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Devaraj, Arun

Publications and source records attributed to Devaraj, Arun.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Extraction of Rare Earth Elements using Magnetite@MOF Composites

Magnetic core-shell microspheres were developed to extract rare earth elements (REEs) from aqueous and brine solutions with up to 99.99% removal efficiency. The shell, composed of a thermally and chemically stable functionalized metal-organic framework (MOF), is grown over a synthesized Fe3O4 magnetic core (magnetite@MOF). The composite particles can be removed from the mixture under an applied magnetic field, offering a practical, and efficient REE-removal process.

Elsaidi, Sameh K.↗
DOE OSTI2018

A Review of Metastable Beta Titanium Alloys

In this article, we provide a broad and extensive review of beta titanium alloys. Beta titanium alloys are an important class of alloys that have found use in demanding applications such as aircraft structures and engines, and orthopedic and orthodontic implants. Their high strength, good corrosion resistance, excellent biocompatibility, and ease of fabrication provide significant advantages compared to other high performance alloys. The body-centered cubic (bcc) ß-phase is metastable at temperatures below the beta transus temperature, providing these alloys with a wide range of microstructures and mechanical properties through processing and heat treatment. One attribute important for biomedical applications is the ability to adjust the modulus of elasticity through alloying and altering phase volume fractions. Furthermore, since these alloys are metastable, they experience stress-induced transformations in response to deformation. The attributes of these alloys make them the subject of many recent studies. In addition, researchers are pursuing development of new metastable and near-beta Ti alloys for advanced applications. In this article, we review several important topics of these alloys including phase stability, development history, thermo-mechanical processing and heat treatment, and stress-induced transformations. In addition, we address recent developments in new alloys, phase stability, superelasticity, and additive manufacturing.

beta phase, metastable, titanium, aircraft, biomed↗
DOE OSTI2018

Nanoscale Solute Partitioning and Carbide Precipitation in a Multiphase TRIP Steel Analyzed by Atom Probe Tomography

Nanoscale solute partitioning across multiple constituent phases in a 980-grade quenched and partitioned (Q&P) steel was analyzed using atom probe tomography (APT). The Q&P process was used to increase the C content in the retained austenite phase thereby improving its stability under plastic straining. Significant carbon enrichment of austenite was measured with decreased levels of C in martensite and almost depleted C content in ferrite, supporting the C partitioning mechanism in the literature. The APT analysis of retained austenite surrounded by martensite demonstrated a higher amount of C content compared with retained austenite surrounded by the ferrite phase. Lath and discrete carbide particle precipitation was also observed inside martensite colonies, tying up C and reducing the total amount of C available for austenite stabilization. In addition, the partitioning of Mn and other minor elements was quantitatively investigated by correlating APT and SEM-EBSD. Furthermore, these techniques provide a robust methodology for analyzing nanoscale compositional partitioning in multiphase steels, TRIP steels in particular, which can be used to better explain their microstructure-mechanical property relationships.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy

Grain boundaries in metallic alloys often play a crucial role, not only in determining the mechanical properties or thermal stability of alloys, but also in dictating the phase transformation kinetics during thermomechanical processing. We demonstrate that locally stabilized structure and compositional segregation at grain boundaries—“grain boundary complexions”—in a complex multicomponent alloy can be modified to influence the kinetics of cellular transformation during subsequent thermomechanical processing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography analysis of a metallic nuclear fuel highly relevant to worldwide nuclear non-proliferation efforts —uranium-10 wt% molybdenum (U-10Mo) alloy, new evidence for the existence of grain boundary complexion is provided. We then modified the concentration of impurities dissolved in Υ-UMo grain interiors and/or segregated to Υ-UMo grain boundaries by changing the homogenization treatment, and these effects were used used to retard the kinetics of cellular transformation during subsequent sub-eutectoid annealing in this U-10-Mo alloy during sub-eutectoid annealing. Thus, this work provided insights on tailoring the final microstructure of the U-10Mo alloy, which can potentially improve the irradiation performance of this important class of alloy fuels.

