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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Microstructural and Mechanical Characterization of a Dispersion Strengthened Medium Entropy Alloy Produced Using Selective Laser Melting

High entropy alloys (HEAs) are an interesting new class of alloys which have been shown to exhibit both notable strength and ductility for a wide range of temperature and stresses. In addition, the remarkably small difference between the solvus and liquidus temperatures for many face centered cubic HEAs makes them an excellent candidate for selective laser melting fabrication. In this study, the microstructure and mechanical properties of a dispersion strengthened equiatomic NiCoCr alloy successfully produced using selective laser melting are explored. The effect laser speed, laser power, and powder recyclability have on final part density and microstructural segregation are analyzed through both x-ray diffraction and high resolution scanning electron microscopy. These results are further validated and compared to stable phase predictions produced using a commercially available high entropy alloy mobility database. Lastly, the tensile strengths resulting from different heat treatment pathways are detailed.

Smith, T. M.↗
DOE OSTI2024

Porous Nanographenes, Graphene Nanoribbons, and Nanoporous Graphene Selectively Synthesized from the Same Molecular Precursor

In this study, we demonstrate a family of molecular precursors based on 7,10-dibromo-triphenylenes that can selectively produce different varieties of atomically precise porous graphene nanomaterials through the use of different synthetic environments. Upon Yamamoto polymerization of these molecules in solution, the free rotations of the triphenylene units around the C–C bonds result in the formation of cyclotrimers in high yields. In contrast, in on-surface polymerization of the same molecules on Au(111) these rotations are impeded, and the coupling proceeds toward the formation of long polymer chains. These chains can then be converted to porous graphene nanoribbons (pGNRs) by annealing. Correspondingly, the solution-synthesized cyclotrimers can also be deposited onto Au(111) and converted into porous nanographenes (pNGs) via thermal treatment. Thus, both processes start with the same molecular precursor and end with a porous graphene nanomaterial on Au(111), but the type of product, pNG or pGNR, depends on the specific coupling approach. We also produced extended nanoporous graphenes (NPGs) through the lateral fusion of highly aligned pGNRs on Au(111) that were grown at high coverage. The pNGs can also be synthesized directly in solution by Scholl oxidative cyclodehydrogenation of cyclotrimers. We demonstrate the generality of this approach by synthesizing two varieties of 7,10-dibromo-triphenylenes that selectively produced six nanoporous products with different dimensionalities. The basic 7,10-dibromo-triphenylene monomer is amenable to structural modifications, potentially providing access to many new porous graphene nanomaterials. We show that by constructing different porous structures from the same building blocks, it is possible to tune the energy band gap in a wide range.

25 ENERGY STORAGE↗
DOE OSTI2021

Role of peracetic acid on the disruption of lignin packing structure and its consequence on lignin depolymerisation

Peracetic acid (PAA) is an effective oxidant capable of solubilising lignin and efficiently depolymerising it to selective phenolic compounds; however, the specific role by which PAA initiates the depolymerisation is still elusive. Herein, interaction between PAA and the lignin macromolecule and the consequent structural changes of the latter were studied by characterising the lignin packing structure and its associated changes during the oxidation process. While the lignin packing structure and its changes associated with the PAA-mediated oxidation were probed by X-ray diffraction, the impact of the PAA on different chemical functionalities present in the lignin structure was established by 13 C and 1 H– 13 C heteronuclear single-quantum coherence nuclear magnetic resonance (NMR) spectroscopy. Further, combining the NMR spectroscopy results, and the product distribution, we conclude that the predominant reaction pathway for the oxidative depolymerisation of lignin with PAA is the Baeyer–Villiger oxidation of the ketone formed by the oxidation of the benzylic hydroxyl group adjacent to the β-O-4 linkage. The experimental evidence provided herein corroborated that PAA instigates oxygen insertion to the lignin macromolecule resulting in disruption of its packing structures and facilitates depolymerisation. We also investigated various metal oxide and mixed metal oxide catalysts to identify effective catalysts that further enhance the efficiency of PAA-mediated depolymerisation of lignin and produce selective monomeric phenolic compounds. Techno-economic analysis was also conducted to identify the key parameters associated with this oxidative process that need to be considered for possible commercial application.

