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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Spatially Precise Light‐Activated Dedoping in Wafer‐Scale MoS 2 Films

2D materials, particularly transition metal dichalcogenides (TMDCs), have shown great potential for microelectronics and optoelectronics. However, a major challenge in commercializing these materials is the inability to control their doping at a wafer scale with high spatial fidelity. Interface chemistry is used with the underlying substrate oxide and concomitant exposure to visible light in ambient conditions for photo-dedoping wafer scale MoS 2 . It is hypothesized that the oxide layer traps photoexcited holes, leaving behind long-lived electrons that become available for surface reactions with ambient air at sulfur vacancies (defect sites) resulting in dedoping. Additionally, high fidelity spatial control is showcased over the dedoping process, by laser writing, and fine control achieved over the degree of doping by modulating the illumination time and power density. This localized change in MoS 2 doping density is very stable (at least 7 days) and robust to processing conditions like high temperature and vacuum. The scalability and ease of implementation of this approach can address one of the major issues preventing the “Lab to Fab” transition of 2D materials and facilitate its seamless integration for commercial applications in multi-logic devices, inverters, and other optoelectronic devices.

14 SOLAR ENERGY↗
DOE OSTI2022

Molecular Doping Increases the Semitransparent Photovoltaic Performance of Dilute Bulk Heterojunction Film with Discontinuous Polymer Donor Networks

The semitransparent and colorful properties of organic solar cells (OSCs) attract intensive academic interests due to their potential application in building integrated photovoltaics, wearable electronics, and so forth. The most straightforward and effective method to tune these optical properties is varying the componential ratio in the blend film. However, the increase in device transmittance inevitably sacrifices the photovoltaic performance because of severe carrier recombination that originates from discontinuous charge-transport networks in the blend film. In this work, a strategy is proposed via the molecular-doping strategy to overcome these shortcomings. It is discovered that p-doping is able to release the trapped holes in segregated polymer domains leading to short-circuit current enhancement, while n-doping is more effective to fill the bandgap states producing a higher fill factor. More importantly, either type of doping improves the photovoltaic performance in the semitransparent photovoltaic devices. These discoveries provide a new pathway to breaking the compromise between the photovoltaic performance and optical transmittance in semitransparent OSCs, and hold promise for their future commercialization.

14 SOLAR ENERGY↗
DOE OSTI2021

Decomposition of Feynman integrals by multivariate intersection numbers

We present a detailed description of the recent idea for a direct decomposition of Feynman integrals onto a basis of master integrals by projections, as well as a direct derivation of the differential equations satisfied by the master integrals, employing multivariate intersection numbers. We discuss a recursive algorithm for the computation of multivariate intersection numbers, and provide three different approaches for a direct decomposition of Feynman integrals, which we dub the straight decomposition, the bottom-up decomposition, and the top-down decomposition. These algorithms exploit the unitarity structure of Feynman integrals by computing intersection numbers supported on cuts, in various orders, thus showing the synthesis of the intersection-theory concepts with unitarity-based methods and integrand decomposition. We perform explicit computations to exemplify all of these approaches applied to Feynman integrals, paving a way towards potential applications to generic multi-loop integrals.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Sphere and disk partition functions in Liouville and in matrix integrals

We compute the sphere and disk partition functions in semiclassical Liouville and analogous quantities in double-scaled matrix integrals. The quantity sphere/disk2 is unambiguous and we find a precise numerical match between the Liouville answer and the matrix integral answer. An application is to show that the sphere partition function in JT gravity is infinite.

