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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Integrated In Situ Characterization of a Molten Salt Catalyst Surface: Evidence of Sodium Peroxide and Hydroxyl Radical Formation

Sodium-based catalysts (such as Na 2 WO 4 ) were proposed to selectively catalyze OH radical formation from H 2 O and O 2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na 2 WO 4 , which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na 2 O 2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800°C, and these species are useful for various gasphase hydrocarbon reactions, including the selective transformation of methane to ethane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Thermodynamic Understanding of Impurity Phase Segregation in a PdCrO 2 /CuCrO 2 Heterostructure

Abstract PdCrO 2 films are synthesized on CuCrO 2 buffer layers on Al 2 O 3 substrates. This synthesis is accompanied by impurity phase segregation, which hampers the synthesis of high quality PdCrO 2 films. Potential causes ofth impurity phase segregation are studied by using a combination of experiments and ab initio calculations. X‐ray diffraction and scanning transmission electron microscopy experiments reveal impurity phases of Cu x Pd 1 − x alloy and chromium oxides, Cr 2 O 3 and Cr 3 O 4 , in PdCrO 2 . Calculations determine that oxygen deficiency can cause the impurity phase segregation. Therefore, preventing oxygen release from delafossites can suppress the impurity phase segregation. The amounts of Cr 2 O 3 and Cr 3 O 4 depend on temperature and oxygen partial pressure. A reasonable theory‐based explanation for this experimental observation is provided.

2D metal↗
DOE OSTI2022

Vanadium (II) Sulfate for the Reductive Leaching of Chalcopyrite: Replacing Smelting with Electrolysis for Copper Production

The demand for copper is expected to outpace supply in the coming decades due in part to the emergence of wind and solar technologies, which require about five times as much copper as traditional energy sources. This work introduces a potentially transformative hydrometallurgical process to extract copper from chalcopyrite, and thereby sustain a high rate of copper production throughout the 21 st century. Chalcopyrite is reacted with vanadium (II) sulfate for the first time to enable the rapid, clean, and complete recovery of copper. Reactions between 39 g/L copper concentrate, 1 M vanadium (II) sulfate, and various concentrations of sulfuric acid yielded a final product of solid copper sulfate, which was characterized by X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis. The solid products were leached in a subsequent step to demonstrate copper yields ranging from 95–99%. The vanadium (II) ion may be regenerated by an electrolysis unit that leverages advances in vanadium flow battery technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Lithium-Rich Nanoscale Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Cathode Material Prepared by Co-Precipitation Combined Freeze Drying (CP-FD) for Lithium-Ion Batteries

Nanoscale Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 material is synthesized by a co-precipitation combined freeze drying (CP-FD) method, and compared with a conventional co-precipitation method combined vacuum drying (CP-VD). With the combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM), it is found that the sample from CP-FD method consists of a pure phase with good crystallinity and small, homogenous particles (100-300 nm) with uniform particle size distribution. Inductively coupled plasma spectroscopy (ICP) shows that the sample has a stoichiometric ratio of n((Li)): n((Mn)): n((Ni)): n((Co))=9: 4: 1: 1; and its Brunauer-Emmett-Teller (BET) specific surface area is 5.749 m(2)g(-1). This sample achieves excellent electrochemical properties: its initial discharge capacities are 298.9 mAhg(-1) at 0.1C (20 mAg(-1)), 246.1 mAhg(-1) at 0.5C, 215.8 mAhg(-1) at 1C, and 154.2 mAhg(-1) at 5C (5C charge and 5C discharge), as well as good cycling performance. In addition, the Li+ chemical diffusion coefficient of Li1.2Mn0.54Ni0.13Co0.13O2 material prepared by the CP-FD method is 4.59 x 10(-11) cm(2) s(-1), which is higher than that of the Li1.2Mn0.54Ni0.13Co0.13O2 material prepared by CP-VD. This phenomenon illustrates the potential for Li1.2Mn0.54Ni0.13Co0.13O2 with good rate performance synthesized by CP-FD method.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Total Recoverable Aluminum: Not Totally Relevant for Water Quality Standards

