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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Photoresponse mechanisms of a graphene-based quantum-dot monolayer structure

Hybrid structures of graphene sheets based quantum dots (QDs) are produced via Langmuir–Blodgett (LB) technique. Morphology of the structures produced is investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Two types of hybrid structures are prepared from graphene covered by sublayers of CdSe/CdS/ZnS and CdSe/ZnS QDs. Photocurrent properties are studied by current–voltage characteristics (CVCs) in the dark and while exposed to visible light and ultraviolet (UV) light with an excitation wavelength of 365 nm. The rise and decay times of graphene and QDs after UV illumination are estimated. (laser applications and other topics in quantum electronics)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Electrochemical Degradation of Pt–Ni Nanocatalysts: An Identical Location Aberration-Corrected Scanning Transmission Electron Microscopy Study

The evolution of Pt–Ni nanoparticles supported on amorphous carbon is investigated before and after electrochemical potential cycling (0.6-1.1 V), using aberration-corrected scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). During voltage cycling and due to the dissolution of nanoparticles, single ions/atoms and ionic/atomic clusters emerge and diffuse across the carbon support toward larger nanoparticles, where they redeposit. We observe that the preferred locations for the dissolution are the steps and corners of the nanoparticles. On the other hand, the redeposition process happens often on {111} type planes. In addition, contrary to the conventional view, where larger particles grow isotropically from smaller ones, this research work shows that anisotropic growth of smaller particles occurs during potential cycling. The reason for this behavior seems to be related to the fact that smaller particles with thicker Pt-rich shells trigger the nucleation and deposition of Pt.

catalysts↗
DOE OSTI2016

Anti-phase boundaries at the SrTiO{sub 3}/Si(001) interface studied using aberration-corrected scanning transmission electron microscopy

In this work, the atomic structure of anti-phase boundary defects at the SrTiO{sub 3}/Si (001) interface is investigated by aberration-corrected scanning transmission electron microscopy. Atomic-resolution images reveal an abrupt SrTiO{sub 3}/Si interface with no intermediate oxide layer. Both single and double Si atomic columns (“dumbbells”) from different terraces of the Si(001) surface are visible at the interface. Anti-phase boundaries (APB) consisting of two adjacent TiO{sub 2} planes in the SrTiO{sub 3} (STO) film resulting either from Si surface steps or from the merging of crystalline domains from different surface nucleation sites are identified. These APBs occur on either {110} or {010} planes and both types have displacement vectors of a{sub STO}/2〈110〉.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Surface modification of cellulose acetate membrane using thermal annealing to enhance produced water treatment

This study is performed primarily to investigate the effect of surface modification of cellulose acetate using thermal annealing on the enhancement of membrane performance for produced water treatment. In this study, Cellulose Acetate membranes were casted using dry/wet phase inversion technique. The effect of additive and post-treatment using thermal annealing on the membrane surface were examined for produced water treatment. Therma annealing was subjected to membrane surface at 60 and 70 °C for 5, 10 and 15 second, respectively. Membrane characterizations were done using membrane flux and rejection with produced water as a feed, Scanning Electron Microscopy (SEM) and Fourier Transform Infra Red (FTIR) analysis. Experimental results showed that asymmetric cellulose acetate membrane can be made by dry/wet phase inversion technique. The results from the Scanning Electron Microscopy (FESEM) analysis was also confirmed that polyethylene glycol as additivie in dope solution and thermal annealing was affected the morphology and membrane performance for produced water treatment, respectively. Scanning electron microscopy micrographs showed that the selective layer and the substructure of membrane became denser and more compact after the thermal annealing processes. Therefore, membrane rejection was significantly increased while the flux was slighty decreased, respectively. The best membrane performance is obtained on the composition of 18 wt % cellulose acetate, poly ethylene glycol 5 wt% with thermal annealing at 70° C for 15 second.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Low-temperature atomic layer deposition of copper(II) oxide thin films

