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DOE OSTI2024

Phase Transitions in Organic and Organic/Inorganic Aerosol Particles

The phase state of aerosol particles can impact numerous atmospheric processes, including new particle growth, heterogeneous chemistry, cloud condensation nucleus formation, and ice nucleation. In this article, the phase transitions of inorganic, organic, and organic/inorganic aerosol particles are discussed, with particular focus on liquid-liquid phase separation (LLPS). The physical chemistry that determines whether LLPS occurs, at what relative humidity it occurs, and the resultant particle morphology is explained using both theoretical and experimental methods. The known impacts of LLPS on aerosol processes in the atmosphere are discussed. Finally, potential evidence for LLPS from field and chamber studies is presented. By understanding the physical chemistry of the phase transitions of aerosol particles, we will acquire a better understanding of aerosol processes, which in turn impact human health and climate.

Chemistry↗

DOE OSTI2024

Modeling aerosol transmission spectra from n(λ) and k(λ) infrared optical constants measurements of organic liquids and solids

The effects of light scattering and refraction play significantly different roles for aerosols than for bulk materials, making it challenging to identify aerosolized chemicals using traditional spectral methods or spectral reference libraries. Due to a potentially infinite number of particle morphologies, sizes, and compositions, constructing a database of laboratory-measured aerosol spectra is not a practical solution. Here, as an alternative approach, the measured n / k optical vectors of two example organic materials (diethyl phthalate and D-mannitol) are used in combination with particle absorption / scattering theory (Mie theory and FDTD) and the Beer-Lambert law to generate a series of synthetic infrared transmission / scattered light spectra. The synthetic spectra show significant differences versus simple slab transmission spectra, even for small changes in particle size (e.g., 5 vs. 10 µm) for both single particles and ensembles, potentially serving as useful reference data for aerosol sensing. For spherical single particles with diameters of 1 to 10 µm, FDTD simulations predict changes in the magnitudes of spectral shifts and the shapes of the peaks vs. particle size with only small deviations from Mie theory predictions, yet reliably capture the direction of the shifts. Typical spectral peak shifts in the longwave infrared correspond to Δλ ∼0.20 µm (∼34 cm -1 ) when compared to corresponding slab transmission spectra. Additionally, synthetic spectra generated from the n / k values derived using two different methods (KBr pellet transmission and single-angle reflectance) are compared using the Mie theory model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2015

Design of a Thermal Precipitator for the Characterization of Smoke Particles from Common Spacecraft Materials

A thermal precipitator (TP) was designed to collect smoke aerosol particles for microscopic analysis in fire characterization research. Information on particle morphology, size and agglomerate structure obtained from these tests supplements additional aerosol data collected. Modeling of the thermal precipitator throughout the design process was performed with the COMSOL Multiphysics finite element software package, including the Eulerian flow field and thermal gradients in the fluid. The COMSOL Particle Tracing Module was subsequently used to determine particle deposition. Modeling provided optimized design parameters such as geometry, flow rate and temperatures. The thermal precipitator was built and testing verified the performance of the first iteration of the device. The thermal precipitator was successfully operated and provided quality particle samples for microscopic analysis, which furthered the body of knowledge on smoke particulates. This information is a key element of smoke characterization and will be useful for future spacecraft fire detection research.

Smoke↗

DOE OSTI2025

Electrodepositing Textured Sn Film as a Highly Reversible Anode for Aqueous Batteries

