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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Investigation of Nanoparticle Degradation in Hydrogen Fuel Cell Systems through Automated Electron Microscopy

Proton exchange membrane fuel cells (PEMFC) are promising devices for the deployment of hydrogen-powered heavy-duty vehicles, providing a higher efficiency for similar driving range and fueling time than the existing ones. However, PEMFCs still encounter durability challenges mainly due to catalyst degradation in the cathode. Mitigating these performance losses requires a better understanding of the degradation mechanisms under heavy-duty accelerated stress tests (ASTs) [1]. Scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) are key tools for the analysis of Pt and PtCo nanoparticle size, spatial distribution and composition [2]. Electron tomography is also used to determine the rate and type of degradation of catalyst nanoparticles as a function of their position on the carbon support. In this work, automated data acquisition software, paired with a custom Python code, have been used to study the effect of different accelerated stress tests (ASTs) on nanoparticle coarsening [2]. Figure 1 shows high-angle annular dark-field (HAADF)-STEM images and EDS maps comparing the cathodes of membrane electrode assemblies (MEAs) following an electrocatalyst AST performed under H2/N2 with that of the heavy-duty AST performed under H2/air. We will discuss how AST conditions affect considerably the spatial distribution of the nanoparticles across the electrode between the membrane and microporous layer. Although the median particle size increased more in the MEA aged under the heavy-duty AST, as determined using a high-throughput image analysis, the quantitative EDS measurements demonstrate that the electrocatalyst AST resulted in more Pt and Co dissolution from the cathode, which is another important indicator of electrocatalyst degradation. We will further present the impact of the relative humidity (% RH) on the degradation mechanisms demonstrated using the same approach. Electron tomography has been used to distinguish the Pt nanoparticles residing on the carbon support surface (exterior) from those within the pore structure (interior) in order to determine the relative stability of interior and exterior nanoparticles. As shown in Figure 2, we will compare the Pt catalyst particle size at the beginning of test (BOT) and end of test (EOT), and discuss the importance of automating the electron tomography workflow, i.e. acquisition, reconstruction, and visualization, to increase sampling and determine the standard deviation of these measurement. The outlook for utilizing low-dose cryo-tomography for limiting damage to the catalyst, support, and especially proton-conducting ionomer will also be discussed [3].

Amichi, Lynda↗
DOE OSTI2024

Magnetic Nanoparticle Extraction of Lithium from Produced Waters - CRADA 483 (Final Report)

The demand for lithium in the energy production industry is expected to increase sharply, development of simple and cost-effective techniques for lithium production and recovery from various lithium sources is essential. In this project, core/shell magnetic nanoparticles were successfully designed to selectively extract lithium from aqueous lithium sources as an extension of Pacific Northwest National Laboratory’s magnetic nanofluid extraction technology. The core/shell magnetic nanoparticles are composed of manganese oxide-based lithium ion sieve shells, which allow selective lithium uptake from brines with multiple coexisting ions, over iron oxide cores, which can respond to external magnetic fields for effective recovery and reuse of adsorbents from a liquid. The synthesized lithium ion-sieves and core/shell magnetic nanoparticles were characterized using several techniques to reveal their crystallinity and morphology. The lithium uptake properties of the lithium ion-sieves and core/shell magnetic nanoparticles were evaluated in terms of lithium adsorption capacity, removal percentage, selectivity, and cycling performance in simulated and natural brines. Magnetic properties of the core/shell magnetic nanoparticles were tested by measuring magnetic saturation, and magnetic response of colloidal solutions containing the core/shell magnetic nanoparticles was tested with permanent magnets.

