High-resolution Scanning Research Articles

Thermomechanical and isothermal fatigue properties of MAR-M247 superalloy

Thermomechanical low-cycle fatigue (TMF) tests were performed on polycrystalline cast nickel-based superalloy MAR-M247 under in-phase (IP) and out-of phase (OP) loading in the temperature range of 500–900 °C. A constant heating and cooling rate of 5 °C.s−1 was selected. Furthermore, isothermal low-cycle fatigue (ILCF) tests with the same cycle period as TMF cycle were carried out at the maximal temperature of TMF cycle (900 °C). All tests ran under strain control and fully reversed cycle on solid cylindrical specimens in laboratory air. High resolution scanning electron microscopy and transmission electron microscopy were utilized to characterize the damage mechanism occurring during TMF and ILCF loading. The cyclic deformation and lifetime behaviour as well as damage mechanisms dependent on loading regime were examined. Results show that the TMF loading has a detrimental effect on the lifetime of MAR-M247. Lifetime reduction is most significant under IP loading. The fracture surfaces are characterized by typical striation fields, where the largest spacing between striations was observed for IP loading with prevailing intercrystalline cracking followed by OP and isothermal ILCF loading with transcrystalline crack propagation. To improve discussion of obtained results, experimental data were compared with damage and life prediction models.

Template-assisted electrodeposition of freestanding antimony, tin, and antimony-tin nanowire arrays from an ionic liquid

In the present study, we show the electrochemical synthesis of Sb, Sn, and Sb-Sn nanowire arrays from the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonate ([Py1,4]TfO) via templated-assisted approaches. Commercially available track etched polycarbonate template with a nominal pore diameter of 400 nm was utilized as a template. The nanowires were electrochemically deposited inside the pores of the template; then, a supporting copper layer was electrodeposited on the back side of the template. Subsequently, the template was dissolved with dichloromethane, and the structural morphology of the nanowire structures was explored by high-resolution scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). Freestanding, mechanically stable nanowire arrays of Sb, Sn, and Sb-Sn with an average pore diameter of 400 nm were obtained. The charge/discharge characteristics of the electrodeposited nanowire films were investigated to explore the Li storage capacity of the fabricated electrodes. The results revealed that the electrodeposited nanowire films are promising anode candidates for the future generation of Li-ion batteries.Graphical abstract

Microstructure and mechanical properties of a hypereutectic Al–Si–Cu alloy manufactured by laser powder bed fusion

A novel Al–Si–Cu alloy was designed for additive manufacturing of automotive components, such as pistons and supercharger rotors, requiring a combination of elevated temperature properties and high cycle fatigue strength. The alloy was designed with an Al–Si hypereutectic chemistry to exploit the formation of primary Si nucleants to enable an equiaxed as-printed microstructure during laser powder bed fusion (LPBF). The alloy design space was assessed using a combined integrated computational materials engineering (ICME) approach with melt-spinning experiments to select a chemistry exhibiting primary Si nucleants acting as heterogeneous grain nucleation sites. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) of the LPBF as-printed samples revealed primary Si particles with a fully equiaxed grain structure and no apparent texturing as evaluated using electron backscatter diffraction (EBSD). High-resolution scanning transmission electron microscopy (STEM) revealed sub-micron Si particles and Al2Cu θ-phase precipitates which result in enhanced room and elevated temperature mechanical strength (room temperature: UTS: 449 ± 10 MPa, YS: 336 ± 12 MPa) as compared to commercial Al10SiMg (UTS: 417 ± 3 MPa, YS: 236 ± 6 MPa).

Uncovering the Infection Strategy of Phyllachora maydis During Maize Colonization: A Comprehensive Analysis.

