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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Circular Economy Contributions to Decarbonizing the US Steel Sector

The potential benefits of the circular economy (CE) for decarbonization have recently attracted much attention in the academic and grey literature. The department of energy (DOE) industrial decarbonization roadmap highlight that in addition to the four pillars (energy efficiency, electrification, low-carbon fuels, feedstocks, and energy sources, and carbon capture, utilization, and storage (CCUS)) identified in the roadmap, "scenarios [...] will need to be developed that incorporate materials efficiency and circular economy strategies". Moreover, the roadmap identifies hard-to-abate CO2 emissions across the five industrial subsectors included in the analysis (iron & steel, chemical, food & beverage, refining, and cement manufacturing). Thus, additional options to decarbonize the industrial sector, like the CE, could prove beneficial to address those hard-to-abate emissions. Moreover, they may be less costly, require less R&D or incentives, and be more readily adopted than other strategies such as energy efficiency and CCUS. While the Industrial Decarbonization Roadmap includes some CE strategies (e.g., the increasing market share of steel from electric arc furnaces - which incorporate steel scrap), a deeper dive into what role the CE could play in the United States (US) industrial decarbonization is needed. In this work, we present several industrial decarbonization scenarios that incorporate materials efficiency and circular economy strategies for the iron & steel subsector. The scenarios identify barriers (including technical limits and constraints), opportunities, and R&D needs.Moreover, we estimate the contribution of those scenarios to reducing the industrial sector's CO2 emissions and their potential synergies with the Industrial Decarbonization Roadmap's four pillars. Iron & steel manufacturing was responsible for 90 million tons of industrial CO2 emissions in 2020 - 7% of the industrial sector's total process- related emissions. Besides recycling - which presents technical limitations due to trace contaminants - CE strategies on the demand side could lower iron & steel manufacturing emissions (e.g., the development of lighter products or business models that encourage a more intensive use). This study reviews barriers, opportunities, and trade-offs for 5 material efficiency strategies. Many topics explored in the review call for further research.

barriers↗
DOE OSTI2020

Enabling Stable High‐Voltage LiCoO 2 Operation by Using Synergetic Interfacial Modification Strategy

Abstract Structural and interfacial instability of the LiCoO 2 cathode under a voltage exceeding 4.5 V (vs Li/Li + ) severely hinders its practical applications for high‐energy‐density lithium batteries. Herein, a modified electrolyte with nitriles (suberonitrile or 1,3,6‐hexanetricarbonitrile) and fluoroethylene carbonate (FEC) coadditives is demonstrated to form an ultrathin and uniform interface layer on LiCoO 2 cathode under a synergetic effect. As such, LiCoO 2 /Li cells display excellent cyclability at a cutoff voltage of 4.6 V with a capacity retention over 72% after 300 cycles and 60% after 200 cycles at 30 and 55 °C, respectively, even achieving operation at a high current rate (10 C) upon 500 cycles as compared to the controls with fast‐falling capacity to zero. Furthermore, an adsorption‐coordination mechanism between nitriles and cobalt and synergetic effect of coadditives are explored by the alliance of spectroscopic analysis and theoretical calculations. The contributed lone‐pairs on the N 2p orbital of nitriles in coordination lowers the real oxidation state of Co 3+/4+ so that it decreases its catalysis on electrolytes, and the synergy from nitrile‐derived species regulates FEC to form an LiF‐containing electron‐insulated interface layer. This work shares a new insight to nitriles with the synergy of coadditives and paves a way to refine (ultra)high‐voltage LiCoO 2 cathode for high‐energy‐density energy storages.

