Ultra-narrow Gap Research Articles

A General Sol-Gel Route to Fabricate Large-Area Highly-Ordered Metal Oxide Arrays Toward High-Performance Zinc-Air Batteries.

A universal method is demonstrated for the fabrication of large-area highly ordered microporous arrayed metal oxides based on a high-quality self-assembly opal template combined with a sucrose-assisted sol-gel technique. Sucrose as a chelating agent optimizes precursor infiltration and regulates both oxide formation and the melting process of polystyrene templates, thus preventing crack formation during infiltration and calcination. As a result, over 20 metal element-based 3DOM oxides with arbitrary compositions are successfully prepared. Therein, a champion electrocatalyst RuCoOx-IO exhibits outstanding bifunctional oxygen activity with an ultra-narrow oxygen potential gap of 0.598V, and the Zn-air batteries based on RuCoOx-IO air cathode operates for 1380h under fast-charging cycling (50mA cm-2), and reaches a high energy efficiency of 69.5% in discharge-charge cycling. In situ spectroscopy characterizations and density functional theory reveal that the rational construction of Ru─O─Co heterointerface with decoupled multi-active sites and mutual coupling of RuO2 and Co3O4 facilitate interfacial electron transfer, leading to an optimized d-band centers of active Ru/Co and a weakened spin interaction between oxygen intermediates and Co sites, so as to enhance the adsorption ability of *OOH on interfacial Co sites for fast ORR kinetics while favoring the desorption of oxygen intermediates on interfacial Ru during OER.

Overall improvement of macro electrochemical jet milling by utilizing a novel cathode tool with an ultra narrow inter-electrode gap

Electrochemical jet milling (EJM) offers significant benefits for producing workpieces, showcasing various advantages in terms of quality and design flexibility. However, macro-scale EJM currently encounters limitations regarding machining efficiency and surface precision. A critical determinant of these aspects is the inter-electrode gap (IEG), with its optimization presenting an opportunity to enhance both precision and efficiency. Reducing the IEG is particularly desirable as it promises considerable improvements in machining efficiency and surface quality. Nonetheless, achieving a narrower IEG is challenging due to the risk of sparking from excessively high current densities at the cathode tool tips. To address this issue, this study introduces an innovative cathode tool design tailored to exploit the characteristics of electric in EJM. This design strategically removes the energy concentration area. As a result, this advancement allows for an ultra-narrow IEG of 0.05 mm, setting a new benchmark for the narrowest IEG achievable in macro EJM. Employing this novel cathode tool leads to a substantial leap in machining performance at an IEG of 0.05mm. When compared with the conventional machining gap of 0.2mm, the refined 0.05mm IEG not only boosts the material removal rate by an impressive 107% but also enhances surface quality. Specifically, the experimental results showed that the minimum surface roughness produced by the RD cathode tool was reduced by nearly 86.2% than that of the surface produced by the standard cathode tool. Moreover, the overcut area was reduced by nearly 60.1%, and stray corrosion was eliminated.

Visible-Photo-Assisted Phase Switching of Antiferroelectric-to-Ferroelectric Orders in an I3 --Intercalated 2D Perovskite.

Antiferroelectric (AFE) has emerged as a promising branch of electroactive materials, due to intriguing physical attributes stemming from the electric field-induced antipolar-to-polar phase transformation. However, the requirement of extremely high electric field strength to switch adjacent sublattice polarization poses great challenges for exploiting new molecular AFE system. Although photoirradiation is striking as a noncontact and nondestructive manipulation tool to optimize physical properties, optical control of antiferroelectricity still remains unexplored. Here, by adopting light-sensitive I3 - anion into 2D perovskite family, we design a new I3 --intercalated molecular AFE of (t-ACH)2EA2Pb3I10(I3)0.5 ⋅ ((H3O)(H2O))0.5 (1, t-ACH=trans-4-aminomethyl-1-cyclohexanecarboxylate, EA=ethylammonium). The I3 --intercalating gives an ultra-narrow band gap of 1.65 eV with strong absorption. In term of AFE structure, the anti-parallel alignment of electric dipoles results in a large spontaneous polarization of 4.3 μC/cm2. Strikingly, 1 merely shows AFE behaviour in the dark even under ultrahigh voltage, while the field-induced ferroelectric state can be facilely obtained upon visible illumination. Such unprecedented visible-photo-assisted phase switching ascribes to the incorporation of photoactive I3 - anions that reduces AFE-to-ferroelectric switching barrier. This pioneering work on the photo-assisting transformation of ferroic orders paves a way to develop future photoactive materials with potential applications.

