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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Enhanced Catalyst Durability for Bio-Based Adipic Acid Production by Atomic Layer Deposition

Harsh reaction environments challenge the lifetime productivity of conventional catalysts and impede emerging biobased chemical processes. Condensed-phase processing of muconic acid, a biobased platform chemical, leads to problematic levels of catalyst leaching and fouling. Atomic layer deposition (ALD) can improve catalyst durability using protective metal oxide coatings; however, a targeted coating strategy and cost models thereof are needed for application-specific deactivation challenges that can surmount these challenges while accounting for process implications. Herein, we utilize thin (<5 wt% Al) Al2O3 ALD coatings to increase the lifetime productivity of Pd/TiO2 during muconic acid hydrogenation to adipic acid. The ALD coating decreases Pd leaching by >3x and markedly improves the thermal stability of Pd and TiO2. Economic analysis for an adipic acid biorefinery supports that increased material costs and reduced catalyst productivity can be justified through lifetime extension. Broadly, this work lays the foundation for reducing the cost of biobased chemical processes through catalyst stability.

Settle, Amy↗
DOE OSTI2018

Ion irradiation induced nucleation and growth of nanoparticles in amorphous silicon carbide at elevated temperatures

Ion irradiation induced crystallization in as-deposited amorphous SiC films is investigated using grazing-angle incidence x-ray diffraction (GIXRD), transmission electron microscopy (TEM) and Raman spectroscopy. Irradiation with 5 MeV Xe to fluence of 115 Xe/nm2 at 700 K results in a homogenous distribution of 3C-SiC grains with an average crystallite size of ~5.7 nm over the entire film thickness (~1 µm). The nucleation and growth processes exhibit a weak dependence on dose in displacements per atom (dpa) in the dose range from 6 to 20 dpa. A transformation of homonuclear C-C bonds from sp3 to sp2 hybridization is observed in the irradiated films, which may be partly responsible for the observed grain size saturation. The results from this study may have a significant impact on synthesis of nanograins in amorphous SiC and other similar materials with effective control of grain size and density by ion irradiation.

phase transformation, SiC, ion irradiation↗
DOE OSTI2020

Influence of Tabula Rasa on Process- and Light-Induced Degradation of Solar Cells Fabricated From Czochralski Silicon

Monocrystalline Si solar cells are fabricated from Czochralski (Cz) Si, which contains 10 17 –10 18 cm -3 oxygen atoms. Cz Si undergoes degradation during high-temperature thermal processing steps, such as dopant diffusion to form the p - n junction. This degradation in the bulk minority carrier lifetime can be related to the formation of oxygen precipitates. We found that a high-temperature annealing process known as tabula rasa (TR) not only mitigates process-induced degradation via oxygen precipitate nuclei dissolution, but also modifies subsequent light-induced degradation. We report on the bulk carrier lifetime of n - and p -type Cz Si after TR, which homogenizes the interstitial oxygen in the bulk Si to its monoatomic form in either an N 2 or O 2 environment. A control sample, which was not subjected to a TR processing step, experienced severe process-induced degradation during a boron emitter thermal budget as oxygen precipitates were formed in the Si bulk. These precipitates could be imaged using photoluminescence. Additionally, samples that underwent a TR processing step prior to the boron emitter thermal budget show efficient gettering of metallic impurities compared to the control sample, which showed a decline in the implied open-circuit voltage after the gettering step. Furthermore, modification of the interstitial oxygen bonding by TR had a strong effect on the light-induced degradation kinetics. Instead of a typically observed monotonic decrease, minority carrier lifetime increases first, followed by a nonmonotonic decrease over a ~20 h period. Finally, we conclude that by modifying the interstitial oxygen bonding via TR pretreatment, p -type Cz Si wafers become substantially resistant to harsh solar cell processes and strongly modified light-induced degradation, which would open alternative ways to mitigate this degradation mechanism.