Yang, Xuerui↗
DOE OSTI2023

Structural Explanation of the Dielectric Enhancement of Barium Titanate Nanoparticles Grown under Hydrothermal Conditions

Abstract When synthesized under certain conditions, barium titanate (BaTiO 3 , BTO) nanoparticles are found to have the non‐thermodynamic cubic structure at room temperature. These particles also have a several‐fold enhanced dielectric constant, sometimes exceeding 6000, and are widely used in thin‐layer capacitors. A hydrothermal approach is used to synthesize BTO nanocrystals, which are characterized by a range of methods, including X‐ray Rietveld refinement and the Williamson–Hall approach, revealing the presence of significant inhomogeneous strain associated with the cubic phase. However, X‐ray pair distribution function measurements clearly show the local structure is lower symmetry than cubic. This apparent inconsistency is resolved by examining 3D Bragg coherent diffraction images of selected nanocrystals, which show the existence of ≈50 nm‐sized domains, which are interpreted as tetragonal twins, and yet cause the average crystalline structure to appear cubic. The ability of these twin boundaries to migrate under the influence of electric fields explains the dielectric anomaly for the nanocrystalline phase.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Stabilization of the Polar Structure and Giant Second-Order Nonlinear Response of Single Crystal γ-NaAs 0.95 Sb 0.05 Se 2

The dearth of suitable materials significantly restricts the practical development of infrared (IR) laser systems with highly efficient and broadband tuning. Recently, γ-NaAsSe 2 is reported, and it exhibits a large nonlinear second-harmonic generation (SHG) coefficient of 590 pm V —1 at 2 µm. However, the crystal growth of γ-NaAsSe 2 is challenging because it undergoes a phase transition to centrosymmetric δ-NaAsSe 2 . Herein, the stabilization of non-centrosymmetric γ-NaAsSe 2 by doping the As site with Sb, which results in γ-NaAs 0.95 Sb 0.05 Se 2 is reported. The congruent melting behavior is confirmed by differential thermal analysis with a melting temperature of 450 °C and crystallization temperature of 415 °C. Single crystals with dimensions of 3 mm × 2 mm are successfully obtained via zone refining and the Bridgman method. The purification of the material plays a significant role in crystal growth and results in a bandgap of 1.78 eV and thermal conductivity of 0.79 Wm —1 K —1 . The single-crystal SHG coefficient of γ-NaAs 0.95 Sb 0.05 Se 2 exhibits an enormous value of |d 11 | = 648 ± 74 pm V —1 , which is comparable to that of γ-NaAsSe 2 and ≈20× larger than that of AgGaSe 2 . Importantly, the bandgap of γ-NaAs 0.95 Sb 0.05 Se 2 (1.78 eV) is similar to that of AgGaSe 2 , thus rendering it highly attractive as a high-performing nonlinear optical material.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Turning Normal to Abnormal: Reversing CO 2 /C2–Hydrocarbon Selectivity in HKUST–1

Metal–organic frameworks (MOFs) can efficiently purify hydrocarbons from CO 2 , but their rapid saturation, driven by preferential hydrocarbon adsorption, requires energy-intensive adsorption–desorption processes. To address these challenges, an innovative approach is developed, enabling control over MOF flexibility through densification and defect engineering, resulting in an intriguing inverse CO 2 /C2 hydrocarbon selectivity. Here, in this study, the densification process induces the shearing of the crystal lattice and contraction of pores in a defective CuBTC MOF. These changes have led to a remarkable transformation in selectivity, where the originally hydrocarbon-selective CuBTC MOF becomes CO 2 -selective. The selectivity values for densified CuBTC are significantly reversed when compared to its powder form, with notable improvements observed in CO 2 /C 2 H 6 (4416 vs 0.61), CO 2 /C 2 H 4 (15 vs 0.28), and CO 2 /C 2 H 2 (4 vs 0.2). The densified material shows impressive separation, regeneration, and recyclability during dynamic breakthrough experiments with complex quinary gas mixtures. Simulation studies indicate faster CO 2 passage through the tetragonal structure of densified CuBTC compared to C 2 H 2 . Experimental kinetic diffusion studies confirm accelerated CO 2 diffusion over hydrocarbons in the densified MOF, attributed to its small pore window and minimal interparticle voids. This research introduces a promising strategy for refining existing and future MOF materials, enhancing their separation performance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tunable Solid‐State Properties and Anisotropic Charge Mobility in Hydrogen‐Bonded Diketopyrrolopyrrole Polymers via Automated Device Fabrication and Characterization