Tar spot, a disease caused by the ascomycete fungal pathogen Phyllachora maydis, is considered one of the most significant yield-limiting diseases of maize (Zea mays) within the United States. P. maydis may also be found in association with other fungi, forming a disease complex that is thought to result in the characteristic fisheye lesions. Understanding how P. maydis colonizes maize leaf cells is essential for developing effective disease control strategies. Here, we used histological approaches to elucidate how P. maydis infects and multiplies within susceptible maize leaves. We collected tar spot-infected maize leaf samples from four different fields in northern Indiana at three different time points during the growing season. Samples were chemically fixed and paraffin-embedded for high-resolution light and scanning electron microscopy. We observed a consistent pattern of disease progression in independent leaf samples collected across different geographical regions. Each stroma contained a central pycnidium that produced asexual spores. Perithecia with sexual spores developed in the stomatal chambers adjacent to the pycnidium, and a cap of spores formed over the stroma. P. maydis reproductive structures formed around but not within the vasculature. We observed P. maydis associated with two additional fungi, one of which is likely a member of the Paraphaeosphaeria genus; the other is an unknown fungi. Our data provide fundamental insights into how this pathogen colonizes and spreads within maize leaves. This knowledge can inform new approaches to managing tar spot, which could help mitigate the significant economic losses caused by this disease.

RAS Dataset: A 3D Cardiac LGE-MRI Dataset for Segmentation of Right Atrial Cavity

The current challenge in effectively treating atrial fibrillation (AF) stems from a limited understanding of the intricate structure of the human atria. The objective and quantitative interpretation of the right atrium (RA) in late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) scans relies heavily on its precise segmentation. Leveraging the potential of artificial intelligence (AI) for RA segmentation presents a promising solution. However, the successful implementation of AI in this context necessitates access to a substantial volume of annotated LGE-MRI images for model training. In this paper, we present a comprehensive 3D cardiac dataset comprising 50 high-resolution LGE-MRI scans, each meticulously annotated at the pixel level. The annotation process underwent rigorous standardization through crowdsourcing among a panel of medical experts, ensuring the accuracy and consistency of the annotations. Our dataset represents a significant contribution to the field, providing a valuable resource for advancing RA segmentation methods.

A study on the oxidative property using thermogravimetric analysis of NiO nanoparticles prepared by a simple wet chemical method

Nanosized NiO particles were synthesised by chemical co-precipitation technique and the particle has been characterized morphologically, elementally, structurally and thermally using High Resolution Scanning Electron Microscopy (HR-SEM), Energy Dispersive X-ray Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). A green precipitated Nickel Oxide Nanoparticles (NiO NPs) was prepared and the size of the particle was found to be 45 nm and the presence of Ni and O elements were confirmed using the elemental analytic tools like EDX and FTIR in which the existence of water molecules was confirmed from the absorption spectrum. The generated sample's crystal structure was face-centered cubic, and Scherer's equation was used to compute its size, which was found to be 43 nm. Crystal characteristics including crystal parameters (a), interatomic distance (dh,k,l), atomic radius (r) and cell volume (Vc) were also calculated. The weight loss observed from TGA curve signifies the oxidative property of NiO NPs and there is a steady increase in the weight difference versus time difference. The calcination temperature of NiO was determined to be 700⁰C via analysis at the TGA curve's peaks. The activation energy (Ea) was determined using Coats-Redfern method by solving the slope of the graph between log[−log(1−α)T2] and 1000T. With respect to its highly effective capacity, which can be seen when treating with an increase in temperature, NiO may be used as an oxidising and reducing agent in oxidation and reduction processes.

The Influence of Carbon on Polytype and Growth Stability of Epitaxial Hexagonal Boron Nitride Films

AbstractBoron nitride (BN) is a promising 2D material as well as a potential wide‐bandgap semiconductor. Chemical vapor deposition (CVD) is commonly used to deposit single layers or thin films of BN, but the deposition process is insufficiently understood at an atomic scale. the CVD of BN is studied using two boron precursors, the organoboranes, triethylborane, and trimethylborane. Using high resolution (scanning) transmission electron microscopy and electron energy loss spectroscopy, this study shows that hexagonal‐BN (h‐BN) nucleates and grows epitaxially for ≈4 nm before it either polytype transforms to rhombohedral‐BN (r‐BN), turns to less ordered turbostratic‐BN or is terminated by a layer of amorphous carbon. this study proposes that the carbon in the organoboranes deposits on the epitaxially growing h‐BN surface and this either leads to the polytype transition to r‐BN, the transition to less ordered BN growth, or complete surface poisoning with carbon terminating BN growth. These results question the use of organoboranes in CVD of epitaxial BN films, and the polytype stability of h‐BN growing on graphene.

