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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Mechanism of O 2 /NO-Promoted Oxidative C–C Bond Cleavage in Linear Alkanes

Selective oxidation of alkanes to oxygenated products remains a fundamental challenge, particularly if the goal is to promote C−C bond cleavage while minimizing formation of CO 2 . Oxidation conditions that use O 2 and nitrogen oxides (NO x ) have been shown to be very effective in promoting radical-mediated functionalization and oxidative carbon−carbon cleavage in saturated hydrocarbon polymers, such as polyethylene. Here, we investigate the mechanism of O 2 /NO-mediated oxidation of ndecane as a prototypical linear alkane substrate. These reactions enable identification and quantification of reactive intermediates, including nitrites, nitrates, alcohols, and ketones. Under the reaction conditions, these species convert into common ketone intermediates that evolve into α-diketones and other α-functionalized ketones, which undergo further conversion into carboxylic acids. Infrared (IR) spectroscopy indicates that HDPE oxidation proceeds through similar key intermediates. Together, these findings establish a mechanistic framework for NO x -mediated alkane oxidation and provide a foundation for the development of broadly applicable oxidative transformations.

Anions↗
DOE OSTI2022

Improved Moisture Management Technology for Eco-N-Control Fertilizer

Three fertilizer technologies to manage nitrogen (N) release rates in soil dominate the market today: 1) bulk controlled-release technologies, which use the intrinsic solubility properties of a N-organic co-polymer to control N release; 2) barrier-based controlled-release technologies, which use porous polymer or sulfur coatings as a physical barrier to control N release from encapsulated N nutrients; and 3) slow-release technologies, which use enzyme inhibitors to chemically slow down the transformation of N nutrients into ammonia (NH 3 ) or to temporarily reduce populations of bacteria in the soil that are responsible for converting ammonium (NH 4 + ) to highly soluble nitrates. These technologies are expensive and provide only limited control of N-release rates. Also, from another environmental perspective, synthetic polymer coatings do not decompose easily and will accumulate over time with continuous application of fertilizer. For most of the past two decades we have been developing the Eco-N-Control solid-nitride fertilizer technology, a type of bulk controlled-release technology. With Eco-N-Control, solid-nitride compounds weather like a mineral, slowly releasing N at a rate determined by their composition. Testing by an industrial collaborator, however, showed that earlier versions of Eco-N-Control released at 25% of the desired rate when deployed in unsaturated soils. The overall goal of the current project, therefore, was to strengthen our IP position and the potential for licensing of Eco-N-Control solid-nitride fertilizer technology by developing new ways to manage the level of moisture in contact with the fertilizer when applied to soil thereby ensuring the desired N-release rate. We achieved this goal by developing a biodegradable polymer cross-linking approach that substantially improved performance of our patented solid-nitride fertilizer. We found that cross-linking an environmentally friendly and biodegradable polymer with a mixture of solid nitrides, other N-nutrient compounds and other additives offers several advantages: 1) mechanical robustness of fertilizer beads, 2) chemical stability during storage, 3) maintenance of sufficient water content in the vicinity of the nitride, and 4) control of N-release rates. We also updated our N-release testing protocol to more realistically simulate the conditions found in soil. Finally, we filed an invention disclosure record to protect these new aspects of Eco-N-Control technology, which offers a potential way to lower both agricultural and industrial pollution by providing an efficient N-delivery mechanism to plants.

42 ENGINEERING↗
DOE OSTI2023

The genome-scale metabolic model for the purple non-sulfur bacterium Rhodopseudomonas palustris Bis A53 accurately predicts phenotypes under chemoheterotrophic, chemoautotrophic, photoheterotrophic, and photoautotrophic growth conditions