The optoelectronic properties of semiconducting polymers and device performance rely on a delicate interplay of design and processing conditions. However, screening and optimizing the relationships between these parameters for reliably fabricating organic electronics can be an arduous task requiring significant time and resources. To overcome this challenge, Polybot is developed—a robotic platform within a self‐driving lab that can efficiently produce organic field‐effect transistors (OFETs) from various semiconducting polymers via high‐throughput blade coating deposition. Polybot not only handles the fabrication process but also can conduct characterization tests on the devices and autonomously analyze the data gathered, thus facilitating the rapid acquisition of data on a large scale. This work leverages the capabilities of this platform to investigate the fabrication of OFETs using hydrogen bonding‐containing semiconducting polymers. Through high‐throughput fabrication and characterization, various data trends are analyzed, and large extents of anisotropic charge mobility are observed in devices. The materials are thoroughly characterized to understand the role of processing conditions in solid state and electronic properties of these organic semiconductors. The findings demonstrate the effectiveness of automated fabrication and characterization platforms in uncovering novel structure–property relationships, facilitating refinement of rational chemical design, and processing conditions, ultimately leading to new semiconducting materials.

automated fabrication and characterization↗
DOE OSTI2024

Efficient and Photostable Organic Solar Cells Achieved by Alloyed Dimer Acceptors with Tailored Linker Structures

Abstract High power conversion efficiency (PCE) and long‐term stability are prerequisites for commercialization of organic solar cells (OSCs). Herein, two dimer acceptors (DYTVT and DYTCVT) are developed with different properties through linker engineering, and study their effects as alloy‐like acceptors on the photovoltaic performance and photostability of OSCs. These ternary OSCs effectively combine the advantages of both dimer acceptors. DYTVT, characterized by its high backbone planarity, ensures elevated electron mobility and high glass‐transition temperature (T g ), leading to efficient charge transport and enhanced photostability of OSCs. Conversely, DYTCVT, with its significant dipole moment and electrostatic potential, enhances compatibility of the alloy acceptors with donors and refines the blend morphology, facilitating efficient charge generation in OSCs. Consequently, D18:DYTVT:DYTCVT OSCs exhibit higher PCE (18.4%) compared to D18:MYT (monomer acceptor, PCE = 16.5%), D18:DYTVT (PCE = 17.4%), and D18:DYTCVT (PCE = 17.0%) OSCs. Furthermore, owing to higherT g of alloy acceptors (133 °C) than MYT (T g = 80 °C) and DYTCVT (T g = 120 °C), D18:DYTVT:DYTCVT OSCs have significantly higher photostability (t 80% lifetime = 4250 h under 1‐sun illumination) compared to D18:MYT (t 80% lifetime = 40 h) and D18:DYTCVT OSCs (t 80% lifetime = 2910 h).

Chemistry↗
DOE OSTI2021

Single‐Domain Multiferroic Array‐Addressable Terfenol‐D (SMArT) Micromagnets for Programmable Single‐Cell Capture and Release

Abstract Programming magnetic fields with microscale control can enable automation at the scale of single cells ≈10 µm. Most magnetic materials provide a consistent magnetic field over time but the direction or field strength at the microscale is not easily modulated. However, magnetostrictive materials, when coupled with ferroelectric material (i.e., strain‐mediated multiferroics), can undergo magnetization reorientation due to voltage‐induced strain, promising refined control of magnetization at the micrometer‐scale. This work demonstrates the largest single‐domain microstructures (20 µm) of Terfenol‐D (Tb 0.3 Dy 0.7 Fe 1.92 ), a material that has the highest magnetostrictive strain of any known soft magnetoelastic material. These Terfenol‐D microstructures enable controlled localization of magnetic beads with sub‐micrometer precision. Magnetically labeled cells are captured by the field gradients generated from the single‐domain microstructures without an external magnetic field. The magnetic state on these microstructures is switched through voltage‐induced strain, as a result of the strain‐mediated converse magnetoelectric effect, to release individual cells using a multiferroic approach. These electronically addressable micromagnets pave the way for parallelized multiferroics‐based single‐cell sorting under digital control for biotechnology applications.

