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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Fundamental Study on Temperature Dependence of Deposition Rate of Silicic Acid - 13270

The dynamic behavior of the silicic acid is one of the key factors to estimate the condition of the repository system after the backfill. This study experimentally examined the temperature dependence of dynamic behavior of supersaturated silicic acid in the co-presence of solid phase, considering Na ions around the repository, and evaluated the deposition rate constant, k, of silicic acid by using the first-order reaction equation considering the specific surface area. The values of k were in the range of 1.0x10{sup -11} to 1.0x10{sup -9} m/s in the temperature range of 288 K to 323 K. The deposition rate became larger with increments of temperature under the Na ion free condition. Besides, in the case of Na ions 0.6 M, colloidal silicic acid decreased dramatically at a certain time. This means that the diameter of the colloidal silicic acid became larger than the pore size of filter (0.45 μm) due to bridging of colloidal silicic acid. Furthermore, this study estimated the range of altering area and the aperture of flow-path in various value of k corresponding to temperature by using advection-dispersion model. The concentration in the flow-path became lower with increments of temperature, and when the value of k is larger than 1.0x10{sup -11} m/s, the deposition range of supersaturated silicic acid was estimated to be less than 20 m around the repository. In addition, the deposition of supersaturated silicic acid led the decrement of flow-path aperture, which was remarkable under the condition of relatively high temperature. Such a clogging in flow paths is expected as a retardation effect of radionuclides. (authors)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Tunable Fluorescence from Dye-Modified DNA-Assembled Plasmonic Nanocube Arrays

Colloidal crystal engineering with DNA on template-confined surfaces is used to prepare arrays of nanocube-based plasmonic antennas and deliberately place dyes with sub-nm precision into their hotspots, on the DNA bonds that confine the cubes to the underlying gold substrate. This combined top-down and bottom-up approach provides independent control over both the plasmonic gap and photonic lattice modes of the surface-confined particle assemblies and allows for the tuning of the interactions between the excited dyes and plasmonically active antennas. Furthermore, the gap mode of the antennas can be modified in situ by utilizing the solvent-dependent structure of the DNA bonds. This is studied by placing two dyes, with different emission wavelengths, under the nanocubes and recording their solvent-dependent emission. Furthermore, it is shown that dye emission not only depends upon the in-plane structure of the antennas but also the size of the gap, which is regulated with solvent. Importantly, this approach allows for the systematic understanding of the relationship between nanoscale architecture and plasmonically coupled dye emission, and points toward the use of colloidal crystal engineering with DNA to create stimuli responsive architectures, which can find use in chemical sensing and tunable light sources.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electrical Switching of Nematic Plasmonic Nanocolloids for Infrared Solar Gain Control

Controlling solar gain is essential to reduce the energy consumption by residential and commercial buildings, which are responsible for ≈40% of all energy generated globally. However, the dynamic control of solar gain in the near-infrared that corresponds to ≈50% of the overall Sun's energy at the Earth's surface, separately from the visible spectral range has been a challenge, albeit commercial coatings provide passive control while retaining highly visible transmission. To address this problem, in this paper switchable silver colloids (SSCs) are demonstrated, colloidal analogs of the common silver coatings used for solar gain control. When dispersed in a nematic liquid crystal, orientations of such plasmonic silver nanoplates are controlled by ≈1 V low-voltage electric fields, allowing for sub-second switching of the near-infrared-based solar gain. Installed and retrofit products made from thin films of such nanoplate dispersions confined between glass and plastic substrates, respectively, exhibit electrically controlled infrared-based solar gain while retaining high visible-range transparency, low haze, and high color rendering index. Furthermore, this study's findings reveal a great potential of soft-matter systems in addressing energy-related problems.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Fluctuating Hydrodynamic Methods for Fluid-Structure Interactions in Confined Channel Geometries

Computational methods are developed for the study of fluid-structure interactions subject to thermal fluctuations when conned within channels having slit-like geometry. The methods take into account the hydrodynamic coupling and diusivity of microstructures when influenced by their proximity to no-slip walls. We develop stochastic numerical methods subject to no-slip boundary conditions using a staggered nite volume discretization. We show that by imposing an exact fluctuation-dissipation condition to discretize the stochastic driving elds combined with using an exact projection method to enforce incompressibility is sucient to ensure results consistent with statistical mechanics. We demonstrate our methods by investigating how the proximity of ellipsoidal colloids to the channel wall eects their active hydrodynamic responses and passive diusivity. We also study the collective dynamics of a large number of particles by considering the intermediate scattering functions for the relaxation of density fluctuations. We expect our introduced stochastic computational methods to be applicable broadly to applications in which confinement effects play an important role in the dynamics of microstructures subject to hydrodynamic coupling and thermal fluctuations. uctuations.

