Edge Defects Research Articles

The effect of printing edge defects on the electrodynamic characteristics of the patch antennas

The influence of repeatability and random edge defects on the frequency dependence of parameter S11 characteristics of a square patch antenna is considered. A certain maximum size of the edge defect, which does not affect its characteristics, is defined. By analogy with a round patch-antenna, it is shown that the dependence of the parameter S11 characteristics on the inverse radius of curvature is linear making it relatively easy to estimate the influence of conformal antenna bending radius on the characteristics.

Fourier phase analysis combined with a fusion scheme in long pulse thermography

Fourier phase analysis (FPA) is a common routine in long pulse thermography (LPT). However, the change of appearance in maximum phase difference in the Fourier domain caused by different depths of defects results in low contrast images with fuzzy defect edges, limiting its application majorly. In this work, the detection capability of FPA is studied by modelling the image sequence length as a function of the defect depth, thereby quantifying the expected image sequence length for inspecting the defects at a specific depth and then, a strategy for selecting the optimal image sequence length is proposed by establishing the relationship between the maximum phase difference and the image sequence length. Followed by an image fusion procedure, the phase difference map with high-contrast defect edges can be obtained from the optimal image sequence. In addition, we show that the precooling treatment before detection is an effective way to improve the image quality for LPT. Experiments have been conducted in identifying defects in a typical glass fiber reinforced polymer (GFPR) with size of 200 × 150 × 6 mm3, where continuous thermal excitation for 100 s was provided by a pair of 1 kW halogen lamps and the images were recorded by an infrared camera with wavelength band of 8–14 μm. The resulting phase difference maps clearly present the edges of all defects with a signal-to-noise ratio greater than 43 dB, demonstrating the effectiveness of the proposed method in improving the image quality in LPT.

Mixed-biomass engineering achieves multi-doped highly-disordered hierarchical flower-like hard carbon for advanced potassium-ion battery

Potassium-ion batteries (PIBs) have emerged as a significant technology for large-scale energy storage. With merits of high abundance, sustainability, and low cost, hard carbons are employed as promising anodes for PIBs, yet distorted carbon lattice induces sluggish conductivity and structural degradation, posing key challenges of low power performance and inferior life span. Here, we proposed a mixed-biomass strategy to design a multi-doped flower-like carbon micro-sphere with major doping of N and trace doping of P and S (NPS-FCM) for advanced PIBs operation. The mixed-biomass engineering achieved inherently rich heteroatoms’ doping and highly disordered hierarchical configuration simultaneously. The NPS-FCM material with expanded lattice spacing, larger specific area, and abundant edge defects and pores, offers robust rate property, and impressive cycle life (1000 cycles with 0.147 ‰ capacity decay per cycle). The potassium-ion full cell (NPS-FCM//PTCDA) was also implemented to show a high median-voltage of 1.78 V and steady cycling. Density functional theory calculation convinced the upgraded electronic conductivity and lowered adsorption energy for potassium storage. This work highlights the importance of mixed-biomass’ cooperation to provide pivotal guidance for sustainable and advanced electrodes for next-generation energy storage.

Defect enhancement method for ZrO2-bearing spherical surface representation based on complete defect stitching and self-defined background balancing algorithm

To address the problems of difficulty in extracting complete defects and high interference of surface background in the process of ZrO2 bearing ball defect detection. A method of ZrO2 bearing ball surface representation defect enhancement based on complete defect stitching and self-defined background balance algorithm is proposed. To determine the location of complete defects, we propose a scanning and acquisition scheme for sub-aperture images and quickly stitch the edges of sub-aperture images. The image feature point gradient definition is optimized, and a less error Euclidean distance finding method is used for feature point matching. The stitched complete defect image is smooth and has high pixel accuracy. The background feature layer of the complete defect image is extracted for background gray leveling, and this process is introduced into the γ-value calculation process. The γ setting allows the image to be self-defined enhancement, outputting a fully defective image with a balanced background and outstanding defects. The average gradient is reduced by more than 90% after complete defect image enhancement, and the information entropy is preserved by about 40%. The defect edges of the image are intact, and the fine texture of the defect features is preserved.

