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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Use of Transmission Electron Microscopy for Analysis of Aerosol Particles and Strategies for Imaging Fragile Particles

For over 25 years, transmission electron microscopy (TEM) has provided a method for the study of aerosol particles with sizes from below the optical diffraction limit to several microns, resolving the particles as well as smaller features. The wide use of this technique to study aerosol particles has contributed important insights about environmental aerosol particle samples and model atmospheric systems. TEM produces an image that is a 2D projection of aerosol particles that have been impacted onto grids and, through associated techniques and spectroscopies, can contribute additional information such as the determination of elemental composition, crystal structure, and 3D particle structures. Soot, mineral dust, and organic/inorganic particles have all been analyzed using TEM and spectroscopic techniques. TEM, however, has limitations that are important to understand when interpreting data including the ability of the electron beam to damage and thereby change the structure and shape of particles, especially in the case of particles composed of organic compounds and salts. In this paper, we concentrate on the breadth of studies that have used TEM as the primary analysis technique. Another focus is on common issues with TEM and cryogenic-TEM. Insights for new users on best practices for fragile particles, that is, particles that are easily susceptible to damage from the electron beam, with this technique are discussed. Tips for readers on interpreting and evaluating the quality and accuracy of TEM data in the literature are also provided and explained.

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

Solid phase characterization and transformation of illite mineral with gas-phase ammonia treatment

In situ remediation applications of ammonia (NH 3 ) gas have potential for sequestration of subsurface contamination. Ammonia gas injections initially increase the pore water pH leading to mineral dissolution followed by formation of secondary precipitates as the pH is neutralized. However, there is a lack of understanding of fundamental alteration processes due to NH 3 treatment. In these batch studies, phyllosilicate minerals (illite and montmorillonite) were exposed to NH 3 gas with subsequent aeration to simulate in situ remediation. Following treatments, solids were characterized using a variety of techniques, including X-ray diffraction, N 2 adsorption-desorption analysis for surface area, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and microscopy methods to investigate physicochemical transformations. The results of this study indicate that, at high pH, the clays are altered as observed by differences in morphology and particle size via microscopy. However, the two clays interact differently with NH 3 . While montmorillonite interlayers collapsed due to intercalation, illite layers were unaffected as confirmed by FTIR analysis. Further, structural changes in silicate ([SiO 4 ] n- ) and aluminol (Al-OH) groups were identified by NMR and FTIR. This research showed that mineral alteration processes occur during and after NH 3 gas treatment which may be used to remove radionuclides from the aqueous phase through sorption, co-precipitation, and coating with secondary phyllosilicate alteration products.

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

Tailored Mesoporous Microspheres by Polymerization-Induced Microphase Separation in Suspension

We describe the preparation of block polymer beads by aqueous suspension polymerization to create poly(caprolactone) (PCL)-block-poly(styrene-co-divinylbenzene) beads that can be selectively etched under basic conditions to yield mesoporous polymer microspheres with uniform pore size. Polyvinylalcohol was used to stabilize the suspension polymerization in which styrene and divinylbenzene monomers were polymerized from a PCL macrochain transfer agent (macroCTA). The resulting polymerization-induced microphase separation process led to a nanostructured bicontinuous morphology. The particle size and pore size were independently tunable: the particle size was controlled by the stir rate of the suspension polymerization-yielding average diameters ranging from 60 to 300 μm-while the pore size was determined by the molar mass of the PCL block, with the mode pore diameters being 6 nm and 11 nm after etching beads made using 13 and 45 kg/mol PCL blocks, respectively. Based on nitrogen sorption measurements, the surface areas of the beads were ~300 m 2 /g when using a PCL macroCTA of 13 kg/mol. The beads were homogenous throughout on the micron length scale as determined by confocal Raman microscopy and lacked an impermeable skin layer as confirmed by scanning electron microscopy. Furthermore, the scalability of suspension polymerization allows for the simple synthesis of large quantities of thermoset microspheres with uniform pore size. We also demonstrate the ability to incorporate functional pore walls into the beads using multiblock precursor polymers. These functionalized mesoporous polymer beads show high affinity for ionic dyes in aqueous solutions (as a proof of principle) and remove dye from the solution at rates exceeding those of commercial ion-exchange resins. The developed procedure could be used to generate other functional surface chemistries with important applications in heterogeneous catalysis, chromatography, and water remediation.

