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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Hydrostatic pressure mapping of barium titanate phase transitions with quenched FeRh

We report a pressure study of the metamagnetic/ferroelectric hybrid heterostructure of a quenched FeRh thin film (25nm) grown on single crystal barium titanate (BTO). It has been previously reported that when the BTO undergoes a crystal transition a massive magnetization and coercivity change is triggered in the highly strain sensitive quenched FeRh thin film. Therefore quenched FeRh makes for an ideal probe for mapping a materials structural phase transitions. In this work we demonstrate this effect as a function of both temperature and hydrostatic pressure. As a result, we present the pressure dependence of the hybrid material which aligns identically with the BTO substrates pressure dependence reported in literature. The concept of combining a structural phase transitional (SPT) material with a magnetostrictive magnetic metal has been shown with vanadium oxides and our findings here prove that this methodology can be extended to strain sensitive metamagnetic materials systems in thin film, and possibly in bulk, heterostructures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Molecular dopants: Tools to control the electronic structure of metal halide perovskite interfaces

In the standard configurations of metal halide perovskite solar cell, the active layer, or absorber, follows a p-i-n or n-i-p electronic structure that is designed to enhance the separation and extraction of photo-induced charge carriers. The control of the Fermi level position across the film, between electron and hole transport layers, is therefore of paramount importance. Direct localized doping in metal halide perovskites being still elusive, the design of n-i-p and p-i-n structures has so far relied predominantly on surface and interface doping of the perovskite as well as on the control of the work function of the substrate and transport layers on which, or between which, the absorber is being placed. We provide here a short review of that work, emphasizing the fundamental studies of electronic structure performed on systems modified with organic molecular dopants. The review starts with a justification for the effectiveness of interface doping, based on the ability to move the Fermi level across the gap of the perovskite. We then review work done on the deposition of molecular oxidants and reductants on perovskite surfaces, including the mitigation of the surface states, and the impact of these dopants on energy level alignment with substrate and charge transport layers. The second part of the review focuses on the use of molecular dopants to either modify the work function of electron or hole transport layers to establish the boundary conditions for a p-i-n or n-i-p structure, or to enhance the conductivity of these layers in order to facilitate charge carrier extraction. Final considerations are also given on recent work on bulk doping of the perovskite layer with molecular dopants.

14 SOLAR ENERGY↗
NASA NTRS1992

Polarimetric emission from anisotropic media for passive remote sensing of sea ice

The polarimetric emission from an anisotropic medium with applications to the passive microwave remote sensing of sea ice is investigated. Based on the fluctuation-dissipation theory, the Stokes vector is obtained for the thermally exicted electromagnetic radiation from an anisotropic object. By modeling sea ice as a layered anisotropic medium, the Stokes vector representing the polarimetric emission is illustrated for various geophysical conditions. It is found that the difference in the brightness temperatures measured at two surface temperatures is correlated with the thickness of the sea ice. For cases where the c-axis of sea ice is aligned or not random in the horizontal plane, the calculated brightness temperatures show a periodic variation when plotted as a function of the azimuthal angle of the observation direction, indicating that the polarimetric Stokes parameters can be used to detect the direction of c-axes in sea ice.

Yueh, S. H.↗
NASA NTRS1997

New Methods for Improved Double Circular-Arc Helical Gears

The authors have extended the application of double circular-arc helical gears for internal gear drives. The geometry of the pinion and gear tooth surfaces has been determined. The influence of errors of alignment on the transmission errors and the shift of the bearing contact have been investigated. Application of a predesigned parabolic function for the reduction of transmission errors was proposed. Methods of grinding of the pinion-gear tooth surfaces by a disk-shaped tool and a grinding worm were proposed.