Synergistic activation of peroxymonosulfate by intrinsic defect and graphitic N of N, P co-doped carbon microspheres for BPA degradation

Doping nonmetallic heteroatoms into carbonaceous materials is a proven strategy for enhancing peroxymonosulfate (PMS) activation in the degradation of endocrine-disrupting compounds (EDCs). Understanding the role of heteroatom doping defects and intrinsic defects (topological, vacancies, or edge defects) on PMS activation is crucial for designing more efficient carbon catalysts. Herein, we synthesized nitrogen (N) and phosphorus (P) co-doped carbon microspheres (NPCs) through the pyrolysis of aminophosphonic acid resin (D418) precursors and utilized them to activate PMS for bisphenol A (BPA) degradation. The pyrolysis temperature was found to regulate the type and degree of defects, as well as the configuration of N and P. NPC-1000 (pyrolysis temperature at 1000 °C) exhibited the highest reaction rate constant (k) (1.20 × 10−1 min−1) with the lowest N and P doping defects and the highest intrinsic defect intensity resulting from the removal of N and P during pyrolysis. Density functional theory (DFT) calculations and correlation analysis between defect sites and k suggest that the adsorption of PMS was facilitated by graphitic N-coordinated C and intrinsic defect sites rather than P doping defect sites, resulting in the degradation of BPA through electron transfer and radical mechanisms, specifically superoxide radicals (O•–2). Excess halide anions led a significant increase of k with only a limited formation of trichloromethane (TCM) (disinfection byproducts) in presence of 100 mM Cl−. This research offers fundamental insights into constructing intrinsic defects through regulating heteroatom configuration, intending to enhance the catalytic activity of metal-free materials.

Magnon boundary states tailored by longitudinal spin–spin interactions and topology

Since longitudinal spin–spin interaction is ubiquitous in magnetic materials, it is very interesting to explore the interplay between topology and longitudinal spin–spin interaction. Here, we examine the role of longitudinal spin–spin interaction on topological magnon excitations. Remarkably, even for single-magnon excitations, we discover topological edge states and defect edge states of magnon excitations in a dimerized Heisenberg XXZ chain and their topological properties can be distinguished via adiabatic quantum transport. We uncover topological phase transitions induced by longitudinal spin–spin interactions whose boundary is analytically obtained via the transfer matrix method. For multi-magnon excitations, even-magnon bound states are found to be always topologically trivial, but odd-magnon bound states may be topologically nontrivial due to the interplay between the transverse dimerization and the longitudinal spin–spin interaction. For two-dimensional spin systems, the longitudinal spin–spin interaction contributes to the coexistence of defect corner states, second-order topological corner states and first-order topological edge states. We propose an experimental scheme to realize and measure the magnon boundary states in superconducting qubits. Our work opens an avenue for exploring topological magnon excitations and has potential applications in topological magnon devices.

Visualized and Nondestructive Quality Identification of Two-Dimensional MoS2 Based on Principal Component Analysis.

To date, the common quality characterizations for MoS2 are inefficient or cause irreversible damage to the samples, which have limited scalability and low throughput. Here, we propose a visualized and nondestructive approach to evaluate the quality of MoS2 based on the PCA machine learning method. Through PCA processing of PL mapping, the CVD grown MoS2 with different edge defect densities can be well distinguished. Furthermore, six twin GBs along the sulfur zigzag direction of the six pointed MoS2 stars are also successfully identified. To verify the correctness of the identification results, we measured the lifetime mapping and thermal expansion coefficient of the synthesized MoS2 samples. It is found that the high quality MoS2 samples have a shorter carrier lifetime (∼0.291 ns) and lower thermal expansion coefficient (∼2.03 × 10-5K-1). Therefore, our work offers a new approach to evaluate the quality of MoS2 to drive their practical application.

