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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Prussian blue as a co-catalyst for enhanced Cr (VI) photocatalytic reduction promoted by titania-based nanoparticles and aerogels

Hexavalent chromium (Cr(VI)) is an noxious and highly toxic heavy metal that presents a serious threat to human health if present even in low concentrations in drinking water. Photocatalytic reduction of Cr(VI) to its less toxic Cr(III) state is a potential strategy to combat Cr(VI) pollution, but the efficiency of the process is low, especially in the absence of hole scavenger organic reagents. To address this issue and prepare efficient photocatalysts for Cr(VI) removal from water, in this study, we explored Prussian blue (PB) as a co-catalyst for improving the photoreduction performance of different high surface area TiO 2 -based materials (titania or silica–titania nanoparticles and aerogels). Here, the photocatalyst nanomaterials were surface-modified with nanocrystalline PB using the photodeposition route. The PB layer acts as an effective electron acceptor/mediator between the semiconductor photocatalyst and Cr(VI) species. All the PB-modified photocatalysts exhibit higher photocatalytic activity (up to 9 times faster) as compared to the unmodified photocatalysts towards reduction of Cr(VI). Importantly, the PB-modified photocatalysts exhibited high photocatalytic performance (98–99% reduction in 40 min for pH = 5.6 and in 10 min for pH = 3) without addition of organic reagents. The simple approach reported herein can be followed to prepare new PB-photocatalyst systems with improved photocatalytic performance towards Cr(VI) reduction and other target applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Pressure-stimulus-responsive behaviors of core–shell InP/ZnSe nanocrystals: remarkable piezochromic luminescence and structural assembly

Piezochromic luminescence materials with optical properties can be adjusted (the colors most sensitive to the human eye range from red to green) to provide powerful means for information acquisition in various applications. Inorganic quantum dots, typically based on heavy metals such as cadmium and lead, have congenital advantages as luminescence materials, including strong inoxidizability and excellent photoelectric properties. However, small band-gap shifts under pressure have hindered the development of inorganic-based piezochromic materials. In this study, we combined in situ high-pressure photoluminescence (PL) and absorption measurements with synchrotron X-ray scattering spectra to elucidate the remarkable modulation of optical properties and morphologies by pressure, particularly that of the piezochromic luminescence, in all-inorganic core–shell InP/ZnSe nanocrystals (NCs). We observed a stepwise PL color change from red to green, and an ultrabroad bandgap tunability of 0.46 eV was observed from 1.99 to 2.45 eV in the pressure range of 14.2 GPa for InP/ZnSe NCs. Moreover, two-dimensional (2D) InP/ZnSe nanosheets were synthesized by the stress-driven attachment of nanoparticles. These results demonstrate the ability of the pressure-stimulus response to trigger remarkable piezochromic luminescence and 2D nanosheet assembly in InP/ZnSe NCs, which paves the way for new applications of all-inorganic InP-based semiconductor NCs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Enriching 2D transition metal borides via MB XMenes (M = Fe, Co, Ir): Strong correlation and magnetism

Recently, two-dimensional (2D) FeSe-like anti-MXenes (or XMenes), composed of late d-block transition metal M and p-block nonmetal X elements, have been both experimentally and theoretically investigated. Here, we select three 2D borides FeB, CoB and IrB for a deeper investigation by including strong correlation effects, as a fertile ground for understanding and applications. Using a combination of Hubbard corrected first-principles calculations and Monte Carlo simulations, FeB and CoB are found to be ferro- and anti-ferro magnetic, contrasting with the non-magnetic nature of IrB. The metallic FeB XMene monolayer, superior to most of the MXenes or MBenes, exhibits robust ferromagnetism, driven by intertwined direct-exchange and super-exchange interactions between adjacent Fe atoms. The predicted Curie temperature ($T$ C ) of the FeB monolayer via the Heisenberg model reaches an impressive 425 K, with the easy-axis oriented out-of-plane and high magnetic anisotropic energy (MAE). The asymmetry in the spin-resolved transmission spectrum induces a thermal spin current, providing an opportunity for spin filtration. In conclusion, this novel 2D FeB material is expected to hold great promise as an information storage medium and find applications in emerging spintronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Granular metals with SiN x dielectrics

