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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Identification and characterization of circular RNAs in rapid atrial pacing dog atrial tissue

Highlights: • Revealed the expression characterization of circRNAs in dog atrial tissue. • Compared differentially expressed circRNAs between atrial fibrillation and control dog. • Found extensive interaction among circRNAs and AF related miRNAs and mRNAs. Circular RNAs (circRNAs) have emerged as novel molecules of interest in gene regulation as other noncoding RNAs, and participating in the process of many diseases. However, the expression and functions of circRNAs in Rapid atrial pacing (RAP) dog atrial tissue still unknown. 12 canines were randomly assigned to control and pacing group. RAP at 500 beats per minute was maintained 14 days in the pacing group. The expression characterization of circRNAs were revealed by high-throughput sequencing. We totally predicted 15,990 circRNAs in dog atrial tissues. Moreover, we found 146 differentially expressed circRNAs between control and RAP dogs. Five circRNAs were selected for subsequent RT-PCR validation, and four circRNAs confirmed with the high throughput sequencing analysis. GO analysis showed that the differentially expressed circRNAs might involve in the process of “structural constituent of cytoskeleton, ion channel activity”. We explored the circRNA-miRNA interaction network, and found extensive interaction among differentially expressed circRNAs and AF related miRNAs and mRNAs. Our work firstly identified the characterization of circRNAs in the dog atrial, and revealed the differentially expressed circRNAs in the RAP dog, this might lay a solid foundation on the function of circRNA in the mechanisms of AF.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Green synthesis and characterization of silver nanoparticles using Enicostemma axillare (Lam.) leaf extract

Highlights: • Green synthesis of AgNPs is using Enicostemma axillare. • Characterization of AgNPs was done by TEM, SEM and XRD. • The synthesized AgNP solution was stable for more than two months. • The method was eco-friendly, benign and cost-effective. In the present article, the facile green synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Enicostemma axillare (Lam.) has reported. This is a simple, cost-effective, stable for a long time and reproducible aqueous synthesis method to obtain a self-assembly Ag nanoparticles. The size and shape of Ag nanoparticles were characterized by XRD, TEM, and SEM-EDS. The formation and stability of the reduced silver nanoparticles in the colloidal solution were monitored by UV–Vis spectrophotometer analysis. Zeta potential was confirmed by DLS study. The mean particle diameter of silver nanoparticles was calculated from the TEM, SEM and the size of the particles was measured between 15 and 20 nm. TEM analysis revealed the spherical shape of the particles. Crystalline nature of the nanoparticles in the face-centred cubic structure are confirmed by the peaks in the XRD pattern corresponding to (111), (200), (220) and (311) planes. This study showed the biogenic, environmentally friendly and cost-effective synthesis and characterization of the silver nanoparticles.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Purification and characterization of two cysteine proteinase inhibitors from silkworm, Bombyx mori

Highlights: • Two recombinant silkworm cysteine proteinase inhibitors were characterized. • The inhibitors showed different inhibitory activities toward cathepsin L. • Secondary structures of both inhibitors were analyzed at different temperatures. • The C-terminal tail was found to be necessary for BCPI inhibitory activity. • Arginine (R31) is important for the inhibitory activity in BCPI. Cysteine proteinase inhibitors from silkworm are selective inhibitors with low molecular weight and regulate cathepsin L-like cysteine proteinase activity, thus, affecting silkworm metamorphosis. In a previous study, two cysteine proteinase inhibitors, BCPI and BmCPI, were identified in the silkworm genome. To characterize these inhibitors, we expressed and purified them in an Escherichia coli system and analyzed their structure and inhibitory activity in vitro. Both inhibitors showed strong tolerance to high temperature. Their CD spectra revealed that their secondary structures could be recovered by a gradual decrease in temperature. Compared to BCPI, BmCPI exhibited weak inhibitory activity toward cathepsin L. BCPI activity was significantly decreased when its C-terminus was truncated, whereas BmCPI activity increased considerably when the C-terminus tail of BCPI was attached to BmCPI. Additionally, the inhibitory activity of BCPI was strongly reduced if R31 was mutated to A31. In summary, two cysteine proteinase inhibitors from silkworm were characterized in the present study, which facilitates an understanding of the interaction mechanism between cysteine proteinase and its inhibitors in the silkworm.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Generation of and characterization of anti-IL-11 antibodies using newly established Il11-deficient mice

