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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Fluoride-Catalyzed Siloxane Exchange as a Robust Dynamic Chemistry for High-Performance Vitrimers

Sustainable development of new technologies requires materials having advanced physical and chemical properties while maintaining reprocessability and recyclability. Vitrimers are designed for this purpose; however, their dynamic covalent chemistries often have drawbacks or are limited to specialized polymers. Here, fluoride-catalyzed siloxane exchange is reported as an exceptionally robust chemistry for scalable production of high-performance vitrimers through industrial processing of commodity polymers such as poly(methyl methacrylate), polyethylene, and polypropylene. The vitrimers show improved resistance to creep, heat, oxidation, and hydrolysis, while maintaining excellent melt flow for processing and recycling. Furthermore, the siloxane exchange between different vitrimers during mechanical blending results in self-compatibilized blends without any compatibilizers. In conclusion, this offers a general, scalable method for producing sustainable high-performance vitrimers and a new strategy for recycling mixed plastic wastes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Demonstration of Complete Recycling Processes of Reversible Epoxies Using Solar Energy Conversion

Reversible epoxies using the Diels–Alder chemistry enables recycling processes through depolymerizing the polymer at higher temperature and then repolymerizing upon cooling. Compared to conventional bulk heating, photothermal heating can save time and resource and, consequently, reduce costs to reach an elevated temperature for recycling processes of the reversible epoxies. In previous studies, self‐healing of cracks and reattachments of two broken pieces have been presented using a laser; however, recycling of a sample as a whole is not feasible by using such a point light source. Herein, complete recycling processes are demonstrated utilizing an area light source, i.e., sunlight. Reversible epoxies are incorporated with carbon black and refractory plasmonic titanium nitride nanoparticles (NPs). Under concentrated (10 times) sunlight, they can generate sufficient heat (≈140 °C) to completely liquefy, reprocess, and reshape the samples multiple times. Recycling processes are validated by evaluation of mechanical properties for each cycle. Using an integrated experimental and theoretical approach, photothermal performance is investigated in terms of the dispersion and loading of photothermal NPs in the matrix, as well as the sample thickness. In this study, an insight is provided into the design of polymer/photothermal nanomaterial composites which can be sustainably recycled using abundant solar energy.

14 SOLAR ENERGY↗
DOE OSTI2016

Adsorption of iodine on hydrogen-reduced silver-exchanged mordenite: Experiments and modeling

The adsorption process of iodine, a major volatile radionuclide in the off-gas streams of spent nuclear fuel reprocessing, on hydrogen-reduced silver-exchanged mordenite (Ag 0 Z) was studied at the micro-scale. The gas-solid mass transfer and reaction involved in the adsorption process were investigated and evaluated with appropriate models. Optimal conditions for reducing the silver-exchanged mordenite (AgZ) in a hydrogen stream were determined. Kinetic and equilibrium data of iodine adsorption on Ag 0 Z were obtained by performing single-layer adsorption experiments with experimental systems of high precision at 373–473 K over various iodine concentrations. Results indicate approximately 91% to 97% of the iodine adsorption was through the silver-iodine reaction. The effect of temperature on the iodine loading capacity of Ag 0 Z was discussed. In conclusion, the Shrinking Core model describes the data well, and the primary rate controlling mechanisms were macro-pore diffusion and silver-iodine reaction. © 2016 American Institute of Chemical Engineers AIChE J, 2016

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

Spectroscopic and Computational Characterization of Diethylenetriaminepentaacetic Acid/Transplutonium Chelates: Evidencing Heterogeneity in the Heavy Actinide(III) Series

Abstract The chemistry of trivalent transplutonium ions (Am 3+ , Cm 3+ , Bk 3+ , Cf 3+ , Es 3+ …) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. Herein, we present the first extended X‐ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal–oxygen nearest‐neighbor bond lengths in the case of Cf 3+ . Corroborating those results, density functional theory calculations, extended to Es 3+ , suggest that the shorter Cf−O and Es−O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [M III DTPA(H 2 O)] 2− (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.

Deblonde, Gauthier J. ‐P.↗
DOE OSTI2018

Spectroscopic and Computational Characterization of Diethylenetriaminepentaacetic Acid/Transplutonium Chelates: Evidencing Heterogeneity in the Heavy Actinide(III) Series

The chemistry of trivalent transplutonium ions (Am 3+ , Cm 3+ , Bk 3+ , Cf 3+ , Es 3+ …) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. We present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal–oxygen nearest-neighbor bond lengths in the case of Cf 3+ . Corroborating those results, density functional theory calculations, extended to Es 3+ , suggest that the shorter Cf-O and Es-O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [M III DTPA(H 2 O)] 2- (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2024

Photooxidation of Polyolefins to Produce Materials with In-Chain Ketones and Improved Materials Properties