14 SOLAR ENERGY↗
DOE OSTI2025

In situ electron microscopy: atomic-scale dynamics of metal oxidation and corrosion

Corrosion degrades metals through complex microscopic processes that traditional methods often fail to capture. In-situ transmission electron microscopy (TEM) bridges this gap by providing real-time atomic-scale imaging of oxidation and corrosion dynamics. Gas-phase TEM uncovers critical oxidation mechanisms like oxide nucleation and alloying effects, while liquid-phase TEM tracks corrosion initiation. Coupled with emerging techniques like ultrafast direct electron detection cameras, these advancements promise unprecedented resolution in understanding material degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Manufacture aluminum alloy tube from powder with a single-step extrusion via ShAPE

Mechanical performance of aluminum in terms of strength, wear and corrosion resistance, especially high-temperature strength has been shown to improve with the addition of transition metal (TM) elements of Fe, Cr, and Ti. However, these feedstock materials occur as powders. As such, the traditional fabrication process is complex and expensive because it requires multiple procedures and consumes considerable energy. This study developed Shear Assisted Processing and Extrusion (ShAPE) as a single-step process that manufactures tubes directly from Al-TM powders obtained via gas atomization. Meter-long Al-TM alloy tubes are extruded from powders with different processing conditions. The ShAPE tubes have very low porosity and the average density is 2.94 kg/cm 3 , which is equal to or higher than parts fabricated by hot extrusion and sintering. The powder-to-tube fabrication process was revealed and discussed by examining the microstructural evolution. The Vickers hardness of ShAPE tubes ranges from 110 to 140 HV through wall thickness and at different extrusion speeds. The variation in hardness was correlated with the extent of refinement of intermetallics and attributed to the shear deformation per unit extrusion length. Energy cost analysis shows that ShAPE save ~60% energy compared to the conventional sintering and extrusion processes. Results indicate ShAPE is a low-cost, high-efficiency manufacturing process for producing tubes from metallic powders.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Large scale dissociation of molecular gas in the sprial arms of M51

The distribution of the atomic and ionized hydrogen along the inner spiral arms of M51 are compared. As is the case in M83, the location of both these phases of the interstellar medium with respect to the major dust lanes suggests that molecular hydrogen is dissociated on kpc scales in active star-forming regions, and that this dissociation process may strongly affect the observed morphology of atomic hydrogen in spiral arms.

Tilanus, R. P. J.↗
DOE OSTI2019

Selective Photo‐Oxygenation of Light Alkanes Using Iodine Oxides and Chloride

Abstract Partial oxidation of light alkanes to generate alkyl esters has been achieved under photochemical conditions using mixtures of iodine oxides and chloride salts in trifluoroacetic acid (HTFA). The reactions are catalytic in chloride and are successful using compact fluorescent light, but higher yields are obtained using a mercury lamp. In this photo‐initiated oxyesterification process, the robust alkyl ester products are resistant to over‐oxidation, and under optimized conditions yields for alkyl ester production of ∼50 % based on methane, ∼60 % based on ethane (with a total functionalized yield of EtX (X=TFA or Cl) of 80 %) and ∼30 % based on propane have been demonstrated. The reaction also proceeds in aqueous HTFA and dichloroacetic acid with lower yields. Mechanistic studies indicate that the process likely operates by a chlorine hydrogen atom abstraction pathway wherein alkyl radicals are generated, trapped by iodine, and converted to alkyl trifluoroacetates in situ .

Liebov, Nichole S.↗
DOE OSTI2018

Nanoscale Solute Partitioning and Carbide Precipitation in a Multiphase TRIP Steel Analyzed by Atom Probe Tomography

Nanoscale solute partitioning across multiple constituent phases in a 980-grade quenched and partitioned (Q&P) steel was analyzed using atom probe tomography (APT). The Q&P process was used to increase the C content in the retained austenite phase thereby improving its stability under plastic straining. Significant carbon enrichment of austenite was measured with decreased levels of C in martensite and almost depleted C content in ferrite, supporting the C partitioning mechanism in the literature. The APT analysis of retained austenite surrounded by martensite demonstrated a higher amount of C content compared with retained austenite surrounded by the ferrite phase. Lath and discrete carbide particle precipitation was also observed inside martensite colonies, tying up C and reducing the total amount of C available for austenite stabilization. In addition, the partitioning of Mn and other minor elements was quantitatively investigated by correlating APT and SEM-EBSD. Furthermore, these techniques provide a robust methodology for analyzing nanoscale compositional partitioning in multiphase steels, TRIP steels in particular, which can be used to better explain their microstructure-mechanical property relationships.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Formation of helium-bubble networks in tungsten