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

Small fatigue crack growth behavior of Ti-6Al-4V produced via selective laser melting: In situ characterization of a 3D crack tip interactions with defects

Small fatigue crack growth (SFCG) behavior is examined for additively manufactured Ti-6Al-4V specimens with optimal and trial build conditions (representing an increased degree of defects) through a combination of in situ tomography and in situ energy dispersive X-ray diffraction. The results showed slower crack growth rates for the SFCG samples compared to the long cracks (which was not expected). Finally, in the case of the trial conditions, the increased levels of porosity deterred crack growth by blunting the crack, as evident by the in situ tomography characterization.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The Electrochemical Behavior of As-Prepared Aluminum Alloy A360 Produced by Selective Laser Melting Fabrication with and without a Trivalent Chromium Process Conversion Coating

In this paper, we report on the electrochemical behavior and corrosion resistance of as-prepared aluminum alloy, A360 (AlSi10Mg), fabricated by additive manufacturing, with and without a trivalent chromium process conversion coating. Selective laser melting was the 3D printing process used for the alloy build. The corrosion suppression provided by the coating system was assessed through electrochemical measurements and accelerated degradation testing during a 14-day continuous neutral salt-spray exposure. The results indicate that the conversion coating can be formed by solution pretreating (degreasing and deoxidation) the alloy (X-Z plane perpendicular to the build plane) with its native surface roughness (as-prepared) followed by immersion for 10, 15 or 20 min in the coating bath. All three immersion times provide an equivalent level of corrosion protection to the alloy. The conversion coating suppresses both anodic and cathodic currents, increases the polarization resistance, and provides both anodic and cathodic corrosion protection to the as-prepared alloy. The conversion-coated specimens exhibit good stand-alone corrosion resistance during a 14-day neutral salt-spray exposure with corrosion intensity values (g/m 2 -year) ~10x lower than values for the uncoated, as-prepared alloy specimens.

36 MATERIALS SCIENCE↗
DOE OSTI2026

MoS 2 Catalysts Selectively Achieve High Yield of Liquid Oxygenate from Direct Conversion of Methane via Hydroxyl Radicals

Directly converting methane (CH 4 ) into liquid oxygenates (e.g., methanol) can circumvent the cost and engineering limits of natural gas transportation and storage. However, oxygenate yields from CH 4 remain low, and sulfur present in natural gas hinders activity in most catalysts. Here, to overcome these barriers, we employ bulk molybdenum disulfide (MoS 2 ), a low-cost, robust catalyst which selectively produces large quantities of liquid oxygenates (>900 µmol/g cat ∙hr) from methane in the presence of hydroxyl (OH • ) radicals produced from dilute hydrogen peroxide (H 2 O 2 ) at 75°C. Under realistic reaction conditions, MoS 2 partially and reversibly adopts a metastable, more electrically conductive phase (1T’) that can only be observed through in situ structural probes. Herein, we elucidate that redox synergy between H 2 O 2 and MoS 2 produces active OH • radical species that selectively transform CH 4 to surface methoxy species at the gas-solid liquid interface, leading to the unitary production of liquid oxygenate at a rate competitive with more costly precious metal catalysts, without additional catalyst preparation steps.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Sub-Nanometer Nanoclusters of Copper Atop Single-Atom Copper Moieties toward Electrochemical CO 2 Hydrogenation to Methane

The electrochemical CO 2 reduction (eCO 2 R) offers a compelling route for converting CO 2 into value-added fuels and chemicals. Among CO 2 -derived products, methane (CH 4 ) occupies a distinct position, serving both as a key intermediate for emerging cascade electro-oxidation to oxygenates and as a strategically important extraterrestrial fuel that can be generated in situ from off-planet CO 2 resources. Although Cu-based catalysts capable of selectively producing CH 4 have been reported, they seldom sustain high selectivity at practically relevant current densities. Here, we created a single-step co-pyrolysis strategy toward generating and anchoring Cu sub-nanometer clusters (Cu SNC ) atop Cu-N x single-atom (SA) motifs embedded within N-doped carbon (NC), with controllable nanostructures through tuning of the synthesis parameters. Complementary spectroscopic analyses and density functional theory (DFT) calculations help reveal a structure−activity correlation that could guide the catalyst design. The Cu SNC @NC sample synthesized at 550 °C pyrolysis temperature (best described and modeled as Cu 3 -CuN 4 domains) represents the most effective combination of cluster size, metal-nitrogen coordination, and adsorption energetics needed to selectively promote CH 4 generation versus other eCO 2 R products. Incorporating pulsed electrolysis and hydrophobicity-modulated transport tuning at the triple-phase boundary (TPB) further enhanced CH 4 production achieving a partial CH 4 current density of ∼321 mA cm −2 , 53% Faradaic efficiency (FECH 4 ), and less than 4% combined FE for other eCO 2 R products, simplifying downstream CH 4 purification or upgrading. This work establishes generalizable principles for controlling Cu cluster atomicity and metal−nitrogen coordination, both of which are recognized determinants of CH 4 -efficient eCO 2 R.