Measure of an ultranarrow topological gap via quantum noise

Measure of an ultranarrow topological gap via quantum noise

Model-Based Practically Precise Fabrication of HgSe Quantum Dots toward Their Application in a Long-Wave Infrared Micro Spectrometer.

Quantum dot (QD) passive filters present a simple and low-cost strategy for the micromation of spectrometers. In this field, the consistency between ultranarrow band gap QD fabrication and the precise control of its absorption characteristics is the key-challenge to extend QD spectrometers into the long-wave infrared (LWIR) region. Here, we show the model-based, practically precise fabrication of HgSe QDs as well as their specific spectral responses. Both the theoretical and experimental models of the HgSe QDs r-λ are formulated, which reveals the variation of transmission spectrum with the size of HgSe QDs. Then, the HgSe QDs synthesis parameter-spectral response hyperplane model and neural network model were obtained by using traditional polynomial fitting and machine learning, respectively. We also demonstrate the model-based precise fabrication of HgSe QDs with transmission characteristic peaks within 14 μm. The further simulation also shows that the 255─element QD filter array has the signal-to-noise ratio up to 14.57 dB with detection resolution about 5 cm-1.

Comparison of Microstructure and Mechanical Properties of Ultra-Narrow Gap Metal Active Gas Arc Welded and Narrow Gap Submerged Arc Welded Q235A Low Carbon Steel.

The 18 mm thick Q235A low carbon steel plates were welded via the ultra-narrow gap metal active gas arc welding (ultra-NGMAGW) and narrow gap submerged arc welding (NGSAW), and the microstructure and mechanical properties of the welded joints' area were characterized. The results showed that there is acicular ferrite (AF) in the weld zone of the joint obtained via the ultra-NGMAGW. The AF grains are fine and have a great difference in growth direction, resulting in high local dislocation density. However, there is no AF in the welded joint obtained via the NGSAW. Using numerical simulation analysis of the temperature field distribution and the thermal cycle curve in the welding process of the ultra-NGMAGW, it was found that the mechanism of microstructure evolution is that during the welding process of the ultra-NGMAGW, the heat input is low, the cooling rate is quick, and the residence time in the high temperature region is short. Therefore, pearlite with coarse grains is basically not formed. AF nucleates in different directions with inclusions as the core. The tensile strength of the weld joint obtained via the ultra-NGMAGW is 643 MPa, which corresponds to 139% of that of the base metal, and 132% of that obtained via the NGSAW. The ultra-NGMAGW joints exhibited better tensile strength and higher microhardness than the NGSAW joints, which is mainly due to the existence of AF.

Numerical simulation study on correlation between characteristics of slice tungsten electrode pulsed arc with insulating wall constrain and transverse shrinkage deformation of groove in ultra narrow gap

Numerical simulation study on correlation between characteristics of slice tungsten electrode pulsed arc with insulating wall constrain and transverse shrinkage deformation of groove in ultra narrow gap

Study on mechanism of the effect of Al element on the arc shape and molten pool fluctuation pattern in flux bands constricting arc welding (FBCA)

Herein, to investigate dynamic penetration control in ultra-narrow gap grooves, the effect of Al addition at a fraction of 0.2 %–1 % in flux bands on welding arc shape changes and molten-pool fluctuations in flux bands constricting arc (FBCA) welding is examined via a high-speed camera and side glass observation system. The influence mechanism of Al on weld formation is analyzed based on the weld depth-to-width ratio. Results reveal that as the Al content increases, the profile of the welding arc shifts from a divergent spherical shape to a contracted ellipsoidal shape, and the arc-burning position changes from the middle to the lower section of the groove. In addition, Al changes the side flow morphology of the molten pool from a shallow concave to a deep single-V shape, thus accelerating the molten pool flow and resulting in a humped molten pool. As Al in the flux bands changes the molten-pool Marangoni convection modes, the weld formation is affected significantly. When the Al addition is at 0.80 %, the weld depth-to-width ratio reaches a maximum of 1.32, and the joint presents the best welding quality. Meanwhile, at 0.92 % Al addition, fluctuations in the weld depth-to-width ratio increase, porous slag inclusions are observed, and the welding quality degrades. This occurs because Al3+ vapor is preferentially ionized, deoxidation within the arc induces further contraction of the arc, and the arc force impact on the bottom of the molten pool increases. In addition, Al2O3 is regenerated in the molten pool and accumulates on the surface, thus resulting in the highest levels of flow and solidification in the molten pool. However, when excess Al is added to intensify the molten pool reaction, the weld deteriorates.