Abstract A large water quality data set, representing more than 100 surface-water locations sampled from 2007 to 2017 in the Los Alamos area of New Mexico, USA's Pajarito Plateau, was assembled to evaluate Al concentrations in unfiltered and filtered samples. Aluminum concentrations often exceeded United States Environmental Protection Agency (USEPA) and New Mexico ambient water quality criteria (AWQC), regardless of filter size and sample location. However, AWQC are based on laboratory toxicity studies using soluble Al salts and do not reflect natural conditions in Pajarito Plateau surface waters. The plateau is predominately covered by glassy and recrystallized volcanic ashes (e.g., Bandelier Tuff) containing colloidal to sand-sized aluminosilicates. Samples from natural background drainages and areas downstream of developed regions exhibited similar Al concentrations, suggesting that AWQC exceedances are caused by naturally elevated Al concentrations. Solubility calculations indicated that most samples were oversaturated with respect to amorphous Al(OH)3(s). Therefore, AWQC exceedances are likely artifacts of the “total recoverable” sample preparation, which includes acidification and partial digestion, thereby liberating nonbioavailable Al from aluminosilicates. Accordingly, Al concentrations were strongly associated with suspended sediment concentrations (SSCs), implying that aluminosilicates in suspended sediment contributed to AWQC exceedances and Al oversaturation. Solid-phase particle characterization, using X-ray diffraction (XRD) and scanning electron microscopy with electron dispersive spectroscopy (SEM/EDS) did not identify potentially bioavailable amorphous Al(OH)3(s) in any sample tested. Thus, current sample collection and analysis protocols should not be used to evaluate attainment of Al AWQC on the Pajarito Plateau or locations where aluminosilicates are substantial contributors to total recoverable Al. A sample preparation method (e.g., pH 4 extraction) capable of differentiating nonbioavailable and bioavailable forms of Al is recommended. Otherwise, current New Mexico and USEPA sample preparation approaches will continue to generate artifactual AWQC exceedances in surface waters that contain aluminosilicates. Integr Environ Assess Manag 2019;00:1–14. © 2019 SETAC

Ryan, Adam C.↗
DOE OSTI2020

Positron annihilation lifetime spectroscopy study of polyvinylpyrrolidone‐added polyvinylidene fluoride membranes: Investigation of free volume and permeation relationships

ABSTRACT Polyvinylidene fluoride (PVDF) membranes were prepared via the phase inversion method from casting solutions containing PVDF, dimethylformamide (DMF), and polyvinylpyrrolidone (PVP) as pore former. PVP was used in the casting solution in a range of 0–5 wt % and extracted. The effect on membranes of using PVP in the casting process was analyzed by X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, viscosity, and water permeability techniques. With an increase of PVP from 0 to 5 wt %, the PVDF casting solution viscosities increased from 858 to 1148 cP; the resulting PVDF membrane thickness increased; and the crystallinity of PVDF membranes decreased from 40.0 to 33.3%, which indicates that the addition of PVP inhibits the degree of crystallization in the PVDF membranes. SEM results revealed the shape and size of macropores in the membranes; these macropores changed after PVP addition to the casting solutions. The impact of structural changes on free‐volume properties was evaluated using positron annihilation lifetime spectroscopy (PALS) studies. PALS analysis indicated no effect on the average radius (~3.4 Å) of membrane free‐volume holes from the addition of PVP to the casting solution. However, the percentage of o ‐Ps pick‐off annihilation intensity, I 3 , increased from 1.7 to 5.1% with increased PVP content. Further, increasing the PVP content from 0.5 to 5% resulted in an increased final pure water permeability flux. For instance, the 210 min flux for a 14% PVDF + 0.5% PVP membrane was found to be 3.3 times greater than a control membrane having the same PVDF concentration. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58 , 589–598