The purple non-sulfur bacterium Rhodopseudomonas palustris is recognized as a critical microorganism in the nitrogen and carbon cycle and one of the most common members in wastewater treatment communities. This bacterium is metabolically extremely versatile. It is capable of heterotrophic growth under aerobic and anaerobic conditions, but also able to grow photoautotrophically as well as mixotrophically. Therefore R . palustris can adapt to multiple environments and establish commensal relationships with other organisms, expressing various enzymes supporting degradation of amino acids, carbohydrates, nucleotides, and complex polymers. Moreover, R . palustris can degrade a wide range of pollutants under anaerobic conditions, e.g., aromatic compounds such as benzoate and caffeate, enabling it to thrive in chemically contaminated environments. However, many metabolic mechanisms employed by R . palustris to breakdown and assimilate different carbon and nitrogen sources under chemoheterotrophic or photoheterotrophic conditions remain unknown. Systems biology approaches, such as metabolic modeling, have been employed extensively to unravel complex mechanisms of metabolism. Previously, metabolic models have been reconstructed to study selected capabilities of R . palustris under limited experimental conditions. Here, we developed a comprehensive metabolic model (M-model) for R . palustris Bis A53 ( i DT1294) consisting of 2,721 reactions, 2,123 metabolites, and comprising 1,294 genes. We validated the model using high-throughput phenotypic, physiological, and kinetic data, testing over 350 growth conditions. i DT1294 achieved a prediction accuracy of 90% for growth with various carbon and nitrogen sources and close to 80% for assimilation of aromatic compounds. Moreover, the M-model accurately predicts dynamic changes of growth and substrate consumption rates over time under nine chemoheterotrophic conditions and demonstrated high precision in predicting metabolic changes between photoheterotrophic and photoautotrophic conditions. This comprehensive M-model will help to elucidate metabolic processes associated with the assimilation of multiple carbon and nitrogen sources, anoxygenic photosynthesis, aromatic compound degradation, as well as production of molecular hydrogen and polyhydroxybutyrate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Confocal Raman Microscopy as an In Situ Probe of Volume Change in Hydration-Sensitive Polymer Membranes

An approach is described for measuring hydration-induced volume change within ion conductive polymer membranes and thin films by adapting the technique of confocal Raman microscopy. With careful consideration of factors that affect excitation and scattering within the confocal probe volume region, material swelling and deswelling were estimated from the intensities of polymer matrix spectral features. A high numerical aperture oil-immersion objective was used to achieve tight focusing within samples and the efficient collection of Raman scattered light. The approach is demonstrated for a fluorinated cation-exchange ionomer (Nafion) and the hydrocarbon anion-exchange ionomer Sustainion. Samples were monitored while under a nitrogen atmosphere that was cycled between dry and humid (∼50% relative humidity, RH) states. The volume changes estimated from the Raman spectra were in close agreement with those derived from conventional measurements. The reported work advances understanding needed to adapt confocal Raman microscopy for quantitative in situ and operando studies of ionomers within electrochemical devices, such as polymer electrolyte membrane fuel cells and electrolyzers, and lays a foundation for broader applications in the study of hydration-induced polymer swelling and the associated molecular level water and polymer framework structural changes.

Absorption↗
DOE OSTI2024

Molecular structures of residual solvent in polyacrylonitrile based electrolytes: Implications for conductivity and stability

Lithium-ion batteries increasingly play significant roles in modern technologies; however, increased energy density also raises concerns about electrolyte safety. Traditional electrolytes that use volatile organic solvents face risks of thermal runaways and fires from electrode shorting. In response, polymer-based solid electrolytes have been developed for replacement. Polyacrylonitrile (PAN) is a promising fire-resistant component for electrolyte fabrication, but its limited solubility necessitates using low-volatility solvents, which are notoriously difficult to remove in subsequent drying processes. Here, we use femtosecond two-dimensional infrared spectroscopy to provide an in-depth understanding of how residual solvent from processing affects the molecular structures and dynamics within a polymer electrolyte. To this end, linear and nonlinear infrared spectroscopies are employed to interrogate the molecular interactions in PAN-based electrolytes containing various contents of N,N-dimethylformamide (DMF). We show that the amount of DMF within the PAN electrolyte affects the Li+ structure. Further, the coordination can proceed through the carbonyl group and/or the amide nitrogen to form antiparallel structures with the nitrile groups of PAN through dipole–dipole interactions. The free motion of DMF is drastically inhibited upon interaction with Li+ and PAN, which decreases the ionic conductivity and potentially affects the stability (resistance toward removal and chemical decomposition). These findings have implications for the design and processing of solid polymer electrolytes.