Autologous Mesenchymal Stromal Cells Immobilized in Plasma-Based Hydrogel for the Repair of Articular Cartilage Defects in a Large Animal Model.

The treatment of cartilage defects in trauma injuries and degenerative diseases represents a challenge for orthopedists. Advanced mesenchymal stromal cell (MSC)-based therapies are currently of interest for the repair of damaged cartilage. However, an approved system for MSC delivery and maintenance in the defect is still missing. This study aimed to evaluate the effect of autologous porcine bone marrow MSCs anchored in a commercially available polyglycolic acid-hyaluronan scaffold (Chondrotissue®) using autologous blood plasma-based hydrogel in the repair of osteochondral defects in a large animal model. The osteochondral defects were induced in twenty-four minipigs with terminated skeletal growth. Eight animals were left untreated, eight were treated with Chondrotissue® and eight received Chondrotissue® loaded with MSCs. The animals were terminated 90 days after surgery. Macroscopically, the untreated defects were filled with newly formed tissue to a greater extent than in the other groups. The histological evaluations showed that the defects treated with Chondrotissue® and Chondrotissue® loaded with pBMSCs contained a higher amount of hyaline cartilage and a lower amount of connective tissue, while untreated defects contained a higher amount of connective tissue and a lower amount of hyaline cartilage. In addition, undifferentiated connective tissue was observed at the edges of defects receiving Chondrotissue® loaded with MSCs, which may indicate the extracellular matrix production by transplanted MSCs. The immunological analysis of the blood samples revealed no immune response activation by MSCs application. This study demonstrated the successful and safe immobilization of MSCs in commercially available scaffolds and defect sites for cartilage defect repair.

Visualizing Ribbon-to-Ribbon Heterogeneity of Chemically Unzipped Wide Graphene Nanoribbons by Silver Nanowire-Based Tip-Enhanced Raman Scattering Microscopy.

Graphene nanoribbons (GNRs), a quasi-one-dimensional form of graphene, have gained tremendous attention due to their potential for next-generation nanoelectronic devices. The chemical unzipping of carbon nanotubes is one of the attractive fabrication methods to obtain single-layered GNRs (sGNRs) with simple and large-scale production. The authors recently found that unzipping from double-walled carbon nanotubes (DWNTs), rather than single- or multi-walled, results in high-yield production of crystalline sGNRs. However, details of the resultant GNR structure, as well as the reaction mechanism, are not fully understood due to the necessity of nanoscale spectroscopy. In this regard, silver nanowire-based tip-enhanced Raman spectroscopy (TERS) is applied for single GNR analysis and investigated ribbon-to-ribbon heterogeneity in terms of defect density and edge structure generated through the unzipping process. The authors found that sGNRs originated from the inner walls of DWNTs showed lower defect densities than those from the outer walls. Furthermore, TERS spectra of sGNRs exhibit a large variety in graphitic Raman parameters, indicating a large variation in edge structures. This work at the single GNR level reveals, for the first time, ribbon-to-ribbon heterogeneity that can never be observed by diffraction-limited techniques and provides deeper insights into unzipped GNR structure as well as the DWNT unzipping reaction mechanism.