Understanding and controlling nanoscale interface phenomena, such as band bending and secondary phase formation, is crucial for electronic device optimization. In granular metal (GM) studies, where metal nanoparticles are embedded in an insulating matrix, the importance of interface phenomena is frequently neglected. Here, we demonstrate that GMs can serve as an exemplar system for evaluating the role of secondary phases at interfaces through a combination of x-ray photoemission spectroscopy (XPS) and electrical transport studies. We investigated SiN x as an alternative to more commonly used oxide-insulators, as SiN x -based GMs may enable high temperature applications when paired with refractory metals. Comparing Co-SiN x and Mo-SiN x GMs, we found that, in the tunneling-dominated insulating regime, Mo-SiN x had reduced metal-silicide formation and orders-of-magnitude lower conductivity. XPS measurements indicate that metal-silicide and metal-nitride formation are mitigatable concerns in Mo-SiN x . Given the metal-oxide formation seen in other GMs, SiN x is an appealing alternative for metals that readily oxidize. Furthermore, SiN x provides a path to metal-nitride nanostructures, potentially useful for various applications in plasmonics, optics, and sensing.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Semiconductor Nanostructures by Scientific Design (Final Technical Report)

We developed and used quantum simulation techniques to predict structural, electronic, optical and thermal properties affecting the scientific design of semiconductor nanostructures. We focused on the study of surfaces and interfaces at the nanoscale, in particular embedding and solvation of semiconductor nanoparticles, and provided a microscopic description of nanostructured materials in realistic environments, directly comparable with experimental conditions. We addressed three major problems: (i) the design of realistic structural models of integrated nanostructures, e.g. quantum dots embedded in solid matrices and nanostructures immersed in fluids; (ii) the development of efficient and accurate calculations to describe the excited state properties of nanostructures, beyond standard Density Functional Theory, so as to understand and predict electronic properties involved in renewable energy applications, for example solar conversion devices. In particular we developed and used methods based on a many body perturbation theory. (iii) the development of calculations of heat transport properties of nanostructured materials, for thermoelectric applications, including predictive calculations of thermal and electrical conductivity and of Seebeck coefficients. Specifically, we developed and used methods based on the Boltzmann transport equation and molecular dynamics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Multiport High-pressure Fluid Cell (MHPFC) for Photon and Electron Beams

A multiport high-pressure fluid cell was developed based on an engineered thin film membrane solution with a reinforced frame of boron-doped silicon, optimized to withstand better pressure with an increase of 17.6% in average burst pressure over similar membranes without frame. The novel cells (patent pending) have 8 microfluidic ports, two intra-cavity electrodes and two pressure sensors on a 8 mm x 8 mm Si chip. The prototypes resisted up to 60 bar with 50-nm-thick silicon nitride membranes of size 70 nm x 70 nm. The cells can be used for testing reactions in fluids in medium-high pressure (up to 300 bar) using X-rays (primary application), electron beams, IR or visible light. Improvements in the pressure sensing setup and customization for applications are supposed to follow.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nanocrystalline Materials: Synthesis, Characterization, Properties, and Applications

Nanostructuring is a commonly employed method of obtaining superior mechanical properties in metals and alloys. Compared to conventional polycrystalline counterparts, nanostructuring can provide remarkable improvements in yield strength, toughness, fatigue life, corrosion resistance, and hardness, which is attributed to the nano grain size. In this review paper, the current state-of-the-art of synthesis methods of nanocrystalline (NC) materials such as rapid solidification, chemical precipitation, chemical vapor deposition, and mechanical alloying, including high-energy ball milling (HEBM) and cryomilling was elucidated. More specifically, the effect of various process parameters on mechanical properties and microstructural features were explained for a broad range of engineering materials. This study also explains the mechanism of grain strengthening using the Hall-Petch relation and illustrates the effects of post-processing on the grain size and subsequently their properties. This review also reports the applications, challenges, and future scope for the NC materials.

