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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Surface Modification of Rock-Forming Minerals of Diamond-Bearing Kimberlites under Interaction with Wastewater and Electrochemically Treated Water

The structural and chemical surface transformation of basic kimberlite-forming minerals (calcite, olivine, serpentine) under the contact with natural and waste mineralized water and products of electrochemical treatment of the water are studied using X-ray photoelectronic spectroscopy, scanning electron microscopy and X-ray spectral micro-analysis, and atomic force microscopy. It is found that contact with kimberlite extract and recycling water induces chemical modification of calcite surface, which consists in adsorption of hydrocarbon impurities, and chlorine- and silica-bearing compounds, majority of which are removed during interaction with the product of electrochemical treatment of recycling water. The change in the structural and chemical surface properties of rock-forming silicates, aside from adsorption–desorption of organic compound, is also connected with the distortion of nano-size layer structure after leaching of Mg, Fe and Si, and with the carbonatization of the surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°C, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid and liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Ab initio simulation of the electronic structure of Ta{sub 2}O{sub 5} crystal modifications

Ab initio simulation of the electronic structure crystalline {beta} and {delta} phases of tantalum(V) oxide (Ta{sub 2}O{sub 5}), representing a promising dielectric material for microelectronics, has been carried out. Both ideal crystals and those with neutral oxygen vacancies in various coordination positions have been studied. The simulation has been performed using the density functional theory with hybrid functionals involving the Hartree-Fock exchange energy. This approach gives a correct description of the bandgap width: 4.1 eV for {beta}-Ta{sub 2}O{sub 5} and 3.1 eV for {delta}-Ta{sub 2}O{sub 5}. The energy levels related to oxygen vacancies in various positions have been determined for the spectra of electron states in {beta}- and {delta}-Ta{sub 2}O{sub 5} polymorphs. It is established that the presence of oxygen vacancies in Ta{sub 2}O{sub 5} crystal modifications leads to the formation of characteristic absorption peaks in their electron energy loss spectra.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Quantum renormalizations in anisotropic multisublattice magnets and the modification of magnetic susceptibility under irradiation

The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[Fe{sup II}(ClO{sub 4}){sub 2}(Fe{sup III}(bpca){sub 2})]ClO{sub 4} containing alternating high-spin (HS) (S = 2) and low-spin (LS) (S = 1/2) iron ions is obtained by the diagram technique for Hubbard operators. The analysis of this equation yields six branches in the excitation spectrum of this magnet. It is important that the crystal field for ions with spin S = 2 is described by the Hamiltonian of single-ion easy-plane anisotropy, whose orientation is changed by 90° when passing from one HS iron ion to another. The U(N) transformation technique in the atomic representation is applied to diagonalize a single-ion Hamiltonian with a large number of levels. It is shown that the modulation of the orientation of easy magnetization planes leads to a model of a ferrimagnet with easy-axis anisotropy and to the formation of energy spectrum with a large gap. For HS iron ions, a decrease in the mean value of the spin projection due to quantum fluctuations is calculated. The analysis of the specific features of the spectrum of elementary excitations allows one to establish a correspondence to a generalized Ising model for which the magnetic susceptibility is calculated in a wide range of temperatures by the transfer-matrix method. The introduction of a statistical ensemble that takes into account the presence of chains of different lengths and the presence of iron ions with different spins allows one to describe the experimentally observed modification of the magnetic susceptibility of the magnet under optical irradiation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Modification of Graphene on a Copper Grid during Femtosecond Laser Irradiation: Electron Diffraction and Raman Spectroscopy Studies