Wang, Yaohong↗
DOE OSTI2017

Structure and Properties of Nanoparticles Fabricated by Laser Ablation of Bulk Metal Copper Targets in Water and Ethanol

Colloidal solutions of nanoparticles (NPs) are prepared by nanosecond pulsed laser ablation (upon exposure to Nd:YAG laser radiation at a wavelength of 1064 nm with a pulse duration of 7 ns) of a copper target in water and ethyl alcohol. Their composition, structure, and optical properties are investigated. It is shown that monovalent Cu{sub 2}O NPs are mainly formed in water, whereas metal Cu NPs are mainly formed in ethanol. The nonlinear transmission of colloids at wavelengths of 532 and 1064 nm is investigated. It is established that they effectively limit the nanosecond laser pulse power at a wavelength of 532 nm.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Evaluating the Rheo-electric Performance of Aqueous Suspensions of Oxidized Carbon Black

Here, the macroscopic properties of carbon black suspensions are primarily determined by the agglomerate microstructure built of primary aggregates. Conferring colloidal stability in aqueous carbon black suspensions should thus have a drastic impact on their viscosity and conductivity. Carbon black was treated with strong acids following a wet oxidation procedure. An analysis of the resulting particle surface chemistry and electrophoretic mobility was performed in evaluating colloidal stability. Changes in suspension microstructure due to oxidation were observed using small-angle X-ray scattering. Utilizing rheo-electric measurements, the evolution of the viscosity and conductivity of the carbon black suspensions as a function of shear rate and carbon content was thoroughly studied. The carboxyl groups installed on the carbon black surface through oxidation increased the surface charge density and enhanced repulsive interactions. Electrostatic stability inhibited the formation of the large-scale agglomerates in favor of the stable primary aggregates in suspension. While shear thinning, suspension conductivities were found to be weakly dependent on the shear intensity regardless of the carbon content. Most importantly, aqueous carbon black suspensions formulated from electrostatically repulsive primary aggregates displayed a smaller rise in conductivity with carbon content compared to those formulated from attractive agglomerates.

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

Effect of grain size on iron-boride nanoglasses

Metallic nanoglasses are made of amorphous grains that are separated by lower-density amorphous boundaries, which have been proposed to enhance plasticity through the deflection of cracks and shear bands at interfaces. It has been difficult to experimentally control grain size and interfacial structure to understand their roles in plastic deformation. Here, we fabricate bulk nanoglasses via compaction and sintering of colloidally synthesized amorphous iron-boride nanoparticles. These nanoglasses have amorphous grains with diameters from 116nm to 576nm and were tested using nanoindentation and micropillar compressions. The nanoglass with a grain size of 576 nm shows the highest elastic modulus and hardness of 101 GPa and 7.4GPa, respectively. Transmission electron microscopy reveals that nanocrystals form within the nanoglasses during compaction. Higher nanocrystal density correlates with higher nanoparticle crystallization enthalpy, an increase in plasticity, and a decrease in yield strength. Plastic strain of 5.0%, yield strength of 3.8GPa, and ultimate compressive strength of 2.7–3.8GPa were achieved. Here we show that the compaction of colloidal metallic glass nanoparticles results in robust bulk samples, with mechanical properties similar to that of other iron-based bulk metallic glasses.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Synthesis, characterization and alloying of Cu{sub 2}ZnSnQ{sub 4} (Q=S, Se and Te) nanocrystals