Integrating collapsible plasmonic gaps on near-field probes for polarization-resolved mapping of plasmon-enhanced emission in 2D material.

Scanning near-field optical microscopy (SNOM) is an important technique used to study the optical properties of material systems at the nanoscale. In previous work, we reported on the use of nanoimprinting to improve the reproducibility and throughput of near-field probes including complicated optical antenna structures such as the 'campanile' probe. However, precise control over the plasmonic gap size, which determines the near-field enhancement and spatial resolution, remains a challenge. Here, we present a novel approach to fabricating a sub-20 nm plasmonic gap in a near-field plasmonic probe through the controlled collapse of imprinted nanostructures using atomic layer deposition (ALD) coatings to define the gap width. The resulting ultranarrow gap at the apex of the probe provides a strong polarization-sensitive near-field optical response, which results in an enhancement of the optical transmission in a broad wavelength range from 620 to 820 nm, enabling tip-enhanced photoluminescence (TEPL) mapping of 2-dimensional (2D) materials. We demonstrate the potential of this near-field probe by mapping a 2D exciton coupled to a linearly polarized plasmonic resonance with below 30 nm spatial resolution. This work proposes a novel approach for integrating a plasmonic antenna at the apex of the near-field probe, paving the way for the fundamental study of light-matter interactions at the nanoscale.

Weld Cross-Section Profile Fitting and Geometric Dimension Measurement Method Based on Machine Vision

A visual measurement method based on a key point detection network is proposed for the difficulty of fitting the cross-sectional profile of ultra-narrow gap welds and the low efficiency and accuracy of manual measurement of geometric parameters. First, the HRnet (High-Resolution Net) key point detection algorithm was used to train the feature point detection model, and 18 profile feature points in a “measurement unit” were extracted. Secondly, the feature point coordinates are transformed from the image coordinate system to the weld coordinate system, and the weld profiles are fitted by the least squares method. Finally, the measurement system is calibrated with a coplanar linear calibration algorithm to perform pixel distance to actual distance conversion for quantitative detection of geometric dimensions. The experimental results show that the accuracy of the proposed method for key point localization is 95.6%, the mean value of the coefficient of determination R-square for curve fitting is greater than 94%, the absolute error of measurement is between 0.06 and 0.15 mm, and the relative error is between 1.27% and 3.12%. The measurement results are more reliable, and the efficiency is significantly improved compared to manual measurement.

Electrical and Optical Properties of γ-SnSe: A New Ultra-narrow Band Gap Material.

We describe the unusual properties of γ-SnSe, a new orthorhombic binary phase in the tin monoselenide system. This phase exhibits an ultranarrow band gap under standard pressure and temperature conditions, leading to high conductivity under ambient conditions. Density functional calculations identified the similarity and difference between the new γ-SnSe phase and the conventional α-SnSe based on the electron localization function. Very good agreement was obtained for the band gap width between the band structure calculations and the experiment, and insight provided for the mechanism of reduction in the band gap. The unique properties of this material may render it useful for applications such as thermal imaging devices and solar cells.

