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At least 253 records · Page 14

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NASA NTRS2008

Spectral Analysis of the Accretion Flow in NGC 1052 with Suzaku

We present an analysis of the 101 ks, 2007 Suzaku spectrum of the LINER galaxy NGC 1052. The 0:3..10 keV continuum is well-modeled by a power-law continuum modified by Galactic and intrinsic absorption, and exhibits a soft, thermal emission component below 1 keV. Both a narrow core and a broader component of Fe-Ka emission are robustly detected at 6:4 keV. While the narrow line is consistent with an origin in material distant from the black hole, the broad line is best fit empirically by a model that describes fluorescent emission from the inner accretion disk around a rapidly rotating black hole. We find no direct evidence for Comptonized reflection of the hard X-ray source by the disk above 10 keV, however, which casts doubt on the hypothesis that the broad iron line is produced in a standard accretion disk. We explore other possible scenarios for producing this spectral feature and conclude that the high equivalent width and full width half maximum velocity of the broad iron line (v greater than or equals 0:37c) necessitate an origin within d approx. 8r(sub g) of the hard X-ray source. Based on the confirmed presence of a strong radio jet in this source, the broad iron line may be produced in dense plasma at the base of the jet, implying that emission mechanisms in the central-most portions of active galactic nuclei are more complex than previously thought.

Brenneman, L. W.↗

NASA NTRS2013

Statistical Issues in Galaxy Cluster Cosmology

The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.

Galaxy↗

NASA NTRS1986

Transfer Casting From Ion-Beam-Textured Surfaces

Textured surfaces created on metals, ceramics, and polymers. Electron-bombardment ion thrustor used as neutralized-ion-beam source. Beam of directed, energetic ions alter surface chemistry and/or morphology of many materials. By adjusting ion energy and ion-beam current density impinging upon target, precise surface modifications obtained without risk of targetmaterial melting or bulk decomposition. Technique developed to generate precise, controllable, surface microstructures on metals, ceramics, and polymers.

Banks, B. A.↗

NASA NTRS2005

Improvements in Fabrication of Sand/Binder Cores for Casting

Three improvements have been devised for the cold-box process, which is a special molding process used to make sand/binder cores for casting hollow metal parts. These improvements are: The use of fiber-reinforced composite binder materials (in contradistinction to the non-fiber-reinforced binders used heretofore), The substitution of a directed-vortex core-blowing subprocess for a prior core-blowing process that involved a movable gassing plate, and The use of filters made from filtration-grade fabrics to prevent clogging of vents. For reasons that exceed the scope of this article, most foundries have adopted the cold-box process for making cores for casting metals. However, this process is not widely known outside the metal-casting industry; therefore, a description of pertinent aspects of the cold-box process is prerequisite to a meaningful description of the aforementioned improvements. In the cold-box process as practiced heretofore, sand is first mixed with a phenolic resin (considered to be part 1 of a three-part binder) and an isocyanate resin (part 2 of the binder). Then by use of compressed air, the mixture is blown into a core box, which is a mold for forming the core. Next, an amine gas (part 3 of the binder) that acts as a catalyst for polymerization of parts 1 and 2 is blown through the core box. Alternatively, a liquid amine that vaporizes during polymerization can be incorporated into the sand/resin mixture. Once polymerization is complete, the amine gas is purged from the core box by use of compressed air. The finished core is then removed from the core box.

Bakhitiyarov, Sayavur I.↗

DOE OSTI2021

A Time-Dependent Directional Damage Theory for Brittle Rocks Considering the Kinetics of Microcrack Growth

In this work, a novel microcrack damage theory for describing the time-dependent behavior of brittle rocks is proposed. Instead of using scalar or tensorial variables to approximate the effect of microcracks, the concept of directional damage is introduced by upscaling the directional distribution density of microcracks through the noninteracting homogenization scheme. The contribution of an individual crack on global strain is first derived from the crack-opening displacements including sliding, closure, and dilation. The model is then cast in the free energy form, and the range of parameters ensuring compliance with the second law of thermodynamics is derived rigorously. Considering that the subcritical propagation of microcracks is the dominant mechanism behind the time-dependent deformation and failure of brittle rocks, the driving force for directional damage is defined as the corresponding energy release rate, and the effect of time is introduced through a damage evolution law inspired from the kinetics of subcritical crack growth. The model is applied to simulate the behavior of basalt rock under various loading conditions. In addition to predicting the stress–strain–time response, the model offers enhanced resolution in representing the anisotropic characteristics of microcrack-induced damage in brittle rocks and their time-dependent evolutions.