CH4 production↗
DOE OSTI2025

Microwave-Assisted Reactive CO 2 Capture with the SrCO 3 -Graphite System

This study details the initial development of a microwave heat-driven reactive CO 2 capture (RCC) process using the SrO/SrCO 3 cycle and graphitic carbon to absorb ppm-levels of CO 2 from humidified room temperature air and selectively convert it into CO. By combining first-principles density functional theory (DFT) simulations with thermogravimetric analysis (TGA) and X-ray diffraction (XRD) verification, it is demonstrated that SrO spontaneously absorbs moisture to generate Sr(OH) 2 followed by Sr(OH) 2 *1H 2 O, which then can spontaneously react with atmospheric levels of CO 2 to form SrCO 3 . The resulting SrCO 3 can then react with solid carbon at elevated temperatures to selectively produce CO and regenerate SrO. Graphitic carbon is an excellent microwave absorber that can quickly generate temperatures approaching 1000 °C and then cool to room temperature within minutes, potentially allowing for integration with intermittent electricity. It is shown that using microwaves to selectively heat a mixture of graphitic carbon and SrCO 3 produced CO with 85 ± 3% selectivity and stable performance over ten cycles. The rapid heating for release and room temperature CO 2 uptake processes appeared to prevent performance loss from particle sintering typically observed with traditional thermal systems. In conclusion, these results demonstrate a new RCC approach that adds to the growing number of potential technologies available for converting CO 2 to useful chemicals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1977

Production of simple molecules on the surface of Mercury

Lunar sample studies have shown that solar-wind irradiation of the lunar surface has produced a variety of low-molecular-weight compounds. Analysis of the lunar soils has revealed the presence of H2, CH4, H2O, N2, CO, CO2, He, Ne and other components which are extralunar. Irradiation experiments on lunar materials and analogs have shown that solar-wind and solar-flare irradiation of the lunar surface produces selected low-molecular-weight components. Solar-wind irradiation of Mercury's surface should also produce a wide variety of low-molecular-weight species because of the increased solar flux, which results from Mercury being nearer the sun than the moon. The thermal regime of Mercury's surface would result in thermal evaporation of low-temperature components followed by 'cold-trapping' on the night-time side of the planet. Such desorption-adsorption processes assist chemical weathering of Mercury's regolith.

Gibson, E. K., Jr.↗
NASA NTRS1996

Method and device for producing a tactile display using an electrorheological fluid

A tactile display device utilizes an electrorheological fluid to activate a plurality of tactile dots. A voltage is selectively produced uniformly across an electrorheological fluid flowing between a common ground electrode and a plurality of conductive dot electrodes, thereby producing an increase in the fluid's viscosity to the extent that fluid flow between the two electrodes is restricted. The flow restriction produces a build-up of electrorheological fluid in a corresponding dot actuator chamber. The resulting pressure increase in the chamber displaces an elastic diaphragm fixed to a display surface to form a lump which can be perceived by the reader as one dot in a Braille character cell. A flow regulation system provides a continually pressurized flow system and provides for free flow of the electrorheological fluid through the plurality of dot actuator chambers when they are not activated. The device is adaptable to printed circuit techniques and can simultaneously display tactile dots representative of a full page of Braille characters stored on a medium such as a tape cassette or to display tactile dots representative of non-Braille data appearing on a computer monitor or contained on another data storage medium. In an alternate embodiment, the elastic diaphragm drives a plurality of spring-loaded pins provided with positive stops to maintain consistent displacements of the pins in both their actuated and nonactuated positions.

Garner, H. Douglas↗
DOE OSTI2024

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods

Abstract CeO 2 nanorod based catalysts for the base‐free synthesis of azoxy‐aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (O v ) and base sites are critical for their excellent catalytic properties. The O v , i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α−C sp3 −H in ethanol to the nitro group coupling it to the redox reactions between Ce 3+ and Ce 4+ . At the same time, the base sites catalyze the condensation step to selectively produce azoxy‐aromatics. The catalytic route opens a much improved way to use non‐noble metal oxides without additives for the selective functional group reduction and coupling reactions.

Yuan, Ziliang↗
DOE OSTI2023

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods

CeO 2 nanorod based catalysts for the base-free synthesis of azoxy-aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (O v ) and base sites are critical for their excellent catalytic properties. The O v , i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α–C sp3 –H in ethanol to the nitro group coupling it to the redox reactions between Ce 3+ and Ce 4+ . At the same time, the base sites catalyze the condensation step to selectively produce azoxy-aromatics. Finally, the catalytic route opens a much improved way to use non-noble metal oxides without additives for the selective functional group reduction and coupling reactions.