Thermoelectric properties of monolayer Cu<sub>2</sub><i>X</i>

Two-dimensional (2D) materials with lower lattice thermal conductivities and high figures of merit are useful for applications in thermoelectric (TE) devices. In this work, the thermoelectric properties of monolayer Cu<sub>2</sub>S and Cu<sub>2</sub>Se are systematically studied through first-principles and Boltzmann transport theory. The dynamic stability of monolayer Cu<sub>2</sub>S and Cu<sub>2</sub>Se through elastic constants and phonon dispersions are verified. The results show that monolayer Cu<sub>2</sub>S and Cu<sub>2</sub>Se have small lattice constants, resulting in lower phonon vibration modes. Phonon transport calculations confirm that monolayer Cu<sub>2</sub>Se has lower lattice thermal conductivity (1.93 W/(m·K)) than Cu<sub>2</sub>S (3.25 W/(m·K)) at room temperature, which is due to its small Debye temperature and stronger anharmonicity. Moreover, the heavier atomic mass of Se atom effectively reduces the phonon frequency, resulting in an ultra narrow phonon band gap (0.08 THz) and a lower lattice thermal conductivity for monolayer Cu<sub>2</sub>Se. The band degeneracy effect at the valence band maximum (VBM) of monolayer Cu<sub>2</sub>S and Cu<sub>2</sub>Se significantly increase their carrier effective mass, resulting in higher Seebeck coefficients and lower conductivities under p-type doping. The electric transport calculation at room temperature shows that the conductivity of monolayer Cu<sub>2</sub>S (Cu<sub>2</sub>Se) under n-type doping about 10<sup>11</sup> cm<sup>–2</sup> is 2.8×10<sup>4</sup> S/m (4.5×10<sup>4</sup> S/m), obviously superior to its conductivity about 2.6×10<sup>2</sup> S/m (1.6×10<sup>3</sup> S/m) under p-type doping. At the optimum doping concentration for monolayer Cu<sub>2</sub>S (Cu<sub>2</sub>Se), the n-type power factor is 16.5 mW/(m·K<sup>2</sup>) (25.9 mW/(m·K<sup>2</sup>)), which is far higher than p-type doping 1.1 mW/m·K<sup>2</sup> (6.6 mW/(m·K<sup>2</sup>)). Through the above results, the excellent figure of merit of monolayer Cu<sub>2</sub>S (Cu<sub>2</sub>Se) under optimal n-type doping at 700 K can approach to 1.85 (2.82), which is higher than 0.38 (1.7) under optimal p-type doping. The excellent thermoelectric properties of monolayer Cu<sub>2</sub>S (Cu<sub>2</sub>Se) are comparable to those of many promising thermoelectric materials reported recently. Especially, the figure of merit of monolayer Cu<sub>2</sub>Se is larger than that of the well-known high-efficient thermoelectric monolayer SnSe (2.32). Therefore, monolayer Cu<sub>2</sub>S and Cu<sub>2</sub>Se are potential thermoelectric materials with excellent performances and good application prospects. These results provide the theoretical basis for the follow-up experiments to explore the practical applications of 2D thermoelectric semiconductor materials and provide an in-depth insight into the effect of phonon thermal transport on improvement of TE transport properties.

A cyano-based electron-accepting building block to design n-type conjugated polymers with absorption wavelength of >1000 nm.

There are much fewer n-type conjugated polymers than p-type counterparts because of the lack of strong electron-accepting building blocks. We report a novel strong electron-accepting unit based on a dicyanomethylene unit. The resulting polymers exhibit LUMO energy levels of as low as -4.04 eV and narrow optical gaps with an onset absorption wavelength of 1050 nm. Moreover, the polymers exhibit near-infrared light absorption with good photostability because of their low-lying LUMO/HOMO energy levels.

Development of Ultra-Narrow Gap Submerged Arc Welding

Development of Ultra-Narrow Gap Submerged Arc Welding

Intelligent Seam Tracking of an Ultranarrow Gap During K-TIG Welding: A Hybrid CNN and Adaptive ROI Operation Algorithm

Deep-penetration keyhole tungsten inert gas (K-TIG) welding uses a large current for welding. The extraction of the deviation between the position of the welding torch and the centerline of the weld is the prerequisite for the realization of seam tracking. However, K-TIG welded workpieces are often assembled without a groove and the gap between each weld is super narrow (0.2–1 mm), making it difficult to accurately identify the seam. In addition, traditional methods of identifying seams based on a fixed region of interest (ROI) are likely to lead to seam tracking failures when the type of weld changes. A narrow gap seam tracking algorithm suitable for different weld shapes is developed to address these factors and increase the robustness. To minimize the interference caused by strong arc lights, the welding images are captured by an high dynamic range (HDR) camera. A you only look once (YOLOv5)-based object detection algorithm is used to determine the position of the torch by the center of the keyhole entrance. Then, an image processing algorithm based on the adaptive ROI operation is used to adaptively extract the weld centerline and obtain the weld deviations. The experimental results proved that the welding deviation detected by the algorithm fluctuated within ±0.122 mm and that the average error was within ±0.043 mm. Moreover, the real-time performance of the algorithm can reach up to 45 frames per second (FPS), which is sufficient to meet the real-time and accuracy requirements of the K-TIG seam tracking system.