Highlights: • Aniti-IL-11 antibody blocks IL-11-, but not IL-6-induced cell proliferation. • Anti-IL-11 antibody detects IL-11-poducing cells of colon cancer in wild-type mice. • We established two lines of Il11−/− mice by the CRISPR-Cas9 method. • These tools might be valuable to elucidate the functions of IL-11 in vivo. Interleukin (IL)-11 belongs to the members of the IL-6 family of cytokines and is involved in a variety of biological responses, including hematopoiesis, bone development, and carcinogenesis. However, the cellular sources of IL-11 and regulation of IL-11 expression under physiological and pathological conditions are not fully understood. One of the causes to prevent characterization of IL-11 in vivo is due to the lack of reliable antibodies that detect IL-11 by immunohistochemistry. Moreover, although mice lacking Il11ra have been generated and extensively characterized, Il11-deficient mice have not been characterized yet. Here we generated two anti-IL-11 antibodies that blocked biological activities of IL-11 and detected IL-11 by immunohistochemistry, respectively. One clone of anti-IL-11 antibodies blocked IL-11-, but not IL-6-induced cell proliferation and IL-11-induced phosphorylation of STAT3 of an IL-11-dependent cell line. Moreover, we used recently established Il11-deficient mice to test the specificity of anti-IL-11 antibodies for immunohistochemistry. Another clone of anti-IL-11 antibodies stained stromal cells surrounding tumors of the colon of wild-type, but not Il11-deficient mice following treatment with Azoxymethane plus dextran sulfate sodium. Together, these newly developed anti-IL-11 antibodies provide a better understanding of the functions of IL-11 in vivo under various physiological and pathological conditions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Evolutionary conservation of transferrin genomic organization and expression characterization in seven freshwater turtles

Highlights: • Transferrin have evolutionary conservation in genomic organization in freshwater turtles. • Transferrin have evolutionary conservation in expression characterization in freshwater turtles. • 12 positive selected sites were detected in freshwater turtles which were mainly located on the surface of Tf proteins. Serum transferrin (tf), encoding an iron-binding glycoprotein, has been revealed to play important roles in iron transportation and immune response, and it also has been demonstrated to be valuable for phylogenetic analysis in vertebrates. However, the evolutionary conservation, expression profiles and positive selection of transferrin genes among freshwater turtle species remain largely unclear. Here, the genomic DNA and coding sequences of transferrin genes were cloned and characterized in seven freshwater turtles including Mauremys mutica, Mauremys sinensis, Cyclemys dentate, Mauremyssi reevesi, Heosemys grandis, Trachemys scripta and Chrysemys picta. The isolated coding sequences of turtles' tf genes were 2118 bp or 2121 bp, encoding 706 or 707 amino acids. The predicted Tf proteins of turtles share high identities with M. mutica Tf, up to 91%–98% and the M. mutica Tf has the highest identity (91%) in amino acid with the Chelomia mydas Tf, the moderate with other reptiles' Tfs (65%–59%), chicken (58%), and Human Tf (∼55%), and the lowest with zebrafish Tf (41%). Additionally, tf genes were consistently composed of 17 exons and 16 introns with the same splicing sites in introns in all the turtles examined. Moreover, 12 positive selected sites were detected in these turtles’ Tf and mainly distributed on the surface of transferrin protein. Importantly, it was found that transferrin genes in all turtles examined were predominantly expressed in adult liver via real-time quantitative PCR. The molecular characterizations and expression profiles of transferrin would shed new insights into understanding the conversations and divergences of transferrin genes in turtles, even in vertebrates.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

SANS coupled with fluid invasion approaches for characterization of overall nanopore structure and mesopore connectivity of organic-rich marine shales in China

