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Results for “POROSITY”

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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Microstructural modification of a high-pressure die-cast A380 alloy through friction stir processing and its effect on mechanical properties

Aluminum alloy A380 is one of the major high-pressure die-cast (HPDC) alloys fabricated in the die casting sector. However, microstructural features such as shrinkage and gas porosity, entrapped oxide inclusions, change in the morphology of eutectic Si particles as a function of casting location, and the presence of multiple second phase particulates, especially Fe-bearing phases in HPDC A380 alloy results in limited ductility, thus, affecting its structural application. However, through proper modification of the as-cast microstructure, it is possible to improve the mechanical performance of alloy A380. In this study, we report the effect of friction stir processing (FSP), a well-known severe plastic deformation (SPD) and thermomechanical processing tool for selective microstructural modification, on A380. FSP effectively refines the as-cast microstructure and breaks down the coarse Si particles, creating a homogenized distribution of equiaxed Si particles in the aluminum matrix. Additionally, FSP eliminates porosity that acts as crack initiation sites, leading to improved mechanical strength and ductility.

Friction stir processing, Aluminum alloys, Mechani↗
DOE OSTI2022

Understanding the role of segmentation on process-structure–property predictions made via machine learning

Here, the present study investigated the effect of porosity surface determination methods on performance of machine learning models used to predict the tensile properties of AlSi10Mg processed by laser powder bed fusion from micro-computed tomography data. Machine learning models applied in this work include support vector machines, neural networks, decision trees, and Bayesian classifiers. The effects of isosurface thresholding and local gradient approaches for porosity segmentation, as well as image filtering schemes, on model precision were evaluated for samples produced under differing levels of global energy density.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Stratigraphic and structural controls on groundwater flow in an outcropping fossil fan delta: the case of Sant Llorenç del Munt range (NE Spain)

Hydrogeological models of mountain regions present the opportunity to understand the role of geological factors on groundwater resources. The effects of sedimentary facies and fracture distribution on groundwater flow and resource exploitation studied in the ancient fan delta of Sant Llorenç de Munt (central Catalonia, Spain) by integrating geological field observations (using sequence stratigraphy methods) and hydrogeological data (pumping tests, hydrochemistry and environmental isotopes). A comprehensive analysis of data portrays the massif as a single unit, constituted by different compartments determined by specific layers and sets of fractures. Two distinct flow systems—local and regional—are identified based on pumping test analysis as well as hydrochemical and isotopic data. Drawdown curves derived from pumping tests indicate that the behavior of the saturated layers, whose main porosity is given by the fracture network, corresponds to a confined aquifer. Pumping tests also reflect a double porosity within the system and the occurrence of impervious boundaries that support a compartmentalized model for the whole aquifer system. Hydrochemical data and associated spatial evolution show the result of water–rock interaction along the flow lines. Concentration of magnesium, derived from dolomite dissolution, is a tracer of the flow-path along distinct stratigraphic units. Water stable isotopes indicate that evaporation (near a 5% loss) occurs in a thick unsaturated zone within the massif before infiltration reaches the water table. The hydrogeological analysis of this outcropping system provides a methodology for the conceptualization of groundwater flow in similar buried systems where logging and hydrogeological information are scarce.

58 GEOSCIENCES↗
DOE OSTI2018

Review: The distribution, flow, and quality of Grand Canyon Springs, Arizona (USA)

An understanding of the hydrogeology of Grand Canyon National Park (GRCA) in northern Arizona, USA, is critical for future resource protection. The ~750 springs in GRCA provide both perennial and seasonal flow to numerous desert streams, drinking water to wildlife and visitors in an otherwise arid environment, and habitat for rare, endemic and threatened species. Spring behavior and flow patterns represent local and regional patterns in aquifer recharge, reflect the geologic structure and stratigraphy, and are indicators of the overall biotic health of the canyon. These springs, however, are subject to pressures from water supply development, changes in recharge from forest fires and other land management activities, and potential contamination. Roaring Springs is the sole water supply for residents and visitors (>6 million/year), and all springs support valuable riparian habitats with very high species diversity. Most springs flow from the karstic Redwall-Muav aquifer and show seasonal patterns in flow and water chemistry indicative of variable aquifer porosities, including conduit flow. They have Ca/Mg-HCO{sub 3} dominated chemistry and trace elements consistent with nearby deep wells drilled into the Redwall-Muav aquifer. Tracer techniques and water-age dating indicate a wide range of residence times for many springs, supporting the concept of multiple porosities. A perched aquifer produces small springs which issue from the contacts between sandstone and shale units, with variable groundwater residence times. Stable isotope data suggest both an elevational and seasonal difference in recharge between North and South Rim springs. This review highlights the complex nature of the groundwater system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Statistical scaling of geometric characteristics in stochastically generated pore microstructures