Khojah, Reem↗
DOE OSTI2022

Hypothesis Learning in Automated Experiment: Application to Combinatorial Materials Libraries

Machine learning is rapidly becoming an integral part of experimental physical discovery via automated and high-throughput synthesis, and active experiments in scattering and electron/probe microscopy. This, in turn, necessitates the development of active learning methods capable of exploring relevant parameter spaces with the smallest number of steps. In this work, an active learning approach based on conavigation of the hypothesis and experimental spaces is introduced. This is realized by combining the structured Gaussian processes containing probabilistic models of the possible system's behaviors (hypotheses) with reinforcement learning policy refinement (discovery). This approach closely resembles classical human-driven physical discovery, when several alternative hypotheses realized via models with adjustable parameters are tested during an experiment. This approach is demonstrated for exploring concentration-induced phase transitions in combinatorial libraries of Sm-doped BiFeO 3 using piezoresponse force microscopy, but it is straightforward to extend it to higher-dimensional parameter spaces and more complex physical problems once the experimental workflow and hypothesis generation are available.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Optically Excited Lasing in a Cavity‐Based, High‐Current‐Density Quantum Dot Electroluminescent Device

Abstract Laser diodes based on solution‐processable materials can benefit numerous technologies including integrated electronics and photonics, telecommunications, and medical diagnostics. An attractive system for implementing these devices is colloidal semiconductor quantum dots (QDs). The progress towards a QD laser diode has been hampered by rapid nonradiative Auger decay of optical‐gain‐active multicarrier states, fast device degradation at high current densities required for laser action, and unfavorable competition between optical gain and optical losses in a multicomponent device stack. Here we resolve some of these challenges and demonstrate optically excited lasing from fully functional high‐current density electroluminescent (EL) devices with an integrated optical resonator. This advance has become possible due to excellent optical gain properties of continuously graded QDs and a refined device architecture, which allows for highly efficient light amplification in a thin, EL‐active QD layer.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The Synthescope: A Vision for Combining Synthesis with Atomic Fabrication

Here, the scanning transmission electron microscope, a workhorse instrument in materials characterization, is being transformed into an atomic-scale material-manipulation platform. With an eye on the trajectory of recent developments and the obstacles toward progress in this field, a vision for a path toward an expanded set of capabilities and applications is provided. The microscope is reconceptualized as an instrument for fabrication and synthesis with the capability to image and characterize atomic-scale structural formation as it occurs. Further development and refinement of this approach may have substantial impact on research in microelectronics, quantum information science, and catalysis, where precise control over atomic-scale structure and chemistry of a few “active sites” can have a dramatic impact on larger-scale functionality and where developing a better understanding of atomic-scale processes can help point the way to larger-scale synthesis approaches.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Synthesis of Ultra‐Incompressible and Recoverable Carbon Nitrides Featuring CN 4 Tetrahedra

Abstract Carbon nitrides featuring three‐dimensional frameworks of CN 4 tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high‐pressure high‐temperature synthesis of three carbon–nitrogen compounds,tI14‐C 3 N 4 ,hP126‐C 3 N 4 , andtI24‐CN 2 , in laser‐heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single‐crystal X‐ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra‐incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high‐pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions.

