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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Adaptive Discovery and Mixed-Variable Optimization of Next Generation Synthesizable Microelectronic Materials

Design of new microelectronic materials is characterized by several challenges such as high-dimensionality of the atomic structure-composition variable space, formidable cost of directly using high-fidelity simulations for design optimization, dispersity in literature-reported similar materials and synthesis methods, complex physical mechanisms, and mixed qualitative and quantitative design variables that lead to a disjointed design space. Even though machine learning (ML) techniques have been employed to expedite materials innovation, existing methods treat ML and design optimization as two separate processes, failing to resolve the fundamental challenges associated with high dimensionality and mixed-variable complexity. We have developed a ML enhanced mixed-variable material design optimization framework to efficiently extract useful information from existing data in literature and physics-based simulations to guide the autonomous search for optimal materials. Our proposed framework is composed of four computational modules: (1) a natural language processing (NLP) based virtual screening module, (2) classification based concept exploration module, (3) a density functional theory (DFT)-based high-fidelity evaluation model, and (4) a novel latent-variable Gaussian process (LVGP) ML model for mixed-variable problems with uncertainty quantification, which seamlessly integrates with Bayesian Optimization (BO) and achieves superb efficiency through embedded physics-based dimension reduction. Our approach is demonstrated and validated using the testbed of functional materials exhibiting metal-insulation transitions (MITs), with the targeted reversible resistivity changes (∼10^5) near room temperature. At the end of the 30-month project, we have developed a series of new ML techniques using NLP, conditional variational autoencoders, active learning, latent-variable Gaussian processes, integrated with Bayesian optimization. Our project has resulted in new predicted MITs compounds and improved understanding of MITs microscopic mechanisms, which in turn will revolutionize microelectronics science to provide energy-saving solutions. Our research has improved both creativity and efficiency in transforming rare-event discoveries of new functional materials to persistent innovations. In addition to open-sourcing the online MIT database and the classification model, the LVGP open source code has been downloaded more than 15,000 times within two years. More than 40 MIT compounds have been identified and many have been pursued experimentally via collaborators. The research results are published in close to 20 collaborative papers in high-impact journals, such as Chem. Mater., Appl. Phys. Rev., Sci. Rep., among others of design space.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Pulse control of superconducting cavity-based qudits with a Fock-state basis

Fock-basis-encoding qudits allow quantum gates to operate on multiple qudit levels simultaneously. This capability is advantageous for applications involving complex local gate operations, such as the digital quantum simulation of non-Abelian gauge theories. However, compiling unitary operations to native qudit gates remains a challenging task, often requiring substantial computational resources. In this work, we theoretically investigate the direct pulse control of a superconducting radio-frequency cavity coupled to an ancilla transmon for gate synthesis. We will discuss the improvements and limitations applicable to high Fock states. This work paves the way toward more efficient and robust qudit-gate synthesis.

Li, Andy C.Y. [Fermilab] (ORCID:0000000345423739)↗
DOE OSTI2026

Pulse control of superconducting cavity-based qudits with a Fock-state basis

Fock-basis-encoding qudits allow quantum gates to operate on multiple qudit levels simultaneously. This capability is advantageous for applications involving complex local gate operations, such as the digital quantum simulation of non-Abelian gauge theories. However, compiling unitary operations to native qudit gates remains a challenging task, often requiring substantial computational resources. In this work, we theoretically investigate the direct pulse control of a superconducting radio-frequency cavity coupled to an ancilla transmon for gate synthesis. We will discuss the improvements and limitations applicable to high Fock states. This work paves the way toward more efficient and robust qudit-gate synthesis.

Li, Andy C.Y. [Fermilab] (ORCID:0000000345423739)↗
DOE OSTI2024

Optimization and purification of magnesium borides fabricated by combustion synthesis and by high-temperature sintering

Hydrogen as a fuel provides several benefits over the use of fossil fuels; however, one challenge in utilizing hydrogen as an energy carrier revolves around its storage. Achieving sufficient volumetric hydrogen density in a storage solution will facilitate hydrogen’s adoption for use in both stationary and mobile applications. Solid-state hydrogen storage provides a promising pathway to solving this problem. However, the hydrogenation of these materials is characterized by slow kinetics and extreme thermodynamic conditions. Magnesium borohydride (Mg(BH4)2) is a promising material in hydrogen storage due to its reversible properties and a theoretical hydrogen capacity of 14.9 wt.%. To synthesize this material, combustion synthesis of magnesium borides (MgBx) has been implemented with the aim to further lower thermodynamic requirements for direct hydrogenation. A drawback of this process is the potential formation of oxide contaminants, which decrease hydrogenation/dehydrogenation and recyclability performance. The present work focuses on identifying parameters useful for reducing contamination and evaluating potential pathways to the purification of magnesium borides with the goal of improving their quality.