The pore structure of shales, including pore morphology, connectivity, pore volume, specific surface area (SSA), and pore size distribution (PSD), is a significant factor in controlling gas storage and transport and the migration mechanisms of hydrocarbons. However, the lack of comprehensive characterization for both accessible and inaccessible pore structure increases the difficulty of gas-in-place estimation and gas exploration. In order to investigate the nanoscale pore system, integration of high-pressure mercury intrusion porosimetry (MIP), low-pressure N 2 /CO 2 adsorption (LNA/LCA), and small-angle neutron scattering (SANS) were employed to obtain a multi-scale quantitative characterization of the nanopore structure of organic-rich marine shale samples from the Longmaxi and Niutitang Formations in China. In this work, PSDs obtained from the combined techniques appropriately cover an overall nanopore size range of shale (0.35–15,000 nm) and overcome the limits of the individual method. Uni-, bi, and multi-modal PSDs were observed, but the sizes of a significant portion of the nanopores observed in these shales range from 0.35 to 100 nm. Pore volumes and surface areas of micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm) were characterized based on the best performance window of each technique: LCA for micropores; LNA and SANS for mesopores; and MIP for macropores. It was found that micropores are the major contributor to the total SSA for both the Longmaxi and Niutitang shales. With respect to pore volume, however, the contribution to the total pore volume has a trend of micropore < mesopore < macropore for the Longmaxi shale samples, but micro-/mesopore volumes are greater than macropore volumes for samples of the Niutitang shale. Strong correlations were also observed between total organic carbon (TOC) content and micropore volume and surface area, which implies that organic matter is a controlling factor in the micropore system of organic-rich shales. In addition, strong correlations between methane adsorption capacity and both micro-/mesopore volumes and SSAs indicate that micro-/mesopores are governing factors for methane storage. Furthermore, the fractions of accessible mesopore volume and surface area were quantitatively estimated by SANS and LNA. Correlation analyses suggest that the accessibility of the mesopore surface area could be an indicator for gas transport and storage in mesopores in organic matter. Thus, a shale with higher connectivity could have higher gas diffusion capability but lower gas adsorption capacity, and vice versa.

58 GEOSCIENCES↗
DOE OSTI2025

WigglyRivers: A tool to characterize the multiscale nature of meandering channels

Channel sinuosity is ubiquitous along river networks, producing complex patterns that encapsulate and influence morphodynamic processes and ecosystem services. Accurately characterizing these patterns is challenging with traditional curvature-based algorithms. Here, in this study, we present WigglyRivers, a Python package that builds on existing wavelet-based methods to create an unsupervised meander identification and characterization tool. The package uses planimetric information the user provides or from the USGS’s High-Resolution National Hydrography Dataset to characterize individual reaches or entire river networks. WigglyRivers also includes a supervised river identification tool for manually selecting individual meandering features. Here, we provide examples of idealized river transects and show the capabilities of WigglyRivers. We also use the supervised identification tool to validate the unsupervised identification on river transects across the continental US. WigglyRivers is a tool to understand better the multiscale characteristics of river networks and the link between river geomorphology and river corridor connectivity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Synthesis and morphological characterization of linear and miktoarm star poly(solketal methacrylate)- block -polystyrene copolymers

The synthesis, molecular characterization, and morphological evaluation of AB n, (n = 2,3) miktoarm star block copolymers consisting of poly(glycerol monomethacrylate) (PGMA) and polystyrene (PS) with varying molecular weights and compositions is described. The system is known to demonstrate a remarkably high Flory-Huggins interaction parameter. The corresponding linear diblock copolymer analogues, were synthesized as well, and comparisons with regard to feature dimensions and morphologies are provided. Well-ordered nanostructures of various morphologies were formed with domain spacing as low as 7.2 nm. Different morphologies were attained by some of the topological isomers indicating that in miktoarm star block copolymers the phase boundaries were strongly shifted. Additionally, a triblock ABA analogue was studied to investigate the effect of triblock copolymer conformations. Noteworthy is that for copolymers with different macromolecular architecture leading to similar morphology; different domain spacings were obtained. The synthesis of all the samples was carried out by high-vacuum anionic polymerization techniques. Molecular characterization with Size Exclusion Chromatography (SEC) and Proton Nuclear Magnetic Resonance Spectroscopy ( 1 H NMR) confirmed well-defined copolymers obtained. The morphological characterization was accomplished by Small-Angle X-ray Scattering (SAXS). In conclusion, the observations from this study highlight the potential of incorporating macromolecular architecture in the self-assembly of strongly immiscible block copolymers to attain ultra-small nanofeatures with desired morphologies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