Copper(II) oxide thin films were grown by atomic layer deposition (ALD) using bis-(dimethylamino-2-propoxide)copper [Cu(dmap){sub 2}] and ozone in a temperature window of 80–140 °C. A thorough characterization of the films was performed using x-ray diffraction, x-ray reflectivity, UV‐Vis spectrophotometry, atomic force microscopy, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The process was found to produce polycrystalline copper(II) oxide films with a growth rate of 0.2–0.3 Å per cycle. Impurity content in the films was relatively small for a low temperature ALD process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Effect of carbonyl iron particles composition on the physical characteristics of MR grease

Magnetorheological (MR) grease is an extension of the study of magnetorheological materials. The MR grease can help to reduce the particles sedimentation problem occurred in the MR fluids. Within this study, an effort has been taken to investigate the effect of different weight compositions of carbonyl iron particles on the physical and chemical characteristics of the MR grease under off-state condition (no magnetic field). The MR grease is prepared by mixing carbonyl iron particles having a size range of 1 to 10 µm with commercial NPC Highrex HD-3 grease. Characterizations of MR grease are investigated using Vibrating Sample Magnetometer (VSM), Environmental Scanning Electron Microscopy (ESEM), Differential Scanning Calorimeter (DSC) and rheometer. The dependency of carbonyl iron particles weight towards the magnetic properties of MR grease and other characterizations are investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Preparation of Porous Nanofibers from Electrospun Polyacrylonitrile/Polyvinylidene Fluoride Composite Nanofibers by Inexpensive Salt Using for Dye Adsorption

The high surface area of porous nanofibers enhances their performance for many applications. The present study investigated electrospinning and dye adsorption properties of polymeric nanofibers which were porous by various types of salts. The salt/polyacrylonitrile/polyvinylidene fluoride composite nanofibers were electrospun, and the inexpensive salts such as sodium chloride (NaCl), sodium bicarbonate (NaHCO{sub 3}), or calcium chloride (CaCl{sub 2}) was used to manufacture the porous fibers. Subsequently, the salt was removed by a selective dissolution, and salt extraction of nanofibers was performed with the solution of hydrochloric acid (10 wt%). Salt/PVDF/PAN and porous PVDF/PAN composite nanofibers have been applied to dye adsorption of solution. The characteristics of nanofibers were studied by Fourier transform infrared microscopy (FTIR) and scanning electron microscopy (SEM) analysis. FTIR showed that the salt was extracted from PVDF/PAN nanofibers successfully, and SEM indicated that many pores were aligned with the nanofibers. The adsorption capacity of salt nanofibers webs and porous nanofibers webs for Basic Blue 41 were compared with each other, and porous fibers were obtained from NaHCO{sub 3} having the highest dye adsorption value. Adsorption of dyes follows the Langmuir isotherm and pseudo-second order kinetics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

AFe{sub 2}O{sub 4}/(Pb{sub 0.80}Sr{sub 0.20})TiO{sub 3} (A = Mn, Ni and Co): a New Room-Temperature Magnetoelectric Multiferroic Bi-layered Composite Films

The room temperature and magnetic field-dependent dielectric, impedance and magnetoelectric (ME) coupling effect of polycrystalline AFe{sub 2}O{sub 4}/(Pb{sub 0.80}Sr{sub 0.20})TiO{sub 3} (A = Mn, Ni and Co) bi-layered composite films have been investigated. The structural and microstructural analyses using the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal the presence of homogenous growth of both tetragonal and spinel phases without any extra phase and diffusion in the AFO/PST20 bi-layered composite films. Our results show that all composite films exhibit ferroelectric as well as considerable magnetic, indicating magnetoelectric coupling effect. Our results show that the dielectric and impedance properties of AFO/PST20 bi-layered composite films can be manipulated by the magnetic field at room temperature, also indicating the existence of magnetoelectric coupling. The impedance (Z{sup ′} and Z{sup ″}) Nyquist plots show distinct electrical responses with the magnetic field. The maximum magnetoelectric coefficient (α) is found to be α{sub ME}∼ 239 and ∼ 195 mV/cm/Oe for the MFO/PST20 and CFO/PST20 bi-layered composite films, respectively. The above results show that the AFO/PST20 bi-layered composite films are room-temperature multiferroic material that can be potentially used in magnetoelectric devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Josephson Effect in the Micron and Submicron YBCO Constrictions Fabricated Using the Femtosecond Laser Technique

