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At least 1,009 records · Page 56

Giant anisotropic in-plane thermal conduction induced by Anomalous phonons in pentagonal PdSe 2

In two-dimensional materials, different atomic stacking induces anisotropic atomic interactions and phonon dispersions, leading to the anisotropy of in-plane thermal transport. In this work, we report an exceptional case in layered pentagonal PdSe 2 , where the bonding, force constants, and lattice constants are nearly-equal along the in-plane crystallographic axis directions, while the thermal conductivity is surprisingly much greater along b-axis than along a-axis with a ratio up to 1.8. Such strong anisotropy is not only unexpected in in-plane uniform structured materials, but also 2 comparable to the record high in-plane anisotropic thermal conductivity in the nonuniform structured material reported to date (the ratio is ~2.0 in TiS 3 ). By combining the inelastic X-ray scattering measurement and the first-principles calculations, we attribute such high anisotropy to the low-energy phonons along a-axis, particularly their lower group velocities and “avoided-crossing” behavior. The different buckling structures between a- (zigzag-type) and b-axis (flat-type) are mainly responsible for such unique phonon dynamics properties of PdSe 2 . This finding helps to discover materials with high anisotropic in-plane thermal conductivity in uniform structures and reveals new physics of anisotropy of in-plane thermal conduction. Due to the unique features in structure and thermal transport properties, PdSe 2 may serve as a new platform for designing novel devices to route heat flow precisely at the nanoscale.

36 MATERIALS SCIENCE↗

Electro-optic transduction in silicon via gigahertz-frequency nanomechanics

Interfacing electronics with optical fiber networks is key to the long-distance transfer of classical and quantum information. Piezo-optomechanical transducers enable such interfaces by using gigahertz-frequency acoustic vibrations as mediators for converting microwave photons to optical photons via the combination of optomechanical and piezoelectric interactions. However, despite successful demonstrations, efficient quantum transduction remains out of reach due to the challenges associated with hybrid material integration and increased loss from piezoelectric materials when operating in the quantum regime. Here, we demonstrate an alternative approach in which we actuate 5-GHz phonons in a conventional silicon-on-insulator platform. In our experiment, microwave photons resonantly drive a phononic crystal oscillator via the electrostatic force realized in a charge-biased narrow-gap capacitor. The mechanical vibrations are subsequently transferred via a phonon waveguide to an optomechanical cavity, where they transform into optical photons in the sideband of a pump laser field. Operating at room temperature and atmospheric pressure, we measure a microwave-to-optical photon conversion efficiency of 1.72±0.14×10 −7 in a 3.3 MHz bandwidth. Our results mark a stepping stone towards quantum transduction with integrated devices made from crystalline silicon, which promise efficient high-bandwidth operation and integration with superconducting qubits. Additionally, the lack of need for piezoelectricity or other intrinsic nonlinearities makes our approach applicable to a wide range of materials for potential applications beyond quantum technologies.

42 ENGINEERING↗

Enhancing Risk Analysis of Accidental Release Using CFD Modeling and Machine Learning

This project report presents the results from the AU31 project that is entitled “Enhancing Risk Analysis of Accidental Release Using CFD Modeling and Machine Learning” performed between FY2021 and FY2022. The technical objective of this project is to enhance risk analysis of accidental release of radioactive materials and provide novel risk forecasting and capabilities for assessing unplanned hazardous chemical releases for the U.S. Department of Energy (DOE). The approach includes a cross-platform finite element analysis of airborne chemical release, machine learning (ML) for simulation and forecasting, and a big data approach to data management, transformation and analysis capable of handling petabyte-scale unstructured and structured data. The outcome of these findings were assembled and accessible as a final output via an intuitive web hosted geospatial-based user interface for demonstration and general dissemination. These new results also provide a mechanism of combining this knowledge in a risk analysis framework tool. The geospatial analysis and output can utilize 5 years of qualified meteorological data to illustrate projected plume footprints that are generated from computational aspects of this study. Specifically, we show the development of a geospatial risk analysis capabilities to respond to and plan for accidental release of radioactive materials and to provide a risk forecasting tool for assessing hazardous chemical releases for the DOE. The focus of this effort is germane to common practices in risk analysis; and it is highly relevant to the timely and transparent release of information related to materials at risk including hazardous materials and chemical vapors and rapid assessment of the potential impacts on the workforce at active sites across the DOE complex.