Herein, we report a selective photooxidation of commodity postconsumer polyolefins to produce polymers with in-chain ketones. The reaction does not involve the use of catalyst, metals, or expensive oxidants, and selectively introduces ketone functional groups. Under mild and operationally simple conditions, yields up to 1.23 mol % of in-chain ketones were achieved. Installation of in-chain ketones resulted in materials with improved adhesion of the materials and miscibility of mixed plastics relative to the unfunctionalized plastics. The introduction of ketone groups into the polymer backbone allows these materials to react with diamines, forming dynamic covalent polyolefin networks. This strategy allows for the upcycling of mixed plastic waste into reprocessable materials with enhanced performance properties compared to polyolefin blends. Mechanistic studies support the involvement of photoexcited nitroaromatics in consecutive hydrogen and oxygen atom transfer reactions.

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

Chemically Recyclable and Tunable Polyolefin-Like Multiblock Copolymer Adhesives

Adhesives are important in creating multilayer products, such as in packaging and construction. Most current hot-melt adhesives such as poly(ethylene-co-vinyl acetate) (EVA) and polyurethanes lack chemical recyclability and do not easily de-bond, complicating recycling. Here, we achieved tunable adhesive properties of chemically recyclable polyolefin-like multiblock copolymers through regulating the incorporation of crystalline hard blocks, amorphous soft blocks, and ester content highlighted by adhesive strengths up to 6.80 MPa. We further demonstrated applications of these adhesives in multi-layer films and showed that the adhesives can be readily de-bonded, recovered, and chemically recycled. Overall, this study into structure-property relationships, including effects of crystallinity, soft-block incorporation, and ester content of the multiblock copolymers on adhesive properties, has resulted in a modular hot-melt adhesive platform that exhibits chemical recyclability for virgin-quality adhesive re-generation, reprocessability for repeated reuse of the recovered adhesive, and tunability for designing adhesives with a wide range of low to high (up to ~80% stronger than EVA) adhesion strengths.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Evaluation of Iron‐Phosphate Glass–Ceramic Waste Form for Electrorefiner Salt Waste Simulant Dechlorinated With Phosphoric Acid

The importance of glass and glass–ceramic nuclear waste forms has been reaffirmed in recent years by the growing interest in nuclear power as a reliable energy source. Determination of processing methods for the disposal of halide-containing wastes will be essential for the advancement of nuclear technologies such as non-aqueous fuel reprocessing. Phosphate-based dechlorination and subsequent vitrification of radioactive salt waste into an iron-phosphate waste form have been identified as a potential processing scheme for electrochemical processing waste. The impact of H 3 PO 4 -based dechlorination of complex salt mixtures on the vitrification process and structure of the final iron-phosphate waste form has not yet been investigated. In this work, iron-phosphate glass–ceramics were made from simulant salt waste (48LiCl–33KCl–19NaCl mol%) dechlorinated with the H3PO4-based method. The glass-forming region was compared to that of traditionally prepared Na 2 O–Fe 2 O 3 –P 2 O 5 systems. For a candidate glass-forming composition, the processing scheme presented here was determined to favor Fe 3+ species. The O/P molar ratio was consistent for the candidate composition when dechlorinated at 400°C and 600°C in air and argon environments, indicating glass network connectivity was maintained despite variations in processing parameters. The results presented here validate processing schemes requiring iron-phosphate waste form synthesis following H 3 PO 4 -based dechlorination.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Extension of the Plutonium Oxide Nanocluster Family to Include {Pu 16 } and {Pu 22 }

Plutonium(IV) oxide nanoclusters represent an interesting scientific problem regarding structure-function relationships and are also relevant to global concerns surrounding plutonium reprocessing, the remediation of plutonium-contaminated soils, and the storage or disposal of plutonium-containing wastes. Here we report the synthesis of five unique Pu IV oxide nanoclusters containing 38,22, or 16 metal centers and capped only with inorganic ligands, such as chlorine and water, which prevent formation of the extended PuO 2 structure. The products are interrogated through single-crystal X-ray diffraction, bond valence calculations, and comparisons to other known metal-oxide nanoclusters. Of particular interest is the in-corporation of hydroxide linkages into the smaller plutonium oxide nanoclusters, which underscores previous observations and hypotheses regarding the formation of plutonium polymers and colloids.

