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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Corrosion Behavior of Sm{sub y}(Fe{sub x}Ni{sub 1−x}){sub 4}Sb{sub 12} (0.40 ≤ x ≤ 0.80) in NaCl Solutions Studied by Electron Microscopy and ICP-AES

Filled skutterudites are currently studied as thermoelectric materials to be used in the automotive and nautical field; the study of their resistance to a saline environment is therefore mandatory. To this purpose, the corrosion behavior of several compositions belonging to the Sm{sub y}(Fe{sub x}Ni{sub 1−x}){sub 4}Sb{sub 12} skutterudites system was investigated by immersing samples in differently concentrated (0.1 and 0.5 M) NaCl solutions. The effect of the treatment was analyzed both by SEM–EDS on the sample surface and at fixed times by ICP-AES on the solution. The formation of an oxide layer was observed on the surface of all the samples: the film results uniformly grown on specimens treated in NaCl at the lower concentration, while it is cracked and not spread over the whole surface in the other samples. Relying on the oxide layer thickness, the oxidation resistance results to increase with increasing the Fe content; correspondingly, the Sb concentration in the more diluted solution decreases at each time considered with increasing the Fe amount, pointing at a strict correlation between the cationic release and the oxide formation, and suggesting a possible mechanism for the growth of the protective film.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Electrochemical Frequency Modulation, Electrochemical Noise, and Atomic Force Microscopy Studies on Corrosion Inhibition Behavior of Benzothiazolone for Steel API X100 in 10% HCl Solution

In this work, electrochemical and surface techniques were applied to study the corrosion inhibition effects of benzothiazolone. 10% HCl was used to simulate the oil and gas well-acidizing fluid. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on electrochemical noise data was evaluated by polynomial fitting, and the optimum polynomial order m = 4 was obtained. After detrending, the charge of corrosion reaction obtained by electrochemical noise decreased with increasing inhibitor concentrations. In addition, the inhibition efficiencies from electrochemical noise were in agreement with data obtained by other electrochemical methods. Surface studies illustrated that the corroded surface was smoother in the presence of benzothiazolone. Electrochemical impedance and noise showed that benzothiazolone blocked the electrode surface by adsorption obeying Langmuir isotherm. According to quantum calculation, S atom in benzothiazolone indicated more tendencies for electrophilic attack in adsorption process. The main reason for high inhibition efficiencies in very low concentrations was the planar and simplicity of inhibitor structure which led to increasing the efficiency of adsorption by functional group especially sulfur.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Influencing Factors in Atomic Force Microscopy Based Mechanical Characterization of Biological Cells

AFM-based single cell force spectroscopy is increasingly being used to understand many biological health problems like malaria, cancer etc. A reliable diagnostics needs, accurate measurement and a clear understanding of the influencing factors, which may otherwise sour the measured biomechanics. Results from any successful experimentation should be repeatable and error free. For this, a deeper understanding of the sources of uncertainties, which may affect the results is necessary. In order to assure the accuracy of evaluated properties and to avoid misinterpretation of the experimental data, we have categorized the common causes of uncertainties in an AFM force spectroscopy, based on their sources of origin and discussed possible remedies to them. The present work discusses the assumptions involved in AFM-based biomechanical studies (assumptions in contact model, data analysis, instrument calibration etc.) and their implications in overall estimations of mechanical biomarkers like stiffness, and adhesive strength. Advantages and disadvantages of simultaneous measurement of stiffness and adhesiveness from single force-indentation data have also been discussed.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Design of a graphical user interface for few-shot machine learning classification of electron microscopy data

The recent growth in data generation by modern electron microscopes requires rapid, scalable, and flexible approaches to image segmentation and analysis. Few-shot machine learning, which can richly classify images from a handful of user-provided examples, is a promising route to high-throughput analysis. However, current command-line implementations of such approaches can be slow and unintuitive to use, lacking the real-time feedback necessary to perform effective classification. Here we report on the development of a Python-based graphical user interface that enables end users to easily conduct and visualize the output of few-shot learning models. This interface is portable and can be hosted locally or on the web, providing the opportunity to reproducibly conduct, share, and crowd-source few-shot analyses.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Characterization of dynamic morphological changes of tin anode electrode during (de)lithiation processes using in operando synchrotron transmission X-ray microscopy