42 ENGINEERING↗

Electrical Control of Spin and Valley in Spin-Orbit Coupled Graphene Multilayers

Electrical control of magnetism has been a major technological pursuit of the spintronics community, owing to its far-reaching implications for data storage and transmission. Here, in this study, we propose and analyze a new mechanism for electrical switching of isospin, using chiral-stacked graphene multilayers, such as Bernal bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced spin-orbit coupling from the TMD, we demonstrate electrical switching of correlation-induced spin and/or valley polarization, by reversing a perpendicular displacement field or the chemical potential. We substantiate our proposal with both analytical arguments and self-consistent Hartree-Fock numerics. Finally, we illustrate how the relative alignment of the TMDs, together with the top and bottom gate voltages, can be used to selectively switch distinct isospin flavors, putting forward correlated Van der Waals heterostructures as a promising platform for spintronics and valleytronics.

36 MATERIALS SCIENCE↗

Performance Testing of Software Upgrade for SRNL CPC Instrument at the Nuclear Material Laboratory, Office of Safeguards Analytical Services, International Atomic Energy Agency

This report summarizes the performance testing for the Software upgrade for the Savannah River National Laboratory (SRNL) Controlled Potential Coulometry (CPC) instrument. This upgrade is specifically to meet the needs of the Nuclear Material Laboratory, Office of Safeguards Analytical Services, International Atomic Energy Agency at Seibersdorf, Austria. The instrument hardware was upgraded in 2010, but the software continued to operate on a Windows platform using a High Tech Basic (HT Basic) application. HT Basic usage is declining. The IAEA requested an upgrade to the existing coulometer software to Laboratory Virtual Instrument Engineering Workbench (LabVIEW), an object-oriented programming language in wide use and one the NML staff is familiar with. The software was developed by SRNL Software Engineer, with assistance from Electrical Engineer and Scientist. Once developed, the new LabVIEW software was validated, tested with Iron (surrogate for plutonium) and plutonium. Once testing was completed, the software was installed at the International Atomic Energy Agency Nuclear Material Laboratory (IAEA NML) coulometer, and SRNL provided hands on training to NML staff on using the new software.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Advanced Algal Biofoundries for the Production of Polyurethane Precursors

The primary goal of the BEEPs project was to develop a process that could accelerate the development of algae as bioproduction platforms, from initial chemical product concept to an economically viable market supply. Under this program we elected to develop strains of algae that could generate polyurethane precursors, while simultaneously developing basic genetic tools to enable improved algal production systems. This program was specifically designed to incorporate National Laboratories as a means to utilize the expertise and facilities for new bio-production platforms. To that end, we designed a program to collaborate with the Agile BioFoundry at Lawrence Berkeley National Laboratory (LBNL) and computational platforms at Pacific Northwest National Laboratory (PNNL). In addition to these National Laboratory partners, we also had academic partners from UC Davis and Georgia Tech, as well as commercial partners Algenesis Materials and BASF. To achieve these goals, we initially focused on developing the genetic tools and high throughput screening technologies necessary to generate and assess production of polymer precursors (succinic acid) in algae and cyanobacteria, including advanced promoters and biosensors. In parallel, we computationally identified potential production bottlenecks and then used the developed genetic tools to increase production rates and yields. Constant feedback of data was used in conjunction with machine learning, high-throughput cell sorting, and synthetic biology, for additional targeted metabolic engineering. Multiple rounds of tool design, building, testing, and learning were supplied to partners at PNNL and LBNL to develop new models and tools that could expedite bioproduction platform development and increase yield performance. We targeted, and achieved, the FOA requirement yield metric of 20 g/L, as a milestone and deliverable from at least one of our engineered strains for the production of succinic acid.

09 BIOMASS FUELS↗

Single photon emitters in van der Waals solids for quantum photonics: materials, theory and molecular-scale characterization probes

