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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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Xerogel-Derived Ni Electrocatalysts for the Hydrogen Evolution Reaction in Alkaline Media

Anion exchange membrane water electrolyzers (AEMWEs) represent a promising technology for hydrogen production. The big advantage of the technology is that it allows for the use of platinum group metal-free (PGM-free) electrocatalysts at both electrodes, including catalysts for the hydrogen evolution reaction (HER) at the cathode. In addition to fulfilling the cost requirement, PGM-free HER catalysts need to meet the activity and durability targets of the AEMWEs. Here, in this work, we developed several carbon-supported, xerogel-derived nickel (Ni) HER electrocatalysts and evaluated the effect of various synthesis conditions, such as the type of carbon support, Ni-to-carbon ratio, and heat-treatment temperature and time, on their performance. Scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy (STEM-EDS), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS) revealed the formation of Ni nanoparticles with an oxygen-rich layer on the outside. Durability of the best-performing catalyst was assessed via a constant-current hold at 10 mA cm –2 over 100 h. This catalyst was found to be more active and durable than the reference PGM-free material, a commercial Ni catalyst supported on a Vulcan XC-72. The catalyst was also tested in the cathode of a fully PGM-free AEMWE, allowing to reach 1.90 V (1.84 V HFR-free) at 1 A cm –2 at 80 °C.

08 HYDROGEN↗
DOE OSTI2020

Eutectic Synthesis of the P2-Type Na x Fe 1/2 Mn 1/2 O 2 Cathode with Improved Cell Design for Sodium-Ion Batteries

An engaging area of research in sodium-ion batteries (SIBs) has been focusing on discovery, design, and synthesis of high-capacity cathode materials in order to boost energy density to levels close enough to that of state-of-the-art lithium-ion batteries. Of particular interest, P2-type layered oxide, Na 2/3 Fe 1/2 Mn 1/2 O 2 , has been researched as a potential cathode in SIBs based on its high theoretical capacity of 260 mA h/g and use of noncritical materials. However, the reported synthesis methods are not only complex and energy-demanding but also often yield inhomogeneous and impure materials with capacities less than 200 mA h/g under impractical test conditions. Here, we report a novel synthesis route using low-temperature eutectic reaction to produce highly homogeneous, crystalline, and impurity-free P2-Na x Fe 1/2 Mn 1/2 O 2 with enhanced Na-ion diffusivity and kinetics. The overall electrochemical performances of the Na-ion cells have been improved by pairing the P2-cathode with presodiated hard carbon anodes, leading to reversible capacities in the range of 180 mA h/g. This new approach is a contribution toward the simplification of synthesis and scalability of sodium-based cathodes with high crystallinity and fine-tuned morphology and the realization of a sodium-ion battery system with lower cost and improved electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2021

Intelligent Agents for the Optimization of Atomic Layer Deposition

Atomic layer deposition (ALD) is a highly controllable thin film synthesis approach with applications in computing, energy, and separations. The flexibility of ALD means that it can access a massive chemical catalogue; however, this chemical and process diversity results in significant challenges in determining processing parameters that result in stable and uniform film growth with minimal precursor consumption. In situ measurements of the ALD growth per cycle (GPC) can accelerate process development but it still requires expert intuition and time-consuming trial and error to identify acceptable processing parameters. This procedure is made more difficult by the presence of experimental noise in the GPC values and the complexity of ALD surface chemistries. Here, a need exists for efficient optimization approaches capable of autonomously determining processing conditions resulting in optimal ALD film growth. In this work, we present the development of three optimization strategies and compare their performance in optimizing four simulated ALD processes. Furthermore, the effect of noise in the GPC measurements on optimization convergence is studied.

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

Nitroarene Photoactivation Promotes Oxidative Deconstruction of Olefinic Polymers

Photoactivation of nitroarenes has been recently reported to induce the transformation of alkenyl bonds into carbonyl functionalities. Capitalizing on this unique photochemical mechanism, this study explores the use of nitroarenes to achieve oxidative cleavage of olefinic polymers under visible light irradiation. The degradation of various olefinic polymers, including commercially available polybutadiene, polynorbornene, both linear and cyclic poly(phenylacetylene), as well as backbone-modified polyacrylates with alkenyl functionality was investigated. To elucidate the efficacy of this methodology, a series of nitroarene derivatives bearing variable substituents were screened for their degradative efficiency on polybutadiene. Varying nitroarene stoichiometry, reaction temperature, and pos-treaction workup conditions were investigated to optimize degradation conditions. Furthermore, the results demonstrated that photoexcited nitroarenes enable efficient oxidative degradation of olefinic polymers in a safe and sustainable manner, providing a novel strategy for mild macromolecular deconstruction.