Litvin, Faydor L.↗
NASA NTRS2004

Formations of Tethered Spacecraft as Stable Platforms for Far IR and Sub-mm Astronomy

In this paper we describe current research in tethered formations for interferometry, and a roadmap to demonstrating the required key technologies via on-ground and in-orbit testing. We propose an integrated kilometer-size tethered spacecraft formation flying concept which enables Far IR and Sub-mm astronomy observations from space. A rather general model is used to predict the dynamics, control, and estimation performance of formations of spacecraft connected by tethers in LEO and deep space. These models include the orbital and tethered formation dynamics, environmental models, and models of the formation estimator/controller/commander. Both centralized and decentralized control/sensing/estimation schemes are possible, and dynamic ranges of interest for sensing/control are described. Key component/subsystem technologies are described which need both ground-based and in-orbit demonstration prior to their utilization in precision space interferometry missions using tethered formations. Defining an orbiting formation as an ensemble of orbiting spacecraft performing a cooperative task, recent work has demonstrated the validity of the tethering the spacecraft to provide both the required formation rigidity and satisfy the formation reconfiguration needs such as interferometer baseline control. In our concept, several vehicles are connected and move along the tether, so that to reposition them the connecting tether links must vary in length. This feature enables variable and precise baseline control while the system spins around the boresight. The control architecture features an interferometer configuration composed of one central combiner spacecraft and two aligned collector spacecraft. The combiner spacecraft acts as the formation leader and is also where the centralized sensing and estimation functions reside. Some of the issues analyzed with the model are: dynamic modes of deformation of the distributed structure, architecture of the formation sensor, and sources of dynamical perturbation that need to be mitigated for precision operation in space. Examples from numerical simulation of an envisioned scenario in heliocentric orbit demonstrate the potential of the concept for space interferometry.

Quadrelli, Marco B.↗
NASA NTRS2016

Initial Navigation Alignment of Optical Instruments on GOES-R

Post-launch alignment errors for the Advanced Baseline Imager (ABI) and Geospatial Lightning Mapper (GLM) on GOES-R may be too large for the image navigation and registration (INR) processing algorithms to function without an initial adjustment to calibration parameters. We present an approach that leverages a combination of user-selected image-to-image tie points and image correlation algorithms to estimate this initial launch-induced offset and calculate adjustments to the Line of Sight Motion Compensation (LMC) parameters. We also present an approach to generate synthetic test images, to which shifts and rotations of known magnitude are applied. Results of applying the initial alignment tools to a subset of these synthetic test images are presented. The results for both ABI and GLM are within the specifications established for these tools, and indicate that application of these tools during the post-launch test (PLT) phase of GOES-R operations will enable the automated INR algorithms for both instruments to function as intended.

geolocation↗
DOE OSTI2026

Machine learning-based interatomic potential development and phase transition analysis of ferroelectric hafnium dioxide

The ferroelectric phase (𝑃⁢𝑐⁢𝑎⁢2 1 , which is in orthorhombic symmetry) of hafnium dioxide (HfO 2 ) has gained much attention due to its potential applications in nanoelectronics and advanced memory devices. However, its complex phase behavior under external stimuli, such as pressure and temperature, remains a subject of intense investigation. This study focuses on developing a machine learning-based interatomic potential (MLIP) that is trained with data from density-functional theory (DFT) calculations to simulate phase transitions and mechanical properties of HfO 2 . The developed MLIP predicts lattice parameters, equations of state, bulk and shear moduli, and elastic constants that closely align with DFT predictions for several phases and at various pressures. Once validated, the MLIP is used to investigate the phase transitions of ferroelectric HfO 2 (𝑃⁢𝑐⁢𝑎⁢2 1 ) under both isobaric and constant stress conditions at elevated temperatures ranging from 200 to 2500 K. We used several complementary methods, including local symmetry identification, radial distribution function, and x-ray diffraction characterization, to identify interesting phase transitions among several competitive hafnia phases predicted from our simulations. The suggested methods uniformly reveal that under pure deviatoric condition, the system favors a transition from the orthorhombic 𝑃⁢𝑐⁢𝑎⁢2 1 phase to a tetragonal (𝑃⁢4 2 /𝑛⁢𝑚⁢𝑐) phase, whereas a zero stress condition drives the system from the 𝑃⁢𝑐⁢𝑎⁢2 1 phase to another orthorhombic (𝑃⁢𝑏⁢𝑐⁢𝑛) phase. These findings provide crucial insights into stress and temperature-induced phase behavior of hafnia, guiding future experimental and theoretical studies for optimizing hafnia-based ferroelectric devices.

