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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Adhesion in thermomechanically processed seaweed-lignocellulosic composite materials

The increasing concerns associated with petroleum-derived polymers motivate the development of sustainable, renewably sourced alternatives. In ubiquitous applications such as structural materials for infrastructure, the built environment as well as packaging, where natural materials such as wood are used, we rely on nonrenewable and nondegradable polymers to serve as adhesives. In wood panels, such as medium density fiberboards (MDFs), formaldehyde-based resins are predominantly used to bond wood fibers and to provide strength to the materials. To further mitigate the environmental impact of construction materials, more sustainable adhesives need to be investigated. Here, in this article, we introduce Ulva seaweed as an adhesive to enable cohesion and strength in hot-pressed wood panels. Upon hot-pressing, powdered Ulva flows in between the wood particles, generating a matrix, which provides strong binding. We show that the flexural strength of Ulva-bonded wood biocomposites increases with increasing Ulva concentrations. At an Ulva concentration of 40 wt%, our composites reach an average elastic modulus of 6.1 GPa, and flexural strength of 38.2 MPa (compared to 4.7 GPa and 22.6 MPa, respectively, for pure wood compressed at the same pressing conditions). To highlight the bonding mechanisms, we performed infrared and x-ray photoelectron spectroscopy and identified indications of fatty acid mobility during hot-pressing. In addition, we demonstrate that the presence of Ulva improves other properties of the composites such as water resistance and fame retardancy. Ulva is also shown to behave as an excellent adhesive agent between two prepressed beams. Finally, we perform an in-depth analysis of the environmental impact of wood-Ulva biocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2021

ASME Code Rules and ASTM Standards Integration for Ceramic Composite Core Materials and Components 1

Fiber-reinforced ceramic matrix composites have many desirable properties for high-temperature nuclear applications, including excellent thermal and mechanical properties and reasonable to outstanding radiation resistance. Over the last 20 years, the use of ceramic composite materials has already expanded in many commercial nonnuclear industries as fabrication and application technologies mature. The new ASME design and construction rules under Section III, Subsection HH, Subpart B lay out the requirements and criteria for materials, design, machining and installation, inspection, examination, testing, and the marking procedure for ceramic composite core components, which is similar to the established graphite code under Section III, Subsection HH, Subpart A. Moreover, the general requirements listed in Section III, Subsection HA, Subpart B are also expanded to include ceramic composite materials. The code rules rely heavily on the development and publication of standards for composite specification, classification, and testing of mechanical, thermal, and other properties. These test methods are developed in the American Society for Testing and Materials Committee C28 on Advanced Ceramics with a current focus on ceramic composite tubes. Details of the composites code, design methodology, and similarities to the graphite code, as well as guidance for the development of specifications for ceramic composites for nuclear application and recent standard developments, are discussed. The next step is to "close the gap" to support licensing aspects by validating the code with benchmarking data.

Geringer, Josina↗
DOE OSTI2024

Multi-coat polymer photonic crystal films

Polymer composite photonic crystal materials are disclosed as coatings and topcoats which have high reflection (>30%) in a specific range of the electromagnetic spectrum, such as ultraviolet (<400 nm), visible (Vis, 400 nm-700 nm), or near-infrared radiation range (NIR, 700-2000 nm), and relatively low reflection (<20% reflection) in a second, different range of the electromagnetic spectrum. Surprisingly, it was found that through a formulation and additives approach, the optical properties of polymer composite photonic crystal films can be selectively modified from a variety of different coating methods, including spray deposition.

Pearson, Ryan Michael↗
DOE OSTI2020

Imprecise global sensitivity analysis using bayesian multimodel inference and importance sampling