Electrodepositing metal materials in large capacity, at low potential, and with high reversibility serves as the foundation for any aqueous rechargeable battery chemistry to realize the promises of high energy, low cost, and high safety. However, such a foundation is not solid because of the natural tendency of metals to form irregular, nonplanar, and often dendritic morphologies during electrochemical crystallization, which is further amplified in an acidic environment due to the faster kinetics of the coupled proton and mass-transport processes between hydrated metal ions and free metal atoms. As a typical representative, tin metal (Sn 0 ) has potential to achieve high energy in acidic batteries, but its nonuniform large-particle morphology, obtained from traditional electrodeposition, leads to dead Sn 0 formation and deteriorating reversibility, accompanied by the sustained hydrogen evolution reaction (HER) and active Sn 0 loss. Here, in this study, we report quaternary onium salts as effective interfacial cocations that, via selective adsorption, steadily texturize Sn 0 deposition along the (211) plane, which is intrinsically inert to the HER, thus regulating the film deposition process by favoring the formation of planar Sn 0 film. Such Sn 0 film brings exceptional reversibility in acidic electrolytes, which translates into sustained cycling stability at applicable areal capacities in both anode-half cells (similar to 1500 deposition/dissolution cycles at 5 mAh cm -2 ) and full cells (350 charge/discharge cycles at 5 mAh cm -2 ). Textured electrodeposition with intrinsic HER-suppression capability provides a universal solution for diverse metal anode materials in rechargeable energy-dense aqueous batteries.

Sn metal↗

DOE OSTI2023

Predicting Outcomes of Nanoparticle Attachment by Connecting Atomistic, Interfacial, Particle, and Aggregate Scales

Predicting nanoparticle aggregation and attachment phenomena requires a rigorous understanding of the interplay among crystal structure, particle morphology, surface chemistry, solution conditions, and interparticle forces, yet no comprehensive picture exists. We used an integrated suite of experimental, theoretical, and simulation methods to resolve the effect of solution pH on the aggregation of boehmite nanoplatelets, a case study with important implications for the environmental management of legacy nuclear waste. Real-time observations showed that the particles attach preferentially along the (010) planes at pH 8.5 and the (101) planes at pH 11. To rationalize these results, we established the connection between key physicochemical phenomena across the relevant length scales. Starting from molecular-scale simulations of surface hydroxyl reactivity, we developed an interfacial-scale model of the corresponding electrostatic potentials, with subsequent particle-scale calculations of the resulting driving forces allowing successful prediction of the attachment modes. Finally, we scaled these phenomena to understand the collective structure at the aggregate-scale . Here, our results indicate that facet-specific differences in surface chemistry produce heterogeneous surface charge distributions that are coupled to particle anisotropy and shape-dependent hydrodynamic forces, to play a key role in controlling aggregation behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Photosynthesis of a Photocatalyst: Single Atom Platinum Captured and Stabilized by an Iron(III) Engineered Defect

Single atom (SA), noble metal catalysts are of interest due to high projected catalytic activity while minimizing cost. Common issues facing many synthesis methodologies include complicated processes, low yields of SA product, and production of mixtures of SA and nanoparticles (NPs). Herein we report a simple, room-temperature synthesis of single Pt-atom decorated, anatase Fe-doped TiO 2 particles that leverages the Fe dopant as an engineered defect site to photodeposit and stabilize atomically dispersed Pt. Both particle morphology and Fe dopant location are based on thermodynamic principles (Gibbs-Wulff construction). CO-DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) reveals absence of bridge-bonded CO signal, confirming atomically dispersed Pt. XAS (x-ray absorption spectroscopy) of both Pt and Fe indicates Fe-O-Pt bonding that persists through catalytic cycling. Mass balance indicates Pt loading on single particles is 2.5 wt% Pt; single Pt-atom decorated nanoparticle yield is 17%. Pt containing particles show more than an order-of-magnitude increased photo-oxidation efficiency relative to particles containing only Fe. High single-atom-Pt yield, ease of synthesis, and high catalytic activity demonstrate the utility and promise of this method. In conclusion, the principles of this photodeposition synthesis allow for its generalizability towards other SA metals of catalytic interest.

36 MATERIALS SCIENCE↗

NASA NTRS1984

Thermoelectric and morphological effects of Peltier pulsing on directional solidification of eutectic Bi-Mn

Extensive in situ thermal measurements using Peltier Interface Demarcation (PID) during directional solidification of eutectic Bi/MnBi were carried out. Observations indicate that significant thermal transients occur throughout the sample as a result of the Peltier pulsing. The contributions of the Peltier, Thomson, and Joule heats were separated and studied as a function of pulse intensity and polarity. The Joule and the combined Peltier and Thomson thermal contributions were determined as a function of time during and after the current pulses, close to the solid/liquid interface. Variations of the Bi/MnBi particle morphology clearly reveal the interface shape, changes in interface velocity, meltback, and temporary loss of cooperative growth, as a result of the pulsing.