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

Enhanced Silver Nanoparticle Synthesis by Escherichia Coli Transformed with Candida Albicans Metallothionein Gene

In this study, the metallothionein gene of Candida albicans (C. albicans) was assembled by polymerase chain reaction (PCR), inserted into pUC19 vector, and further transformed into Escherichia coli (E. coli) DH5α cells. The capacity of these recombinant E. coli DH5α cells to synthesize silver nanoparticles was examined. Our results demonstrated that the expression of C. albicans metallothionein in E. coli promoted the bacterial tolerance to metal ions and increased yield of silver nanoparticle synthesis. The compositional and morphological analysis of the silver nanoparticles revealed that silver nanoparticles synthesized by the engineered E. coli cells are around 20 nm in size, and spherical in shape. Importantly, the silver nanoparticles produced by the engineered cells were more homogeneous in shape and size than those produced by bacteria lack of the C. albicans metallothionein. Our study provided preliminary information for further development of the engineered E. coli as a platform for large-scale production of uniform nanoparticles for various applications in nanotechnology.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Superparamagnetic nanoparticles and nanocomposites

The present invention is directed to the syntheses of superparamagnetic nanoparticles and the incorporation of the nanoparticles as the magnetic component to form a strongly magnetic nanocomposite. The superparamagnetic nanoparticles possess no hysteresis and are too small to support eddy currents. The invention uses a ligand exchange procedure to produce aminated nanoparticles that are then cross-linked using epoxy chemistry. The result is a magnetic nanoparticle component that is covalently linked and well separated. By using this ‘matrix-free’ approach, it is possible to substantially increase the magnetic nanoparticle fraction, while still maintaining good separation, leading to a superparamagnetic nanocomposite with strong magnetic properties and low magnetic losses.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Systems and methods for scale-up synthesis multi-layered Pt-skin nanoparticle catalysts

A method for scaled-up synthesis of PtNi nanoparticles. Synthesizing a Pt nanoparticle catalyst comprises the steps of: synthesizing PtNi nanoparticles, isolating PtNi/substrate nanoparticles, acid leaching the PtNi/substrate, and annealing the leached PtNi/substrate nanoparticles, and forming a Pt-skin on the PtNi/substrate nanoparticles.

Stamenkovic, Vojislav↗
DOE OSTI2021

Structurally ordered nanoparticles, methods and applications

Embodiments provide a nanoparticle and a method for preparing the nanoparticle, as well as a membrane that includes the nanoparticle and a fuel cell that includes the membrane. The method comprises a thermal treatment method that provides from a nanoparticle comprising a structurally disordered material the nanoparticle comprising: (1) a structurally ordered core comprising a first material; and (2) a shell surrounding and further structurally aligned with the structurally ordered core and comprising a second material different from the first material. Particularly desirable is a nanoparticle comprising a Pt3Co@Pt/C structurally ordered core-shell composition supported upon a carbon support.

Abruna, Hector D.↗
DOE OSTI2021

Colloidal immobilized protein based on stable colloid of TiO 2 nanoparticles at neutral pH for protein microarray

A stable colloid of titanium dioxide nanoparticles was specially prepared at neutral pH so that horse radish peroxidase as a model protein can interact and be immobilized with colloidal titanium dioxide nanoparticles, while usually titanium dioxide colloid is only stable at acidic condition. Colloidal immobilized peroxidase based on titanium dioxide nanoparticles at neutral pH were highly active and stably dispersible in aqueous solution. The resulting colloidal immobilized peroxidase can be readily printed using a standard microarray printer for facile fabrication of protein microarrays. After printing, the colloidal immobilized protein formed uniform membrane of proteinated nanoparticles with 3-dimensional nanoconfiguration. Finally, the protein microarray sensitivity based on peroxidase-titanium dioxide nanoparticles was nearly 20 times as high as that using conventional technology.

