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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Spectroscopy of Rydberg states in erbium using electromagnetically induced transparency

We present a study of the Rydberg spectrum in 166 Er for series connected to the 4 f 12 ( 3 H 6 )6s, J c = 13/2 and J c = 11/2 ionic core states using an all-optical detection based on electromagnetically induced transparency in an effusive atomic beam. Identifying approximately 550 individual states, we find good agreement with a multi-channel quantum defect theory (MQDT) which allows assignment of most states to ns or nd Rydberg series. We provide an improved accuracy for the lowest two ionization thresholds to E IP, J c =13/2 = 49260:750(1) cm -1 and E IP, J c =11/2 = 49701:184(1) cm -1 as well as the corresponding quantum defects for all observed series. We identify Rydberg states in five different isotopes, and states between the two lowest ionization thresholds. Our results open the way for future applications of Rydberg states for quantum simulation using erbium and exploiting its special open-shell structure.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Creating yellow seed Camelina sativa with enhanced oil accumulation by CRISPR ‐mediated disruption of Transparent Testa 8

Summary Camelina ( Camelina sativa L.), a hexaploid member of the Brassicaceae family, is an emerging oilseed crop being developed to meet the increasing demand for plant oils as biofuel feedstocks. In other Brassicas, high oil content can be associated with a yellow seed phenotype, which is unknown for camelina. We sought to create yellow seed camelina using CRISPR/Cas9 technology to disrupt its Transparent Testa 8 (TT8) transcription factor genes and to evaluate the resulting seed phenotype. We identified three TT8 genes, one in each of the three camelina subgenomes, and obtained independent CsTT8 lines containing frameshift edits. Disruption of TT8 caused seed coat colour to change from brown to yellow reflecting their reduced flavonoid accumulation of up to 44%, and the loss of a well‐organized seed coat mucilage layer. Transcriptomic analysis of CsTT8 ‐edited seeds revealed significantly increased expression of the lipid‐related transcription factors LEC1 , LEC2 , FUS3 , and WRI1 and their downstream fatty acid synthesis‐related targets. These changes caused metabolic remodelling with increased fatty acid synthesis rates and corresponding increases in total fatty acid (TFA) accumulation from 32.4% to as high as 38.0% of seed weight, and TAG yield by more than 21% without significant changes in starch or protein levels compared to parental line. These data highlight the effectiveness of CRISPR in creating novel enhanced‐oil germplasm in camelina. The resulting lines may directly contribute to future net‐zero carbon energy production or be combined with other traits to produce desired lipid‐derived bioproducts at high yields.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Seeing through the nucleus: A review of color transparency phenomena

In this work, we review the current status of the phenomenon of color transparency (CT), a fundamental consequence of the description of hadrons from quantum chromodynamics. CT refers to the vanishing of final (and/or initial) state interactions with the nuclear medium for exclusive process at sufficiently high enough momentum transfers. We discuss the current experimental observations relating to CT and their theoretical implications for other high energy processes. Future CT experiments and facilities are also described.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Silver nanowire-indium zinc oxide composite flexible transparent conducting electrodes made by spin-coating and photonic curing

Flexible transparent conducting electrodes (TCE) play a critical role in modern technologies. Eliminating the high-temperature annealing of vacuum- or solution-deposited films will increase production throughput and lower the cost of the final products. Photonic curing uses intense pulses of broadband light to induce material transformations instead of heat. In this work, we combine solution deposition and photonic curing, replacing thermal annealing, to fabricate flexible composite TCE films on plastic polyethylene terephthalate (PET) substrates. The composite TCE films are composed of spin-coated silver nanowire-indium zinc oxide layers. Further, the TCE films’ electrical, optical, and morphological properties are investigated and compared to those of commercially available PET/TCE. A sheet resistance of 15 Ω/sq and an average transmittance from 400 – 700 nm of 77% are achieved with the spin-coated and photonic-cured composite flexible TCE films.

14 SOLAR ENERGY↗
DOE OSTI2022

Recent Progress in Transparent Conductive Materials for Photovoltaics

Transparent conducting materials (TCMs) are essential components for a variety of optoelectronic devices, such as photovoltaics, displays and touch screens. In recent years, extensive efforts have been made to develop TCMs with both high electrical conductivity and optical transmittance. Based on material types, they can be mainly categorized into the following classes: metal oxides, metal nanowire networks, carbon-material-based TCMs (graphene and carbon nanotube networks) and conjugated conductive polymers (PEDOT:PSS). This review will discuss the fundamental electrical and optical properties, typical fabrication methods and the applications in solar cells for each class of TCMs and highlight the current challenges and potential future research directions.

