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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Space station advanced automation

In the development of a safe, productive and maintainable space station, Automation and Robotics (A and R) has been identified as an enabling technology which will allow efficient operation at a reasonable cost. The Space Station Freedom's (SSF) systems are very complex, and interdependent. The usage of Advanced Automation (AA) will help restructure, and integrate system status so that station and ground personnel can operate more efficiently. To use AA technology for the augmentation of system management functions requires a development model which consists of well defined phases of: evaluation, development, integration, and maintenance. The evaluation phase will consider system management functions against traditional solutions, implementation techniques and requirements; the end result of this phase should be a well developed concept along with a feasibility analysis. In the development phase the AA system will be developed in accordance with a traditional Life Cycle Model (LCM) modified for Knowledge Based System (KBS) applications. A way by which both knowledge bases and reasoning techniques can be reused to control costs is explained. During the integration phase the KBS software must be integrated with conventional software, and verified and validated. The Verification and Validation (V and V) techniques applicable to these KBS are based on the ideas of consistency, minimal competency, and graph theory. The maintenance phase will be aided by having well designed and documented KBS software.

Woods, Donald↗
NASA NTRS2010

Asymptotic Linearity of Optimal Control Modification Adaptive Law with Analytical Stability Margins

Optimal control modification has been developed to improve robustness to model-reference adaptive control. For systems with linear matched uncertainty, optimal control modification adaptive law can be shown by a singular perturbation argument to possess an outer solution that exhibits a linear asymptotic property. Analytical expressions of phase and time delay margins for the outer solution can be obtained. Using the gradient projection operator, a free design parameter of the adaptive law can be selected to satisfy stability margins.

Nguyen, Nhan T.↗
NASA NTRS1987

Nonlinear diffusion in the solid phase

A Fourier series expansion method has been used to develop simple and relatively accurate solutions for nonlinear Fickian diffusion in the solid phase. For the fundamental harmonic, the first term in the Fourier expansion is qualitatively similar but quantitatively quite different from the conventional exponential function. In contrast, the Fourier coefficients of the higher order harmonics are combinations of fast-decay and slow-decay components. The simple analytical results agree well with numerical solutions for one sample calculation.

Tsang, Tung↗
DOE OSTI2023

Low and High LET Degradation Studies of Metal-Loaded Organic Phase Ligands in the ALSEP Process

Organic solutions comprising the Actinide Lanthanide Separation Process (ALSEP) solvent consisting of 0.5 M 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and 0.05 M N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide (T2EHDGA) in n-dodecane were subjected to low LET and high LET irradiation before and after equilibration with an aqueous phase of 3 M HNO 3 . Degradation dose constants revealed greater ligand degradation due to gamma irradiation than alpha irradiation for both ligands. Furthermore, equilibration with nitric acid did not have a significant impact on ligand degradation for either irradiation source. Identified degradation products were similar for both gamma and alpha irradiation and occurred mostly through the rupture of the N–C carbonyl and C–O ether bonds for T2EHDGA and the C–Oether bond in HEH[EHP]. Acid contact appears to alter the degradation pathway by favoring the formation of higher molecular weight recombination products. Furthermore, mixed T2EHDGA-HEH[EHP]-NO 3 complexes were formed with Nd(III) after extraction from 3 M HNO 3 , and low LET gamma irradiation of the Nd(III) loaded organic solution produced similar degradation products as the organic solution absent of Nd(III). Interestingly, and likely due to the greater radiolytic susceptibility of T2EHDGA than HEH[EHP], a HEH[EHP]-Nd(III) complex appears to form as the T2EHDGA degrades with increasing absorbed dose.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1986

Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts

Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

Su, Ching-Hua↗
DOE OSTI2019

Reel-to-Reel Heat Treatment, Microstructure, and Superconducting Properties of Jelly-Roll Nb{sub 3}Al Superconducting Wire

In this work, we utilized the jelly-roll method to make a single-filament Nb{sub 3}Al precursor long wire, combining with a homemade reel-to-reel rapid heating and quenching (RHQ) equipment, and consequently the high-performance Nb{sub 3}Al superconducting wires had been prepared. By investigating the heating current and wire moving speed, the optimized RHQ heat treatment conditions of this Nb{sub 3}Al wire were obtained. The results suggest that the T{sub c} for the Nb{sub 3}Al superconducting wire is up to 17.4 K and the non-Cu critical current density (non-Cu J{sub c}) reaches 1238 A/mm{sup 2} at 4.2 K and 12 T, which indicates the bcc-phase Nb–Al supersaturated solid solution has already been generated. Considering the Nb{sub 3}Al precursor wire with a large thickness of Al layer, about 690 nm, such high J{sub c} is quite unexpected. The SEM analysis presents that there is still some unreacted Nb and Nb{sub 2}Al phase in the superconducting wire, which may result from the inhomogeneity of Nb and Al foils. This work implies the Nb{sub 3}Al superconducting wire is promising to the application of high-field superconducting magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Understanding the TiH (2-x) /TiO y System at Elevated Temperature: A Literature Review