Cu{sub 2}ZnSnQ{sub 4} nanocrystals, with Q=S, Se and Te, were grown by a colloidal synthetic approach and characterized by X-ray diffraction, transmission electron microscopy, and optical absorbance. We also demonstrate that doping and alloying at the nanoscale is possible by this approach. The results are discussed in terms of developing a standardized synthetic approach for the synthesis of quaternary nanocrystals, including doping and alloying, in order to allow for bottom-up processing of these materials for energy-related applications. - Graphical abstract: We developed a standardized synthetic approach for the synthesis of quaternary stannite Cu{sub 2}ZnSnQ{sub 4} nanocrystals with Q=S, Se and Te including doping, alloying and Te-based compositions for the first time, in order to allow for bottom-up processing of these materials for energy-related applications. - Highlights: • Cu{sub 2}ZnSnQ{sub 4} nanocrystals, with Q=S, Se and Te, were grown by a colloidal synthetic approach. • Doping and alloying of these quaternary nanocrystals were demonstrated for the first time. • This standardized synthetic approach allows for bottom-up processing of these materials for energy-related applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Plutonium Redox Transformation in the Presence of Iron, Organic Matter, and Hydroxyl Radicals: Kinetics and Mechanistic Insights

Plutonium (Pu) redox and complexation processes in the presence of natural organic matter and associated iron can impact the fate and transport of Pu in the environment. In this work, we studied the fate of Pu(IV) in the presence of humic acid (HA) and Fe(II) upon reaction with H 2 O 2 that may be generated by photochemical and other reactions. A portion of Pu(IV) was oxidized to Pu(V/VI), which is primarily ascribed to the generation of reactive intermediates from the oxidation of Fe(II) and Fe(II)–HA complexes by H 2 O 2 . The kinetics of Pu(IV) oxidation is pH-dependent and can be described by a model that incorporates Pu redox kinetics with published HA-modified Fenton reaction kinetics. At pH 3.5, the presence of HA slowed Pu(IV) oxidation, while at pH 6, HA accelerated Pu(IV) oxidation in the first several hours followed by a reverse process where the oxidized Pu(V/VI) was reduced back to Pu(IV). Analysis of Pu-associated particle size suggests that Pu oxidation state is a major driver in its complexation with HA and formation of colloids and heteroaggregates. Our results revealed the H 2 O 2 -driven oxidation of Pu(IV)–HA–Fe(II) colloids with implications to the transient mobilization of Pu(V/VI) in organic-rich redox transition zones.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction

The activity of colloidally synthesized CoP for the hydrogen evolution reaction (HER) was studied to determine the impact of surface ligand on catalysis. The as-synthesized CoP nanocrystals were stripped with trialkyloxonium tetrafluoroborate (Meerwein’s reagent) to create a “blank template” that was then religated with carboxylates (oleate, octanoate, acetate) and amines (oleylamine, octylamine, dioctylamine, trioctylamine butylamine). Carboxylates and amines were chosen due to their prevalence in colloidal syntheses, and the range of ligands was chosen to study the impact of sterics and hydrophobicity of the surface ligands on catalysis. Long chain carboxylates were found to result in a larger increase in overpotential when compared to the equivalent amine (e.g., oleate vs oleylamine), due to higher ligand density and stronger coordination with carboxylates. Increased carbon chain length resulted in increased overpotential with carboxylates; however, the range of 1° amines studied had similar overpotentials. This is due to the lower ligand density and therefore sparse ligand packing for the 1° amines. These results suggest that the mechanism by which surface ligands impede catalysis on CoP for HER is primarily through inhibiting substrate access to surface active sites rather than poisoning the active sites.