Impact of edge defects on the synaptic characteristic of a ferromagnetic domain-wall device and on on-chip learning

Topological-soliton-based devices, like the ferromagnetic domain-wall device, have been proposed as non-volatile memory (NVM) synapses in electronic crossbar arrays for fast and energy-efficient implementation of on-chip learning of neural networks (NN). High linearity and symmetry in the synaptic weight-update characteristic of the device (long-term potentiation (LTP) and long-term depression (LTD)) are important requirements to obtain high classification/regression accuracy in such an on-chip learning scheme. However, obtaining such linear and symmetric LTP and LTD characteristics in the ferromagnetic domain-wall device has remained a challenge. Here, we first carry out micromagnetic simulations of the device to show that the incorporation of defects at the edges of the device, with the defects having higher perpendicular magnetic anisotropy compared to the rest of the ferromagnetic layer, leads to massive improvement in the linearity and symmetry of the LTP and LTD characteristics of the device. This is because these defects act as pinning centres for the domain wall and prevent it from moving during the delay time between two consecutive programming current pulses, which is not the case when the device does not have defects. Next, we carry out system-level simulations of two crossbar arrays with synaptic characteristics of domain-wall synapse devices incorporated in them: one without such defects, and one with such defects. For on-chip learning of both long short-term memory networks (using a regression task) and fully connected NN (using a classification task), we show improved performance when the domain-wall synapse devices have defects at the edges. We also estimate the energy consumption in these synaptic devices and project their scaling, with respect to on-chip learning in corresponding crossbar arrays.

Laser Ablation of the Flexible Graphite: A New Way to Create a Graphene‐Based Flexible Substrate

The morphological and structural changes of an ablated flexible graphite in air and acetone ablation environments are studied here. From field emission scanning electron microscopy images, vertically aligned graphene nanosheets are found on the surface of ablated target in acetone. Measured ablation depth values for the ablated target in water are generally higher than those for the ablated target in air. X‐ray diffraction analysis reveals that the (002) peak position and full‐width at half‐maximum of this peak in the ablated flexible graphite in the air increase. The gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, i.e., the bandgap of the ablated target, indicating that the energy bandgap of the ablated target in two ablation media increased compared to the nonirradiated target. Raman analysis from different points of the surface of the ablated target in both ablation media demonstrates the presence of bulk defects on the ablated target in the air, instead the edge defects are found for the ablated target in acetone. From Raman spectra, there are no single‐layer graphene nanosheets pinned on the surface of the target in acetone.

Microstructure regulation of carbon nitrides for electrochemical nitrogen fixation

The electrochemical synthesis ammonia from nitrogen fixation utilizing sustainable electric energy to realize ammonia (NH3) production under ambient conditions. Herein, we introduce a microstructure regulation strategy to improve the electrochemical nitrogen reduction reaction (eNRR) performance of carbon-nitrogen solid materials (CNs). The CN-Ami, CN-Urea and CN-Mel were obtained under high temperature solid state reaction with 3-amino-1,2,4-triazole, urea and melamine as organic molecular precursors, respectively. Three CNs show great differences in their morphologies and microstructures. Where the CN-Ami has numerous heptazine fragments and more terminal CN sites compared to CN-Urea and CN-Mel. And CN-Ami exhibits the best eNRR performance in both of activity and selectivity among three CNs, the maximum production rate of NH3 is 10.2 μg−1 mg−1cat and Faraday efficiency of NH3 is 20.3% under the potential of 0 V vs reversible hydrogen electrode (RHE). The ammonia production rate remained initial 85.9% during the 6 cycles eNRR tests. Finally, the edge defect of heptazine (C3) is proved as the catalytic active site of NRR by theoretical calculations.

Microwave and template assisted synthesis of atomically dispersed Co–N2 sites on carbon spheres for Fenton-like reaction

Recently, single atomic metals supported on carbon materials have attracted great interests because of their high catalytic activity and stability in peroxymonosulfate (PMS)-based Fenton-like process. Herein, we propose a convenient strategy to synthesize Co single atoms supported on nitrogen-doped carbon spheres (Co@MNC) via microwave treatment. The microwave irradiation can simultaneously induce the formation of carbon defects and immobilize the Co single atoms in N doped carbon support in a few minutes. The obtained Co@MNC can activate PMS for efficient catalytic oxidation of organic pollutants. The radical quenching tests and electron paramagnetic resonance (EPR) verify that Co (IV)-oxo species, 1O2, and O2•− are responsible for the remediation of organic pollutants. Density functional theory (DFT) calculations confirm that unique and low coordinated Co–N2 on void or edge defects are favorable for PMS adsorption. The electrons will then transfer from Co atoms to adsorbed PMS via the bonded N. Co (IV)-oxo species and other ROSs are therefore generated for pollutants degradation. This work provides a fast method for the synthesis of single atom catalysts for efficient Fenton-like reactions.