Silberstein, R. P.↗

DOE OSTI2026

Influence of aluminum source and Ni/Al ratio in a batch stirred tank reactor on the structure, morphology, and electrochemical performance of Ni-rich NMA cathodes

Here, the structural, morphological, and electrochemical performance of Ni-rich LiNi 0.9 Mn 0.05 Al 0.05 O 2 (955NMA) and LiNi 0.85 Mn 0.05 Al 0.1 O 2 (85,510) cathodes strongly depends on the properties of their hydroxide precursors. Ni-Mn-Al hydroxide precursors were synthesized through controlled co-precipitation in a batch stirred tank reactor, where pH, reaction time, metal-ion feed rate, aluminum source, and aluminum concentration were systematically varied to tailor particle morphology, phase composition, and dopant distribution. Two aluminum sources, aluminum nitrate and sodium aluminate produced two distinct hydroxide precursors NMA(OH) 2 -1 and NMA(OH) 2 -2, which were lithiated to form LiNMA1 (Li 0.992 [Ni 0.905 Mn 0.049 Al 0.046 ]O 2 ) and LiNMA2 (Li 0.990 [Ni 0.850 Mn 0.047 Al 0.103 ]O 2 ). Structural and compositional analyses revealed that aluminum incorporation and phase formation in Ni–Mn–Al hydroxides are governed by local supersaturation and interfacial growth kinetics. Rapid dilute aluminum addition produced aluminum-free β-phase hydroxides, intermediate conditions generated mixed α/β phases, whereas slow concentrated dosing enabled uniform aluminum incorporation and stabilization of the β-phase structure. LiNMA1 delivers a high initial discharge capacity of 223 mAhg −1 but significant capacity fading with 67% retention after 100 cycles, associated with structural instability. In contrast, LiNMA2 delivers a lower initial capacity 172 mAhg −1 yet excellent cycling stability 91% retention, attributed to improved TM–O framework stability and reduced cation disorder.

Capacity↗

DOE OSTI2026

Paramagnetic Properties of Rare Earth Hydroxides, Oxalates, and Dibutyl Phosphates

Magnetic separations present a promising approach for the recovery of rare earth (RE) elements from mixtures, particularly when coupled with precipitation techniques that enhance process efficiency and selectivity. However, the magnetic properties of RE materials typically encountered in the separations industry are not well characterized. Here, we synthesized a series of RE materials, combining four REs – praseodymium (Pr), neodymium (Nd), terbium (Tb), and dysprosium (Dy) – with three precipitating agents – hydroxide, oxalate, and dibutyl phosphate. All materials showed typical paramagnetic behavior consistent with the Curie-Weiss law. At low temperatures, we observed weak antiferromagnetic correlations, which were more pronounced for the lighter RE ions (Pr, Nd). Particle morphology and crystallography analyses showed that the dibutyl phosphates were well-ordered metal-organic frameworks, the oxalates were crystals with mixed hydration states, and the hydroxides were mostly amorphous. Regardless of the degree of crystallinity, the effective magnetic moments aligned well with theoretical estimates based on Hund's rules and 4f electron configurations of the corresponding RE ions. For a given RE ion, the magnetophoretic response was thus determined by the size of the particles rather than specific metal-ligand coupling, with dibutyl phosphate promoting the formation of larger crystals that were the most strongly attracted to magnets.