In this study, we analyze the statistical scaling of structural attributes of virtual porous microstructures that are stochastically generated by thresholding Gaussian random fields. Characterization of the extent at which randomly generated pore spaces can be considered as representative of a particular rock sample depends on the metrics employed to compare the virtual sample against its physical counterpart. Typically, comparisons against features and/patterns of geometric observables, e.g., porosity and specific surface area, flow-related macroscopic parameters, e.g., permeability, or autocorrelation functions are used to assess the representativeness of a virtual sample, and thereby the quality of the generation method. Here, we rely on manifestations of statistical scaling of geometric observables which were recently observed in real millimeter scale rock samples [13] as additional relevant metrics by which to characterize a virtual sample. We explore the statistical scaling of two geometric observables, namely porosity (Φ) and specific surface area (SSA), of porous microstructures generated using the method of Smolarkiewicz and Winter [42] and Hyman and Winter [22]. Our results suggest that the method can produce virtual pore space samples displaying the symptoms of statistical scaling observed in real rock samples. Order q sample structure functions (statistical moments of absolute increments) of Φ and SSA scale as a power of the separation distance (lag) over a range of lags, and extended self-similarity (linear relationship between log structure functions of successive orders) appears to be an intrinsic property of the generated media. The width of the range of lags where power-law scaling is observed and the Hurst coefficient associated with the variables we consider can be controlled by the generation parameters of the method.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

End-Of-Life Textiles as Reinforcements in Biocomposites

A number of attempts have been made to recycle cotton/polyester blend woven fabrics after use; however, most of these fabrics are disposed of in landfills. Major part of these blend fabrics are not recycled due to complexity of the fibre arrangement and cannot be separated economically. This study shows that these discarded woven fabrics could be directly used as reinforcements in composites without fibre separation. Uniform alignment in the woven fabric provided consistent properties to the composites. The fabrics were reinforced by soybean-based-bioresins to produce biocomposites. The composites were analysed for mechanical, thermal, viscoelastic and morphological properties. Porosity and wettability of the composites were also evaluated. Results demonstrate that the tensile strength and modulus of over 100 and 10 MPa, respectively, can be obtained without any fibre treatment. Furthermore, impact strength over 70 kJ/m{sup 2} was obtained without any chemical treatment on fibres. The porosity of the composites produced was less than 9 vol%. Additionally, the fabrics were treated with alkali in order to improve the fibre–matrix interface and the composite properties were studied. From the economical perspective, these composites can be produced at a low cost as the major component is available for free or low cost.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnetic Mesocellular Foam Functionalized by Curcumin for Potential Multifunctional Therapeutics

The study investigates curcumin/SPIONs hybridized mesocellular foam type silica for potential dual purpose of drug delivery (curcumin) and magnetic resonance imaging. Magnetization capability and curcumin release was assessed for different structured silica such as spherical silica (Q-10), Si-MCM-41, Si-SBA-16, mesocellular foam (MSU-Foam), Si-KIT-6, ULPFDU-12, and silicalite. The phase, textural, and morphological variation was systematically scrutinized using various physico-chemical techniques. Ten weight percent SPIONs loading was found to generate magnetically active SPIONs in the following order: Q-10 (1.44 emu/g) > SBA-16 (0.80 emu/g) > MSU-Foam (0.24 emu/g) > Si-MCM-41 (0.07 emu/g) > Si-KIT-6 (0.07 emu/g) > silicalite (0.08 emu/g), respectively. The iron oxide dispersion, specific surface area, and porosity play a major role in various structured silicas. MSU-Foam with wormhole structure showed highest specific surface area occupation of SPIONs (73%). The presence of interconnected porosity of foam tends to generate external agglomeration of SPIONs (7–18 nm) at the pore surface contributing to expansion of pore sizes from 16.4 to 40.2 nm. The SPIONs over spherical micron-sized silica Q-10 showed the formation of large nanoclusters (10–25 nm). Thirty to 390 μg/ml of curcumin was loaded over silica and SPIONs/silica structured hybrid, and drug release was studied at pH 5.6 for 72 h. SPIONs/MSU-Foam with less magnetization showed the highest cumulative curcumin release (53.2%), while Q-10 spherical silica with high magnetization property showed less cumulative release of curcumin (12%).

