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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Solution combustion synthesis of iron-based alumina nanocomposites for clean production of hydrogen from fossil fuels

Iron-based alumina nanocomposites are promising materials for microwave-assisted thermocatalytic dehydrogenation of fossil fuels, which has been proposed for the production of hydrogen with no CO2 emissions. Solution combustion synthesis (SCS) is an attractive technique for the fabrication of these materials because it has been used for synthesis of many nanoscale oxides. However, SCS can be carried out using different organic fuels and different heating equipment, and it is important to determine which fuel and heating mode generate materials with the best properties for dehydrogenation, such as maximized specific surface area. In the present work, the iron-based alumina nanocomposites were obtained by SCS using two different fuels (citric acid and glycine) and two different heating modes (a hotplate and a muffle furnace). The precursors/oxidizers were iron nitrate and aluminum nitrate. They were mixed with the fuel according to stoichiometry and dissolved in water. Heating the solution resulted in combustion synthesis. The products were characterized by X-ray diffraction analysis, Brunauer-Emmett-Teller surface area analysis, laser diffraction particle size analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The experiments have shown that the specific surface area of the iron-based alumina nanocomposites obtained by SCS can be dramatically increased by using citric acid instead of glycine, and additionally by using a muffle furnace instead of a hotplate.

Solution combustion synthesis, Nanoscale metal oxi↗
DOE OSTI2022

Onion-Like nanoparticles of the metal–organic framework UiO-66 synthesized by sequential spike crystal growth

Reproducible size and morphology of metal–organic framework (MOF) particles are essential for tuning these materials for applications like heterogeneous catalysis. Particle size measurements from electron micrographs provide information about the impact of changing synthetic parameters on MOF growth, but reported data are usually limited to averages and statistical distributions. Further elucidating synthetic control parameters could facilitate studies of facet-dependent and non-classical growth mechanisms. Here, in this work, phase-pure nanoparticles of the MOF UiO-66 were synthesized using alternating spikes of zirconium and hafnium-based nodes, forming an onion-like structure with alternating layers of Zr-UiO-66 and Hf-UiO-66. In conventional, bright-field transmission electron micrographs, Hf-UiO-66 and Zr-UiO-66 layers appeared darker and lighter, respectively. Alternating layers of Hf-UiO-66 and Zr-UiO-66 were also apparent in elemental maps obtained using scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy. Average particle sizes increased monotonically with each spike, and no Zr-only or Hf-only particles were observed after the first spike, indicating that new material was consistently incorporated onto existing seeds. Surface area of the onion-like particles and their uptake of Ni 2+ from solution were both between the values measured for Zr-UiO-66 and Hf-UiO-66. Results demonstrate the use of sequential spikes of nodes in monitoring crystal growth in MOFs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Quantification of Inactive Lithium and Solid–Electrolyte Interphase Species on Graphite Electrodes after Fast Charging

Rapid charging of Li-ion batteries is limited by lithium plating on graphite anodes, whereby Li+ ions are reduced to Li metal on the graphite particle surface instead of inserting between graphitic layers, which directly contributes to cell capacity loss because of the low reversibility of the Li plating/stripping process. Furthermore, precisely identifying the onset and amount of Li plating is therefore vital in order to remedy these issues. We demonstrate a titration technique with a detection limit of 20 nmol (5 × 10 –4 mAh) of Li that can be used to quantify inactive Li that remains on the graphite electrode after fast charging. The titration is extended to quantify the total amount of solid carbonate species and lithium acetylide (Li 2 C 2 ) within the solid–electrolyte interphase (SEI), and electrochemical modeling is used to determine the Li plating exchange current density (10 A/m 2 ) and stripping efficiency (65%) of plated Li metal on graphite. These techniques provide a highly accurate measure of the onset of Li plating and quantitative insight into graphite SEI evolution during fast charging.

