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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

In-Tank Processing Using Low Temperature Aluminum Dissolution: Year 1 Progress Report

The Hanford Site stores approximately 56 million gallons of radioactive legacy defense waste in underground tanks. This study investigates the feasibility of utilizing in-tank low-temperature aluminum dissolution to favorably alter the transport properties of aluminum-rich southeast quadrant waste sludges, thereby de-risking sludge delivery for Direct Feed of High-Level Waste. Specifically, this study aims to assess the rate and extent of gibbsite dissolution under various conditions, including different particle sizes (~10 to 90 µm), NaOH concentrations (1 to 6 M), and the presence of specific analytes such as NO 2 - , NO 3 - , and other aluminum-rich waste background analytes, using simulated waste solids and liquids. Experimental tests were designed to highlight the impact of aluminum leaching on simulated waste transport properties, quantified by the just-suspended mixing speed (NJS), and were conducted under well-mixed, turbulent conditions, ensuring full suspension of gibbsite particles using an overhead mixer. The results suggest that the presence of NO 2 - and NO 3 - , in conjunction with leaching at relatively low free hydroxide contents, improved transport requirements (i.e., lowered NJS) for pure gibbsite slurries. These findings will inform the design of potential in-tank processing systems, optimizing aluminum dissolution for improved waste management in the Hanford Tank Farms.

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

Elimination of remnant phases in low-temperature growth of wurtzite ScAlN by molecular-beam epitaxy

We report growth of wurtzite Sc x Al 1-x N (x < 0.23) by plasma-assisted molecular-beam epitaxy on c-plane GaN at high temperatures significantly alters the extracted lattice constants of the material due to defects likely associated with remnant phases. In contrast, ScAlN grown below a composition-dependent threshold temperature exhibits uniform alloy distribution, reduced defect density, and atomic-step surface morphology. The c-plane lattice constant of this low-temperature ScAlN varies with composition as expected from previous theoretical calculations and can be used to reliably estimate alloy composition. Moreover, lattice-matched Sc 0.18 Al0 .82 N/GaN multi-quantum wells grown under these conditions display strong and narrow near-infrared intersubband absorption lines that confirm advantageous optical and electronic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Elimination of remnant phases in low-temperature growth of wurtzite ScAlN by molecular-beam epitaxy

Growth of wurtzite ScxAl1−xN (x < 0.23) by plasma-assisted molecular-beam epitaxy on cplane GaN at high temperatures significantly alters the extracted lattice constants of the material due to defects likely associated with remnant phases. In contrast, ScAlN grown below a composition-dependent threshold temperature exhibits uniform alloy distribution, reduced defect density, and atomic-step surface morphology. The c-plane lattice constant of this low-temperature ScAlN varies with composition as expected from previous theoretical calculations and can be used to reliably estimate alloy composition. Moreover, lattice-matched Sc0.18Al0.82N/GaN multiquantum wells grown under these conditions display strong and narrow near-infrared intersubband absorption lines that confirm advantageous optical and electronic properties.

Dzuba, Brandon↗
DOE OSTI2020

Elucidation of the Active Sites in Single-Atom Pd 1 /CeO 2 Catalysts for Low-Temperature CO Oxidation

Supported precious metals with atomic dispersion are of great interest in catalysis due to their potentials in achieving maximum atom efficiency and unique reactivities. Herein, the active sites for low-temperature CO oxidation are elucidated over single-atom Pd 1 /CeO 2 catalysts prepared via high-temperature atom trapping (AT). The increased oxygen vacancies on CeO 2 surface induced by 800 °C air calcination result in decreased Pd–CeO 2 coordinations, i.e., the coordination-unsaturated Pd 2+ on CeO 2 . Light-off and light-out measurements coupled with CO-DRIFTS and X-ray absorption characterization confirm that these coordination-unsaturated Pd 2+ on CeO 2 are much more reactive than the fully coordinated counterpart, evidenced by a decrease of T 90 (temperature to achieve 90% conversion) by ~100 °C in CO oxidation at a gas hourly space velocity of 300 L g –1 h –1 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Structural and reactive evolution of oxidatively grafted Pd catalysts on MnO 2 for the low-temperature oxidation of CO

We report Isolated Pd atoms supported on high surface area MnO 2 , prepared by the oxidative grafting of (bis(tricyclohexylphosphine-palladium(0)), catalyze (>50 turnovers, 17 h) the low temperature (≤325 K) oxidation of CO (7.7 kPa O 2 , 2.6 kPa CO) with results of in situ/operando and ex situ spectroscopic characterization signifying a synergistic role of Pd and MnO 2 in facilitating redox turnovers.