Ferroelectric HfO2↗
DOE OSTI2020

Combinatorial Study of MZO Emitters for CdTe-Based Solar Cells

Precise band alignment at the front interface of CdTe-based solar cells is necessary to reduce photoexcited charge carrier recombination and to enable higher energy conversion efficiencies. Magnesium zinc oxide is not only transparent but also offers the ability to tune the conduction band offset with CdTe at the front of the device stack. In this work, we describe reactive sputtering of Mg 1-x Zn x O using metal targets and its application in CdTe photovoltaics. Combinatorial libraries of Mg 1-x Zn x O were created to tune the conduction band alignment for the optimal performance of CdTe solar cells. Band gap variation of more than 0.4 eV is achieved across a 3-inch substrate. Kelvin probe measurements demonstrate variance of work function across the substrate. Device performance is optimized at band gaps of 3.5 eV for the CdTe device processing conditions employed in this study.

14 SOLAR ENERGY↗
DOE OSTI2022

Structure of the Core Postfusion Porcine Endogenous Retrovirus Fusion Protein

Retroviral elements from endogenous retroviruses have functions in mammalian physiology. The best-known examples are the envelope proteins that function in placenta development and immune suppression. Porcine endogenous retroviruses (PERVs) are an understudied class of endogenous retroviruses that infect cultured human cells, raising concern regarding porcine xenografts. The PERV envelope glycoprotein has also been proposed as a possible swine syncytin with a role in placental development. Despite the growing interest in PERVs, their envelope glycoproteins remain poorly characterized. Here, we successfully determined the postfusion crystal structure of the PERV core fusion ectodomain. The PERV fusion protein structure reveals a conserved class I viral fusion protein six-helix bundle. Biophysical experiments demonstrated that the thermodynamic stability of the PERV fusion protein secondary structure was the same at physiological and acidic pHs. A conserved surface analysis highlights the high degree of sequence conservation among retroviral fusogens in the chain reversal region that facilitates the large-scale conformational change required for membrane fusion. Further structural alignment of class I viral fusogens revealed a phylogenetic clustering that shows evolution into various lineages that correlate with virus mechanisms of cell entry. Our work indicates that structural dendrograms can be used to qualitatively infer insights into the fusion mechanisms of newly discovered class I viral fusogen structures.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Design and performance of a 35-ton liquid argon time projection chamber as a prototype for future very large detectors

Liquid argon time projection chamber technology is an attractive choice for large neutrino detectors, as it provides a high-resolution active target and it is expected to be scalable to very large masses. Consequently, it has been chosen as the technology for the first module of the DUNE far detector. However, the fiducial mass required for “far detectors” of the next generation of neutrino oscillation experiments far exceeds what has been demonstrated so far. Scaling to this larger mass, as well as the requirement for underground construction places a number of additional constraints on the design. A prototype 35-ton cryostat was built at Fermi National Acccelerator Laboratory to test the functionality of the components foreseen to be used in a very large far detector. The Phase I run, completed in early 2014, demonstrated that liquid argon could be maintained at sufficient purity in a membrane cryostat. A time projection chamber was installed for the Phase II run, which collected data in February and March of 2016. The Phase II run was a test of the modular anode plane assemblies with wrapped wires, cold readout electronics, and integrated photon detection systems. While the details of the design do not match exactly those chosen for the DUNE far detector, the 35-ton TPC prototype is a demonstration of the functionality of the basic components. Measurements are performed using the Phase II data to extract signal and noise characteristics and to align the detector components. A measurement of the electron lifetime is presented, and a novel technique for measuring a track's position based on pulse properties is described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Zam Is a Redox-Regulated Member of the RNB-Family Required for Optimal Photosynthesis in Cyanobacteria

