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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Microstructure Analysis of Bismuth Absorbers for Transition-Edge Sensor X-ray Microcalorimeters

Given its large X-ray stopping power and low specific heat capacity, bismuth (Bi) is a promising absorber material for X-ray microcalorimeters and has been used with transition-edge sensors (TESs) in the past. However, distinct X-ray spectral features have been observed in TESs with Bi absorbers deposited with different techniques. Evaporated Bi absorbers are widely reported to have non-Gaussian low-energy tails, while electroplated ones do not show this feature. In this study, we fabricated Bi absorbers with these two methods and performed microstructure analysis using scanning electron microscopy and X-ray diffraction microscopy. The two types of material showed the same crystallographic structure, but the grain size of the electroplated Bi was about 40 times larger than that of the evaporated Bi. This distinction in grain size is likely to be the cause of their different spectral responses.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Microstructural analysis of recycled concrete using X-ray microtomography

This paper reports an investigation of the recycled concrete (RC) microstructure using synchrotron microtomography (μCT) at the Advanced Light Source combined with Scanning Electron Microscopy analysis. The study evaluated the influence of 50% of recycled concrete aggregate (RCA) and its water absorption compensation on the RC microstructure. The following variables were studied: a) the compressive strength of the original concrete used to obtain the RCA (40 and 80 MPa) and b) the initial moisture condition of the RCA (Saturated Surface Dry and Oven Dry). The microtomographic images showed the mixtures cast with RCA in the dry condition developed an evident macropore network surrounding the RCA particle that was not observed in the mixtures using RCA in the SSD condition. SEM images confirmed the initial findings from μCT and showed that the thickness of the interfacial transition zone in RC is in the same order of magnitude as the reference concrete.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Microstructural analysis and thermoelectric properties of Sn-Al co-doped ZnO ceramics

Sn-Al co-doped polycrystalline ZnO ceramics were prepared by sintering in air. Phase and microstructure analysis was performed by X-ray diffraction and SEM-EDS and thermoelectric properties were measured. XRD analysis showed a ZnO primary phase as well as secondary phase peaks due to the formation of a Zn{sub 2}SnO{sub 4} spinel phase or SnO{sub 2}(ZnO:Sn-Al){sub m} intergrowth phase. SEM analysis revealed a dense microstructure with a small number of nanometric pores, consistent with the measured density of 5.48 g/cm{sup 3}. An activated electrical conductivity characteristic of a semiconducting material was observed as well as a negative Seebeck coefficient with both values increasing in absolute value from RT to 730 °C. The power factor had a maximum value of 3.73×10{sup −4} W m{sup −1} K{sup −2} at 730 °C. Thermal conductivity measurements showed a significant reduction over the measured temperature range compared to undoped ZnO. This could be attributed to grain size reduction, the formation of a nanoscale secondary phase or a reduction in crystallinity caused by Sn-Al co-doping. A maximum ZT of 0.06 was obtained at 750 °C for the Sn-Al co-doped ZnO ceramics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Growth of faceted SiC nanostructures using vapor phase condensation: Microstructural analysis

Highlights: • Synthesis of nanocrystalline SiC using thermal plasma route. • XRD data indicates presence of both α- and β-SiC polytypes with β-SiC as the major content. • HRTEM and SAED analysis reveals polytypic arrangement with stacking faults SiC nanoparticles. • TEM micrograph reveals presence of faceted structures such as hexagonal, triangular, triangular pyramidal structure. - Abstract: The paper emphasizes the morphological and microstructural analysis of SiC nanostructures grown by thermal plasma assisted gas phase condensation process. High Resolution Transmission Electron Microscopic and Selected Area Electron Diffraction studies are used to analyze the growth directions and the polytypic arrangement with stacking faults in the as synthesized SiC nanoparticles. The results help in understanding the hierarchical poly-types related to the observed geometries and showed the presence of both α- and β-SiC polytypes. The microstructural study is supported by X-Ray diffraction and UV–Visible absorption spectroscopic studies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Electrical and microstructure analysis of nickel-based low-resistance ohmic contacts to n-GaSb