Eren, Bilge↗
DOE OSTI2017

Deformation and damage of sintered low-porosity aluminum under planar impact: microstructures and mechanisms

In this paper, plate impact experiments are conducted to study compaction and spallation of 5% porosity aluminum. Free surface velocity histories, the Hugoniot elastic limit (HEL), and spall strengths are obtained at different peak stresses and pulse durations. Scanning electron microscopy, electron backscatter diffraction, and X-ray computed tomography are used to characterize 2D and 3D microstructures. 3D void topology analyses yield rich information on size distribution, shape, orientation, and connectivity of voids. HEL decreases/increases with sample thickness/impact velocity and approaches saturation. Its tensile strength increases with increasing peak stress and shock-induced densification. With the enhanced compaction under increasing impact velocities, spall damage modes change from growth of original voids to inter-particle crack propagation and to “random” nucleation of new voids. Such a change in damage mechanism also gives rise to a distinct decrease in damage extent at high impact velocities. Finally, compaction induces strain localizations around the original voids, while subsequent tension results in grain refinement, and shear deformation zones between staggered cracks.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis and Characterization of MoNb Films Superconducting at 100-200 mK

We have developed a new transition-edge sensor material with critical temperature (T-c) in the range 100-200 mK. The new material is a solid solution of two superconducting components, MoxNb1-x, co-sputtered from two high-purity single-component targets (Mo and Nb). The T-c has a minimum (dT(c)/dx = 0) at an intermediate concentration of the components. We have optimized the deposition parameters and composition to provide films with a sharp superconducting transition at ~ 150 mK. We investigated structural features of the films and surface morphology using X-ray diffraction (XRD) and scanning electron microscopy. The XRD measurements indicate that the grown films are polycrystalline, with a preferred orientation along the (110) crystal direction and a clear correlation between superconducting properties and film microstructure.

superconducting alloys↗
DOE OSTI2018

Effect of Aluminizing on the High-Temperature Oxidation Behavior of an Alumina-Forming Austenitic Stainless Steel

Due to their excellent oxidation resistance and creep resistance at elevated temperatures, alumina forming austenitic (AFA) stainless steels have emerged as potential alloys for high temperature applications. In this study, a Reactive Air Aluminizing (RAA) method was used to aluminize the surface of AFA25 stainless steel. The high temperature oxidation behavior of both as-received and aluminized AFA25 was investigated at 850 °C in dry air. The mass gain per unit area was higher for the aluminized AFA25 than for the as-received material. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), performed on the oxide scales following the high temperature oxidation tests, confirmed the formation of alumina scale on both as-received and aluminized AFA. However, the aluminized alloy exhibited a thicker alumina scale on the surface, as well as more extensive penetration of the scale into the subsurface region of the alloy.

Rashidi, S.↗
DOE OSTI2021

Thermodynamic properties of the Nd-Bi system via emf measurements, $\mathrm{DFT}$ calculations, machine learning, and $\mathrm{CALPHAD}$ modeling

Thermodynamic properties of the Nd-Bi system were investigated using a combination of experimental measurements, first-principles calculations based on density functional theory (DFT), data mining and machine learning (DM + ML) predictions, and calculation of phase diagrams (CALPHAD) modeling. The electromotive force (emf) of Nd-Bi alloys in molten LiCl-KCl-NdCl 3 at 773–973 K was measured via coulometric titration of Nd into Bi for the determination of thermochemical properties such as activity coefficients and solubilities of Nd in Bi. A new peritectic reaction of [liquid + NdBi 2 = Nd 3 Bi 7 ] at 774 K was confirmed using differential scanning calorimetry, structural (X-ray diffraction), and microstructural (scanning electron microscopy) analyses. The unknown crystal structure of NdBi2 was suggested to be a mixture of the anti-La 2 Sb configuration and the La 2 Te-type configuration based on ML predictions for over 26,000 data-mined AB 2 -type configurations together with DFT-based verifications. Using the newly acquired experimental data and DFT-based calculations, the thermodynamic description of the Nd-Bi system was remodeled, and a more complete Nd-Bi phase diagram was calculated, including the Nd 3 Bi 7 compound, invariant transition reactions, and liquidus temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Origin, parameters, and underlying deformation mechanisms of propagating deformation bands in irradiated 316L stainless steel