Strong light–matter interactions in two-dimensional layered materials (2D materials) have attracted the interest of researchers from interdisciplinary fields for more than a decade now. A unique phenomenon in some 2D materials is their large exciton binding energies (BEs), increasing the likelihood of exciton survival at room temperature. It is this large BE that mediates the intense light–matter interactions of many of the 2D materials, particularly in their monolayer limit, where the interplay of excitonic phenomena poses a wealth of opportunities for high-performance optoelectronics and quantum photonics. Within quantum photonics, quantum information science (QIS) is growing rapidly, where photons are a promising platform for information processing due to their low-noise properties, excellent modal control, and long-distance propagation. A central element for QIS applications is a single photon emitter (SPE) source, where an ideal on-demand SPE emits exactly one photon at a time into a given spatiotemporal mode. Recently, 2D materials have shown practical appeal for QIS which is directly driven from their unique layered crystalline structure. This structural attribute of 2D materials facilitates their integration with optical elements more easily than the SPEs in conventional three-dimensional solid state materials, such as diamond and SiC. In this review article, we will discuss recent advances made with 2D materials towards their use as quantum emitters, where the SPE emission properties maybe modulated deterministically. Here, the use of unique scanning tunneling microscopy tools for the in-situ generation and characterization of defects is presented, along with theoretical first-principles frameworks and machine learning approaches to model the structure-property relationship of exciton–defect interactions within the lattice towards SPEs. Given the rapid progress made in this area, the SPEs in 2D materials are emerging as promising sources of nonclassical light emitters, well-poised to advance quantum photonics in the future.

2D layered materials↗

Plastic Parallel Pathways Platform - 4P Model

Global momentum is building towards a circular economy capable of keeping plastics in use and out of waste streams. Given that 79% of all plastic produced since 1950 has accumulated in landfills or the natural environment,rapid implementation of various end-of-life (EoL) management technologies will be needed to reach this target. However, it can be challenging to develop an effective plastic EoL strategy when the available options - chemical or molecular recycling, energy recovery, upcycling, downcycling, closed-loop (plastic-to-plastic) or open-loop (plastic-to-x) recycling, among others - can generate products ranging from low-grade to virgin-quality plastic and from fuels to value-added chemicals. We present a flexible material flow model capable of analyzing the effects of both plastic-to-plastic and plastic-to-x EoL management strategies on the U.S. PET economy. This Plastic Parallel Pathways Platform (4P) assesses the environmental impacts, costs, and circularity of a PET system in which waste is managed through six potential EoL pathways: landfill, incineration with energy recovery, pyrolysis to fuel oil, upcycling to glass fiber reinforced plastic (GFRP), mechanical recycling to low-grade PET, and chemical recycling (glycolysis) to bottle-grade PET. We compare the pathways across multiple metrics using multi-criteria decision analysis (MCDA) and then use a brute force algorithm to predict an optimal combination of EoL pathways to minimize greenhouse gas (GHG) emissions and costs and maximize circularity. This work highlights the need to implement a diverse portfolio of EoL strategies in parallel to enable a PET economy that meets environmental, economic, and circularity requirements simultaneously.

downcycling↗

Robust Heat-Flux Sensors for Coal-Fired Boiler Extreme Environments

In this project, robust heat-flux measurement systems were developed. The heat-flux sensors utilize thermoelectric effects to directly transduce the heat-flux inputs to analog electrical voltage signals. They were constructed from dedicated materials that can withstand temperatures of at least 1000°C and maintain adequate performance at these conditions for prolonged periods of time. The proposed approaches took into account numerous considerations, including system cost, sensor head resilience, sensor footprint, data accuracy, response time, and maintenance requirements. Through modern thermoelectric materials design, methodical materials selection and rigorous testing in materials characterization labs and medium-scale fire research facilities, we have demonstrated functioning laboratory prototypes, upon which one could base industrial heat-flux sensing platforms capable of operating in the challenging high-temperature, corrosive environments of the boilers of coal-fired power plants. A distributed sensor array for heat-flux measurements throughout the furnace water-wall, the superheater area and the economizer coils can provide critical data for the power plant control systems to increase efficiency, improve safety and reduce down times. For example, the combined heat-flux sensor/control systems can contribute to the optimization of burner and boiler operations under flexible loads, the optimization of heat-exchange conditions and overall reduction of heat rate and emissions, the prediction of imminent overheating conditions, and the optimization of the soot-blowing protocols.

20 FOSSIL-FUELED POWER PLANTS↗

Bridging the length scales in ionic separations via data-driving machine learning

We pursued a data science driven machine learning (ML) approach that blended molecular scale attributes informed from molecular dynamics (MD) simulation and materials properties to the selectivity and energy efficiency in targeted ionic separations using electric fields. The model mixtures investigated for ionic separations are pH sensitive and include organic acids, silica and boron, transition metals, such as copper and chromium. There were two major research thrusts of this project. Firstly, we investigated surrogate models and deep learning that relate material chemistries and structures to selective transport of ionic species under applied electric fields. Secondly we investigated how the bipolar junction interfacial design and water dissociation catalyst in bipolar membranes affect reverse bias polarization behavior and pH modulation in deionization platforms as a function of the platform operating parameters (e.g., cell voltage, residence time, and salt feed concentration). As a result of this work, we also were able to start a new direction, namely ML models for molecular design of surfactants.