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

Enhanced Anhydrous Proton Conductivity in Azole Phosphonic Acid Mixtures

Azole molecules are investigated as potential candidates for proton conductors under anhydrous conditions. Since 1,2,3-triazole has the lowest melting point (T m = 17 °C), it was blended with three phosphonic acid-containing molecules (small molecules with one and two phosphonic acids per molecule and a phosphonic acid polymer) to provide a source of excess protons to enhance the proton conductivity of the blends. Here we study a wide range of compositions in each system to find that these three mixtures show a maximum proton conductivity at moderate doping compositions, approximately 5–10 azole molecules per phosphonic acid group. Using NMR diffusometry, we show that the protons bonded to nitrogen move faster than the protons bonded to carbons of 1,2,3-triazole, suggesting proton hopping between azole proton carriers. Given the high proton conductivity at 90 °C of the best mixtures, in the range of 20–60 mS/cm, this work provides a path forward for future work in anhydrous proton-conducting polymer membranes. Additionally, Raman spectroscopy was used to accurately determine the molar percentage of protonated 1,2,3-triazole. Combining that with the proton diffusion results, we find that the phosphonic acid polymer shows the most proton hopping at low acid content.

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

Membranes for gas separation

Membranes, methods of making the membranes, and methods of using the membranes are described herein. The membranes can comprise a support layer, and a selective polymer layer disposed on the support layer. In some cases, the support layer can comprise a gas permeable polymer and hydrophilic additive dispersed within the gas permeable polymer. In some cases, the selective polymer layer can comprise a selective polymer matrix and carbon nanotubes dispersed within the selective polymer matrix. The membranes can exhibit selective permeability to gases. As such, the membranes can be for the selective removal of carbon dioxide and/or hydrogen sulfide from hydrogen and/or nitrogen.

Ho, W. S. Winston↗
DOE OSTI2022

The Anionic Polymerization of a tert-Butyl-Carboxylate-Activated Aziridine

N-Sulfonyl-activated aziridines are known to undergo anionic-ring-opening polymerizations (AROP) to form polysulfonyllaziridines. However, the post-polymerization deprotection of the sulfonyl groups from polysulfonyllaziridines remains challenging. In this report, the polymerization of tert-butyl aziridine-1-carboxylate (BocAz) is reported. BocAz has an electron-withdrawing tert-butyloxycarbonyl (BOC) group on the aziridine nitrogen. The BOC group activates the aziridine for AROP and allows the synthesis of low-molecular-weight poly(BocAz) chains. A 13C NMR spectroscopic analysis of poly(BocAz) suggested that the polymer is linear. The attainable molecular weight of poly(BocAz) is limited by the poor solubility of poly(BocAz) in AROP-compatible solvents. The deprotection of poly(BocAz) using trifluoroacetic acid (TFA) cleanly produces linear polyethyleneimine. Overall, these results suggest that carbonyl groups, such as BOC, can play a larger role in the in the activation of aziridines in anionic polymerization and in the synthesis of polyimines.

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

A Unique Bacterial Pelletized Cultivation Platform in Rhodococcus opacus PD630 Enhanced Lipid Productivity and Simplified Harvest for Lignin Bioconversion

Pelletized liquid cultivation has been widely explored because of its advantages in biomanufacturing, such as easier biomass harvesting, higher product yield, and lower medium viscosity and energy consumption. In this study, we discovered that the nonfilamentous bacterium Rhodococcus opacus PD630 could form pellets during the fermentation of alkaline pretreatment liquor containing lignin as a carbon source. This discovery advanced our understanding of bacterium pelletization, as only filamentous fungi and filamentous bacteria were reported to form pellets without the addition of external agents such as flocculants or polymers in previous research. Several factors were investigated to understand how they affect the process of pelletization. Notably, the lipid content in the pellets was much higher than in the scattered bacteria at low nitrogen concentration (<0.5 g/L), under which condition (high carbon to nitrogen ratio) the industrial microbial production for lipids was carried out. Moreover, the highest pellet percentage (~60% of the total biomass) was observed at 30 g/L soluble solid content, an agitation rate of 180 rpm, 1.4 g/L NH 4 NO 3 , an initial optical density (OD 600 ) of 10, and a centrifugation speed of 6000 rpm. Further, the study also opens new avenues to decrease harvesting and cultivation cost as well as energy consumption for microbial fermentation.

