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At least 973 records · Page 54

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NASA NTRS2008

Friction Stir Weld Restart+Reweld Repair Allowables

A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data for initial FSW, confirming no change to the critical flaw size or inspection requirements for the repaired weld. Testing of VPPA fusion/FSW intersection weld specimens exhibited acceptable strength and exceeded the minimum design value. Porosity, when present at the intersection was on the root side toe of the fusion weld, the "worst case" being 0.7 inch long. While such porosity may be removed by sanding, this "worst case" porosity condition was tested "as is" and demonstrated that porosity did not negatively affect the strength of the intersection weld. Large, 15-inch "wide panels" FSW repair welds were tested to demonstrate strength and evaluate residual stresses using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no significant stress gradients due to the presence of the restart and multi-pass FSW repair weld.

Clifton, Andrew↗

NASA NTRS2002

Experimental Study of Characteristics of Micro-Hole Porous Skins for Turbulent Skin Friction Reduction

Characteristics of micro-hole porous skins for the turbulent skin friction reduction technology called the micro-blowing technique (MBT) were assessed experimentally at Mach 0.4 and blowing fractions from zero to 0.005. The objective of this study was to provide guidelines for the selection of porous plates for MBT. The hole angle, pattern, diameter, aspect ratio, and porosity were the parameters considered for this study. The additional effort to angle and stagger the holes was experimentally determined to be unwarranted in terms of skin friction benefit; therefore, these parameters were systematically eliminated from the parametric study. The impact of the remaining three parameters was evaluated by fixing two parameters at the reference values while varying the third parameter. The best hole-diameter Reynolds number was found to be around 400, with an optimum aspect ratio of about 6. The optimum porosity was not conclusively discerned because the range of porosities in the test plates considered was not great enough. However, the porosity was estimated to be about 15 percent or less.

Hwang, Danny P.↗

NASA NTRS2015

Detection of CFRP Composite Manufacturing Defects Using a Guided Wave Approach

NASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered waves are in phase over the overlap boundaries.

Hudson, Tyler B.↗

NASA NTRS2016

Permeability of Two Parachute Fabrics - Measurements, Modeling, and Application

Two parachute fabrics, described by Parachute Industry Specifications PIA-C-7020D Type I and PIA-C-44378D Type I, were tested to obtain their permeabilities in air (i.e., flow-through volume of air per area per time) over the range of differential pressures from 0.146 psf (7 Pa) to 25 psf (1197 Pa). Both fabrics met their specification permeabilities at the standard differential pressure of 0.5 inch of water (2.60 psf, 124 Pa). The permeability results were transformed into an effective porosity for use in calculations related to parachutes. Models were created that related the effective porosity to the unit Reynolds number for each of the fabrics. As an application example, these models were used to calculate the total porosities for two geometrically-equivalent subscale Disk-Gap-Band (DGB) parachutes fabricated from each of the two fabrics, and tested at the same operating conditions in a wind tunnel. Using the calculated total porosities and the results of the wind tunnel tests, the drag coefficient of a geometrically-equivalent full-scale DGB operating on Mars was estimated.