Lüders-type propagating deformation bands were observed in specimens of irradiated 316L stainless steel samples removed from Spallation Neutron Source target vessels after service. Mechanical testing with digital image correlation (DIC) and in-situ tensile testing with scanning electron microscopy electron backscatter diffraction showed that the observed Lüders-type behavior was not related to the known transformation-induced plasticity or twinning-induced plasticity behavior. Instead, the phenomenon occurs at small local strain values before a significant amount of martensite or deformation twins appear in the microstructure. Microstructural analysis and in-situ mechanical test results suggest Lüders-type band formation and propagation were related to the appearance and evolution of defect-free channels—analogous to slip bands. A modified Swift equation with a Ludwigson-like component was offered to rationalize the phenomenon and model the strain-softening processes at small strain values. Finally, the results indicate complex microstructural processes and deformation mechanisms were active at small strain values and underline the benefits of advanced mechanical test approaches such as DIC.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Insights into twinning in $\mathrm{Mg AZ31: A}$ combined $\mathrm{EBSD}$ and machine learning study

To explore the driving forces behind deformation twinning in Mg AZ31, a machine learning framework is utilized to mine data obtained from electron backscatter diffraction (EBSD) scans in order to extract correlations in physical characteristics that cause twinning. The results are intended to inform physics-based models of twin nucleation and growth. A decision tree learning environment is selected to capture the relationships between microstructure and twin formation; this type of model effectively highlights the more influential characteristics of the local microstructure. Trees are assembled to analyze both twin nucleation in a given grain, and twin propagation across grain boundaries. Each model reveals a unique combination of crystallographic attributes that affect twinning in the Mg. Twin nucleation is found to be mostly controlled by a combination of grain size, basal Schmid factor, and bulk dislocation density while twin propagation is affected most by grain boundary length, basal Schmid factor, angle from grain boundary plane to the RD plane, and grain boundary misorientation. The machine learning framework can be readily adapted to investigate other relationships between microstructure and material response.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Monitoring structural variation on Gd ratio of La modified bismuth ferrite ceramics with enhanced magnetization

Critical structural variation and dielectric properties were investigated in Lanthanum and Gadolinium co-substituted bismuth ferrite (Bi 0.9 La 0.1 Fe 1-x Gd x O 3 (x = 0.01, 0.03, 0.05, 0.07, 0.1, and 0.15). Conventional solid state reaction technique was used to synthesize ceramic samples. To investigate the influence of co-substitution on the phase formation and crystal structure, X-ray diffraction method (XRD), Scanning electron microscopy (SEM) and Raman spectroscopy were utilized. Probing the structural properties by changing Gd ratio was carried out to ensure single phase of rhombohedral R3c structure. Hence, the exploration of dielectric properties of single phase modified BiFeO 3 (BFO) ceramic was executed by room temperature capacitance and loss tangent measurements. It was found that by substitution of 10 mol% La for Bi and up to 5 mol% Gd for Bi, perovskite structure of rhombohedral symmetry and R3c space group were formed. This possessed enhanced magnetization and reduced dielectric loss compared to pure BFO.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and magnetic properties of ferrimagnetic ε-phase Mn 4 N and antiferromagnetic ζ-phase Mn10N thin films on MgO(001)