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

Enhancing the low-temperature performance of Pt-based three-way catalysts using CeO 2 (core)@ZrO 2 (shell) supports

Developing robust Pt/CeO 2 -based three-way catalysts (TWCs) with enhanced oxygen buffering capability and low-temperature activity is highly desirable. In this study, a new TWC family, Pt/(1 − x)CeO 2 (core)@xZrO 2 (shell) (where x = 0–0.5), was prepared and evaluated at degreened (DG) and hydrothermally aged (HTA) states. Incorporation of 0.1 molar concentration of ZrO 2 resulted in a decreased temperature that 50% (T 50 ) (CO: 167 °C, THCs: 218 °C, NO: 228 °C) and 90% (T 90 ) (CO: 207 °C, THCs: 237 °C, NO: 244 °C) conversions achieved over HTA 1.8 wt% Pt/0.9CeO 2 @0.1ZrO 2 compared to the HTA 1.8 wt% Pt/CeO 2 sphere (CO: T50,90 = 179, 222 °C, THCs: 234, 252 °C, NO x : 240, 260 °C). An enhanced oxygen storage capacity and oxygen release rate were observed over Pt/0.9CeO 2 @0.1ZrO 2 compared to the Pt/CeO 2 sphere. Increasing the ZrO 2 molar concentration to values greater than 0.2 resulted in increased T 50 s (224, 265 274 °C) and T 90 s (251, 289, 292 °C) for CO, THCs, and NO x , respectively, over 1.8 wt.% Pt/0.5CeO 2 @0.5ZrO 2 . Overall, this work highlights the potential of forming a ZrO 2 shell on CeO 2 spheres as a support for TWC applications.

Liu, Chih-Han [State Univ. of New York (SUNY), Buf↗
DOE OSTI2021

Highly Perfluorinated Covalent Triazine Frameworks Derived from a Low-Temperature Ionothermal Approach Towards Enhanced CO 2 Electroreduction

Perfluorinated covalent triazine frameworks (F-CTFs) have shown unique features and attractive performance in separation and catalysis. However, state-of-art F-CTFs synthesized via the ZnCl 2 -promoted procedure have quite low fluorine contents due to C-F bond cleavage induced by chloride (a Lewis base) and the harsh conditions deployed (400-700 °C). Fabricating F-CTFs with high fluorine contents (> 30 wt%) remains challenging. Herein, we present a low-temperature ionothermal approach (275 °C) to prepare F-CTFs, which is achieved via polymerization of tetrafluoroterephthalonitrile (TFPN) over the Lewis superacids, e.g., zinc triflimide [Zn(NTf 2 ) 2 ] without side reactions. With low catalyst loading (equimolar), F-CTFs are afforded with high fluorine content (31 wt%), surface area up to 367 m 2 g -1 , and micropores around 1.1 nm. The highly hydrophobic F-CTF-1 exhibits good capability to boost electroreduction of CO 2 to CO, with faradaic efficiency of 95.7% at –0.8 V and high current density (–141 mA cm -2 ) surpassing most of the metal-free electrocatalysts.

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

Low-Temperature Molten Salt Electrochemical CO 2 Upcycling for Advanced Energy Materials

One strategy for addressing the climate crisis caused by CO 2 emissions is to efficiently convert CO 2 to advanced materials suited for green and clean energy technology applications. Porous carbon is widely used as an advanced energy storage material because of its enhanced energy storage capabilities as an anode. Herein, we report electrochemical CO 2 upcycling to solid carbon with a controlled microstructure and porosity in a ternary molten carbonate melt at 450 °C. Controlling the electrochemical parameters (voltage, temperature, cathode material) enabled the conversion of CO 2 to porous carbon with a tunable morphology and porosity for the first time at such a low temperature. Additionally, a well-controlled morphology and porosity are beneficial for reversible energy storage. In fact, these carbon materials delivered high specific capacity, stable cycling performances, and exceptional rate capability even under extremely fast charging conditions when integrated as an anode in lithium-ion batteries (LIBs). In conclusion, the present approach not only demonstrated efficient upcycling of CO 2 into porous carbon suitable for enhanced energy storage but can also contribute to a clean and green energy technology that can reduce carbon emissions to achieve sustainable energy goals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Enhancing the electron mobility in Si-doped (010) β-Ga 2 O 3 films with low-temperature buffer layers