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

Impact of Precipitation Parameters on the Specific Surface Area of PuO 2

Controlling the properties of PuO 2 through processing is of vital importance to environmental transport and fate, production of nuclear fuels, nuclear forensic analyses, stockpile stewardship, and storage of nuclear wastes applications. A number of processing conditions have been identified to control final product properties, including specific surface area (SSA), residual carbon content, adsorption of volatile species, morphology, and particle size. In this paper, a novel approach is developed for the prediction of PuO 2 SSA via the synthetic route of Pu(IV) oxalate precipitation followed by calcination. The proposed model utilizes multivariate regression methodology and leave one out formalism to link Savannah River Site (SRS) precipitation and calcination production data to the SSA of the final product. A comparison among the models provides insight into the accuracy and ability to identify variations amongst the processing data. Additionally, the models may also be used to fit new data outside of the parameters explored in a production facility. Finally, the trained model was compared to a similarly trained conventional model form to illustrate the influence of precipitation parameters on the prediction of the final SSA. The models presented here attempt to provide new methods for more accurate prediction of the PuO 2 product properties in a production scale environment for key environmental and nuclear applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Harnessing Solvent Displacement Crystallization for Actinide Synthesis: Insights from Uranyl Oxalate

To address the challenge of actinide crystallization in systems with a low chemical potential, solvent displacement crystallization (SDC) techniques are applied to synthesize uranyl oxalate in a series of alcohols with varying solvent polarity. This work demonstrates the simplicity of applying SDC to actinides and indicates that solvent polarity affects crystallizations. Uranyl oxalate trihydrate was synthesized from methanol, ethanol, 1-propanol, and isopropanol as additive solvents, with characterization indicating an absence of solvent influence on the bulk structure. The choice of solvent did cause changes to the observed morphology and particle size. Additionally, the total yield of uranyl oxalate was found to decrease with increasing solvent polarity. These data support the use of SDC techniques for the crystallization of high-solubility actinide compounds.

Anions↗
DOE OSTI2023

Probing the atomically diffuse interfaces in Pd@Pt core-shell nanoparticles in three dimensions

Deciphering the three-dimensional atomic structure of solid-solid interfaces in core-shell nanomaterials is the key to understand their catalytical, optical and electronic properties. Here, we probe the three-dimensional atomic structures of palladium-platinum core-shell nanoparticles at the single-atom level using atomic resolution electron tomography. We quantify the rich structural variety of core-shell nanoparticles with heteroepitaxy in 3D at atomic resolution. Instead of forming an atomically-sharp boundary, the core-shell interface is found to be atomically diffuse with an average thickness of 4.2 Å, irrespective of the particle’s morphology or crystallographic texture. The high concentration of Pd in the diffusive interface is highly related to the free Pd atoms dissolved from the Pd seeds, which is confirmed by atomic images of Pd and Pt single atoms and sub-nanometer clusters using cryogenic electron microscopy. These results advance our understanding of core-shell structures at the fundamental level, providing potential strategies into precise nanomaterial manipulation and chemical property regulation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Effect of growth dynamics on the structural, photophysical and pseudocapacitance properties of famatinite copper antimony sulphide colloidal nanostructures (including nanosheets)

Facile phase selective synthesis of copper antimony sulphide (CAS) nanostructures is important because of their tunable photoconductive and electrochemical properties. In this study, off-stoichiometric famatinite phase CAS (fCAS) quasi-spherical and quasi-hexagonal colloidal nanostructures (including nanosheets) of sizes, 2.4–18.0 nm were grown under variable conditions of temperature (60–200 °C), time and oleylamine capping ligand concentration using copper(II) acetylacetonate and antimony(III) diethyldithiocarbamate precursors. Data from powder X-ray diffraction, Raman spectroscopy and high-resolution scanning/transmission electron microscopy confirm the tetragonal structure of the famatinite phase. X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy data suggest a correlation of particle size, morphology and composition of the off-stoichiometric fCAS nanostructures with growth temperature and time, and oleylamine concentration. The off-stoichiometric Cu 3-a Sb 1+b S 4±c (a, b, c – mole fractions) nanostructures being severely copper-deficient and antimony-rich, exhibit shallow-lying acceptor copper vacancy states, deep-lying donor states of antimony interstitials, sulphur vacancies and antimony-copper antisites and shallow-lying acceptor surface trapping states. Further, these electronic states are likely implicated in tunable UV-visible absorption and bandgaps between 2.3 and 2.8 eV, and broad visible-NIR photoluminescence with fast recombination of radiative lifetimes between 0.2 and 6.2 ns, confirmed from absorption, steady-state and time-resolved photoluminescence spectroscopies. Additionally, cyclic voltammetry and electrochemical impedance spectroscopy confirm that electrodes of the fCAS nanostructures display slightly variable pseudocapacitance of charge-storage primarily via possible sodium ion intercalation with a high specific capacitance of ~84 F g -1 obtained at a scan rate of 5 mV s -1 . Overall, these results show the influence of composition, in particular point defects, phase quality and morphology on the optical and pseudocapacitance properties of fCAS nanostructures, suitable as solar absorbers or electrodes for energy storage devices.