14 SOLAR ENERGY↗
DOE OSTI2025

Fabricating Silver Nanowire–IZO Composite Transparent Conducting Electrodes at Roll-to-Roll Speed for Perovskite Solar Cells

This study addresses the challenges of efficient, large-scale production of flexible transparent conducting electrodes (TCEs). We fabricate TCEs on polyethylene terephthalate (PET) substrates using a high-speed roll-to-roll (R2R) compatible method that combines gravure printing and photonic curing. The hybrid TCEs consist of Ag metal bus lines (Ag MBLs) coated with silver nanowires (AgNWs) and indium zinc oxide (IZO) layers. All materials are solutions deposited at speeds exceeding 10 m/min using gravure printing. We conduct a systematic study to optimize coating parameters and tune solvent composition to achieve a uniform AgNW network. The entire stack undergoes photonic curing, a low-energy annealing method that can be completed at high speeds and will not damage the plastic substrates. The resulting hybrid TCEs exhibit a transmittance of 92% averaged from 400 nm to 1100 nm and a sheet resistance of 11 Ω/sq. Mechanical durability is tested by bending the hybrid TCEs to a strain of 1% for 2000 cycles. The results show a minimal increase (<5%) in resistance. The high-throughput potential is established by showing that each hybrid TCE fabrication step can be completed at 30 m/min. We further fabricate methylammonium lead iodide solar cells to demonstrate the practical use of these TCEs, achieving an average power conversion efficiency (PCE) of 13%. The high-performance hybrid TCEs produced using R2R-compatible processes show potential as a viable choice for replacing vacuum-deposited indium tin oxide films on PET.

14 SOLAR ENERGY↗
DOE OSTI2021

Siberian Snakes, Figure-8 and Spin Transparency Techniques for High Precision Experiments with Polarized Hadron Beams in Colliders

We present a review of the possibilities to conduct experiments of high efficiency in the nuclear and high energy physics with spin-polarized beams in a collider complex, configuration of which includes Siberian snakes or figure-8 collider ring. Special attention is given to the recently elicited advantageous possibility to conduct high precision experiments in a regime of the spin transparency (ST) when the design global spin tune is close to zero. In this regime, the polarization control is realized by use of spin navigators (SN), which are compact special insertions of magnets dedicated to a high flexibility spin manipulation including frequent spin flips.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Unusually Strong Near‐Infrared Photoluminescence of Highly Transparent Bulk InSe Flakes

Abstract Bulk γ‐InSe has a direct bandgap of 1.24 eV, which corresponds to near infrared wavelengths ( λ = 1.0 µm) useful in optoelectronic applications from biometric detectors to silicon photonics. However, its potential for optoelectronic applications is largely untapped due in part to the lack of quantitative studies of its optical properties. Here, the unusually low absorptance and high photoluminescence quantum efficiency of single‐crystalline InSe flakes with thickness in the hundreds of nanometers are studied. InSe emits brightly at room temperature from its direct bandgap with a peak photoluminescence quantum yield (PLQY) of 20%, despite displaying indirect bandgap like low absorption coefficient due to the symmetry of its crystal structure. By performing pump‐dependent PLQY measurements, the radiative and nonradiative recombination coefficients are extracted, including the Shockley‐Read‐Hall and Auger coefficients. Finally, a proof‐of‐concept alternating current electroluminescent device at low temperature is demonstrated to show the promise of InSe in optoelectronic technology such as highly transparent, bright NIR light sources.

Geng, Jamie↗
DOE OSTI2024

Infrared-Transparent Semiconductor Membranes for Electromagnetic Interference Shielding of Millimeter Waves

Here, it is demonstrated that single-crystalline and highly doped GaAs membranes are excellent candidates for realizing infrared-transparent shields of electromagnetic interference at millimeter frequencies. Measured optical transmittance spectra for the semiconductor membranes show resonant features between 750 and 2500 nm, with a 100% maximum transmittance. The shielding effectiveness of the membranes is extracted from measured scattering parameters between 65 and 85 GHz. Selected GaAs membranes and membranes/polyamide films exhibit shielding effectiveness ranging from 22 to 40 dB, which are suitable values to ensure the safe operation of infrared devices for commercial applications. Theoretical calculations based on a plane wave model show that the interplay of primary reflection and multiple internal reflections of the radio-frequency waves results in broadband shielding capabilities of the membrane between 10 and 300 GHz.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Redesigned Nylon 6 Variants with Enhanced Recyclability, Ductility, and Transparency

Abstract Geminal ( gem −) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem ‐dimethyl groups onto ϵ‐caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem ‐nylon 6’s properties are highly sensitive to the substitution position, with the monomers ranging from non‐polymerizable to polymerizable and the gem ‐nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with the gem ‐dimethyls substituted at the γ position is amorphous and optically transparent, with a higher T g (by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6.

