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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

An in-situ crosslinking binder for binder jet additive manufacturing

Additive Manufacturing (AM) of metals is a potentially disruptive technology that could significantly change the industrial supply chain. There are a limited number of AM methods capable of creating metal parts, and one method showing significant potential is Binder Jet AM (Binder Jetting). Binder Jetting utilizes an inkjet print head to deposit a binder fluid onto a powder bed and bind together powder particles into a desired geometry. This study investigates a new binder system consisting of a difunctional monomer, triethylene glycol dimethacrylate (TEG-DMA). TEG-DMA exhibits excellent printability with an Ohnesorge’s number of .258 making the Z number 3.876. During the thermal curing process, the difunctional monomer polymerizes and crosslinks at the onset temperature of 138 °C, becoming a solid dimethacrylate network. When the binder is utilized within the stainless-steel powder bed at 200 °C, it forms a network incorporating the stainless-steel particles, binding the powder into any specified geometry. Crosslinking the monomer within the stainless-steel 420 powder bed imparts a flexural strength of 1.0–3.3 MPa to the green part depending on the volume of monomer in the part. After sintering, the final stainless-steel parts results in a void fraction close to 60 % and carbon content below 0.4 %.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-speed X-ray imaging of droplet-powder interaction in binder jet additive manufacturing

Binder jetting (BJ) is an additive manufacturing process that uses a powder feedstock in a layer wise process to print parts by selectively depositing a liquid binder into the powder bed using inkjet technology. This study presents findings from high-speed synchrotron imaging of binder droplet-interaction during the BJ printing process. A custom laboratory-scale BJ test platform was used for testing which enabled control of relevant process parameters including powder material, print geometry, spacing between droplets, powder bed density, and powder moisture content. Powder ejection was observed above the powder bed surface and powder relocation due to droplet impact was observed below the powder bed surface. Powder relocation was observed to be sensitive to powder material, powder bed density, powder bed moisture, droplet spacing, and print geometry. Increasing powder bed density was found to increase particle ejection velocity but reduce the total number of particles ejected. Process parameters that increase binder / moisture content in the powder bed were found to reduce powder ejection. The number of ejected powder particles was reduced for lower droplet spacings. Both powder ejection and powder relocation below the powder bed were reduced by treating the surface of the powder bed with a water/triethylene glycol (TEG) mixture before printing. In conclusion, results from this study help to build understanding of the physical mechanisms in the BJ printing process that may contribute to formation of defects observed in final parts.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Impact of size and thermal gradient on supercooling of phase change materials for thermal energy storage

Phase change material based thermal energy storage has many current and potential applications in the heating and cooling of buildings, battery and electronics thermal management, thermal textiles, and dry cooling of power plants. However, connecting lab scale thermal data obtained with differential scanning calorimetry (DSC) to the performance of large-scale practical systems has been a major challenge primarily due to the dependence of supercooling on the size and temperature gradient of the system. Here we show how a phase change material’s supercooling behavior can be characterized experimentally using common lab scale thermal analysis techniques. We then develop a statistics based theoretical model that uses the lab-scale data on small samples to quantitatively predict the supercooling performance for a general thermal energy storage application of any size, including also allowing for the possibility of temperature gradients. Finally, we validate the modeling methodology by comparing to experimental results for solid-solid phase change in neopentyl glycol, which shows how the model successfully predicts the changes in supercooling temperature across a large range of cooling rates (2 orders of magnitude) and volumes (3 orders of magnitude). By accounting for thermal gradients, the model avoids ~2x error incurred by lumped approximations.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Effect of grafting density on the two-dimensional assembly of nanoparticles

Employing grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we demonstrate that films composed of polyethylene glycol (PEG)-grafted silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), as well as their binary mixtures, form highly stable hexagonal structures at the vapor–liquid interface. These nanoparticles exhibit remarkable stability under varying environmental conditions, including changes in pH, mixing concentration, and PEG chain length. Short-chain PEG grafting produces dense, well-ordered films, while longer chains produce more complex, less dense quasi-bilayer structures. AuNPs exhibit higher grafting densities than AgNPs, leading to more ordered in-plane arrangements. In binary mixtures, AuNPs dominate the population at the surface, while AgNPs integrate into the system, expanding the lattice without forming a distinct binary superstructure. In conclusion, these results offer valuable insights into the structural behavior of PEG-grafted nanoparticles and provide a foundation for optimizing binary nanoparticle assemblies for advanced nanotechnology applications.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Mechanically graded granular scaffolds for osteochondral tissue engineering