25 ENERGY STORAGE↗
DOE OSTI2023

Metal-Complex Inks for Lower Cost and Improved Passivation for Silicon Photovoltaic Metallization

This contribution introduces the silicon PV community to screen-printable metal-complex inks that potentially will reduce Ag usage in Si PV metallization to one-quarter and costs to one-third that of traditional particle-based pastes while also improving passivation. Metal-complex inks are formulated using a Tollen's reaction to produce inks with a high percentage of diamminesilver (I) cations (22 wt %) in a solution of acetate and formate anions. When printed and dried labile ammonia ligands evaporate, leaving behind silver cations which, when reduced by formate anions and acetic acid, plate out silver and silver acetate. When annealed to just 300 degrees C a dense metallic silver film forms with excellent conductivity, and adhesion to silicon. When compared to traditional particle-based screen-printing pastes, the metal-complex inks are much denser, have higher conductivity, use less Ag, and are a fraction of the cost. Importantly, the inks anneal from 90 - 450 degrees C allowing for better passivation schemes than fired SiNx. This contribution highlights first experiments on the improved passivation of metallized poly-Si/SiO2 passivated contacts using metal-complex, Ag inks compared with particle-based, fired pastes.

metal-complex ink↗
DOE OSTI2022

Performance Leap of Lithium Metal Batteries in LiPF 6 Carbonate Electrolyte by a Phosphorus Pentoxide Acid Scavenger

Phosphorus pentoxide (P 2 O 5 ) is investigated as an acid scavenger to remove the acidic impurities in a commercial lithium hexafluorophosphate (LiPF 6 ) carbonate electrolyte to improve the electrochemical properties of Li metal batteries. Nuclear magnetic resonance (NMR) measurements reveal the detailed reaction mechanisms of P 2 O 5 with the LiPF 6 electrolyte and its impurities, which removes hydrogen fluoride (HF) and difluor-ophosphoric acid (HPO 2 F 2 ) and produces phosphorus oxyfluoride (POF 3 ), OF 2 P-O-PF 5 - anions, and ethyl difluorophosphate (C 2 H 5 OPOF 2 ) as new electrolyte species. The P 2 O 5 -modified LiPF 6 electrolyte is chemically compatible with a Li metal anode and LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) cathode, generating a PO x F y -rich solid electrolyte interphase (SEI) that leads to highly reversible Li electrodeposition, while eliminating transition metal dissolution and cathode particle cracking. The excellent electrochemical properties of the P 2 O 5 -modified LiPF6 electrolytes are demonstrated on Li||NMC622 pouch cells with 0.4 Ah capacity, 50 mu m Li anode, 3 mAh cm -2 NMC622 cathode, and 3 g Ah -1 electrolyte/capacity ratio. The pouch cells can be galvanostatically cycled at C/3 for 230 cycles with 87.7% retention.

25 ENERGY STORAGE↗
DOE OSTI2020

Stability of gas atomized reactive powders through multiple step in-situ passivation

A method for gas atomization of oxygen-reactive reactive metals and alloys wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a protective reaction film on the atomized particles. The present invention is especially useful for making highly pyrophoric reactive metal or alloy atomized powders, such as atomized magnesium and magnesium alloy powders. The gaseous reactive species (agents) are introduced into the atomization spray chamber at locations downstream of a gas atomizing nozzle as determined by the desired powder or particle temperature for the reactions and the desired thickness of the reaction film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Stability of gas atomized reactive powders through multiple step in-situ passivation

A method for gas atomization of oxygen-reactive reactive metals and alloys wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a protective reaction film on the atomized particles. The present invention is especially useful for making highly pyrophoric reactive metal or alloy atomized powders, such as atomized magnesium and magnesium alloy powders. The gaseous reactive species (agents) are introduced into the atomization spray chamber at locations downstream of a gas atomizing nozzle as determined by the desired powder or particle temperature for the reactions and the desired thickness of the reaction film.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Single-particle chemical analysis reveals organic-rich detonation soot products

The detonation of high explosives produces a wide variety of particulate matter (PM) with distinct properties, not all of which are traditionally studied for chemical composition, formation processes, and forensic applications. We report particle-resolved measurements of Composition B detonation soot using soot particle aerosol mass spectrometry (SP-AMS), identifying carbonaceous species and metals not previously characterized on a single-particle basis. Results are combined with scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) to enhance source-dependent signatures. Black carbon, including graphitic carbon and detonation nanodiamonds, contributed 50.5-71.4% of PM 2.5 mass, while 22.5-43.4% was non-refractory organic carbon, a previously overlooked component that exhibited a complex and varying composition. Detonations were performed with and without PMMA confinement and under steady and overdriven conditions. Distinct particles enriched with polycyclic aromatic hydrocarbons (PAHs) were observed in experiments utilizing confinement, with quantities dependent on manufacturing method. SEM-EDS validated SP-AMS findings of metals internally mixed with carbonaceous species and extended the particle size range to 100 µm. This work makes detecting non-refractory organics using single-particle techniques more feasible for detonation forensics and understanding high-energy soot formation. While this analysis uses offline sample collection, SP-AMS could be deployed for in-situ measurements of detonation PM 2.5 transported in the atmosphere.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Modelling the complex evaporated gas flow and its impact on particle spattering during laser powder bed fusion