Cruz, Juan R.↗

NASA NTRS2017

Permeability of Two Parachute Fabrics: Measurements, Modeling, and Application

Cruz, Juan R.↗

NASA NTRS2023

Phyllosilicate Decomposition on Bennu Due to Prolonged Surface Exposure

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission to carbonaceous asteroid (101955) Bennu performed detailed mapping with a suite of instruments to characterize the composition and geology of its surface. Here we use data from the OSIRIS-REx Thermal Emission Spectrometer (OTES) instrument to investigate the relationship of OTES-derived spectral indices to other derived data products from OTES, the OSIRIS-REx Camera Suite (OCAMS), and the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS) at global and local scales. We quantitatively confirm that high values of the OTES silicate stretching slope (from ∼10 to ∼12 μm) in midday spectra that are indicative of thin and/or patchy dust cover are strongly associated with low thermal inertia (high porosity), low albedo boulders on Bennu. These high porosity boulders have brecciated textures with embedded clasts that likely originated on Bennu's parent body or during its disruption. The high porosity of these boulders is a key factor in the local production of the dust or its entrapment, as some large, brecciated boulders with a lower porosity have little evidence of dust. A second OTES spectral parameter, the silicate bending band depth near 22.7 μm applied to early evening spectra, is not correlated to thermal inertia, but is weakly to strongly correlated to albedo, OVIRS-derived 1.05 μm and 2.74 μm band depths, OVIRS-derived hydrogen abundance, and modeled nanophase troilite abundance. In several regions on Bennu there is a strong spatial relationship between these parameters, whereby areas with shallower silicate bending bands also have shallower 1.05 μm and 2.74 μm bands and lower albedo with higher nanophase troilite abundances. These correlations, combined with analysis of the silicate bending band in laboratory experiments of space weathered and mildly heated carbonaceous chondrites, suggests that decreased silicate bending band depths signify decomposition of phyllosilicates, likely Fe-bearing, due to space weathering or mild heating (<600 °C) via solar radiation during Bennu's time in near-Earth space. There is a strong association of larger silicate bending band depths in areas dominated by small rocks and unresolved material and in areas with small (≤ 25 m) craters identified as the spectrally reddest on Bennu, suggesting that this material has been more recently exposed due to impact and/or mass wasting processes. The shallowest silicate bending depths are associated with larger rocks and boulders that appear to have the longest surface exposure history, although there is band depth variation among them suggesting either initial composition variation that resulted in different responses to space weathering or heating, or varied exposure history of individual boulders themselves. We predict that any grains returned from Bennu with a significant surface exposure history will be characterized by shallower 22.7 μm, 1.05 μm and 2.7 μm band depths and increased sulfide (troilite) abundance, as well as textural and chemical evidence for phyllosilicate dehydration.

Asteroids, surfaces↗

NASA NTRS2024

Subsurface Thermophysical Properties of Europa's Leading and Trailing Hemispheres as Revealed by ALMA

We present best-fit values of porosity—and the corresponding effective thermal inertiae—determined from three different depths in Europa's near-subsurface (∼1–20 cm). The porosity of the upper ∼20 cm of Europa's subsurface varies between 75% and 50% (Γeff ≈ 50–140 J m −2 K −1 s −1/2 ) on the leading hemisphere and 50%–40% (Γeff ≈ 140–180 J m −2 K −1 s −1/2 ) on the trailing hemisphere. Residual maps produced by comparison with these models reveal thermally anomalous features that cannot be reproduced by globally homogeneous porosity models. These regions are compared to Europa's surface terrain and known compositional variations. We find that some instances of warm thermal anomalies are co-located with known geographical or compositional features on both the leading and trailing hemisphere; cool temperature anomalies are well correlated with surfaces previously observed to contain pure, crystalline water ice and the expansive rays of Pwyll crater. Anomalous regions correspond to locations with subsurface properties different from those of our best-fit models, such as potentially elevated thermal inertia, decreased emissivity, or more porous regolith. We also find that ALMA observations at ∼3 mm sound below the thermal skin depth of Europa (∼10–15 cm) for a range of porosity values, and thus do not exhibit features indicative of diurnal variability or residuals similar to other frequency bands. Future observations of Europa at higher angular resolution may reveal additional locations of variable subsurface thermophysical properties, while those at other wavelengths will inform our understanding of the regolith compaction length and the effects of external processes on the shallow subsurface.

Alexander E Thelen↗

DOE OSTI2018

Selective, electrochemical etching of a semiconductor

Methods for facilitating fabricating semiconductor structures are provided which include: providing a multilayer structure including a semiconductor layer, the semiconductor layer including a dopant and having an increased conductivity; selectively increasing, using electrochemical processing, porosity of the semiconductor layer, at least in part, the selectively increasing porosity utilizing the increased conductivity of the semiconductor layer; and removing, at least in part, the semiconductor layer with the selectively increased porosity from the multilayer structure. By way of example, the selectively increasing porosity may include selectively, anodically oxidizing, at least in part, the semiconductor layer of the multilayer structure.