The modification of a graphene sheet, which was fabricated by chemical vapor deposition on a close-meshed copper grid, during powerful femtosecond laser irradiation is studied. The process of long-term irradiation of a sample in vacuum is found to be accompanied by (1) breaking carbon bonds, which is indicated by a decrease in the intensities of the reflections corresponding to electron-beam diffraction by graphene and (2) the formation of new products, which is indicated by the appearance of new diffraction rings and a change in the Raman spectrum of the sample. The compositions of the forming chemical compounds are analyzed. Copper oxides Cu{sub 2}O and CuO are shown to form predominantly on the sample surface as a result of the chemical reactions induced by powerful femtosecond laser pulses.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Hamiltonian formalism in the problem on the modification of the current density profile during the development of tearing instability in a tokamak

The formation of a magnetic island as a result of tearing instability can be interpreted as the bifurcation of an axisymmetric equilibrium configuration at which nested magnetic surfaces are preserved. The modification of the current density profile due to such bifurcation is studied using the Hamiltonian formalism. In the case of a long narrow island, the gradient profile changes to a profile with an extremum on the axis of the magnetic island.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

High-efficiency plasma treatment for surface modification of LPCVD ZnO

Plasma treatment of LPCVD Boron-doped ZnO aimed at surface modification of the films has been performed. We have shown that five minutes treatment with RF magnetron Ar plasma can be sufficient to transform surface morphology from as-deposited V-type to U-type, which better suits the growth and enhances the properties of post-deposited microcrystalline silicon as a material for PV modules. Effect of plasma treatment on optical and electrical properties and surface morphology has been studied. Comparative analysis of the acquired results has shown that short time treatment can provide required changes in surface morphology without significant deterioration of structure and electrical and optical properties of treated films, while long time treatment results in reduction of electronic properties most probably caused by excess defect formation at the surface of ZnO films. These results show that, despite promising outlooks, RF magnetron plasma treatment of ZnO for the production of PV modules requires careful optimization.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

An Effect of Chemical Modification of Surface of Carbon Nanotubes on Their Thermal Conductivity

An effect of partial chemical modification of the surface of a single-walled carbon nanotube on its thermal conductivity is studied. Numerical simulation of heat transfer showed that partial hydrogenation (fluorination) of a nanotube (addition of hydrogen and fluorine atoms from its outer side) can lead to more than a tenfold decrease in thermal conductivity. When the length of the nanotube increases, its thermal conductivity increases in proportion to the logarithm of the length, whereas the proportionality coefficient decreases with an increase in density of hydrogen or fluorine atoms attached. A thermal conductivity reduction coefficient does not depend on the length of the nanotube, but depends on temperature (the lower the temperature, the stronger the decrease) and density of the attached atoms p. When p < 0.25, an increase in density monotonically decreases the thermal conductivity. A decrease is maximum, when density p is 0.25. If only one half of the nanotube is hydrogenated, this half has a lower thermal conductivity. Such a nanotube becomes anisotropic and can be used as a heat transfer rectifier with no more than two percent rectification efficiency.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Measurement of inclusive jet production and nuclear modifications in pPb collisions at $\sqrt{s_{_\mathrm {NN}}} =5.02\,\mathrm{TeV} $

In this study, inclusive jet production in pPb collisions at a nucleon–nucleon (NN) center-of-mass energy of √ s NN = 5.02 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 30.1 nb -1 is analyzed. The jet transverse momentum spectra are studied in seven pseudorapidity intervals covering the range -2.0 < η CM < 1.5 in the NN center-of-mass frame. The jet production yields at forward and backward pseudorapidity are compared and no significant asymmetry about ηCM=0 is observed in the measured kinematic range. The measurements in the pPb system are compared to reference jet spectra obtained by extrapolation from previous measurements in pp collisions at √s = 7 TeV. In all pseudorapidity ranges, nuclear modifications in inclusive jet production are found to be small, as predicted by next-to-leading order perturbative QCD calculations that incorporate nuclear effects in the parton distribution functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Medium-induced modification of azimuthal correlations of electrons from heavy-flavor hadron decays with charged particles in Pb–Pb collisions at $\mathbf {\sqrt{s_{\textrm{NN}}} = 5.02}$ TeV

The azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb–Pb collisions at $\sqrt{s_{\textrm{NN}}} = 5.02$ TeV are reported for the 0–10% and 30–50% centrality classes. This measurement provides access to the jet-like correlation observables in the heavy-flavor sector in Pb–Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum $4< p_\textrm{T}^\textrm{e} < 16~\textrm{GeV}/c$, considering associated particles within the transverse-momentum range $1< p_\textrm{T}^\textrm{assoc} < 7$ GeV/c, and a pseudorapidity difference of $|\Delta \eta |<1$ between the trigger electron and associated particles. The per-trigger nuclear modification factor ( I AA ) is calculated to compare the near- and away-side peak yields to those in pp collisions at $\sqrt{s} = 5.02$ TeV. In 0–10% central collisions, the indicates a hint of enhancement of associated-particle yields with $p_\textrm{T}<3$ GeV/c on the near side, and a suppression of yields with $p_\textrm{T}>4$ GeV/c on the away side. The I AA for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties.

Abualrob, I. J. [University of Houston] (ORCID:000↗
DOE OSTI2023

Reactive Extrusion of Waste Plastics with Compatibilizer and Lightly Pyrolyzed Crumb Rubber for Asphalt Modification

Modifying asphalt is a potentially high-value application for reusing waste plastics because of the high-volume usage of asphalt in highway construction. However, simply blending hot plastics and asphalt encounters difficulties related to the poor solubility of polymers, which limits the formation of a swollen network with asphalt molecules. The polymer phases also tend to coalesce and separate from asphalt during high-temperature storage in static conditions. The present study developed an innovative process to stabilize waste plastics in asphalt and improve binder storage stability by using lightly pyrolyzed crumb rubber together with a chemical compatibilizer. Both polymers were extruded to produce a thermoplastic elastomer (TPE) for asphalt modification. The mechanical performance and chemical reactions of TPEs were characterized via tension test and Fourier transform infrared spectroscopy. The storage stability and rheological properties of modified binder blends were evaluated through laboratory asphalt stability test and dynamic shear rheometer test. Polymer phases and network structures were characterized through optical microscopy. It was found that the pyrolyzed and reactive extrusion process improved the rubber solubility and polymer interaction, and therefore the storage stability of modified binder blends. The co-existence of rigid plastic and soft rubbery regimes in an entangled network provided a promising pathway to improve the mechanical performance of asphalt binders in both high- and low-temperature domains.

Ma, Yuetan↗
DOE OSTI2023

Analysis of a macrophage carbamylated proteome reveals a function in post-translational modification crosstalk

Background. Lysine carbamylation is a biomarker of rheumatoid arthritis and kidney diseases. However, its cellular function is understudied due to the lack of tools for systematic analysis of this post-translational modification (PTM). Methods. We adapted a method to analyze carbamylated peptides by co-affinity purification with acetylated peptides based on the cross-reactivity of anti-acetyllysine antibodies. We also performed immobilized-metal affinity chromatography to enrich for phosphopeptides, which allowed us to obtain multi-PTM information from the same samples. Results. By testing the pipeline with RAW 264.7 macrophages treated with bacterial lipopolysaccharide, 7,299, 8,923 and 47,637 acetylated, carbamylated, and phosphorylated peptides were identified, respectively. Our analysis showed that carbamylation occurs on proteins from a variety of functions on sites with similar as well as distinct motifs compared to acetylation. To investigate possible PTM crosstalk, we integrated the carbamylation data with acetylation and phosphorylation data, leading to the identification 1,183 proteins that were modified by all 3 PTMs. Among these proteins, 54 had all 3 PTMs regulated by lipopolysaccharide and were enriched in immune signaling pathways, and in particular, the ubiquitin-proteasome pathway. We found that carbamylation of linear diubiquitin blocks the activity of the anti-inflammatory deubiquitinase OTULIN. Conclusions. Overall, our data show that anti-acetyllysine antibodies can be used for effective enrichment of carbamylated peptides. Moreover, carbamylation may play a role in PTM crosstalk with acetylation and phosphorylation, and that it is involved in regulating ubiquitination in vitro.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Targeting hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase for lignin modification in Brachypodium distachyon