The additive manufacturing (AM) of metals is becoming an increasingly important production process with the potential to replace traditional techniques such as casting. Laser Powder Bed Fusion (LPBF) is used in many applications to print metal parts from powder. The metal powder is heated locally with sufficient laser radiation that the liquid melt easily reaches its boiling temperature, which leads to a metallic vapour jet that can entrain both powder bed particles and molten droplets. The small size of laser-matter interaction site makes a detailed experimental analysis of the process challenging. Synchrotron X-ray imaging experiments are one of the few methods which can capture the dynamic melting and solidification processes. Comparing such experiments with computer simulations of the process is an important approach in order to better understand the manufacturing process and to analyse the influence of process parameters on the evaporated gas jet and the subsequent impact on particle ejection, leading to potentially reduced AM component quality. The melting and solidification of the metal powder is simulated using an Eulerian multiphase approach based on a control volume discretization of powder bed and substrate and a volume of liquid separation from melt and gas phase. The gas phase modelled as an ideal gas reaches velocities up to 100 m/s. Lagrangian particle tracking in the simulation demonstrates that the velocity fields calculated by the Eulerian multi-phase approach in combination with a standard drag-force model lead to particle accelerations in good agreement with those measured experimentally. In order to avoid numerical laborious Lagrangian calculations, a direct method to compare an Eulerian multiphase simulation with synchrotron X-ray experiments was introduced and validated. This approach is used to analyse the influence of process parameters including laser power and laser speed on the maximal acceleration of particles from the melt pool area. While the particle acceleration increases linearly with line energy in the conduction mode, a linear decrease of the acceleration with increasing line energy can be found in the transition mode before the accel-eration increases again with line energy in the keyhole mode.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ultra‐Thin Single‐Particle‐Layer Sodium Beta‐Alumina‐Based Composite Polymer Electrolyte Membrane for Sodium‐Metal Batteries

Inorganic/organic composite polymer electrolytes (CPEs) with good flexibility and electrode contact have been pursued for solid-state sodium-metal batteries. However, the application of CPEs for high energy density solid-state sodium-metal batteries is still limited by the low Na + conductivity, large thickness, and low ion transference number. Herein, an ultra-thin single-particle-layer (UTSPL) composite polymer electrolyte membrane with a thickness of ≈20 µm straddled by a sodium beta-alumina ceramic electrolyte (SBACE) is presented. A ceramic Na + -ion electrolyte that bridges or percolates across an ultra-thin and flexible polymer membrane provides: 1) the strength and flexibility from the polymer membrane, 2) excellent electrolyte/electrode interfacial contact, and 3) a percolation path for Na + -ion transfer. Owing to this novel design, the obtained UTSPL-35SBACE membrane exhibits a high Na+-ion conductivity of 0.19 mS cm -1 and a transference number of 0.91 at room temperature, contributing to long-term cycling stability of symmetric sodium cells with a small overpotential. The assembled quasi-solid-state cell with the as-prepared UTSPL-35SBACE membrane displays superior cycling performance with a discharge capacity of 105 mAh g -1 at 0.5 °C rate after 100 cycles and excellent rate performance (82 mAh g -1 at 5 °C rate) at room temperature with the potassium manganese hexacyanoferrate (KMHCF)@CNTs/CNFs cathode, where KMHCF refers to potassium manganese hexacyanoferrate.

25 ENERGY STORAGE↗
DOE OSTI2020

Regioselective Generation of Single‐Site Iridium Atoms and Their Evolution into Stabilized Subnanometric Iridium Clusters in MWW Zeolite

Abstract Preparation of supported metal catalysts with uniform particle size and coordination environment is a challenging and important topic in materials chemistry and catalysis. In this work, we report the regioselective generation of single‐site Ir atoms and their evolution into stabilized subnanometric Ir clusters in MWW zeolite, which are located at the 10MR window connecting the two neighboring 12MR supercages. The size of the subnanometric Ir clusters can be controlled by the post‐synthesis treatments and maintain below 1 nm even after being reduced at 650 °C, which cannot be readily achieved with samples prepared by conventional impregnation methods. The high structure sensitivity, size‐dependence, of catalytic performance in the alkane hydrogenolysis reaction of Ir clusters in the subnanometric regime is evidenced.