Titanium hydride of varying TiH stoichiometry is used in pyrotechnic compositions. In order to yield consistent performance, manufacturing processes must be developed to ensure precise and reproducible material properties, including composition and morphology. Legacy synthesis protocols are not comprehensive nor are the required apparatuses still available. To guide the development of novel production procedures, this report reviews literature on relevant chemical reactions and diffusion events occurring at elevated temperature in the TiH (2-x) /TiO y system. Titanium hydride exposed to air spontaneously forms a passivating oxide layer. Upon heating, significant hydrogen release, which is accompanied by changes to the surface oxide layer, is noted by 375–400°C. At higher temperatures (above about 500°C) the oxide layer is reported to be essentially nonexistent as a result of oxide-layer dissolution processes and, potentially, oxide-layer reduction due to water formation. Based on the reviewed literature, we hypothesize that, by 500°C, the surface layer consists of an oxyhydride phase, which is a solid solution of oxygen in titanium hydride. We believe that hydrogen release from titanium hydride is controlled by the kinetics of molecular hydrogen desorption on the oxyhydride surface. No literature data is available for corresponding activation energies of the dynamic desorption process, and the equilibrium phase diagram of this three-component system remains largely unexplored as well. These gaps in knowledge might be addressed through coordinated computational modeling and experimental efforts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Preparation and Characterization of New Environmental Functional Polymers Based on Vanillin and N-isopropylacrylamide for Post Polymerization

The study aims to synthetize a new functional acrylate monomer from vanillin in one step reaction. The new monomer has called by vanillin acrylate and abbreviated (VA). It was confirmed by chemical methods 1H NMR, 13C, IR and UV indicated logic results. The homopolymer has been prepared by free radical polymerization and characterized chemically and physically, the {sup 1}HNMR and IR have proofed the presence of aldehyde group in the polymer main chain. This monomer was used to synthesize three different molar concentrations of temperature responsive functional polymers with N-isopropylacrylamide via free radical polymerization by AIBN in solution. The {sup 1}H NMR was used for determination of actual mole concentration of each monomer. The aldehyde group in polymers were used as a linker for grafting with primary amine compounds by click reactions to form Schiff’s base imine compounds. The grafted copolymers were also investigated by 1H NMR and IR for structure elucidation. Gel permeation chromatography GPC was used for determination the molecular weight and polydispersity; DSC for glass temperature of solid polymers; XRD for crystallinity. UV–Vis Spectroscopy was used for the determination of phase separation or the lower critical solution temperature (Tc) of polymers solution before and after grafting, not only in deionized water but in pH 5 and pH 11. Graphical Abstract: Synthesis of new functional monomer based on vanillin in one step reaction. Monomer has been successfully polymerized by free radical polymerization using AIBN as initiator. Three different mole ratios (10, 15, 20 mol%) of copolymer with NIPAAm were prepared. All monomers and polymers have been chemically elucidated. The aldehyde functional group used as linker for primary amine compounds, the final products have been characteristics as T, pH dual responsive polymers the phase transition temperature of copolymer before and after grafting was determined by UV.vis Spectroscopy. .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Wear Behavior of Vanadium and V-Ti-Ta Alloys under Reciprocating Sliding Conditions

Vanadium and newly developed V-Ti-Ta alloys have been systematically investigated for wear characteristics using ball-on-flat reciprocative sliding experiments. These materials have been tested at different sliding conditions (load and frequency) against hardened steel (AFBMA Grade 10) ball as counter-body. Coefficient of friction, wear volume and specific wear rate were measured and evaluated. Friction coefficient of vanadium and its alloys increases with increase in applied load irrespective of sliding frequencies. Wear rate decreases with increase in alloying content. Among the investigated compositions, V-4Ti-7Ta alloy exhibited superior wear performance having a least wear rate of 3.06 × 10{sup −6} mm{sup 3}/Nm, which is three times lower as compared with unalloyed vanadium when tested at 5 N and 5 Hz conditions. Addition of Ti and Ta strengthens the vanadium matrix by solid solution and contributes to enhanced wear resistance of the material without affecting the friction coefficient values. The major phases identified in the wear track regions were V{sub 2}O{sub 5} and Fe{sub 0.11}V{sub 2}O{sub 5.15}. Microstructural investigation reveals the predominant presence of adhesive wear regions at higher loads (15 N).