Camarena, Miguel Joaquin↗
DOE OSTI2022

Halide perovskites as disposable epitaxial templates for the phase-selective synthesis of lead sulfochloride nanocrystals

Colloidal chemistry grants access to a wealth of materials through simple and mild reactions. However, even few elements can combine in a variety of stoichiometries and structures, potentially resulting in impurities or even wrong products. Similar issues have been long addressed in organic chemistry by using reaction-directing groups, that are added to a substrate to promote a specific product and are later removed. Inspired by such approach, we demonstrate the use of CsPbCl 3 perovskite nanocrystals to drive the phase-selective synthesis of two yet unexplored lead sulfochlorides: Pb 3 S 2 Cl 2 and Pb 4 S 3 Cl 2 . When homogeneously nucleated in solution, lead sulfochlorides form Pb 3 S 2 Cl 2 nanocrystals. Conversely, the presence of CsPbCl 3 triggers the formation of Pb 4 S 3 Cl 2 /CsPbCl 3 epitaxial heterostructures. The phase selectivity is guaranteed by the continuity of the cationic subnetwork across the interface, a condition not met in a hypothetical Pb 3 S 2 Cl 2 /CsPbCl 3 heterostructure. The perovskite domain is then etched, delivering phase-pure Pb 4 S 3 Cl 2 nanocrystals that could not be synthesized directly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Low-thermal-budget synthesis of monolayer molybdenum disulfide for silicon back-end-of-line integration on a 200 mm platform

Two-dimensional (2D) materials are promising candidates for future electronics due to their excellent electrical and photonic properties. Although promising results on the wafer-scale synthesis (≤150 mm diameter) of monolayer molybdenum disulfide (MoS 2 ) have already been reported, the high-quality synthesis of 2D materials on wafers of 200 mm or larger, which are typically used in commercial silicon foundries, remains difficult. The back-end-of-line (BEOL) integration of directly grown 2D materials on silicon complementary metal–oxide–semiconductor (CMOS) circuits is also unavailable due to the high thermal budget required, which far exceeds the limits of silicon BEOL integration (<400 °C). This high temperature forces the use of challenging transfer processes, which tend to introduce defects and contamination to both the 2D materials and the BEOL circuits. Here we report a low-thermal-budget synthesis method (growth temperature < 300 °C, growth time ≤ 60 min) for monolayer MoS 2 films, which enables the 2D material to be synthesized at a temperature below the precursor decomposition temperature and grown directly on silicon CMOS circuits without requiring any transfer process. We designed a metal–organic chemical vapour deposition reactor to separate the low-temperature growth region from the high-temperature chalcogenide-precursor-decomposition region. We obtain monolayer MoS 2 with electrical uniformity on 200 mm wafers, as well as a high material quality with an electron mobility of ~35.9 cm 2 V -1 s -1 . Finally, we demonstrate a silicon-CMOS-compatible BEOL fabrication process flow for MoS 2 transistors; the performance of these silicon devices shows negligible degradation (current variation < 0.5%, threshold voltage shift < 20 mV). We believe that this is an important step towards monolithic 3D integration for future electronics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Preactivated zeolite nanosheet plate-tiled membrane on porous PVDF film: Synthesis and study of proton-selective ion conduction

Preactivated MFI zeolite nanosheet plates (ZNPs) with large areas (~2.0 × 2.0 μm 2 ) and nanometer thicknesses (~60 nm) were prepared directly in liquid-dispersed state. The individual ZNP was a stack of 4-nm-thick single crystalline zeolite nanosheets (ZNs) interlinked by Si–O–Si bonds between neighboring ZN surfaces. The dispersed open-pore ZNPs allowed formulating suspensions for tiling ZNP membranes on polymer substrates without requiring post-coating activation. A pinhole-free ZNP-tiled (ZNPT) membrane has been achieved on macroporous PVDF film by a self-repairing vacuum-assisted filtration coating method. The resultant ZNPT layer was ~500 nm-thick consisting of about 7 ZNP layers with inter-ZNP width and inter-ZNP entrance porosity around 9 nm and 2%, respectively. The ZNPT-PVDF membrane exhibited high selectivity to proton transport over vanadyl ion and low resistances to proton conduction in aqueous solutions. The membrane also demonstrated to function as an efficient ion separator for the vanadium redox flow battery. The reported synthesis of preactivated ZNP suspension may overcome the major hurdle to realizing polymer-supported ZN membranes, which is the inefficiency of existing methods in obtaining readily dispersible open-pore ZNs. Finally, the ZNPT-PVDF membrane can be a more affordable and sustainable alternative to the Nafion-based ion separation membranes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Non-Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