36 MATERIALS SCIENCE↗
NASA NTRS2011

Application of Emerging Pharmaceutical Technologies for Therapeutic Challenges of Space Exploration Missions

An important requirement of therapeutics for extended duration exploration missions beyond low Earth orbit will be the development of pharmaceutical technologies suitable for sustained and preventive health care in remote and adverse environmental conditions. Availability of sustained, stable and targeted delivery pharmaceuticals for preventive health of major organ systems including gastrointestinal, hepato-renal, musculo-skeletal and immune function are essential to offset adverse effects of space environment beyond low Earth orbit. Specifically, medical needs may include multi-drug combinations for hormone replacement, radiation protection, immune enhancement and organ function restoration. Additionally, extended stability of pharmaceuticals dispensed in space must be also considered in future drug development. Emerging technologies that can deliver stable and multi-therapy pharmaceutical preparations and delivery systems include nanotechnology based drug delivery platforms, targeted-delivery systems in non-oral and non-parenteral formulation matrices. Synthetic nanomaterials designed with molecular precision offer defined structures, electronics, and chemistries to be efficient drug carriers with clear advantages over conventional materials of drug delivery matricies. Nano-carrier materials like the bottle brush polymers may be suitable for systemic delivery of drug cocktails while Superparamagnetic Iron Oxide Nanoparticles or (SPIONS) have great potential to serve as carriers for targeted drug delivery to a specific site. These and other emerging concepts of drug delivery and extended shelf-life technologies will be reviewed in light of their application to address health-care challenges of exploration missions. Innovations in alternate treatments for sustained immune enhancement and infection control will be also discussed.

Putcha, Lakshmi↗
DOE OSTI2021

Snapshots of Ce 70 Toroid Assembly from Solids and Solution

Crystallization at the solid–liquid interface is difficult to spectroscopically observe and therefore challenging to understand and ultimately control at the molecular level. The Ce70-torroid formulated [Ce IV 70 (OH) 36 (O) 64 (SO 4 ) 60 (H 2 O) 10 ] 4– , part of a larger emerging family of M IV 70 -materials (M = Zr, U, Ce), presents such an opportunity. We elucidated assembly mechanisms by the X-ray scattering (small-angle scattering and total scattering) of solutions and solids as well as crystallizing and identifying fragments of Ce 70 by single-crystal X-ray diffraction. Fragments show evidence for templated growth (Ce 5 , [Ce 5 (O) 3 (SO 4 ) 12 ] 10- ) and modular assembly from hexamer (Ce 6 ) building units (Ce 13 , [Ce 13 (OH) 6 (O) 12 (SO 4 ) 14 (H 2 O) 14 ] 6– and Ce 62 , [Ce 62 (OH) 30 (O) 58 (SO 4 ) 58 ] 14- ). Ce 62 , an almost complete ring, precipitates instantaneously in the presence of ammonium cations as two torqued arcs that interlock by hydrogen boding through NH 4 + , a structural motif not observed before in inorganic systems. The room temperature rapid assemblies of both Ce 70 and Ce 62 , respectively, by the addition of Li + and NH 4 + , along with ion-exchange and redox behavior, invite exploitation of this emerging material family in environmental and energy applications.

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

Imaging how thermal capillary waves and anisotropic interfacial stiffness shape nanoparticle supracrystals

Abstract Development of the surface morphology and shape of crystalline nanostructures governs the functionality of various materials, ranging from phonon transport to biocompatibility. However, the kinetic pathways, following which such development occurs, have been largely unexplored due to the lack of real-space imaging at single particle resolution. Here, we use colloidal nanoparticles assembling into supracrystals as a model system, and pinpoint the key role of surface fluctuation in shaping supracrystals. Utilizing liquid-phase transmission electron microscopy, we map the spatiotemporal surface profiles of supracrystals, which follow a capillary wave theory. Based on this theory, we measure otherwise elusive interfacial properties such as interfacial stiffness and mobility, the former of which demonstrates a remarkable dependence on the exposed facet of the supracrystal. The facet of lower surface energy is favored, consistent with the Wulff construction rule. Our imaging–analysis framework can be applicable to other phenomena, such as electrodeposition, nucleation, and membrane deformation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Mechanics of Dynamic and Deformable DNA Nanostructures