Ultra low resistance ohmic contacts are fabricated on n-GaSb grown by molecular beam epitaxy. Different doping concentrations and n-GaSb thicknesses are studied to understand the tunneling transport mechanism between the metal contacts and the semiconductor. Different contact metallization and anneal process windows are investigated to achieve optimal penetration depth of Au in GaSb for low resistances. The fabrication, electrical characterization, and microstructure analysis of the metal-semiconductor interfaces created during ohmic contact formation are discussed. The characterization techniques include cross-sectional transmission electron microscopy and energy dispersive spectroscopy. Specific transfer resistances down to 0.1 Ω mm and specific contact resistances of 1 × 10{sup −6} Ω cm{sup 2} are observed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Microstructural analysis on cleavage fracture in pearlitic steels

Microstructural features controlling cleavage fracture in pearlitic structures were investigated by means of scanning electron microscopy and electron backscattered diffraction. It was found that pearlite block size corresponds well to the cleavage facet size, and a single cleavage facet usually contains multiple pearlite colonies. Pearlite block size and cleavage facet size decrease with the refinement of prior austenite grain size, while pearlite colony size only changes slightly. The cleavage crack can largely deflect at block boundaries rather than at colony boundaries. Pearlite block can act as the dominant substructure on cleavage crack propagation in pearlitic steels. - Highlights: •The cleavage crack propagation path in pearlitic structures was analyzed by EBSD. •Pearlite block boundaries can effectively hinder the crack propagation. •Pearlite block size corresponds well to the cleavage facet size. •A single cleavage facet usually contains multiple pearlite colonies.

36 MATERIALS SCIENCE↗
DOE OSTI2023

MATBOX, an Open-Source Microstructure Analysis Toolbox for Meshing, Generation, Segmentation, and Characterization of 3D Heterogenous Volumes

Battery performance is strongly correlated with electrode microstructural properties. To account for its impact, lithium-ion battery (LIB) models either abstract the microstructural heterogeneity of composite electrodes using effective macroscopic properties (macro- or meso- scale models) or directly solve the system of equations on the microstructure geometry or mesh (microstructure-scale models). Therefore, to be adequate, both families of models require information from the microstructure geometry, which can be provided by the numerical tool presented in this work. MATBOX is a MATLAB open-source application [1] developed by NREL for performing various microstructure-related tasks including microstructure numerical generation, image filtering and microstructure segmentation, microstructure characterization and correlation, visualization, and microstructure meshing. MATBOX was originally developed for the analysis of LIB electrode microstructures; however, the algorithms provided by the toolbox are widely applicable to other heterogeneous materials. The toolbox provides a user-friendly experience thanks to a Graphical-User Interface, requires no coding by the user, and is well documented. This presentation will illustrate various MATBOX features for the characterization of a LIB electrode, including a fully automated Representative Volume Element (RVE) analysis, the numerical generation of complex 'virtual' microstructure, including dual-layer electrodes and carbon-binder additive phase, and the meshing of a complex NMC/graphite full cell microstructure suitable for 3D finite-element modeling. Other modules (segmentation, visualization, and correlation) will be briefly presented. Thanks to its modular, open-source approach, MATBOX can easily incorporate third-party algorithms to eventually build a standard in the field that will benefit the whole scientific community. Effective diffusion coefficient [2], additive phase numerical generation [3], and meshing [4] third-party algorithms have been already integrated in the toolbox with more to come.

DIRECT ENERGY CONVERSION,MATHEMATICS AND COMPUTING↗
DOE OSTI2017

A microstructural analysis of aluminum buildup during thermomechanical processing

Highlights: • Microstructure of roll coating developed on a ground steel work roll was examined. • Roll coating was formed during the 20 pass hot rolling schedule of an Al-Mg alloy. • The roll coating had a complex layered nanocrystalline and amorphous structure. • The roll coating layers were composed of metallic Al, porous MgO and C. • Work roll debris, Fe and Cr, were observed embedded within the roll coating. - Abstract: The microstructure and composition of a roll coating built-up on an AISI M2 steel work roll during a 20 pass hot rolling schedule using a laboratory rolling tribo-simulator with a roll-on-block configuration was examined. The AISI M2 steel work roll was characterized by grinding grooves and possessed a surface roughness (R{sub a}) of 0.17 μm. The roll coating developed under these lubricated conditions was discontinuous, patchy and streaked out in the rolling direction. The microstructure and chemical composition of the material transfer that made up the roll coating was analysed and revealed to possess a complex composite microstructure consisting of nanocrystalline aluminum, nanocrystalline/amorphous MgO and amorphous carbon layers. The nanocrystalline MgO layers were porous structures lying between the solid metallic aluminum layers. Debris particles from the wear of the work roll were detected embedded within the carbon layer and at the base of the roll coating. The microstructure of the roll coating appear to be determined by the deformation conditions experienced during the rolling process, while its composition is dependent on the composition of the rolled alloy, the work roll and the lubrication conditions employed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