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

Direct Comparison of the Activity and Selectivity of Rh 1 Cu and Ni 1 Cu Single-Atom Alloy Sites for Ethanol Decomposition

Ethanol is an important source of clean hydrogen, acetaldehyde, acetic acid, acetate esters, and light hydrocarbons. Controlling the divergent reaction pathways to these products requires understanding how different active sites influence the elementary steps involved. Herein, we present a combined surface science, theory, and nanoparticle catalysis study demonstrating how two single-atom dopants (Rh and Ni) in a Cu host can distinctively alter the selectivity of alcohol conversion. Specifically, our model studies reveal that ethanol reacts on Ni 1 Cu single-atom alloys to selectively produce acetaldehyde, whereas methane and CO are also formed on Rh 1 Cu single-atom alloys. Interestingly, these different reactivities are in contrast to the behavior of the pure metals as Ni(111) and Rh(111) surfaces favor methane/CO and surface carbon/CO, respectively. DFT calculations of reaction pathways and simulated product desorption based on microkinetic analyses explain these reactivity differences, demonstrating that C–C cleavage leading to methane formation has a lower barrier on Rh single-atom sites. To test the catalytic relevance of these fundamental results we synthesized and characterized supported Ni 1 Cu and Rh 1 Cu single-atom alloy nanoparticles with dopant:Cu ratios of 1:200. Flow reactor results revealed that both Ni and Rh increased ethanol conversion over Cu and that Ni 1 Cu catalysts were >99.9% selective to acetaldehyde, while Rh 1 Cu also produced 0.6%–2.6% of equimolar methane and CO between 433 and 493 K, demonstrating that C–C bond cleavage is enabled by isolated Rh sites. Furthermore, these catalytic results bridge the pressure and materials gaps, and together, this study provides insights into how different isolated dopant sites promote different catalytic pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Non-equilibrium plasma co-upcycling of waste plastics and CO 2 for carbon-negative oleochemicals

Mechanical recycling and chemical upcycling by thermochemical reactions have been the major approaches for recycling end-of-life plastics. Herein, we report an electrified approach to upcycle waste plastics into carbon-negative commodity chemicals using greenhouse gas CO 2 as the oxidant and additional carbon source. In this non-equilibrium plasma process, waste polyolefins were oxidatively depolymerized by plasma-activated CO 2 to produce oleochemicals and hydrocarbon chemicals in a single-step process at high reaction rates. In addition, a mixture of CO 2 and a small amount of O 2 was employed as plasma gases to selectively produce fatty alcohols from polyolefins. Based on this atmospheric pressure, non-solvent, and non-catalyst process, up to 97.6% of fatty alcohols could be produced within minutes. In this article, the co-conversion approach was demonstrated using common polyolefins and real-world mixed waste plastics to obtain comparable results. The techno-economic analysis estimates the internal rate of return to be 42.2% and 43.5% for the plasma-based conversion of waste plastics, depending on the plasma gas composition. Lifecycle assessment indicates the global warming potential is between −3.33 and −3.07 kg CO 2e per kg of plastic.

42 ENGINEERING↗
DOE OSTI2021

Evaluating the stability and activity of dilute Cu-based alloys for electrochemical CO 2 reduction

Cu-based catalysts currently offer the most promising route to actively and selectively produce value-added chemicals via electrochemical reduction of CO 2 (eCO 2 R); yet further improvements are required for their wide-scale deployment in carbon mitigation efforts. Here, we systematically investigate a family of dilute Cu-based alloys to explore their viability as active and selective catalysts for eCO 2 R through a combined theoretical–experimental approach. Using a quantum–classical modeling approach that accounts for dynamic solvation effects, we assess the stability and activity of model single-atom catalysts under eCO 2 R conditions. Our calculations identify that the presence of eCO2R intermediates, such as CO*, H*, and OH*, may dynamically influence the local catalyst surface composition. Additionally, we identify through binding energy descriptors of the CO*, CHO*, and OCCO* dimer intermediates that certain elements, such as group 13 elements (B, Al, and Ga), enhance the selectivity of C 2+ species relative to pure Cu by facilitating CO dimerization. The theoretical work is corroborated by preliminary testing of eCO 2 R activity and selectivity of candidate dilute Cu-based alloy catalyst films prepared by electron beam evaporation in a zero-gap gas diffusion electrode-based reactor. Of all studied alloys, dilute CuAl was found to be the most active and selective toward C 2+ products like ethylene, consistent with the theoretical predictions. Finally, we attribute the improved performance of dilute CuAl alloys to more favorable dimerization reaction energetics of bound CO species relative to that on pure Cu. In a broader context, the results presented here demonstrate the power of our simulation framework in terms of rational catalyst design.

30 DIRECT ENERGY CONVERSION↗