Tian, Jun‐Jie↗
DOE OSTI2022

Integration of Highly Luminescent Lead Halide Perovskite Nanocrystals on Transparent Lead Halide Nanowire Waveguides through Morphological Transformation and Spontaneous Growth in Water

The integration of highly luminescent CsPbBr 3 quantum dots on nanowire waveguides has enormous potential applications in nanophotonics, optical sensing and quantum communications. On the other hand, CsPb 2 Br 5 nanowires have also attracted a lot of attention due to their unique water stability and controversial luminescent property. Here we first report the growth of CsPbBr 3 nanocrystals on CsPb 2 Br 5 nanowires by simply immersing CsPbBr 3 powder into pure water, CsPbBr 3-γ X γ (X = Cl, I) nanocrystals on CsPb 2 Br 5-γ X γ nanowires are then synthesized for tunable light sources. Systematic structure and morphology studies, including in-situ monitoring, revealed that CsPbBr 3 powder was first converted to CsPb 2 Br 5 microplatelets in water, followed by a morphological transformation from CsPb 2 Br 5 microplatelets to nanowires, which is a kinetic dissolution-recrystallization process controlled by electrolytic dissociation and supersaturation of CsPb 2 Br 5 . CsPbB r3 nanocrystals are spontaneously formed on CsPb 2 Br 5 nanowires when nanowires are collected from the aqueous solution. Raman spectroscopy, combined photoluminescence and SEM imaging confirm that the bright emission originates from CsPbBr 3-γ X γ nanocrystals while CsPb 2 Br 5-γ X γ nanowires are transparent waveguides. In conclusion, the intimate integration of nanoscale light sources with a nanowire waveguide is demonstrated through the observation of the wave guiding of light from nanocrystals and Fabry-Perot interference modes of the nanowire cavity.

42 ENGINEERING↗
DOE OSTI2020

Reflected shock-initiated ignition probed via simultaneous lateral and endwall high-speed imaging with a transparent, cylindrical test-section

A TRAnsparent cylindrical (TRAC) shock tube test section has been developed to explore the ignition structure behind reflected shockwaves via simultaneous lateral and endwall high-speed imaging using three fuel/oxidizer mixtures: 0.1% n-C 7 H 16 /1.10% O 2 /4.14% N 2 /94.66% Ar, 0.1% iC 8 H 18 /1.25% O 2 /4.69% N 2 /93.96% Ar, and 5% CH 4 /10% O 2 /85% CO 2 . During mild ignition, the first exothermic centers were located outside of the observable test section. It is shown that with increasing temperature the far-wall ignition events move closer to the endwall, until a strong ignition is achieved. The temperature gradients that promote mild ignition were quantified and were found to have a slight dependence on fuel with the RMS temperature gradients being 0.80% for n-heptane and 1.07% for isooctane. The impact of temperature gradients on metrics used to improve kinetic models, such as species time histories, is noteworthy. From this temperature gradient, an experimental correlation is provided to estimate the transition temperature from mild to strong ignition for a mixture. The effect of diagnostic location in non-homogeneous reactions is quantified in reference to ignition delay. In conclusion, the unique and insightful perspective on the ignition process under heavy shock bifurcation is also discussed.

02 PETROLEUM↗
DOE OSTI2020

Transparent window film with embedded nano-shades for thermoregulation

Every year, more than 20% of the energy consumption in the United States and more than 10% of the global consumption is used towards HVAC (Heating, Ventilating, Air-Conditioning) systems in buildings. Although continued efforts in advancing renewable energy, efficient appliances, and smart building systems are desired, the most critical factors that cause extensive indoor energy consumption are thermal leakage and thermal waste generation. We demonstrate a smart window film that allows natural lighting with a clear view while blocking oblique incident sunlight to make the building interior cooler without using electricity or generating heat. Building upon the concept of, often overlooked, traditional window shades and privacy window films, we emphasize and elevate the application and impact of using magnetically arranged nanoscale material for energy conservation purpose in buildings. By embedding vertically aligned Ni flakes (VANF) in a polymer matrix film, nanoscale mirror array serve as shades to block the high-angled incident sunlight, blocking approximately 73% of total solar irradiance and bringing down the indoor temperature by 1.92 °C during the daytime in a model house while providing nearly 90% transparency. Global application was simulated by applying the respective solar angle and intensity at selected latitudes, indicating their potential. This passively energy-conserving smart film is a low cost, maintenance free, and simple product for users and easy-to-manufacture product for the industry.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Vortex Flow and Cavitation in Liquid Injection: A Comparison between High-Fidelity CFD Simulations and Experimental Visualizations on Transparent Nozzle Replicas