In DNA nanotechnology, DNA molecules are designed, engineered, and assembled into arbitrary-shaped architectures with predesigned functions. Static DNA assemblies often have delicate designs with structural rigidity to overcome thermal fluctuations. Dynamic structures reconfigure in response to external cues, which have been explored to create functional nanodevices for environmental sensing and other applications. However, the precise control of reconfiguration dynamics has been a challenge due partly to flexible single-stranded DNA connections between moving parts. Deformable structures are special dynamic constructs with deformation on double-stranded parts and single-stranded hinges during transformation. These structures often have better control in programmed deformation. However, related deformability and mechanics including transformation mechanisms are not well understood or documented. In this review, we summarize the development of dynamic and deformable DNA nanostructures from a mechanical perspective. We present deformation mechanisms such as single-stranded DNA hinges with lock-and-release pairs, jack edges, helicity modulation, and external loading. Theoretical and computational models are discussed for understanding their associated deformations and mechanics. We elucidate the pros and cons of each model and recommend design processes based on the models. The design guidelines should be useful for those who have limited knowledge in mechanics as well as expert DNA designers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Kalman Filter Based Estimation of Surface Conductivity in STM

In scanning tunneling microscopy (STM), the surface conductivity, σ, contributes to the total tunneling current due to a quantum phenomenon. Here, the surface conductivity may change from atom to atom during a scan. It is an important electronic property of the surface that cannot be directly measured with current spectroscopy methods. In this paper, we propose an offline estimation method based on augmented state Kalman filter to determine σ. We demonstrate the successful application of this method to a set of STM images obtained from a Si(100) – 2 × 1:H passivated surface.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Atoms to fibers: Identifying novel processing methods in the synthesis of pitch-based carbon fibers

Understanding and optimizing the key mechanisms used in the synthesis of pitch-based carbon fibers (CFs) are challenging, because unlike polyacrylonitrile-based CFs, the feedstock for pitch-based CFs is chemically hetero- geneous, resulting in complex fabrication leading to inconsistency in the final properties. In this work, we use molecular dynamics simulations to explore the processing and chemical phase space through a framework of CF models to identify their effects on elastic performance. The results are in excellent agreement with experiments. We find that density, followed by alignment, and functionality of the molecular constituents dictate the CF mechanical properties more strongly than their size and shape. Last, we propose a previously unexplored fabrication route for high-modulus CFs. Unlike graphitization, this results in increased sp 3 fraction, achieved via generating high-density CFs. In addition, the high sp 3 fraction leads to the fabrication of CFs with isometric compressive and tensile moduli, enabling their potential applications for compressive loading.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2024

DNA Origami Incorporated into Solid-State Nanopores Enables Enhanced Sensitivity for Precise Analysis of Protein Translocations

The rapidly advancing field of nanotechnology is driving the development of precise sensing methods at the nanoscale, with solid-state nanopores emerging as promising tools for biomolecular sensing. Here, this study investigates the increased sensitivity of solid-state nanopores achieved by integrating DNA origami structures, leading to the improved analysis of protein translocations. Using holo human serum transferrin (holo-hSTf) as a model protein, we compared hybrid nanopores incorporating DNA origami with open solid-state nanopores. Results show a significant enhancement in holo-hSTf detection sensitivity with DNA origami integration, suggesting a unique role of DNA interactions beyond confinement. This approach holds potential for ultrasensitive protein detection in biosensing applications, offering advancements in biomedical research and diagnostic tool development for diseases with low-abundance protein biomarkers. Further exploration of origami designs and nanopore configurations promises even greater sensitivity and versatility in the detection of a wider range of proteins, paving the way for advanced biosensing technologies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Controlling quantum phases of electrons and excitons in moiré superlattices

Moiré lattices formed in twisted and lattice-mismatched van der Waals heterostructures have emerged as a platform to engineer the novel electronic and excitonic states at the nanoscale. This Perspective reviews the materials science of moiré heterostructures with a focus on the structural properties of the interface and its structural–property relationships. We first review the studies of the atomic relaxation and domain structures in moiré superlattices and how these structural studies provide critical insights into understanding the behaviors of quantum-confined electrons and excitons. We discuss the general frameworks to manipulate moiré structures and how such control can be harnessed for engineering new phases of matter and simulating various quantum phenomena. Lastly, we discuss routes toward large-scale moiré heterostructures and give an outlook on their applications in quantum electronics and optoelectronics. Special emphasis will be placed on the challenges and opportunities of the reliable fabrication and dynamical manipulation of moiré heterostructures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