cobalt phosphide, hydrogen evolution reaction, lig↗
DOE OSTI2025

PFSA-Ionomer Adsorption to C and Pt/C Particles in Fuel-Cell Inks

Catalyst inks used to make fuel-cell electrodes consist of Pt/C catalyst particles and a perfluorosulfonic acid (PFSA) ionomer dispersed in water/alcohol solvent mixtures. PFSA ionomer in the ink adsorbs to the surface of the catalyst particles, dictating the dispersion colloid properties. Following adsorption, the subsequent distribution of excess nonadsorbed ionomer in the ink then governs the final structure of the electrode. Here, we characterize the adsorption of the PFSA ionomer onto Pt/C catalyst particles. PFSA adsorption is largely irreversible. Adsorbed sulfonic-acid moieties impart a negative charge on the catalyst surface, causing electrostatic repulsion between the free ionomer in solution and the ionomer-covered Pt/C particle surface. The amount of adsorption is limited by the resulting electrostatic charge that grows as more ionomer adsorbs, and the catalyst surface becomes more negatively charged. Attenuating electrostatic repulsion by increasing the ink ionic strength promotes ionomer adsorption. Electrostatically limited adsorption is observed, irrespective of the solvent water/n-propanol ratio or the catalyst particle porosity and Pt loading. Experimentally measured ionomer adsorption isotherms are well predicted by a Smoluchowski-based kinetic adsorption model, in which the electrostatic energy barrier for adsorption is predicted from DLVO theory. These findings help to unravel the complex phenomena within these colloidal dispersions, allowing for subsequent tailoring of inks to optimize fuel-cell electrode structure and performance.

Adsorption↗
DOE OSTI2019

Effect of Passivating Shells on the Chemistry and Electrode Properties of LiMn 2 O 4 Nanocrystal Heterostructures

Building a stable chemical environment at the cathode/electrolyte interface is directly linked to the durability of Li-ion batteries with high energy density. Recently, colloidal chemistry methods have enabled the design of core–shell nanocrystals of Li 1+x Mn 2–x O 4 , an important battery cathode, with passivating shells rich in Al 3+ through a colloidal synthetic route. These heterostructures combine the presence of redox-inactive ions on the surface to minimize undesired reactions, with the coverage of each individual particle in an epitaxial manner. Although they improve electrode performance, the exact chemistry and structure of the shell as well as the precise effect of the ratio between the shell and the active core remain to be elucidated. Correlation of these parameters to electrode properties would serve to tailor the heterostructure design toward complete shutdown of undesired reactions. These knowledge gaps are the target here. Li 1+x Mn 2–x O 4 nanocrystals with Al 3+ -rich shells of different thicknesses were synthesized. Multimodal characterization comprehensively revealed the elemental distribution, electronic state, and crystallinity in the heterostructures, which confirmed the potential of this approach to finely tune passivating layers. All of the modified nanocrystals improved the capacity retention while retaining charge storage compared to the bare counterpart, even under harsh conditions.

25 ENERGY STORAGE↗
DOE OSTI2018

Predicting Nanoparticle Suspension Viscoelasticity for Multimaterial 3D Printing of Silica–Titania Glass

A lack of predictive methodology is frequently a major bottleneck in materials development for additive manufacturing. Hence, exploration of new printable materials often relies on the serendipity of trial and error approaches, which is time-consuming, labor-intensive, and costly. In this paper, we present an approach to overcome these issues by quantifying and controlling the viscoelasticity of inks for multimaterial 3D printing of silica–titania glass using direct ink writing (DIW). We formulate simple silica and silica–titania inks from a suspension of fumed silica nanoparticles in an organic solvent with a dissolved molecular titania precursor. We use a small set of experimental rheological data and estimates of interaction potentials from colloidal theory to develop a predictive tool that allows us to design and obtain compatible inks that are matched both in desired rheological properties (viscosity profiles and elastic modulus) as well as solids loading. The model incorporates silica particle volume fraction, particle size, particle size distribution, and titania precursor concentration, and captures the effects of all formulation parameters on the measured viscoelasticity in a single curve. We validate the ink formulations predicted by the model and find that the materials can be very well matched in rheological properties as desired for 3D printing. Using the DIW and heat treatment methods we have reported previously, we use these inks to print and process a fully transparent glass with spatial change in dopant composition and refractive index. Finally, we believe that this approach can be extended to other colloidal systems and allow predictive ink formulation design for desired printability in direct ink write manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Discovery of Gold Nanoparticles in Marcellus Shale