We demonstrate a new substrate cleaning and buffer growth scheme in β-Ga 2 O 3 epitaxial thin films using metal–organic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 °C) un-doped Ga 2 O 3 buffer was grown, followed by a transition layer to a high-temperature (HT, 810 °C) Si-doped Ga 2 O 3 channel layers without growth interruption. The (010) Ga 2 O 3 Fe-doped substrate cleaning uses solvent cleaning, followed by additional hydrofluoric acid (49% in water) treatment for 30 min before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer–substrate interface that originates from the substrate polishing process or contamination from the ambient. From secondary ion mass spectroscopy (SIMS) analysis, the Si peak atomic density at the substrate interface is found to be several times lower than the Fe atomic density in the substrate—indicating full compensation. The elimination of the parasitic electron channel at the epi–substrate interface was also verified by electrical (capacitance–voltage profiling) measurements. In the LT-grown (600 °C) buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp, with a decay rate of ∼9 nm/dec. X-ray off-axis rocking curve ω-scans show very narrow full width at half maximum (FWHM) values, similar to the as-received substrates. These channels show record high electron mobility in the range of 196–85 cm 2 /V⋅s in unintentionally doped and Si-doped films in the doping range of 2 × 10 16 –1 × 10 20 cm −3 . Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT buffers. Record high electron Hall mobility of 110 cm 2 /V⋅s was measured for sheet charge density of 9.2 × 10 12 cm −2 . This substrate cleaning, combined with the LT buffer scheme, shows the potential of designing Si-doped β-Ga 2 O 3 channels with exceptional transport properties for high-performance Ga 2 O 3 -based electron devices.

Bhattacharyya, Arkka↗
DOE OSTI2024

Final Technical Report - Rapid Surface Microanalysis using a Low Temperature Plasma

This project focused on improving our current understanding and scientific knowledge in the area of plasma-surface interactions and plasma assisted material synthesis related to advanced microelectronics and nanotechnology. Current challenges include: controlling the interaction of Low Temperature Plasma (LTP) with a single layer of atoms to manufacture integrated circuits, continued miniaturization of integrated circuits, LTP processing of material surfaces and thin films to enable industrial scale fabrication of advanced microelectronics, synthesis of new materials, nanomaterials, nanotubes, and complex materials, Technology developed in this subtopic is of value to either (i) enable scans of surfaces (~1 sq. cm area) using various microscopies (electron, optical, other) at high resolution (micron or sub-micron resolution) rapidly (hours or days rather than years to complete a high-resolution scan of such a large surface area), or (ii) enable scans of surfaces (~1 sq. cm area) using various microscopies (electron, optical, other) at relatively low resolution rapidly, then apply algorithms to select spots for micron-scale imaging. Sputtering occurs when particles of a solid material are ejected from its surface by energetic particles from a plasma. While the degradation of the solid material and the subsequent deposition of the ejected material onto vulnerable surfaces are the usual subjects of sputtering studies, plasma science has yet to be combined with sputtering to create new diagnostics devices and systems. Small changes in the design of the plasma discharge device make it possible to create broad plasma beams for rapid scanning or small plasma beams to obtain the distribution of ejected elements with micron resolution. In the high-resolution use, the ion flux is extracted from the gas-discharge plasma and focused by a spherical emission surface to micron sizes onto the target specimen, providing very local sputtering and local elemental analysis. We call this “self-focusing”. The radiation from the excited and ionized sputtered atoms is recorded by a spectrometer through a window and fiberglass cable and analyzed with standard software packages used for optical glow discharge spectroscopy. Computer simulations of beam formation were used to verify and optimize the designs to be tested. A prototype was designed, constructed, and used to start experiments of beam formation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Formation of Crystalline Silica–Carbonate Biomorphs of Alkaline Earth Metals (Ca, Ba, Sr) from Ambient to Low Temperatures: Chemical Implications during the Primitive Earth’s Life