2D Gravity↗
DOE OSTI2019

Nanoscale plasmonic detector of wave intensity difference and uni-directional waveguide

In this paper, a new nanoscale plasmonic differential detector of wave intensities is proposed. This structure can be useful for calibration applications and for finding out if a wave intensity is high enough to pass a threshold level or not. Next, a nanoscale plasmonic uni-directional waveguide is presented. The distinction of this waveguide with similar cases is that the one-way wave-guiding is provided by adding a properly located controlling source, without employing any non-reciprocal material. This feature can be used in many applications that only uni-directional wave propagation is desirable. Both structures have been designed in metal–insulator–metal structure including cavity resonators. The operations are based on the coupling of the wave from input waveguides to the cavity resonators and decoupling to output waveguides in the cavity resonance wavelengths. The simulation results of performance of the structures, as elements applicable to photonic integrated circuits, have been obtained using the numerical method of the finite difference time domain.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Towards physics-informed explainable machine learning and causal models for materials research

From emergent material descriptions to estimation of properties stemming from structures to optimization of process parameters for achieving best performance – all key facets of materials science and related fields have experienced tremendous growth with the introduction of data-driven models. This gradual progression goes at par with developments of machine learning workflows, from purely data-driven shallow models to those that are well-capable in encoding more complex graphs, symbolic representations, invariances, and positional embeddings. Furthermore, this perspective aims at summarizing strategic aspects of such transitions while providing insights into the requirements of bringing in explainable, interpretable predictive models, and causal learning to aid in materials design and discovery. Although the focus remains on a variety of functional materials by providing a handful of case studies, the applications of such integrated methodologies are universal to facilitate fundamental understandings of materials physics while enabling autonomous experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2017

An integrated environmental and health performance quantification model for pre-occupancy phase of buildings in China

To comprehensively pre-evaluate the damages to both the environment and human health due to construction activities in China, this paper presents an integrated building environmental and health performance (EHP) assessment model based on the Building Environmental Performance Analysis System (BEPAS) and the Building Health Impact Analysis System (BHIAS) models and offers a new inventory data estimation method. The new model follows the life cycle assessment (LCA) framework and the inventory analysis step involves bill of quantity (BOQ) data collection, consumption data formation, and environmental profile transformation. The consumption data are derived from engineering drawings and quotas to conduct the assessment before construction for pre-evaluation. The new model classifies building impacts into three safeguard areas: ecosystems, natural resources and human health. Thus, this model considers environmental impacts as well as damage to human wellbeing. The monetization approach, distance-to-target method and panel method are considered as optional weighting approaches. Finally, nine residential buildings of different structural types are taken as case studies to test the operability of the integrated model through application. The results indicate that the new model can effectively pre-evaluate building EHP and the structure type significantly affects the performance of residential buildings.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Operational and scaling-up barriers of SOEC and mitigation strategies to boost H 2 production- a comprehensive review

Solid oxide electrolysis cells (SOECs) proffer a flexible and environmentally friendly solution to reduce CO 2 emissions and/or produce H 2 fuel for various applications. Here, the integration of this technology with renewable energy systems makes them even more promising in realizing a near-perpetual green energy infrastructure in the near future. SOEC technology has achieved stupendous improvement in recent years, and some of the limiting factors to the commercialization of this technology have been explored. It is, therefore, necessary to have a succinct outlook of the different factors that contribute to the recent developments in SOEC technology. The current work presents a comprehensive review of the state-of-the-art SOEC component materials and their degradation mechanisms, SOEC modeling essentials and efficiencies, and the scalability of SOECs. Although SOEC is considered a highly promising technology and sufficient multifaceted research has been done, yet not been widely commercialized. Despite the improvement to mitigate degradation of the SOEC materials, a large share of the degradation concerns sprang from charge transfer reaction at the triple-phase boundaries of the H 2 -electrode. Part of which can be improved by microkinetic modeling of these materials supported by their characterization to give insight into their development. Some other directions for the future in advancing this technology toward the commercialization stage are thoroughly addressed.