Chemistry↗
DOE OSTI2024

Strong‐Yet‐Ductile Eutectic Alloys Employing Cocoon‐Like Nanometer‐Sized Dislocation Cells

Abstract Eutectic alloys (EAs) with superior fluidity are known to be the easiest to cast into high‐quality ingots, making them the alloys of choice for making large‐sized structural parts. However, conventional EAs (CEAs) have never reached strength–ductility combinations on par with the best in other alloy categories. Via thermomechanical processing of cast Ni‐32.88wt%Fe‐9.53wt%Al CEAs, a cocoon‐like nano‐meshed (as fine as 26 nm) network of dislocations (CNN‐D) is produced via recovery annealing, through the rearrangement of cold‐work‐accumulated dislocations anchored by dense pre‐existing nanoprecipitates. In lieu of traditional plasticity mechanisms, such as TWIP and TRIP, the CNN‐D is particularly effective in eutectic lamellae with alternating phases, as it instigates nanometer‐spaced planar slip bands that not only dynamically refine the microstructure but also transmit from the FCC (face‐centered‐cubic) layers into the otherwise brittle B2 layers. These additional mechanisms for strengthening and strain hardening sustain stable tensile flow, resulting in a striking elevation of both strength and ductility to outrank not only all previous CEAs, but also the state of the art—additively manufactured eutectic high‐entropy alloys. The CNN‐D thus adds a novel microstructural strategy for performance enhancement, especially for compositionally complex alloys that increasingly make use of nanoprecipitates or local chemical order.

Chemistry↗
DOE OSTI2024

ASb 3 Mn 9 O 19 (A = K or Rb): New Mn-Based 2D Magnetoplumbites with Geometric and Magnetic Frustration

Magnetoplumbites are one of the most broadly studied families of hexagonal ferrites, typically with high magnetic ordering temperatures, making them excellent candidates for permanent magnets. However, magnetic frustration is rarely observed in magnetoplumbites. Herein, the discovery, synthesis, and characterization of the first Mn-based magnetoplumbite, as well as the first magnetoplumbite involving pnictogens (Sb), ASb 3 Mn 9 O 19 (A = K or Rb) are reported. The Mn 3+ ( S = 2) cations, further confirmed by DC magnetic susceptibility and X-ray photoelectron spectroscopy, construct three geometrically frustrated sublattices, including Kagome, triangular, and puckered honeycomb lattices. Magnetic properties measurements revealed strong antiferromagnetic spin–spin coupling as well as multiple low-temperature magnetic features. Heat capacity data does not show any prominent λ-anomaly, suggesting minimal associated magnetic entropy. Moreover, neutron powder diffraction (NPD) implied the absence of long-range magnetic ordering in KSb 3 Mn 9 O 19 down to 3 K. However, several magnetic peaks are observed in RbSb 3 Mn 9 O 19 at 3 K, corresponding to an incommensurate magnetic structure. Interestingly, strong diffuse scattering is seen in the NPD patterns of both compounds at low angles and is analyzed by reverse Monte Carlo refinements, indicating short-range spin ordering related to frustrated magnetism as well as 2D magnetic correlations in ASb 3 Mn 9 O 19 (A = K or Rb).

2-D magnetic correlation↗
DOE OSTI2026

Adsorption-Engineered Hydrocarbon Ionomers for Durable Proton-Exchange Membrane Fuel Cells

Reducing reliance on perfluoroalkyl substances (PFAS) in proton-exchange membrane fuel cells requires hydrocarbon ionomers that combine high performance with long-term durability, a persistent challenge in catalyst-layer design. Here, we identify oxidation-driven ionomer-catalyst interfacial degradation as a dominant failure pathway in hydrocarbon ionomer-bonded cathodes and introduce an adsorption-engineering strategy to overcome this limitation. The comparison of a commercial sulfonated poly(phenylene) (Pemion) with structurally engineered sulfonated poly(fluorene)s demonstrated that electrode durability is governed by the interplay between ionomer adsorption strength and resistance to oxidative degradation on carbon-supported Pt catalysts. A poly(fluorene) ionomer with mobile alkyl sulfonic acid groups forms resilient interfaces, delivering 1.28 A cm−2 at 0.65 V under fully humidified H2/air conditions (80°C and 150 kPaabs), comparable to Pemion. After 90,000 accelerated potential cycles, the poly(fluorene)-bonded cathode exhibits significantly improved durability, with only 29% performance loss compared to 58% for Pemion; further molecular refinement reduces the loss to 17%, approaching that of Nafion-bonded cathodes (14%). These findings establish adsorption-engineered ionomer design that decouples interfacial anchoring from oxidative degradation as a general strategy for achieving durable, high-performance PFAS-free PEM fuel cell electrodes.