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

Cost-effective carbon fiber precursor selections of polyacrylonitrile-derived blend polymers: carbonization chemistry and structural characterizations

Blending polyacrylonitrile (PAN) with plastic wastes and bio-based polymers provides a convenient and inexpensive method to realize cost-effective carbon fiber (CF) precursors. In this work, PAN-based blend precursors are investigated using ReaxFF reactive molecular dynamics simulations with respect to the formation of all-carbon rings, the evolutions of oxygen-containing and nitrogen-containing species, and the migration of carbon atoms to form turbostratic graphene. From these simulations, we identify that PAN/cellulose (CL) blend manifests the highest carbon yield and the most substantial all-carbon ring formation. This ReaxFF-based finding is confirmed by Raman and TEM experiments indicating high crystallinity for PAN/CL-derived blend CFs. We trace the pathway of gasification and carbonization of PAN/CL to elaborate the mechanism of the formation of all-carbon ring networks. We discover that the acetals of CL can catalyze the cyclization of the blend precursor, allowing for the search for CL derivatives or the other kinds of bio-based polymers with similar functionalities as alternative blends. In addition, we examine the structural characteristics using the carbon–carbon (C–C) radial distribution functions, C–C bond length distributions, and sp2 C atom ratios for the four representative precursors, i.e., PAN, oxidized PAN, PAN/nylon 6,6, and PAN/CL. Our simulation results show the most extensive all-carbon ring cluster and graphitic structure growths for PAN/CL. Here, we propose PAN/CL as a cost-effective alternative CF precursor, since (a) CL is naturally abundant and eco-friendly for production, (b) the blend precursor PAN/CL does not require oxidation treatment, (c) PAN/CL has a high carbon yield with substantial all-carbon ring formation, and (d) PAN/CL based CFs potentially provide a mechanical property enhancement.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Adaptive learning-driven high-throughput synthesis of oxygen reduction reaction Fe–N–C electrocatalysts

Reducing human reliance on inefficient energy systems and fossil fuels has become more urgent due to the consequences of global climate change. However, traditional trial-and-error approaches have hampered our ability to accelerate the discovery and implementation of functional materials for efficient energy conversion devices, such as polymer electrolyte fuel cells (PEFCs). To address this, we develop an adaptive learning framework that integrates machine learning and state-of-the-art capabilities in high-throughput synthesis to achieve expedited optimization of iron-nitrogen-carbon PEFC oxygen reduction reaction (ORR) electrocatalysts. We use statistical inference, uncertainty quantification, and global optimization to build a computational design-of-experiment tool that identifies the optimum compositions to be investigated next to reduce the demands placed on experimental materials discovery. We benchmark the ability of the proposed strategy to discover optimum catalyst synthesis conditions in a six-dimensional search space when starting with a thirty-six-sample database. By following the adaptive learning strategy, we synthesize fourteen new catalysts from approximately ten billion unique compositions and discover four catalysts that outperform all original samples. The best machine learning-optimized catalyst is 33% more active than the highest-performing one in the initial database, showing an ORR activity seven times larger than those typically reported for the same class of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Probing Heterogeneous Degradation of Catalyst in PEM Fuel Cells under Realistic Automotive Conditions with Multi-Modal Techniques

