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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Thermal and Mechanical Properties of Eco-friendly Poly(Vinyl Alcohol) Films with Surface Treated Bagasse Fibers

Bagasse fibers reinforced poly(vinyl alcohol) (PVA) composite films were successfully prepared by solution casting method. To enhance the dispersing effect of the fillers, alkali treatment of the plant fibers was adopted before the fabrication of composites. The structure and properties of the resulting composites were characterized by scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry, mechanical tests, water uptake and thermal stability in detail. The results showed that bagasse fibers after surface modification exhibited good compatibility with PVA matrix. The increased polarity as well as the roughness would be beneficial to the interaction and mechanical interlocking between the fiber and matrix. Acting as the heterogeneous nucleation agents, the fibers could enhance the degree of crystallization and decrease the supercooling degrees of PVA matrix. The fibers exhibited dramatically reinforcing effect in the matrix, and with the increase of fiber, the Young’s modulus and tensile yield stress increased. The Young’s modulus and tensile yield stress of composites with 8% filler would be 3 and 2 times compared with neat PVA films. The thermal stability decreased a little and the water uptake increased with the increase of filler content. These composite films would find wide applications in green packaging areas for their fine mechanical and thermal properties.

36 MATERIALS SCIENCE↗
NASA NTRS1978

The room-temperature dissociation of the compound Au3Si

Three gold-18.6 at.% silicon specimens which were solidified by quenching from above the liquidus temperature have been reexamined after being stored at room temperature for about 8 years. It was found that the 'metastable' compound Au3Si formed on quenching had begun to dissociate by a surface nucleated, solid-state reaction. The reaction front had advanced about 0.2 mm from the surface, leaving a rim of dissociation products. These dissociation products were studied using optical and scanning electron microscopy, electron beam microprobe analysis and an X-ray micro-diffraction technique. It was concluded that the reaction produces elemental gold and silicon, as at higher reaction temperatures, but that the scale of dispersion is so extremely fine that the resulting microstructure cannot be resolved by scanning electron microscopy.

Bhattacharya, D.↗
NASA NTRS2005

Polymer based nanocomposites with nanofibers and exfoliated clay

Polymer solutions, containing clay sheets, were electrospun into nanofibers and microfibers that contained clay sheets inside. Controllable removal of polymer by plasma etching from the surface of fibers revealed the arrangement of clay. The shape, flexibility, size distribution and arrangement of clay sheets were observed by transmission and scanning electron microscopy. The clay sheets were partially aligned in big fibers with normal direction of clay sheets perpendicular to fiber axis. Crumpling of clay sheets inside fibers was observed when the fiber diameter was comparable to the lateral size of clay sheets. Single sheets of clay were observed both by catching clay sheets dispersed in water with electrospun nanofiber mats and by the deliberate removal of most of the polymer in the fibers. Thin, flexible gas barrier films, that are reasonably strong, were assembled from clay sheets and polymer nanofibers. Structure of composite films was characterized with scanning electron microscopy. Continuous film of clay sheets were physically attached to the surface of fiber mats. Spincoating film of polymer and clay sheets was reinforced by electrospun fiber scaffold. Certain alignment of clay sheets was observed in the vicinity of fibers.

Meador, Michael A.↗
DOE OSTI2017

SurR9C84A protects and recovers human cardiomyocytes from hypoxia induced apoptosis