Global Sensitivity Analysis (GSA) aims to understand the relative importance of uncertain input variables to model response. Conventional GSA involves calculating sensitivity (Sobol’) indices for a model with known model parameter distributions. However, model parameters are affected by aleatory and epistemic uncertainty, with the latter often caused by lack of data. In this paper, we propose a new framework to quantify uncertainty in probability model-form and model parameters resulting from small datasets and integrate these uncertainties into Sobol’ index estimates. First, the process establishes, through Bayesian multimodel inference, a set of candidate probability models and their associated probabilities. Imprecise Sobol’ indices are calculated from these probability models using an importance sampling reweighting approach. This results in probabilistic Sobol’ indices, whose distribution characterizes uncertainty in the sensitivity resulting from small dataset size. The imprecise Sobol’ indices thus provide a measure of confidence in the sensitivity estimate and, moreover, can be used to inform data collection efforts targeted to minimize the impact of uncertainties. Through an example studying the parameters of a Timoshenko beam, we show that these probabilistic Sobol’ indices converge to the true/deterministic Sobol’ indices as the dataset size increases and hence, distribution-form uncertainty reduces. The approach is then applied to assess the sensitivity of the out-of-plane properties of an E-glass fiber composite material to its constituent properties. This second example illustrates the approach for an important class of materials with wide-ranging applications when data may be lacking for some input parameters.

42 ENGINEERING↗
DOE OSTI2024

Tuning the Spin Transition and Carrier Type in Rare-Earth Cobaltates via Compositional Complexity

There is growing interest in material candidates with properties that can be engineered beyond traditional design limits. Compositionally complex oxides (CCO), often called high entropy oxides, are excellent candidates, wherein a lattice site shares more than four cations, forming single-phase solid solutions with unique properties. However, the nature of compositional complexity in dictating properties remains unclear, with characteristics that are difficult to calculate from first principles. Here, in this study, compositional complexity is demonstrated as a tunable parameter in a spin-transition oxide semiconductor La 1- x (Nd, Sm, Gd, Y) x/4 CoO 3 , by varying the population x of rare earth cations over 0.00≤ x≤ 0.80. Across the series, increasing complexity is revealed to systematically improve crystallinity, increase the amount of electron versus hole carriers, and tune the spin transition temperature and on-off ratio. At high a population (x = 0.8), Seebeck measurements indicate a crossover from hole-majority to electron-majority conduction without the introduction of conventional electron donors, and tunable complexity is proposed as new method to dope semiconductors. First principles calculations combined with angle resolved photoemission reveal an unconventional doping mechanism of lattice distortions leading to asymmetric hole localization over electrons. Thus, tunable complexity is demonstrated as a facile knob to improve crystallinity, tune electronic transitions, and to dope semiconductors beyond traditional means.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Advanced Methodology and Preliminary Measurements of Molecular and Mechanical Properties of Heart Valves under Dynamic Strain

Mammalian heart valves are soft tissue assemblies with multi-scale material properties. This is because they are constructs comprising both muscle and non-contractile extracellular matrix proteins (such as collagens and proteoglycans) and transition regions where one form of tissue structure becomes another, significantly different form. The leaflets of the mitral and tricuspid valves are connected to chordae tendinae which, in turn, bind through papillary muscles to the cardiac wall of the ventricle. The transition regions between these tissue subsets are complex and diffuse. Their material composition and mechanical properties have not been previously described with both micro and nanoscopic data recorded simultaneously, as reported here. Annotating the mechanical characteristics of these tissue transitions will be of great value in developing novel implants, improving the state of the surgical simulators and advancing robot-assisted surgery. We present here developments in multi-scale methodology that produce data that can relate mechanical properties to molecular structure using scanning X-ray diffraction. We correlate these data to corresponding tissue level (macro and microscopic) stress and strain, with particular emphasis on the transition regions and present analyses to indicate points of possible failure in these tissues.