Engineered scaffolds designed to approximate the mechanical microenvironment of the osteochondral unit often address this complexity using discrete, two-phase architectures that introduce mechanical discontinuities and interfacial stress concentrations rather than a contiguous stiffness transition. To address this challenge, we created a photoannealed polyethylene glycol (PEG) granular scaffold with a spatially controlled stiffness gradient within a cell-permissive, macroporous architecture. Stiffness was dictated by photoannealing microgels using a photomask. We tuned void volume and available surface area by varying microgel diameter and tested how mesenchymal stromal cells (MSCs) interpret local mechanical environments. MSCs exhibited position-dependent differences in morphology, cytoskeletal structure, matrix deposition, and lineage-specific gene expression within the gradient scaffolds. Softer regions supported rounded cell morphology and deposition of a glycosaminoglycan-rich matrix, whereas stiffer regions promoted cell elongation, increased cytoskeletal tension, and expression of mineral-associated markers. Gradients formed from smaller microgels magnified these spatial responses by increasing cellular confinement and adhesion site availability. Disruption of actomyosin contractility eliminated these regional differences, demonstrating that MSCs rely on tension-dependent mechanotransduction to interpret the gradient. These findings reveal that coupling microgel architecture with continuous stiffness transitions provides a tractable platform to study multiscale mechanobiologic regulation and spatially guide osteochondral tissue formation.

Biological and medical sciences↗
DOE OSTI2020

Solvent effects on the heterogeneous growth of TiO 2 nanostructure arrays by solvothermal synthesis

One-dimensional titanium dioxide (TiO 2 ) nanostructure arrays (nanoarrays) are important metal oxide nanomaterials that can be synthesized via facile solvothermal methods. The properties of the organic solvents can impose significant effects on the microstructures and properties of the final products. However, the discussions were limited to the homogeneously nucleated TiO 2 nanomaterials in free-standing powder form, while the solvent effects are less understood during the heterogeneous growth of TiO 2 nanoarrays on a substrate surface. In this work, six organic compounds, namely 2-butanone, n-decane, n-hexane, toluene, ethylene glycol and ethanol, were selected as the solvents for the solvothermal synthesis of TiO 2 nanoarrays on the cordierite monolithic substrates. Special attentions are paid to the morphology, crystallinity, specific surface area, and porosity of the samples. The heterogeneous growth of TiO 2 nanoarrays on substrate surfaces is found to favor the solvents with moderate dielectric constants, which can be partially dissolved in the aqueous solution and modulate the reaction rate during the solvothermal synthesis. Organic solvents with low dielectric constants may result in a complete separation between the precursors and aqueous solution, and therefore slow down the overall reaction, causing the insufficient growth of the nanoarrays. The TiO 2 nanoarrays are obtained with optimum morphology from the combination of 2-butanone and titanium (IV) butoxide as solvent and precusor, respectively, with a high specific surface area up to 56 m 2 /g including cordierite substrate given a micron thickness. When loaded with Pt catalyst, the TiO 2 nanoarray-based monolithic catalysts show excellent low-temperature catalytic activity and hydrothermal stability for the CO and hydrocarbon oxidation under the simulated exhausted conditions. This article shall shed light on a better understanding of the growth mechanism and rational design of TiO 2 nanoarrays for high-performance catalytic converters.

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

Synergistic effect of dual Brønsted acidic deep eutectic solvents for oxidative desulfurization of diesel fuel

Deep eutectic solvents (DESs) are generally used as attractive solvents or extractants rather than catalysts in the field of synthesis and separation. Herein, dual Brønsted acidic DESs were prepared by mixing sulfonated quaternary ammonium and oxalic acid as extractants and catalysts for deep oxidative desulfurization. Compared to the DESs with single acidic group, the dual acidic DESs exhibited much higher catalytic activity likely due to the synergistic effect. The 1 H NMR study indicated that the weak interaction between DES and sulfur compounds led to a low extraction capacity. However, the sulfur removal could reach 97.7% under optimized reaction conditions. Density functional theory (DFT) calculations demonstrated that sulfonic group and carboxylic group are of equal importance to desulfurization performance. Further, the desulfurization efficiency was also strongly affected by the viscosity of DESs. Here, we put forward a new strategy that the reaction time could be sharply shortened to 40 min and 100 min by adding low viscous acetonitrile and polyethylene glycol into DES to form mixing reaction system, respectively.