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

Continuous flow photochemical synthesis of metal–ceramic composite microparticles

We developed a UV-assisted microfluidic system to synthesize FeCrAl–Al 2 O 3 composite microparticles for additive manufacturing. Here, the system ensures precise particle size, morphology, and elemental distribution control. Increasing the dispensing pressure while keeping the oil flow rate constant resulted in larger microparticles. Laser fusing revealed FeCrAl and Al 2 O 3 phases, showing their potential as feedstocks for 3D printed heterogeneous materials such as FeCrAl/Al 2 O 3 bi-phase materials.

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

A quantitative imaging framework for lithium morphology: Linking deposition uniformity to cycle stability in lithium metal batteries

Characterizing the morphology of lithium (Li) is crucial for developing long-lasting lithium metal batteries. It is well established that more uniform Li deposition correlates with better cell performance. Li morphology is often characterized through qualitative analysis of scanning electron microscopy (SEM) images; however, there are no widely accepted metrics to quantitatively describe deposition uniformity. Here, we propose a framework to quantify uniformity through SEM image analysis via the index of dispersion (ID) metric, which is defined and presented in the context of Li metal batteries. We also explore experimental impacts of sampling protocols onIDmeasurements. Our results demonstrate that theIDmetric is highly sensitive to variations in deposition uniformity, including the coexistence and uniformity of multiple morphologies, uniformity within a single morphology, and particle size distribution uniformity. Furthermore, it is demonstrated that uniformity, as measured by theID, can be related to the average potential of Li||Li symmetric cells over cycling. Higher capacity cycling leads to more pronounced changes in bothIDand average cell potential. Local minima/maxima are found consistently in bothIDand average cell potential immediately before cells short-circuit, which we suggest may indicate a collapse of the microstructure prior to failure. We put forward this framework as a more robust approach to quantify Li deposition uniformity, advancing the development of Li metal batteries that are safer and longer lasting.

Science & Technology - Other Topics↗
DOE OSTI2022

Analysis of Dust Samples Collected from a Near-Marine East Coast ISFSI Site ("Site C")

In June of 2022, dust samples were collected from the surface of an in-service spent nuclear fuel dry storage canister during an inspection at an Independent Spent Fuel Storage Installation. The site is anonymous but is a near-marine or brackish water east coast location referred to here as "Site C". The purpose of the sampling was to assess the composition and abundance of the soluble salts present on the canister surface, information that provides a metric for potential corrosion risks. Following collection, the samples were delivered to Sandia National Laboratories for analysis. At Sandia, the soluble salts were leached from the dust and quantified by ion chromatography. In addition, subsamples of the dust were taken for scanning electron microscopy to determine the particle sizes, morphology, and mineralogy of the dust and salts. The results of those analyses are presented in this report.

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

Interrogating organo-mineral interactions by Py-GC/MS and ToF-SIMS

Soil organic matter (SOM) is crucial to soil fertility and agricultural sustainability in the face of climate change, and organo-mineral interactions are a key mechanism for stabilizing SOM. The stability of mineral-associated organic matter (MAOM) can be approximated by the strength of bonds between biomolecules and mineral surfaces. We hypothesized that factors such as mineral reactivity and solution pH would impact bonding strength. To test these factors, sorption isotherms were performed on minerals differing in particle size, morphology, and reactivity (quartz, goethite, gibbsite, kaolinite, montmorillonite), under two pH conditions (4 and 6), and across a range of tannic acid concentration (0-1400 ppm). The quantity and quality of organo-mineral bonds was assessed by quantifying post-sorption solution compounds using an absorbance plate reader and assessing the thermal energy needed to break bonds using evolved gas analysis (EGA) on a pyrolysis gas chromatograph-mass spectrometer (Py-GC/MS). Organo-mineral surfaces were also interrogated using Time-of-flight secondary ion mass spectrometry (ToF-SIMS). Sorption experiments revealed an asymptotic relationship between sorbed tannic acid and increasing initial concentrations which suggests our concentration range saturated available mineral surfaces. Results indicated that mineral identity, chiefly surface area and native pH, impacted the amount of compound sorbed to mineral surfaces. Evolved gas analyses of organo-mineral samples uncovered increased thermal stability of sorbed compounds compared to our tannic acid standard particularly on the iron oxide, goethite. ToF-SIMS revealed that goethite surface ions were covered by increasing concentrations of adsorbed tannic acid with the replacement of chlorine and sulfate ions by tannic acid related ions. Our results indicate that Py-GC/MS and ToF-SIMS are useful techniques to determine the nature and strength of organo-mineral bonds and are steppingstones to understanding controls on carbon sequestration in terrestrial systems.