Single phase ε-Mn 4 N and ζ-Mn 10 N thin films are grown on MgO(001) using molecular beam epitaxy. The films are identified and characterized using reflection high-energy electron diffraction, x-ray diffraction, back scattered electron scanning electron microscopy, atomic/magnetic force microscopy and Rutherford backscattering spectrometry. These films are found to be highly smooth with root-mean-squared roughnesses 3.39 nm and below. The quality of ε-Mn 4 N grown is strongly dependent on substrate temperature during growth. Epitaxial growth of substantial grains composed of the antiferromagnetic η-phase Mn 3 N 2 side by side with ferrimagnetic ε-phase grains is observed when growth temperature is below 480 °C. Ising domains isolated within areas roughly 0.5 μm across are observed in the ferrimagnetic ε-phase grains of samples consisting of a mix of η- and ε-phase grains. Magnetic domains following semi-continuous paths, which are 0.7–7.2 μm across, are observed in single phase ε-Mn4N. Measurements of the ζ-phase detail the structure and magnetism of the material as high Mn content γ-type ζ-phase with a regular surface corrugation along the [100]-direction and antiferromagnetic.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effects of the particle properties on electrochemical performance of nanocrystalline LiAl 0.1 Cu 0.1 Mn 1.8 O 4 cathode materials prepared by ultrasonic spray pyrolysis

LiAl 0.1 Cu 0.1 Mn 1.8 O 4 particles were prepared by the ultrasonic spray pyrolysis using nitrate salts at 800 °C in air atmosphere. The effects of ultrasonic frequency (120 kHz and 2.4 MHz) of the atomizer on the particle properties were investigated by X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive spectroscopy. In addition, cyclic voltammetry and galvanostatic tests were performed to study the influence of the particle structure on the electrochemical behavior in Li-ion battery half-cell. Particle characterization studies reveal that the LiAl 0.1 Cu 0.1 Mn 1.8 O 4 particles have a nanocrystalline spinel structure. The secondary particles have a spherical morphology and the average particle size of the samples decreases with increase in frequency from 3.5 μm to 770 nm. Both samples have porous and partly hollow structure. The initial discharge capacities of LiAl 0.1 Cu 0.1 Mn 1.8 O 4 particles produced using 120 kHz and 2.4 MHz atomizers are 82 and 75 mAh·g -1 , respectively, between 3.0 and 4.8 V at 0.1C rate. Discharge capacities at the 4 V potential region drop to 85% of the initial values for both samples after 110 cycles. Although the micron-sized LiAl 0.1 Cu 0.1 Mn 1.8 O 4 particles exhibit higher capacity at 0.1C than the finer particles, the cathode prepared from the submicron particles has a better rate capability with a retention of the discharge capacity that is 3 times higher at 4C rate.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Relative impact of H 2 O and O 2 in the oxidation of UO 2 powders from 50 to 300 °C

Here, we studied the reaction of water and molecular oxygen with stoichiometric uranium dioxide (i.e. UO 2 ) powder at elevated temperature by high-resolution x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, powder x-ray diffraction (XRD), and scanning electron microscopy (SEM). We observed and quatified oxidation resulting from the dissociative chemisorption of the adsorbing molecules and subsequent incorporation into the oxide lattice. Molecular oxygen was found to be a stronger oxidation agent than water at elevated temperatures but not at ambient.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microstructure and fracture toughness characterization of three 9Cr ODS EUROFER steels with different thermo-mechanical treatments

Ferritic martensitic ODS steels are one of the candidate structural materials for future Gen-IV nuclear fission and fusion reactors. Here, the dependence of fracture toughness on microstructure was investigated by comparing three 9Cr ODS EUROFER steels manufactured through different thermo-mechanical processing routes. Quasi-static fracture toughness testing was performed with sub-sized C(T) specimens and microstructural characterization was carried out using scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. It was found that at lower test temperatures (-100 – 22 °C), the fracture toughness was primarily controlled by crack initiation at sub-micron particles and by production of secondary cracks during fracture. At higher temperatures (above 100 °C), fracture toughness was predominantly controlled by the matrix ductility and the grain boundary strength with a relatively ductile coarse-grained alloy demonstrating higher fracture toughness compared to high-strength fine-grained alloys. These results and discussion show that variations in thermomechanical treatments can produce significant differences in microstructure and fracture toughness behavior of ferritic martensitic ODS steels.

36 MATERIALS SCIENCE↗