The Stability of SiO{sub 2} Fe{sub 3}O{sub 4} Nanoparticles for Uranium Extraction in Acidic Media - 20189

This comprehensive study has shown that the proposed strategy of SiO{sub 2} coating of Fe{sub 3}O{sub 4} nanoparticles (NPs) for the use of uranium (U) extraction in acidic media was successful. The breakdown of Fe{sub 3}O{sub 4} in acidic media has proven to be a challenge when applying to a nuclear waste removal scenario, leading to the dissolution of Fe{sub 3}O{sub 4} and preventing uptake of U ions in the waste. To overcome this a SiO{sub 2} passivating layer was grafted to the Fe{sub 3}O{sub 4} NPs, to which an acid stability test was conducted between pH 3 and pH 4. It has been shown via Transmission Electron Microscopy (TEM) and zeta potential measurements that the uncoated Fe{sub 3}O{sub 4} NPs exhibit rapid coagulation when exposed to acidic conditions, moving from a stable zeta potential of -44 mV to an unstable zeta potential of +6 mV. SiO{sub 2} coated Fe{sub 3}O{sub 4} on the other hand can remain stable for several hours and continue to be stable beyond that. Throughout acid exposure the zeta potential of these NPs remained at ∼ -38 mV, showing great stability. As a functionality is needed on the surface of the NPs for separation and extraction, the phosphate complex used was also tested for its acid stability. It was determined that with a constant zeta potential of ∼ -20 mV, the phosphate functionality was able to remain stable in the acidic conditions simulating the environment of certain nuclear wastes. Overall SiO{sub 2} coated (PO)x-Fe{sub 3}O{sub 4} NPs show great promise for application in separation and removal of U in acid media. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Chapter 3: Nanostructured Iron Oxide Hybrid Composites as Heterogeneous Fenton-Like Catalyst for Remediation of Persistent Organic Pollutants

In water purification research and technologies, heterogeneous Fenton catalysts are evolving as an excellent material recently. A summary of present research on heterogeneous Fenton/Fenton-like processes is essential for developing novel and high-efficiency organic wastewater treatment methods. In this chapter, we discussed the basics of Fenton reactions taking the example of iron oxides and their different composites, such as bimetallic composites, composites with carbon compounds, and Fe metal-organic frameworks (MOFs). The important operating parameters (solution pH, H 2 O 2 dosage, amount of catalyst used, and reaction temperature) in heterogeneous Fenton-like reactions are discussed. Strategies to increase the rate and activities of heterogeneous Fenton catalysts by using energy sources are presented. The mechanistic aspects of heterogeneous Fenton processes and reusability of catalysts along with their application in real wastewater plants are summarized and discussed. Finally, we concluded with the scope and future prospects of heterogeneous Fenton catalysis research to motivate the readers to construct novel and efficient heterogeneous Fenton/Fenton-like systems for industrial applications.

carbon composites↗
DOE OSTI2024

Formation of tunable diamond micro- and nanopillars for field effect enhancement applications

Here, we developed a process for the fabrication of tunable single crystal diamond micro- and nanopillars, with tip widths ranging from 40 to 460 nm, densities ranging from 0.5 to 53.5 pillars/μm 2 , and heights greater than 4.5 μm. A self-assembled Au nanodot ensemble etch mask was formed from an annealed Au thin film. The nanodot diameter and density can be tuned using the initial film thickness. The pillars were etched from the nanodot mask using an RIE O 2 plasma, which has infinite selectivity for the diamond when applied at low RF powers (50 W). Finally, the pillars can be sharpened to ~40 nm tip widths by annealing in air at 650 °C. These pillars can be used for applications such as field effect enhancement of diamond photocathode devices, enhancement of optical emission from N-V centers, and antireflective coatings.

36 MATERIALS SCIENCE↗