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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Nanostructured layer for graded index freeform optics

The present disclosure relates to a method for creating an optical component having a spatially controlled refractive index. The method may involve applying a thin metal material layer to a substrate. The thin metal material layer may then be heated to create a mask having a spatially varying nano-particle distribution. The substrate may then be etched, using the mask, to imprint a spatially patterned nanostructure pattern on a surface the substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nanostructured catalyst supports

The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Nanostructured polyelectrolytes for ion-selective membranes

Nanostructured polyelectrolyte bilayers deposited by Layer-by-Layer deposition on nanoporous membranes can be selectively crosslinked to modify the polyelectrolyte charge density and control ionic selectivity independent of ionic conductivity. For example, the polyelectrolyte bilayer can comprise a cationic polymer layer, such as poly(ethyleneimine), and an anionic polymer layer, such as poly(acrylic acid). Increasing the number of bilayers increases the cation selectivity when the poly(ethyleneimine) layer is crosslinked with glutaraldehyde. Crosslinking the membranes also increases the chemical and mechanical strength of the polyelectrolyte films. This controllable and inexpensive method can be used to create ion-selective and mechanically robust membranes on porous supports for a wide range of applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Arrays of high-aspect-ratio germanium nanostructures with nanoscale pitch and methods for the fabrication thereof

Methods for fabricating thin, high-aspect-ratio Ge nanostructures from high-quality, single-crystalline Ge substrates are provided. Also provided are grating structures made using the methods. The methods utilize a thin layer of graphene between a surface of a Ge substrate, and an overlying resist layer. The graphene passivates the surface, preventing the formation of water-soluble native Ge oxides that can result in the lift-off of the resist during the development of the resist.

Lagally, Max G.↗
DOE OSTI2021

Nanostructured mixed metal oxides as catalysts and method of making thereof

A method of forming a metal oxide material having a rod shape or polyhedral nanostructure includes preparing a first reverse micro-emulsion system comprising an aqueous precipitating agent dispersion and a second reverse micro-emulsion system containing an aqueous metal salt dispersion; combining the micro-emulsions together to initiate a reaction; allowing the reaction to continue to form a product mixture comprising a metal oxide gel and aqueous media; separating the metal oxide gel from the aqueous media; collecting the metal oxide gel; and calcining the metal oxide gel to form the metal oxide material. The metal oxide material corresponds to the chemical formula of La2MxNi1-xO4, Pr2-yAyNiO4, or La2-zDzNiO4, wherein M is copper, cobalt, iron, manganese, chromium, aluminum, or platinum; A is lanthanum or neodymium; D is calcium, barium or strontium; x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

Nikolla, Eranda↗
DOE OSTI2020

Strain-Enhanced Metallic Intermixing in Shape-Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanoparticles tailored to each potential application.

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

Ti‐Modified Imogolite Nanotubes as Promising Photocatalyst 1D Nanostructures for H 2 Production

Imogolite nanotubes (INTs) are predicted as a unique 1D material with spatial separation of conduction and valence band edges but their large band gaps have inhibited their use as photocatalysts. The first step toward using these NTs in photocatalysis and exploiting the polarization-promoted charge separation across their walls is to reduce their band gap. Here, the modification of double-walled aluminogermanate INTs by incorporation of titanium into the NT walls is explored. The precursor ratio x = [Ti]/([Ge]+[Ti]) is modulated between 0 and 1. Structural and optical properties are determined at different scales and the photocatalytic performance is evaluated for H 2 production. Although the incorporation of Ti atoms into the structure remains limited, the optimal condition is found around x = 0.4 for which the resulting NTs reveal a remarkable hydrogen production of ≈1500 µmol g −1 after 5 h for a noble metal-free photocatalyst, a 65-fold increase relative to a commercial TiO 2 -P25. This is correlated to a lowering of the recombination rate of photogenerated charge carriers for the most active structures. These results confirm the theoretical predictions regarding the potential of modified INTs as photoactive nanoreactors and pave the way for investigating and exploiting their polarization properties for energy applications.

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

Hot Electron Driven Photocatalysis on Plasmon-Resonant Grating Nanostructures

Here, we demonstrate the hot electron injection of photoexcited carriers in an Ag-based plasmon resonant grating structure. By varying the incident angle of irradiation, sharp dips are observed in the reflectance with p-polarized light (electric field perpendicular to grating lines) when there is wavevector matching between the incident light and the plasmon resonant modes of the grating and no angle dependence is observed with s-polarized light. This configuration enables us to compare photoelectrochemical current produced by plasmon resonant excitation with that of bulk metal interband absorption simply by rotating the polarization of the incident light while keeping all other parameters of the measurement fixed. With 633 nm light, we observed a 12-fold enhancement in the photocurrent (i.e., reaction rate) between resonant and nonresonant polarizations at incident angles of ±7.6° from normal. At 785 nm irradiation, we observed similar resonant profiles to those obtained with 633 nm wavelength light but with a 44-fold enhancement factor. Using 532 nm light, we observed two resonant peaks (with approximately 10× enhancement) in the photocurrent at 19.4° and 28.0° incident angles, each corresponding to higher order modes in the grating with more nodes per period. The lower enhancement factors observed at shorter wavelengths are attributed to interband transitions, which provide a damping mechanism for the plasmon resonance. Finite difference time domain (FDTD) simulations of these grating structures confirm the resonant profiles observed in the angle-dependent spectra of these gratings and provide a detailed picture of the electric field profiles on and off resonance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Dynamic evolution of ultracold electron beams from nanostructured cathodes

Dynamic Coulomb expansion of dense, nonuniform particle beamlets can lead to causticlike formations in the charge density profile of the resultant beam. Such features only occur for cold beams where thermal diffusion of the particles is minimized. These phenomena have been observed experimentally for select cases with ion beams but not yet for electron beams as the electron dynamics occur over far faster timescales. We simulate the interaction of electron bunches while varying the initial transverse temperature and density profiles to determine the thresholds that characterize this pattern formation. Furthermore, we extend the simulations to geometric arrangements that are more pertinent to the nanotip cathode application and consider the effects of asymmetries and the impact of a low-density halo on the overall process. The simulations are conducted using a previously documented high-fidelity algorithm for collisional particle dynamics. These studies identify the temperature and density thresholds required for caustic formation and provide guidance for optimizing the design of nanoscale structured cathodes. We also demonstrate that the correlation between the final density patterns and the underlying beam parameters enables a virtual diagnostic tool for measuring ultralow emittance beams solely based on a transverse charge density profile.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Real-time Measurements of Complex Transition Metal Oxide Nanostructure Growth (Year 3 - Final Technical Report-GaTech-MIT)

The project, a collaboration between the Ross Lab at MIT and the Filler Lab at Georgia Tech, aimed to combine in situ microscopy and spectroscopy measurements to answer fundamental questions about the physics and chemistry governing the bottom-up vapor-solid-liquid (VLS) growth of one-dimensional (1-D) functional oxides. This work supported one PhD student and 1 postdoc. One paper has been published and 5 others are in preparation. To date, this work has been presented at 5 conferences.

36 MATERIALS SCIENCE↗