Bond cleavage↗
DOE OSTI2026

Insights into the Structure of Ultrasmall Fluorescent Core–Shell Silica Nanoparticles

Ultrasmall fluorescent core–shell nanoparticles (NPs) with a silica core and poly(ethylene glycol) ligand shell are the earliest example of hybrid NPs that have received U.S. investigational new drug FDA approval. They are among only a few inorganic NPs translated to safety, diagnostic, and therapeutic human clinical trials. Despite these achievements, little is known about the exact structure of their 3–4 nm sized silica cores. We report the surprising discovery of a well-defined pentagonal bipyramidal core structure preferentially formed in the aqueous synthesis built from seven primary silica NPs. A combination of reverse-phase high-performance liquid chromatography, cryogenic transmission electron microscopy, and coarse-grained simulations provides fundamental insights into this magic-size cluster formation and its unusual stability. Here, results rationalize the successful NP synthesis scale-up from 1 mL to 50 L, provide clues to the recent discovery of their self-therapeutic properties in oncology via ferroptosis, an iron-dependent cell death mechanism, and promise improved control of particle size distribution via chromatographic separations.

cluster chemistry↗
DOE OSTI2025

DNA-PAINT Imaging with Hydrogel Imprinting and Clearing

Hydrogel-embedding is a versatile technique in fluorescence microscopy, offering stabilization, optical clearing, and the physical expansion of biological specimens. DNA-PAINT is a super-resolution microscopy approach based on the diffusion and transient binding of fluorescently labeled oligos, but its feasibility in hydrogels has not yet been explored. In this study, we demonstrate that polyacrylamide hydrogels support sufficient diffusion for effective DNA-PAINT imaging. Using acrydite-anchored oligonucleotides imprinted from patterned DNA origami nanostructures and microtubule filaments in fixed cells, we find that hydrogel embedding preserves docking strand positioning at the nanoscale. Sample clearing via protease treatment had minor structural effects on the microtubule structure and enhanced diffusion and accessibility to hydrogel-imprinted docking strands. Our work demonstrates promising potential for diffusion and binding-based fluorescence imaging applications in hydrogel-embedded samples.

DNA origami↗
DOE OSTI2021

Direct Optical Lithography of Colloidal Metal Oxide Nanomaterials for Diffractive Optical Elements with 2π Phase Control

Spatially patterned dielectric materials are ubiquitous in electronic, photonic, and optoelectronic devices. These patterns are typically made by subtractive or additive approaches utilizing vapor-phase reagents. On the other hand, recent advances in solution-phase synthesis of oxide nanomaterials have unlocked a materials library with greater compositional, microstructural, and interfacial tunability. However, methods to pattern and integrate these nanomaterials in real-world devices are less established. In this work, we directly optically pattern oxide nanoparticles (NPs) by mixing them with photosensitive diazo-2-naphthol-4-sulfonic acid and irradiating with widely available 405 nm light. We demonstrate the direct optical lithography of ZrO 2 , TiO 2 , HfO 2 , and ITO NPs and investigate the chemical and physical changes responsible for this photoinduced decrease in solubility. Micron-thick layers of amorphous ZrO 2 NPs were patterned with micron resolution and shown to allow 2 pi phase control of visible light. We also show multilayer patterning and use it to fabricate features with different thicknesses and distinct structural colors. Upon annealing at 400 degrees C, the deposited ZrO 2 structures have excellent optical transparency across a wide wavelength range (0.3-10 mu m), a high refractive index (n = 1.84 at 633 nm), and are optically smooth. We then fabricate diffractive optical elements, such as binary phase diffraction gratings, that show efficient diffractive behavior and good thermal stability. Different oxide NPs can also be mixed prior to patterning, providing a high level of material tunability. This work demonstrates a general patterning approach that harnesses the processability and diversity of colloidal oxide nanomaterials for use in photonic applications.

2𝜋 phase shift↗
DOE OSTI2025

Non-stoichiometry Governs the Pathway from Amorphous to Crystalline Calcium Carbonate

The controlled crystallization of calcium carbonate underlies the elaborate architectures of marine corals, the design of biomimetic materials, and the global carbon cycle. Despite its ubiquity, the chemical mechanisms that govern the crystallization of calcium carbonate from its amorphous precursor, amorphous calcium carbonate (ACC), remain elusive, largely due to the difficulty in resolving the structure and chemistry of this transient amorphous state. Here, we use time-lapse photography, image analysis, spatially resolved pH determination, in situ synchrotron pair distribution function (PDF) analysis, and dynamic nuclear polarization (DNP) solid-state nuclear magnetic resonance (NMR) spectroscopy to reveal pervasive compositional variability in ACC that underpins its metastability and crystallization. By evaluating the kinetics of the amorphous-to-crystalline transition across different solution chemistries, we demonstrate that ACC is non-stoichiometric and CO 3 -deficient. Counterions from the precursor (e.g., NO 3 - from Ca(NO 3 ) 2 ) substitute into the ACC network, displacing CO 3 ions and mediating both ACC stability and transformation. Crystallization proceeds through refinement of the stoichiometry toward CaCO 3 and uptake of free CO 3 2- anions. Furthermore, these findings are consistent across a wide range of concentrations and different carbonate sources, explaining the diverse behaviors observed for ACC and providing a chemical framework for controlling calcium carbonate crystallization.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Patterned crystal growth and heat wave generation in hydrogels