valve failure↗
DOE OSTI2022

Characterizing Electron Flow through Catechol‐Graphene Composite Hydrogels

Abstract Electronic materials that allow the controlled flow of electrons in aqueous media are required for emerging applications that require biocompatibility, safety, and/or sustainability. Here, a composite hydrogel film composed of graphene and catechol is electrofabricated, and that this composite offers synergistic properties is reported. Graphene confers metal‐like conductivity and enables charge‐storage through an electrical double layer mechanism. Catechol confers redox‐activity and enables charge‐storage through a redox mechanism. Importantly, there are two functional populations of catechols: conducting‐catechols (presumably in intimate contact with graphene) allow direct electron‐transfer; and non‐conducting‐catechols (presumably physically separated from graphene) require diffusible mediators to enable electron‐transfer. Using a variety of spectroelectrochemical measurements, that the capacity of the composite for charge‐storage increases in proportion to the extent by which the catechol‐groups can undergo redox‐state switching is demonstrated. To illustrate the broad relevance of this work, how the redox‐state switching can be related to both the charge storage of energy materials and the memory of molecular electronic materials is discussed. The authors believe this work is significant because it demonstrates that: conducting and redox‐active components enable distinctly different mechanisms for charge‐storage and electron‐transfer; these components act synergistically; and mediators provide unique opportunities to extend the capabilities of electronic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Impacts of A‐Site Composition on the Cation Dissolution‐Mediated Surface Restructuring of Layered Nickelate Oxide Electrocatalysts During Alkaline Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a key anodic counter‐reaction for electrochemical production of fuels and chemicals. It is hindered by sluggish four‐electron transfer kinetics requiring highly oxidative operating potentials to achieve commercially relevant rates. NiFeO x H y electrocatalysts are among the most promising for OER in alkaline electrolytes. The Ni(OH) 2 /NiOOH redox couple has been reported as the active phase in Ni‐based electrocatalysts; however, its activity is often hindered by deactivation arising from the formation of OER‐inactive insulating species. Limited strategies exist for mitigating this deactivation. This study aims to address this by interrogating the evolution of OER active sites as a function of precatalyst composition and structural properties using a series of layered, crystalline Ni‐based Ruddlesden–Popper (RP) oxides (A 2 NiO 4+δ ). In situ evolution of the active NiO x H y surface is probed through Ni‐site OER turnover frequency analysis, and electrochemical impedance spectroscopy coupled with scanning transmission electron microscopy. We show that the stability of layered nickelate oxide electrocatalysts is governed by the dynamic competition between cation dissolution and Ni‐site reversibility, which can be tuned through the A‐site composition of RP oxides. These findings yield insights toward engineering OER oxide precatalysts that optimize the stability of in situ‐generated OER active phases.

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

Local halide heterogeneity drives surface wrinkling in mixed-halide wide-bandgap perovskites

Compositional heterogeneity in wide-bandgap (1.8 - 2.1 eV) mixed-halide perovskites is a key bottleneck in the processing of high-quality solution-processed thin films and prevents their application in efficient multijunction solar cells. Notably, mixed-cation (formamidinium-methylammonium) wide-bandgap perovskite films are prone to form micrometer-scale wrinkles which can interfere with the smooth surfaces ideal for multijunction devices. Here, we study the formation dynamics of wrinkled mixed-halide perovskite films and its impact on the local composition and optoelectronic properties. We use in situ X-ray scattering during perovskite film formation to show that crystallization of bromide-rich perovskites precedes that of mixed-halide phases in wrinkled films cast using an antisolvent-based process. Using nanoscopic X­-ray fluorescence and hyperspectral photoluminescence imaging, we also demonstrate the formation of iodide- and bromide-rich phases in the wrinkled domains. This intrinsic spatial halide segregation results in an increased local bandgap variation and Urbach energy. Morphological disorder and compositional heterogeneity also aggravate the formation of sub-bandgap electronic defects, reducing photostability and accelerating light-induced segregation of iodide and bromide ions in thin films and solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electronic transport in copper–graphene composites

In this work, we investigate electronic transport properties of copper–graphene (Cu–G) composites using a density-functional theory (DFT) framework. Conduction in composites is studied by varying the interfacial distance of copper/graphene/copper (Cu/G/Cu) interface models. Electronic conductivity of the models computed using the Kubo–Greenwood formula shows that the conductivity increases with decreasing Cu–G distance and saturates below a threshold Cu–G distance. The DFT-based Bader charge analysis indicates increasing charge transfer between Cu atoms at the interfacial layers and the graphene with decreasing Cu–G distance. The electronic density of states reveals increasing contributions from both copper and carbon atoms near the Fermi level with decreasing Cu–G interfacial distance. By computing the space-projected conductivity of the Cu/G/Cu models, we show that the graphene forms a bridge to the electronic conduction at small Cu–G distances, thereby enhancing the conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Characterizing Copper-Graphene Composites (Abstract)