Dried Porous Biomaterials from Mealworm Protein Gels: Proof of Concept and Impact of Drying Method on Structural Properties and Zinc Retention.

Dried porous materials can be found in a wide range of applications. So far, they are mostly prepared from inorganic or indigestible raw materials. The aim of the presented study was to provide a proof of concept for (a) the suitability of mealworm protein gels to be turned into dried porous biomaterials by either a combination of solvent exchange and supercritical drying to obtain aerogels or by lyophilization to obtain lyophilized hydrogels and (b) the suitability of either drying method to retain trace elements such as zinc in the gels throughout the drying process. Hydrogels were prepared from mealworm protein, subsequently dried using either method, and characterized via FT-IR, BET volume, and high-resolution scanning electron microscopy. Retention of zinc was evaluated via energy-dispersive X-ray spectroscopy. Results showed that both drying methods were suitable for obtaining dried porous biomaterials and that the drying method mainly influenced the overall surface area and pore hydrophobicity but not the secondary structure of the proteins in the gels or their zinc content after drying. Therefore, a first proof of concept for utilizing mealworm protein hydrogels as a base for dried porous biomaterials was successful and elucidated the potential of these materials as future sustainable alternatives to more conventional dried porous materials.

Sonarlogger: Enabling long-term underwater sonar observations

Coastal seas are under increasing pressure from extreme weather events and sea level rise, resulting in impacts such as changing hydrodynamic conditions, coastal erosion, and marine heat waves. To monitor changes in coastal marine habitats, such as reefs and macrophytes meadows, which add to the resilience of our coasts, consistent, medium- to long-term seafloor observations are needed. This project aims to deliver repeated, high-frequency sonar surveys on a stationary seabed mooring of a specific target area over a period of up to several months. A new stand-alone subsea system, the Sonarlogger, based on a battery pack, low-power logger and a high-resolution scanning sonar, was developed. It allows for long-term deployments with a customisable battery pack, WI-FI download and configurable sleep state. The system has been tested for over 130 days in dynamic coastal environments off the Belgian coast. Combined with auxiliary sensors, such as for measuring currents, waves and turbidity, this system enables comprehensive studies of morphologic changes and changing benthic ecosystems. Moreover, this system has the capacity to provide measurements of coastal environments during storms, where conventional systems may fall short, providing insights into event-based changes of the seafloor.

High Speed Impact Testing of UHMWPE Composite Using Orthogonal Arrays

BackgroundUltra high molecular weight polyethylene composites are fiber based composites used in armor applications. While some characterization has been conducted experimentally, this study varies multiple parameters simultaneously to investigate material response under a wide range of conditions.ObjectiveThis work focuses on characterizing the response of Dyneema® HB26 hard laminate composites under high-speed impacts to examine the influence of plate diameter, clamping pressure, and plate spacing on target performance. Additionally, micro Computer Tomography scans are used to nondestructively evaluate the damage evolution in the targets.MethodsThese scan results are used in concert with more traditional armor performance metrics to evaluate the effect of various parameters using the method of orthogonal array analysis. This technique allows for multiple variables to be investigated in the same test series, saving time and budget while still providing quality results across a range of variables and variable values.ResultsWe conclude that of the parameters investigated, the plate spacing parameter has the largest effect on performance, followed by the plate diameter. Bolt torque was found to not have a significant impact on results, indicating that an edge clamping pressure is not critical to material response. Additionally, by examining the high resolution scans, we can quantify the damage with an effective damage angle and that this angle is a good predictor of performance. ConclusionFinally a damage theory involving the effective bending strength of the plates is discussed as an explanation for all of the results observed in this test series.