Devaraj, Arun (ORCID:0000000313146212)↗
DOE OSTI2018

Multimodal characterization of solution-processed Cu3SbS4 absorbers for thin film solar cells

The most efficient inorganic thin film chalcogenide-based solar cells use CdTe or CuInGaSe2 (CIGS) as absorber layers, which rely on toxic (Cd) and/or scarce elements (In, Te). The desire for more sustainable solar cells has led to the development of Earth abundant and non-hazardous chalcogenide absorbers. Cu3SbS4 (famatinite) is a promising Earth abundant p-type semiconductor that has a low direct band gap (0.9–1.05 eV), is a superabsorber (absorption coefficient 104–105 cm1), and has potential in low-cost, thin-film solar cells. Although these properties make the Cu3SbS4 phase stand out as a promising material for photovoltaics, to date Cu3SbS4 solar cells have only achieved low efficiencies. In this study, we demonstrate a method for synthesizing Cu3SbS4 nanocrystals and formation of thin-films by coating nanocrystal precursors onto substrates. Optical, structural, and chemical state characterization were performed before and after thermal processing of the Cu3SbS4 films. A detailed experimental analysis of the bulk and surfaces of the Cu3SbS4 absorber films indicate that phase stability and preferential copper oxidation at the surface may limit device performance for Cu3SbS4 based solar cells. These findings may provide significant insight on how to improve Cu3SbS4 based solar cell performance by controlling processing conditions. This research was funded by the United States National Science Foundation – Scalable Nanomanufacturing program (Grant CBET-1449383). A portion of this research was performed at the Northwest Nanotechnology Infrastructure, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS- 1542101). The acquisition of the OSU Titan TEM was supported by the National Science Foundation via the Major Research Instrumentation (MRI) program under Grant No. 1040588, the Murdock Charitable Trust, and the Oregon Nanoscience and Microtechnologies Institute (ONAMI). XANES spectra were obtained through an approved program user proposal at the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The ALS approved program user proposal beam time was obtained through the chemical imaging initiative, an LDRD program at PNNL. We acknowledge Trey Diulus and Dr Igor Lyubinetsky for their assistance with the XPS experiments.

Albuquerque, Gustavo H.↗
DOE OSTI2018

The limiting layer of fish scales: structure and properties

Fish scales serve as a flexible natural armor that have received increasing attention across the materials community. Most efforts in this area have focused on the composite structure of the predominately organic elasmodine, and limited work addresses the highly mineralized external portion known as the Limiting Layer (LL). This coating serves as the first barrier to external threats and plays an important role in resisting puncture. In this investigation the structure, composition and mechanical behavior of the LL were explored for three different fish, including the arapaima (Arapaima gigas), the tarpon (Megalops atlanticus) and the carp (Cyprinus carpio). The scales of these three fish have received the most attention within the materials community. Features of the LL were evaluated with respect to anatomical position to distinguish site-specific functional differences. Results show that there are significant differences in the surface morphology of the LL from posterior and anterior regions in the scales, and between the three fish species. The calcium to phosphorus ratio and the mineral to collagen ratios of the LL are not equivalent among the three fish. Results from nanoindentation showed that the LL of tarpon scales is the hardest, followed by the carp and the arapaima and the differences in hardness are related to the apatite structure, possibly induced by the growth rate and environment of each fish.