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Prospect Analysis and Hydrocarbon Reservoir Volume Estimation in an Exploration Field, Shallow Offshore Depobelt, Western Niger Delta, Nigeria

The daunting challenge in the exploration and production of oil and gas in the face of continual rise in the world’s energy consumption has long been how to economically recover bypassed reserves within existing assets. This research is focused on the analysis of prospects and volumetric estimation of the hydrocarbon reservoirs delineated within an exploratory field using 3D seismic data and suites of wireline logs. The prospectivity of the delineated reservoir was carried out using seismo-structural interpretation and formation evaluation towards the assessment of the prolific hydrocarbon occurrence within the field. The reservoirs have porosity (0.29–0.32) for H1, (0.20–0.31) for H2 and (0.30–0.40) for H3 and the average computed hydrocarbon saturation of (0.31–0.62) for H1, (0.16–0.52) for H2 and (0.64–0.73) for H3, hydrocarbon pore volume (HCPV) of 28,706.95, 33,081.2 and 45,731.49 barrels for H1, H2 and H3, respectively, while the estimated stock tank oil initially-in-place (STOIIP) range (136.8–140.73) MMSTB for H1, (36.77–489.64) MMSTB for H2 and (166.62–308.14) MMSTB for H3. The observed porosity and hydrocarbon saturation for the delineated reservoirs as well as the estimated hydrocarbon pore volume and storage total oil in place indicate that the reservoirs are highly prolific. The study has therefore contributed to the understanding of hydrocarbon resource potential within the study area.

58 GEOSCIENCES↗
DOE OSTI2018

Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of Structure and Mineral Association of Tuyere-Level Coke on Gasification Process

The gasification properties of feed coke and tuyere coke were investigated by non-isothermal thermogravimetric method under CO{sub 2} atmosphere. The physical and chemical structure features were also systematically tested, as well as the mineral composition. The pore characteristics, graphitization degree of carbon matrix, and ash content were the main factors determining the reactivity of coke. Higher L{sub c} decreases the reactivity of tuyere coke in low temperature, while larger porosity increases the reactivity in high temperature, forming an intersection with the gasification process of the feed coke. The high content of Fe{sub 2}O{sub 3} in 25 to 20 mm tuyere coke made a rapid gasification reaction. The SiC produced in the tuyere area increased the porosity of coke especially the 5 to 1 mm coke at the edge of BF, which promoted the gasification process of coke in the area.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Diffusion and Flow of CO{sub 2} in Carbon Anode for Aluminium Smelting

Using a well-made carbon anode with the right porosity characteristics is essential to the successful operation of a Hall–Héroult cell. Bubble generation at this carbon anode and its contribution to the overall voltage drop in aluminum production holds significant potential for reducing overpotential and improving energy savings. This voltage drop is believed to be greatly influenced by the gas diffusion in the anode carbon, for which there are a limited number of measurements to correlate with the carbon anode properties. In the present study, the CO{sub 2} gas diffusion characteristics were first investigated via measuring anode porosity using mercury intrusion porosimetry (MIP) for different samples with different permeability. Second, diffusion experiments were conducted by flowing CO{sub 2} gas into the anode sample at elevated temperatures (up to 960 °C). The impact of temperature, average pore size, and permeability on the diffusion coefficient was investigated. The diffusion coefficient was consequently calculated by curve fitting using diffusion theories. The value obtained varied from 1.38 × 10{sup −6} to 7.89 × 10{sup −6} m{sup 2}/s. A high diffusion coefficient was measured in the carbon sample with larger average pore size and higher permeability. It was found that anomalous diffusion behavior in the temperature range 600 °C to 960 °C was caused by convective flow effects, different diffusion mechanisms, and the Boudouard reaction for these carbon anode samples. Furthermore, by plotting the measured diffusion coefficient against average pore size and permeability, an increasing trend of diffusivity with an increase in pore size and permeability was observed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure and Mechanical Properties of W-ZrC Composites Synthesized by Reactive Melt Infiltration of Zr{sub 2}Cu into Porous Preforms from Partially Carburized W Powders