A prospective case series to evaluate subcostal nerve injury with high-resolution ultrasound in posterior retroperitoneoscopic adrenalectomy

BackgroundPosterior retroperitoneoscopic adrenalectomy has several advantages over transabdominal laparoscopic adrenalectomy regarding operating time, blood loss, postoperative pain, and recovery. However, postoperatively several patients report chronic pain or hypoesthesia. We hypothesized that these symptoms may be the result of damage to the subcostal nerve, because it passes the surgical area.MethodsA prospective single-center case series was performed in adult patients without preoperative pain or numbness of the abdominal wall who underwent unilateral posterior retroperitoneoscopic adrenalectomy. Patients received pre- and postoperative questionnaires and a high-resolution ultrasound scan of the subcostal nerve and abdominal wall muscles was performed before and directly after surgery. Clinical evaluation at 6 weeks was performed with repeat questionnaires, physical examination, and high-resolution ultrasound. Long-term recovery was evaluated with questionnaires, and photographs from the patients were examined for abdominal wall asymmetry.ResultsA total of 25 patients were included in the study. There were no surgical complications. Preoperative visualization of the subcostal nerve was possible in all patients. At 6 weeks, ultrasound showed nerve damage in 15 patients, with no significant association between nerve damage and postsurgical pain. However, there was a significant association between nerve damage and hypoesthesia (p = 0.01), sensory (p < 0.001), and motor (p < 0.001) dysfunction on physical examination. After a median follow-up of 18 months, 5 patients still experienced either numbness or muscle weakness, and one patient experienced chronic postsurgical pain.ConclusionIn this exporatory case series the incidence of postoperative damage to the subcostal nerve, both clinically and radiologically, was 60% after posterior retroperitoneoscopic adrenalectomy. There was no association with pain, and the spontaneous recovery rate was high.Graphical

Topology selectivity of a conformationally flexible precursor through selenium doping

Conformational arrangements within nanostructures play a crucial role in shaping the overall configuration and determining the properties, for example in covalent/metal organic frameworks. In on-surface synthesis, conformational diversity often leads to uncontrollable or disordered structures. Therefore, the exploration of controlling and directing the conformational arrangements is significant in achieving desired nanoarchitectures. Herein, a conformationally flexible precursor 2,4,6-tris(3-bromophenyl)−1,3,5-triazine is employed, and a random phase consisting of C3h and Cs conformers is firstly obtained after deposition of the precursor on Cu(111) at room temperature to 365 K. At low coverage (0.01 ML) selenium doping, we achieve the selectivity of the C3h conformer and improve the nanopore structural homogeneity. The ordered two-dimensional metal organic nanostructure can be fulfilled by selenium doping from room temperature to 365 K. The formation of the conformationally flexible precursor on Cu(111) is explored through the combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy. The regulation of energy diagrams in the absence or presence of the Se atom is revealed by density functional theory calculations. These results can enrich the on-surface synthesis toolbox of conformationally flexible precursors, for the design of complex nanoarchitectures, and for future development of engineered nanomaterials.

Low-temperature precipitation strengthening of maraging steel 1.2709 produced by powder bed fusion

Research into precipitation hardening in additively manufactured (AM) maraging steel is mainly conducted on the material after several hours of holding at the peak hardening temperatures of 450–500 °C. Lower temperatures are expected to have little to no effect on mechanical properties even after very long holds at these temperatures. This article, however, demonstrates that new precipitates grow and cause a noticeable hardening effect in solution-annealed AM maraging steel after only a 6-hour hold at a temperature of 350 °C. High-resolution scanning and transmission electron microscopy (HRSEM, HRTEM) was used to identify the new precipitates. Very fine coherent microdomains containing mainly nickel and molybdenum layers were found. Particles of a new phase, Al0.5CNi3Ti0.5, were also detected. Additionally, various precipitates were also found in both the as-built and the AM solution-annealed maraging steel samples. Precipitates such as Ni3Ti, Al0.3Ni0.35Ti0.35 and Al2O5Ti, were also observed in the as-built condition. After subsequent solution annealing at 820 °C additional Ni3Mo particles and another type of Ti-rich particles, Ni4Ti3, were further found in the AM steel microstructure. The additional new phases which precipitated during the final hardening at 350 °C caused an 18 % (200 MPa) increase in strength.

Direct observation of a magnetic-field-induced Wigner crystal.