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

Hairy nanoparticles by atom transfer radical polymerization in miniemulsion

Polymer nanoparticles with various architectures and functionalities are promising materials in numerous fields. Miniemulsion polymerization is one of the suitable pathways to prepare polymer nanoparticles since each droplet could act as a “nanoreactor”. A “smart” atom transfer radical polymerization (ATRP) catalytic system comprising Cu-TPMA/DS – (TPMA = tris(2-pyridylmethyl)amine, DS – = dodecyl sulfate anion) ion pair catalyst was efficiently applied in miniemulsion ATRP at low catalyst concentrations. Herein, hairy nanoparticles consisting of hydrophobic poly(n-butyl methacrylate) (P(BMA/EGDMA), EGDMA = ethylene glycol dimethacrylate) network “core” and hydrophilic oligo(ethylene oxide) methyl ether methacrylate (OEOMA) chains as “hair” were prepared by miniemulsion ATRP and a successive chain extension by aqueous ATRP from the particle surface. The addition of an inimer, 2-(α-bromoisobutyryloxy)ethyl methacrylate (HEMA-iBBr) to the P(BMA/EGDMA) network introduced more ATRP initiation sites for ATRP of OEOMA, enabling adjustment of the particle size from >400 nm to <150 nm. The miniemulsion system remained stable after the one pot synthesis of P(BMA/EGDMA)-g-POEOMA and P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA, and the resulting polymer nanoparticles were re-dispersed in water for further modification. A zwitterionic monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was grafted from P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA. The resulting hairy nanoparticles provide an avenue for the design and preparation of novel nanostructured materials.

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

Evaluation of Force Fields for Molecular Dynamics Simulations of Platinum in Bulk and Nanoparticle Forms

Here, understanding the size- and shape-dependent properties of platinum nanoparticles is critical for enabling the design of nanoparticle-based applications with optimal and potentially tunable functionality. Toward this goal, we evaluated nine different empirical potentials with the purpose of accurately modeling faceted platinum nanoparticles using molecular dynamics simulation. First, the potentials were evaluated by computing bulk and surface properties - surface energy, lattice constant, stiffness constants, and the equation of state - and comparing these to prior experimental measurements and quantum mechanics calculations. Then, the potentials were assessed in terms of the stability of cubic and icosahedral nanoparticles with faces in the {100} and {111} planes, respectively. Although none of the force fields predicts all the evaluated properties with perfect accuracy, one potential - the embedded atom method formalism with a specific parameter set - was identified as best able to model platinum in both bulk and nanoparticle forms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Extraordinary Thermal Stability and Sinter Resistance of Sub-2 nm Platinum Nanoparticles Anchored to a Carbon Support by Selenium

Nanoparticle sintering has long been a major challenge in developing catalytic systems for use at elevated temperatures. Here we report an in situ electron microscopy study of the extraordinary sinter resistance of a catalytic system comprised of sub-2 nm Pt nanoparticles on a Se-decorated carbon support. When heated to 700 °C, the average size of the Pt nanoparticles only increased from 1.6 to 2.2 nm, while the crystal structure, together with the {111} and {100} facets, of the Pt nanoparticles was well retained. Our electron microscopy analyses suggested that the superior resistance against sintering originated from the Pt–Se interaction. Confirmed by energy-dispersive X-ray elemental mapping and electron energy loss spectra, the Se atoms surrounding the Pt nanoparticles could survive the heating. This work not only offers an understanding of the physics behind the thermal behavior of this catalytic material but also sheds light on the future development of sinter-resistant catalytic systems.

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

Magnetic and Optical Properties of Au–Co Solid Solution and Phase-Separated Thin Films and Nanoparticles

The chemical composition and morphology of Au x Co 1–x thin films and nanoparticles are controlled via a combination of cosputtering, pulsed laser-induced dewetting (PLiD), and annealing, leading to tunable magnetic and optical properties. Regardless of chemical composition, the as-deposited thin films and as-PLiD nanoparticles are found to possess a face-centered cubic (FCC) Au x Co 1–x solid-solution crystal structure. Annealing results in large phase-separated grains of Au and Co in both the thin films and nanostructures for all chemical compositions. The magnetic and optical properties are characterized via vibrating sample magnetometry (VSM), ellipsometry, optical transmission spectroscopy, and electron energy loss spectroscopy (EELS). Despite the exceptionally high magnetic anisotropy inherent to Co, the presence of sufficient Au (72 atom %) in the Au x Co 1–x solid solution results in superparamagnetic thin films. Among the as-PLiD nanoparticle samples, an increased Co composition leads to a departure from traditional ferromagnetism in favor of wasp-waisted hysteresis caused by magnetic vortices. Phase separation resulting from annealing leads to ferromagnetism for all compositions in both the thin films and nanoparticles. The optical properties of Au x Co 1–x nanostructures are also largely influenced by the chemical morphology, where the Au x Co 1–x intermixed solid solution has significantly damped plasmonic performance relative to pure Au and comparable to pure Co. Phase separation greatly enhances the quality factor, optical absorption, and electron energy loss spectroscopy (EELS) signatures. The enhancement of the localized surface plasmon resonances (LSPRs) scales with the reduction in Co composition, despite EELS evidence that excitation of the Co portions of a nanoparticle can provide a similar, and in some instances enhanced, LSPR resonance compared to Au. This behavior, however, is seemingly limited to the LSPR dipole mode, while higher-order modes are greatly damped by a Co aloof position. As a result, this observed magneto-plasmonic functionality and tunability could be applicable in biomedicine, namely, cancer therapeutics.

