickness. The samples consisted of a colorless polyimide film and a poly(arylene ether benzimidazole) film and thread. The samples were characterized for changes in physical properties, thermal/optical properties (i.e. solar absorptivity and thermal emissivity), surface chemistry (X-ray photoelectron spectroscopy), and surface topography (atomic force microscopy). The data from the polymer samples on MISSE were compared to samples from the same batch of material stored under ambient conditions on Earth. In addition, comparisons were made between the MISSE samples and those subjected to shorter term space flight exposures. The results of these analyses will be presented.

Watson, K. A.↗
DOE OSTI2024

Emerging Functionality in Transition-Metal Compounds Driven by Spatial Confinement and Broken Symmetry

This research project investigates the emerging functionality in transition-metal-compounds (TMCs) driven by spatial confinement and broken symmetry. It combines advanced growth capabilities with cutting-edge characterization and first principles theory to probe and control the properties of TMC interfaces, including the utilization and development of state-of-the-art atomically resolved electron microscopy and spectroscopy to determine the structure, composition, and bonding at TMC interfaces. The proposed research will focus on four challenging areas: 1) manipulate interfaces to design new material phases such as magnetic metals with unique polar structure (net dipole) to achieve multiple functionality; 2) explore electronic mismatch or screening at interfaces of insulating/poor metal TMCs to produce novel electronic and magnetic properties; 3) elucidate and exploit the role of defects, both point and extended, on the functionality of interfaces; 4) develop advanced electron microscopy/spectroscopy techniques to explore temperature dependent phase transitions and couple these structural tools with new nonlinear optical probes of the electronic structure. The research team aims to close the materials-by-design loop of make, measure, model, and modify. The program promises to enhance our ability to engineer the desired physical properties at interfaces, superlattices (periodic arrays of films of different compounds), and heterostructures of TMCs.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Collision integrals and high temperature transport properties for N-N, O-O, and N-O

Accurate collision integrals for the interactions of N(4S0) + N(4S0), O(3P) + O(3P), and N(4S0) + O(3P) are reported. These are computed from a semiclassical formulation of the scattering using the best available representations of all of the potential energy curves needed to describe the collisions. Spectroscopic curves and other accurate measured data are used where available; the results of accurate ab initio electronic structure calculations are used to determine the remaining potential curves. The high-lying states are found to give the largest contributions to the collision cross sections. The nine collision integrals needed to determine transport properties to second order are tabulated for translational temperatures in the range 250-100,000 K. The viscosity, thermal conductivity, diffusion coefficient, and thermal diffusion factor for a gas composed of nitrogen and oxygen atoms in thermal equilibrium have been calculated. It is found that the second-order contribution to the transport properties is small. Graphs of these transport properties for various mixture ratios are presented for temperatures in the range 5000-15,000 K.

Levin, E.↗