08 HYDROGEN↗
DOE OSTI2026

Multi-material additive manufacturing of aluminum 6061-T6 alloy with stainless steel 304: Suppression of intermetallic compounds and interface growth mechanism

Fabricating integrated aluminum-steel structures is difficult because of metallurgical incompatibilities that promote intermetallic compound (IMC) formation at their interfaces. This work introduces a practical route for additively manufacturing 6061-T6 aluminum alloy (AA6061-T6) directly onto 304 stainless steel (SS304) using a high shear strain rate-assisted interfacial bonding mechanism. Through the friction extrusion deposition-based additive manufacturing method, both single- and multi-layer deposits of AA6061-T6 were successfully fabricated on SS304, yielding a robust hybrid multi-material structure. Comprehensive analyses of deposition quality, interface porosity, and bonding performance showed that the interface achieved a tensile strength exceeding 154 MPa under quasi-static loading. Microstructural observations revealed that the deposited aluminum layers experienced severe plastic deformation, resulting in pronounced grain refinement. Importantly, the interfacial zone was found to be free of brittle IMCs, instead containing a thin amorphous layer that evolved through a non-linear reaction-zone growth law. This solid-state additive strategy establishes a promising pathway for lightweight structural systems, nuclear energy component cladding, and multifunctional engineering components, redefining how dissimilar metals can be integrated for advanced applications.

Aluminum alloy↗
DOE OSTI2013

Single-crystalline CuGeO{sub 3} nanorods: Synthesis, characterization and properties

Graphical abstract: - Highlights: • Single crystalline CuGeO{sub 3} nanorods were prepared via a hydrothermal route. • The material exhibits greatly enhanced activity in photocatalytic degradation of dyes. • The magnetic susceptibility measurements indicate spin-Peierls transition properties. • CuGeO{sub 3} nanorods may be of potential application in future integrated optical devices. - Abstract: Single crystalline CuGeO{sub 3} nanorods with a diameter of 20–35 nm and a length up to 1 μm have been prepared via a facile hydrothermal route with the assistance of ethylenediamine. Some influencing factors such as the reaction time, reaction temperature, the volume of ethylenediamine were revealed to play crucial roles in the formation of the CuGeO{sub 3} nanorods. A possible growth mechanism was proposed based on the experimental results. Significantly, this is the first time that CuGeO{sub 3} was used as a photocatalyst for organic pollutant degradation under UV light irradiation. The reaction constant (k) of CuGeO{sub 3} nanorods was five times that of the sample prepared by solid-state reaction under UV light irradiation. Additionally, the optical and magnetic properties of CuGeO{sub 3} nanorods were systematically studied.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Photoluminescence, enhanced ferroelectric, and dielectric properties of Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} multifunctional ceramics

Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) multifunctional ceramics were synthesized by the conventional solid state method. The photoluminescence (PL) excitation and emission spectra, enhanced ferroelectric and dielectric properties were investigated. The X-ray diffraction (XRD) and FESEM analyses indicated that the samples were simple phase and uniform flake-structure. Under the 250–350 nm ultraviolet (UV) excitations, the red emission was obtained and the optimal emission intensity was investigated when Pr doping level was 0.005 mol. With the increasing of the Pr{sup 3+} ion contents, the ferroelectric properties were enhanced obviously. As a new multifunctional material, the Pr{sup 3+}-doped SBN ceramics could be used for a wide range of application, such as integrated electro-optical devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Integrated carbon cloth supported LiFePO4/N-C films as high-performance cathode for lithium ion batteries