The morphological evolution of tin particles with different sizes during the first lithiation and delithiation processes has been visualized by an in operando synchrotron transmission X-ray microscope (TXM). Here, the in operando lithium ion battery cell was operated at constant current condition during TXM imaging. Two-dimensional projection images with 40 nm resolution showing morphological evolution were obtained and analyzed. The analysis of relative area change shows that the morphology of tin particles with different sizes changed simultaneously. This phenomenon is mainly because of a negative feedback mechanism among tin particles in the battery electrode at a constant current operating condition. For irregular-shaped tin particles, the contour analysis demonstrates that the regions with higher curvature started volume expansion first, and then the entire particle expanded almost homogeneously. This study provides insights for understanding the dynamic morphological change and the particle-particle interactions in high capacity lithium ion battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2023

Investigating the failure behavior of cast Al-11Ce-0.4Mg alloys using in-situ scanning electron microscopy tensile testing

Within the last decade, research on Al-Ce-Mg alloys has reported promising results for use in cast part applications. In this paper, the failure behavior of cast Al-11Ce-0.4Mg (wt%) was investigated experimentally with focus on the effect the matrix and intermetallic phases have on the fracture propagation behavior at failure. For the first time, in-situ SEM tensile testing was used to study the failure behavior of cast Al-Ce alloys, reporting results for uniaxial, DIC, and single edge notch tensile tests. The results of the in-situ SEM tensile testing were compared with the materials characterization experiments, which included serial sectioning, EBSD, EDS, and fractography. Analysis of EBSD and EDS mapping of cast Al-11Ce-0.4Mg showed that the cast microstructure was a hypereutectic two phase Al-Ce alloy with grains encompassing large complex colonies of laminar eutectic Al 11 Ce 3 intermetallic. The uniaxial tensile results reported the effect casting defects have on the strength and ductility of the alloy, and DIC in-situ testing showed that the eutectic colonies plastically deform less than the matrix phase. In-situ SEM single edge notch tensile testing displayed how the strength of an individual phase affected the crack propagation direction in the alloy. The results of both the materials characterization and in-situ tensile testing experiments on the failure of this alloy revealed further directions for future alloy development that can improve both the strength and fracture toughness of Al-Ce-Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Analysis of time-dependent strain heterogeneity in shales using X-ray microscopy and digital volume correlation

In this paper, we report the results of a 4-dimensional (3 spatial dimensions plus time) in-situ creep experiment on a milli-core shale plug from Barnett formation in Texas. An outstanding challenge in shale mechanics is connecting observable characteristics to predictable mechanical and hydraulic behavior. We employ novel imaging and analysis techniques to statistically link sample mineralogy and structure to observed deformation. In particular, we focus on mechanisms of porosity reduction during transient response to step changes in stress, analogous to the aseismic deformation that occurs after an episode of fracturing. Our main goal in this study is to take the first steps to visualize and capture the small-scale deformation mechanisms involved in creep of shales, using imaging techniques. To do so, we conducted a uniaxial creep experiment inside an Xradia Versa 520 micro-CT system for 12 h at room temperature under a constant uniaxial stress of 25 MPa. We employed a Digital Volume Correlation (DVC) method to measure micro-scale deforspmation of the sample by comparing the resulting volumetric images with a high-resolution scan of the sample obtained prior to the creep experiment. The results indicate that the time-dependent deformation in the compliant clay plus kerogen matrix constituents facilitates rigid grain rotation and compaction of intergranular porosity at the boundary between rigid grains and matrix.