Abstract Background Hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HCT) is a central enzyme of the so-called “esters” pathway to monolignols. As originally envisioned, HCT functions twice in this pathway, to form coumaroyl shikimate and then, in the “reverse” direction, to convert caffeoyl shikimate to caffeoyl CoA. The discovery of a caffeoyl shikimate esterase (CSE) that forms caffeic acid directly from caffeoyl shikimate calls into question the need for the reverse HCT reaction in lignin biosynthesis. Loss of function of HCT gives severe growth phenotypes in several dicot plants, but less so in some monocots, questioning whether this enzyme, and therefore the shikimate shunt, plays the same role in both monocots and dicots. The model grass Brachypodium distachyon has two HCT genes, but lacks a classical CSE gene. This study was therefore conducted to evaluate the utility of HCT as a target for lignin modification in a species with an “incomplete” shikimate shunt. Results The kinetic properties of recombinant B. distachyon HCTs were compared with those from Arabidopsis thaliana , Medicago truncatula , and Panicum virgatum (switchgrass) for both the forward and reverse reactions. Along with two M. truncatula HCTs, B. distachyon HCT2 had the least kinetically unfavorable reverse HCT reaction, and this enzyme is induced when HCT1 is down-regulated. Down regulation of B. distachyon HCT1, or co-down-regulation of HCT1 and HCT2, by RNA interference led to reduced lignin levels, with only modest changes in lignin composition and molecular weight. Conclusions Down-regulation of HCT1, or co-down-regulation of both HCT genes, in B. distachyon results in less extensive changes in lignin content/composition and cell wall structure than observed following HCT down-regulation in dicots, with little negative impact on biomass yield. Nevertheless, HCT down-regulation leads to significant improvements in biomass saccharification efficiency, making this gene a preferred target for biotechnological improvement of grasses for bioprocessing.

09 BIOMASS FUELS↗
DOE OSTI2015

Femtosecond-laser–induced modifications in Co/Pt multilayers studied with tabletop resonant magnetic scattering

We characterize the magnetic domain structure of Co/Pt multilayer fi lms on length scales below one hundred nanometers using resonant magnetic scattering and magnetic force microscopy. The extreme ultraviolet light for the scattering experiment is created by a laser- based high-order harmonic generation source. After illumination with intense ultrashort laser pulses, we observe pronounced changes in the magnetic structure and morphology. Furthermore, this study points out the importance of a detailed analysis of the different laser-induced modifications of a magnetic thin fi lm that influence the scattering patterns.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulated patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structure of Type IIL Restriction-Modification Enzyme MmeI in Complex with DNA Has Implications for Engineering New Specificities

The creation of restriction enzymes with programmable DNA-binding and -cleavage specificities has long been a goal of modern biology. The recently discovered Type IIL MmeI family of restriction-and-modification (RM) enzymes that possess a shared target recognition domain provides a framework for engineering such new specificities. However, a lack of structural information on Type IIL enzymes has limited the repertoire that can be rationally engineered. We report here a crystal structure of MmeI in complex with its DNA substrate and an S-adenosylmethionine analog (Sinefungin). The structure uncovers for the first time the interactions that underlie MmeI-DNA recognition and methylation (5’-TCCRAC-3’; R = purine) and provides a molecular basis for changing specificity at four of the six base pairs of the recognition sequence (5’-TCCRAC-3’). Surprisingly, the enzyme is resilient to specificity changes at the first position of the recognition sequence (5’-TCCRAC-3’). Collectively, the structure provides a basis for engineering further derivatives of MmeI and delineates which base pairs of the recognition sequence are more amenable to alterations than others.

59 BASIC BIOLOGICAL SCIENCES↗