Co9S8 with core-shell structure supported S/N co-doped carbon nanosheets for effective bifunctional electrocatalysts for rechargeable Zn-air battery

A new S/N-containing Co(II) complex was synthesized by hydrothermal synthesis, and a uniformly dispersed porous carbon was successfully synthesized by carbonized nanocomposites. The prepared catalyst-a exhibited excellent electrochemical performance being as air cathode in a constructed rechargeable Zn-air battery. After a long-term galvanostatic discharge–charge durability test at 5 mA cm−2 over 166 h, the potential difference between the discharge and charge processes was only 0.65 V and the corresponding voltaic efficiency was as high as 64.7%. The active sites such as the M−N,S/C groups, the metallic oxides, the N/S-dopant and the surfae and edge defects cooperatively improve the oxygen electrocatalysis.

Synergetic influence of nitrogen-doped species and hollow microporous structure on surface active sites of carbonaceous catalysts for oxygen reduction reaction of Zn-air battery

The development of metal-free carbon catalysts towards oxygen reduction reaction has focused on their surface active sites multiplied by heteroatom doping and/or pore adjustment. Herein, to coordinate nitrogen doping and pore structure is uncovered to expect highly comparable properties of the carbons to those of commercial Pt/C catalysts. N-doped porous carbons have been fabricated by a ready and collaborative strategy in two-step pyrolysis. The first is to pyrolyze only a raw citrate forming porous carbons with micro-, meso-, or macro-porous structure. Subsequent cyanoguanidine thermolysis induces gaseous nitrogen doping to generate edge defects. Especially, the hollow microporous architecture gives rise to large specific surface area and relatively high catalytic activity of the carbon catalysts (denoted as N-CK). Furthermore, theoretical calculations indicate meta-positional dual-N doped sites with the carbon combining graphitic N and pyridinic N (Gn-C-Py) show a minimum overpotential of 0.39 V. Such a catalyst under the synergistic effect of high-active N-doped species and hollow microporous architecture enables its Zn-air batteries to deliver a superior peak power density of 99.9 mW cm−2 vs. 95.7 mW cm−2 for those using commercial Pt/C. Considering the comprehensive comparability, the N-CK catalysts in a hollow microporous construction possess great feasibility for practical applications.

Antiferromagnetic Spin-Ordered Topology of Surface Functionalized Sb and Bi Monolayer Nanoflakes

Abstract Scale effect and topological frustration have been found to induce magnetic ordering in graphene-like nanoflakes. Based on triangular nanoflakes, the chemically surface-modified Sb and Bi monolayer nanotopological structures are proposed as spintronic logic gates, and their first-principles spin-polarized electron-structure calculations are performed to provide a theoretical basis for developing a new generation of ultrafast spin devices. The net spin of surface-functionalized Sb and Bi monolayer triangular nanoflakes mainly originates from the topological edge-states, exhibiting a sufficiently large spin bandgap, thus enabling stable large spin magnetic moments even under conditions of internal or edge defects and room-temperature electron excitation. The double-triangular nanoflakes of surface-functionalized Sb and Bi monolayers exhibit two stable spin configurations: ferromagnetic coupling and antiferromagnetic coupling. These configurations can serve as elementary variables for spin logic gates. Even at a linear scale as small as 2 nm, the spin coupling energy remains greater than 120 meV, and the error rate decreases below 1×10-5 at room temperature, demonstrating the spin logic gates of triple triangular nanoflakes protected by scattering-prohibited topology.