Porous carbonaceous electrodes are performance-defining components in redox flow batteries (RFBs), where their properties impact the efficiency, cost, and durability of the system. The overarching challenge is to simultaneously fulfill multiple seemingly contradictory requirements—i.e., high surface area, low pressure drop, and facile mass transport—without sacrificing scalability or manufacturability. Here, non-solvent induced phase separation (NIPS) is proposed as a versatile method to synthesize tunable porous structures suitable for use as RFB electrodes. The variation of the relative concentration of scaffold-forming polyacrylonitrile to pore-forming poly(vinylpyrrolidone) is demonstrated to result in electrodes with distinct microstructure and porosity. Tomographic microscopy, porosimetry, and spectroscopy are used to characterize the 3D structure and surface chemistry. Flow cell studies with two common redox species (i.e., all-vanadium and Fe2+/3+) reveal that the novel electrodes can outperform traditional carbon fiber electrodes. It is posited that the bimodal porous structure, with interconnected large (>50 µm) macrovoids in the through-plane direction and smaller (<5 µm) pores throughout, provides a favorable balance between offsetting traits. Although nascent, the NIPS synthesis approach has the potential to serve as a technology platform for the development of porous electrodes specifically designed to enable electrochemical flow technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Accelerated carbonation and structural transformation of blast furnace slag by mechanochemical alkali-activation

Alternative cements and production routes are necessary to offset the considerable global CO 2 emissions of Portland cement production. The combination of alkali-activation and mechanochemical milling in a CO 2 rich atmosphere is a promising green direction for synthesizing cementitious material as it upcycles hazardous material (slag) while capturing wt% of CO 2 during synthesis. We investigate the resulting structural transformations incurred during synthesis and hydration using a suite of characterization techniques including solid-state 27 Al, 29 Si, and 13 C NMR. The local aluminosilicate network structure of the processed clinker is best described by a melilite-type structure. Upon hydration, the network polymerizes to form a calcium, sodium aluminosilicate hydrate gel. The synthesis route also creates various metastable carbonates and bicarbonates from captured CO 2 and alkali-additives that transform into stable carbonate phases like calcite, aragonite, and gaylussite, after hydration. These findings indicate accelerated carbonation reactions occur during clinker production and demonstrates novelty as a green cement technology.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Structural Characterization of the Platinum Nanoparticle Hydrogen-Evolving Catalyst Assembled on Photosystem I by Light-Driven Chemistry

Directed assembly of abiotic catalysts onto biological redox protein frameworks is of interest as an approach for the synthesis of biohybrid catalysts that combine features of both synthetic and biological materials. In this report, we provide a multiscale characterization of the platinum nanoparticle (NP) hydrogen-evolving catalysts that are assembled by light-driven reductive precipitation of platinum from an aqueous salt solution onto the photosystem I protein (PSI), isolated from cyanobacteria as trimeric PSI. The resulting PSI-NP assemblies were analyzed using a combination of X-ray energy-dispersive spectroscopy (XEDS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), small-angle X-ray scattering (SAXS), and high-energy X-ray scattering with atomic pair distribution function (PDF) analyses. The results show that the PSI-supported NPs are approximately 1.8 nm diameter disk-shaped particles that assemble at discrete sites with 145 Å separation. This separation is too large to be consistent with NP nucleation and growth at a site adjacent to the F B cofactor site. Instead, we suggest a mechanism for NP growth at hydrophobic sites on the PSI stromal surface. The NPs photoreductively assembled on the PSI stromal surface are found to be analogous to the nanostructures produced by successive cycles of atomic layer deposition (ALD) of platinum onto 40 nm porous anodic alumina oxide supports, although the mechanisms for nucleation appear to differ. In conclusion, this work establishes a foundation for the investigation of the reductive assembly of abiotic metal catalysts at sites connected to photochemically reducing equivalent production in PSI.