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

Gamma Radiation-Induced Degradation of Acetohydroxamic Acid (AHA) in Aqueous Nitrate and Nitric Acid Solutions Evaluated by Multiscale Modelling

Acetohydroxamic acid (AHA) has been proposed for inclusion in advanced, single-cycle, used nuclear fuel reprocessing solvent systems for the reduction and complexation of plutonium and neptunium ions. For this application, a detailed description of the degradation of AHA in dilute aqueous nitric acid is required. To this end, we present a comprehensive, multiscale computer model for the coupled radiolytic and hydrolytic degradation of AHA in aqueous sodium nitrate and nitric acid solutions. Rate coefficients for the reactions of AHA and HA with the oxidizing nitrate radical were measured for the first time using pulsed electron radiolysis and used as inputs in the kinetic model. The computer model results are validated by comparison to experimental data from steady state gamma irradiations, for which the agreement is excellent. Here, the presented model accurately predicts the yields of the major degradation products of AHA: acetic acid, hydroxylamine, nitrous oxide, and molecular hydrogen.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Closed‐Loop Recyclable Vitrimer Plastics from PET Waste: A Design for Circularity

Plastics are essential to modern society, but their low recycling rates and inefficient end-of-life management pose a significant environmental challenge. Herein, the efficient strategy for upcycling postconsumer poly(ethylene terephthalate) (PET) waste into robust, closed-loop recyclable vitrimer plastics and composites is presented to address this issue. The catalyst-free aminolysis utilizes readily available amines to deconstruct diverse PET wastes into macromonomers, which are upcycled into vitrimers, exhibiting superior mechanical properties and exceeding the ultimate tensile stress and Young's Modulus of virgin PET by 80% and 150% respectively. These vitrimers exhibit excellent healability, shape memory, thermal reprocessability, and closed-loop chemical recyclability, enabling quantitative macromonomer recovery even from mixed plastic waste streams and glass/carbon fiber reinforced vitrimer (G/CFRV) composites. Furthermore, the vitrimer resin yields robust GFRV and CFRV composites with tensile strengths exceeding those of traditional epoxy composites by 100% and 80%, respectively, while maintaining complete chemical recyclability of both constituent materials. A preliminary technoeconomic analysis confirms the costeffectiveness and competitiveness of the facile PET deconstruction approach, which is potentially adaptable to other condensation polymers. Further, this study presents a facile approach to upcycling plastic waste into circular plastics and composites, offering a sustainable solution to global plastic waste management and fostering a circular economy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Synthesis and Characterization of Non-Aqueous [Tc X M-PW11O39] n – with M = O, N: Comparing Tc V and Tc VI in Metal Oxide Matrices

Technetium-99, a prevalent by-product of the nuclear fuel cycle, is a transition metal with 9 accessible oxidation states and a half-life of 2.1 × 10 5 years. 99 Tc VII has been found in the environment surrounding National Lab sites and fuel reprocessing centers, and its separation and long-term storage is complicated by its extensive redox chemistry. In our prior work we have reported the synthesis and reduction of Tc V O to Tc IV O in α 1- and α 2 -Wells–Dawson P 2 W 17 O 61 10- polyoxometalates and reported on the polyoxometalate features that promote reduction and stabilization. In this work we report on the oxidation state stabilization of Tc V O, Tc VI O and Tc VI N within the α-Keggin PW 11 O 39 7- polyoxometalate. Both Density Functional Theory and experimental results show that Tc in TBA 4 [Tc VI N-PW 11 O 39 ] can be reduced to TcV, but any subsequent electrons reduce the tungsten framework of the polyoxometalate. TBA 4 [Tc V O-PW 11 O 39 ] however, can be theoretically reduced down to Tc(I) before reduction of the polyoxometalate occurs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Advanced Nanomaterials for Nuclear Energy and Nanotechnology

The use of the latest engineered nanomaterials in nuclear energy systems has opened doors for improving the performance and safety of nuclear power. Nuclear nanotechnology (NNT) deals with the use of engineered nanomaterials for future nuclear energy applications. In this paper, the recent progress in research and benefits of using nanomaterials in different areas of nuclear energy like nuclear fuel extraction and fabrication, fission product capturing, creating robust reactor materials, radiation sensing and monitoring, and radioactive waste separation and spent nuclear fuel reprocessing are summarized. Ongoing research around the world in this field is reviewed, including experimental and computational methods.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Healable Coatings as a Mechanism to Repair Leading Edge Erosion in Wind Energy

Wind turbine blades are highly engineered structures designed to face temperature extremes and high winds. However, erosion of the blade's leading edge and subsequent repair remains a significant and costly challenge for the wind energy industry. Repair of these leading edges can lead to large amounts of downtime for the turbine and significant operational inefficiencies. In this work, the strength of adhesion and healing ability of a commercially available vitrimer (Mallinda's VITRIMAX) was compared to that of a thermoplastic resin, which has previously been demonstrated in wind energy applications (Arkema's Elium) to evaluate their efficacy as surface coatings for wind turbine blades, particularly their leading edges. Vitrimers are a class of inherently reprocessable thermosets, and it was theorized that vitrimer-based leading edge coatings could enable more robust and efficient wind turbine blades with decreased operational downtime and safer maintenance practices. It was found that the VITRIMAX adhered better to the wind blades' surfaces than both the manufacturer's paint and Elium, with increases in pull-off strength of adhesion ranging from 24% to 83% above that of the original paint. Furthermore, the VITRIMAX adhered strongly to the underlying composite of each blade with strength of adhesion values increasing in ranges from 42% to 97% above that of the original paint. Finally, the vitrimer coating showed an 88% decrease in surface roughness compared to end-of-life blade materials, and initial healing demonstrations in which coatings were manually scratched and subsequently healed exhibited an ~84.5% decrease in scratch depths.