annealing (metallurgy)↗
DOE OSTI2022

Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior

Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO 2 ) and vinyl-functionalized (V-SiO 2 ) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO 2 composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO 2 induced no significant changes in gel fraction and both V-SiO 2 and MA-SiO 2 nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO 2 composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO 2 composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO 2 and a monomodal size distribution for MA-SiO 2 . Although aggregates were observed for both nanoparticle surface treatments, V-SiO 2 dispersion was poor while MA-SiO 2 were generally well-dispersed. Finally, these findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.

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

Regulating the Catalytic Activity of Pd Nanoparticles by Confinement in Ordered Mesoporous Supports

Studying structure-sensitive reactions requires the synthesis of catalytic nanoparticles with precisely controlled sizes. Here we demonstrate the facile production of size controlled Pd nanoparticles by confinement in the pores of mesoporous silica nanoparticles (MSN). We show that Pd particles 2.1 nm in size have a higher catalytic activity than larger nanoparticles for the Suzuki-Miyaura cross coupling between 4’-bromoacteophenone and phenyl boronic acid and for the hydrogenation of phenol in aqueous phase. The enhanced activity can be explained in terms of increased number of coordinatively unsaturated sites and higher back donation capacity of the small nanoparticles.

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

Optical and Mechanical Properties of Nanocomposite Films Based on Polymethyl Methacrylate (PMMA) and Fumed Silica Nanoparticles

Nanocomposite polymer films are prepared by using ultrasonic spray deposition (USD) technique through mixing polymethyl methacrylate as matrix and fumed silica nanoparticles as second phase in dimethyl carbonate solvent. Annealing procedure improves the film uniformity and optical transmission. The addition of fumed silica nanoparticles impedes the transmission of the electrolyte films due to agglomeration of fumed silica nanoparticles. Adding surfactant, cetyltrimethylammonium bromide, disperses the fumed silica nanoparticles and retrieves the optical transmission of nanocomposite polymer films to around 90%. The hardness and elastic modulus of the nanocomposite polymer films are better than the commercial bulk. The USD deposited nanocomposite polymer film comprises of PMMA and fumed silica nanoparticles is a promising candidate of solid-state electrolyte for EC windows application.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sculpting the Plasmonic Responses of Nanoparticles by Directed Electron Beam Irradiation

Spatial confinement of matter in functional nanostructures has propelled these systems to the forefront of nanoscience, both as a playground for exotic physics and quantum phenomena and in multiple applications including plasmonics, optoelectronics, and sensing. In parallel, the emergence of monochromated electron energy loss spectroscopy (EELS) has enabled exploration of local nanoplasmonic functionalities within single nanoparticles and the collective response of nanoparticle assemblies, providing deep insight into associated mechanisms. However, modern synthesis processes for plasmonic nanostructures are often limited in the types of accessible geometry, and materials and are limited to spatial precisions on the order of tens of nm, precluding the direct exploration of critical aspects of the structure-property relationships. Here, the atomic-sized probe of the scanning transmission electron microscope is used to perform precise sculpting and design nanoparticle configurations. Using low-loss EELS, dynamic analyses of the evolution of the plasmonic response are provided. It is shown that within self-assembled systems of nanoparticles, individual nanoparticles can be selectively removed, reshaped, or patterned with nanometer-level resolution, effectively modifying the plasmonic response in both space and energy. This process significantly increases the scope for design possibilities and presents opportunities for unique structure development, which are ultimately the key for nanophotonic design.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Mitigating keyhole pore formation by nanoparticles during laser powder bed fusion additive manufacturing