A femtosecond laser was used successfully to fabricate planar micron and submicron-sized constrictiontype Josephson junctions on YBa{sub 2}Cu{sub 3}O{sub 7−x} thin films. A simple program using G-code (control systems) programming language was written to control the movement of the sample stage during the etching process. The constriction’s geometry was investigated using both atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrical transport measurements were performed at different temperatures. Shapiro steps were observed and analyzed. The micron-sized constriction shows a linear relationship for the measured critical current against the temperature which is consistent with the behavior of an S–s’–Stype Josephson junction where “S” stands for a bulk superconductive material that is untouched by the laser and “s”’ is superconducting material whose critical temperature is lower than the value of “S” In the case of the narrower submicronsized constriction, the measured critical current dependence with temperature shows an exponential decay, which is consistent with the behavior of the long S–N–Stype Josephson junction where “N” stands for a normal material. A model is proposed to describe the observed behavior by considering the effect of sample heating during the constriction’s fabrication.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Microstructure and Properties of Fe{sub 3}Al-Fe{sub 3}AlC{sub x} Composite Prepared by Reactive Liquid Processing

A Fe{sub 3}Al-Fe{sub 3}AlC{sub x} composite was prepared using reactive liquid processing (RLP) through controlled mixture of carbon steel and aluminum in the liquid state. The microstructure and phases of the composite were assessed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, optical microscopy, and differential scanning calorimetry. In addition, the density, hardness, microhardness, and elastic modulus were evaluated. The Fe{sub 3}Al-Fe{sub 3}AlC{sub x} composite consisted of 65 vol pct Fe{sub 3}Al and 35 vol pct Fe{sub 3}AlC{sub x} (κ). The κ phase contained 10.62 at. pct C, resulting in the stoichiometry Fe{sub 3}AlC{sub 0.475}. The elastic modulus of the Fe{sub 3}Al-Fe{sub 3}AlC{sub 0.475} composite followed the rule of mixtures. The RLP technique was shown to be capable of producing Fe{sub 3}Al-Fe{sub 3}AlC{sub 0.475} with a microstructure and properties similar to those achieved using other processing techniques reported in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Composite electrolytes ceramic Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}/glassy Li{sub 2}O-Y{sub 2}O{sub 3}-SiO{sub 2}

Highlights: • We synthesized Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}-x wt% 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} (x = 1–10) composites. • Density of the composite samples is higher than one of the sintered Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}. • The composition with x = 5 has high total conductivity, 2.5 × 10{sup −5} S cm{sup −1} at 25 °C. - Abstract: We have investigated the effect of lithium yttrium-silicate glass 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} on the density and total conductivity of tetragonal Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}. An optimal sintering temperature (1200 °C) was selected on the basis of a composite with 1 wt% of the glass having the highest density and total conductivity after annealing at this temperature. A series of composites Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}-x wt% 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} (x = 1–10) was prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. The data revealed that the sintering additive interacted with Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}, causing the glass to crystallize during annealing. The conductivity of the composites was studied using complex impedance spectroscopy over a temperature range of 20–250 °C. The composite with x = 5 exhibited the highest total conductivity at room temperature: 2.5 × 10{sup −5} S cm{sup −1}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Structural and Magnetic Characteristics of Nanocrystalline Co{sub 82}Zr{sub 18} Alloy