36 MATERIALS SCIENCE↗
NASA NTRS1992

Failure of the method of slowly varying amplitude and phase for non-linear, singular oscillators

It is shown that the method of slowly varying amplitude and phase yields erroneous results in the study of the mathematical properties of nonlinear singular oscillator systems. The analytical solution is described in which the phase function is constant and for which a special limiting behavior exists when the wavelength is zero. The previous method based on the condition of boundedness cannot be satisfied for nonlinear singular characteristics, and the erroneous designation of the expansion parameter is identified.

Mickens, R. E.↗
DOE OSTI2018

Changes in Interfacial Tension with Time in Two-Liquid-Phase Systems

Interfacial tension (IFT) is a thermodynamic property of the interface between two immiscible fluids. This property has been identified as an important factor in an advanced solvent extraction system because it correlates with settling time and miscibility. The IFT in a variety of two phase systems has been partially characterized by Los Alamos National Laboratory (LANL) scientists. Information about the change in IFT is gathered in this study to more fully characterize these two-phase systems. Metal loaded aqueous solutions are of particular interest, as they simulate a solvent extraction system. Based in part on this body of research, LANL scientists will select the appropriate organic solvent and aqueous pH to develop an advanced solvent extraction system which will remove heavy metals from acidic solutions. Previous studies show that the factor which has the greatest effect on discrete IFT measurements is the ratio of aqueous density to organic density1. It is expected that this density ratio will play an important role in time-dependent IFT measurements as well. The two phases will be brought into equilibrium before beginning the tests, so it is also expected that IFT will not drastically change over a two hour time period.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1979

Development of SiAlON materials

Cold pressing and sintering techniques were used to produce ceramic test specimens in which the major phase was either Si3N4 or a solid solution having the beta Si3N4 structure. Additional components were incorporated to promote liquid phase sintering. Glass and/or crystalline phase were consequently retained in boundaries between Si3N4 grains which largely determined the physical properties of the bodies. Systems investigated most extensively included R-Si-Al-O-N (R = rare earth element) Zr-Si-Al-O-N, Y-Si-Be-O-N, and R1-R2-Si-O-N. Room temperature and 1370 C modulus of ruptured, 1370 C creep, and oxidation behavior are discussed in terms of phase relationships in a parent quinery, and relavent oxide systems.

Layden, G. K.↗
DOE OSTI2025

Evaluation of Density-Functional Tight-Binding Methods for Simulation of Protic Molecular Ion Pairs

In this work, we benchmark the accuracy of the density-functional tight-binding (DFTB) method, namely the long-range corrected second-order (LC-DFTB2) and third-order (DFTB3) models, for predicting energetics of imidazolium-based ionic liquid (IL) ion pairs. We compare the DFTB models against popular density functionals such as LC-ωPBE and B3LYP, using ab initio domain-based local pair-natural orbital coupled cluster (DLPNO-CC) energies as reference. Calculations were carried out in the gas phase, as well as in aqueous solution using implicit solvent methods. We find that the LC-DFTB2 model shows excellent performance in the gas phase and agrees well with reference energies in implicit solvent, often outperforming DFTB3 predictions for complexation energetics. Our study identifies a range of opportunities for use of the LC-DFTB method and quantifies its sensitivity to protonation states and the types of chemical interactions between ion pairs.

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

Colliding-Droplet Microreactor: Rapid On-Demand Inertial Mixing and Metal-Catalyzed Aqueous Phase Oxidation Processes

In-depth investigations of the kinetics of aqueous chemistry occurring in microdroplet environments require experimental techniques that allow a reaction to be initiated at a well-defined point in time and space. Merging microdroplets of different reactants is one such approach. The mixing dynamics of unconfined (airborne) microdroplets have yet to be studied in detail, which is an essential step toward widespread use and application of merged droplet microreactors for monitoring chemical reactions. Here, we present an on-demand experimental approach for initiating chemical reactions in and characterizing the mixing dynamics of colliding airborne microdroplets (40 ± 5 μm diameter) using a streak-based fluorescence microscopy technique. The advantages of this approach include the ability to generate two well-controlled monodisperse microdroplet streams and collide (and thus mix) the microdroplets with high spatial and temporal control while consuming small amounts of sample (<0.1 μL/s). Mixing times are influenced not only by the velocity at which microdroplets collide but also the geometry of the collision (i.e., head-on vs off-center collision). For head-on collisions, we achieve submillisecond mixing times ranging from ~900 μs at a collision velocity of 0.1 m/s to <200 μs at ~6 m/s. For low-velocity (<1 m/s) off-center collisions, mixing times were consistent with the head-on cases. For high-velocity (i.e., > 1 m/s) off-center collisions, mixing times increased by as much as a factor of 6 (e.g., at ~6 m/s, mixing times increased from <200 μs for head-on collisions to ~1200 μs for highly off-center collisions). At collision velocities >7 m/s, droplet separation and fragmentation occurred, resulting in incomplete mixing. These results suggest a limited range of collision velocities over which complete and rapid mixing can be achieved when using airborne merged microdroplets to, e.g., study reaction kinetics when reaction times are short relative to typical bulk reactor mixing times. We benchmark our reactor using an aqueous-phase oxidation reaction: iron-catalyzed hydroxyl radical production from hydrogen peroxide (Fenton's reaction) and subsequent aqueous-phase oxidation of organic species in solution. In conclusion, kinetic simulations of our measurements show that quantitative agreement can be obtained using known bulk-phase kinetics for bimolecular reactions in our colliding-droplet microreactor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Improving Data Center Energy Efficiency Through End-to-End Cooling Modeling and Optimization. Final Report

