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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Conservative scattering of Reissner-Nordström black holes at third post-Minkowskian order

Using a recently developed effective field theory formalism for extreme mass ratios arXiv:2308.14832, we present a calculation of charged black hole scattering at third post-Minkowskian order. The charges and masses are kept arbitrary, and the result interpolates from the scattering of Schwarzschild to extremal charged black holes, and beyond to charged particles in electrodynamics — agreeing with previously reported results in all such limits. The computation of the radial action is neatly organized in powers of the mass ratio. The probe (0SF) contributions are readily computed by direct integration of the radial momentum, and we use the effective field theory to compute the subleading (1SF) contributions via background-field Feynman rules supplemented by an operator encoding recoil of the background. Together these contributions completely determine the conservative physics at order O (G 3 ). .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

One-loop central-emission vertex for two gluons in $\mathcal{N}$ = 4 super Yang-Mills theory

A necessary ingredient for extending the BFKL equation to next-to-next-to-leading logarithmic (NNLL) accuracy is the one-loop central emission vertex (CEV) for two gluons which are not strongly ordered in rapidity. Here we consider the one-loop six-gluon amplitude in $\mathcal{N}$ = 4 super Yang-Mills (SYM) theory in a central next-to-multi-Regge kinematic (NMRK) limit, we show that its dispersive part factorises in terms of the two-gluon CEV, and we use it to extract the one-loop two-gluon CEV for any helicity configuration within this theory. This is a component of the two-gluon CEV in QCD. Although computed in the NMRK limit, both the colour structure and the kinematic dependence of the two-gluon CEV capture much of the complexity of the six-gluon amplitudes in general kinematics. In fact, the transcendental functions of the latter can be conveniently written in terms of impact factors, trajectories, single-emission CEVs and a remainder, which is a function of the conformally invariant cross ratios which characterise the six-gluon amplitudes in planar $\mathcal{N}$ = 4 SYM. Finally, as expected, in the MRK limit the two-gluon CEV neatly factorises in terms of two single-emission CEVs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The convolutional double copy: a case study with a point

The double copy relates scattering amplitudes in gauge and gravity theories. It has also been extended to classical solutions, and a number of approaches have been developed for doing so. One of these involves expressing fields in a variety of (super-)gravity theories in terms of convolutions of gauge fields, including also BRST ghost degrees of freedom that map neatly to their corresponding counterparts in gravity. In this paper, we spell out how to use the convolutional double copy to map gauge and gravity solutions in the manifest Lorenz and de Donder gauges respectively. We then apply this to a particular example, namely the point charge in pure gauge theory. As well as clarifying how to use the convolutional approach, our results provide an alternative point of view on a recent discussion concerning whether point charges map to the Schwarzschild solution, or the more general two-parameter JNW solution, which includes a dilaton field. We confirm the latter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

The timbre of Hawking gravitons: an effective description of energy transport from holography

Planar black holes in AdS, which are holographically dual to compressible relativistic fluids, have a long-lived phonon mode that captures the physics of attenuated sound propagation and transports energy in the plasma. We describe the open effective field theory of this fluctuating phonon degree of freedom. The dynamics of the phonon is encoded in a single scalar field whose gravitational coupling has non-trivial spatial momentum dependence. This description fits neatly into the paradigm of classifying gravitational modes by their Markovianity index, depending on whether they are long-lived. The sound scalar is a non-Markovian field with index 3 - d for a d-dimensional fluid. We reproduce (and extend) the dispersion relation of the holographic sound mode to quartic order in derivatives, constructing in the process the effective field theory governing its attenuated dynamics and associated stochastic fluctuations. We also remark on the presence of additional spatially homogeneous zero modes in the gravitational problem, which remain disconnected from the phonon Goldstone mode.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Exploiting chitosan to improve the interface of nanocellulose reinforced polymer composites