In the present study, the structural and magnetic characteristics of nanocrystalline Co{sub 82}Zr{sub 18} alloy with different structure and crystallite sizes were investigated. In this regard, the nanocrystalline Co{sub 82}Zr{sub 18} sample with different structure and crystallite sizes were prepared using a copper boat vacuum induction melting plus melt spinning and subsequent annealing processes. The prepared samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), and vibrating scanning magnetometer (VSM). According to achieved results, single-phase structure of Zr{sub 2}Co{sub 11} can successfully form by means of melt spinning process at wheel speed of 40 m/s. The melt-spun ribbons exhibit hard magnetic properties with the coercivity and saturation of magnetization in the range of 2.3 kOe and 58 emu/g, respectively. The highest value of coercivity in Co{sub 82}Zr{sub 18} alloy was estimated to be about 3 kOe in annealed sample at 500{sup ∘}C for 1 h.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effects of boron addition on the morphology of silicon phases in Al-Si casting alloys

Highlights: • The influence of boron on Si phase was studied. • Boron addition reduces the length of eutectic Si plates in Al-11Si alloys. • Boron addition promotes the nucleation temperature of primary Si phases in Al-14Si alloys. • Boron addition increases the twin density in the <112>{sub Si} growth direction of eutectic Si in Al-11Si and Al-14Si alloys. - Abstract: The influence of B elements on the morphology of Si phases in Al-11Si and Al-14Si alloys has been investigated employing Optical Microscope, Scanning Electron Microscopy, Transmission Electron Microscopy and Differential Scanning Calorimetry. In Al-11Si alloy, the addition of B element not only refines the primary Al dendrites, but also reduces the length of eutectic Si plates. In Al-14Si alloys, the addition of B element promotes the nucleation temperature of primary Si phases, but shows weak influence on the nucleation temperature of eutectics. The effects of B element on the morphologies of both primary Si particle and eutectics can be attributed to the interaction between B and Si elements during the solidification process.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Coating of Steel by Alkyd Resin Reinforced with Al{sub 2}O{sub 3} Nanoparticles to Improve Corrosion Resistance

In this study, an alkyd/Al{sub 2}O{sub 3} nanocomposite coating was prepared and applied on a stainless steel substrate. The Al{sub 2}O{sub 3} nanoparticles (NPs) with different weight ratios (1, 2, and 3 wt.%) were added to the alkyd resin and coated on the substrate via dip-coating technique. Then, the dispersion of NPs in the coating film was investigated using scanning electron microscopy (SEM) and scanning probe microscopy (SPM). The coating thickness estimated by SEM was 20 μm. The corrosion behavior of the coating was examined through the Tafel polarization and salt spray tests. The results showed that the addition of Al{sub 2}O{sub 3} NPs up to 2 wt.% will result in a dense and homogeneous coating which protects the substrate leading to lower corrosion current density from 9.2 × 10{sup −6} to 1.65×10{sup −9} A/cm{sup 2} compared with the uncoated stainless steel.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Corrosion Protection of Phenolic-Epoxy/Tetraglycidyl Metaxylediamine Composite Coatings in a Temperature-Controlled Borax Environment

The failure behavior for two kinds of phenolic-epoxy/tetraglycidyl metaxylediamine composite coatings in 60 °C borax aqueous solution was evaluated using electrochemical methods (EIS) combined with scanning electron microscopy, confocal laser scanning microscope, water immersion test, and Raman spectrum. The main focus was on the effect of curing agent on the corrosion protection of coatings. Results revealed that the coating cured by phenolic modified aromatic amine possessed more compact cross-linked structure, better wet adhesion, lower water absorption (0.064 mg h{sup −1} cm{sup −2}) and its impedance values was closed to 10{sup 8} Ω cm{sup 2} after immersion for 576 h, while the coating cured by modified aromatic ring aliphatic amine was lower than 10{sup 5} Ω cm{sup 2}. The corrosion mechanism of the two coatings is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Three-dimensional mapping of crystalline ceramic waste form materials