The Earth has undergone at least four great glaciations, during which the ice layers and the glaciers have expanded all over the planet, corresponding to significant drops in global temperatures that lasted millions of years. Since the Precambrian era, ice ages have occurred at intervals of several millions of years. It is considered that the impact on the biosphere was large, because life was on the brink of disappearing completely from the planet. During these glaciation periods, carbon was reassigned, with the subsequent formation of carbonates called cap carbonates, which present stromatolite-like activity. These findings prove that life was conserved even during the glacial period. Knowledge on life conservation during the glacial period through stromatolites that have endured until the present day, is of special relevance. In recent investigations, in vitro structures have been synthesized; these crystalline aggregates have been named biomorphs because they mirror the morphologies of primitive organisms called Precambrian cherts. These biomorphs have been synthesized at different temperatures (from room temperature to lower ones). Finally, the aim of the present work was to synthesize CaCO 3 , BaCO 3 , and SrCO 3 silica–carbonate biomorphs at three low temperatures (4 °C, -20 °C, and -70 °C). CaCO 3 biomorphs present almost the same morphology at all temperatures with a calcite crystalline structure, whereas BaCO 3 and SrCO 3 biomorphs present remarkably different morphologies depending on temperature with witherite and strontianite crystalline structure, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Palladium/Zeolite Low Temperature Passive NOx Adsorbers (PNA): Structure-Adsorption Property Relationships for Hydrothermally Aged PNA Materials

Zeolites with different framework structures (SSZ-13, ZSM-5, BEA) but similar Si/Al ratios and Pd loading (~1 wr%) were synthesized and evaluated as low temperature passive NOx adsorbers (PNA). These materials exhibit high NOx adsorption efficiency with atomically dispersed Pd the active adsorption site. Hydrothermal aging at 750 ºC for 16 hours in the presence of 10% water vapor in air resulted in the formation of PdO nanoparticles in all three samples as evidenced by high energy XRD. Hydrothermal aging of the small-pore Pd/SSZ-13 (Si/Al = 6), which contain ~100-90% atomically dispersed palladium ions, decreases its PNA performance only by ~10-20%. High-field solid state 27Al NMR studies on the fresh and aged samples substantiate dealumination and significant changes in the distribution of Al (and thus, Bronsted acid) sites after hydrothermal aging. FTIR measurements with NO probe molecule and titration of Bronsted acid sites with nitrosyl (NO+) ions further corroborate the 27Al NMR data. Because framework aluminum atoms are the anchoring sites for atomically dispersed Pd ions, their elution from the framework causes the loss of active atomically dispersed Pd species. Furthermore, with the aid of HAADF-STEM imaging and synchrotron XRD studies, we further confirm and visualize the fate of these Pd species – they agglomerate into PdO nanoparticles on the external surface of zeolite. Consequently, these changes lead to the decrease in PNA performance of these materials after hydrothermal aging. The thus formed agglomerates cannot be re-dispersed back to their ionic state due to the loss of framework Al T-sites and/or inherent stability of such large PdO particles. Our study clearly demonstrates that, unlike in previous studies that found increased PNA performance upon HTA , high temperatures hydrothermal aging of PNA materials that contain atomically dispersed Pd initially, results in a decrease in NOx storage efficiency due mostly to the formation of PdO agglomerates. However, we also highlight the high hydrothermal stability of predominantly atomically dispersed 1-3 wt% Pd/SSZ-13 (Si/Al = 6), whose performance decreases only marginally after prolonged hydrothermal aging at 750 ºC. Overall, this study shows that hydrothermally stable passive NOx materials can be prepared using small-pore SSZ-13 zeolite.

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

Low-Temperature Catalyst Redispersion: A Route to Enhanced Stability of Supported Metal Catalysts?

Sintering poses a significant challenge to achieving the long-term stability of supported metal catalysts under reaction conditions. Here, in this study, we report a low-temperature catalyst redispersion mechanism, in which platinum single atoms, which aggregate into nanoparticles under Reverse Water Gas Shift (RWGS) conditions at elevated temperatures, fragment into atomically dispersed species upon cooling. Using multimodal operando characterization combined with first-principles theoretical modeling, we track the structural evolution of Pt single atoms supported on ceria nanodomes, deposited either on ceria or ceria–titania mixed oxides. We find that fragmentation is more pronounced when cooling occurs under RWGS conditions compared to CO alone, owing to a synergistic interplay of the effects of H 2 , CO 2 , and CO. The support architecture has a strong influence on the extent of redispersion: while CO alone induces fragmentation on ceria, interfacial confinement and vacancy pinning at the ceria–titania interface suppress restructuring. In contrast, RWGS conditions overcome these barriers, enabling redispersion across both supports. These findings point toward a pathway for catalyst stabilization via reaction-induced redispersion under mild conditions.