Wang, Qingpu (ORCID:0000000156041571)↗

DOE OSTI2020

A scalable approach of using biomass derived glycerol to synthesize cathode materials for lithium-ion batteries

Glycerol, a main byproduct of biodiesel, was used as the fuel agent in a scalable flame-assisted spray pyrolysis approach to synthesize micron-size cathode materials. Single droplet combustion, particle morphology, and electrochemical performance were examined considering the effects of salt concentration, water addition, and post-annealing time on synthesizing Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 (NCM111) cathode materials. Single droplet tests showed that a sufficient amount of water in the glycerol-based precursor could delay droplet inflation and ignition. Moreover, using a two-fluid atomization nozzle, spray tests demonstrated that adding water would result in less wrinkled and more uniform particles. Nevertheless, increasing water proportion in the precursor could reduce the reaction heat, resulting in that samples prepared with water addition needed longer post-annealing time to improve their electrochemical performance. Using the precursor without water, the best performed NCM111 cathode material was synthesized with only 2 h of post-annealing. It has a discharge capacity of 163.3 mAh/g at 0.1C and 85.5% capacity retention at 1C after 100 cycles. Furthermore, the current work confirmed the capability of using glycerol as a sustainable fuel agent to synthesize NCM111 cathode materials, and also provided basic conditions for the development of large-scale production in the future.

25 ENERGY STORAGE↗

NASA NTRS2026

Satellite Optical Remote Sensing of Clouds and Aerosols: From Particle Single-Scattering and Gaseous Absorption Through Radiative Transfer to Retrieval Products

Clouds and aerosols are fundamental regulators of Earth’s radiation budget and climate system, influencing both solar and terrestrial radiation through scattering, absorption, and emission processes. Accurate characterization of their physical and radiative properties from space requires a rigorous understanding of particle single-scattering, gaseous absorption, and radiative transfer in the atmosphere, as well as reliable inversion methods. This review synthesizes the physical foundations and algorithmic implementations of satellite-based passive optical remote sensing of clouds and aerosols, spanning the ultraviolet to thermal infrared spectral range. Beginning with electromagnetic scattering theory and state-of-the-art methods for computing single-scattering by nonspherical particles and computationally efficient methods for accounting for atmospheric absorption, we discuss the radiative transfer framework underpinning cloud and aerosol retrievals. The connection between single-scattering and multiple-scattering is rigorously formulated. We then summarize operational and research-grade retrieval techniques, including cloud masking and thermodynamic phase determination, CO₂ slicing for cloud-top pressure, the Nakajima-King shortwave bi-spectral, and infrared split-window approaches for cloud optical thickness and effective particle size, inversion algorithms for determining aerosol properties from multi-spectral and/or multi-angle radiometric and polarimetric measurements, and active-passive sensing synergy. Examples of the global cloud and aerosol climatologies are illustrated using observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging SpectroRadiometer (MISR). Furthermore, the unique strengths of active remote sensing techniques based on spaceborne lidar observations are briefly elaborated in the context of studying ice clouds composed of randomly and horizontally oriented ice crystals, which is a significant challenge for conventional passive remote sensing techniques. By connecting physical theory to practical retrievals, this review highlights both the maturity of current methodologies and the remaining challenges in reducing uncertainties in particle morphology, vertical structure, absorption, and aerosol-cloud interactions. Furthermore, the impact of artificial intelligence (AI) on atmospheric remote sensing is briefly addressed.

Aerosols↗

DOE OSTI2024

Advanced Functional Membranes for Noble Gas Management: Fabrication and Testing of Membranes on Porous Support

We selected several porous materials including PNW-24, CC3, SAPO-34, SAPO-56 and PNW-6, as the basis for fabricating membranes for Kr/Xe separation. Initially, we synthesized powder samples of the candidates and confirmed their crystallinity and morphology with X-ray diffraction and microscopy. In the case of PNW-24 and PNW-6, we further confirmed its Xe selectivity through Xe and Kr adsorption experiments, while we relied on literature reports for CC3, SAPO-34 and SAPO-56. We subsequently proceeded to fabricate membranes on porous alumina supports using techniques such as seeded-assisted secondary growth, in-situ growth and solution-processed method. PXRD on the membranes verified that the structures were well-grown on the surface of alumina support, while SEM provided visual confirmation of particle morphology. Importantly, defects were not visually observed in the fabricated membranes, which was further verified with pressure retention tests. We analyzed the separation performance of the synthesized membranes using a dilute gas mixture comprising of xenon, krypton and argon. We focused on PNW-6 to optimize the synthesis reaction time and study the effects of time on gas separation. While more research is necessary to reach a comprehensive conclusion, in alignment with our milestones, we have successfully achieved our goals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2000