42 ENGINEERING↗

DOE OSTI2019

Subtask 1.1 – Advanced Characterization of Unconventional Oil and Gas Reservoirs to Enhance CO2 Storage Resource Estimates

The Energy & Environmental Research Center (EERC) developed methods and approaches for advanced characterization of unconventional oil and gas reservoirs to enhance CO2 storage resource estimates using samples collected from organic-rich shales of the Bakken Formation. The project was funded under U.S. Department of Energy (DOE) Cooperative Agreement No. DE-FE0024233, with nonfederal cost share provided by Hitachi High Technologies America. The project participants included the EERC, Hitachi High Technologies America, the team at the National Energy Technology Laboratory’s (NETL’s) computed tomography (CT) scanning laboratory in Morgantown, West Virginia, and several NETL staff who have worked on CO2 storage resource estimation. Investigations on the use of subsurface geologic formations for CO2 storage have been ongoing for many years. In the last decade, improvements in directional drilling technology and hydraulic fracturing of organic-rich shale and other tight rock formations have opened new opportunities for CO2 storage, with the potential cobenefit of enhancing gas and oil recovery. Gas-bearing, organic-rich shales have been of particular interest as a carbon storage target because their ability to store large volumes of CO2 is implied by their ability to store methane; however, estimating the CO2 storage resource of organic-rich shales and other unconventional reservoirs is challenging because of the lack of detailed geologic and petrophysical data that are needed to develop improved volumetric equations. According to NETL’s method for estimating regional-scale CO2 storage resources, the key factors that control CO2 storage in geologic formations include void space within induced fractures, natural fractures and matrix pores, as well as the occurrence and distribution of organic matter (OM) and clay minerals. A key goal of this effort was to use field emission scanning electron microscopy (FESEM) analysis of fine-grain unconventional reservoir rocks coupled with advanced image analysis and machine learning techniques to quantify the occurrence and distribution of porosity, OM, and clay minerals. By better understanding the potential migration pathways of CO2 within tight rocks and quantifying the occurrence of sorptive components (OM and clays) along potential flow pathways, methods to estimate the CO2 storage resource of such rocks can be refined. The Bakken petroleum system (Bakken) was used as the source of rock samples for this effort because it includes organic-rich shales with contrasting degrees of thermal maturity as well as tight, nonshale clastic rocks with varying clay mineral content. To better understand the key components of interest in tight rock samples, the EERC worked closely with Hitachi to optimize the FESEM settings necessary to resolve the sample mineralogy, porosity and OM content at micro- to nanoscale resolution. The EERC also worked closely with Hitachi to apply and improve its advanced mineral identification and characterization system (AMICS) software so that it is better suited for mineral identification at the high resolution necessary to resolve features of interest in fine-grained rocks such as organic-rich shales. The EERC also applied advanced image analysis software packages, including Ilastik, to classify and quantify the key components of interest within the samples using FESEM imagery. These advanced techniques allowed for quantification and differentiation of the void space within fractures, pores and OM, as well as a technique to determine and quantify the key mineral and OM components surrounding pore spaces. Being able to better quantify the void space and the potential accessibility of CO2 to sorptive minerals or OM within tight rocks allows for improved estimation of the CO2 storage resource potential of organic-rich shales and other unconventional formations. The information derived from the image analysis techniques was used to refine NETL’s method for estimating regional-scale CO2 storage resources in collaboration with staff from NETL. An additional goal of this work was to better understand rates of CO2 permeation, flow pathways, and sorption in organic-rich shales and nonshale reservoir rocks and to evaluate potential changes in CO2 flow over time. The EERC conducted long-duration (several weeks) CO2 flow-through testing at reservoir conditions using Bakken shale and nonshale samples to assess CO2 permeation rates and retention/sorption within core plugs to represent bulk matrix behavior. Conventional isothermal adsorption testing over a range of pressure conditions was also performed on pulverized Bakken samples to better assess potential maximum sorptive capacity of the samples. The results of this testing illustrated the higher sorptive capacity of the Bakken shales when compared to the sorptive capacity of the nonshale reservoir rock, which contains very little OM when compared to the Bakken shales. The results also illustrate the differences in permeation behavior as a function of fracture flow versus matrix flow. In an attempt to visualize CO2 permeation and flow behavior in Bakken shale samples over time, the EERC collaborated with NETL’s CT Lab in Morgantown, West Virginia. A variety of tests were performed at the NETL lab on unfractured and fractured samples of the Bakken shale. The unfractured Bakken shale samples did not result in CO2 migration within the samples over the testing duration; thus imagery of CO2 migration pathways within the matrix of Bakken samples was not obtained. The results of the flow-through testing within fractured samples illustrate changes in CO2 permeation rates over time, with a trend of decreasing CO2 flow over time. The results of this effort suggest that FESEM analysis coupled with advanced image analysis and machine learning techniques are effective in characterizing and quantifying the mineralogy, porosity, fractures, and OM content of 2-D imagery at the high resolution needed to identify features of interest in tight rocks. In addition, the image analysis techniques allow for identification and quantification of different porosity types as well as the key mineral components and/or OM that CO2 would contact in the reservoir as it migrates through pores and fracture networks. This is key information needed to better estimate the CO2 storage resource potential of organic-rich shales and other tight reservoirs. Additional work is needed to determine the sorptive capacity of the individual sample components (OM and clay minerals) at reservoir conditions so that this approach and the refined CO2 storage resource equation can be applied to other shale and unconventional reservoirs. In addition, subsequent work should be performed to better understand the number of images needed to use stereological approaches to estimate the volume of sample components using 2-D imagery, to explore machine learning techniques to differentiate between induced vs. natural fractures, and to estimate the connectivity of pores and fracture networks using 2-D imagery. Being able to derive this information at the microscale would facilitate scaling up of the sample characterization data used for reservoir modeling and simulation to estimate the CO2 storage resource potential of tight formations.