Cellulose nanofibrils (CNFs) have been widely used as a nanofiller for polymer composite reinforcement due to their excellent mechanical properties. However, CNF is produced in water and needs to be dried prior to use in composite materials. The presence of hydroxyl groups on the surface of CNF creates strong hydrogen bonding that makes it difficult and costly to dry. Additionally, the hydrophilicity at the fiber surface results in agglomeration of CNFs within many polymer matrices. In this study, chitosan (CS) was co-precipitated with CNF to produce a dual-bonding filler for use in poly (lactic acid) (PLA) composites. CS promotes improved interfacial interaction within the polymer matrix by forming strong hydrogen bonds with the CNF and potential covalent bonds with the PLA. Finally, the results confirmed that the addition of a small amount of CS significantly improved the mechanical properties compared to PLA + CNF composites and neat PLA. The detailed study of the PLA + CNF/CS composites reveals the synergetic effect of the hydrogen and covalent bonding mechanism for PLA reinforcement.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Additively manufactured polymer composites for heat exchanger applications: evaluation of critical thermophysical properties

Polymeric heat exchangers (PHXs) have been used in applications involving weight restrictions, chemical compatibility, and fouling issues. Additive manufacturing (AM) or 3D printing provide new solutions to previously inaccessible combinations of properties and geometries. There are some advancements in the PHXs by AM; however, the process and the properties of materials still need further investigation to improve the overall performance. In this study, additively manufactured polyethylene terephthalate glycol (PETG) composites reinforced with graphite and pitch-based carbon fibers were evaluated for their potential application as PHXs. The thermal conductivity, volumetric heat capacity, coefficient of thermal expansion, creep behavior, and long-term performance were studied in detail. Our results reveal that the composites have an anisotropic thermal conductivity. The thermal conductivity along the printing direction is higher than the layer building direction due to the shear-induced alignment of the fillers. The printed composites achieve good thermal stability with 80% lower CTE at room temperature than neat PETG. Creep tests suggest the creep and creep recovery were highly temperature-dependent, and the deformation can be recovered when the temperature is below glass transition. These results suggest additive manufactured composites be potentially used for heat exchanger applications at low temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Roles of Solvent in the Catalytic Hydrogen Release from Liquid Organic Hydrogen Carriers: Chemical, Thermodynamical and Technological Aspects

A Liquid Organic Hydrogen Carrier (LOHC) enables the storage and transport of hydrogen at ambient pressures and temperatures in a safe and convenient form using current infrastructure. However, it is challenging to directly compare reactivity and selectivity for hydrogen release, especially when comparing the catalytic efficiencies of neat LOHCs to highly diluted LOHCs in different solvents, reaction conditions, and catalysts. This work evaluates the role of solvents in catalysis and quantifies the energy efficiency of the overall process. The presence of solvent dilutes the volumetric density of available hydrogen, but may be necessary to achieve optimal catalysts stability, reactivity, and product selectivity. With respect to the reaction conditions as determined by thermodynamics, solvents with higher vapor pressures than that of the carrier can cause the erroneous impression of a more favorable reaction equilibrium. Concerning energy efficiency, solvents can result in increased energy demand for hydrogen release as the inert solvent must be heated to reaction temperatures required for release of H 2 from the LOHC. Further, this work recommends that investigations of catalyst reactivity should be carried out at different ratios of solvent to LOHC to understand how the reactivity changes and what the implications are for maximizing energy density and catalyst stability and reactivity. Investigations should also consider how these implications will affect the technical needs of applications intended for the LOHC system. Based on the results of this study, it is advised to focus research activities on LOHC systems with a gravimetric solvent content below about 50% as the thermodynamic disadvantages become very pronounced beyond this threshold.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Post-process annealing of large-scale 3D printed polyphenylene sulfide composites

Large-scale extrusion-based additive manufacturing of high-performance thermoplastic composites like fiber reinforced polyphenylene sulfide (PPS) is well-suited for tooling applications to lower manufacturing costs and lead times. Autoclave tooling requires good mechanical performance at temperatures even above the glass transition temperature (T g ). In this work, the authors have investigated a post-process isothermal annealing technique to improve the mechanical properties of various grades of carbon fiber reinforced PPS components printed on the Big Area Additive Manufacturing (BAAM) system. Since PPS is a semi-crystalline polymer, crystallinity can change during annealing and affect the mechanical properties of the part. In addition, isothermal annealing can also lead to solid-state structural changes in the form of thermal and oxidative branching and/or crosslinking reactions in some grades of PPS which can alter the crystallization process. This work reports the effect of annealing on dynamic mechanical properties of BAAM printed components, along with studies to determine the effect of annealing on crystallinity and the occurrence of oxidative reactions. Results showed that isothermal annealing at 250 °C for 18 h improved the storage modulus of all selected grades (neat and reinforced) of PPS at temperatures above T g . Annealing led to an overall increase in the degree of crystallinity, with secondary crystallization taking place. Although oxidative structural changes were observed to occur more on the surface of the PPS parts, they primarily influenced the size of crystals formed and did not significantly alter the degree of crystallinity at various regions within the sample.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Characterizing material transitions in large-scale Additive Manufacturing