W-ZrC composites with different W contents from 48 to 73 vol.% have been synthesized by reactive melt infiltration of Zr{sub 2}Cu melt into porous preforms from partially carburized W powders at 1300 °C for 1 h in vacuum. The influences of carbon content and porosity in the preforms on microstructure and mechanical properties of W-ZrC composites are investigated. Cold isostatic pressing followed by pre-sintering process is used to produce porous preforms with suitable porosities of 53.6-47% under a pressure of 100 MPa to allow sufficient penetration of Zr{sub 2}Cu melt into the preforms. Small amounts of Cu-rich phases form in the synthesized W-ZrC composites after a complete reaction of y/2xZr{sub 2}Cu(l) + WC{sub y}(s) = y/xZrC{sub x}(s) + W(s) + y/2xCu(l). These Cu-rich phases are distributed not only at the phase boundaries of W matrix and ZrC grains, but also in the interior of ZrC{sub x} grains. With decreasing W content from 73 to 48 vol.% in the W-ZrC composites, the flexural strength and fracture toughness increase from 519 to 657 MPa and from 9.1 to 10.6 MPa m{sup 1/2}, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Deformation Behavior and Microstructure Evolution of Powder Metallurgy Ti6Al4V Alloy During Hot Compression

In order to determine appropriate workability parameters for cross-wedge rolling products of powder metallurgy (PM) Ti6Al4V alloys, thermal compression experiments were carried out within the temperature range of 850-1050 °C, the strain rate range of 0.1-10 s{sup −1}, and with a height decrease of 60%. The compression deformation behavior was investigated. A strain-compensated constitutive model was established based on the flow stress curves corrected by the friction, which can predict the flow behaviors under the entirety of the experimental deformation conditions. Moreover, the processing map was developed, and stable and unstable deformation regimes were established. The microstructure analysis illustrated that globularization and dynamic recrystallization were the main deformation mechanisms. The porosity of the compressed samples was greatly reduced and influenced by the temperature and strain rate. Considering the material flow stress, hot processing map, microstructure and porosity, the appropriate hot deformation parameters for PM Ti6Al4V alloy preforms are suggested.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-performance molded composites using additively manufactured preforms with controlled fiber and pore morphology

Here, large-scale multimaterial preforms produced by additive manufacturing (AM) underwent compression molding (CM) to produce high-performance thermoplastic composites reinforced with short carbon fibers. AM and CM techniques were integrated to control the fiber orientation (microstructure) and to reduce void content for the improved mechanical performance of the composite. The new integrated manufacturing technique is termed “additive manufacturing-compression molding” (AM-CM). For the present study, the most common materials were used for large-scale printing, i.e., acrylonitrile butadiene styrene (ABS), carbon fiber (CF)–filled ABS (CF/ABS) and glass fiber (GF)–filled ABS (GF/ABS). Three different manufacturing processes; (a) AM (b) extrusion compression molding (ECM), and (c) AM-CM were used to prepare four different panel configurations: (1) neat ABS, (2) CF/ABS, (3) overmold (CF/ABS over neat ABS), and (4) sandwich (neat ABS between two CF/ABS layers). The mechanical properties (tensile and flexural strength and modulus, and Izod impact energy) of samples prepared via all three manufacturing processes were compared. X-ray microcomputer tomography was employed to evaluate the fiber orientation distribution and the volumetric porosity content. The preform maintained high fiber alignment (≈ 82% of fibers within the range of 0–20° in the deposition direction), and the volumetric porosity was reduced by 50% from 3.79% to 1.91% after compression. The alignment of long pores along the deposition direction was also observed. The mechanical properties are discussed with correlation to the fiber alignment and void content in the samples. CF/ABS samples prepared by AM-CM showed significant improvement of 11.15%, 35.27%, 28.6%, and 74.3% in the tensile strength, tensile modulus, flexural strength, and flexural modulus, respectively, when compared with samples prepared by ECM. Unique aspects of this study are the demonstration of large-scale multimaterial AM and the use of multimaterials as preforms to make high-performance composites.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Impact of controlled prewetting on part formation in binder jet additive manufacturing

Binder jetting is an additive manufacturing process that bonds powder through selectively depositing binder by inkjet printing. The part is then extracted and densified by sintering and/or infiltration. The process offers low costs and fast build rates, but properties can be poor due to residual porosity after sintering. The inkjet printing process may contribute to this residual porosity by creating large pores. The droplet kinetic energy ejects some powder particles from the bed and rearranges others. Particle ejection and rearrangement are theorized to create porous regions in binder-jetted parts. In this work, small amounts of moisture are added to the spread powder before printing and the impact on part formation, part properties, and printing parameters measured with varied droplet spacing, droplet velocity, and print frequency. Moisture is added by applying an atomized fluid mixture to the powder between layer spreading and binder printing. The fluid mixture partially evaporates but leaves a stable residue to increase cohesion and enhance imbibition. Moisture addition to the powder increases the range of droplet spacings for line formation while reducing particle ejection, powder rearrangement, and balling in layer and multilayer parts. Excessive moisture addition decreases the effective saturation of printed lines, but saturation in 3D parts is less impacted. Increased surface roughness in the first few layers of a print was also mitigated with prewetting. Finally, high-speed X-ray imaging verified prewetting reduction in particle ejection and rearrangement.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Defect and satellite characteristics of additive manufacturing metal powders

Metal additive manufacturing (AM) requires high-quality metal powders to three-dimensionally (3D) print metallic components with complex and customizable geometries. The lack of quantification of AM metal powders creates quality control challenges for 3D printed components, increases the uncertainty of printing reliability and net cost of inspected and certified printed components, and reduces the recyclability of used powders. However, critical characteristics of AM metal powders that are decisive factors for the 3D printing process, such as internal porosity, contamination, and satellite feature, remain ambiguous. In this work, we developed a novel approach to 3D quantify key characteristics of AM metal powders down to individual particles by using high-resolution synchrotron x-ray computed tomography. Empowered by the penetrative capability of high-energy x-ray, internal porosity and contamination within as-atomized metal powders from high-entropy alloys to nickel-based superalloys were evaluated. Additionally, the newly-developed dispersion method enables the homogeneous separation of individual particles, and consequently, results in the implementation of 3D particle shape analysis. To resolve a major challenge of identification and quantification of satellite-feature particles in as-atomized AM metal powders, the satellite features were quantitated by modeling and analyzing the shape parameter of local thickness variance. Furthermore, the 3D analytical methods of particle assessment in this study can be applied to other materials systems like rock, food, and pharmaceutical particles, and provide insights for process optimization across powder metallurgy, concrete, food and pharmaceutical manufacturing, and AM industries.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Comparison of three-dimensional printing and vacuum freeze-dried techniques for fabricating composite scaffolds

In this study, the performances of different preparation methods of the scaffolds were analyzed for chondrocyte tissue engineering. Silk fibroin/collagen (SF/C) was fabricated using a vacuum freeze-dried technique and by 3D printing. The porosity, water absorption expansion rates, mechanical properties, and pore sizes of the resulting materials were evaluated. The proliferation and metabolism of the cells was detected at different time points using an MTT assay. Cell morphologies and distributions were observed by histological analysis and scanning electron microscopy (SEM). The porosity, water absorption expansion rate, and Young’s modulus of the material obtained via 3D printing were significantly higher than those obtained by the freeze-dried method, while the pore size did not differ significantly between the two methods. MTT assay results showed that the metabolism of cells seeded on the 3D printed scaffolds was more viable than the metabolism on the freeze-dried material. H&E staining of the scaffolds revealed that the number of cells in the 3D printed scaffold was higher in comparison to a similar measurement on the freeze-dried material. Consequently, stem cells grew well inside the 3D printed scaffolds, as measured by SEM, while the internal structure of the freeze-dried scaffold was disordered. Compared with the freeze-dried technique, the 3D printed scaffold exhibited better overall performance and was more suitable for cartilage tissue engineering. - Highlights: • Silk fibroin/collagen was fabricated using 3D printing. • Physical characterization and Cell compatibility were compared. • 3D printed scaffold exhibited better overall performance.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Characterization of white poplar and eucalyptus after ionic liquid pretreatment as a function of biomass loading using X-ray diffraction and small angle neutron scattering

A systematic study was done to understand interactions among biomass loading during ionic liquid (IL) pretreatment, biomass type and biomass structures. White poplar and eucalyptus samples were pretreated using 1-ethyl-3-methylimidazolium acetate (EmimOAc) at 110 °C for 3 h at biomass loadings of 5, 10, 15, 20 and 25 wt%. All of the samples were chemically characterized and tested for enzymatic hydrolysis. Physical structures including biomass crystallinity and porosity were measured by X-ray diffraction (XRD) and small angle neutron scattering (SANS), respectively. SANS detected pores of radii ranging from ~25 to 625 Å, enabling assessment of contributions of pores with different sizes to increased porosity after pretreatment. Contrasting dependences of sugar conversion on white poplar and eucalyptus as a function of biomass loading were observed and cellulose crystalline structure was found to play an important role.

59 BASIC BIOLOGICAL SCIENCES↗