The heterogeneity of polymer electrolyte fuel cell catalyst degradation is studied under varied relative humidity and types of feed gas. Accelerated stress tests (ASTs) are performed on four membrane electrode assemblies (MEAs) under wet and dry conditions in an air or nitrogen environment for 30 000 square voltage cycles. The largest electrochemically active area loss is observed for MEA under wet conditions in a nitrogen gas environment AST due to constant upper potential limit of 0.95 V and significant water content. The mean Pt particle size is larger for the ASTs under wet conditions compared to dry conditions, and the Pt particle size under land is generally larger than under the channel. Observations from ASTs in both conditions and gas environments indicate that water content promotes Pt particle size growth. ASTs under wet conditions and an air environment show the largest difference in Pt particle size growth for inlet versus outlet and channel versus land, which can be attributed to larger water content at outlet and under land compared to inlet and under channel. From X-ray fluorescence experiments Pt particle size increase is a local phenomenon as Pt loading remains relatively uniform across the MEA.

25 ENERGY STORAGE↗
DOE OSTI2026

Diethylenetriamine-functionalized graphene oxide: Insights into ion adsorption and applications in rare earth element separation

The growing demand for critical minerals and materials requires atom- and energy-efficient, selective separations to overcome the challenges posed by the similar chemical and physical properties of the rare earth elements (REEs) and their low concentrations in unconventional domestic feedstocks. Here, in this study, we developed diethylenetriamine-functionalized graphene oxide (DETA-GO) as a membrane material for REE adsorption and separation. Synthesis conditions were optimized to maximize nitrogen incorporation while also preserving GO dispersibility for facile membrane fabrication. We investigated the mechanism of amine functionalization, the nitrogen-bonding configurations, the organization of the interlayer transport channels, and the resulting effects on ion and water transport for REE separations. Neat-GO and DETA-GO multilayer laminate membranes were fabricated by vacuum filtration onto polymer supports. To investigate the effects of amine functionalization, the membranes were characterized using scanning electron microscopy, Raman, Fourier transform infrared, and X-ray photoelectron spectroscopy, as well as grazing-incidence X-ray diffraction measurements. Ion permeation experiments with representative lanthanum (La 3+ ) and ytterbium (Yb 3+ ) solutions revealed enhanced ion adsorption and water transport through DETA-GO membranes compared to neat-GO. The strong affinity of the membranes for multivalent REEs was also validated with conductivity and inductively coupled plasma mass spectrometry measurements. Atomistic insight into the role of amine functionalization in modulating nanochannel architecture and long-term stability, optimizing adsorption sites, and regulating REE and water transport was obtained using classical molecular dynamics simulations. Collectively, our joint experimental and theoretical study demonstrates the potential of DETA-GO membranes for selective REE separations, offering insights into ion-binding mechanisms, water-transport properties, and nanochannel optimization for the recovery of critical materials from aqueous feedstocks.

Adsorbent↗
DOE OSTI2022

Outgassing of casted and 3D printed silicones

Outgassing of 3D printed and casted silica-filled silicones was studied using a standard ASTM E-595 procedure and a modified Soreq’s method that allows very sensitive measurements of the outgassing kinetics even at low temperatures, 20 – 50 °C. We studied three different silica-filled silicones, non-porous cased M9787, and 3D printed LL50 and 40P materials. The present report shows that vacuum outgassing products of polysiloxane-based materials include multiple species. In addition to chemisorbed and physisorbed water outgassing, previously studied by TPD, polymer fragments of varying sizes evaporate as well. The chemical composition of the condensable volatile species collected on a Germanium substrate, was analyzed by FTIR. It was shown that all studied materials produce mostly PDMS-based outgassing products that form stable droplet-like structure on the Ge substrate. The highest amount of the condensable volatile species was measured for LL50. Isothermal TGA in nitrogen atmosphere of the LL50 material was compared to the standard vacuum outgassing. The results of TGA showed lower mass loss and higher water regain. The kinetics of the outgassing at relatively low temperatures of 20, 30 and 50 °C was studied using Thermoelectric Quartz Crystal Microbalance (TQCM). The TQCM surface was held at -10 °C to enhance condensation of the outgassed moisture. The analysis presented here, when combined with the extensive previous work on moisture outgassing, provides a better understanding of the aging mechanism of polysiloxane-based materials. In this work we show that outgassing techniques, usually applied for qualification of polymers for space-related applications, may be used as a complementary method to study thermal degradation and aging of silica-based silicones. Our results indicate that the long-term degradation mechanics and thermal degradation products depend primarily on the chemical composition of silicone-based material and only slightly affected by the manufacturing process. Surprisingly, the surface-to-volume ratio of the 3D printed vs. casted/molded materials showed only minor effect on the outgassing kinetic parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Low-temperature carbonization of polyacrylonitrile/graphene carbon fibers: A combined ReaxFF molecular dynamics and experimental study