In situ characterization of phase transformations in petroleum pitch by high temperature X-ray diffraction

The phase transformation from isotropic to mesophase of a petroleum-derived pitch was monitored by in situ X-ray diffraction at 410 °C. The kinetics of the transformation were characterized by monitoring the growth of a broad peak at 2θ~24° and could be described by Avrami’s equation. The volatilization of low molecular weight components originally present in the pitch, or produced during the condensation reaction, was assessed by thermal gravimetry analysis, following the same thermal history. Ex situ characterizations of the pitch precursor before and after thermal treatment provided insight into the evolution of the molecular structure associated with mesophase generation (optical polarized microscopy, molecular weight distribution by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, X-ray photoelectron spectroscopy, Auger spectroscopy, and thermal stability). Here, this investigation demonstrates the value of using complementary in situ and ex situ experimental techniques to characterize complex mechanisms during the processing of organic materials.

02 PETROLEUM↗
DOE OSTI2020

Three-dimensional seismic characterization and imaging of the Soda Lake geothermal field

Accurate characterization of subsurface geophysical properties and detection of the fault system are essential for geothermal energy exploration and production. The Soda Lake geothermal field is in western Nevada with a complex fault system. Previous seismic characterization only produced a low-resolution, smooth velocity model along with a simple, conceptual fault model. Using optimized correlation-based full-waveform inversion, wavefield-separation-based reverse-time migration, and automatic fault detection techniques, we present 3D seismic characterization for the Soda Lake geothermal field using 3D surface seismic data acquired with Vibroseis sources. Here, we obtain 3D high-resolution velocity, density, and acoustic impedance models, 3D seismic images with different grid spacings, and a high-resolution fault system. Consistency check between the constructed faults and currently active injection and production geothermal wells verifies that our seismic inversion and imaging results and detected faults are reliable. These results can provide valuable information for optimizing well placement and geothermal energy production at the Soda Lake geothermal field.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Structural and spectroscopic characterization of thorium pyrasal complexes

To explore the coordination chemistry of thorium, the most abundant radioactive element on earth, we examine the synthesis and characterization of two Th (IV)-pyrasal complexes, L1 “pyrasal” ((2,2'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))diphenol), and L2 “naphthylpyrasal” (1,1'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol). These complexes demonstrate little or no fluorescence when compared to similar naphthylsalophen thorium complexes previously published. Each complex was synthesized and characterized by IR, NMR (1H), and mass spectrometry. The photometric properties of the complexes were characterized using UV–Vis and fluorescence spectroscopy and their solid-state molecular structures were established by single-crystal X-ray crystallography. The electron-withdrawing effects of the pyrazine ring creates changes in the thorium coordination environment resulting in a secondary solid-state extended structure that minimizes the pi-pi stacking. Further, this subsequently causes an overall decrease in the intensity of fluorescence demonstrated previously in by naphthylsalophen thorium complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Progress in development of characterization capabilities to evaluate candidate materials for direct air capture applications

As part of U.S. national efforts to combat the detrimental effect of global climate change, the National Institute of Standards and Technology (NIST) was recently tasked to support efforts in direct air capture (DAC) of carbon dioxide research and deployment. In order to develop test procedures, materials, and documentary standards, key characterization methods relevant to DAC materials have been investigated and used to identify desirable properties for a potential Standard Reference Material (SRM). Select amine-supported materials that previously showed potential for DAC applications have been characterized using commonly available laboratory methods. Further insights into the adsorption characteristics have been gained from developing and applying more specialized characterization tools ideal for probing low concentrations of carbon dioxide. A broad suite of capabilities that examine relevant properties under appropriate conditions gives the most profound insights into a material's specific performance. We advocate for even more specialized capabilities to be developed and standardized to quantitatively monitor the interactions of CO 2 with molecular species in complex and often disordered systems to advance DAC and support carbon dioxide reduction (CDR) in general.