58 GEOSCIENCES↗

DOE OSTI2022

Experiment design for the neutron irradiation of $\mathrm{PM-HIP}$ alloys for nuclear reactors

Here, this article describes the design of an Advanced Test Reactor (ATR) drop-in neutron irradiation experiment aiming to directly compare the performance of nuclear structural alloys fabricated by powder metallurgy with hot isostatic pressing (PM-HIP) against conventional casting or forging. There is growing interest in PM-HIP alloys for nuclear applications because of their microstructural uniformity, superior mechanical properties, and reduced dependence on welding and machining, compared to cast/forged alloys. Nuclear code-qualification of PM-HIP alloys requires neutron irradiation testing to demonstrate performance under relevant conditions. In this experiment, six nuclear structural alloys were irradiated: Ni-based alloys 625 and 690, Grade 91 ferritic steel, SA508 pressure vessel steel, and 304L and 316L austenitic stainless steels. The experiment is assembled into seven capsules in four test trains and irradiated in three ATR inboard A positions. Both the PM-HIP and cast/forged versions of each alloy were irradiated under nearly identical conditions for comparative purposes, to target doses of 1 ± 0.2 and 3 ± 0.2 dpa at temperatures of 300 ± 50 °C and 400 ± 50 °C. A thorough description of the experiment design and thermal, structural and neutronic analyses performed to ensure the targeted irradiation conditions are met is provided. Specimens were configured as small disks, compact tension specimens and tensile bars to facilitate post-irradiation examination (PIE) that will include mechanical testing, microstructure characterization, and fracture toughness testing. Given the considerations for ASTM standardized mechanical testing, comparative fluence and temperature across specimen pairs, and comprehensive PIE planning herein, this work serves as a template for future nuclear materials qualification experiment designs.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

NASA NTRS1951

Experimental Investigation of Air-Cooled Turbine Blades in Turbojet Engine. 7: Rotor-Blade Fabrication Procedures

An experimental investigation was conducted to determine the cooling effectiveness of a wide variety of air-cooled turbine-blade configurations. The blades, which were tested in the turbine of a - commercial turbojet engine that was modified for this investigation by replacing two of the original blades with air-cooled blades located diametrically opposite each other, are untwisted, have no aerodynamic taper, and have essentially the same external profile. The cooling-passage configuration is different for each blade, however. The fabrication procedures were varied and often unique. The blades were fabricated using methods most suitable for obtaining a small number of blades for use in the cooling investigations and therefore not all the fabrication procedures would be directly applicable to production processes, although some of the ideas and steps might be useful. Blade shells were obtained by both casting and forming. The cast shells were either welded to the blade base or cast integrally with the base. The formed shells were attached to the base by a brazing and two welding methods. Additional surface area was supplied in the coolant passages by the addition of fins or tubes that were S-brazed. to the shell. A number of blades with special leading- and trailing-edge designs that provided added cooling to these areas were fabricated. The cooling effectiveness and purposes of the various blade configurations are discussed briefly.

Long, Roger A.↗

NASA NTRS1980

Directional solidification at ultra-high thermal gradient

A high gradient controlled solidification (HGC) furnace was designed and operated at gradients up to 1800 C/cm to continuously produce aluminum alloys. Rubber '0' rings for the water cooling chamber were eliminated, while still maintaining water cooling directly onto the solidified metal. An HGC unit for high temperature ferrous alloys was also designed. Successful runs were made with cast iron, at thermal gradients up to 500 C/cm.