Survivin, as an anti-apoptotic protein and a cell cycle regulator, is recently gaining importance for its regenerative potential in salvaging injured hypoxic cells of vital organs such as heart. Different strategies are being employed to upregulate survivin expression in dying hypoxic cardiomyocytes. We investigated the cardioprotective potential of a cell permeable survivin mutant protein SurR9C84A, for the management of hypoxia mediated cardiomyocyte apoptosis, in a novel and clinically relevant model employing primary human cardiomyocytes (HCM). The aim of this research work was to study the efficacy and mechanism of SurR9C84A facilitated cardioprotection and regeneration in hypoxic HCM. To mimic hypoxic microenvironment in vitro, well characterized HCM were treated with 100 µm (48 h) cobalt chloride to induce hypoxia. Hypoxia induced (HI) HCM were further treated with SurR9C84A (1 µg/mL) in order to analyse its cardioprotective efficacy. Confocal microscopy showed rapid internalization of SurR9C84A and scanning electron microscopy revealed the reinstatement of cytoskeleton projections in HI HCM. SurR9C84A treatment increased cell viability, reduced cell death via, apoptosis (Annexin-V assay), and downregulated free cardiac troponin T and MMP-9 expression. SurR9C84A also upregulated the expression of proliferation markers (PCNA and Ki-67) and downregulated mitochondrial depolarization and ROS levels thereby, impeding cell death. Human Apoptosis Array further revealed that SurR9C84A downregulated expression of pro-apoptotic markers and augmented expression of HSPs and HTRA2/Omi. SurR9C84A treatment led to enhanced levels of survivin, VEGF, PI3K and pAkt. SurR9C84A proved non-toxic to normoxic HCM, as validated through unaltered cell proliferation and other marker levels. Its pre-treatment exhibited lesser susceptibility to hypoxia/damage. SurR9C84A holds a promising clinical potential for human cardiomyocyte survival and proliferation following hypoxic injury. - Highlights: • Protection/regeneration of dying myocardium post myocardial infarction is important. • Downregulation of survivin induces apoptosis in hypoxic human cardiomyocytes (HCM). • Bio-replenishment with SurR9-C84A reinstates HCM survival, recovery and growth. • SurR9-C84A targets mitochondrial depolarization, fcTnT and ROS generation in HCM. • SurR9-C84A upregulates survivin, PCNA, PI3K/Akt pathway, VEGF and HSP levels. • SurR9-C84A holds promise as a treatment and preventive agent to replenish survivin.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Optimization of the CVD parameters for ZnO nanorods growth: Its photoluminescence and field emission properties

Highlights: • Home-made CVD reactor fabricated and successfully used for growing ZnO nanorods. • Growth of nanostructures depends on several CVD process parameters. • CVD parameters, flow rate of carrier gas, substrate temperature, Au catalyst droplet size, growth time duration, etc. optimized. • The mechanism of crystal growth understood by studying FESEM/TEM/XRD. • Photoluminescence and Field emission studies done for defects and applications. - Abstract: Vertically aligned single crystalline ZnO nanorods arrays were grown on a silicon substrate in a CVD reactor using Au as a catalyst. The CVD parameters such as substrate temperature, catalyst layer thickness/morphology and reaction time play a crucial role in the synthesis of nanostructures by the vapor-liquid-solid process. By optimizing these various CVD parameters, highly controlled guided growth of ZnO nanorods was achieved. The structural and morphological properties of resultant ZnO nanorods were studied by means of X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction and field emission scanning electron microscopy. The photoluminescence spectroscopy was also done to investigate the defects in grown ZnO nanorods. The field emission results of nanorods array indicated that the properties of the field emission follow Fowler–Nordheim law. The nanorods (grown for 20 min) are vertically aligned on the substrate surface without entanglements and with good crystal quality as well which is very important for several applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Starch-assisted synthesis and optical properties of ZnS nanoparticles

Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Utah FORGE: Well 78B-32 Core Sample Petrographic Analysis Data

This dataset contains an overview of the petrographic, X-ray Diffraction and scanning electron microscopy analyses of core samples from Utah FORGE Well 78B-32 and related data as described in the .zip folder's Description below.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Polyacids as Modulators for the Synthesis of UiO-66

Poly(acrylic acid) (PAA) and poly(vinylbenzoic acid) (PBA) were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization and used as modulators for the synthesis of the metal–organic framework (MOF) UiO-66 (UiO = University of Oslo). Whereas typical syntheses of UiO-66 require large excesses of acid modulators, such as acetic acid or benzoic acid, to achieve controlled particle size and morphology of the resulting MOF particles, the use of polymerized acids allows for narrow particle size distributions at sub-stoichiometric quantities of modulator. Here, we show using scanning electron microscopy and dynamic light scattering techniques that polyacids can act as alternative modulators for the growth of UiO-66.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Advances in Coring Procedures of Silicon Photovoltaic Modules

We describe advances on procedures used for the coring of silicon photovoltaic modules. These procedures involve coring specific locations, starting from the back of the modules, and removing selected parts of the cell structure, while preserving the front tempered glass. The standard coring procedures had to be modified from case to case due to the different cell structures and measurement requirements. We provide examples of the characterization of the cored samples by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Finally, we describe a simple process to create small openings at specific locations on the back of photovoltaic modules to allow for efficiency-related measurement of individual cells and groups of cells.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2016

Effect of T6 heat treatment on the microstructural and mechanical properties of Al–Si–Cu–Mg alloys

In this communication, it is aimed to optimize the conditions for T6 heat treatment of permanent die cast Al–Si–Cu–Mg alloys. Various solutionizing temperatures, aging treatments and soaking times were used to improve / modify the mechanical properties of presently studied alloys. Formation mechanism of the particles was understood by carrying out optical microscopy and energy dispersive X–ray (EDX) spectroscopy measurements. Spherical particles of alloys were studied for their microstructural properties using scanning electron microscopy (SEM). Microhardness test was performed to investigate their mechanical properties. Dependence of cluster formation and microhardness of the alloys on the adequate solutionizing temperature, aging treatment and soaking time has been discussed in detail.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Electron microscopy study of direct laser deposited IN718