The nucleation and subsequent growth of helium bubbles in bulk tungsten is investigated using molecular dynamics simulations. By considering a setting that includes the diffusion process of helium clusters, we study their attachment to existing bubbles and their interaction with tungsten crowdion structures generated in the bubble growth process. Here, we find that incoming helium atoms, and especially small helium clusters, can become trapped in the crowdion structures, providing nucleation sites for new helium bubbles, and leading to a distributed network of bubbles rather than a single, growing bubble. The nature of this network depends on both the temperature and the implantation flux of helium. Our results indicate that the kinetic interaction of He with generated dislocations is a key factor dictating the evolution of bubble distributions in plasma-exposed tungsten.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Vacancy-mediated complex phase selection in high entropy alloys

Phase selection in Ti-Zr-Hf-Al high-entropy alloys was investigated by in-situ high-energy x-ray diffraction, single-crystal x-ray diffraction, and KKR-CPA electronic-structure methods that address disorder and vacancies, predicting formation enthalpy and chemical short-range order (SRO). Samples with varying Al content were synthesized, characterized, and computationally assessed to ascertain the composition-dependent phase selection, as increased Al content often acts as a stabilizer of a body-centered-cubic structure. Equiatomic TiZrHfAl was especially interesting due to its observed bcc superstructure – a variant of γ-brass with 4 vacancies per cell (not 2 as in γ-brass). We highlight how vacancy ordering mediates selection of this variant of γ-brass, which is driven by vacancy-atom SRO that dramatically suppress all atomic SRO. As vacancies are inherent in processing refractory systems, we expect that similar discoveries await in other high entropy alloys or in revisiting older experimental data.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Diffusion in intact secondary cell wall models of plants at different equilibrium moisture content

Secondary plant cell walls are composed of carbohydrate and lignin polymers, and collectively represent a significant renewable resource. Leveraging these resources depends in part on a mechanistic understanding for diffusive processes within plant cell walls. Common wood protection treatments and biomass conversion processes to create biorefinery feedstocks feature ion or solvent diffusion within the cell wall. X-ray fluorescence microscopy experiments have determined that ionic diffusion rates are dependent on cell wall hydration as well as the ionic species through non-linear relationships. In this work, we use classical molecular dynamics simulations to map the diffusion behavior of different plant cell wall components (cellulose, hemicellulose, lignin), ions (Na + , K + , Cu2 + , Cl - ) and water within a model for an intact plant cell wall at various hydration states (3-30 wt% water). From these simulations, we analyze the contacts between different plant cell wall components with each other and their interaction with the ions. Generally, diffusion increases with increasing hydration, with lignin and hemicellulose components increasing diffusion by an order of magnitude over the tested hydration range. Ion diffusion depends on charge. Positively charged cations preferentially interact with hemicellulose components, which include negatively charged carboxylates. As a result, positive ions diffuse more slowly than negatively charged ions. Measured diffusion coefficients are largely observed to best fit piecewise linear trends, with an inflection point between 10 and 15% hydration. These observations shed light onto the molecular mechanisms for diffusive processes within secondary plant cell walls at atomic resolution.

09 BIOMASS FUELS↗
DOE OSTI2025

Ultrafast Electron–Dipole Interactions in TeO- Photodetachment

We present direct experimental evidence of ultrafast coupling between ejected electrons and dynamically forming dipole moments in TeO, captured during the photodetachment of TeO?. By combining high-resolution cryogenic photoelectron spectroscopy with velocity-map imaging, we assess previously inaccessible excited states and resolve rich photoelectron angular distributions (PADs) that encode electron–dipole interactions. Systematic comparison of PADs from femtosecond and picosecond lasers reveals striking deviations from free-electron behavior, representing direct evidence of a transient dipole moment evolving on femtosecond timescales. Quantitative analysis pinpoints the dipole buildup time to be within ~60 fs, providing real-time access to the birth of a molecular dipole field. This work establishes a general approach to probing electron-dipole interactions in their formation stages, offering fundamental insights into the ultrafast interplay between departing electrons and transient polar systems — a process that lies at the core of atomic, molecular, and ultrafast physics.