58 GEOSCIENCES↗
DOE OSTI2019

A transmission electron microscopy study of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750

The microstructure of EBR-II neutron-irradiated austenitic stainless steel 304 and nickel-base alloy X-750 was investigated. Both alloys were irradiated at low dose rates (~2 × 10 -8 dpa/s) to a neutron fluence of 6.9 × 10 22 n/cm 2 (E > 0.1 MeV) at 371–389 °C. Different types of defects, including Frank loops, cavities, and γ' precipitates were characterized. The Frank loops in Type 304 stainless steel (SS) are larger in size (~50 nm in diameter) and lower in number density (2.58 × 10 21 m -3 ), compared to most previous higher dose rate neutron irradiation studies. The Frank loops in X-750 have an average size 26.0 nm of and a number density of 9.44 × 10 21 m -3 . In 304 SS and X-750, cavities are of ~20 nm and ~14 nm in diameter, respectively. The swelling of both alloys was found to be insignificant. In 304 SS, Ni and Si were found enriched at the cavity surfaces and Ni,Si-rich precipitates were also found. Multivariate statistical analysis using non-negative matrix factorization reveals that these Ni,Si-rich precipitates contain only ~5.7 at.% Si, differing from the Ni 3 Si γ' precipitates found in several previous studies. In X-750, L1 2 -structured γ' precipitates were found, and multivariate statistical analysis confirmed the 3:1 stoichiometry (Ni 3 (Ti,Al)) of the precipitates and the superlattice reflections confirmed the stability of the crystal structure of these γ' precipitates, indicating higher-than-expected precipitate stability under high-dose neutron irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Linking sintering stresses to nano modification in the microstructure of BaLa4Ti4O15 by transmission electron microscopy

Highlights: • by systematic HRTEM studies we link the microstructural changes in BLT ceramics to the external pressure applied during sintering; • we developed a mechanistic understanding of the role of stress in sintering; • external stresses during sintering affect the microstructural development at the nanoscale level, being responsible for the creation of higher defective bulk and grain boundary regions; • observation of high density of stacking faults (which generally arrises due to the Ti vacancy layers) indicates that the applied stress is modifying the stacking of AO{sub 3} layers of BLT which in turn creates Ti vacancy layer and stacking faults; • stress assisted sintering has, therefore, the potential to be used as a tool to design microstructures and achieve tailored properties, as suggested from our previous results in BLT and BNT. - Abstract: High quality factor and a temperature stable resonant frequency make BaLa{sub 4}Ti{sub 4}O{sub 15} (BLT) ceramics attractive materials for microwave applications. Aiming to exploit the effects of external stresses on the development of textured and anisotropic microstructures to optimise MW properties, the influence of applied external pressure during sintering of BLT ceramics is analysed. HRTEM and geometric phase analysis (GPA) showed that stresses applied during sintering, trigger the nucleation and growth of faults hypothesised to be due to the errors in the AO{sub 3} layer (basal plane) stacking sequence of the hexagonal perovskite structure. The results reveal a strong correlation between the high concentration of structural defects and the development of anisotropic microstructures, which tune the properties of BLT. Stresses applied during sintering are therefore a promising tool to design material properties.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Surprisingly high irradiation-induced defect mobility in Fe 3 O 4 as revealed through in situ transmission electron microscopy

Radiation-induced defects are expected to change the corrosion kinetics when a material is exposed to a corrosive environment. Characterization of the defects forming under irradiation and their ability to move/diffuse is therefore key to understanding how they impact the corrosion kinetics and possibly mechanisms. For that matter, Fe/Fe 3 O 4 interfaces were irradiated using 1 MeV Kr 2+ at temperatures of 273 K (25 °C), 573 K (300 °C) and 773 K (500 °C) to a maximum dose of 10 dpa (as measured in the Fe matrix) in situ in a transmission electron microscope. The evolution of the microstructure was followed as a function of the dose and temperature. The formation of defects was followed in the metal and the oxide as well as at the metal/oxide interface and characterized in terms of size and density. Additionally, the dynamic observation of the spatial distribution of the defects allowed for a qualitative assessment of the mobility of defects in the oxide as a function of temperature, revealing evidence for enhanced mobility even more so than in the Fe matrix. Mechanisms of induced defect mobility in the spinel are discussed to account for the observations.

36 MATERIALS SCIENCE↗