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

Controlling PET oligomers vs monomers via microwave-induced heating and swelling

The production of polyethylene terephthalate (PET) bottles and fibers, and their subsequent mismanagement, have created an urgent need to develop strategies to handle the resulting waste. Here, in this work, glycolysis of PET using manganese oxide catalysts under microwave-assisted heating is demonstrated to form oligomers and the monomer bis(2-hydroxyethyl) terephthalate (BHET) at moderate conditions. Higher surface area catalysts achieve faster overall rates of depolymerization to the monomer. Oligomers form homogeneously and depolymerize to monomers over manganese oxide. The polymer-to-solvent ratio and reaction temperature affect the overall oligomer yield. The swelling of PET, caused by the diffusion of ethylene glycol into the polymer matrix, causes the dissolution of the PET to form oligomers. Oligomers are characterized and show similar physical properties to the starting PET despite having 1/20th of the molecular weight.

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

Green co-solvent-assisted one-pot synthesis of high-performance flexible lignin polyurethane foam

Although lignin is a promising candidate as a source of polyol for producing eco-friendly polyurethane foam (PUF), its direct application has limitations, primarily stemming from the brittleness of the resulting products and poor processibility at high lignin loadings. To address these technical challenges, we introduced an effective co-solvent for the lignin-based polyurethane foams (LPUFs) with up to 80wt% of lignin substitution for petroleum polyols. As a green co-solvent that involves carbon dioxide fixation during its production, propylene carbonate (PC), was blended with lignin and improved the distribution of lignin by decreasing the viscosity, providing a room-temperature reaction. The LPUFs demonstrated a comparable thermal insulation performance (R-values greater than 5 in -1 ) with commercially available PUF with a uniform size of closed-cell structure induced by the reduced viscosity of lignin-based polyol. LPUFs also showed enhanced fire retardancy and moisture resistance compared to the control PUFs, benefiting from lignin’s intrinsic fire-resistant and hydrophobic properties. To mitigate the brittleness issue at high lignin loadings, flexible polyethylene glycols (PEGs) with a high molecular weight (i.e., PEG-1000) were dissolved in PC at room temperature to further improve the mechanical strength of LPUFs. The compressive strength of LPUFs with 80 wt% lignin substitution content was remarkably improved to 226 kPa by the employment of co-solvent and PEG-1000 compared to the control PUF (<140 kPa). Moreover, the flexibility of the LPUFs was successfully controlled by simply adjusting the PEG-400/PEG-1000 ratio. In conclusion, the results of this study provide valuable insights for accelerating and broadening the utilization of lignin in sustainable materials and manufacturing areas.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Novel insight into the kinetics of amide bond glycolysis for nylon-6 depolymerization

Chemical recycling of nylon-6 to short-chain oligomers and monomer ε-caprolactam via catalytic glycolysis is a potential solution for plastic waste remediation. Here, in this work, the kinetics of amide bond glycolysis (with ethylene glycol) in nylon-6 and the model compound N-phenethyl-3-phenylpropanamide (M1) were evaluated at 473 K in the presence of the cyclic amidine catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene. Rates of polymer glycolysis were determined by the time-dependent shift in molecular weight distribution, whereas rates of M1 glycolysis were determined using liquid chromatography. The similarity of the first-order rate constants for glycolysis of nylon-6 and M1 at 473 K with 0.03 M amidine catalyst (5 mol% relative to amide bonds), 1.22 × 10 −5 s −1 and 2.18 × 10 −5 s −1 , respectively, confirmed the suitability of M1 as a model compound for nylon-6 glycolysis. Similar rates of glycolysis in the presence of other cyclic amidine catalysts as well as sodium methoxide revealed little influence of base strength. Glycolysis rates were unexpectedly non-linear in catalyst loading and deactivation occurred with long reaction times, presumably by non-selective decomposition of products as detected by liquid chromatography.

Depolymerization rate and rate constant↗
DOE OSTI2023

Reinforced double-threaded slide-ring networks for accelerated hydrogel discovery and 3D printing

Traditionally, slide-ring gels are stretchable but soft as a result of an elasticity-stretchability trade-off. Herein, we introduce a new approach to breaking this trade-off and creating reinforced slide-ring networks with mobile crosslinkers. Our approach involves the construction of a polyethylene glycol double-threaded γ-cyclodextrin-based pro-slide-ring crosslinker that serves as a modular component for 3D printing and copolymerization. The resulting crystalline-domain-reinforced slide-ring hydrogels, or CrysDoS-gels, exhibit both high elasticity and high stretchability. The modular synthesis allows for high-throughput synthesis of CrysDoS-gels, generating a large amount of data for structure-property analysis. Here, by employing data science techniques, such as machine learning and linear regression, not only were we able to identify which chemical components influence the mechanical properties of CrysDoS-gels, but this analysis also aided in the discovery of better-performing CrysDoS-gels. Finally, we demonstrate the potential application of the newly discovered CrysDoS-gels as sensing devices by 3D printing them as stress sensors with high sensitivity and a broad detection range.