03 NATURAL GAS↗

DOE OSTI2020

Petrophysical and geomechanical properties of gas hydrate-bearing sediments recovered from Alaska North Slope 2018 Hydrate-01 Stratigraphic Test Well

Knowledge of petrophysical and geomechanical properties of gas hydrate-bearing sediments are essential for predicting reservoir response due to gas production from gas hydrate reservoirs. That information will be critical parameters for designing production well completion such as specification of depressurization pump, water storage tank, and mesh size of sand screen. In December 2018, Stratigraphic Test Well Hydrate-01 was drilled in the western part of the Prudhoe Bay Unit, Alaska North Slope as part of the technical planning effort for a future long-term production test by collaborative team of DOE/NETL, USGS, and MH21-S (Boswell et al., 2020, Collett et al., 2020, Okinaka et al., 2020). Data set of logging-while-drilling (LWD) were acquired (Haines et al., 2020, Suzuki et al., 2019) and core sampling depth was determined on-site.Side-wall pressure coring was conducted to recover gas hydrate-bearing sediments from two reservoir sections named Unit-B and Unit-D. A total of 34 cores were successfully recovered by 5 runs of a wire-line deployed pressure corer (CoreVault® System - Halliburton). Core analysis scheme of this project are shown in Figure 1. All cores were quenched in liquid nitrogen while at high pressure in the laboratory of Stratum Reservoir, LLC. at Anchorage (Figure 1, a)). And the cores were removed from the pressure corer autoclave with temperature support of dry ice and stored under liquid nitrogen at atmospheric pressure. 19 damaged cores were processed to index property measurements directly such as grain size, grain density. 4 of another 17 cores were depressurized and trimmed for making a plug to analyze petrophysical properties of host sediments. Unsteady-state permeability test was conducted to obtain relative water permeability to gas and core scale NMR T2 distribution measurement was performed for evaluating pore size distribution at Houston (Figure 1, b)). Remained high quality 13 cores were preserved with gas hydrate for advanced laboratory analysis. National Institute of Advanced Industrial Science and Technology, as a part of the Japanese National Hydrate Research Program (MH21-S, funded by Ministry of Economy, Trade and Industry), received the samples at Sapporo, Japan for advanced core analysis. High-resolution X-ray CT was used to analyze the quality of the samples, which showed undisturbed lithological layers. Cores were lathed into cylindrical shape and distributed for multi property measurements (Figure 1, c)).<p>As a result, sediment from Unit-D is categorized as silty sand at ~37% porosity with ~80% gas hydrate saturation. An average hydration number n = 6.16 was measured by Raman spectroscopy. An average intrinsic permeability of ~400 mD and in situ effective permeability (with hydrate) on the order of ~10 mD. The Unit B recovered cores consisted of well sorted sand at ~40% porosity with ~95% gas hydrate saturation. An average intrinsic permeability of ~1 Darcy and in situ effective permeability on the order of ~30 mD was measured for the Unit B cores. There was a small permeability reduction due to porosity loss with increasing effective stress that simulated consolidation behavior along with depressurization in the highly permeable sandy sediment. The apparent minimum change in porosity and permeability may be caused by the low compressibility of quartz sand grains in the recovered cores. XRD and thermal conductivity analysis also suggested high quartz content. Triaxial compression tests established internal friction angles based on the Mohr-Coulomb's failure criterion, which are 40° for hydrate-bearing sediment and 29.8° for hydrate free sediment.</p>