In this project, Pacific Northwest National Laboratory (PNNL) will measure the electrical and mechanical properties of the metal composite samples provided by MetalKraft Technologies, LLC. PNNL will also use multimodal methods for characterizing the microstructure of MetalKraft Technologies, LLC’s copper graphene composites. PNNL will work with MetalKraft Technologies, LLC as part of the CABLE Manufacturing Prize efforts under a CRADA. The voucher from DOE has a budget of $100,000 over a period of 6 months. PNNL will be the primary place of performance for the property and microstructure characterization efforts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photochemical reactions on aerosols at West Antarctica: A molecular case-study of nitrate formation among sea salt aerosols

Environmental implications of climate change are complex and exhibit regional variations both within and between the polar regions. The increase of solar UV radiation flux over Antarctica due to stratospheric ozone depletion creates the optimal conditions for photochemical reactions on the snow. Modeling, laboratory, and indirect field studies suggest that snowpack process release gases to the atmosphere that can react on sea salt particles in remote regions such as Antarctica, modifying aerosol composition and physical properties of aerosols. Here, we present evidence of photochemical processing in West Antarctica aerosols using microscopic and chemical speciation of individual atmospheric particles. Individual aerosol particles collected at the Brazilian module Criosfera 1 were analyzed by scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) combined with computer controlled scanning electron microscopy (CCSEM) with energy-dispersive X-ray (EDX) microanalysis. The displacement of chlorine relative to sodium was observed over most of the sea salt particles. Particles with a chemical composition consistent with NaCl-NO3 contributed up to 30% of atmospheric particles investigated. Overall, this study provides evidence that the snowpack and particulate nitrate photolysis should be considered in dynamic partition equilibrium in the troposphere. Finally, these findings may assist in reducing modeling uncertainties and present new insights into the aerosol chemical composition in the polar environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Machine learning-enabled prediction of chemical durability of A 2 B 2 O 7 pyrochlore and fluorite

Pyrochlore-structure type and its derivative in a general formula A 2 B 2 O 7 (A = rare earth elements and actinides; B = Ti, Sn, Zr, Hf, Pb, Si, etc.) display excellent structural flexibility and rich crystal chemistry as promising nuclear waste form materials capable of immobilizing actinides and fission products. It is essential to understand these materials’ chemical durability and element release of radionuclides in order to evaluate their performance in near-field environment. However, it is a formidable grand technological challenge to experimentally perform durability testing across hundreds of thousands of possibilities resulting from their extreme compositional complexities due to cation substitutions at both A and B-sites. In this work, we demonstrate a machine learning approach to determine the key materials parameters and structural characteristics governing the leaching behaviors from a small set of selected compositions as model systems, enabling a science-based prediction of their chemical durability that can be extended to a wide range of chemical compositions. The combination of four key structural characteristics and materials parameters, including ionic radius size difference , ionic potential difference , electronegativity difference , and lattice parameter , creates features an optimized prediction of the chemical durability. Two machine learning models, linear regression and Kernel ridge regression models, are trained on the randomly-split training dataset derived from the experimentally-determined elemental release rates, and subsequently tested on the testing dataset. The predicted leaching rates from both machine learning models show an excellent agreement with the experimental data, demonstrating the feasibility of rapidly evaluating the material properties of new compositions. These results highlight the immense potential of synergizing informatics through machine learning-based models and well-controlled experiments of selected model systems to accelerate materials design and discovery with optimized compositions and performance of promising materials for effective nuclear waste management.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

A single-ion-conducting polymer and high-entropy Li-garnet composite electrolyte with simultaneous enhancement in ion transport and mechanical properties