Global to Microscale Evolution of the Pinatubo Volcanic Aerosol Derived from Diverse Measurements and Analyses

We assemble data on the Pinatubo aerosol from space, air, and ground measurements, develop a composite picture, and assess the consistency and uncertainties of measurement and retrieval techniques. Satellite infrared spectroscopy, particle morphology, and evaporation temperature measurements agree with theoretical calculations in showing a dominant composition of H2SO4-H20 mixture, with H2SO4 weight fraction of 65-80% for most stratospheric temperatures and humidities. Important exceptions are (1) volcanic ash, present at all heights initially and just above the tropopause until at least March 1992, and (2) much smaller H2SO4 fractions at the low temperatures of high-latitude winters and the tropical tropopause. Laboratory spectroscopy and calculations yield wavelength- and temperature-dependent refractive indices for the H2SO4-H20 droplets. These permit derivation of particle size information from measured optical depth spectra, for comparison to impactor and optical-counter measurements. All three techniques paint a generally consistent picture of the evolution of R(sub eff), the effective radius. In the first month after the eruption, although particle numbers increased greatly, R(sub eff) outside the tropical core was similar to preeruption values of approx. 0.1 to 0.2 microns, because numbers of both small (r < 0.2 microns) and large (r > 0.6 microns) particles increased. In the next 3-6 months, extracore R(sub eff) increased to approx. 0.5 microns, reflecting particle growth through condensation and coagulation. Most data show that R(sub eff) continued to increase for about 1 year after the eruption. R(sub eff) values up to 0.6 - 0.8 microns or more are consistent with 0.38 - 1 micron optical depth spectra in middle to late 1992 and even later. However, in this period, values from in situ measurements are somewhat less. The difference might reflect in situ undersampling of the very few largest particles, insensitivity of optical depth spectra to the smallest particles, or the inability of flat spectra to place an upper limit on particle size. Optical depth spectra extending to wavelengths lambda > 1 micron are required to better constrain R(sub eff), especially for R(sub eff) > 0.4 microns. Extinction spectra computed from in situ size distributions are consistent with optical depth measurements; both show initial spectra with lambda(sub max) <= 0.42 microns, thereafter increasing to 0.78 <= lambda(sub max) <= 1 micron. Not until 1993 do spectra begin to show a clear return to the preeruption signature of lambda(sub max) <= 0.42 microns. The twin signatures of large R(sub eff) (> 0.3 microns) and relatively flat extinction spectra (0.4 - 1 microns) are among the longest-lived indicators of Pinatubo volcanic influence. They persist for years after the peaks in number, mass, surface area, and optical depth at all wavelengths <= 1 microns. This coupled evolution in particle size distribution and optical depth spectra helps explain the relationship between global maps of 0.5- and 1.0-micron optical depth derived from the Advanced Very High Resolution Radiometer (AVHRR) and Stratospheric Aerosol and Gas Experiment (SAGE) satellite sensors. However, there are important differences between the AVHRR and SAGE midvisible optical thickness products. We discuss possible reasons for these differences and how they might be resolved.

Russell, P. B.↗

DOE OSTI2024

Controlling the Crystal Packing and Morphology of Metal–Organic Macrocycles through Side-Chain Modification

Supramolecular nanotubes constructed from the self-assembly of conjugated metal–organic macrocycles provide a unique collection of materials properties, including solution processability, porosity, and electrical conductivity. Here we show how small modifications to the macrocycle periphery subtly alter the noncovalent interactions governing self-assembly, leading to large changes in crystal packing, crystal morphology, and materials properties. Specifically, we synthesized five distinct copper-based macrocycles that differ in either the steric bulk, polarity, or hydrogen-bonding ability of the peripheral side chains. We show that the electrical conductivity of these macrocycles is highly sensitive to steric bulk, decreasing by 3 orders of magnitude upon introduction of peripheral neopentyl substituents. Here, we further show that the introduction of hydrogen-bonding groups leads to more ordered packing and a dramatic increase in crystallite size. Together, these results establish side-chain engineering as a rich toolkit for controlling the packing structure, particle morphology, and bulk properties of conjugated metal–organic macrocycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Impact of Controlled Storage Conditions on the Hydrolysis and Surface Morphology of Amorphous-UO 3