36 MATERIALS SCIENCE↗

Surfactant-Induced Interfacial Aggregation of Porphyrins for Structuring Color-Tunable Liquids

Locking nonequilibrium shapes of liquids into targeted architectures by interfacial jamming of nanoparticles is an emerging area in material science. 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (H 6 TPPS) shows three different aggregation states that present an absorption imaging platform to monitor the assembly and jamming of supramolecular polymer surfactants (SPSs) at the liquid/liquid interface. The interfacial interconversion of H 6 TPPS, specifically H 4 TPPS 2- dissolved in water, from J- to an H-aggregation was induced by strong electrostatic interactions with amine-terminated polystyrene dissolved in toluene at the water/toluene interface. We find that this resulted in color-tunable liquids due to interfacial jamming of the SPSs formed between H 4 TPPS 2- and amine-terminated polystyrene. However, the formed SPSs cannot lock in nonequilibrium shapes of liquids. In addition, a self-wrinkling behavior was observed when amphiphilic triblock copolymers of PS-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) were used to interact with H 4 TPPS 2- . Subsequently, the SPSs formed can lock in nonequilibrium shapes of liquids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Magnetic Topological Semimetal Phase with Electronic Correlation Enhancement in SmSbTe

The ZrSiS family of compounds hosts various exotic quantum phenomena due to the presence of both topological nonsymmorphic Dirac fermions and nodal-line fermions. In this material family, the LnSbTe (Ln = lanthanide) compounds are particularly interesting owing to the intrinsic magnetism from magnetic Ln which leads to new properties and quantum states. Here in this work, the authors focus on the previously unexplored compound SmSbTe. The studies reveal a rare combination of a few functional properties in this material, including antiferromagnetism with possible magnetic frustration, electron correlation enhancement, and Dirac nodal-line fermions. These properties enable SmSbTe as a unique platform to explore exotic quantum phenomena and advanced functionalities arising from the interplay between magnetism, topology, and electronic correlations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

3D Nanomagnetism in Low Density Interconnected Nanowire Networks

Free-standing, interconnected metallic nanowire networks with densities as low as 40 mg/cm 3 have been achieved over centimeter-scale areas, using electrodeposition into polycarbonate membranes that have been ion-tracked at multiple angles. Networks of interconnected magnetic nanowires further provide an exciting platform to explore 3-dimensional nanomagnetism, where their structure, topology, and frustration may be used as additional degrees of freedom to tailor the materials properties. New magnetization reversal mechanisms in cobalt networks are captured by the first-order reversal curve method, which demonstrate the evolution from strong demagnetizing dipolar interactions to intersection-mediated domain wall pinning and propagation, and eventually to shape-anisotropy dominated magnetization reversal. These findings open up new possibilities for 3-dimensional integrated magnetic devices for memory, complex computation, and neuromorphics.

36 MATERIALS SCIENCE↗

Dehydrogenated Polyethylene from Discarded Plastics as a Synthon for Functional Polyolefins

Many valuable specialty chemicals and drug candidates rely on synthesizing reactive intermediates to generate the final product(s). An approach that leverages C-H activation chemistry to achieve chemically active reactive handles for polymer diversification is desirable. Further, this report describes the synthesis and functionalization of dehydrogenated high-density polyethylene (HDPE) from discarded post-consumer plastic via acceptorless Ir-pincer-catalyzed non-oxidative dehydrogenation followed by acid-catalyzed hydroamination and hydroalkoxylation. The final products show significant material property changes with tunability and scalability through variation of the olefin content. This method highlights the potential value of dehydrogenated intermediates as platforms to enable carbon circularity and polyolefin end-of-life management strategies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Carbon Dioxide Utilization Life Cycle Analysis Guidance for the U.S. DOE Office of Fossil Energy and Carbon Management (Version 2.0)