Wigner predicted that when the Coulomb interactions between electrons become much stronger than their kinetic energy, electrons crystallize into a closely packed lattice1. A variety of two-dimensional systems have shown evidence for Wigner crystals2-11 (WCs). However, a spontaneously formed classical or quantum WC has never been directly visualized. Neither the identification of the WC symmetry nor direct investigation of its melting has been accomplished. Here we use high-resolution scanning tunnelling microscopy measurements to directly image a magnetic-field-induced electron WC in Bernal-stacked bilayer graphene and examine its structural properties as a function of electron density, magnetic field and temperature. At high fields and the lowest temperature, we observe a triangular lattice electron WC in the lowest Landau level. The WC possesses the expected lattice constant and is robust between filling factor ν ≈ 0.13 and ν ≈ 0.38 except near fillings where it competes with fractional quantum Hall states. Increasing the density or temperature results in the melting of the WC into a liquid phase that is isotropic but has a modulated structure characterized by the Bragg wavevector of the WC. At low magnetic fields, the WC unexpectedly transitions into an anisotropic stripe phase, which has been commonly anticipated to form in higher Landau levels. Analysis of individual lattice sites shows signatures that may be related to the quantum zero-point motion of electrons in the WC lattice.

High-resolution scanning tunneling microscope and its adaptation for local thermopower measurements in 2D materials

We present the design, fabrication and discuss the performance of a new combined high-resolution Scanning Tunneling and Thermopower Microscope (STM/SThEM). We also describe the development of the electronic control, the user interface, the vacuum system, and arrangements to reduce acoustical noise and vibrations. We demonstrate the microscope’s performance with atomic-resolution topographic images of highly oriented pyrolytic graphite (HOPG) and local thermopower measurements in the semimetal Bi2Te3. Our system offers a tool to investigate the relationship between electronic structure and thermoelectric properties at the nanoscale.

Observation of broad triangular Frank-type stacking faults and characterization of stacking faults with emission wavelengths below 430 nm in 4H–SiC epitaxial layers

Frank-type stacking faults in 4H–SiC epitaxial layers were investigated using room-temperature photoluminescence mapping and high-angle annular dark-field high-resolution scanning transmission electron microscopy. Remarkably, the intrinsic Frank-type stacking fault (5,2) and intrinsic multilayer Frank-type stacking fault (4,2), which have been reported to have elongated triangular shapes to date, were found to have broader triangular shape, which was typical shape of Shockley-type stacking faults. The shaping of stacking faults could be explained based on the directions of the partial dislocations bounding the stacking faults. Formation models for the intrinsic (5,2) and (4,2) stacking faults were proposed. In addition, we observed Frank-type stacking faults (3,2,2,3) and (3,3) and Shockley-type stacking faults (3,3,3,2,3,2) and (3,2,3,3,3,2), which were not reported before. All of these stacking faults were composed with the stacking numbers 2 and 3 in the Zhdanov notation and showed very close characteristic photoluminescence emission wavelengths of 427–428 nm. Formation models for the stacking faults of (3,2,2,3), (3,3), (3,3,3,2,3,2), and (3,2,3,3,3,2) were proposed, also. Based on the proposed formation models of (4,2) and (3,3) stacking faults, formation models for the Frank-type stacking faults (4,1) and (3,2) were discussed. Finally, we pointed out that the (4,1) Frank-type stacking fault should be the intrinsic not the extrinsic fault, and the (3,2) Frank-type stacking fault is the extrinsic fault.

Chiroplasmonic DNA Scaffolded "Fusilli" Structures.

DNA is an ideal template for the design of nanoarchitectures with molecular-like features. Here, we present an optimized assembly strategy for the concatenation of DNA quasi-rings into long scaffolds. Ionic strength, which played a major role during self-assembly, produced the expected high quality only at 15 mM MgCl2. Atomic force microscopy (AFM) characterization showed several micrometer long tubular structures that were used as templates for the positioning of plasmonic nanoparticles (NPs) along a three-dimensional helical path using DNA tethers. As imaged by high-resolution scanning transmission electron microscopy (HR-STEM) and modeled by theoretical calculations, the NPs distributed into a "fusilli" fashion (i.e., a helical pasta shape), displaying chiroptical activity as revealed by a bisignated CD absorption, centered at the plasmon resonance wavelength. The present structures contribute to enrich the ever-developing arena of chiroplasmonic DNA-based nanomaterials and demonstrate that large assemblies are attainable for their future application to develop metamaterials.