Highlights: • Construct carbon cloth supported LiFePO{sub 4}/N-C films via hydrothermal. • The LiFePO{sub 4}/N-C films show high capacity and good cycles. • Carbon cloth and N-C layer work together to provide fast ion/electron transfer. - Abstract: Fabricating advanced cathode is critical for the development of high-performance lithium ion batteries (LIBs). In this work, we develop a facile hydrothermal method for construction of LiFePO{sub 4}/N-C films on the carbon cloth forming integrated binder-free cathode. The LiFePO{sub 4}/N-C films are composed of interconnected nanoscale LiFePO{sub 4}/N-C particles with diameters of 100–200 nm. High porosity and good adhesion are obtained in the carbon cloth supported LiFePO{sub 4}/N-C films (CC + LiFePO{sub 4}/N-C films). As compared to the LiFePO{sub 4}/C powder nanoparticles, the CC + LiFePO{sub 4}/N-C films show much better electrochemical properties with higher capacities, smaller polarization and better high-rate cycling life. A high capacity of 169 mAh g{sup −1} at 1C is achieved for the carbon cloth supported LiFePO{sub 4}/N-C films, superior to the LiFePO{sub 4}/C powder nanoparticles (154 mAh g{sup −1} at 5C). This enhancement is owing to the unique integrated porous architecture and N-C coating. Our work shows a new way to construct integrated cathode for application in LIBs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Graphene foam supported LiFePO4 nanosheets composite as advanced cathode for lithium ion batteries

Highlights: • Construct self-supported porous LiFePO{sub 4}/GF composite film. • Porous LiFePO{sub 4}/GF composite film show superior cycling life. • Hierarchical porous nanosheets structure boost fast electron/ion transfer. - Abstract: Smart design of advanced cathode plays a significantly important role for the development of high-performance lithium ion batteries (LIBs). In this work, we synthesized a new kind of LiFePO{sub 4}/Graphene foam (LFP/GF) integrated binder-free cathode via chemical vapor deposition (CVD) + hydrothermal method. The LFP is composed of interconnected LiFePO{sub 4} nanosheets with numerous nanopores of 50–500 nm. High porosity and good adhesion endow LiFePO{sub 4}/GF film superior electrochemical properties with remarkable high-rate capacities, small polarization and stable cycling life. A high-rate capacity of 110 mAh g{sup −1} at 24 C is obtained for the LiFePO{sub 4}/GF composite. Moreover, a high capacity retention of 95% is acquired after 160 cycles. This enhancement is due to the unique integrated porous LiFePO{sub 4} nanosheets and good support of graphene foam providing fast ion/electron transfer. Our work displays a new insight in constructing integrated cathode for application in high-performance LIBs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Nanoelectronics with proximitized materials

While materials design for many device applications usually relies on adding impurities, recent advances in scaling-down heterostructures with improved interfacial properties offer a different way to transform a large class of materials. A given material can be drastically changed by inheriting properties leaking from its neighboring regions, such as magnetism, superconductivity, or spin-orbit coupling. While these proximity effects often have a short range and are considered negligible, the situation is qualitatively different in atomically thin and two-dimensional materials where the extent of proximity effects can exceed their thickness. Consequently, proximitized materials have a potential to display novel properties and device opportunities, absent in any of the constituent region of the considered heterostructures. Such proximitized materials could provide platforms for a wide range of emerging applications: from seamless integration of memory and logic, to fault-tolerant topologically protected quantum computing.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies

Stimuli-induced structural transformations of molecular assemblies in aqueous solutions are integral to nanotechnological applications and biological processes. In particular, pH responsive amphiphiles as well as proteins with various degrees of ionization can reconfigure in response to pH variations. Here, we use in situ small and wide-angle X-ray scattering (SAXS/WAXS), transmission electron microscopy (TEM), and Monte Carlo simulations to show how charge regulation via pH induces morphological changes in the assembly of a positively charged peptide amphiphile (PA). Monte Carlo simulations and pH titration measurements reveal that ionic correlations in the PA assemblies shift the ionizable amine pK ~ 8 from pK ~ 10 in the lysine headgroup. SAXS and TEM show that with increasing pH, the assembly undergoes spherical micelle to cylindrical nanofiber to planar bilayer transitions. SAXS/WAXS reveal that the bilayer leaflets are interdigitated with the tilted PA lipid tails crystallized on a rectangular lattice. The details of the molecular packing in the membrane result from interplay between steric and van der Waals interactions. We speculate that this packing motif is a general feature of bilayers comprised of amphiphilic lipids with large ionic headgroups. Altogether, our studies correlate the molecular charge and the morphology for a pH-responsive PA system and provide insights into the Å-scale molecular packing in such assemblies.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Confinement and Processing Can Alter the Morphology and Periodicity of Bottlebrush Block Copolymers in Thin Films