The microstructure of direct laser deposited (DLD) IN718 has been investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that the dendrite core microstructure can be linked to the cooling rate experienced during the deposition. A ~ 100 μm wide δ partially dissolved region in the IN718 substrate was observed close to the substrate/deposit boundary. In the deposited IN718, γ/Laves eutectic constituent is the predominant minor microconstituent. Irregular and regular (small) (Nb,Ti)C carbides and a mixture of the carbides and Laves were observed. Most M{sub 3}B{sub 2} borides were nucleated around a (Nb,Ti)C carbide. Needles of δ phase precipitated from the Laves phase were also observed. A complex constituent (of Laves, δ, α-Cr, γ″, and γ matrix) is reported in IN718 for the first time. The formation of α-Cr particles could be related to Cr rejection during the formation and growth of Cr-depleted δ phase. - Highlights: • Secondary phases in IN718 deposits were identified using electron diffraction and EDS. • MC, M{sub 3}B{sub 2}, γ/Laves eutectic and γ/NbC/Laves eutectic were observed. • Needle-like δ phases were precipitated from the Laves phase. • A complex constituent (Laves, δ, α-Cr, γ″ and γ) was reported for the first time.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Electron-bombarded 〈110〉-oriented tungsten tips for stable tunneling electron emission

A clean tungsten (W) tip apex with a robust atomic plane is required for producing a stable tunneling electron emission under strong electric fields. Because a tip apex fabricated from a wire by aqueous chemical etching is covered by impurity layers, heating treatment in ultra-high vacuum is experimentally known to be necessary. However, strong heating frequently melts the tip apex and causes unstable electron emissions. We investigated quantitatively the tip apex and found a useful method to prepare a tip with stable tunneling electron emissions by controlling electron-bombardment heating power. Careful characterizations of the tip structures were performed with combinations of using field emission I–V curves, scanning electron microscopy, X-ray diffraction (transmitted Debye-Scherrer and Laue) with micro-parabola capillary, field ion microscopy, and field emission microscopy. Tips were chemically etched from (1) polycrystalline W wires (grain size ∼1000 nm) and (2) long-time heated W wires (grain size larger than 1 mm). Heating by 10-40 W (10 s) was found to be good enough to remove oxide layers and produced stable electron emission; however, around 60 W (10 s) heating was threshold power to increase the tip radius, typically +10 ± 5 nm (onset of melting). Further, the grain size of ∼1000 nm was necessary to obtain a conical shape tip apex.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Identifying different stacking sequences in few-layer CVD-grown Mo S 2 by low-energy atomic-resolution scanning transmission electron microscopy

We present that atomically thin MoS 2 grown by chemical vapor deposition (CVD) is a promising candidate for next-generation electronics due to inherent CVD scalability and controllability. However, it is well known that the stacking sequence in few-layer MoS 2 can significantly impact electrical and optical properties. Herein we report different intrinsic stacking sequences in CVD-grown few-layer MoS 2 obtained by atomic-resolution annular-dark-field imaging in an aberration-corrected scanning transmission electron microscope operated at 50 keV. Trilayer MoS 2 displays a new stacking sequence distinct from the commonly observed 2H and 3R phases of MoS 2 . Finally, density functional theory is used to examine the stability of different stacking sequences, and the findings are consistent with our experimental observations.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of sucrose on foaming and melting behavior of a low-activity waste melter feed

Reductants, such as sucrose, are added to nuclear waste melter feeds containing high fractions of nitrates and nitrites to reduce excessive foaming during feed-to-glass conversion and to decrease sulfate segregation and increase technetium retention. The sucrose effect on foaming and melting reactions during the conversion was examined using the feed volume expansion, thermogravimetric analysis, evolved gas analysis, X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray spectrometry. Different sucrose additions were used to vary the carbon to nitrogen (C/N) ratio in the melter feed. As C/N ratio increased, the extent of foaming decreased and N2/NO ratio increased in the gas phase evolved. Significant foam suppression, rapid gas release at approximately 250°C, and reduction of transition metal oxides were observed at C/N > 1.1.