carbon dioxide↗
DOE OSTI2019

Discovery and Characterization of FMN-Binding β-Glucuronidases in the Human Gut Microbiome

The human gut microbiota encodes β-glucuronidases (GUSs) that play key roles in health and disease via the metabolism of glucuronate-containing carbohydrates and drugs. Hundreds of putative bacterial GUS enzymes have been identified by metagenomic analysis of the human gut microbiome, but less than 10% have characterized structures and functions. Here in this paper we describe a set of unique gut microbial GUS enzymes that bind flavin mononucleotide (FMN). First, we show using mass spectrometry, isothermal titration calorimetry, and x-ray crystallography that a purified GUS from the gut commensal microbe Faecalibacterium prausnitzii binds to FMN on a surface groove located 30 Å away from the active site. Second, utilizing structural and functional data from this FMN-binding GUS, we analyzed the 279 unique GUS sequences from the Human Microbiome Project database and identified 14 putative FMN-binding GUSs. We characterized four of these hits and solved the structure of two, the GUSs from Ruminococcus gnavus and Roseburia hominis, which confirmed that these are FMN binders. Third, binding and kinetic analysis of the FMN-binding site mutants of these five GUSs show that they utilize a conserved site to bind FMN that is not essential for GUS activity, but can affect KM. Lastly, a comprehensive structural review of the PDB reveals that the FMN-binding site employed by these enzymes is unlike any structurally characterized FMN binders to date. These findings reveal the first instance of an FMN-binding glycoside hydrolase and suggest a potential link between FMN and carbohydrate metabolism in the human gut microbiota.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Characterizing surrogates to develop an additive manufacturing process for U 3 Si 2 nuclear fuel

U 3 Si 2 is considered as an accident-tolerant nuclear fuel candidate due to its promising high uranium density along with its improved thermal properties. The current U 3 Si 2 powder metallurgical fabrication process encompasses numerous process steps with extensive fabrication times. Thus, an additive manufacturing process to fabricate U 3 Si 2 is currently under development to ultimately produce U 3 Si 2 fuel at a lower cost, in a timely and commercially-reliable manner. The current research work seeks to characterize U 3 Si 2 surrogate materials fabricated by a laser synthesis. The characterization results provided novel microstructural data that aided in the early development stages of an additive manufacturing process. For this study, cerium, zirconium, and hafnium, were selected as surrogates based on their thermodynamic properties and crystal structure. As a result, the laser-synthesized samples were characterized by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) along with X-ray diffraction (XRD), where the different phases of formation, morphology, and microstructural features have been analyzed. Laser synthesis showed suitability for alloying Zr-Si and Hf-Si to ultimately form silicide compounds (Zr 3 Si 2 and Hf 3 Si 2 ).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

High energy X-ray characterization of the microstructure of PuGa alloy samples at macroscopic depths and non-ambient conditions

High energy (95 keV) X-rays were utilized to characterize the microstructure of eight PuGa alloy samples at room temperature and during cooling to ∼10 K. The samples had different Ga content (nominally 0-3.4 at.%), age, and history. A ninth sample, similarly characterized with neutron diffraction, was included to extend the Ga range to 7 at.%. The samples span the range from single phase α (monoclinic) to δ (face-centered cubic) PuGa, as well as a two-phase α′/δ sample. The crystallographic textures, phase fractions, lattice parameters and dislocation densities of each sample were evaluated through distinct analysis techniques. The textures of the samples were modest. In each case, the dislocation densities were relatively high, comparable to cold worked metals and metals exposed to similar radiation dose. At room temperature, the lattice parameters determined in the predominantly single-phase samples were larger than expected based on the nominal Ga concentration. The observed lattice thermal expansions of the single-phase δ samples to 10 K are self-consistent across the samples and consistent with previous measurements reported in the literature. Significantly larger thermal lattice strain is observed in the δ phase of the two-phase material due to mechanical constraint from the α′ phase, which has a three times larger thermal expansion and is much harder than the δ phase. In conclusion, the results demonstrate the unique value of high-energy X-rays for relatively routine microstructural characterization of Pu alloy samples.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Operando NMR characterization of cycled and calendar aged nanoparticulate silicon anodes for Li-ion batteries