Hubbard, Amber [ORNL]↗
DOE OSTI2024

Effects of moisture and aging upon decomposition of methyl iodide by reduced silver mordenite

Abstract Reduced silver mordenite has been considered as a sorbent for the capture of organic iodides, especially methyl iodide, from off-gases produced by aqueous used nuclear fuel reprocessing operations. The adsorption capacity of this material has been unpredictable especially when NO x and water are present. Previous work has found that a catalytic decomposition reaction is occurring on the surface but few determinations have been made of the kinetics of this reaction. The work presented tested the adsorption behavior and apparent catalytic reaction rate in humid conditions and compared those to dry conditions testing. Both experiments observed a first order reaction with rate constants of 0.0847 L/g sorbent/s and 0.1202 L/g sorbent/s respectively. Such a reduction in apparent rate constant is possibly due to either water obstructing methyl iodide adsorption or product desorption limitation. Changes in the adsorption profile were also apparent between these two, with the humid conditions experiment reaching saturation sooner than the dry conditions experiment. Additionally, an experiment into the effects of sorbent storage in a controlled laboratory environment was performed. The performance of the sorbent materials that were stored with silver in the zerovalent state was slightly inferior to those materials that were stored in ionic form (Ag + ) and reduced to zerovalent silver immediately prior to subjecting them to sorption test. The materials stored with silver in the ionic form (and reduced just prior to application) behaved essentially similarly to the freshly synthesized (and reduced) sorbents in the sorption tests. This suggests that zerovalent silver experiences some oxidation resulting in deactivation of some sites.

Goettsche, Heinrik↗
DOE OSTI2018

Properties and Applications of Distillate Fractions from Highly Stable Dispersions of Liquid Pyrolysis Products

Modern reprocessing and recycling methods for liquid pyrolysis products from hydrocarbon feedstock are analyzed. Hydrocarbon fractions produced during distillation of highly stable dispersions of liquid pyrolysis products from a broad fraction of light hydrocarbons and an ethane fraction are studied. The main physicochemical parameters and fractional and component compositions of the obtained distillates are determined. The products are analyzed for compliance with requirements for grade E-1 and E-18 liquid pyrolysis products. The obtained hydrocarbon distillates were found to meet requirements of TU 2451-179-00203335-2008 for grade E-1 liquid pyrolysis products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effects of Aging and Different Mechanical Recycling Processes on the Structure and Properties of Poly(lactic acid)-clay Nanocomposites

The growing use of poly(lactic acid) (PLA) and PLA-based nanocomposites in packaging has raised the interest of studying the mechanical recycling of the wastes and the properties of the recycled materials. The main objective of this work was to study the effect of two different mechanical recycling processes on the structure and properties of a PLA-montmorillonite nanocomposite. The two recycling processes included accelerated thermal and photochemical aging steps to simulate the degradation experienced by post-consumer plastics during their service life. One of them also included a demanding washing process prior to the reprocessing. A decrease in the molecular weight of PLA was observed in the recycled materials, especially in those subjected to the washing step, which explained the small decrease in microhardness and the increased water uptake at long immersion times. Water absorption at short immersion times was similar in virgin and recycled materials and was accurately described using a Fickian model. The recycled materials showed increased thermal, optical and gas barrier properties due to the improved clay dispersion that was observed by XRD and TEM analysis. The results suggest that recycled PLA-clay nanocomposites can be used in demanding applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Cryogenic gamma detectors enable direct detection of 236 U and minor actinides for non-destructive assay [Cryogenic gamma detectors enable direct detection of minor actinides for non-destructive assay]

Here, we demonstrate the utility of a superconducting transition edge sensor (TES) γ-ray detector with high energy resolution and low Compton background for non-destructive assay (NDA) of a uranium sample from reprocessed nuclear fuel. We show that TES γ-detectors can separate low energy actinide γ-emissions from the background and nearby lines, even from minor isotopes whose signals are often obscured in NDA with conventional Ge detectors. Superconducting γ detectors may therefore bridge the gap between high-accuracy destructive assay (DA) and easier to-use NDA.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