Integrating Multiple Materials (MM) into large-scale Additive Manufacturing (AM) is a key for various industrial applications wishing to incorporate site-specific properties into geometrically complex designs that are difficult to manufacture with traditional techniques. Printing with multiple materials is typically accomplished by using layers as natural material boundaries, but having the capability to switch between materials within a single layer without pausing would further expand MM possibilities. This study used Cincinnati Incorporated’s Big Area Additive Manufacturing (BAAM) system to explore material transitions with a novel dual-hopper that enables in-situ material blending of a pelletized feedstock. Constructing MM and functionally graded material (FGM) structures requires depositing a specific material composition at a specific geometric location to achieve a desired performance. Furthermore, accurately implementing this with the BAAM’s blended extrusion system requires a thorough understanding of the transition between distinct material compositions. This study characterizes a step-change transition between neat acrylonitrile butadiene styrene (ABS) and carbon fiber-reinforced ABS. Three distinct techniques were compared for analyzing the fiber content, and the transition zone between materials was characterized as a function of transition direction. The transition process was consistent to within 0.7 wt% carbon fiber variation between different layers and prints. The transition between materials was found to be directionally dependent, with ABS to CF/ABS having a transition length of 3.5 m compared to 3.2 m for CF/ABS to ABS. Furthermore, the transition from Material A to Material B was found to be repeatable with a possible variance in transition length of 0.3 m.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Large-scale additive manufacturing of self-heating molds

Large-scale material extrusion additive manufacturing technology is becoming the new mainstream technology for scaled-up composite mold and die applications. This paradigm shift in composite processing technology is primarily driven by out-of-autoclave tooling applications, in which fiber reinforced composite molds with scaled-up sizes and embedded heating elements are attractive. The present research describes the design, manufacturing, and testing of self-heating composite molds fabricated via a large-scale pellet extrusion 3D printing machine with an integrated wire co-extrusion tool. Polycarbonate (PC) composites reinforced with carbon fiber (PC/CF; 20 wt.%) and glass fiber (PC/GF; 20 wt.%) were used to fabricate mold parts. Joule heating thermal test results showed that uniform temperatures (~100 °C) were achieved for both PC/CF and PC/GF mold surfaces, using a custom-made feedback control power supply and infrared thermography. Mechanical characterizations, including tensile and flexural testing were performed on the wire-embedded and un-wired PC/CF and PC/GF base specimens to investigate the impact of the fiber reinforcement as well as the embedded wires. In the direction of extrusion, the ultimate tensile stress of PC/CF was 105 MPa, and that of PC/GF was 73 MPa, while the neat PC value was 64 MPa. Inner-bead voids and interfacial gaps were observed and characterized via optical and scanning electron microscopy. The embedded wires and inner bead impacted the mechanical properties of the composites. Furthermore, the stiffness of the wire-embedded mold was still satisfactory, proving that the technology can be used to fabricate additively manufactured out-of-oven/autoclave molds.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Microgrids 2025 editorial

We, the guest editors, thank everyone who has contributed to this virtual special issue (VSI), Microgrids 2025. This editorial includes a brief blurb for each accepted paper, collected in five loose areas. The topics represented do not settle neatly into categories, so we apologize in advance to any authors who find their work is not correctly represented. Within each section, the paper order reflects the sequence in which the manuscripts were submitted.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Surface-modified and oven-dried microfibrillated cellulose reinforced biocomposites: Cellulose network enabled high performance

Microfibrillated cellulose (MFC) is widely used as a reinforcement filler for biocomposites due to its unique properties. However, the challenge of drying MFC and the incompatibility between nanocellulose and polymer matrix still limits the mechanical performance of MFC-reinforced biocomposites. In this study, we used a water-based transesterification reaction to functionalize MFC and explored the capability of oven-dried MFC as a reinforcement filler for polylactic acid (PLA). Remarkably, this oven-dried, vinyl laurate–modified MFC improved the tensile strength by 38 % and Young’s modulus by 71 % compared with neat PLA. Our results suggested improved compatibility and dispersion of the fibrils in PLA after modification. This study demonstrated that scalable water-based surface modification and subsequent straightforward oven drying could be a facile method for effectively drying cellulose nanomaterials. We find that the method helps significantly disperse fibrils in polymers and enhances the mechanical properties of microfibrillar cellulose-reinforced biocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Encapsulation of highly viscous CO 2 capture solvents for enhanced capture kinetics: Modeling investigation of mass transfer mechanisms