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

A Coupled Mathematical Model of the Intracellular Replication of Dengue Virus and the Host Cell Immune Response to Infection

Dengue virus (DV) is a positive-strand RNA virus of the Flavivirus genus. It is one of the most prevalent mosquito-borne viruses, infecting globally 390 million individuals per year. The clinical spectrum of DV infection ranges from an asymptomatic course to severe complications such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), the latter because of severe plasma leakage. Given that the outcome of infection is likely determined by the kinetics of viral replication and the antiviral host cell immune response (HIR) it is of importance to understand the interaction between these two parameters. In this study, we use mathematical modeling to characterize and understand the complex interplay between intracellular DV replication and the host cells' defense mechanisms. We first measured viral RNA, viral protein, and virus particle production in Huh7 cells, which exhibit a notoriously weak intrinsic antiviral response. Based on these measurements, we developed a detailed intracellular DV replication model. We then measured replication in IFN competent A549 cells and used this data to couple the replication model with a model describing IFN activation and production of IFN stimulated genes (ISGs), as well as their interplay with DV replication. By comparing the cell line specific DV replication, we found that host factors involved in replication complex formation and virus particle production are crucial for replication efficiency. Regarding possible modes of action of the HIR, our model fits suggest that the HIR mainly affects DV RNA translation initiation, cytosolic DV RNA degradation, and naïve cell infection. We further analyzed the potential of direct acting antiviral drugs targeting different processes of the DV lifecycle in silico and found that targeting RNA synthesis and virus assembly and release are the most promising anti-DV drug targets.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Direct Optical Lithography of Colloidal Metal Oxide Nanomaterials for Diffractive Optical Elements with 2π Phase Control

Spatially patterned dielectric materials are ubiquitous in electronic, photonic, and optoelectronic devices. These patterns are typically made by subtractive or additive approaches utilizing vapor-phase reagents. On the other hand, recent advances in solution-phase synthesis of oxide nanomaterials have unlocked a materials library with greater compositional, microstructural, and interfacial tunability. However, methods to pattern and integrate these nanomaterials in real-world devices are less established. In this work, we directly optically pattern oxide nanoparticles (NPs) by mixing them with photosensitive diazo-2-naphthol-4-sulfonic acid and irradiating with widely available 405 nm light. We demonstrate the direct optical lithography of ZrO 2 , TiO 2 , HfO 2 , and ITO NPs and investigate the chemical and physical changes responsible for this photoinduced decrease in solubility. Micron-thick layers of amorphous ZrO 2 NPs were patterned with micron resolution and shown to allow 2 pi phase control of visible light. We also show multilayer patterning and use it to fabricate features with different thicknesses and distinct structural colors. Upon annealing at 400 degrees C, the deposited ZrO 2 structures have excellent optical transparency across a wide wavelength range (0.3-10 mu m), a high refractive index (n = 1.84 at 633 nm), and are optically smooth. We then fabricate diffractive optical elements, such as binary phase diffraction gratings, that show efficient diffractive behavior and good thermal stability. Different oxide NPs can also be mixed prior to patterning, providing a high level of material tunability. This work demonstrates a general patterning approach that harnesses the processability and diversity of colloidal oxide nanomaterials for use in photonic applications.

2𝜋 phase shift↗
DOE OSTI2021

Fischer-Tropsch Synthesis: The Characterization and Testing of Pt-Co/SiO 2 Catalysts Prepared with Alternative Cobalt Precursors

Different low-cost cobalt precursors (acetate, chloride) and thermal treatments (air calcination/H 2 reduction versus direct H 2 -activation) were investigated to alter the interaction between cobalt and silica. H 2 -activated catalysts prepared from cobalt chloride had large Co 0 particles (XRD, chemisorption) formed by weak interactions between cobalt chloride and silica (temperature programmed reduction (TPR), TPR with mass spectrometry (TPR-MS), TPR with extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES) techniques) and retained Cl-blocked active sites, resulting in poor activity. In contrast, unpromoted Co/SiO 2 catalysts derived from cobalt acetate had strong interactions between Co species and silica (TPR/TPR-MS, TPR-EXAFS/XANES); adding Pt increased the extent of the Co reduction. For these Pt-promoted catalysts, the reduction of uncalcined catalysts was faster, resulting in larger Co 0 clusters (19.5 nm) in comparison with the air-calcined/H 2 -activated catalyst (7.8 nm). Both catalysts had CO conversions 25% higher than that of the Pt-promoted catalyst prepared in the traditional manner (air calcination/H 2 reduction using cobalt nitrate) and three times higher than that of the traditional unpromoted Co/silica catalyst. The retention of residual cobalt carbide (observed in XANES) from cobalt acetate decomposition impacted performance, resulting in a higher C 1 –C 4 selectivity (32.2% for air-calcined and 38.7% for uncalcined) than that of traditional catalysts (17.5–18.6%). The residual carbide also lowered the α-value and olefin/paraffin ratio. Future work will focus on improving selectivity through oxidation–reduction cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Towards Low-Temperature CVD Synthesis and Characterization of Mono- or Few-Layer Molybdenum Disulfide