Flemings, M. C.↗

NASA NTRS1986

Microstructure and stability of melt spun INCONEL 713 LC

The alloy IN-714LC was used in an investigation of the effect of process parameters on the microstructure of a rapidly solidified melt-spun material. The resultant ribbon microstructure consisted of several distinct regions, each of which corresponds to a different thermal history during processing. A chill zone of equiaxed randomly-oriented grains exists in a region of the foil which was in contact with the wheel during casting. This zone develops into a dendritic growth morphology with distance away from the lower ribbon surface. Dendrites inclined in the direction of wheel rotation result from growth into a flowing stream. TEM studies showed that a cell structure formed, the cell size decreasing with increasing wheel speed. Aging studies indicated that the cell structure plays an important role in gamma prime precipitation. Results relating to heat treatments (as would be encountered in compaction and use) and the stability of the melt-spun structure are considered.

Antolovich, S. D.↗

NASA NTRS1986

Compositional redistribution during casting of Hg sub 0.8 Cd sub 0.2 Te alloys

A series of Hg(0.8)Cd(0.2)Te ingots was cast both vertically and horizontally under well-defined thermal conditions by using a two-zone furnace with isothermal heat-pipe liners. The main objective of the experiments was to establish correlations between casting parameters and compositional redistribution and to develop ground-based data for a proposed flight experiment of casting of Hg(1-x)Cd(x)Te alloys under reduced gravity conditions. The compositional variations along the axial and radial directions were determined by precision density measurements, infrared transmission spectra, and X-ray energy dispersion spectrometry. Comparison between the experimental results and a numerical simulation of the solidification process of Hg(0.8)Cd(0.2)Te is described.

Su, Ching-Hua↗

NASA NTRS1988

The origin and location of the 5 March 1979 gamma-ray burst

Evidence and arguments concerning the origin and location of the gamma-ray burst (GRB) of March 5, 1979 are reviewed. This GRB has been positionally identified with the SNR 49 in the LMC. Such an association would fix the GRB's distance at 55 kpc, and the observed flux from the GRB would require prodigious energy and luminosity, casting doubt on the GRB's distance and its association with the LMC. Some Kosmos 856 observations which may provide more direct evidence on the energy released are discussed.

Kazanas, Demosthenes↗

NASA NTRS1988

Compositional redistribution during casting of Hg(0.8)Cd(0.2)Te alloys

Su, Ching-Hua↗

NASA NTRS1990

Heat treatment study 2

The microstructural variations in nickel based superalloys that result from modifications in processing were examined. These superalloys include MAR-M246(HF) and PWA1480. Alternate heat treatments for equiaxed as-cast specimens were studied and a sample matrix of 42 variations in the heat treatments were processed, as well as different directional solidification parameters. Variation in temperature and times for both solution and aging were performed. Photomicrographs were made of the microstructure and volume fraction analysis of primary gamma-prime and aged gamma-prime precipitates were performed. The results of the heat treatment, cooling rate, and directional solidification experiments are discussed.

Workman, Gary L.↗

NASA NTRS2011

Apparatus and method for a light direction sensor

The present invention provides a light direction sensor for determining the direction of a light source. The system includes an image sensor; a spacer attached to the image sensor, and a pattern mask attached to said spacer. The pattern mask has a slit pattern that as light passes through the slit pattern it casts a diffraction pattern onto the image sensor. The method operates by receiving a beam of light onto a patterned mask, wherein the patterned mask as a plurality of a slit segments. Then, diffusing the beam of light onto an image sensor and determining the direction of the light source.

Leviton, Douglas B.↗

DOE OSTI2025

3D printing of architected sulfur cathodes with dual-site atomic catalysts for accelerated polysulfide kinetics and Li-ion transport in high areal-loading lithium–sulfur batteries