The encapsulation of highly viscous liquid-like Nanoparticle Organic Hybrid Materials (NOHMs) inside a gas permeable polymer to form SIPs (Solvent Impregnated Polymers) significantly enhanced the CO 2 capture kinetics of NOHMs, leading to a remarkable 50-fold increase in CO 2 flux compared to the neat NOHMs. To understand the mechanism for enhanced CO 2 mass transfer within these hybrid materials, kinetic modeling of CO 2 uptake into SIPs containing polyethylenimine functionalized NOHMs, denoted NPEI-SIP, was conducted. CO 2 mass transfer into NPEI-SIP films was found to conform, both qualitatively and quantitatively, with a diffusion-controlled moving front model. The diffusion-controlled model was also used to simulate CO 2 uptake within a fixed bed containing polydisperse NPEI-SIP particles, and this model accurately predicted experimentally measured breakthrough curves at 25 °C and 50 °C. The 50-fold increase in gas flux was shown to be a consequence of the very large CO 2 permeability within the polymer–solvent composite. Furthermore, the increase in gas flux is also dependent on the diffusion–reaction regime in which the chemical solvent operates, and the largest improvement will occur when immobilizing solvents, such as NOHMs, which operate in the instantaneous-reaction regime. The CO 2 capacity (~3 mol CO 2 /kg) and saturation time (~5 min) of 430 μm SIP particles were comparable to popular CO 2 chemisorption materials such as amine grafted silicates, in spite of the slow kinetics of NOHM-I-PEI in liquid form (CO 2 saturation time ~24 h for a 1 mm thin film).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Local structure and Ca/Si ratio in C-S-H gels from hydration of blends of tricalcium silicate and silica fume

At the microscale, C-S-H gels from alite, or neat Portland cements, has a Ca/Si ratio close to 1.80. At the nanoscale, C-S-H is described by a defective tobermorite structure which allows a maximum Ca/Si ratio close to 1.40. There is no agreement in the location of the extra 0.40 mol of Ca(OH){sub 2} at the nanoscale. Atomistic modelling studies reported Ca(OH){sub 2} species within the tobermorite interlayer space. Other works point toward a fine intermixing of defective tobermorite and nanoportlandite. Here, we have prepared a series of alite blended with silica fume and studied the pastes by several techniques including synchrotron pair distribution function (PDF). In the employed conditions, the C-S-H gel formed by the pozzolanic reaction has nearly the same local structure than the primary C-S-H gel. Furthermore, differential PDF points toward Ca(OH){sub 2} excess having a local structure compatible with few-layer thick nanoparticles stretched along the c-axis.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of reactive MgO-modified calcium sulfoaluminate cements upon carbonation

This study characterizes reactive MgO-modified calcium sulfoaluminate (CSA) cement upon carbonation. Paste samples were fabricated by replacing CSA cement with reactive MgO at levels of 0, 5, 10, and 20 wt%. The samples were cured for 56 days and further cured at a CO{sub 2} concentration of 3% for 28 days. MgO incorporation into the CSA cement favored the formation of monosulfate over ettringite. Externally supplied MgO in the CSA cement reduced Al uptake in C-A-S-H and formed hydrotalcite as a secondary phase, which is associated with a reduction in the carbonation degree. In addition, the incorporated MgO inhibited the carbonation of ettringite and monosulfate, while more C-A-S-H and aluminum hydroxide were formed in neat CSA cement upon carbonation, showing the nearly full decomposition of ettringite and monosulfate. The tetrahedral Al network of the MgO-modified sample was not altered upon carbonation, indicating that MgO modified the route of carbonation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Molecular-Level Behavior of Imidazolium-Based Ionic Liquid Mixtures