The hydration and morphological effects of amorphous (A)-UO 3 following storage under varying temperature and relative humidity have been investigated. This study provides valuable insight into U-oxide speciation following aging, the U-oxide quantitative morphological data set, and, overall, the characterization of nuclear material provenance. A-UO 3 was synthesized via the washed uranyl peroxide synthetic route and aged based on a 3-factor circumscribed central composite design of experiment. Target aging times include 2.57, 7.00, 14.0, 21.0, and 25.4 days, temperatures of 5.51, 15.0, 30.0, 45.0, and 54.5 °C, and relative humidities of 14.2, 30.0, 55.0, 80.0, and 95.8% were examined. Following aging, crystallographic changes were quantified via powder X-ray diffraction and an internal standard Rietveld refinement method was used to confirm the hydration of A-UO 3 to crystalline schoepite phases. The particle morphology from scanning electron microscopy images was quantified using both the Morphological Analysis of MAterials software and machine learning. Results from the machine learning were processed via agglomerative hierarchical clustering analysis to distinguish trends in morphological attributes from the aging study. Significantly hydrated samples were found to have a much larger, plate-like morphology in comparison to the unaged controls. Predictive modeling via a response surface methodology determined that while aging time, temperature, and relative humidity all have a quantifiable effect on A-UO 3 crystallographic and morphological changes, relative humidity has the most significant impact.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Ice Cryo-Encapsulation Balloon (Project ICEBall) Field Campaign Report

The Ice Cryo-Encapsulation Balloon (ICEBall) field campaign was designed to sample the ice crystals that compose high-altitude cirrus with a passive device. The campaign made use of a new instrument, ICEBall, which is a balloon-borne ice crystal sampling system. The ice crystal sounding system is capable of measuring ice crystal concentration, temperature, atmospheric pressure, ice crystal habit, aerosol particle morphology, and residual composition. The 3-kg instrument is carried upwards at 5 m s-1 by a high-altitude balloon. The instrument can be cut down from the balloon at any altitude up to 20 km, and the apparatus returns to the surface by parachute. Basic measurements such as temperature and pressure are recorded onboard, and high-frequency Global Positioning System (GPS) records altitude and latitude/longitude. Ice crystal concentrations are measured through the use of a high-resolution video camera mounted on the device. Ice crystals are collected through an open aperture leading to insulated collection chambers cooled with dry ice. Upon exiting the top of the cloud system, the chamber aperture is closed, and the ~1 mm3 sample cell is magnetically sealed and isolated at -78 °C, ensuring that ice particles do not sublimate or grow after collection. Once the crystals are returned to the surface, they are double-sealed and immersed at liquid nitrogen temperature in “dry-cryo shippers” before being transported back to the laboratory. Dr. Magee’s laboratory at The College of New Jersey contains a cryo-stage scanning electron microscope (SEM), which was used to interrogate the crystals and aerosol particles. The main purpose of this pilot field campaign was to provide an unprecedented level of detail on the crystal habits and ice surface complexity in mid-latitude cirrus, which may help resolve issues associated with habit identification and classification in cirrus. The ICEBall campaign was originally scheduled to run from March 28 to April 18 of 2021 at the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains observatory. The COVID-19 pandemic intervened and caused us to shift the dates of the experiment to October 16-November 6 of 2021. This period is also climatologically favorable for cirrus. The approximately six-month gap between our original field campaign dates and the actual dates afforded us the opportunity to build two new ICEBall payload instruments. These instruments were tested during an August 2021 trip to The College of New Jersey. During this field testing phase, we decided to launch the ICEBall payload upstream from the ARM SGP site with the goal of landing in the vicinity of the site. Our goal was to sample the ice crystals before the cirrus were advected over the remote-sensing instruments at the SGP site. The team assembled for the field campaign consisted of the Principle Investigator (PI) and Co-Principle Investigator (Co-PI) (Drs. Harrington and Magee), The Pennsylvania State University research scientist Dr. Alfred Moyle, and two graduate students (Ms. Marley Majetic and Gwenore Pokrifka). The team operated out of a house rented in Enid, Oklahoma. We successfully sampled seven cirrus cloud systems during the three-week field campaign (October 21, 23-26, 31, and November 1). This was a much higher success rate than either of the PIs anticipated (our goal was closer to sampling three or four cases). The balloon was typically launched from oil pads or farm fields northwest of Enid and the payload was typically retrieved somewhat north of the SGP site. We never landed directly at the SGP site, and so did not need regular access to the SGP facilities. Our greatest concern going into the field campaign was the longer-term storage of crystals in the -196°C cryo dry-shipper dewars and the subsequent transport across the country. We had tested storage and transport prior to the field campaign, but we had never stored crystals for a few weeks nor had we transported the dewars over long distances. To our great relief, the storage and transport worked flawlessly and we were able to image a large number of crystals from six of the seven cases. Working with the staff at the ARM SGP office was excellent. They not only helped us find the sources we needed for helium, liquid nitrogen, and other materials, but also helped with contacts within the Federal Aviation Administration (FAA) and Vance Air Force Base. One goal of our field project was to tie the in situ measurements of ice crystal habits to the radar signatures derived from the Ka-band ARM Zenith-pointing Radar (KAZR). Unfortunately KAZR was down for the duration of our experiment. However, the Ka-band Scanning ARM Cloud Radar (KASACR) was put into vertically pointing mode during the ICEBall campaign and those data, along with Doppler lidar measurements, have proved very useful.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2022