Molybdenum disulfide (MoS 2 ) transistors are a promising alternative for the semiconductor industry due to their large on/off current ratio (>10 10 ), immunity to short-channel effects, and unique switching characteristics. MoS 2 has drawn considerable interest due to its intriguing electrical, optical, sensing, and catalytic properties. Monolayer MoS 2 is a semiconducting material with a direct band gap of ~1.9 eV, which can be tuned. Commercially, the aim of synthesizing a novel material is to grow high-quality samples over a large area and at a low cost. Although chemical vapor deposition (CVD) growth techniques are associated with a low-cost pathway and large-area material growth, a drawback concerns meeting the high crystalline quality required for nanoelectronic and optoelectronic applications. This research presents a lower-temperature CVD for the repeatable synthesis of large-size mono- or few-layer MoS 2 using the direct vapor phase sulfurization of MoO 3 . The samples grown on Si/SiO 2 substrates demonstrate a uniform single-crystalline quality in Raman spectroscopy, photoluminescence (PL), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy. These characterization techniques were targeted to confirm the uniform thickness, stoichiometry, and lattice spacing of the MoS 2 layers. The MoS 2 crystals were deposited over the entire surface of the sample substrate. With a detailed discussion of the CVD setup and an explanation of the process parameters that influence nucleation and growth, this work opens a new platform for the repeatable synthesis of highly crystalline mono- or few-layer MoS 2 suitable for optoelectronic application.

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

Online Bayesian State Estimation for Real-Time Monitoring of Growth Kinetics in Thin Film Synthesis

Rapid validation of newly predicted materials through autonomous synthesis requires real-time adaptive control methods that exploit physics knowledge, a capability that is lacking in most systems. Here, in this study, we demonstrate an approach to enable real-time control of thin film synthesis by combining in situ optical diagnostics with a Bayesian state estimation method. We developed a physical model for film growth and applied the direct filter (DF) method for real-time estimation of nucleation and growth rates during pulsed laser deposition (PLD). We validated the approach using simulated and experimental reflectivity data for WSe 2 growth and ultimately deployed the algorithm on an autonomous PLD system during the growth of 1T'-MoTe 2 . The DF robustly estimates growth parameters in real time at early stages of growth, down to 15% monolayer area coverage. This fusion of in situ diagnostics, data assimilation, and physical modeling opens new opportunities in adaptive control of synthesis trajectories toward desired material states.

36 MATERIALS SCIENCE↗
DOE OSTI2021

S ‐Adenosyl‐ l ‐ethionine is a Catalytically Competent Analog of S ‐Adenosyl‐ l ‐methionine (SAM) in the Radical SAM Enzyme HydG

Abstract Radical S ‐adenosyl‐ l ‐methionine (SAM) enzymes initiate biological radical reactions with the 5′‐deoxyadenosyl radical (5′‐dAdo . ). A [4Fe‐4S] + cluster reductively cleaves SAM to form the Ω organometallic intermediate in which the 5′‐deoxyadenosyl moiety is directly bound to the unique iron of the [4Fe‐4S] cluster, with subsequent liberation of 5′‐dAdo . . We present synthesis of the SAM analog S ‐adenosyl‐ l ‐ethionine (SAE) and show SAE is a mechanistically equivalent SAM‐alternative for HydG, both supporting enzymatic turnover of substrate tyrosine and forming the organometallic intermediate Ω. Photolysis of SAE‐bound HydG forms an ethyl radical trapped in the active site. The ethyl radical withstands prolonged storage at 77 K and its EPR signal is only partially lost upon annealing at 100 K, making it significantly less reactive than the methyl radical formed by SAM photolysis. Upon annealing above 77 K, the ethyl radical adds to the [4Fe‐4S] 2+ cluster, generating an ethyl‐[4Fe‐4S] 3+ organometallic species termed Ω E .

Impano, Stella↗