08 HYDROGEN↗
DOE OSTI2024

Your Clean Graphene is Still Not Clean

Researchers working with thin samples, such as monolayer graphene, are consistently struggling against contamination. Indeed, the problem of hydrocarbon contamination is known from the earliest days of electron microscopy and efforts to reduce this problem are ubiquitous to almost all high-vacuum experiments. Accurate knowledge of the behavior of such contamination is essential for electron beam (e-beam) based atomic fabrication, where it is aspired to select and control matter on an atom-by-atom basis. Here, the vexing question of hydrocarbon contamination on graphene is taken up. Image intensity is used to directly reveal the presence of diffusing hydrocarbons on ostensibly clean graphene. These diffusing hydrocarbons are previously inferred but not directly observed. Surprising dynamic variations of the concentration of these hydrocarbons impels questions about their origin. Here, some possible explanations are presented and some tentative conclusions are drawn. This work updates the conceptual model of “clean graphene” and offers refinements to the description of e-beam induced hydrocarbon deposition.

atomic fabrication↗
DOE OSTI2023

Measuring the Exciton Binding Energy: Learning from a Decade of Measurements on Halide Perovskites and Transition Metal Dichalcogenides

The exciton binding energy ( E b ) is a key parameter that governs the physics of many optoelectronic devices. At their best, trustworthy and precise measurements of E b challenge theoreticians to refine models, are a driving force in advancing the understanding of a material system, and lead to efficient device design. At their worst, inaccurate E b measurements lead theoreticians astray, sow confusion within the research community, and hinder device improvements by leading to poor designs. Here, this review article seeks to highlight the pros and cons of different measurement techniques used to determine E b , namely, temperature‐dependent photoluminescence, resolving Rydberg states, electroabsorption, magnetoabsorption, scanning tunneling spectroscopy, and fitting the optical absorption. Due to numerous conflicting E b values reported for halide perovskites (HP) and transition metal dichalcogenides (TMDC) monolayers, an emphasis is placed on highlighting these measurements in an attempt to reconcile the variance between different measurement techniques. It is argued that the experiments with the clearest indicators are in agreement on the following values: ≈350–450 meV for TMDC monolayers between SiO 2 and vacuum, ≈150–200 meV for hBN‐encapsulated TMDC monolayers, ≈200–300 meV for common lead‐iodide 2D HPs, and ≈10 meV for methylammonium lead iodide.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synergy of Liquid-Crystalline Small-Molecule and Polymeric Donors Delivers Uncommon Morphology Evolution and 16.6% Efficiency Organic Photovoltaics

Achieving an ideal morphology is an imperative avenue for enhancing key parameters toward high-performing organic solar cells (OSCs). Among a myriad of morphological-control methods, the strategy of incorporating a third component with structural similarity and crystallinity difference to construct ternary OSCs has emerged as an effective approach to regulate morphology. A nematic liquid-crystalline benzodithiophene terthiophene rhodamine (BTR) molecule, which possesses the same alkylthio-thienyl-substituted benzo moiety but obviously stronger crystallinity compared to classical medium-bandgap polymeric donor PM6, is employed as a third component to construct ternary OSCs based on a PM6:BTR:Y6 system. The doping of BTR (5 wt%) is found to be enough to improve the OSC morphology—significantly enhancing the crystallinity of the photoactive layer while slightly reducing the donor/acceptor phase separation scale simultaneously. Rarely is such a morphology evolution reported. It positively affects the electronic properties of the device—prolongs the carrier lifetime, shortens the photocurrent decay time, facilitates exciton dissociation, charge transport, and collection, and ultimately boosts the power conversion efficiency from 15.7% to 16.6%. This result demonstrates that the successful synergy of liquid-crystalline small-molecule and polymeric donors delicately adjusts the active-layer morphology and refines device performance, which brings vibrancy to the OSC research field.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