The zam gene mediating resistance to acetazolamide in cyanobacteria was discovered thirty years ago during a drug tolerance screen. We use phylogenetics to show that Zam proteins are distributed across cyanobacteria and that they form their own unique clade of the ribonuclease II/R (RNB) family. Despite being RNB family members, multiple sequence alignments reveal that Zam proteins lack conservation and exhibit extreme degeneracy in the canonical active site—raising questions about their cellular function(s). Several known phenotypes arise from the deletion of zam, including drug resistance, slower growth, and altered pigmentation. Using room-temperature and low-temperature fluorescence and absorption spectroscopy, we show that deletion of zam results in decreased phycocyanin synthesis rates, altered PSI:PSII ratios, and an increase in coupling between the phycobilisome and PSII. Conserved cysteines within Zam are identified and assayed for function using in vitro and in vivo methods. We show that these cysteines are essential for Zam function, with mutation of either residue to serine causing phenotypes identical to the deletion of Zam. Redox regulation of Zam activity based on the reversible oxidation-reduction of a disulfide bond involving these cysteine residues could provide a mechanism to integrate the ‘central dogma’ with photosynthesis in cyanobacteria.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1980

Charging of a large object in low polar Earth orbit

The charging of a large sphere subject to the environment encountered by the shuttle orbiter as it passes through the auroral regions in its low polar Earth orbit was investigated. The environment consists of a low temperature dense plasma and a relatively intense (200 mu A/sq m) field aligned flux of energetic electrons (approximately 5 to 10 keV). The potential on a sphere in eclipse is presented as a function of the ratio kappa of the charging rate produced by precipitating electrons to the discharging rate produced by ram ions. It was found that a 5 meter conducting sphere charges to potentials of order 1 kilovolt for kappa approximately 2, even though a 0.5 meter sphere charges to less than 100 volts. It is concluded that the natural charging environment can induce large potentials (approximately 1 kilovolt) on the shuttle orbiter.

Parks, D. E.↗
NASA NTRS1983

Ray-tracing studies and path-integrated gains of ELF unducted whistler mode waves in the earth's magnetosphere

Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.

Huang, C. Y.↗
NASA NTRS1982

Magnetopause modeling - Flux transfer events and magnetosheath quasi-trapped distributions

Three-dimensional distribution functions for energetic ions are studied numerically in the magnetosphere, through the magnetopause, and in the magnetosheath using a simple one-dimensional quasi-static model and ISEE 1 magnetopause crossing data for November 10, 1977. Quasi-trapped populations in the magnetosheath observed near flux transfer events (FTEs) are investigated, and it is shown that the population in the sheath appears to sandwich the FTE distributions. These quasi-trapped distributions are due to slow, large pitch angle, outward moving particles left behind by the outward rush of the ions more field-aligned at the time the flux was opened. It is found that sheath convective flows can map along the connected flux tube without drastically changing the distribution function, and results suggest that localized tangential fields above the upper limit may exist.

Speiser, T. W.↗
NASA NTRS1982

Payload installation and deployment aid for space shuttle orbiter spacecraft remote manipulator system

An aid concept known as the PIDA (Payload Installation and Deployment Aid) is presented as a way to assist the Remote Manipulator System (RMS) by relaxing the accuracy required during payload handling in the payload bay. The aid concept was designed and developed to move payloads through a prescribed path between the confined quarters of the payload bay and a position outside the critical maneuvering area of the Orbiter. An androgynous docking mechanism is used at the payload/PIDA interfaces for normal docking functions that also serves as the structural connection between the payload and the Orbiter, that is capable of being loosened to prevent transfer of loads between a stowed payload and the PIDA structure. A gearmotor driven drum/cable system is used in the docking mechanism in a unique manner to center the attenuator assembly, align the ring and guide assembly (docking interface) in roll, pitch, and yaw, and rigidize the mechanism at a nominal position. A description of the design requirements and the modes of operation of the various functions of the deployment and the docking mechanisms are covered.

