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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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Controlling hydrocarbon transport and electron beam induced deposition on single layer graphene: Toward atomic scale synthesis in the scanning transmission electron microscope
Abstract Focused electron beam induced deposition (FEBID) is a direct write technique for depositing materials on a support substrate akin to 3D printing with an electron beam (e‐beam). Opportunities exist for merging this existing technique with aberration‐corrected scanning transmission electron microscopy to achieve molecular‐ or atomic‐level spatial precision. Several demonstrations have been performed using graphene as the support substrate. A common challenge that arises during this process is e‐beam‐induced hydrocarbon deposition, suggesting greater control over the sample environment is needed. Various strategies exist for cleaning graphene in situ. One of the most effective methods is to rapidly heat to high temperatures, for example, 600℃ or higher. While this can produce large areas of what appears to be atomically clean graphene, mobile hydrocarbons can still be present on the surfaces. Here, we show that these hydrocarbons are primarily limited to surface migration and demonstrate an effective method for interrupting the flow using e‐beam deposition to form corralled hydrocarbon regions. This strategy is effective for maintaining atomically clean graphene at high temperatures where hydrocarbon mobility can lead to substantial accumulation of unwanted e‐beam deposition.
Amorphous oxides as electron transport layers in Cu(In,Ga)Se 2 superstrate devices: Amorphous oxides in Cu(In,Ga)Se 2 superstrate devices
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Comparison Between the f-Electron and Conduction-Electron Density of States in the Falicov-Kimball Model at Low Temperature
The spinless Falicov-Kimball model is one of the simplest models of many-body physics. While the conduction-electron density of states is temperature independent in the normal state, the f -electron density of states is strongly temperature dependent—it has an orthogonality catastrophe singularity in the metallic phase and is gapped in the insulating phase. The question we address here is whether the spectral gap is the same for both electron species as T → 0. Finally, we find strong evidence to indicate that the answer is affirmative.
Complete collision data set for electrons scattering on molecular hydrogen and its isotopologues: IV. Vibrationally-resolved ionization of the ground and excited electronic states
Here, we present a comprehensive set of vibrationally-resolved cross sections for electron-impact ionization of molecular hydrogen and its isotopologues (H 2 , D 2 , T 2 , HD, HT, and DT) in both the ground and excited electronic states. We apply the adiabatic-nuclei molecular convergent close-coupling (MCCC) method to calculate cross sections from threshold to 1000 eV for ionization of the ground and excited vibrational levels of the X 1 Σ$^{+}_{g}$, B 1 Σ$^{+}_{u}$, C 1 π u , EF 1 Σ$^{+}_{g}$, a 3 Σ$^{+}_{g}$, and c 3 π u electronic states, representing all states with united-atoms-limit principle quantum number n=1–2. The cross sections are presented in graphical form and provided as both numerical values and analytic fit functions in supplementary data files. The data can also be downloaded from the MCCC database at mccc-db.org.
Rational design of mixed ionic and electronic conducting perovskite oxides for solid oxide fuel cell anode materials: A case study for doped SrTiO3
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Effects of cation compositions on the electronic properties and optical dispersion of indium zinc tin oxide thin films by electron spectroscopy
Highlights: • REELS analysis can provide optical dispersion and electronic properties of oxide materials. • The band gap varied with In/Zn/Sn compositions and increased after annealing. • The optical properties were examined using REELS in conjunction with the Tougaard–Yubero model. • The dispersion parameters were determined by a single-oscillator Wemple–DiDomenico model. • The Zn and Sn contents play a crucial role in determining the single-oscillator constant and dispersion energy of IZTO thin films. - Abstract: The electronic properties and optical dispersion of indium zinc tin oxide (IZTO) films with different cation compositions were investigated by reflection electron energy loss spectroscopy (REELS). The REELS spectra of IZTO films revealed that the band gap varied with different Sn/Zn ratios and In content. The optical properties were examined with REELS data using Tougaard–Yubero model and the results were compared with the envelope of the transmission spectra obtained using a UV-spectrometer. The dispersion behavior of the refractive index from REELS results was studied in terms of the single-oscillator Wemple–DiDomenico model. The results showed that the different compositions of In/Zn/Sn caused a change in the dispersion parameters of IZTO thin films in contrast to the static values of refractive indices and dielectric constant which remained the same. Our work demonstrated that REELS is an efficient tool to study the optical properties of a material by obtaining the optical parameters.