Here, we demonstrate the use of synchrotron-based, transmission X-ray microscopy (TXM) and scanning electron microscopy to image the 3-D morphologies and spatial distributions of Ga-doped phases within model, single- and two-phase waste form material systems. Gallium doping levels consistent with those commonly used for nuclear waste immobilization (e.g., Ba 1.04 Cs 0.24 Ga 2.32 Ti 5.68 O 16 ) could be readily imaged. This analysis suggests that a minority phase with different stoichiometry/composition from the primary hollandite phase can be formed by the solid-state ceramic processing route with varying morphology (globular vs. cylindrical) as a function of Cs content. Our results represent a crucial step in developing the tools necessary to gain an improved understanding of the microstructural and chemical properties of waste form materials that influence their resistance to aqueous corrosion. This understanding will aid in the future design of higher durability waste form materials.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Recreating Fuel Cell Catalyst Degradation in Aqueous Environments for Identical-Location Scanning Transmission Electron Microscopy Studies

The recent surge in interest of proton exchange membrane fuel cells (PEMFCs) for heavy-duty vehicles increases the demand on the durability of oxygen reduction reaction electrocatalysts used in the fuel cell cathode. This prioritizes efforts aimed at understanding and subsequently controlling catalyst degradation. Identical-location scanning transmission electron microscopy (IL-STEM) is a powerful method that enables precise characterization of degradation processes in individual catalyst nanoparticles across various stages of cycling. Recreating the degradation processes that occur in PEMFC membrane electrode assemblies (MEAs) within the aqueous cell used for IL-STEM experiments is vital for generating an accurate understanding of these processes. In this work, we investigate the type and degree of catalyst degradation achieved by cycling in an aqueous cell compared to a PEMFC MEA. While significant degradation is observed in IL-STEM experiments performed on a traditional Pt catalyst using the standard accelerated stress test potential window (0.6-0.95 VRHE), degradation of a PtCo catalyst designed for heavy-duty vehicle use is very limited compared to that observed in MEAs. We therefore explore various experimental parameters such as temperature, acid type, acid concentration, ionomer content, and potential window to identify conditions that reproduce the degradation observed in MEAs. We find that by extending the cycling potential window to 0.4-1.0 V RHE in an electrolyte containing Pt ions, the degraded particle size distribution and alloy composition better match that observed in MEAs. In particular, these conditions increase the relative contribution of Ostwald ripening, which appears to play a more significant role in the degradation of larger alloy particles supported on high-surface-area carbons than coalescence. Results from this work highlight the potential for discrepancies between ex situ aqueous experiments and MEA tests. While different catalysts may require a unique modification to the AST protocol, strategies provided in this work enable future in situ and identical-location experiments that will play an important role in the development of robust catalysts for heavy-duty vehicle applications.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Effect of Tempering Temperature on the Precipitation Behavior and Mechanical Properties of a Martensite Ferritic Steel

In this investigation, the precipitation of boron-containing M{sub 23}C{sub 6} in the CB2 steel during tempering was investigated. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, transmission electron microscopy and differential scanning calorimetry were used to analyze the influence of temperature on the microstructure and properties of CB2-tempered martensite ferritic steel. The steel was normalized at 1100 °C for 2 h and then tempered at six different temperatures between 690 and 790 °C for 2 h. During air-cooling following austenitization, the precipitation of M{sub 3}C particles occurred in flakes forming with their diameter and thickness of 100 and 20 nm, respectively. The boron-containing M{sub 23}C{sub 6} was formed on the lath boundary after the dissolution of M{sub 3}C within the boundary. When the tempering temperature increased from 690 to 790 °C, the average diameter of boron-containing M{sub 23}C{sub 6} increased from 132 to 198 nm. Owing to the rapid growth of the precipitates, the phenomenon of lath widening as well as the recovery of microstructure would take place at high temperature. With an increase in the temperature, the tensile and yield strengths decreased gradually, while the plasticity increased and the boron-containing M{sub 23}C{sub 6} grew rapidly. Furthermore, when the tempering temperature exceeded 750 °C, the plasticity of CB2 steel was significantly improved.

36 MATERIALS SCIENCE↗