M2 Selective Laser Melting GRCop-42 Recycling Study

A powder recycling study was conducted to examine the effects of powder reuse on physical and mechanical properties of SLM GRCop-42. Twelve sequential builds were conducted, each reusing powder from the previous build topped off with virgin powder to fill the powder chamber. Powder morphology, particle size distribution, flowability, and chemistry were examined for each subsequent build, along with the mechanical properties of tensile and LCF specimens built with each powder batch. It was found that only powder flowability demonstrated a trend with increasing reuse, with flowability and cohesiveness generally decreasing over the course of the 12 builds. Minor variation in powder chemistry was observed throughout the study, however, the variations did not correlate with increasing powder reuse

Additive Manufacturing↗

DOE OSTI2026

Linking spout fluidization hydrodynamics to pyrolytic carbon deposition characteristics in a fluidized bed chemical vapor deposition reactor

Spout fluidized bed chemical vapor deposition (SFB-CVD) is the dominant method for producing pyrolytic carbon (PyC) coatings on tristructural-isotropic (TRISO) fuel particles, yet the relationship between gas injector design, fluidization hydrodynamics, and resulting coating quality remains poorly quantified. Here, in this work, three spout fluidized bed (SFB) nozzle geometries were designed and fabricated to empirically investigate how injector-driven changes in particle circulation influence PyC deposition. The geometries were first evaluated in a room temperature fluidization apparatus using time-resolved particle image velocimetry, which highlighted distinct differences in particle velocity fields, circulation pathways, and overall fluidization quality. Graphite versions of each injector geometry were subsequently implemented in a laboratory-scale SFB-CVD reactor to deposit PyC onto surrogate fuel kernels under similar conditions. Post-deposition characterization included particle morphology, coating thickness, porosity distribution, optical anisotropy, and microindentation mechanical testing. Overall, the results show clear differences in coating microstructure as a function of changing injector geometry, despite mechanical testing indicating comparable elastic modulus values across all coatings. This study provides one of the first fully experimental, quantitative mappings between SFB nozzle geometry, fluidization hydrodynamics, and resulting PyC coating structure. The framework established here supports rational injector design and offers a pathway toward improved coating control in future pilot- and production-scale TRISO fuel fabrication systems.

Coated particle fuel↗