3D-printing↗
DOE OSTI2020

Influence of plasticizers on thermal and mechanical properties of biocomposite filaments made from lignin and polylactic acid for 3D printing

Polylactic acid (PLA) and organosolv lignin were mixed at different ratios and extruded to obtain PLA-lignin composite filaments. PLA was replaced with lignin up to 20 wt%. Two plasticizers (polyethylene glycol (PEG) 2000 and struktol TR451) were added in varying concentrations to enhance the properties of PLA_L20 (20% lignin in PLA) composite filaments. Furthermore, the effect of lignin in PLA, and PEG, and struktol in PLA_L20 composites was investigated via tensile test, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy of the filaments, and dynamic mechanical analysis of 3D printed samples. A 2 wt% PEG was able to enhance both tensile stress and elongation at maximum load of PLA_L20 composite by 19% and 35%, respectively, whereas struktol TR451 was able to improve elongation at maximum load by 24%.

3D printing↗
DOE OSTI2023

Polyester-based epoxy vitrimer integrating spent coffee ground as a natural filler

Coffee is a widely consumed beverage, but approximately 80% mass of coffee cherry is discarded as waste. Here, in this study, spent coffee grounds (SCG) were recycled and used as a natural filler in a polyester-based epoxy matrix made from reactions of diglycidyl ethers of Bisphenol A and polyethylene glycol with methyl nadic anhydride. The properties of SCG/epoxy composites with various SCG contents up to 40% w/w were evaluated using various techniques such as FT-IR spectroscopy, tensile testing, optical microscopy, differential scanning calorimetry, and rheology. The SCG filled polyester-based epoxy matrix demonstrated excellent dimensional stability and retained a permanently crosslinked network, but re-shaping was possible at ~150 °C through transesterification, which occurred due to a dynamic chain exchange reaction between the ester group of the epoxy matrix and the hydroxyl group of the SCG fillers. The transesterification also improved the interfacial adhesion between the matrix and SCG fillers, resulting in tensile strength of over 20 MPa and a modulus of around 2.5 GPa, even with high SCG contents up to 40% w/w. While neat, cured epoxy shows thermoset behavior, filling the matrix with SCG enables reforming and origami-inspired spontaneous change in shape.

42 ENGINEERING↗
DOE OSTI2021

Electrolyte effects on the electrochemical performance of microemulsions

Here, we report a study of the electrochemistry of Ferrocene (Fc) in a Tween®20 (polyethylene glycol (20) sorbitan monolaurate) /1-butanol/ water/Toluene (TBWT) microemulsion system, focusing on the effects of electrolyte components. Resistance and conductivity measurements are used along with Cyclic Voltammetry (CV) to characterize the effects of supporting electrolyte, such as Bu 4 NBF 4 and KNO 3 , on the electrochemical performance and transport properties of Fc. With increasing Fc-containing oil phase concentration in the microemulsion, the observed peak current density fails to increase proportionately with the Fc concentration. Adding 0.05 m Bu 4 NBF 4 in the oil phase significantly increases the current density, presumably by lowering the resistance of microemulsion and promoting the accessibility of Fc in the system. Moreover, increasing the aqueous phase supporting electrolyte from 0.5 m KNO 3 to 1 m KNO 3 does not exhibit an analogous effect. We discuss these results in the context of our working hypothesis for microemulsion organization and its implications for electron transfer to Fc.

Conductivity↗
DOE OSTI2022

Mechanically and thermally robust microporous copolymer separators for lithium ion batteries

Next generation, multifunctional separators can enhance energy storage, power, and safety performance of lithium ion batteries but must be simple to fabricate and incorporate with existing roll-to-roll manufacturing. Here, this study presents a strategy to facilely prepare these separators using UV-initiated polymerization-induced phase separation (PIPS), wherein microporous polymer separators are fabricated directly from constituent monomers and ethylene carbonate (EC) porogen. This enables a wide compositional design space as co-monomers with specific chemical functionality can be readily incorporated into the PIPS precursor mixture. Herein, 1,4-butanediol diacrylate (BDDA) was copolymerized with poly(ethylene glycol) diacrylate (PEGDA) to increase the acrylate conversion in the photopolymerization and improve mechanical properties. By tuning the ratio of PEGDA and EC, separators with high porosity (41.3%) and effective ionic conductivity (2.09 mS cm –1 ) were prepared. Inclusion of PEGDA was essential to increasing the elastic modulus to > 345 MPa, which is required for cell assembly by roll-to-roll manufacturing. All separators prepared were shown to enable reversible cycling of lithium metal/LiNi 0.5 Mn 0.3 Co 0.2 O 2 half-cells for 100 cycles. Unlike conventional polyolefin separators, which were shown to melt at 160 °C and shrink by up to 29.8% at elevated temperatures, the PIPS separators possess exceptional, safety-enhancing thermomechanical properties, undergoing no phase transitions or thermal shrinkage.