Experimental instantaneous shadowgraph visualizations on transparent glass nozzle replicas of high-pressure fuel injectors have been used to validate a novel in-house high-fidelity LES-VOF multiphase solver, to study the evolution of vortex flow and fuel cavitation. Both experiments and simulations capture the formation of an unsteady vapor structure inside the nozzle volume, which is referred to as 'string-cavitation'; strings are found at the core of the recirculation zones. Furthermore, high-fidelity simulations provide a very detailed insight into the vortex generation in the injector nozzle; strings appear within the time scales that are relevant for fast injection events (on the order of 0.1 milliseconds) and, for the problem under consideration, their generation seems mostly related to the flow pattern in the sac. It is also shown that vortexes interact, merge till they disrupt and favor the temporary inception of shear cavitation.

3-phase LES-VOF solver↗
DOE OSTI2024

The lipidomics reporting checklist a framework for transparency of lipidomic experiments and repurposing resource data

The rapid increase in lipidomic studies has led to a collaborative effort within the community to establish standards and criteria for producing, documenting, and disseminating data. Creating a dynamic checklist that condenses key information about lipidomic experiments into common terminology will enhance the field's consistency, comparability, and repeatability. Here, we describe the structure and rationale of the established Lipidomics Minimal Reporting Checklist to increase transparency in lipidomics research.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

A semiempirical transparency model for dual energy cargo radiography applications

Cargo containers passing through ports are scanned by non-intrusive inspection systems to search for concealed illicit materials. By using two photon beams with different energy spectra, dual energy inspection systems are sensitive to both the area density and the atomic number of cargo contents. Most literature on the subject assumes a simple exponential attenuation model for photon intensity in which only free streaming photons are detected. However, this approximation neglects second order effects such as scattering, leading to a biased model and thus incorrect material predictions. This work studies the accuracy of the free streaming model by comparing it to simulation outputs, finding that the model shows poor atomic number reconstruction accuracy at high- Z and suffers significantly if the source energy spectra and detector response function are not known exactly. To address these challenges, this work introduces a semiempirical transparency model which modifies the free streaming model by rescaling different components of the mass attenuation coefficient, allowing the model to capture secondary effects ignored by the free streaming model. The semiempirical model displays improvement agreement with simulated results at high- Z and shows excellent extrapolation to materials and thicknesses which were not included during the calibration step. Furthermore, this work demonstrates that the semiempirical model yields accurate atomic number predictions even when the source spectra and detector response are not known exactly. In conclusion, using the semiempirical model, manufacturers can perform a simple calibration to enable more precise Z reconstruction capabilities, which has the potential to significantly improve the performance of existing dual energy radiographic systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Nanoscale Electronic Transparency of Wafer-Scale Hexagonal Boron Nitride

We report monolayer hexagonal boron nitride (hBN) has attracted interest as an ultrathin tunnel barrier or environmental protection layer. Recently, wafer-scale hBN growth on Cu(111) was developed for semiconductor chip applications. For basic research and technology, understanding how hBN perturbs underlying electronically active layers is critical. Encouragingly, hBN/Cu(111) has been shown to preserve the Cu(111) surface state (SS), but it was unknown how tunneling into this SS through hBN varies spatially. Here, we demonstrate that the Cu(111) SS under wafer-scale hBN is homogeneous in energy and spectral weight over nanometer length scales and across atomic terraces. In contrast, a new spectral feature-not seen on bare Cu(111)-varies with atomic registry and shares the spatial periodicity of the hBN/Cu(111) moiré. This work demonstrates that, for some 2D electron systems, an hBN overlayer can act as a protective yet remarkably transparent window on fragile low-energy electronic structure below.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Prolonging All-Optical Molecular Electron Spin Coherence in the Tissue Transparency Window

Coherent electron spin states within paramagnetic molecules hold significant potential for microscopic quantum sensing. However, all-optical coherence measurements amenable to high spatial and temporal resolution under ambient conditions remain a significant challenge. Here we conduct room-temperature, picosecond time-resolved Faraday ellipticity/rotation (TRFE/R) measurements of the electron spin decoherence time T 2 * in [IrBr 6 ] 2- . Decoherence is strongly sensitive to solution phase viscosity, pointing to molecular tumbling as an important decoherence mechanism. Accordingly, immobilization of [IrBr 6 ] 2- molecules in thin polymer films results in an order-of-magnitude increase in coherence lifetime and significantly greater magnetic field sensitivity. Here, by tuning energies of ligand-to-metal charge transfer (LMCT) states, TRFE/R enables spin initialization and readout in the tissue transparency window, paving the way toward all-optical, ultrafast molecular electron spin coherence imaging in biological systems.

Electron paramagnetic resonance spectroscopy↗