Bottlebrush block copolymers (BBCPs) are intriguing architectural variations on linear BCPs with highly tunable structure. Confinement can have a significant impact on polymer assembly, giving rise to changes in morphology, assembly kinetics, and properties like the glass transition. Given that confinement leads to significant changes in the persistence length of bottlebrush homopolymers, it is reasonable to expect that BBCPs will see significant changes in their structure and periodicity relative to the bulk morphology. Understanding how confinement influences assembly will be important for designing BBCPs for thin film applications including membranes, integrated photonic structures, and potentially BCP lithography. In this work, in order to study the effects of confinement on BBCP conformation and morphology, a blade coating was used to prepare films with continuous variation in film thickness. Unlike thin films of linear BCPs, islands/holes were not observed, and instead mixtures of parallel and perpendicular morphologies emerge after annealing. The lamellar periodicity ($L_0$) of the morphologies is found to be thickness dependent, increasing $L_0$ with decreasing film thickness for blade coated films. Films coated out of tetrahydrofuran (THF) resulted in a single well-defined lamellar periodicity, verified through atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS), which increases dramatically from the bulk value (30.6 nm) and continues to increase as the film thickness decreases. The largest observed $L_0$ was 65.5 nm, and this closely approaches the estimated upper limit of 67 nm corresponding to a fully extended backbone in a bilayer arrangement. Films coated out of propylene glycol methyl ether acetate (PGMEA) resulted in a mixture of perpendicular lamellae and a smaller, likely cylindrical morphology. The lamellar portion of the film shows the same thickness dependence as the lamellae observed in the THF coated films. The scaling of the lamellar $L_0$ with respect to film thickness follows predictions for confined semiflexible polymers with weak excluded volume interactions and can be related to models for confinement of DNA. Spin coated films shows the same reduction in periodicity, although at very different film thicknesses. This result suggests that the material has shallow free-energy barriers to transitioning between different $L_0$ and morphologies, a property that could be taken advantage of for patterning diverse structures with a single material.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g( 2 )(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicating the importance of surface passivation on NPL emission quality. Second-order photon correlation (g( 2 )(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. In conclusion, these findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Quantitative Proteomic Analysis of Mouse Embryonic Fibroblasts and Induced Pluripotent Stem Cells Using 16O /18O labeling

Induced pluripotent stem cells (iPSC) hold great promise for regenerative medicine as well as for investigations into the pathogenesis and treatment of various diseases. Understanding of key intracellular signaling pathways and protein targets that control development of iPSC from somatic cells is essential for designing new approaches to improve reprogramming efficiency. Here we report the development and application of an integrated quantitative proteomics platform for investigating differences in protein expressions between mouse embryonic fibroblasts (MEF) and MEF-derived iPSC. This platform consists of 16O/18O labeling, multidimensional peptide separation coupled with tandem mass spectrometry, and data analysis with UNiquant software. Using this platform a total of 2,481 proteins were identified and quantified from the 16O/18O-labeled MEF-iPSC proteome mixtures with a false discovery rate of 0.01. Among them, 218 proteins were significantly upregulated, while 247 proteins were significantly downregulated in iPSC compared to MEF. Many nuclear proteins, including Hdac1, Dnmt1, Pcna, Ccnd1, Smarcc1, and subunits in DNA replication and RNA polymerase II complex were found to be enhanced in iPSC. Protein network analysis revealed that Pcna functions as a hub orchestrating complicated mechanisms including DNA replication, epigenetic inheritance (Dnmt1) and chromatin remodeling (Smarcc1) to reprogram MEF and maintain stemness of iPSC.

16O/18O labeling↗