Replacing graphite anodes with Si anodes can greatly increase the energy of current Li-ion batteries. Detailed characterization of Si lithiation reactions, SEI formation, and reversibility are therefore active areas of research. Solid-state 7 Li nuclear magnetic resonance (NMR) spectroscopy is useful for characterizing different lithium local environments within Si anodes. Here, we developed an operando NMR methodology to characterize aging of carbon-coated nanoparticulate Si anodes in pouch cells paired with Ni-rich cathodes. We observed a new lithiation mechanism in the Si nanoparticles: direct formation of over-lithiated Li 15+x Si 4 (x<0.6) phase. Furthermore, our novel operando cells maintained good performance with long-term cycle and calendar aging. Here we identified trapped lithium silicides as a major contributor to capacity fade with aging. Finally, we determined that the addition of Mg (TFSI) 2 to the electrolyte decreased the amount of trapped lithium silicides and therefore increased the capacity and capacity retention for the nanoparticulate Si used.

25 ENERGY STORAGE↗
DOE OSTI2018

Interfacial characterization by TEM and nanoindentation of W-Eurofer brazed joints for the first wall component of the DEMO fusion reactor

Highlights: • Interfacial characterization of W-Eurofer joints by TEM and nanoindentation has been accomplished. • Microstructural and mechanical properties were in complete agreement. • The combination of both nano-techniques allows to obtain valuable information about braze interfaces. - Abstract: The interfacial characterization of W-Eurofer brazed joints, which could be implemented in the first wall component of the future DEMO nuclear fusion reactor, has been carried out by TEM and nanoindentation. The Eurofer-braze interface is characterized by the formation of two reaction layers formed during the melting stage of the filler in the brazing process, which reported high hardness and modulus values. The obtained microstructure supposes a homogenous transition between the base material and the braze. However, in the W-braze interface a more defined interface is formed, where the presence of an intermetallic transition compound has been identified. The combination of both techniques allows to study the resultant microstructure and to analyze the mechanical response of the phases, which constitute the interface and could be helpful to control the brazing conditions avoiding undesirable brazeability problems.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

Nondestructive ultrasonic characterization of a triple-weld-bead wire arc additively manufactured ER70S-6 S-curved wall

Understanding build-scale microstructural variation in wire arc additive manufacturing (WAAM) of low-carbon steels is essential for ensuring consistent structure–property relationships throughout large components. Conventional destructive characterization techniques, such as scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), are time-intensive and limited to localized regions, making comprehensive evaluation of large WAAM structures challenging. In this study, a nondestructive ultrasonic approach was employed to characterize a 252 mm tall ER70S-6 S-curved WAAM wall produced using a triple-bead deposition strategy. Optical and SEM analysis revealed a repeating dual-region microstructure consisting of uniform polygonal ferrite at melt pool centers and heterogeneous ferrite with coarse and fine grains near melt pool boundaries, attributed to cyclic thermal conditions. Longitudinal ultrasonic backscatter imaging was used to evaluate the continuity of this periodicity along the full build height. The ultrasonic response exhibited a consistent repeating pattern that correlated with the observed layer-wise microstructural variation. X-ray computed tomography confirmed the absence of detectable porosity, indicating that ultrasonic contrast is primarily governed by grain morphology. Overall, the results indicate that longitudinal backscatter ultrasound is a promising nondestructive characterization technique for validating microstructural variations along the s-curved WAAM wall, with significant potential for microstructure optimization and process control.

36 MATERIALS SCIENCE↗