Capturing carbon dioxide (CO 2 ) and placing it in permanent storage in geologic formations is an option for reducing CO 2 emissions, but it may not be a viable one for all CO 2 emitters. For some, the added cost of capture may be too high to implement, or the geology near the source may not be suitable for storage. In these circumstances, other options will be needed. Carbon use and reuse, or CO 2 utilization (CO2U), is an alternative approach that seeks beneficial uses for captured CO 2 , such as using it as a feedstock in the production of fuels, chemicals, and building materials. These uses would give CO 2 value that could be used by suppliers (emitters) to offset capture costs. One of the principal features and challenges associated with CO2U is that the products derived from CO 2 must have lower carbon footprints than their conventional counterparts. Previous assessments of CO2U alternatives have focused on the carbon content of utilization products as an indicator of CO 2 equivalent (CO 2 e) emissions reduction potential. However, embodied emissions are—at best—only weakly correlated with the amount of carbon contained in any physical product. Therefore, the most attractive CO2U options will both displace the carbon in an existing product and improve the overall carbon efficiency of the manufacturing process. Research to overcome barriers will include identifying existing co-feeds and available low-carbon energy sources to enable the conversion of CO 2 to value-added products under favorable processing conditions. New discoveries in the fields of nano- and bio-technology will be applied to efficiently utilize CO 2 in new applications. Development of advanced materials and processes, integrating CO 2 capture with utilization processes (e.g., algae), exploring a diverse slate of products from CO 2 to effectively offset capture costs and developing processes based on waste energy are means to overcome these barriers. The research will lead to the development of advanced catalysts, materials, and equipment that can be used to convert CO 2 into useful products. The result will be multiple flexible and adaptable technology platforms that can be used to produce suites of products spanning multiple utilization pathways.

54 ENVIRONMENTAL SCIENCES↗

Luminescent Materials for the Detection of Economically Critical Metals in Harsh Environments

Renewable energy technologies used for electric vehicles and wind turbines are heavily reliant upon metals, such as rare earth elements, cobalt, lithium, and nickel. Indeed, there are 50 minerals that are currently considered “economically critical” by the 2022 United States Geological Survey. With anticipated global adoption of renewable energy technologies, producing sufficient metals to meet this demand presents a significant challenge, particularly due to the current monopolistic market for many of these metals. The production of metals from unconventional sources, such as coal utilization byproducts, is one of many promising strategies to boost domestic supply. However, sensitive, rapid, and inexpensive characterization technologies are needed to minimize production costs associated with metals prospecting and processing. Photoluminescence-based sensing techniques are particularly intriguing due to their potential for low cost and portability, coupled with high sensitivity and selectivity. This presentation focuses on the development of high-performance sensing materials for a range of critical metals, including metal-organic frameworks capable of sensitizing detection of parts-per-billion concentrations of six different rare earth elements, nanoparticles that can detect down to 600 parts-per-billion levels of cobalt, and thin films that sense aluminum down to 120 parts-per-billion. These materials are highly selective, capable of withstanding low pH conditions, and provide a response within minutes. Importantly, each sensing material is integrated with a custom-built, fully portable fiber-optic spectrometer for potential field deployment, providing significant cost savings over commercial instruments, along with potential advantages such as material regeneration for use across multiple sensing cycles and solvent removal for enhanced emission signal. These results highlight the exciting potential of luminescence platforms as cost-effective alternatives for metals characterization.

Crawford, Scott↗

Closed‐Loop Recycling of Poly(pentylene Adipate‐ co ‐Terephthalate) via Amine‐Catalyzed Methanolysis

Advancing circularity through effective chemical recycling strategies is essential for enabling the sustainable use of emerging biodegradable polyesters in film applications. In this context, poly(pentylene adipate-co-terephthalate) with a 40/60 adipate-to-terephthalate ratio (PPeAT60), a significantly stiffer and partially biobased copolyester recently reported by our team, offers improved mechanical performance and processability compared to commercial poly(butylene adipate-co-terephthalate), while providing a platform to evaluate advanced recycling approaches for film applications. Here, this study describes depolymerization of PPeAT60 through amine-catalyzed methanolysis, followed by the repolymerization of the recovered monomers. The resulting repolymerized material exhibited a molar mass distribution, chemical structure, and thermal stability comparable to the virgin polymer, confirming the technical feasibility of the methanolysis-based recycling route. Both polymers displayed nearly identical melting, glass transition, and decomposition temperatures, crystallinity, and modulus, demonstrating full structural and mechanical reproducibility after recycling. Variations in crystallization kinetics, elongation at break, and barrier properties likely arise from trace impurities (<1%) introduced during processing acting as nucleating and stress-inducing agents. Overall, these results demonstrate that PPeAT60 retains its key properties after chemical recycling, establishing methanolysis as a promising platform for recycling of this partially biobased polymer that may be able to replace both conventional polyolefins and PBAT in flexible packaging applications.

09 BIOMASS FUELS↗