Liu, Lichen↗
DOE OSTI2020

Regioselective Generation of Single‐Site Iridium Atoms and Their Evolution into Stabilized Subnanometric Iridium Clusters in MWW Zeolite

Abstract Preparation of supported metal catalysts with uniform particle size and coordination environment is a challenging and important topic in materials chemistry and catalysis. In this work, we report the regioselective generation of single‐site Ir atoms and their evolution into stabilized subnanometric Ir clusters in MWW zeolite, which are located at the 10MR window connecting the two neighboring 12MR supercages. The size of the subnanometric Ir clusters can be controlled by the post‐synthesis treatments and maintain below 1 nm even after being reduced at 650 °C, which cannot be readily achieved with samples prepared by conventional impregnation methods. The high structure sensitivity, size‐dependence, of catalytic performance in the alkane hydrogenolysis reaction of Ir clusters in the subnanometric regime is evidenced.

Liu, Lichen↗
DOE OSTI2025

Microscale Metal Additive Manufacturing by Solid‐State Impact Bonding of Shaped Thin Films

The deposition of device-grade inorganic materials is one key challenge toward the implementation of additive manufacturing (AM) in microfabrication, and to that end, a broad range of physico-chemical principles has been explored for 3D fabrication with micro- and nanoscale resolution. Yet, for metals, a process that achieves material quality rivalling that of established thin-film deposition methods, and at the same time, has the potential to combine high throughput production with a broad palette of processable materials, is still lacking. Here, the kinetic, solid-state bonding of metal thin films for the additive assembly of high-purity, high-density metals with micrometer-scale precision is introduced. Indirect laser ablation accelerates micrometer-thick gold films to hundreds of meters per second without their heating or ablation. Their subsequent impact on the substrate above a critical velocity forms a permanent, metallic bond in the solid state. Stacked layers are of high density (>99%). By defining thin-film layers with established lithographic methods prior to launch, a variable feature size (2–50 µm), arbitrary shape of bonded layers, and parallel transfer of up to 36 independent film units in a single shot, is demonstrated. Thus, the solid-state kinetic bonding principle as a viable and potentially versatile route for micro-scale AM of metals is established.

3D printing↗
DOE OSTI2022

Synthesizing Carbon‐Supported, High‐Loading, Ultra‐Small Pt 3 Ni Nanoparticles via Tuning the Surface Electrostatic Effect

Carbon‐supported nanoparticles (NPs) are widely used as catalysts in fuel cells and electrolyzers. While it is well known that NPs with smaller size and higher loading often lead to better catalytic activity, they remain challenging to synthesize due to the weak control over the surface properties of the support. Herein, a facile approach to synthesize carbon‐supported, high‐loading, and ultra‐small Pt 3 Ni NPs via applying thermal shock on strongly interacted carbon support with metal salt is reported. Specifically, sodium citrate is introduced into the precursor solution and substrate mixture, which induces strong electrostatic effect between metal salts and carbon particles that markedly improves precursor anchoring and dispersion, thereby achieving high particle loading as well as small size and distribution. As a proof‐of‐concept, the synthesis of Pt 3 Ni NPs supported on carbon black with particle size of 1.56 ± 0.36 nm at 30 wt% loading and 1.66 ± 0.56 nm at 40 wt% loading is reported, where the sizes are among the smallest while the loadings are among the highest in the literature. This approach can be readily extended to many compositions and substrates, with tunable particle size and loading, thereby substantially expanding the synthesis space for NP catalysts in various electrochemical applications.

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

Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

Abstract In this paper, we present a brief historic overview of the research on dust in fusion devices with carbon plasma-facing components and then highlight the most recent developments in the post-carbon era of the field. In particular, we consider how the metallic dust form, mobilize, and interact with fusion plasmas and plasma facing components. Achievements in wall conditioning and associated anomalous plasma transport modification, including ELM suppression, with the powder injection technique is another focus of the paper. Capabilities of the state-of-art simulation tools to describe different aspects of dust in fusion devices are exemplified and new directions for future dust studies are brought forward.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Salt-Mediated Coarsening in Conversion-Reaction-Synthesized Nanoporous Metals and Nanocomposites Resolved through In Situ Synchrotron Diffraction Studies