58 GEOSCIENCES↗
DOE OSTI2023

Improvement of screen-printable metallization paste for low-cost silicon solar cells utilizing silver coated copper powders

This aims of this project were to develop low-cost screen-printable Ag|Cu metallization, as alternative to Ag paste, for contacting PERC solar cells with transparent emitter for high performance and reliability. The intended goal was to achieve 81% fill factor with a screen-printable Ag|Cu paste alternative. This was attempted through a three strand approach including Ag|Cu formulation by SVMT, production using cavitation technology by ACI and contact formation through the understanding of (i) the liquid phase sintering of the nano/macro particles of Ag|Cu to achieve bulk metal with very low series resistance, (ii) optimization of contact firing to avoid penetration of Cu into the silicon bulk, and finally (iii) proper analysis to quantify the contributions of each resistance component and keep the total series resistance at 0.2 Ω-cm2, which would result in high fill factor of 81% by UNC Charlotte. The objectives also involved i) the implementation of glass frit with Cu metal that will etch through the ARC for low contact resistance and adhesion, ii) development of Ag|Cu pastes with the optimized glass frit, iii) investigation of the impact of Cu particle size, morphology and loading on the gridline resistance, iv) narrow gridline screen designs along with narrow gridline prints, v) development of fast belt speeds of up to 375 inches per minute (ipm) sintering, and vi) stability study on Ag|Cu contact to high performance and reliability.

14 SOLAR ENERGY↗
DOE OSTI2025

Developing tools and process controls to manufacture energy-efficient powders for additive manufacturing feedstocks: Computational analysis of metal powder manufacturing via machining

Traditionally, metal powders have been produced through methods such as grinding, atomization, and electrolysis. In contrast to these techniques, Metal Powder Works, Inc. has pioneered a methodology based on metal cutting. This innovative approach utilizes a vibrating cutting tool to machine metal particles, in the form of chips, from a workpiece. This technique allows for control of powder particle size, morphology, and avoids any thermally induced material changes. This collaboration aims to elucidate metal cutting characteristics and assess performance on tough materials like Inconel alloys. Computational models, using FEA and SPH techniques, will be developed initially, focusing on aluminum alloy (Al 7075-T6) for studying mesh sensitivity, cutting forces, and chip morphology.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2025

Developing tools and process controls to manufacture energy-efficient powders for additive manufacturing feedstocks

Traditionally, metal powders have been produced through methods such as grinding, atomization, and electrolysis. In contrast to these techniques, Metal Powder Works, Inc. has pioneered a methodology based on metal cutting. This innovative approach utilizes a vibrating cutting tool to machine metal particles, in the form of chips, from a workpiece. This technique allows for control of powder particle size, morphology, and avoids any thermally induced material changes. This collaboration aims to elucidate metal cutting characteristics and assess performance on tough materials like Inconel alloys. Computational models, using FEA and SPH techniques, will be developed initially, focusing on aluminum alloy (Al 7075- T6) for studying mesh sensitivity, cutting forces, and chip morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Influence of soluble oligomeric aluminum on precipitation in the Al-KOH-H2O system