Yoneda, Jun↗

DOE OSTI2021

Compressed Expanded Natural Graphite (CENG) Processing for PCM Composites

The use of phase change materials (PCMs) in thermal energy storage applications has received considerable attention in recent decades. Organic PCMs are popular due to their high latent heat of fusion, noncorrosive properties, and relative stability over many charge and discharge cycles. A primary limitation of these materials is their low thermal conductivity. This has led researchers to develop various methods to increase thermal conductivity by seeding PCM with or impregnating them into more conductive materials. One method is to impregnate PCMs into compressed expanded natural graphite (CENG) matrices, which can improve thermal conductivity by a factor of 100. CENG matrices have received particular interest due to their low cost, high porosity, small (nano/micro) pore size, high pore density, high thermal conductivity, and ability to be compressed into many geometries. PCM/CENG matrix composites have been extensively studied; however, the effect that CENG processing has on PCM saturation and the overall matrix thermal conductivity has not been well investigated. This processing includes four major steps including graphite intercalation, thermal shock, compression, and PCM saturation. Intercalation involves soaking graphite flakes in sulfuric and/or nitric acid to intercalate the acids between the graphene layers. The graphite flakes are then subjected to a high-temperature thermal shock, during which the intercalated acid is gasified rapidly, pushing the graphene layers apart, resulting in accordion-shaped graphite "worms". The "worms" are then compacted to a desired bulk density and then soaked with molten PCM until fully saturated. The properties of the produced CENG matrix, and its ability to allow PCM permeation, are sensitive to the processing parameters, namely, the thermal shock temperature and exposure time, as well as the matrix apparent density or porosity. Here, we study the effect of the thermal shock conditions necessary to expand intercalated graphite flakes on PCM saturation and the expanded graphite's thermal conductivity and morphology. We found that the thermal shock temperature exhibits the greatest influence. At greater shock temperatures, SEM images showed that expanded graphite worms exhibited greater density of pores, thus increasing total surface area within the matrices. Increasing thermal shock temperature yielded greater overall PCM saturation, as well as an increased rate of saturation. Improvements in PCM saturation rate and overall saturation are obtained as the shock temperature is increased. Longer exposure to thermal shock also improves initial saturation rates and is beneficial if a shortened impregnation time is needed. Thermal shock conditions did not impact thermal conductivity; however, conductivity was largely affected by matrix porosity. A local maximum in axial thermal conductivity was observed at around 83% porosity, which is similar to that observed in previous studies.

compressed expanded natural graphite↗

DOE OSTI2016

Investigation and modeling of the degradation of Zr-based fuel claddings during corrosion in steam and air-steam mixtures at high temperatures - 6.3 STP-2016-0033