Ross, T. O.↗
DOE OSTI2022

Microstructural changes of proton irradiated Hastelloy-N and in situ micropillar compression testing of one single grain at different local damage levels

Here, in situ micropillar compression was used to study the deformation of proton-irradiated Hastelloy-N at different damage levels. Multiple pillars were prepared from a single domain along the cross-section of 2.5 MeV proton-irradiated Hastelloy-N. Depending on the location of micropillars, the critical resolved shear stress was obtained as a function of local damage levels. Such an approach eliminates the variation of yield stress due to the difference in the Schmid factor. Microstructural characterization showed that irradiation hardening is contributed by complicated defect structures, including (a) dislocation loops with many in corduroy-like alignments, (2) dislocations pile up, and (3) Cottrell atmosphere. Silicon atoms are found to segregate at dislocation lines and loops and form complicated Cottrell cloud patterns. The critical resolved shear stress, $t_{crss}$, and hardening exponents were both extracted as a function of displacements per atom values up to 2.3. There was a 60% increase in $t_{crss}$ at the highest damage level.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Role of Fluorine in Chemomechanics of Cation-Disordered Rocksalt Cathodes

The role of nanoscale chemomechanical behavior in the macroscopic performance of functional materials is well recognized. For lithium-ion battery cathodes, tremendous effort has been devoted to the development of new chemistry and structure, yet fundamental understanding of the correlation between redox processes and mechanical properties of the novel materials lags behind. In the present study, we prepare large discrete single grains of Li-excess cation-disordered rocksalts (DRX) and investigate their chemomechanical behavior at the particle level, using nanoresolution X-ray and electron-based spectro-imaging and chemical mapping techniques. While irregular cracking upon lithium extraction leads to the eventual breakdown of the baseline DRX oxide (Li 1.2 Ti 0.4 Mn 0.4 O 2 ) particles at a high delithiation state, the fluorinated-DRX (Li 1.3 Ti 0.3 Mn 0.4 O 1.7 F 0.3 ) clearly displays aligned cracking along the <001> direction. The resulting periodicity in the cracking pattern enables the particles to retain their integrity and, consequently, improved electrochemical stability. Density functional theory (DFT) calculations showed that fluorination leads to increased concentration of Li+ on the (001) planes and preferential Li movements along the <001>-family directions, revealing the underlying mechanism for directional cracking. Overall, our study demonstrates the unique role of fluorine in modulating nanoscale chemomechanics, which in turn influences the evolution of charge and strain heterogeneity at the particle level. These insights provide important design guidelines in further improving DRX cathode materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Targeted Adjusting Molecular Arrangement in Organic Solar Cells via a Universal Solid Additive

The incorporation of solid additive has been considered as an effective strategy for developing organic photovoltaics with multi-components, which is independent of dynamics, playing unique roles in morphology adjustment. However, their complex working mechanisms involving specific chemical structures are selective to material systems, hence limiting their university and flexibility in application. Herein, an inert small-molecular compound naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT) is introduced into the bulk-heterojunction blend as the solid additive, which can function with various material systems and solvents, depending on its simple π-conjugated structure and S⋯N interaction for adjusting molecular alignment. It is interesting to note that the introduced NT can not only improve device performance, but also simplify complicated pre- or post-processing methods, reduce impact from batch-to-batch differences, construct sufficient energy transfer channel as well as improve device stability. The resulting devices based on PTzBI-dF:Y6-BO system show an impressive power conversion efficiency of 17.4% with obviously enhanced T 80 lifetime of >1200 h. These findings provide useful guidelines for exploring potential universal solid additives benefitting toward commercial application.

36 MATERIALS SCIENCE↗