Influence of Pulsed Current for Heating Characteristic of Groove in Ultra-narrow Gap Welding with Sheet Tungsten Electrode Arc Constricted by Insulating Solid Wall

Influence of Pulsed Current for Heating Characteristic of Groove in Ultra-narrow Gap Welding with Sheet Tungsten Electrode Arc Constricted by Insulating Solid Wall

Numerical Simulation of Temperature Field in Ultra-Narrow Arc Welding of Thick-Walled Steam Turbine Valve Body Material

The welding problems of large and thick plates are becoming more prominent as the application of large-scale and thick-plate metal structures grows. Due to the issue of excessive welding deformation between the 60mm thick steam turbine valve body and the pipe joint, a new process method is employed to connect. In this paper, the welding technology of flux strip confined arc ultra-narrow gap is proposed to carry out welding test on the ZG13Cr9Mo2Co1NiVNbNB cast steel test block of steam turbine valve body material with a thickness of 60 mm. The welding temperature field is measured by means of a K-type thermocouple and numerical simulation. The results show that the thermal cycle curve obtained by the homogeneous body heat source simulation is basically consistent with the thermal cycle curve measured during the experiment, and the simulation results of the molten pool morphology are also consistent with the actual macroscopic morphology of the weld.

Numerical simulation of influence of constraint wall configuration on arc characteristics of sheet tungsten electrode

The sheet tungsten electrode is mainly used in ultra-narrow gap TIG welding (UNGW-TIG) because of its shape characteristics, and the constraint wall can further cool and compress the sheet tungsten electrode arc, improve the arc characteristics and optimize the welding process. In this study, the differences between two-sided constraint sheet tungsten electrode arc and all-sided constraint sheet tungsten electrode arc are compared. The results show that the all-sided constraint wall has a better compression effect on the arc. The effects of constraint height and constraint gap on characteristics of all-sided constraint sheet tungsten electrode arc are further discussed. The constraint height mainly improves the effect of compressed arc by increasing the contact area, while the constraint gap mainly improves the effect of compressed arc by increasing the temperature difference. Finally, the temperature distribution in the space of two-sided constraint sheet tungsten electrode arc is measured by electrostatic probe as experimental verification.

Numerical simulation of the effect of sheet tungsten electrode configuration on arc characteristics in ultra-narrow gap welding

Numerical simulation of the effect of sheet tungsten electrode configuration on arc characteristics in ultra-narrow gap welding

Atomically dispersed cobalt in core-shell carbon nanofiber membranes as super-flexible freestanding air-electrodes for wearable Zn-air batteries

• This work represents the first-ever attempt of introducing specific carbon nanofiber-based membranes which is truly flexible via electrospun technique. • Due to good integration of Zn/Co-ZiFs and fiber precursor, the Co-N 4 sites are atomically dispersed in the crosslinked flexible nanofibers. • A correlation between flexibility and high-efficiency of air-electrodes for Zn-air batteries is elucidated, opening a new area of structure-based design and development of carbon nanofibers by core-shell electrospinning approach. Highly efficient and flexible air-electrodes play a vital role in the development of solid-state metal-air batteries for wearable electronic devices. However, the practical application of air-electrodes is impeded by the multistep synthesis and poor flexibility. Herein, metal/nitrogen co-doped carbon nanofiber membranes are synthesized by integrated core-shell electrospun, in which Co-N 4 sites are atomically dispersed in the porous shell and specific carbon nanofibers with super-flexibility form backbones in the core. Owing to a high specific surface area, a 3D porous network structure and atomically dispersed Co-N 4 active sites, as-prepared membranes demonstrate a remarkable bifunctional electrocatalytic performance towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a low potential gap of 0.719 V. Furthermore, the flexible Zn–air battery featuring a freestanding air-electrode by as-fabricated membranes displays an outstanding open-circuit voltage (1.461 V), a high peak power density (60.3 mW cm −2 ) and an ultra-narrow and stable discharge-charge voltage gap of 0.61 V under different bending angles, which are among the best values reported for self-supported flexible Zn-air batteries. This work paves a new way to prepare integrated freestanding air-electrodes as power sources for flexible electronic devices. .