Thermal scanning probe and laser lithography for patterning nanowire based quantum devices

Semiconductor nanowire (NW) quantum devices offer a promising path for the pursuit and investigation of topologically-protected quantum states, and superconducting and spin-based qubits that can be controlled using electric fields. Theoretical investigations into the impact of disorder on the attainment of dependable topological states in semiconducting nanowires with large spin–orbit coupling and g-factor highlight the critical need for improvements in both growth processes and nanofabrication techniques. In this work, we used a hybrid lithography tool for both the high-resolution thermal scanning probe lithography and high-throughput direct laser writing of quantum devices based on thin InSb nanowires with contact spacing of 200 nm. Electrical characterization demonstrates quasi-ballistic transport. The methodology outlined in this study has the potential to reduce the impact of disorder caused by fabrication processes in quantum devices based on 1D semiconductors.

Seeing is believing: Correlating optoelectronic functionality with atomic scale imaging of single semiconductor nanocrystals.

A unique on-chip method for the direct correlation of optical properties, with atomic-scale chemical-structural characteristics for a single quantum dot (QD), is developed and utilized in various examples. This is based on performing single QD optical characterization on a modified glass substrate, followed by the extraction of the relevant region of interest by focused-ion-beam-scanning electron microscope processing into a lamella for high resolution scanning transmission electron microscopy (STEM) characterization with atomic scale resolution. The direct correlation of the optical response under an electric field with STEM analysis of the same particle allows addressing several single particle phenomena: first, the direct correlation of single QD photoluminescence (PL) polarization and its response to the external field with the QD crystal lattice alignment, so far inferred indirectly; second, the identification of unique yet rare few-QD assemblies, correlated directly with their special spectroscopic optical characteristics, serving as a guide for future designed assemblies; and third, the study on the effect of metal island growth on the PL behavior of hybrid semiconductor-metal nanoparticles, with relevance for their possible functionality in photocatalysis. This work, therefore, establishes the use of the direct on-chip optical-structural correlation method for numerous scenarios and timely questions in the field of QD research.

Ice-Core Micro-CT Image Segmentation with Dual Stream Spectrum Deconvolution Neural Network and Gaussian Mixture Model

Polar ice sheets, or ice cores, are among the most well-known natural archives that might provide crucial historical details about our planet's previous environment. An important factor in establishing the fundamental characteristics of ice, likes pore close-off, albedo, melt events, is the ice-core microstructure. To engulf these complications Ice-Core Micro-CT Image Segmentation with Dual Stream Spectrum Deconvolution Neural Network and Gaussian Mixture Model (ICMCTS-WSOA-DSSDNN-GMM)is proposed. Initially, micro scale CT images are collect from Alfred Wegener Institute ice-core storage as input. Then,data’s are given to pre-processing. In pre-processing, it enhance image brightness, remove salt pepper noise, crop outer ring (carbon fiber casing) to have only ice particles in image utilizing Federated Neural Collaborative Filtering (FNCF).The pre-processing output is given to segmentation. Here, micro scale CT image is utilized for segmenting high-resolution scans using Gaussian Mixture Model (GMM). After that, the segmented images are given to Dual Stream Spectrum Deconvolution Neural Network optimized with Water Strider Optimization Algorithm for classifying micro scale CT images as sintered snow, compacted firn and bubbly ice. The proposed ICMCTS-WSOA-DSSDNN-GMM method is executed in python. The performance of ICMCTS-WSOA-DSSDNN-GMM approach attains 16.24%, 17.90% and 27.7% high accuracy, 14.04%, 25.51% and 19.31% higher precision and 14.36%, 12.65%, 14.51% higher recall analyzed with existing techniques likes Ice-Core Micro-CT Image Segmentation With Deep Learning and Gaussian Mixture Method (ICMCTS-U-net-GMM), Computer Aided Detection of COVID 19 from CT Images Depend on Gaussian Mixture Method with Kernel Support Vector Machines Classifer (ICMCTS-KNN-GMM) and the Gmmseg: Gaussian mixture based generative semantic segmentation methods(ICMCTS-FCN-GMM) respectively.