Abstract The crystallization of metastable liquid phase change materials releases stored energy as latent heat upon nucleation and may therefore provide a triggerable means of activating downstream processes that respond to changes in temperature. In this work, we describe a strategy for controlling the fast, exothermic crystallization of sodium acetate from a metastable aqueous solution into trihydrate crystals within a polyacrylamide hydrogel whose polymerization state has been patterned using photomasks. A comprehensive experimental study of crystal shapes, crystal growth front velocities and evolving thermal profiles showed that rapid growth of long needle-like crystals through unpolymerized solutions produced peak temperatures of up to 45˚C, while slower-crystallizing polymerized solutions produced polycrystalline composites and peaked at 30˚C due to lower rates of heat release relative to dissipation in these regions. This temperature difference in the propagating heat waves, which we describe using a proposed analytical model, enables the use of this strategy to selectively activate thermoresponsive processes in predefined areas.

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

Elasticity-controlled jamming criticality in soft composite solids

Soft composite solids are made of inclusions dispersed within soft matrices. They are ubiquitous in nature and form the basis of many biological tissues. In the field of materials science, synthetic soft composites are promising candidates for building various engineering devices due to their highly programmable features. However, when the volume fraction of the inclusions increases, predicting the mechanical properties of these materials poses a significant challenge for the classical theories of composite mechanics. The difficulty arises from the inherently disordered, multi-scale interactions between the inclusions and the matrix. To address this challenge, we systematically investigated the mechanics of densely filled soft elastomers containing stiff microspheres. We experimentally demonstrate how the strain-stiffening response of the soft composites is governed by the critical scalings in the vicinity of a shear-jamming transition of the included particles. The proposed criticality framework quantitatively connects the overall mechanics of a soft composite with the elasticity of the matrix and the particles, and captures the diverse mechanical responses observed across a wide range of material parameters. The findings uncover a novel design paradigm of composite mechanics that relies on engineering the jamming properties of the embedded inclusions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Highly transparent silanized cellulose aerogels for boosting energy efficiency of glazing in buildings

Abstract To maintain comfortable indoor conditions, buildings consume ~40% of the energy generated globally. In terms of passively isolating building interiors from cold or hot outdoors, windows and skylights are the least-efficient parts of the building envelope because achieving simultaneously high transparency and thermal insulation of glazing remains a challenge. Here we describe highly transparent aerogels fabricated from cellulose, an Earth-abundant biopolymer, by utilizing approaches such as colloidal self assembly and procedures compatible with roll-to-roll processing. The aerogels have visible-range light transmission of 97–99% (better than glass), haze of ~1% and thermal conductivity lower than that of still air. These lightweight materials can be used as panes inside multi-pane insulating glass units and to retrofit existing windows. We demonstrate how aerogels boost energy efficiency and may enable advanced technical solutions for insulating glass units, skylights, daylighting and facade glazing, potentially increasing the role of glazing in building envelopes.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Photobiological production of high-value pigments via compartmentalized co-cultures using Ca-alginate hydrogels

Abstract Engineered cyanobacterium Synechococcus elongatus can use light and CO 2 to produce sucrose, making it a promising candidate for use in co-cultures with heterotrophic workhorses. However, this process is challenged by the mutual stresses generated from the multispecies microbial culture. Here we demonstrate an ecosystem where S. elongatus is freely grown in a photo-bioreactor (PBR) containing an engineered heterotrophic workhorse (either β-carotene-producing Yarrowia lipolytica or indigoidine-producing Pseudomonas putida ) encapsulated in calcium-alginate hydrogel beads. The encapsulation prevents growth interference, allowing the cyanobacterial culture to produce high sucrose concentrations enabling the production of indigoidine and β-carotene in the heterotroph. Our experimental PBRs yielded an indigoidine titer of 7.5 g/L hydrogel and a β-carotene titer of 1.3 g/L hydrogel, amounts 15–22-fold higher than in a comparable co-culture without encapsulation. Moreover, 13 C-metabolite analysis and protein overexpression tests indicated that the hydrogel beads provided a favorable microenvironment where the cell metabolism inside the hydrogel was comparable to that in a free culture. Finally, the heterotroph-containing hydrogels were easily harvested and dissolved by EDTA for product recovery, while the cyanobacterial culture itself could be reused for the next batch of immobilized heterotrophs. This co-cultivation and hydrogel encapsulation system is a successful demonstration of bioprocess optimization under photobioreactor conditions.

59 BASIC BIOLOGICAL SCIENCES↗