Electron and photon identification in the D0 experiment
The electron and photon reconstruction and identification algorithms used by the D0 Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized.
Observation of a THz-sub-THz spontaneous coherent undulator radiation driven by a low energy electron beam from a thermionic RF electron gun
In this work, we report observations of an intense, multi-band, sub-THz and THz radiation extracted from a similar to 2-3 MeV electron beam with a flat transverse profile propagating in an oversized rectangular waveguide placed into a 3.25 mm gap of a planar undulator having 1.3 cm period and similar to 20 cm length. Radiation outcoupling is accomplished using a horn antenna and a miniature permanent in-vacuum magnet separating the mm-sub-mm-waves and electron beam. A table-top experiment utilizes a radio frequency thermionic electron gun delivering a thousand momentum-chirped microbunches per macropulse and an alpha-magnet producing microbunches of a sub-mm length. Total radiated energy of a sub-millijoule per a microsecond radio frequency macropulse is demonstrated with flux more than ten micro-Joules per centimeter squared. With 1 THz filter the energy measured is about 1 microjoule and flux of a few micro-Joules per centimeter squared.
Advanced silicon tracking detector developments for the future Electron-Ion Collider
The proposed Electron-Ion Collider (EIC) will operate high-luminosity high-energy electron+proton and electron+nucleus collisions at the collision energies from 20 GeV to 141 GeV to solve several fundamental questions in the high energy and nuclear physics fields. Its instantaneous luminosity can reach 10 33-34 cm -2 s -1 and the bunching crossing rate is around 10 ns. The EIC project has received CD1 approval from the US DOE in 2021 and moves toward the machine design and preparation for construction. To realize various particle measurements with high precision at the future EIC, a low material-budget and high-granularity silicon vertex and tracking detector with fine spatial and momentum resolutions and nearly 4π solid angle coverage is desired. The Monolithic Active Pixel Sensor (MAPS) and AC Coupled Low Gain Avalanche Diode (AC-LGAD) technologies stand out of several advanced technology options for the EIC silicon vertex and tracking detector subsystems. The MAPS technology has advanced features of low material budget, low power consumption, good radiation resistance and fine spatial resolution. The AC-LGAD technology can achieve fast timing resolution. Latest studies and progress of the EIC silicon vertex and tracking detector conceptual design, performance validations in simulation and ongoing MAPS and AC-LGAD R&D will be shown. Furthermore, schedule and plan of the EIC project detector development will be discussed as well.
Electron Irradiation Tolerance of Molybdenum Disulfide Two-dimensional Nanolayers Investigated from Electron Diffraction
Structural stability of MoS 2 nanosheets were in-situ investigated from selected area electron diffraction. The nano-sheets were stable at low-energy electron irradiation (80 keV) while degraded under high-energy electron irradiation (120 keV).
Photoemission electron microscopy and scanning electron microscopy of Magnetospirillum magnetotacticum ’s magnetosome chains
Magnetotactic bacteria are of great interdisciplinary interest, since a vast field of applications from magnetic recording media to medical nanorobots is conceivable. A key feature for a further understanding is the detailed knowledge about the magnetosome chain within the bacteria. We report on two preparation procedures suitable for UHV experiments in reflective geometry. Further, we present the results of scanning electron microscopy, as well as the first photoemission electron microscopy experiments, both accessing the magnetosomes within intact magnetotactic bacteria and compare these to scanning electron microscopy data from the literature. From the images, we can clearly identify individual magnetosomes within their chains.
Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization
Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e – /atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Furthermore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate.
Direct Investigation of Mg Intercalation into the Orthorhombic V 2 O 5 Cathode Using Atomic-Resolution Transmission Electron Microscopy [Direct Investigation of Mg intercalation into orthorhombic V 2 O 5 cathode using Atomic Resolution Electron Microscopy Methods]
Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V 2 O 5 , combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electron energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V 2 O 5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV 2 O 5 sample. Results suggest that the electrochemically cycled orthorhombic V 2 O 5 cathode shows a local formation of the theoretically predicted ϵ-Mg 0.5 V 2 O 5 phase; however, the intercalation levels of Mg are lower than predicted. Lastly, this phase is different from the chemically synthesized sample, which is found to represent the δ-MgV 2 O 5 phase.
Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications
With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interesting morphology--a distinctly mesoporous structure. Moreover, the walls of fiber cells are composed of thousands of fibers (or macrofibrils) oriented in a similar angle. Nanofibrils and nanocrystals can be further liberated from macrofibrils by mechanical, chemical, and enzymatic methods. The obtained nanocellulose has unique optical, mechanical, and barrier properties and is an excellent candidate for chemical modification and reconfiguration. Wood is naturally a composite material, comprised of cellulose, hemicellulose, and lignin. Wood is sustainable, earth abundant, strong, biodegradable, biocompatible, and chemically accessible for modification; more importantly, multiscale natural fibers from wood have unique optical properties applicable to different kinds of optoelectronics and photonic devices. Today, the materials derived from wood are ready to be explored for applications in new technology areas, such as electronics, biomedical devices, and energy. The goal of this study is to review the fundamental structures and chemistries of wood and wood-derived materials, which are essential for a wide range of existing and new enabling technologies. The scope of the review covers multiscale materials and assemblies of cellulose, hemicellulose, and lignin as well as other biomaterials derived from wood, in regard to their major emerging applications. Structure-properties-application relationships will be investigated in detail. Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistry, and performance of wood and wood-derived materials is advancing historical applications of these materials. This new level of understanding also enables a myriad of new and exciting applications, which motivate this review. There are excellent reviews already on the classical topic of woody materials, and some recent reviews also cover new understanding of these materials as well as potential applications. This review will focus on the uniqueness of woody materials for three critical applications: green electronics, biological devices, and energy storage and bioenergy.
Nuclear Magnetic Resonance Measurements and Electronic Structure of Pu(IV) in [(Me)4N]2PuCl6
The synthesis, electronic structure, and characterization via single crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, and magnetic susceptibility of (Me4N)2PuCl6 are reported. NMR measurements were performed to both search for the direct 239Pu resonance and to obtain local magnetic and electronic information at the Cl site through 35Cl and 37Cl spectra. No signature of 239Pu NMR was observed. The temperature dependence of the Cl spectra was simulated by diagonalizing the Zeeman and quadrupolar Hamiltonians for 35Cl, 37Cl and 14N isotopes. Electronic structure calculations predict a magnetic ?5 triplet ground state of Pu(IV) in the crystalline electric field of the undistorted PuCl6 octahedron. A tetragonal distortion would result in a very small splitting (20 cm-1) of the triplet ground state into a nonmagnetic singlet and a doublet state. The Cl shifts have an inflection point at T = 15 K, differing from the bulk susceptibility, indicating a nonmagnetic crystal field ground state. The Cl spin-lattice relaxation time is constant down to T = 15 K, below which it rapidly increases, also supporting the nonmagnetic crystal field ground state.
Electron transfer reactivity of the aqueous iron(IV)–oxo complex. Outer-sphere vs proton-coupled electron transfer
Here, the kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, Fe IV (H 2 O) 5 O 2+ (hereafter Fe IV aq O 2+ ), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN) 3 2+ (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS–/ABTS 2– , phenothiazines, Co II (dmgBF 2 ) 2 , macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. Fe IV aq O 2+ oxidizes even Ce(III) (E 0 in 1 M HClO 4 = 1.7 V) with a rate constant greater than 10 4 M –1 s –1 . In 0.10 M aqueous HClO 4 at 25 °C, the reactions of Os(phen) 3 2+ (k = 2.5 × 10 5 M –1 s –1 ), IrCl 6 3– (1.6 × 10 6 ), ABTS 2– (4.7 × 10 7 ), and Fe(cp)(C 5 H 4 CH 2 OH) (6.4 × 10 7 ) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen) 3 2+ and of ferrocenes remained unchanged in the acidity range 0.05 < [H+] < 0.10 M, ruling out prior protonation of Fe IV aq O 2+ and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k 22 + E 0 Fe /0.059) = 17.2 ± 0.8, where k 22 and E 0 Fe are the self-exchange rate constant and reduction potential, respectively, for the Fe IV aq O 2+ /Fe III aq O + couple. Comparison with literature work suggests k 22 < 10 –5 M –1 s –1 and thus E 0 (Fe IV aq O 2+ /Fe III aq O + ) > 1.3 V. For proton-coupled electron transfer, the reduction potential is estimated at E 0 (Fe IV aq O 2+ , H + /Fe III aq OH 2+ ) ≥ 1.95 V.
Systematic Investigation of Electronic States and Bond Properties of LnO, LnO + , LnS, and LnS + (Ln = La–Lu) by Spin–Orbit Multiconfiguration Perturbation Theory
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