Appel, Connor J.↗
DOE OSTI2015

The Effects of Cold Work on the Microstructure and Mechanical Properties of Intermetallic Strengthened Alumina-Forming Austenitic Stainless Steels

In order to achieve energy conversion efficiencies of > 50 pct for steam turbines/boilers in power generation systems, materials are required that are both strong and corrosion-resistant at > 973 K (700 A degrees C), and economically viable. Austenitic steels strengthened with Laves phase, NiAl and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The microstructure and microchemistry of recently developed alumina-forming austenitic stainless steels have been characterized by scanning electron microscopy, transmission electron microscopy, and synchrotron X-ray diffraction. Different thermo-mechanical treatments were performed on these steels to improve their mechanical performance. These reduced the grain size significantly to the nanoscale (similar to 100 nm) and the room temperature yield strength to above 1000 MPa. A solutionizing anneal at 1473 K (1200 A degrees C) was found to be effective for uniformly redistributing the Laves phase precipitates that form upon casting. (C) The Minerals, Metals & Materials Society and ASM International 2015

Hu, B.↗
DOE OSTI2021

Structural and chemical changes from CO2 exposure to self-healing polymer cement composites for geothermal wellbores

Wellbore cement is subjected to a number of mechanical, thermal and chemical stress regimes over its lifetime. Therefore, next generation wellbore cement formulations need to be evaluated in conditions relevant to these environments. In this work, we investigate the mechanism of the alteration of a novel self-healing polymer-cement composite recently reported by our group after exposure to a CO2-rich environment by using synchrotron based X-ray Fluorescence (XRF) and X-ray absorption near edge structure (XANES) and scanning electron microscopy coupled with energy dispersive spectroscopy. Results showed that chemical alteration of the polymer-cement follows the rim carbonation mechanism, similar to conventional cement although carbonation takes place to a lesser extent in polymer-cements despite the higher porosity. Along with detailed mechanistic insights on carbonation in polymer-cement composite, the performance of these in CO2-rich environment is further studied using standard compressive strength analysis.

Elbakhshwan, Mohamed↗
DOE OSTI2016

Irradiation effects in tungsten-copper laminate composite

Tungsten-copper laminate composite has shown promise as a structural plasma-facing component as compared to tungsten rod or plate. The present study evaluated the tungsten-copper composite after irradiation in the High Flux Isotope Reactor (HFIR) at temperatures of 410-780°C and fast neutron fluences of 0.02-9.0×1025 n/m2, E>0.1 MeV, 0.0039-1.76 displacements per atom (dpa) in tungsten. Tensile tests were performed on the composites, and the fracture surfaces were analyzed with scanning electron microscopy. Before irradiation, the tungsten layers had brittle cleavage failure, but the overall composite had 15.5% elongation at 22°C. After only 0.0039 dpa this was reduced to 7.7% elongation, and no ductility was observed after 0.2 dpa at all irradiation temperatures when tensile tested at 22°C. For elevated temperature tensile tests after irradiation, the composite only had ductile failure at temperatures where the tungsten was delaminating or ductile.

Garrison, L. M.↗
DOE OSTI2016

Electron microscopy analysis of high burnup commercial fuel

Modern electron microscopy analysis can provide detailed insight into the microstructure and chemistry of high burnup UO{sub 2} fuel. This more complete understanding of fuel evolution and performance in reactor can provide critical insight necessary to validate fuel performance models and optimize reactor operations. Preliminary results from the investigation of a polished cross-section of high burnup UO{sub 2} fuel (seven cycles) from the H.B. Robinson pressurized water reactor will be discussed. The analysis focuses on scanning electron microscopy (SEM) of the complete cross-section, while scanning transmission electron microscopy (S/TEM) was performed on targeted features identified by SEM where specimens were fabricated by traditional focused ion beam lift-out techniques. Analysis of the complete cross-section allowed for investigation of the microstructural variations from centerline to fuel/clad interface, pellet/pellet interface, and cladding. Secondary electron imaging and backscatter electron imaging was performed to identify variations in the distribution of fission product secondary phases and bubbles/voids. The analysis of the pellet/pellet interface is a unique feature of this sample where initial analysis shows segregation of fission product phases at the pellet/pellet interface and also indicates an interface microstructure lacking of bubbles and voids. X-ray spectrum imaging was performed by both SEM and STEM techniques to identify the composition of the secondary phases present in the fuel. Multivariate statistical analysis (MVSA) of the X-ray spectrum images has been applied to improve the sensitivity of the analysis and highlight minor variations in the fuel chemistry and secondary phases comprised of fission product as well as the distribution of sub-surface Xe gas bubbles in the high burnup structure. The results presented demonstrate the level of microstructural understanding that is attainable with a combination of SEM techniques along with S/TEM techniques.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