Keyhole pore formation is one of the most detrimental subsurface defects in the laser metal additive manufacturing process. However, effective ways to mitigate keyhole pore formation beyond tuning laser processing conditions during keyhole mode laser melting are still lacking. Here we report a novel approach to mitigate keyhole pore formation during laser powder bed fusion (LPBF) process by using stable nanoparticles. The critical keyhole depth for keyhole pore generation (i.e., the largest keyhole depth without keyhole pore formation) during LPBF of Al6061 increases from 246 µm to 454 µm (85% increase) after adding TiC nanoparticles. In-depth x-ray imaging studies and thermo-fluid dynamics simulation enable us to identify that two mechanisms work together to mitigate keyhole pore generation: (1) adding nanoparticles prevents the keyhole from collapsing by increasing the liquid viscosity to impede the protrusion development; (2) adding nanoparticles slows down the keyhole pore movement by increasing the liquid viscosity, resulting in the recapturing of the pore by the keyhole. We further demonstrate that adding TiC nanoparticles can also eliminate the keyhole fluctuation induced keyhole pore during LPBF of Al6061. Our research provides a potential way to mitigate keyhole pore formation for defect lean metal additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Impact of hydrogen bonding pendant groups in polymer grafted nanoparticles on interlayer adhesion and mechanical properties in material extrusion printing

The addition of nanoparticles or copolymer grafted nanoparticles (CPGNPs) to polymeric matrices greatly improves thermomechanical properties of the resulting nanocomposite, but corresponding studies of nanocomposite systems created by 3D printing are few, especially in the realm of functional polymeric materials. Here we describe how silica nanoparticle-grafted, random copolymers of poly(methyl methacrylate-random-2-uriedo-[1H]-pyrimidinone methacrylate) (P(MMA-r-UPyMA) dramatically increases the mechanical properties of poly(methyl methacrylate) (PMMA) based nanocomposite specimens created by melt extrusion printing. Most notably, when these novel CPGNPs are combined with PMMA matrix chains via a solution-based process, printed specimens containing only 0.5 wt% additive show significant increases in Young’s modulus (90%), storage modulus (93%), tensile modulus (148%) and ultimate tensile strength (110%). These improvements are ascribed to strengthening of adhesion across interfaces due to multi-point hydrogen bonding between UPyMA groups, the reinforcement effect of the P(MMA-r-UPyMA)-grafted silica nanoparticles, as well as hydrogen bonding interactions and entanglements between graft and matrix chains. Imaging of fracture surfaces after tensile testing reveals that in comparison to nanocomposites created by simple mechanical mixing of solids, the solution-casting process improves the dispersion of nanoparticles and reduces the void spaces between printed roads. These studies demonstrate that introducing functionality into polymer grafts, such as hydrogen bonding interactions, and intimate mixing of polymer-modified nanomaterials can greatly improve interlayer adhesion and mechanical properties, thereby advancing this method of polymer additive manufacturing

36 MATERIALS SCIENCE↗
DOE OSTI2025

Effect of grafting density on the two-dimensional assembly of nanoparticles

Employing grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we demonstrate that films composed of polyethylene glycol (PEG)-grafted silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), as well as their binary mixtures, form highly stable hexagonal structures at the vapor–liquid interface. These nanoparticles exhibit remarkable stability under varying environmental conditions, including changes in pH, mixing concentration, and PEG chain length. Short-chain PEG grafting produces dense, well-ordered films, while longer chains produce more complex, less dense quasi-bilayer structures. AuNPs exhibit higher grafting densities than AgNPs, leading to more ordered in-plane arrangements. In binary mixtures, AuNPs dominate the population at the surface, while AgNPs integrate into the system, expanding the lattice without forming a distinct binary superstructure. In conclusion, these results offer valuable insights into the structural behavior of PEG-grafted nanoparticles and provide a foundation for optimizing binary nanoparticle assemblies for advanced nanotechnology applications.

36 MATERIALS SCIENCE↗