Enabling the lithium metal anode has been the holy grail for improving the energy density for the next generation advanced batteries. Developing electrolytes that will suppress Li dendrite growth and provide sufficient ionic conductivity remains a major challenge in this field. In this study, we develop a polymer–ceramic composite electrolyte for lithium metal batteries. The polymer matrix is a vinyl ethylene carbonate (VEC) based single-ion-conducting polymer electrolyte. The ceramic filler is a Li 7 La 3 Zr 0.5 Nb 0.5 Ta 0.5 Hf 0.5 O 12 high-entropy Li-garnet (HE Li-garnet) ceramic, which is less prone to surface Li 2 CO 3 formation compared to Al-doped Li garnets. The addition of HE Li-garnet leads to a 7-fold increase in the ionic conductivity (8.6 × 10 −5 S cm −1 at 30 °C) compared to the pure polymer, while maintaining a high Li + transference of 0.73. Proton nuclear magnetic resonance and thermogravimetric analysis results suggest that the addition of HE Li-garnet results in a lower degree of polymerization of VEC, leaving more unpolymerized VEC monomers in the matrix, serving as the governing mechanism for conductivity enhancement. The favorable interactions between HE Li-garnet particles and the polymer matrix lead to a stable and well-mixed composite with 2-fold enhancement of storage modulus at 40 °C. The simultaneous ion transport and mechanical property enhancement significantly improves the composite electrolyte's dendrite resistance and cycle life in Li symmetric cells. This work highlights the positive role HE Li-garnet can play in improving polymer electrolytes to enable lithium metal anodes.

Ock, Ji-young [Oak Ridge National Laboratory (ORNL↗
DOE OSTI2020

Overcoming immiscibility toward bimetallic catalyst library

Bimetallics are emerging as important materials that often exhibit distinct chemical properties from monometallics. However, there is limited access to homogeneously alloyed bimetallics because of the thermodynamic immiscibility of the constituent elements. Overcoming the inherent immiscibility in bimetallic systems would create a bimetallic library with unique properties. Here, we present a nonequilibrium synthesis strategy to address the immiscibility challenge in bimetallics. As a proof of concept, we synthesize a broad range of homogeneously alloyed Cu-based bimetallic nanoparticles regardless of the thermodynamic immiscibility. The nonequilibrated bimetallic nanoparticles are further investigated as electrocatalysts for carbon monoxide reduction at commercially relevant current densities (>100 mA cm -2 ), in which Cu 0.9 Ni 0.1 shows the highest multicarbon product Faradaic efficiency of ~76% with a current density of ~93 mA cm -2 . The ability to overcome thermodynamic immiscibility in multimetallic synthesis offers freedom to design and synthesize new functional nanomaterials with desired chemical compositions and catalytic properties.

25 ENERGY STORAGE↗
DOE OSTI2023

Carbon Nanotube and Graphene Oxide Reinforced Composites for Lightning Strike Protection of Composite Structures

Carbon fiber reinforced plastics (CFRP) composites have become the primary materials in the aerospace industry. Future transportation means, such as urban air mobility (UAM), will be employing CFRP structures. However, lightning strike damage on composite structures is a serious concern. CFRP composites possess low through-thickness electrical conductivity (≈ 1 S/m), which can cause extreme resistive heat in the event of lightning strikes. Research on polymeric lightning strike protection has gained momentum in the past few years. Researchers have studied various conductive fillers to improve the CFRP performance against lightning strikes. Carbon nanotubes (CNTs) and graphene oxide (GO) have been studied as future lightning Strike Protection (LSP) materials the most. The use of CNT and GO-based composites has shown improved mechanical properties and improved electrical conductivity of the composites. Researchers investigated CNTs and GO as the fillers to the matrix system, sizing the carbon fibers and the surface coating on top of the CFRP surface. This chapter highlights the remarkable improvement in the lightning damage suppression of CNT and GO-based composites and their structural applications. Special attention is given to their potential use as LSP material in future aircraft.

Kumar, Vipin↗
DOE OSTI2023

In situ probing the origin of interfacial instability of Na metal anode

The unstable and fragile solid electrolyte interphase (SEI) has restricted the application of Na metal anodes. Despite numerous research efforts being put into understanding its chemical composition and physical properties, direct observation of its formation remains a challenge due to the lack of temporal and spatial resolution. Here, through combined in situ probing techniques, we exhibit two pivotal stages associated with SEI instability during the often -neglected formation process. It is revealed that Na metal that is not uniformly passivated at the initial (passivating) stage will trigger unrestricted electrolyte decomposition and homogeneous components distribution during the subsequent (growing) stage. SEI with homogenously distributed components is found to have higher solubility than that with a layered structure evolved from a compact passivation layer. Furthermore, through demonstrating an SEI dissolution model that is closely related to its formation process and compositional distribution, this work sheds light on an uncharted territory of Na metal batteries.

25 ENERGY STORAGE↗