Yang, Fan↗
DOE OSTI2018

Three-Dimensional Solid-State Lithium-Ion Batteries Fabricated by Conformal Vapor-Phase Chemistry

Three-dimensional thin-film solid-state batteries (3D TSSB) were proposed by Long et al. in 2004 as a structure-based approach to simultaneously increase energy and power densities. Here, we report experimental realization of fully conformal 3D TSSBs, demonstrating the simultaneous power-and-energy benefits of 3D structuring. All active battery components—electrodes, solid electrolyte, and current collectors—were deposited by atomic layer deposition (ALD) onto standard CMOS processable silicon wafers microfabricated to form arrays of deep pores with aspect ratios up to approximately 10. The cells utilize an electrochemically prelithiated LiV 2 O 5 cathode, a very thin (40–100 nm) Li 2 PO 2 N solid electrolyte, and a SnNx anode. The fabrication process occurs entirely at or below 250 °C, promising compatibility with a variety of substrates as well as integrated circuits. The multilayer battery structure enabled all-ALD solid-state cells to deliver 37 μAh/cm 2 ·μm (normalized to cathode thickness) with only 0.02% per-cycle capacity loss. Conformal fabrication of full cells over 3D substrates increased the areal discharge capacity by an order of magnitude while simulteneously improving power performance, a trend consistent with a finite element model. Furthermore, this work shows that the exceptional conformality of ALD, combined with conventional semiconductor fabrication methods, provides an avenue for the successful realization of long-sought 3D TSSBs which provide power performance scaling in regimes inaccessible to planar form factor cells.

25 ENERGY STORAGE↗
DOE OSTI2019

In-situ electron microscopy mapping of an order-disorder transition in a superionic conductor

Solid-solid phase transitions are processes ripe for the discovery of correlated atomic motion in crystals. Here, we monitor an order-disorder transition in real-time in nanoparticles of the super-ionic solid, Cu 2-x Se. The use of in-situ high-resolution transmission electron microscopy allows the spatiotemporal evolution of the phase transition within a single nanoparticle to be monitored at the atomic level. The high spatial resolution reveals that cation disorder is nucleated at low co-ordination, high energy sites of the nanoparticle where cationic vacancy layers intersect with surface facets. Time-dependent evolution of the reciprocal lattice of individual nanoparticles shows that the initiation of cation disorder is accompanied by a ~3% compression of the anionic lattice, establishing a correlation between these two structural features of the lattice. The spatiotemporal insights gained here advance understanding of order-disorder transitions, ionic structure and transport, and the role of nanoparticle surfaces in phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Guided anisotropic oxygen transport in vacancy ordered oxides

Abstract Anisotropic and efficient transport of ions under external stimuli governs the operation and failure mechanisms of energy-conversion systems and microelectronics devices. However, fundamental understanding of ion hopping processes is impeded by the lack of atomically precise materials and probes that allow for the monitoring and control at the appropriate time- and length- scales. In this work, using in-situ transmission electron microscopy, we directly show that oxygen ion migration in vacancy ordered, semiconducting SrFeO 2.5 epitaxial thin films can be guided to proceed through two distinctly different diffusion pathways, each resulting in different polymorphs of SrFeO 2.75 with different ground electronic properties before reaching a fully oxidized, metallic SrFeO 3 phase. The diffusion steps and reaction intermediates are revealed by means of ab-initio calculations. The principles of controlling oxygen diffusion pathways and reaction intermediates demonstrated here may advance the rational design of structurally ordered oxides for tailored applications and provide insights for developing devices with multiple states of regulation.