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

Material Discovery and High Throughput Exploration of Ru Based Catalysts for Low Temperature Ammonia Decomposition

High throughput experimentation has the capability to generate massive, multidimensional datasets, allowing for the discovery of novel catalytic materials. Here, we show the synthesis and catalytic screening of over 100 unique Ru-Metal-K based bimetallic catalysts for low temperature ammonia decomposition, with a Ru loading between 1–3 wt% Ru and a fixed K loading of 12 wt% K, supported on γ-Al2O3. Bimetallic catalysts containing Sc, Sr, Hf, Y, Mg, Zr, Ta, or Ca in addition to Ru were found to have excellent ammonia decomposition activity when compared to state-of-the-art catalysts in literature. Furthermore, the Ru content could be reduced to 1 wt% Ru, a factor of four decrease, with the addition of Sr, Y, Zr, or Hf, where these secondary metals have not been previously explored for ammonia decomposition. The bimetallic interactions between Ru and the secondary metal, specifically RuSrK and RuFeK, were investigated in detail to elucidate the reaction kinetics and surface properties of both high and low performing catalysts. The RuSrK catalyst had a turnover frequency of 1.78 s−1, while RuFeK had a turnover frequency of only 0.28 s−1 under identical operating conditions. Based on their apparent activation energies and number of surface sites, the RuSrK had a factor of two lower activation energy than the RuFeK, while also possessing an equivalent number of surface sites, which suggests that the Sr promotes ammonia decomposition in the presence of Ru by modifying the active sites of Ru.

McCullough, Katherine (ORCID:0000000197525740)↗
DOE OSTI2023

A highly proton conductive perfluorinated covalent triazine framework via low-temperature synthesis

Proton-conducting materials are essential to the emerging hydrogen economy. Covalent triazine frameworks (CTFs) are promising proton-conducting materials at high temperatures but need more effective sites to strengthen interaction for proton carriers. However, their construction and design in a concise condition are still challenges. Herein, we show a low temperature approach to synthesize CTFs via a direct cyclotrimerization of aromatic aldehyde using ammonium iodide as facile nitrogen source. Among the CTFs, the perfluorinated CTF (CTF-TF) was successfully synthesized with much lower temperature ( ≤ 160 °C) and open-air atmosphere. Due to the additional hydrogen-bonding interaction between fluorine atoms and proton carriers (H 3 PO 4 ), the CTF-TF achieves a proton conductivity of 1.82 × 10 -1 S cm -1 at 150 °C after H 3 PO 4 loading. Moreover, the CTF-TF can be readily integrated into mixed matrix membranes, displaying high proton conduction abilities and good mechanical strength. This work provides an alternative strategy for rational design of proton conducting media.

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

Low-temperature Leidenfrost-like jumping of sessile droplets on microstructured surfaces

The Leidenfrost effect—the levitation and hovering of liquid droplets on hot solid surfaces—generally requires a sufficiently high substrate temperature to activate liquid vaporization. Here, in this paper, we report the modulation of Leidenfrost-like jumping of sessile water microdroplets on micropillared surfaces at a relatively low temperature. Compared to traditional Leidenfrost effect occurring above 230 °C, the fin-array-like micropillars enable water microdroplets to levitate and jump off the surface within milliseconds at a temperature of 130 °C by triggering the inertia-controlled growth of individual vapour bubbles at the droplet base. We demonstrate that droplet jumping, resulting from momentum interactions between the expanding vapour bubble and the droplet, can be modulated by tailoring of the thermal boundary layer thickness through pillar height. This enables regulation of the bubble expansion between the inertia-controlled mode and the heat-transfer-limited mode. The two bubble-growth modes give rise to distinct droplet jumping behaviours characterized by constant velocity and constant energy regimes, respectively. This heating strategy allows the straightforward purging of wetting liquid droplets on rough or structured surfaces in a controlled manner, with potential applications including the rapid removal of fouling media, even when located in surface cavities.

42 ENGINEERING↗
DOE OSTI2024

Kinetic effects of self-organization in low-temperature magnetized plasmas

This final report presents the progress made for the DOE-SC0020623 for the period of performance between January 1 2020 and September 30 2024. The research project is entitled "Kinetic effects of self-organization in low-temperature magnetized plasmas", in which kinetic theory and simulations are used to under stand self-organization patterns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