A high density of gold (Au) nanoparticles has been observed on the surfaces of the coexisting opal nanospheres in kerogen-bearing shales from the Marcellus Formation. Our analyses of the Au nanoparticles and associated minerals indicate that this represents a new formation type of colloidal gold nanoparticles. Additionally, the opal nanospheres are a new kind of natural opal-A that is characteristic of the mesoporous texture formed through oil-in-water emulsion processes. High-resolution transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy analysis directly reveals spherical gold nanoparticles and gold nanorods associated with mesoporous opal nanospheres. Our newly found textures indicate that opal nanospheres may have facilitated the co-precipitation of pure gold nanoparticles in organic-bearing, reduced environments. Furthermore, our TEM observations provide distinct images of the initial phase of colloidal gold and silica, which may contribute to the formation of Au deposits involving "invisible" gold, secondary supergene enrichments, or high-grade gold accumulations. Finally, the discovery of Au nanoparticles in hydrocarbon-rich shale formations such as Marcellus (which contains 0.6-4.1 wt % gold/opal) suggests a potential for co-production of both gas/oil and gold-two valuable commodities.

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

Solution-Processed Ultrafast, Room-Temperature Single-Photon Source at 1550 nm

Single photons are cornerstones of quantum technologies. The need for an ultrafast, bright, and stable photon source emitting in the telecom-band at ∼1550 nm, ideally operating at room temperature, has resulted in a decades-long quest. However, to date, telecom sources are hampered by inherently long radiative lifetimes that severely limit brightness and speed, material instability, or the need for cryogenic operation. Here, in this study, stable colloidal PbS/CdS quantum dots emitting at 1550 nm (C-band) or 1350 nm (O-band) are embedded in a solution-synthesized nanoparticle-on-mirror cavity. Single cavity-coupled quantum dots experience extreme Purcell factors up to 10,700, resulting in ultrafast emission lifetimes of 65 ps, along with near-complete blinking suppression. As a result, 12 million single photons are emitted per second affording a single photon source at 1550 nm that is more than two orders of magnitude brighter than previously possible at room-temperature. These telecom-band single photon sources are solution-processable and lithography-free and may leverage mature colloidal fabrication technologies for future quantum applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nanotechnology: Colourful Particles for Spectrometry

In 1857 Michael Faraday gave a well-attended lecture at the Royal Institution of Great Britain, in which he presented his pioneering experimental work that investigated the interaction of light with matter. Faraday’s study probed the fundamental properties of light as it was reflected and absorbed by progressively smaller particles. Very fine gold particles dispersed in liquid were shown to produce vivid colors not seen in larger particles. Faraday did not know he had created colloidal suspensions of quantum dots, but his insight correctly concluded that the distinct colors were somehow due to the minute size of the gold particles. This great experimental physicist had actually glimpsed a special condition where the particle’s quantum nature was expressed. This work set the future course for nanoscience and quantum theory, but it would take another 125 years before the physical basis of this phenomenon would be explained by quantum size effects. It is now known that when quantum dots are exposed to UV light, some of the electrons are excited as they gain energy, however they remain confined to discrete energy levels not observed in larger particles and solid materials. When the electrons relax and lose their energy, the quantum dot emits light at a specific color that varies with the size of the quantum dot. Bao and Bawendi have cleverly exploited the unique optical properties intrinsic to colloidal quantum dots to develop an innovative compact optical spectrometer that could be integrated with a smart phone camera or as a versatile miniature handheld sensing tool.

Colloidal quantum dots↗
DOE OSTI2014

Real time monitoring of superparamagnetic nanoparticle self-assembly on surfaces of magnetic recording media

Nanoparticle self-assembly dynamics are monitored in real-time by detecting optical diffraction from an all-nanoparticle grating as it self-assembles on a grating pattern recorded on a magnetic medium. The diffraction efficiency strongly depends on concentration, pH, and colloidal stability of nanoparticle suspensions, demonstrating the nanoparticle self-assembly process is highly tunable. This metrology could provide an alternative for detecting nanoparticle properties such as colloidal stability.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Manipulating light propagation and emission using photonic crystals

We discuss the synthesis and characterization of self-assembled photonic crystals using polymer colloids having sub-micron diameters. The angle resolved optical reflectivity measurements indicate the hybridization between stop gaps in the multiple Bragg diffraction regimes. Each diffraction resonances in the multiple Bragg diffraction regimes are assigned to respective crystal planes. We also discuss laser-induced studies of spontaneous emission in self-assembled photonic crystals having Rhodamine-B dye doped colloids. Our experimental results reveal more than 51% inhibition in emission intensity within the stop gap as compared to a proper reference sample.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