Graphene inclusion in a polymer matrix is a promising route to significantly enhance the mechanical properties of low-grade carbon fibers (CFs). Using ReaxFF molecular dynamics simulation, the atomistic mechanism leading to this enhancement is investigated. We demonstrate that the graphene edges along with the nitrogen and oxygen functional groups play a catalytic role and act as seeds to expedite alignment of the all-carbon rings, which are starting sites for the growth of graphitic structures. To examine the role of this proposed mechanism that enhances the graphitic structure of PAN/graphene CFs, we discuss the experimental results wherein the PAN/graphene CFs carbonized at 1250 C demonstrate 91% (from 632 to 1207 MPa) increase in strength and 101% (from 88 to 177 GPa) enhancement in Young’s modulus compared to PAN-based CFs carbonized at 1500 C. In conclusion, these enhanced mechanical properties of low-grade carbon fibers achieved via graphene inclusion at decreased carbonization temperature provide a means to realize both energy savings and cost reduction.

42 ENGINEERING↗
DOE OSTI2023

Molecular dynamics study of carbon dioxide and nitrogen selectivity through poly[bis((methoxyethoxy)ethoxy)phosphazene] (MEEP) membrane

Here, a molecular dynamics simulation model was developed to comprehensively understand carbon dioxide over nitrogen (CO 2 /N 2 ) selectivity through polyphosphazene-based membrane comprising of poly[bis((methoxyethoxy)ethoxy)phosphazene] (MEEP) selective layer at the molecular level. The effects of temperature, pressure, and initial feed gas composition on the CO 2 transport on a polymer membrane were studied. The computed free energy and density profile of the permeating gas mixture exhibited that CO 2 molecules express higher interactions with the membrane than N 2 molecules, resulting in higher CO 2 /N 2 selectivity. Statistical analysis of gas molecules (CO 2 , water (H 2 O), and N 2 ) transportation suggested that hydro- and CO 2 -philic functional groups in the membrane significantly impact CO 2 permeability and CO 2 /N 2 selectivity. This study suggested that Lewis acid–base and hydrogen bonding combinations contribute to CO 2 permeation and CO 2 /N 2 selectivity. An equal CO 2 /N 2 selectivity was observed with and without water vapor in the feed gas suggesting that water does not hinder CO 2 transport through the membrane.

36 MATERIALS SCIENCE↗
DOE OSTI2023

ElectroCat: Platinum-Group-Metal-Free Engineered Framework Nano-Structure Catalyst (Final Technical Report)

Traditional synthesis methodologies that produce durable, highly active PGM-free electrocatalysts typically consist of a top-down approach utilizing a nitrogen-coordinating precursor, a metal precursor, and a support material. Nitrogen-coordinated transition metal complexes typically are absorbed onto a support material, which is then activated via high-temperature pyrolysis. Selection of the support and the nitrogen coordinating precursor has long been the focal point of efforts to maximize the number of accessible, catalytically active sites. In this project, GWE in collaboration with SRNL and NU will develop durable, highly active, low-cost, PGM-free electrocatalysts for polymer electrolyte membrane fuel cells designed and synthesized using a unique, bottom-up, rationally designed approach. Electrocatalysts are produced via polymerization reaction followed by a high-temperature pyrolysis step. Additionally, this project focuses on catalyst site and ORR mechanistic modeling to better understand the structure-property relationship.

08 HYDROGEN↗