This paper presents the main results of a study conducted to quantify and to model the degradation state of Zr-based fuel claddings submitted to severe accident conditions in a nuclear reactor core: high temperatures and either pure steam or air-steam mixture. Due to the progressive thickening of a dense and protective ZrO{sub 2} layer, the oxidation kinetics of Zr-based claddings in steam at high temperatures typical of nuclear severe accidents, is generally cubic or parabolic. However, for some temperature domains, this oxide layer may crack, becoming porous and non-protective anymore. In these 'breakaway' conditions, the oxidation kinetics change from (sub-)parabolic to linear or even accelerated. Additionally, the temperature increase can lead core materials to melt and to relocate down to the vessel lower head, threatening its integrity. If it fails, and for specific conditions, air ingress may take place into the reactor. Hence, oxygen and nitrogen both react with Zr-based claddings, successively through oxidation of Zr (forming ZrO{sub 2} layer), nitriding of Zr (forming ZrN particles) and oxidation of ZrN (forming ZrO{sub 2} and releasing nitrogen). These self-sustained chemical reactions enhance the deterioration of Zr-based claddings and of their ZrO{sub 2} layers, inducing a rise of their open porosity. To quantify this porosity, a series of two-step experiments was conducted. First, Zirlo{sup TM} cladding samples were isothermally oxidized in various conditions: in pure steam or in 50- 50 mol% air-steam mix, at several temperatures, and for different durations. The main thermal effects on reaction kinetics and the high impact of air on the cladding degradation are all confirmed by experimental results. Second, pioneering porosimetry measurements by Hg intrusion were realized for the first time on such corroded cladding samples. In both atmospheres, it is pointed out that 1200 and 1250 K lead to particularly porous oxide layers, especially due to strong 'breakaway' effects. Moreover, it is confirmed that the presence of air strongly enhances the oxide cracking: cladding samples are more porous when oxidized in the air-steam mixture than under pure steam. Finally, it is observed that in all conditions, the open porous volume fraction of Zirlo{sup TM} claddings continuously rises during their corrosion process. Hence, for each experimental condition, porosity correlations are determined through linear regressions, and porosity increase rates are deduced by derivation versus time and validated against porosimetry results of cladding samples corroded in transient (nonisothermal) conditions. (authors)

36 MATERIALS SCIENCE↗

NASA NTRSDate not supplied

Flash Thermal Diffusivity Measurements and Inspection of Additively Manufactured Ti-6Al-4V Specimens with Varying Process Parameters

Flash thermal diffusivity measurements were obtained on additively manufactured Ti-6Al-4V disk shaped specimens with various process parameters. For additively manufactured metal parts, processing parameters such as laser power and scanning speed are critical to ensure the desired microstructure. For this study, the laser powder bed fusion process parameters were changed at various angular sections on a 21 mm diameter and 3.0 mm thick disk. The measurement of thermal diffusivity was performed by fitting a 1-dimensional thermal model to the data pixel by pixel to produce an inspection image. The image revealed the detection of defects such as lack of fusion porosity and areas of aggregated porosity. The thermal diffusivity imagery was compared to immersion scan ultrasonic and X-ray computed tomography (CT) measurements for validation. Based on these results, additional samples were investigated using a single side thermal inspection technique to detect lack of fusion porosity and near surface voids.

thermal nondestructive evaluation↗

NASA NTRS2023

Flash Thermal Diffusivity Measurements and Inspection of Additively Manufactured Ti-6Al-4V Specimens with Varying Process Parameters

thermal nondestructive evaluation↗

DOE OSTI2017

Investigation of the Mechanical Properties of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} Added with Nanosized Ferrites ZnFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} Using Ultrasonic Measurement

Recently, there is much interest in studying the effect of nanosized ferrites addition on high- T{sub c} superconductors. However, little information is available on the mechanical properties. We have investigated the effect of (CoFe{sub 2}O{sub 4}){sub x} and (ZnFe{sub 2}O{sub 4}){sub x} nanosized ferrites with 0.01 ≤ x ≤ 0.40 on the mechanical properties of the high- T{sub c} superconducting compound GdBa{sub 2}Cu{sub 3}O{sub 7−δ} (Gd-123) prepared by the conventional solid-state reaction technique. Elastic parameters including shear modulus (G), bulk modulus (B), and Young’s modulus (E) of all samples were inspected using ultrasonic measurements and compared with Vickers microhardness results. Furthermore, the porosity of the samples was investigated and correlated to Young’s modulus, which was corrected to zero porosity using different models. The corrected values were correlated with Vickers microhardness. Moreover, the Debye temperature (θ{sub D}) and the electron-phonon coupling factor (λ) were also determined as a function of x. We observed that the different nanoparticles addition has influenced the Gd-123 compound differently. For (ZnFe{sub 2}O{sub 4}){sub x} added samples, the mechanical properties and Debye temperature improved up to x = 0.06, then deteriorated with further addition. However, (CoFe{sub 2}O{sub 4}){sub x} addition improved the mechanical properties for all samples with x up to 0.40. We found that the proportionality constant between the corrected values of E and H{sub v} and G and H{sub v} are strongly dependent on the porosity corrections and the kind of superconducting material. This indicates that the widely used formula E = 81.96 H{sub v} may not be valid for all types of superconducting materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Quantitative Analysis of Micro-structural Changes in a Bituminous Coal After Exposure to Supercritical CO{sub 2} and Water