Enhanced UV Light‐Emission of Zinc‐Phosphate‐Hydrate Hydrothermally‐Grown on Cu Metal Substrates for Opto‐Electronic Applications

AbstractIn the present study, polycrystalline films of layered zinc phosphate hydrate are produced by a facile, low‐temperature single‐step hydrothermal fabrication method on top of Cu metal substrates. Despite containing structural water, the as‐grown films remain crystalline, chemically stable, and electrically conductive. The photoluminescence spectrum obtained at room‐temperature reveals the presence of a spectrally narrow, high‐intensity ultraviolet band that consists of two Gaussian peaks at ≈377 and 383 nm and a UV‐to‐visible peak emission intensity ratio of ≈5.3. The electrical charge‐transport properties remain Ohmic for electric fields of up to ≈2 kV m−1 and temperature (T) range of ≈223–368 K. The electrical conductivity is further found to vary exponentially with the inverse temperature, and the thermal activation energy, Ea is 285 ± 8 meV. A moderate UV‐vis photoconduction effect is registered and assigned to light‐assisted electronic transitions that involve near‐band edge defect states. This study can potentially open a door to the engineering and deployment of water‐based compounds with advanced, semiconducting‐like attributes in short‐wavelength opto‐electronic devices.

Structural Design and Simulation of a Multi-Channel and Dual Working Condition Wafer Defect Inspection Prototype.

Detecting and classifying defects on unpatterned wafers is a key part of wafer front-end inspection. Defect inspection schemes vary depending on the type and location of the defects. In this paper, the structure of the prototype is designed to meet the requirements of wafer surface and edge defect inspection. This prototype has four inspection channels: scattering, reflection, phase, and contour, with two working conditions: surface and edge inspection. The key structure of the prototype was simulated using Ansys. The simulation results show that the maximum deformation of the optical detection subsystem is 19.5 μm and the fundamental frequency of the prototype is 96.9 Hz; thus, these results meet the requirements of optical performance stability and structural design. The experimental results show that the prototype meets the requirements of the inspection sensitivity better than 200 nm equivalent PSL spherical defects.

Reopenable clip-over-the-line method for closing large mucosal defects following colorectal endoscopic submucosal dissection: A feasibility study.

Background and study aims Complete closure of large defects after colorectal endoscopic submucosal dissection (ESD) can be problematic, especially in challenging areas or lesions larger than half the lumen circumference. We report a reopenable clip-over-the-line method for such defects and aim to investigate its feasibility through a case series. Patients and methods We retrospectively evaluated data from 30 consecutive patients who underwent ESD with defect closure using the reopenable clip-over-the-line method between October 2020 and September 2022. This method requires the first clip-with-line grasp of the oral side's defect edge and muscle layer. The next reopenable clip (with a line fed through a hole in the reopenable clip tooth) is placed on the opposing mucosal defect edge and muscle layer. This process is repeated until complete closure. The primary study outcome was the rate of complete mucosal defect closure. We also reported post-procedure bleeding or perforation. Results The median dimensions of the resected specimens were 45 mm (range, 35-70) by 39 mm (range, 29-60). Complete closure was achieved for all defects, including nine rectal defects, of which three bordered the anal verge. Of the 30 defects included in this study, nine were larger than half the lumen circumference. The median closure time was 25 minutes (range, 14-52), and the median clip number was 17 (range, 9-42). No post-procedure bleeding or perforation occurred. Conclusions The reopenable clip-over-the-line method is a feasible technique for the complete closure of large colorectal defects after endoscopic submucosal dissection, regardless of location.

Electrochemical Crosslinking of Alginate-Towards Doped Carbons for Oxygen Reduction.

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na2S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na2S treated/untreated samples. The most positive onset potential (-0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e- reduction pathway at low overpotentials and shifted towards complete 4e- reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering.