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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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A numerical study of the meso-structure variability in the compaction process of prepreg platelet molded composites

Compaction deformations in a thermoplastic composite system molded from chopped prepreg platelets were analyzed to obtain statistical distributions of local distortions that define the final consolidated meso-structure. This study provides an insight into and allows quantification of the intrinsic geometric variability of the composite meso-structure that controls the variability of the effective composite mechanical properties. A two-phase viscoelastic finite element model was utilized to treat the behavior of molten prepreg platelets, which were assumed to be incompressible and inextensible in the fiber direction during processing. A two-step simulation procedure with discretely modeled platelets and platelet-to-platelet contacts is proposed. The analysis begins with a drop simulation of the uncontrolled material deposition followed by a 3D finite element analysis of the preform compaction and bulk material flow. The proposed model provides a method for generating a composite meso-structure ab initio starting from a statistical sampling of the initial conditions for platelet deposition. The predicted platelet thickness distribution, intra-platelet fiber waviness and out-of-plane platelet undulations were found to be in good agreement with experimental measurements. An estimate of the volume of resin pockets was inferred from the compaction simulation.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Mechanical Degradation of Graphite/PVDF Composite Electrodes: A Model-Experimental Study

Mechanical failure modes of a graphite/polyvinylidene difluoride (PVDF) composite electrode for lithium-ion batteries were investigated by combining realistic stress-stain tests and mathematical model predictions. Samples of PVDF mixed with conductive additive were prepared in a similar way to graphite electrodes and tested while submerged in electrolyte solution. Young's modulus and tensile strength values of wet samples were found to be approximately one-fifth and one-half of those measured for dry samples. Simulations of graphite particles surrounded by binder layers given the measured material property values suggest that the particles are unlikely to experience mechanical damage during cycling, but that the fate of the surrounding composite of PVDF and conductive additive depends completely upon the conditions under which its mechanical properties were obtained. Simulations using realistic property values produced results that were consistent with earlier experimental observations.

25 ENERGY STORAGE↗
DOE OSTI2018

Inclusion Detection in Aluminum Alloys Via Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has shown promise as a technique to quickly determine molten metal chemistry in real time. Because of its characteristics, LIBS could also be used as a technique to sense for unwanted inclusions and impurities. Simulated Al{sub 2}O{sub 3} inclusions were added to molten aluminum via a metal-matrix composite. LIBS was performed in situ to determine whether particles could be detected. Outlier analysis on oxygen signal was performed on LIBS data and compared to oxide volume fraction measured through metallography. It was determined that LIBS could differentiate between melts with different amounts of inclusions by monitoring the fluctuations in signal for elements of interest. LIBS shows promise as an enabling tool for monitoring metal cleanliness.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Gaussian kernel density functions for compositional quantification in atom probe tomography

Highlights: • A methodology for compositional quantification from atom probe tomography is proposed. • A probability density function p(x) given discrete data points is constructed. • Each atom approximated by a Gaussian function with a particular smoothing parameter. • Density Kernel functions are used to find the optimum smoothing parameter. • The method is validated by using simulated data of semiconductor materials. - Abstract: Atom probe tomography (APT) has the ability to identify the nature and position of single atoms in a material with an almost 3D atomic resolution. However, the quantification of the material composition requires an appropriate treatment of the discrete APT data. When the amount of atoms selected to quantify the composition is relatively small, the spatial resolution is enhanced but the statistical error worsens. Conversely, the increase in the number of atoms considered reduces the spatial resolution, but improving the statistics. We have developed a methodology to reach an optimum equilibrium between the positional and the statistical error in an unsupervised form using Gaussian Kernel density functions. The validity of the method has been tested using APT simulated data of semiconductor materials. It has been proved that the chemical quantification in these materials requires the appropriate selection of the smoothing parameter, obtained without user intervention. In addition, the results have been compared to the usual techniques for composition measurement from APT data (voxelization and proximity histograms), showing better precision for high spatial resolution. This work supplies a data driven methodology based in Gaussian Kernel density functions for the accurate quantification of the composition from APT data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

Presolar grains are small particles found in meteorites through their isotopic compositions, which are considerably different from those of materials in the solar system. If some isotopes in presolar grains diffused out beyond their grain sizes when they were embedded in parent bodies of meteorites, their isotopic compositions could be washed out, and hence the grains could no longer be identified as presolar grains. We explore this possibility for the first time by self-consistently simulating the thermal evolution of planetesimals and the diffusion length of {sup 18}O in presolar silicate grains. Our results show that presolar silicate grains smaller than ∼0.03 μ m cannot keep their original isotopic compositions even if the host planetesimals experienced a maximum temperature as low as 600 °C. Since this temperature corresponds to that experienced by petrologic type 3 chondrites, isotopic diffusion can constrain the size of presolar silicate grains discovered in such chondrites to be larger than ∼0.03 μ m. We also find that the diffusion length of {sup 18}O reaches ∼0.3–2 μ m in planetesimals that were heated up to 700–800°C. This indicates that, if the original size of presolar grains spans a range from ∼0.001 μ m to ∼0.3 μ m like that in the interstellar medium, then the isotopic records of the presolar grains may be almost completely lost in such highly thermalized parent bodies. We propose that isotopic diffusion could be a key process to control the size distribution and abundance of presolar grains in some types of chondrites.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Optically tunable acoustic wave band-pass filter

The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Fracture Analysis of Cohesive Zone Models for Modeling Residual Stress Induced Delamination in Composite Structures

A fracture study of coupon-scale composite cylinders with embedded defects was conducted with an objective to assess and validate a modeling approach using two available cohesive material models. The study included experimental and simulation evaluations of initiation of crack growth and progression. Interrupted thermal experiments used acoustic emissions monitoring to identify the onset of crack progression during each cooling interval and ultrasonic scanning provided images of defect growth. Verification, validation, and uncertainty quantification (VVUQ) processes were performed in the assessment of the simulation predicted temperature at which crack propagation begins (quantity of interest). The Sobol sensitivity analysis identified the hoop direction elastic modulus in the carbon fiber reinforced polymer (CFRP) plies as the most influential parameter for simulations using both cohesive models, accounting for at least 70% of the variation in the temperature at crack propagation. The UQ temperature range for the Tvergaard-Hutchinson model was higher (more conservative) than the experimental acoustic measurement indicators of crack progression, while the temperature range for the Thouless-Parmigiani model enveloped the experimental data points for the primary defect size of 0.75 x 1 in. The simulations could not capture the stable crack growth indicated in the experiments. This is likely due to the models’ inability to represent anisotropic fracture toughness attributed to the structure of the orthotropic fiber weave in a woven composite laminate.

42 ENGINEERING↗
DOE OSTI2022

EERC Final Topical Report – Findings on Subtask 3.2 – Produced Water Management Through Geologic Homogenization, Conditions, and Reuse

The Energy & Environmental Research Center (EERC) was awarded a contract by the North Dakota Industrial Commission (NDIC) Oil and Gas Research Program (NDIC No. G-051-101) to conduct a study on the recycling of water used in oil and gas operations, also known as produced water, from oil- and gas-producing regions of North Dakota as directed by Section 19 of North Dakota House Bill 1014. This final report provides a compilation of results of the study, which include regulatory, scientific, technological, and feasibility methods and considerations associated with North Dakota produced water management. The report provides a synopsis of this project’s previously submitted produced water assessment report entitled “Produced Water Management and Recycling Options in North Dakota” (Energy & Environmental Research Center, 2020), with updated values provided as appropriate. The report provides the results from the investigation of a novel produced water management strategy, referred to as geologic homogenization, conditioning, and reuse (GHCR), which aims to use a subsurface geologic formation as a natural medium for managing produced water recycling and reuse. Water management is a significant technical and economic challenge for sustainable oil and gas production, and water volumes are intrinsically linked to oil production volumes. North Dakota oil production rose to over 1.5 million barrels (MMbbl)/day in 2019, and despite a downturn in oil price in early 2020, North Dakota oil production has recovered to 1.1 MMbbl/day as of August 2021. Bakken petroleum system development between 2008 and 2020 has resulted in a nearly fourfold increase in produced water volumes to 642 MMbbl/yr in 2020 after peaking at 740 MMbbl/yr in 2019 and a fivefold increase in saltwater disposal (SWD) volumes to 565 MMbbl/yr in 2020 after a peak of 682 MMbbl/yr in 2019. Produced water and SWD volumes are forecasted to double by 2030. SWD is the primary method of produced water management used in North Dakota, with approximately 95% of the SWD volume occurring through subsurface injection into sandstones of the Dakota Group (Dakota). Localized pressurization of the Dakota resulting from SWD and projected increases in produced water volumes could impact the economics of North Dakota oil production. As a result, there is an emerging need to pursue alternative produced water management approaches, including recycling and reuse. While produced water recycling is not yet widespread, commercial operators are making strides in overcoming the technical challenges of using high salinity produced water in completion operations (Marathon Oil, 2020). As water management continues to be a key focal point in companies’ environmental, social, and governance (ESG) initiatives, focus on water management, including recycling, will likely continue to increase. Laboratory column testing, field sample collection, geologic modeling and numerical simulation, and techno-economic analysis all indicate that GHCR could feasibly be implemented as a potential water management option. Laboratory column testing and field sample collection indicate that the Inyan Kara sandstone and native formation fluid are capable of homogenizing with the Bakken produced water to a point where the fluid composition appears to stabilize. Extracting that stabilized fluid could be considered homogeneous and capable of providing individual batches of hydraulic fracturing fluid. Numerical simulation results indicate that extraction of fluids from the Inyan Kara in a GHCR implementation scenario is capable of reducing formation pressure, which would help ease localized pressurization of the Inyan Kara and extend the available capacity for nearby existing SWD wells. Economic analysis indicates that there are scenarios where GHCR implementation can be a competitive or even lower-cost option than a conventional water management approach. Site-specific conditions will dictate the economic potential of GHCR, but potentially attractive sites for GHCR implementation will be those that are located above a pressurized zone of the Inyan Kara, need six or more Bakken infill wells, and face high costs for conventional SWD and/or freshwater. Based on the regulatory review, drilling into the Inyan Kara for SWD and to harness as a source water for industrial use have precedent in North Dakota, and a workable regulatory solution for GHCR seems likely. However, restrictions in the state regarding surface storage and transport of produced fluids may limit some activities, which will affect how GHCR could ultimately be implemented. In summary, this study reveals pursuing GHCR can be a viable approach to water management in North Dakota. The GHCR concept addresses some of the challenges that hinder the more traditional approaches to recycling in the industry. Furthermore, an assessment of the current landscape of water management within the state reveals the ongoing trend of increasing volumes of produced water and SWD. Projections reveal that the volumes of produced water that need to be managed are expected to double over the next decade (Energy & Environmental Research Center, 2020). With the continued development of the Bakken and continuing driving factors related to ESG initiatives, implementing a practice such as GHCR is a feasible approach to adding recycling of produced water to industry within the state. This subtask was cofunded through the EERC–U.S. Department of Energy Joint Program on Research and Development for Fossil Energy-Related Resources Cooperative Agreement No. DE-FE0024233. Nonfederal funding was provided by the North Dakota Industrial Commission Oil and Gas Research Program. References Energy & Environmental Research Center, 2020, Produced water management and recycling options in North Dakota: Final Report for North Dakota Legislative Management Energy Development and Transmission Committee and North Dakota Industrial Commission. Marathon Oil, 2020, Sustainability report: https://cdn.sanity.io/files/ghcnw9z2/website/ 91744eb6ef8fbe59505a911c6b8d2e8dd9a537fa.pdf?dl (accessed November 2021).

02 PETROLEUM↗
DOE OSTI2018

Selective growth of Ni4Ti3 precipitate variants induced by complicated cyclic stress during laser additive manufacturing of NiTi-based composites

Highlights: • The NiTi-based composites were in-situ synthesized by SLM. • Ni{sub 4}Ti{sub 3} could tailor the phase transformation temperature of TiC/NiTi composites. • A three-dimensional stress field modeling of TiC/NiTi composites was established. • The relationship between growth of Ni{sub 4}Ti{sub 3} variants and cyclic stress was disclosed. - Abstract: NiTi-based composites were in-situ synthesized by selective laser melting (SLM) additive manufacturing technology with formation of a great many Ni{sub 4}Ti{sub 3} precipitates. The differential scanning calorimetry (DSC) were carried out to exhibit the similar phase transformation temperature (A{sub s} = 51.82 °C, A{sub f} = 94.02 °C, M{sub s} = 55.87 °C and M{sub f} = 18.93 °C) by comparing with that of SLM-fabricated equi-atomic NiTi alloy, which could be attributed to the compensation of Ni{sub 4}Ti{sub 3} precipitates for the effect of an addition of TiC particles. Three different Ni{sub 4}Ti{sub 3} precipitate variants ((111){sub R}//(1 1-bar 1-bar ){sub B2}, (111){sub R}//( 1-bar 1-bar 1){sub B2}, and (111){sub R}//( 1-bar 1 1-bar ){sub B2}) with various precipitate diameters were observed within SLM fabricated part, showing apparently selective growth behavior. By high-resolution transmission electron microscopy, severe lattice defects formed surrounding the smaller variant, while relatively intact lattice structure was found around the larger one, which indicated that high strain energy was produced in the interface between the matrix and the smaller variant. Furthermore, finite element simulation method was applied to disclose the evolution features of complicated cyclic stress during SLM processing of TiC/NiTi composites. By predicting, the main constraint mode within as-fabricated track was tensile stress effect. Based on the redistribution behavior of thermal stress and the coupling effect between the thermal stress and strain field induced by Ni{sub 4}Ti{sub 3} precipitate, the selective growth mechanism of Ni{sub 4}Ti{sub 3} variant was revealed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Miktoarm Stars via Grafting-Through Copolymerization: Self-Assembly and the Star-to-Bottlebrush Transition

The grafting-through copolymerization of two distinct macromonomers via ring-opening metathesis polymerization is normally used to form statistical or diblock bottlebrush polymers with large total backbone degrees of polymerization (N BB ) relative to that of the side-chains (N SC ). Here, we demonstrate that Grubbs-type chemistry in the opposite limit, namely N BB << N SC , produces well-defined materials with excellent control over ensemble-averaged properties, including molar mass, dispersity, composition, and number of branch points. The dependence of self-assembly on these molecular design parameters was systematically probed using small angle X-ray scattering and self-consistent field theoretic simulations. Moreover, our analysis supports the notion that two-component bottlebrush copolymers with small N BB behave like miktoarm star polymers. The star-to-bottlebrush transition is quantifiable for both statistical and diblock sequences by unique signatures in the experimental scaling of domain spacing and simulated distribution of backbone/side-chain density within lamellar unit cells. These findings represent a conceptual framework that simplifies the synthesis of miktoarm star polymers when dispersity in the number of arms and composition can be tolerated. The analytical approach introduced to distinguish chain conformations in complex macromolecules also complements previous methods, for example form factor scattering and rheology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Magnetic properties and microstructure of Sm-Co/α-Fe nanocomposite thick film-magnets composed of multi-layers over 700 layers

We synthesized Sm-Co/α-Fe nanocomposite film-magnets, approximately 10 μm in thickness, composed of 780 layers by the pulse laser deposition method. Transmission electron microscopic observations revealed that the synthesized film is composed of Sm-Co and α-Fe layers with the well-controlled α-Fe thickness of approximately 10–20 nm, which is suitable one predicted by the micromagnetic simulation. In spite of the enhanced interlayer diffusion of Fe and Co by annealing for crystallization, the (BH){sub max} value of 100 kJ/m{sup 3} was obtained at the averaged compositions of Sm/(Sm + Co) = 0.16 and Fe/(Sm + Co + Fe) = 0.47. The α-Fe fraction for obtaining the highest (BH){sub max} value was smaller than that expected from the micromagnetic simulation. Although the annealing for crystallization lay the easy direction of magnetization in the plane, the film is not expected to have strong crystallographic texture.

36 MATERIALS SCIENCE↗
DOE OSTI2017

The IRX–β Relation: Insights from Simulations

We study the relationship between the UV continuum slope and infrared excess (IRX≡L{sub IR}/L{sub FUV}) predicted by performing dust radiative transfer on a suite of hydrodynamical simulations of galaxies. Our suite includes both isolated disk galaxies and mergers intended to be representative of galaxies at both z∼0 and z∼2--3. Our low-redshift systems often populate a region around the locally calibrated Meurer et al. relation but move above the relation during merger-induced starbursts. Our high-redshift systems are blue and IR luminous and therefore lie above the Meurer et al. relation. The value of β strongly depends on the dust type used in the RT simulation: Milky-Way-type dust leads to significantly more negative (bluer) slopes compared with Small-Magellanic-Cloud-type dust. The effect on β due to variations in the dust composition with galaxy properties or redshift is the dominant model uncertainty. The dispersion in β is anticorrelated with specific star formation rate (sSFR) and tends to be higher for the z∼2--3 simulations. In the actively star-forming z∼2--3 simulated galaxies, dust attenuation dominates the dispersion in β, whereas in the z∼0 simulations, the contributions of star formation history (SFH) variations and dust are similar. For low-sSFR systems at both redshifts, SFH variations dominate the dispersion. Finally, the simulated z∼2--3 isolated disks and mergers both occupy a region in the IRX--β plane consistent with observed z∼2--3 dusty star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature, the blue colors of high-z DSFGs do not imply that they are short-lived starbursts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Calibration of laboratory aging practice to replicate changes to roof albedo in a Chinese city

Highly reflective roofs can save building air conditioning energy, mitigate the urban heat island, and offset CO 2 emissions. A laboratory aging methodology was developed to simulate change in the solar reflectances of field-applied roof coatings induced by one year of natural exposure in Guangzhou (China). The approach compared the changes in solar reflectance spectra observed in the naturally exposed materials with those obtained following a three-stage laboratory procedure: conditioning, soiling, and weathering. The method was systematically modified over five trials by adjusting the key variables in laboratory aging: composition of the soiling mixture, deposition mass, and conditions of soiling application. Tests were performed using a small number of specimens. Simulating exposure in Guangzhou required a loading of soiling agents greater than that used to simulate US cites. In the final trial, the reduction in solar reflectance was reproduced to within an average of 0.02 for three of the six products, and to within an average of 0.06 for the remaining three products.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Modeling the Work Hardening Behavior of High-Manganese Steels

The work hardening of a series of high-manganese steels with various chemical compositions (manganese contents of 18–30 wt.% and carbon contents of 0.06–1.2 wt.%) and deformation products (mechanical twins and/or ε-martensite) was modeled using a physics-based model. The model comprised the contributions of dislocation glide and phase transition (mechanical twinning and/or ε-martensite formation) kinetics to the overall work hardening rate. The model parameters included the physical characteristics of the steels such as the stacking fault energy as well as the microstructural features such as the volume fraction of the deformation products. A key point of the model was that it is globally applicable for all high-manganese steels—including twinning-induced plasticity and/or transformation-induced plasticity steels—instead of being limited to a specific category of these steels. A good agreement was found between the predicted and observed work hardening for all the experimental alloys in this study as well as several high-manganese steels in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Grain boundary segregation beyond the dilute limit: Separating the two contributions of site spectrality and solute interactions

Solute segregation at grain boundaries (GBs) is known to have a profound impact on material properties, and as such is becoming routinely used as an element in alloy design. Beyond the dilute limit, the extent of solute GB segregation is known to be concentration dependent. Using hybrid Monte Carlo/Molecular Statics simulations of Mg segregation in Al, in this work we decouple the two contributions to this composition dependence: (i) spectrality of atomic environments at the boundary and (ii) solute-solute interactions. Although only contribution (ii) is typically considered in the literature, we argue that both contributions are equally important to understand concentration dependence and correctly quantify GB solute segregation in a binary alloy. Finally, a thermodynamic segregation isotherm is outlined that accounts for both the spectrality of grain boundary sites and solute-solute interactions. Unlike classical isotherms like those of McLean or Fowler-Guggenheim, which can be successfully fitted to GB segregation data only over a limited range of composition and temperature, our proposed model is shown to be accurate across the composition-temperature space.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Enhancing microsegregation during rapid directional solidification through ternary microalloying

The nano-cellular dendritic microstructure formed during rapid directional solidification in powder bed fusion additive manufacturing creates unique properties such as simultaneous improvement in strength and ductility. However, process control of microsegregation features remains challenging due to low sensitivity of critical solidification mechanisms to process parameters. This study leverages microalloying to achieve large changes in dendrite composition, microstructure, and interdendritic zone width during laser powder bed fusion without modifying process parameters. CALPHAD simulations predict that the addition of Zr significantly steepens the solidus line of the dilute Cu-Cr alloy system, leading to enhanced Cr rejection into the melt and greater than 95% reduction in solubility of Cr in the solidified Cu matrix. Experimental validation using time-of-flight secondary ion mass spectrometry and Kelvin probe force microscopy reveals that the ternary alloy containing 0.01 wt% Zr exhibited wider interdendritic regions compared to the binary, a significantly higher number of Cr-rich particles within interdendritic regions, near-complete ejection of oxygen impurities from the matrix, and greater nanoscale work function contrast. These features indicate more aggressive Cr segregation in the presence of Zr and a purer Cu matrix and provide a potentially robust method for engineering the nano-cellular dendritic solidification microstructure.

CALPHAD↗
DOE OSTI2020

Partitioning of tramp elements Cu and Si in a Ni-based superalloy and their effect on creep properties

An alloy's processing history, including melting, remelting or the choice of stock material, affects its purity and eventually involves tramp element pickup or retention. Herein, variants of a novel Ni-based superalloy were manufactured with different levels of purity. The so-called low purity alloys contained 0.138 wt. % Cu and 0.019 wt. % Si while the Cu and Si levels were below x-ray fluorescence (XRF) detection limits of 0.003 and 0.010 wt. %, respectively, in the high purity ingots. Atom-probe tomography (APT) was carried out and revealed Si partitioning at the following interfaces: grain boundaries, MC carbide/γ, M 3 B 2 boride/$γ$ and M 3 B 2 boride/$γ$'. Copper was found to primarily segregate to the $γ$' precipitates. An average of 2.4 × decrease in creep life and 4.3 × decrease in creep ductility was measured in the low purity alloys, which was attributed to the embrittlement caused by Si segregation to grain boundaries. Furthermore, the positive effect of B on the creep properties was mitigated by the presence of Si. Thermodynamic predictions for the matrix and γ' precipitate compositions represented the trends observed experimentally although the extent of preferential partitioning lacks accuracy. Monte Carlo simulations were performed to describe the partitioning of Cu and Si atoms to either $γ$ or $γ$' phases.

36 MATERIALS SCIENCE↗