This report summarizes the development and demonstration of the three features developed for the DOE project “Improving Data Center Energy Efficiency through End-to-End Cooling Modeling and Optimization” (Award No. DE-EE0007688). The development of the three software features, Feature 1: Optimization of Cooling System Operation, Feature 2: Optimization of Airflow Management System, and Feature 3: Simultaneous Optimization of Airflow Management and Cooling Systems, are described first. Feature 1 is implemented in Phase 1 of the project and demonstrates 15% energy savings from cooling system optimization by applying the proposed retrofit solutions. Feature 2 is implemented in Phase 2 and the assessments show cooling energy-saving potential between 19.3% and 54.0%, depending on the energy-saving measures employed. In addition, investigating the energy saving potential for a hypothetical simple data center shows about 6.8% energy savings by optimizing the server load placement. Feature 3 is implemented in Phase 3 and the results show energy savings of 53.4% and 74.6% for the two partner data centers, respectively, compared to the baselines defined in Phase 1. Lastly, the project outcomes including software releases and publications are discussed.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Ultrafast photochemistry of gas-phase transition metal carbonyls

Organometallic photochemistry lies at the heart of photochemical energy conversions in applications such as photocatalysis, photovoltaic cells, and luminescent materials. Thus, understanding how metal and ligand interactions in organometallic complexes modify electronic excited-state properties and reactivity has been the subject of intense studies for decades. Transition metal carbonyls [M n (CO) m ] have long served as prototypical organometallic complexes for understanding metal–ligand bonding and photochemistry and have been studied extensively in solution, matrices, and the gas phase on time scales ranging from femtoseconds to microseconds and longer. This review chronicles the past two and a half decades of efforts in understanding the ultrafast (sub-nanosecond) dynamics of transition metal carbonyls in the gas phase, where complicating solvent influences are absent and multiple experimental probes and high-level electronic structure theory can come together to yield rich information on the intricate interplay of electronic and structural dynamics. This review first lays the groundwork by briefly describing the electronic structure of transition metal carbonyls and introducing the various ultrafast techniques that have been applied to study their unimolecular dynamics. We then provide a detailed historical account on the ultrafast photochemistry of iron pentacarbonyl, nickel tetracarbonyl, and transition metal hexacarbonyls and decacarbonyls, putting the more recent ultrafast studies in the context of prior investigations. In conclusion, we end this review with an outlook on open questions and future possibilities.

Core level spectroscopy↗
DOE OSTI2023

High‐Throughput Evaluation of Hardening Coefficients of Eight Alloying Elements in Magnesium

Liquid–solid diffusion couples (LSDCs) are employed to generate a composition gradient in the single‐phase hexagonal closed‐packed (hcp) solid solution with compositions up to the solubility limit of various solutes in Mg. Nanoindentation scanning across the composition gradient in LSDCs allows effective evaluation of composition‐dependent hardness of eight alloying elements (Al, Ca, Ce, Gd, Li, Sn, Y, and Zn) in the hcp Mg phase. The hardening coefficients, an indicator of the potency of solid‐solution hardening, are evaluated from the measured composition‐hardness data and correlated with various materials properties such as atomic radius, shear modulus, and elastic modulus of the solutes. The rank of hardening potency of Al, Gd, Sn, Y, and Zn measured by nanoindentation is in good agreement with that measured by microindentation reported in the literature. The hardening coefficient (potency) from the strongest to the weakest is Ce > Ca > Y ≈ Gd > Zn > Al ≈ Sn > Li in Mg‐based hcp binary solid solutions. The hardening coefficient is found to be closely correlated with the strengthening potency.

36 MATERIALS SCIENCE↗