A User-Friendly GUI Tool for Automated Microstructural Analysis of Fiber-Reinforced Composites and Porous Structures

Understanding and quantifying microstructural features such as fiber orientation and porosity is critical for predicting the mechanical behavior and performance of fiber-reinforced polymer composites. Traditional manual analysis is time-consuming, subjective, and unsuitable for high-throughput datasets. We present a graphical user interface (GUI) application that automates the analysis of microscopy images to extract key microstructural metrics, including fiber orientation tensors, fiber orientation distribution, porosity and pore size distribution. The app integrates multiple image segmentation techniques including global and local thresholding, clustering, and region-based approaches, offering flexibility for different types of image qualities and features. Users can load microstructural images, select regions of interest and segmentation techniques tailored to their image dataset. It also addresses a critical challenge in fiber orientation analysis: the ambiguities caused by touching, overlapping, or partially cut fibers. It supports autorun examples for standardized workflows, enabling reproducible analysis and facilitating training and benchmarking. This tool significantly reduces manual intervention, enhances consistency, and accelerates data generation for structure–property modeling, process optimization, and digital materials research. The tool is intended for use by materials scientists, engineers, and researchers engaged in composite characterization, quality control, and machine learning-based microstructural studies.

Chawla, Komal [ORNL] (ORCID:0000000190327565)↗
DOE OSTI2012

Microstructural Analysis of Irradiated U-Mo Fuel Plates: Recent Results

Microstructural characterization of irradiated dispersion and monolithic RERTR fuel plates using scanning electron microscopy (SEM) is being performed in the Electron Microscopy Laboratory at the Idaho National Laboratory. The SEM analysis of samples from U-Mo dispersion fuel plates focuses primarily on the behavior of the Si that has been added to the Al matrix to improve the irradiation performance of the fuel plate and on the overall behavior of fission gases (e.g., Xe and Kr) that develop as bubbles in the fuel microstructure. For monolithic fuel plates, microstructural features of interest, include those found in the U-Mo foil and at the U-Mo/Zr and Zr/6061 Al cladding interfaces. For both dispersion and monolithic fuel plates, samples have been produced using an SEM equipped with a Focused Ion Beam (FIB). These samples are of very high quality and can be used to uncover some very unique microstructural features that are typically not observed when characterizing samples produced using more conventional techniques. Overall, for the dispersion fuel plates with matrices that contained Si, narrower fuel/matrix interaction layers are typically observed compared to the fuel plates with pure Al matrix, and for the monolithic fuel plates microstructural features have been observed in the U-10Mo foil that are similar to what have been observed in the fuel particles found in U-Mo dispersion fuels. Most recently, more prototypic monolithic fuel samples have been characterized and this paper describes the microstructures that have been observed in these samples.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Microstructural Analysis and Transport Resistances of Low-Platinum-Loaded PEFC Electrodes

In this study, we present microstructural characterization for polymer electrolyte fuel cell (PEFC) cathodes with low platinum loadings (low-PGM). The characterization results are used to quantify the contribution of mass transport resistances to cell voltage losses observed in polarization curve data. Three-dimensional pore morphology and ionomer distribution are resolved using nano-scale X-ray computed tomography (nano-CT). Electrode structural properties are reported along with analysis of the impact of microstructure on the effective charge and reactant transport properties. These characterizations are incorporated with a two-dimensional multi-physics model that accounts for energy, charge, and mass transport along with the effect of liquid water flooding. Defining a total mass transport resistance for the whole polarization curve, contributions of transport mechanisms are identified. Analysis of the experimental polarization curves at different operating pressures and temperatures indicates that the mass transport resistance in the cathode is dominated by the transport processes in the electrode. It is shown that flooding in the electrode is a major contributor to transport losses especially at elevated operating pressures while the pressure-independent resistance at the catalyst surface due to transport through the ionomer film plays a significant role, especially at low temperatures and low catalyst loading. In addition, by performing a parametric study for varying catalyst loadings, the importance of electrode roughness (i.e, electrochemically-active surface area/geometric electrode area) in determining the mass transport losses is highlighted.