25 ENERGY STORAGE↗
DOE OSTI2023

Tuning and high throughput experimental screening of eutectic electrolytes with co-solvents for redox flow batteries

Eutectic solvents, with high salt concentrations and suppressed volatility, are promising alternatives to aqueous and volatile organic electrolytes for grid-scale energy storage devices such as redox flow batteries (RFBs). However, it is not known a priori which hydrogen bond acceptors and donors would form a eutectic solvent and at which compositions of these mixtures would yield desirable properties for RFBs. Specifically, the known deep eutectic solvents generally have high viscosities and low ionic conductivities, especially in the landscape of RFB electrolytes. We report a high throughput experimental (HTE) study was carried out to assess the properties of eutectic solvents based on choline chloride as the hydrogen bond acceptor and ethylene glycol and aniline as the hydrogen bond donors. In addition, water, acetonitrile, and dimethyl sulfoxide as co-solvents were examined in terms of tuning the viscosity, conductivity, and solubility of two redox-active species: methyl viologen dichloride hydrate (MVCl 2 ·H 2 O, or MV for simplicity) and 2,1,3-benzothiadiazole (BTZ) that are relevant to RFBs. The HTE framework enabled the development of a rapid and comprehensive understanding of the design of new eutectic electrolytes incorporating co-solvents to improve the physicochemical and electrochemical properties for RFBs.

25 ENERGY STORAGE↗
DOE OSTI2022

Constructing a multi-functional polymer network for ultra-stable and safe Li-metal batteries

We report the practical application of lithium (Li) metal electrodes is impeded by Li dendrite growth and unstable solid electrolyte interphase (SEI). Herein, a multi-grafting polymer network, poly(dimethyl siloxane)-g-[poly(poly(ethylene glycol) methyl ether methacrylate)-r-sodium poly(p-styrene sulfonate)] (PPS), is chemically synthesized from reversible addition-fragmentation chain transfer (RAFT) polymerization. With integrated stretchability, ionic conductivity, and mechanical robustness, it serves a dual role to stabilize the Li electrode. As artificial SEI layer, the PPS enables superior electrochemical performance in half cells, symmetric cells, and full cells (PPS@Li/LiFePO 4 , capacity retention of >70% after 600 cycles). Utilized as solid polymer electrolyte (SPE), the all-solid-state Li/SPE/LiFePO 4 full cell delivers excellent cycling performance with an unprecedented capacity retention of 90% over 1,700 cycles at 0.5 C and 81% over 1,000 cycles at 1.0 C. With high-voltage LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) as cathode, the Li/SPE/NMC811 cell exhibits an initial discharge capacity of 162.2 mAh g -1 with a capacity retention of 72% after 200 cycles. The assembled solid-state Li/SPE/LiFePO4 pouch cell with SPE exhibits stable cycling performance over 200 cycles with a capacity retention of 75% and still operates well even after curling, folding, and cutting, demonstrating great potential for achieving ultra-safe and high energy density batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Efficient separation and coprecipitation for simplified cathode recycling

Hydrometallurgical recycling of spent lithium-ion batteries is among the most promising recovery approaches. The current hydrometallurgical method for battery recycling faces challenges such as complex separation and precipitation processes, and environmental concerns from the use of caustic inorganic acid and hazardous hydrogen peroxide. Our proposed modified method, namely polyol-metallurgy, uses citric acid in ethylene glycol as dual-function green solution to overcome these obstacles. This bifunctional solution leaches valuable metal ions from cathode materials (e.g., LiCoO 2 ), and then acts as chelating agents to selectively precipitate cobalt through an esterification reaction, without the need for additional precipitation agents. The leaching efficiency of cobalt and lithium reaches 99.55% and 97.65%, respectively, and more than 96% of cobalt could be directly self-precipitated and recovered. Further, the unique characteristics of the dual-function solution also avoids impurities from Al foils and PVDF/carbon black films, enabling the simple separation process. Therefore, the process can be completed in one-pot system with efficient leaching, separation and coprecipitation, making it more efficient and feasible for operation than existing alternatives.

25 ENERGY STORAGE↗