High-volatile bituminous coal samples were reacted in deionized water with supercritical CO{sub 2} (ScCO{sub 2}–water) under simulated in situ pressure and temperature conditions (8 MPa and 40 °C) in unconfined stress state for 14 days, in order to characterize potential CO{sub 2}–water–coal reactions. Micro-structural changes were identified pre- and post-experiment using X-ray powder diffraction (XRD) analysis for powdered coal (mineralogical changes), optical microscopy and scanning electron microscopy (SEM) for polished thin sections (surface feature changes) and micro-CT scanning for a small core (porosity and permeability changes). XRD analysis revealed that carbonic acid leaches out mineral matters in coal, including carbonates (calcite) and silicate minerals (albite, illite and kaolinite). Optical microscopy, SEM and CT images confirmed that the interaction of coal with ScCO{sub 2}–water causes an abundance of micro-cracks to open or propagate in unconfined coal samples. Most micro-cracks preferably propagated along maceral–mineral and maceral–maceral interfaces, which demonstrates that the micro-cracking was caused by differential swelling of different coal lithotypes. Wormhole formation was observed in coal caused by mineral dissolution and hydrocarbon mobilization, which significantly increases coal porosity compared with swelling-induced cracking. 3-D pore network models extracted from CT images show that ScCO{sub 2}–water treatment enlarges the pore and throat size, increases the numbers of pores and throats and improves pore network connectivity. Overall, CO{sub 2}–water–coal interactions under unconfined conditions enhance coal porosity, connectivity and permeability, which can be attributed to the combined effect of micro-cracking, mineral dissolution and hydrocarbon mobilization.

58 GEOSCIENCES↗

DOE OSTI2019

Studies on Highly Fluxed Iron Ore Pellets Hardened at 1100 °C to 1200 °C

The behaviors of highly fluxed (basicity 2, 4, 6, and 8) iron ore pellets heat hardened in the temperature range 1100 °C to 1200 °C were examined and are reported here. The highly fluxed (basicity 8) pellets exhibited 103 kg/pellet crushing strength and 43.65 pct porosity when heat hardened at 1180 °C. During heat hardening, calcium di-ferrite and calcium ferrite phases were observed; however, when they were heated at 1200 °C, high crushing strength (458.63 kg/pellet) with low porosity (4.57 pct) were noted due to low melting eutectic formation. In this study, it was possible to prepare highly fluxed pellets without sticking at 1180 °C with good strength and porosity.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Porous Titanium Parts Fabricated by Sintering of TiH{sub 2} and Ti Powder Mixtures

A new simple powder metallurgy process by sintering TiH{sub 2} powders was used to manufacture porous Ti components. The effects of the processing parameters (pressure of cold isostatic pressing and sintering temperature) and the TiH{sub 2}/Ti ratio in the powder mixtures on the impurities, the linear shrinkage and the pore properties (including overall and open porosities) were comprehensively determined. The addition of TiH{sub 2} as a reactant has been found beneficial for the synthesis of porous Ti components. The formation mechanisms of pores were demonstrated based on the dehydrogenation process of TiH{sub 2} during sintering, resulting in highest reactivity due to the “in statu nascendi” generation of the metal. In addition, the hardness and corrosion resistance of all the sintered samples were evaluated, related to the overall and open porosities. As a result, an optimal composition of Ti-40 wt.% TiH{sub 2} was defined, as its maximum open porosity was about 23%.

36 MATERIALS SCIENCE↗