High-energy synchrotron X-rays were used to probe the structural and microstructural evolution in Fe, Co, and Cu nanoporous metals (NPMs) and metal/salt nanocomposites (NCs) produced by recently developed conversion reaction synthesis (CRS) methods. Microstructure analysis of as-synthesized samples via whole pattern fitting showed that the NPMs exhibit domain sizes that increase as Co < Fe < Cu, with both Fe and Co having crystallite sizes below 3.0 nm. The as-synthesized metal/salt NCs had similar metal sizes, and additionally, the salt in the composite had unusually large lattice microstrain whose origin is attributed to chemical substitution of metal ions into the salt (e.g., Li $1–3x$ Fe $x$ Cl for Fe 3+ ). When thermal annealing is used to modify crystallite size, pore collapse often occurs in NPMs but NCs can be effectively tuned without this problem. While the NC coarsening occurs slowly at low temperatures, it was found that there is a drastic acceleration of the reaction rate at a specific onset temperature that results in the crystallite size increasing by an order of magnitude in about a minute. Curiously, there was no evidence in the diffraction data for salt melting at this onset temperature. However, there was a sharp reduction in the salt chemical lattice strain at the onset temperature, indicating that rapid metal coarsening is facilitated by the salt. Importantly, this behavior indicates an unexpectedly coupled reaction mechanism by which the metal ions needed for grain growth are supplied by the salt in a rate-limiting fashion.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Facile Strategy to Prepare Poly(ionic liquid)-Coated Solid Polymer Electrolytes through Layer-by-Layer Assembly

The inability of solid polymer electrolytes to preserve strong mechanical strength with high ionic conductivity hinders the commercialization of lithium metal batteries (LMBs). The success of fabricating layer-by-layer (LbL)-assembled electrolytes has realized the application of flexible solid polymer electrolytes in electrochemical devices. Here, we demonstrate a rational strategy to construct solid electrolytes coated with multiple ultrathin layers of polyanions (poly(sodium 4-styrenesulfonate)) and polycations (linear poly(1-butyl-3-(4-vinylbenzyl)-1H-imidazolium chloride) (BVIC)/linear poly(PEG 4 -VIC)/SiO 2 -g-poly(PEG 4 -VIC)) using an LbL assembly method. Poly(ionic liquid) backbones and PEG side groups are employed to facilitate the transport of lithium ions via the segmental motion of the macromolecular matrix. The fabricated free-standing membranes exhibited good ionic conductivities of 9.03–10 × 10 –4 S cm –1 . Furthermore, a Li/LiFePO 4 cell assembled with the LbL-membrane electrolytes exhibits an initial high discharge capacity of 143–158 mAhg –1 at 60 °C with high columbic efficiency. In conclusion, this approach, which combines polymer synthesis and LbL self-assembly, is an effective and facile route to fabricate solid polymer electrolyte membranes with superior ionic conductivity and mechanical robustness, which are useful for electrochemical devices and high-voltage battery applications.

25 ENERGY STORAGE↗
DOE OSTI2024

Hydrogen Spillover Is Regulating Minority Rh 1 Active Sites on TiO 2 in Room-Temperature Ethylene Hydrogenation

The complicated dynamics of active sites on single-atom catalysts under reducing conditions limits their applications in hydrogenation reactions and mechanistic understanding. Herein, we report that on Rh 1 /TiO 2 , *H spillover during room-temperature ethylene hydrogenation hydroxylates and reduces TiO 2 , enhancing the intrinsic activity of Rh 1 by 9-fold. Spectroscopic and kinetic evidence suggests that the spillover of *H is suppressed by their facile reaction with C 2 H 4 , most of the spilled *H are nonreactive spectators, and >99% turnovers occur on a small subset (<20%) of exposed “active Rh 1 ”. Steady-state kinetics indicates competitive adsorption between H and C 2 H 4 , H 2 dissociation is the rate-determining step, and the apparent activation barrier (E a,app ) of the reaction is ~48 kJ/mol. The evolution of Rh 1 under H 2 was further tracked by spectroscopic and microscopic techniques at elevated temperatures. At 200 °C, more Rh 1 are exposed, but these Rh 1 are at least 5-fold less active than that of the “active Rh 1 ”. At 300 °C, Rh clusters derived from Rh 1 become the main active sites, shifting E a,app to 62 kJ/mol, characteristic of Rh nanoparticles. At ≥400 °C, larger and more active Rh particles in the strong metal–support interaction state are created. In conclusion, this work revealed the unexpected regulation effects of *H spillover on M 1 active sites under ambient conditions, differentiated the minority active M 1 sites, and demonstrated how the stability of M 1 under reducing atmospheres affects hydrogenation catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