25 ENERGY STORAGE↗
DOE OSTI2014

X-ray microstructural analysis of nanocrystalline TiZrN thin films by diffraction pattern modeling

A detailed microstructural characterization of nanocrystalline TiZrN thin films grown at different substrate temperatures (T{sub S}) was carried out by X-ray diffraction (XRD). Total diffraction pattern modeling based on more meaningful microstructural parameters, such as crystallite size distribution and dislocation density, was performed to describe the microstructure of the thin films more precisely. This diffraction modeling has been implemented and used mostly to characterize powders, but the technique can be very useful to study hard thin films by taking certain considerations into account. Nanocrystalline films were grown by using the cathodic pulsed vacuum arc technique on stainless steel 316L substrates, varying the temperature from room temperature to 200 °C. Further surface morphology analysis was performed to study the dependence of grain size on substrate temperature using atomic force microscopy (AFM). The crystallite and surface grain sizes obtained and the high density of dislocations observed indicate that the films underwent nanostructured growth. Variations in these microstructural parameters as a function of T{sub S} during deposition revealed a competition between adatom mobility and desorption processes, resulting in a specific microstructure. These films also showed slight anisotropy in their microstructure, and this was incorporated into the diffraction pattern modeling. The resulting model allowed for the films' microstructure during synthesis to be better understood according to the experimental results obtained. - Highlights: • Mobility and desorption competition generates a critical temperature. • A microstructure anisotropy related to the local strain was observed in thin films. • Adatom mobility and desorption influence grain size and microstrain.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure Analysis and Rheological Behavior of Magnesium Alloys at Semi-solid Temperature Range

Microstructure and rheological properties of AZ91 and Elektron 21 magnesium alloys in semi-solid state were studied. Differential scanning calorimetry revealed significant differences in melting range in analyzed materials. Isothermal annealing for 5, 30 and 80 min, in semi-solid range, corresponding to 50 and 70% of solid fraction, showed slower microstructure coarsening kinetics in Elektron 21 due to the presence of Zr- and RE-enriched precipitations. Ostwald ripening and coalescence resulted in decrease in grains density with increasing annealing time and temperature. Hardness after annealing showed overall tendency to diminish with soaking time probably due to the growth of average grain size. Rheological analysis showed tendency to lower the value of dynamic viscosity coefficient as shear rate rise, which confirmed non-Newtonian flow behavior. The highest values of dynamic viscosity coefficient were obtained for alloy AZ91.

36 MATERIALS SCIENCE↗
DOE OSTI2020

MATBOX (Microstructure Analysis Toolbox) [SWR-20-76]

MATBOX is a MATLAB application for performing various microstructure-related tasks including microstructure numerical generation, image filtering and microstructure segmentation, microstructure characterization, result three-dimensional visualization and result correlation, and microstructure meshing. MATBOX was originally developed to analyze electrode microstructures for lithium ion batteries; however, the algorithms provided by the toolbox are widely applicable to other heterogeneous materials. The toolbox provides a user-friendly experience thanks to a Graphic-User Interface.

Usseglio Viretta, Francois↗
DOE OSTI2013

Chemical selective microstructural analysis of thin film using resonant x-ray reflectivity

Strong modulations of the reflected x-ray intensities near the respective absorption edges of the constituent materials promise to determine layer composition of thin film structures along with spectroscopic like information. Near the absorption edge, the orders of magnitude more contrast beyond the pure electron density distributions of materials find an approach to overcome the low density difficulty of the conventional x-ray reflectivity technique. These aspects are explained by experimental studies on partially decomposed boron nitride thin films. Chemical composition profile is determined from free surface to the embedded buried layer with depth resolution in nanometer scale. The results of resonant reflectivity for chemical analysis are correlated with depth dependent x-ray photo electron spectroscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