The role of oligomeric aluminate (Al(OH)4-) species in the precipitation of aluminum phases such as gibbsite (a-Al(OH)3) from aqueous hydroxide solutions remains unclear and difficult to probe directly, despite its importance to developing accurate predictions of Al solubility in highly alkaline systems. Precipitation in this system entails a transition from predominantly tetrahedrally coordinated Al species in solution to octahedrally coordinated Al in gibbsite. Here we report a quantitative study of dissolved Al in the Al-KOH-H2O system using a combination of molecular spectroscopies. We established a relationship between changes in 27Al NMR chemical shifts and the relative intensity of Raman vibrational bands, indicative of variations in the ensemble speciation of Al in solution, and the formation of unique contact ion pair interactions with the aluminate dimer, Al2O(OH)62 . A strong correlation between the extent of Al oligomerization and the amount of solvated Al was demonstrated by systematically varying the KOH:Al molar ratio. The concentration of dissolved oligomeric Al in solution also directly impacted the particle size and morphology of gibbsite; high concentrations of dimeric Al2O(OH)62-, yielded smaller and more numerous anhedral to subhedral gibbsite particles, while low concentrations yielded fewer and larger euhedral gibbsite platelets. The collective observations suggest a key role of the Al2O(OH)62- dimer in promoting gibbsite precipitation from solution, where the potassium ion-paired dimer possibly catalyzes a more rapid transformation of Al coordination from tetrahedral in solution to octahedral in gibbsite.

Dembowski, Mateusz↗
DOE OSTI2023

Effects of particle size, shape and loading rate on the normal compaction of an advanced granular ceramic

Compaction behavior of granular materials is influenced by strain rate, particle size, and shape. In this report, boron carbide powders with different particle sizes under uni-axial strain conditions are studied using quasi-static compression, dynamic Kolsky bar experiments and normal plate impact. A rounded powder is compacted to investigate the effect of particle shape. The normal plate impact technique is an excellent tool in characterization of powder compaction behavior up to strain rates of ~10 5 s -1 . From our experiments, granular boron carbide shows a highly compressible behavior with significant volume compaction. Constitutive responses are obtained for four powders. Particle fracture is identified as key deformation mechanism. Dynamic loading introduces more particle fragmentation than quasi-static loading. Morphological characterization of particle shapes shows that the deformation from powder compaction alters the particle shape distribution, which is also rate-dependent. Particle size, shape and strain rate effects on the normal stress are discussed accordingly.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Modeling Solution Drying by Moving a Liquid-Vapor Interface: Method and Applications

A method of simulating the drying process of a soft matter solution with an implicit solvent model by moving the liquid-vapor interface is applied to various solution films and droplets. For a solution of a polymer and nanoparticles, we observe “polymer-on-top” stratification, similar to that found previously with an explicit solvent model. Furthermore, “polymer-on-top” is found even when the nanoparticle size is smaller than the radius of gyration of the polymer chains. For a suspension droplet of a bidisperse mixture of nanoparticles, we show that core-shell clusters of nanoparticles can be obtained via the “small-on-outside” stratification mechanism at fast evaporation rates. “Large-on-outside” stratification and uniform particle distribution are also observed when the evaporation rate is reduced. Polymeric particles with various morphologies, including Janus spheres, core-shell particles, and patchy particles, are produced from drying droplets of polymer solutions by combining fast evaporation with a controlled interaction between the polymers and the liquid-vapor interface. Our results validate the applicability of the moving interface method to a wide range of drying systems. The limitations of the method are pointed out and cautions are provided to potential practitioners on cases where the method might fail.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Developing of nano sized fibrous eutectic silicon in hypereutectic Al–Si alloy by laser remelting

Laser surface melting followed by rapid solidification is an effective means to produce very fine microstructures with desirable surface properties because of the high rates of cooling associated with it. In the present study, the effect of rapid cooling on the silicon particle size, distribution, and morphology of hypereutectic Al–17wt.%Si and Al–20wt.%Si alloys have been investigated. A continuous-wave CO2 laser of wavelength 10.6 μm and a Trumpf Yb-YAG disk laser of wavelength 1.030 μm were used with a beam diameter of 1 mm and scanning speeds ranging from 5 to 100 mm/s. Rapid solidification increased the solubility of silicon in aluminum to approximately 5wt% and induced non-equilibrium hypoeutectic microstructures comprising large volume fractions of primary α-Al dendrites and ultrafine Al–Si eutectic of lamellar morphology. Both α-Al dendrites and the silicon particle sizes were significantly reduced from micron to nanoscale level. The morphology of silicon particles is modified from massive polygonal and plate-like to a mixture of fine fakes with round corners, feathery and fibrous, or a coral-like and thread-like structure. The eutectic silicon size and the interlamellar spacing were reduced to 30 and 10 nm, respectively. Furthermore, most of the silicon crystals in the eutectic region and the aluminum dendrites contained a significant number of twins which were considered as an essential contributor to the mechanism of growth and branching. Microhardness values increased two to threefold due to the refinement of the microstructural constituent.

42 ENGINEERING↗