Arola, Dwayne D.↗
DOE OSTI2017

PRECIPITATES AND VOIDS IN CUBIC SILICON CARBIDE IMPLANTED WITH 25Mg+ IONS

This study reports on the formation of 25Mg-bearing precipitates and voids in cubic phase silicon carbide (3C-SiC) single crystals implanted to 9.6×1016 25Mg+/cm2 at 673 K and subsequently annealed at 1073 and 1573 K for 2, 6 and 12 h in an Ar environment. Unidirectionally aligned tetrahedral precipitates are observed around the Mg profile peak, many of which are likely cubic MgC2 and tetragonal Mg2Si particles or their precursor structures. There is also evidence that suggests a possible formation of core (MgC2)-shell (Mg2Si) structure in some of the large precipitates. In addition, small spherical voids are observed near the surface, along with the larger faceted voids in the region of maximum vacancy concentration. 25Mg segregation takes place with a dominant fraction of small atomic clusters. The study provides important results needed to fully assess SiC for potential fusion applications.

Jiang, Weilin↗
DOE OSTI2017

Multimodal and In-Situ Chemical Imaging of Critical Surfaces and Interfaces in Li Batteries

Interfaces play a critical role in the properties and lifetime of current generation and advanced batteries. However, detailed characterization of the critical interfaces during battery operation which can enable performance improvements and improved design has been a significant challenge requiring innovative technique development and creative experiments. This paper describes ways that information from a range of microscopy, spectroscopy, and spectrometry tools can be used to address important challenges associated with energy storage science and technology, in particular the development of advanced batteries for consumer use, transportation, , and renewable storage. Expanding the types of measurements that can be made on operational model batteries has significantly expanded the type and quality of information that can be obtained. This paper first shows examples of approaches being used to collect in situ transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS) and x-ray photoelectron spectroscopy data. The final section of the paper briefly shows two examples: the use of in situ XPS to examine SEI layers and a variety of methods including scanning TEM, atom probe tomography, scanning transmission x-ray microscopy (STXM), and x-ray adsorption near edge spectroscopy to understanding improve the performance of layered lithium transition metal oxide (LTMO) cathodes .

interface analysis, batteries in situ method, batt↗
DOE OSTI2017

Reduced Magnetism in Core–Shell Magnetite@MOF Composites

Rare-earth elements (REEs) have significant commercial and military uses.1-3 However, REE extraction through conventional mining processes is expensive and feasible at only a few locations worldwide. Alternative methods are needed to produce REEs from more geographically disperse resources and in a cost effective, environmental friendly manner.4,5 Among various sources, geothermal brine, used for generating geothermal energy can possess attractive concentrations (ppb to ppm level) of REEs along with other dissolved metal ions.6 A system that can selectively trap the REEs using an existing geothermal power plant infrastructure would be an attractive additional revenue stream for the plant operator that could accelerate the development and deployment of geothermal plants in the United States and rest of the world.7,8 Here, we demonstrate a magnetic core-shell approach that can effectively extract REEs in their ionic form from aqueous solution with up to 99.99% removal efficiency. The shell, composed of thermally and chemically stable functionalized metal-organic framework (MOF), is grown over a synthesized Fe3O4 magnetic core. Magnetic susceptibility of the particles was found to decline significantly after in situ growth of a MOF shell, which resulted from oxidation of Fe2+ species of the magnetite (Fe3O4) to Fe3+ species (maghemite). The core-shell particles can be completely removed from the mixture under an applied magnetic field, offering a practical, economic, and efficient REE-removal process.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Effect of Silicon in U-10Mo Alloy

This document details a method for evaluating the effect of silicon impurity content on U-10Mo alloys. Silicon concentration in U-10Mo alloys has been shown to impact the following: volume fraction of precipitate phases, effective density of the final alloy, and 235-U enrichment in the gamma-UMo matrix. This report presents a model for calculating these quantities as a function of Silicon concentration, which along with fuel foil characterization data, will serve as a reference for quality control of the U-10Mo final alloy Si content. Additionally, detailed characterization using scanning electron microscope imaging, transmission electron microscope diffraction, and atom probe tomography showed that Silicon impurities present in U-10Mo alloys form a Si-rich precipitate phase.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Thermal Evaluation of Metal Oxides on Silica Supports

Atomic level engineering of nanoparticles (NPs) with ability to precisely tune its functional properties can help us realize many promising applications in catalytic science. Such a bottom-up approach would require fundamental level understanding of nucleation and subsequent chemical evolution of nanoparticles during synthesis process. In particular, transition metal based nanoparticles such as Cobalt (Co), Nickel (Ni), Iron (Fe), Paladium (Pd), and Platinum (Pt) can serve as catalysts for many important reactions such as syngas conversion, hydrogenation-dehydrogenation reactions and hydro-deoxygenation reactions. The porous SiO2 is widely used as support medium due to their chemical inertness under reducible and reactive chemical environments often encountered during catalytic process. Nevertheless, even chemically benign SiO2 can have interaction with catalyst particles under high temperatures and adversely affect catalytic activity due to the presence of reactive surface functional groups. Although the influence of the support on catalyst activity and the selectivity is widely studied with respect to the strong metal-support interaction (SMSI) and more recently on the electronic effect of metal-support interaction (EMSI), the choice of support and the catalyst preparation method are still mostly determined by the empirical optimization. For this study, we focus on local structural evolution of cobalt and nickel oxide nanoparticles and its interaction with SiO2 support using multi-modal spectroscopic approach involving X-ray absorption spectroscopy (XAS), nuclear magnetic resonance (NMR) and density functional theory (DFT) based computational methods.

Murugesan, Vijayakumar↗
DOE OSTI2017

Nanoscale Compositional Mapping of Spent HZSM-5: An Atom Probe Tomography Study

Zeolites are highly crystalline and porous materials possessing a well-defined one- to three-dimensional pore structure. Zeolites play a major role in the petrochemical industry, exploitation of non-conventional petroleum resources and nonpetroleum resources like gas and coal. Recently, zeolite has been researched heavily in the valorization of biomass for renewable fuel and chemical generation. It has been reported widely that zeolite deactivation can occur via two main mechanisms. The first one is leaching of alumina from the unit structure of the zeolite in the presence of steam; this mechanism causes the irreversible deactivation. The second mechanism is the formation of coke during the transformation of organic compounds in the pores and/or the outer surface and the poisoning of the active sites and/or blocking of the pores. The catalyst deactivation from this mode can be regenerated by burning the catalyst under oxidative conditions. Repeated thermal treatment for spent catalyst regeneration is also shown to cause permanent modification of the zeolite structure. So identifying the nature and the location of the coking material and changes in Al distribution in catalyst after catalytic reactions becomes imperative. Recently, a relatively new technique called atom probe tomography (APT) has been increasingly used to perform 3D quantitative analysis of element distribution with sub-nanometer scale spatial resolution and high mass sensitivity up to the few ppm level of concentration of elements in materials. In the study we used a multimodal approach including C K-edge x-ray absorption along with 13C cross polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) and APT to investigate element distribution within a HZSM-5 as-synthesized condition and after ethanol conversion reaction.

Devaraj, Arun↗
DOE OSTI2017

Detecting the Extent of Cellular Decomposition after Sub-Eutectoid Annealing in Rolled UMo Foils

This report presents an automated image processing approach to quantifying microstructure image data, specifically the extent of eutectoid (cellular) decomposition in rolled U-10Mo foils. An image processing approach is used here to be able to quantitatively describe microstructure image data in order to relate microstructure to processing parameters (time, temperature, deformation).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

To understand how variations in interface properties such as misfit-dislocation density and local chemistry affect radiation-induced defect absorption and recombination, we have explored a model system of CrxV1-x alloy epitaxial films deposited on MgO single crystals. By controlling film composition, the lattice mismatch with MgO was adjusted so that the misfit-dislocation density varies at the interface. These interfaces were exposed to irradiation and in situ results show that the film with a semi-coherent interface (Cr) withstands irradiation while V film, which has similar semi-coherent interface like Cr, showed the largest damage. Theoretical calculations indicate that, unlike at metal/metal interfaces, the misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry, and the precise location of the misfit-dislocation density relative to the interface, drives defect behavior. Together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