The practical deployment of lithium–sulfur batteries (LSBs) is hindered by fundamental limitations in conventional slurry-cast cathodes, including poor sulfur utilization, sluggish ion transport, and low areal capacity, particularly in thick electrodes required for high energy density. To address these challenges, we present direct ink writing (DIW) as an additive manufacturing strategy to fabricate advanced current-collector-free, 3D-printed sulfur cathodes (3DP S@CoNi-DSACs/NC) with hierarchically porous architectures that enhance lithium-ion diffusion, promote electrolyte penetration, and reduce interfacial resistance. The synergistic effects of Co/Ni dual-atom sites accelerate redox kinetics and mitigate polysulfide shuttling. As a result, the optimized 3DP cathode with a sulfur loading of 5.4 mg cm −2 demonstrated excellent rate capability, delivering a high reversible capacity of 1041.4 mAh g −1 at 1C with 85.5% capacity retention after 1000 cycles, significantly outperforming its cast counterpart. Remarkably, even at a higher sulfur loading of 8.1 mg cm −2 , the 3DP cathode maintains outstanding performance, achieving a discharge capacity of 1538.4 mAh g −1 and an areal capacity of 12.5 mAh cm −2 at 0.1C. This study not only demonstrates the functional integration of catalytically active materials into 3D printable sulfur cathode architectures but also offers a scalable and transformative platform for building high-performance LSBs beyond conventional electrode manufacturing methods.

3D electrode↗

NASA NTRS1981

Two-dimensional integrating matrices on rectangular grids

The use of integrating matrices in solving differential equations associated with rotating beam configurations is examined. In vibration problems, by expressing the equations of motion of the beam in matrix notation, utilizing the integrating matrix as an operator, and applying the boundary conditions, the spatial dependence is removed from the governing partial differential equations and the resulting ordinary differential equations can be cast into standard eigenvalue form. Integrating matrices are derived based on two dimensional rectangular grids with arbitrary grid spacings allowed in one direction. The derivation of higher dimensional integrating matrices is the initial step in the generalization of the integrating matrix methodology to vibration and stability problems involving plates and shells.

Lakin, W. D.↗

NASA NTRS1992

Experiments with the low melting indium-bismuth alloy system

The following is a laboratory experiment designed to create an interest in and to further understanding of materials science. The primary audience for this material is the junior high school or middle school science student having no previous familiarity with the material, other than some knowledge of temperature and the concepts of atoms, elements, compounds, and chemical reactions. The objective of the experiment is to investigate the indium-bismuth alloy system. Near the eutectic composition, the liquidus is well below the boiling point of water, allowing simple, minimal hazard casting experiments. Such phenomena as metal oxidation, formation of intermetallic compound crystals, and an unusual volume increase during solidification could all be directly observed. A key concept for students to absorb is that properties of an alloy (melting point, mechanical behavior) may not correlate with simple interpolation of properties of the pure components. Discussion of other low melting metals and alloys leads to consideration of environmental and toxicity issues, as well as providing some historical context. Wetting behavior can also be explored.

Krepski, Richard P.↗

DOE OSTI2022

Characterization of Properties of Laser Powder Bed Fusion 3D-Printed Inconel 718 for Centrifugal Turbomachinery Applications

Here, this paper presents the results of a comprehensive effort to characterize the properties of Inconel 718 produced by a form of laser powder bed fusion (LPBF) additive manufacturing (AM) or 3D-printing, subsequently subjected to hot isostatic pressing (HIP) and heat treatment according to standards F3055-14a and AMS 5663, respectively. Material property data, while broadly available for traditional Inconel 718 presentations (e.g. forgings or castings), is currently lacking for the 3D-printed material. It is expected that while limited in size, the experimental data sets presented provide sufficient information to glean the capability of LPBF Inconel 718. These include: 1) Chemical composition, electron backscatter diffraction (EBSD), and x-ray energy dispersive spectroscopy (XEDS) characterization of 3D-printed material structure; 2) Tensile properties — 0.2% yield stress, ultimate stress, modulus of elasticity, and elongation to failure — based on 108 samples, as functions of temperature and sample print orientation; 3) Creep rupture data including the Larson-Miller parameter, based on 21 samples; and 4) High cycle fatigue data based on 21 samples as a function of temperature. Results are compared to available standards and/or data for forged, cast, and other AM Inconel 718. A key observation of this study, based on the EBSD results, is that while the material appears to approach full recrystallization following heat treatment, there is a detectable fraction of the material that does not fully recrystallize, resulting in a material with mechanical properties (e.g. yield stress, creep rupture) measurably lower than those of forgings, but higher than those of castings.

30 DIRECT ENERGY CONVERSION↗