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

Creation of discrete active site domains via mesoporous silica poly(styrene) composite materials for incompatible acid–base cascade reactions

This work highlights the design and synthesis of bifunctional mesoporous silicate – polymer composite dual acid–base supported cascade catalysts. Compartmentalization of the two incompatible active sites is sought by segregating acid sites on the silica surface, and base sites within polymer chains and/or polymer domains. The ability to isolate and segregate active sites via control of the mesoporous silica pore size and polymer molecular weight is probed with silica samples functionalized by a grafting-to process. Supplemental activator and reducing agent (SARA) atom transfer radical polymerization is used to synthesize random copolymers containing protected primary amines. Thiol–ene ‘click’ chemistry facilitates silica functionalization via a convergent approach, with the ene-functionalized polymer end group and silica-grafted thiols forming SBA/MCM-SH-poly(styrene-co-2-(4-vinylbenzyl)isoindoline-1,3-dione). Polymer deprotection and thiol oxidation produces primary amine/sulfonic acid containing composite catalysts. With the polymer supported Lewis base and silica grafted Brønsted acid, the two-step deacetalization – Knoevenagel condensation cascade is explored to assess the ability of these polymer/silica hybrids to segregate active sites, allowing both acid and base site accessibility. Six composite catalysts are synthesized and tested in individual and cascade reactions with kinetic results demonstrating that lower molecular weight SBA-15-P1 and MCM-41-P1 catalysts outperform (higher turnover frequencies and initial rates) their higher molecular weight analogues, as well as a polymer-free system containing molecular active sites dispersed on the silica surface. Higher molecular weight composite catalysts perform more poorly due to limited chain solubility, mass transfer limitations, and poor catalyst accessibility. In many cases, the polymer chains effectively thread into the mesopores, with higher molecular weight polymers leading to pore blockage and inhibited mass transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electron inelastic mean free path in water

Liquid phase transmission electron microscopy (LPTEM) is rapidly developing as a powerful tool for probing processes in liquid environments with close to atomic resolution. Knowledge of the water thickness is needed for reliable interpretation and modelling of analytical studies in LPTEM, and is particularly essential when using thin liquid layers, required for achieving the highest spatial resolutions. Furthermore, the log-ratio method in electron energy-loss spectroscopy (EELS) is often applied in TEM to quantify the sample thickness, which is measured relative to the inelastic mean free path ( λ IMFP ). However, λ IMFP itself is dependent on sample material, the electron energy, and the convergence and divergence angles of the microscope electronoptics. Here, we present a detailed quantitative analysis of the λ IMFP of water as functions of the EELS collection angle ( β ) at 120 keV and 300 keV in a novel nanochannel liquid cell. We observe good agreement with earlier studies conducted on ice, but find that the most widely used theoretical models significantly underestimate λ IMFP of water. We determine an adjusted average energy-loss term E m, water , and characteristic scattering angle θ E, water that improve the accuracy. The results provide a comprehensive knowledge of the λ IMFP of water (or ice) for reliable interpretation and quantification of observations in LPTEM and cryo-TEM studies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Ensuring thermodynamic consistency with invertible coarse-graining

Coarse-grained models are a core computational tool in theoretical chemistry and biophysics. A judicious choice of a coarse-grained model can yield physical insights by isolating the essential degrees of freedom that dictate the thermodynamic properties of a complex, condensed-phase system. The reduced complexity of the model typically leads to lower computational costs and more efficient sampling compared with atomistic models. Designing “good” coarse-grained models is an art. Generally, the mapping from fine-grained configurations to coarse-grained configurations itself is not optimized in any way; instead, the energy function associated with the mapped configurations is. In this work, we explore the consequences of optimizing the coarse-grained representation alongside its potential energy function. We use a graph machine learning framework to embed atomic configurations into a low-dimensional space to produce efficient representations of the original molecular system. Because the representation we obtain is no longer directly interpretable as a real-space representation of the atomic coordinates, we also introduce an inversion process and an associated thermodynamic consistency relation that allows us to rigorously sample fine-grained configurations conditioned on the coarse-grained sampling. We illustrate that this technique is robust, recovering the first two moments of the distribution of several observables in proteins such as chignolin and alanine dipeptide.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