Understanding the molecular-level organization of anions and cations in a mixture of different ionic liquids (ILs) is challenging, but it can be very important for designing solvents and IL-based membrane materials. In this work, we perform all-atom molecular dynamics (MD) simulations to understand the intermolecular interactions and structuring of both neat and mixed IL compositions containing 1-benzyl-3-methylimidazolium [ZMIM + ], 1-butyl-3-methylimidazolium [BMIM + ], bistriflimide [Tf 2 N – ], and tetrafluoroborate [BF 4 – ]. We observe very strong underlying molecular-level migrations in these mixtures, and this tends to mainly involve the anion species. As compared to the systems with a single anion, the mixed anions lead to large increases/decreases in the radial distribution function peak heights, whereas the cation mixing is relatively benign. The [BF 4 – ] anions have a strong tendency to displace the [Tf 2 N – ] anions in the mixtures, and this is seen with respect to both [BMIM + ] and [ZMIM + ].

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Probing air-water interfaces of dibutyl phosphoric acid (HDBP) aqueous solutions using vibrational sum frequency generation (vSFG) spectroscopy

Liquid-liquid extraction is a separation technique implemented in a wide variety of areas, achieving particular success in both the nuclear and biomedical fields. In this work, vibrational sum frequency generation spectroscopy (VSFG) and surface tension measurements were used to investigate the adsorption of dibutyl phosphate (DBP) at air-aqueous interfaces to simulate liquid-liquid systems relevant to the Plutonium Uranium Redox Extraction (PUREX) Process. The objective of this work is to establish qualitative relationships between changes in the bulk aqueous phase concentrations of DBP and its concentration and structure at air-liquid interface as probed with VSFG. Nitric acid concentration and solution ionic strength were varied to examine their effect on the interfacial DBP.. Introduction of DBP into neat water resulted in reduction of the VSFG spectral intensity in the dangling O-H region (3680 – 3800 cm -1 ) but large increase in the H-bonded O-H stretch frequency region (3000 – 3500 cm-1) and the appearance of the CH 3 symmetric stretch and CH 3 Fermi resonance peaks at ~ 2880 and 2945 cm -1 , respectively, indicating DBP at the air-water interface. The intensity of the C-H strecth peaks increased as DBP concentration increased from 0.24 to 32 mM, accompanied by a decreasing surface tension values. At fixed DBP concentration, the addition of either or both of HNO 3 and NaNO 3 to an ionic strength of 1 M or 3 M led to significant reduction of the O-H VSFG peaks and enhancement of the C-H peaks. The origins of these experimental observations are attributed to both the increased HDBP molecules partitioning and adsorption to the interface and the protonation of the interfacial DBP- molecules.

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

Autoignition study of iso -cetane/tetralin blends at low temperature

iso-Cetane and tetralin are the two fuel components commonly considered in literature diesel surrogates, and are hydrocarbon classes representative of iso-alkanes and naphthoaromatics, respectively. Since both surrogate components are involved in the key reactions controlling the autoignition reactivity of diesel surrogates, autoignition studies of iso-cetane, tetralin, and their blending behavior at low temperatures can be helpful in developing/refining chemical kinetic models of diesel surrogates, in order to better predict diesel ignition response under low temperature combustion conditions. In this investigation, autoignition experiments of iso-cetane, tetralin, and their binary mixtures at varying blending ratios have been conducted in a rapid compression machine (RCM) in the temperature/pressure range of 630–930 K and 10–20 bar. For the neat fuel components, the newly-acquired RCM data have been compared with the literature experimental results at some overlapping conditions. In addition, a chemical kinetic model describing the oxidation of iso-cetane and tetralin compiled/updated from the diesel surrogate model developed by Lawrence Livermore National Laboratory is used to simulate the experimental datasets. It is shown that this model exhibits good agreement with the experimental results of tetralin and also predicts the total ignition delay times of iso-cetane at lower temperatures reasonably well. However, the current model fails to fully capture the increase of total ignition delay time with increasing amount of tetralin in the binary blends observed in the present RCM experiments. Therefore, chemical kinetic analyses of the current model are conducted to help identify possible reasons leading to the discrepancies between simulations and experiments. Furthermore, the chemical kinetic interactions between iso-cetane and tetralin are explored by including additional cross-reactions among iso-cetane, tetralin, and their fuel fragments in the current model to assess their effects on model predictions. As a result, based on the chemical kinetic analysis results, future direction for model refinements is discussed.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