Search Results (35)

In this work, research on liquid-based resistive switching devices is carried out, using bottom printable electrodes fabricated from Silver (Ag) paste and silver nitrate (AgNO₃) solution. The self-crossing I-V curves are observed and repeatedly shown by applying 100 sweep cycles, demonstrating repeatability and stability. This liquid device can be refreshed by adding extra droplets of AgNO₃ so that self-crossing I-V hysteresis with up to 493 dual sweeps can be obtained. The ability to be refreshed by supplying a new liquid solution demonstrates an advantage of liquid-based memristive devices, in comparison to their solid counterparts, where the switching layer is fixed after fabrication. The switching mechanism is attributed to Ag migration in the liquid, which narrows the gap between electrodes, giving rise to the observed phenomenon. The devices further show some synaptic properties including excitatory post-synaptic current (EPSC) and potentiation-depression, presenting opportunities to utilize the devices in mimicking some functions of biological neurons. The simplicity and cost-effectiveness of these devices may advance research into fluidic memristors, in which devices with versatile forms and shapes could be fabricated. Full article

To address the challenge of dynamic monitoring during grouting operations in coal mine fault zones under pressurized mining, this study proposes the Borehole–Tunnel Joint Resistivity Method (BTJRM). By integrating three-dimensional (3D) electrode arrays in both tunnels and boreholes with 3D resistivity inversion technology, this approach enables fully automated underground data acquisition and real-time processing, facilitating comprehensive dynamic monitoring of grout propagation. A case study was conducted on a coal mine fault grouting project, where tunnel and borehole survey lines were deployed to construct a 3D cross-monitoring network, overcoming the limitations of traditional 2D data acquisition. Finite volume method and quasi-Gauss–Newton inversion algorithms were employed to analyze dynamic resistivity variations, enhancing spatial resolution for detailed characterization of grout migration. Key findings include: (1) Grout diffusion reduced resistivity by 10%, aligning with electrical response patterns during fracture-filling stages; (2) 3D inversion reveals that grout propagates along the principal stress axis, forming a “Y”-shaped low-resistivity anomaly zone that penetrates the fault structural block and extends into roadway areas. The maximum planar and vertical displacements of grout reach 100 m and 40 m, respectively. Thirty days post-grouting, resistivity recovers by up to 22%, reflecting the electrical signature of grout consolidation; (3) This method enables 3D reconstruction of grout diffusion pathways, extends the time window for early warning of water-conducting channel development, and enhances pre-warning capabilities for grout migration. It provides a robust framework for real-time sealing control of fault strata, offering a novel dynamic monitoring technology for mine water inrush prevention. The technology can provide reliable grouting evaluation for mine disaster control engineering. Full article

Oxide dispersion-strengthened (ODS) alloys demonstrate enhanced mechanical properties at elevated temperatures and show potential as next-generation powder materials for additive manufacturing. These alloys can mitigate defects such as micropores and cracks by regulating solidification and grain growth behaviors during the additive manufacturing process. This study investigates the fabrication technology for ODS Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy powder to achieve uniform oxide distribution within the alloy powders. Thermodynamic calculations were employed to determine the optimal Ti6242–Y₂O₃ composition for in situ gas atomization, ensuring complete dissolution of the oxide in the Ti6242 molten metal and subsequent reprecipitation upon cooling. A rod-shaped ingot was produced via vacuum arc melting, resulting in coarse Y₂O₃ precipitating along the grain boundaries. The powder was fabricated through an electrode induction gas atomization method, and the ODS Ti6242 powder exhibited a spherical shape and a smooth surface. Cross-sectional analysis revealed the uniform distribution of Y₂O₃ oxide particles, measuring several tens of nanometers in size, within the alloy powder. This research demonstrates the successful synthesis of oxide-integrated ODS Ti6242 alloy powder through the in situ gas atomization method, potentially advancing the field of additive manufacturing for high-temperature applications. Full article

The present work presents an innovative marine sensing robotics device based on piezoelectric cantilever-integrated micro-electro-mechanical systems (MEMSs) modeled on fish lateral lines. The device comprises 12 cantilevers of different shapes and sizes in a cross-shaped configuration, embedded between molybdenum (Mo) electrodes in a piezoelectric thin film (PbTiO₃, GaPO₄). It has the advantage of a directional response due to the unique design of the circular cantilevers. In COMSOL software 5.5, we designed, modeled, and simulated a piezoelectric device based on a comparative study of these piezoelectric materials. Simulations were performed on cantilever microstructures ranging in length from 100 µm to 500 µm. These materials perform best when lead titanate (PbTiO₃) is used. A maximum voltage of 4.9 mV was obtained with the PbTiO₃-material cantilever with a displacement of 37 µm. A laser Doppler vibrometer was used to measure the resonance frequency mode and displacement. Our simulations and experiments were in good agreement. Its performance and compactness allow us to envision its employment in underwater acoustics for monitoring marine cetaceans and ultrasound communications. In conclusion, MEMS piezoelectric transducers can be used as hydrophones to sense underwater acoustic pulses. Full article

To investigate the impact of electrode structure on Electrical Stimulation Therapy (EST) for chronic wound healing, this study designed three variants of flexible microelectrodes (FMs) with Ag-Cu coverings (ACCs), each exhibiting distinct geometrical configurations: hexagonal, cross-shaped, and serpentine. These were integrated with PPY/PDA/PANI (3/6) (full name: polypyrrole/polydopamine/polyaniline 3/6). Hydrogel dressing comprehensive animal studies, coupled with detailed electrical and mechanical modeling and simulations, were conducted to assess their performance. Results indicated that the serpentine-shaped FM outperformed its counterparts in terms of flexibility and safety, exhibiting minimal thermal effects and a reduced risk of burns. Notably, FMs with metal coverings under 3% demonstrated promising potential for optoelectronic self-powering capabilities. Additionally, simulation data highlighted the significant influence of hydrogel non-uniformity on the distribution of electrical properties across the skin surface, providing critical insights for optimizing EST protocols when employing hydrogel dressings. Full article

The present investigation focuses on the design and mathematical modeling of a microelectromechanical (MEMS) mode-localized based sensor/actuator system. This device incorporates a sensitive clamped–clamped shallow arch microbeam with an initial curvature shaped to resemble one of the first two symmetric and asymmetric modes of free oscillations of a clamped–clamped beam. The analysis reveals that with a suitable arrangement of the initial shape of the device flexible electrode and a proper tuning of the maximum initial rise and the actuating dc load enables the transition to display certain bistable behavior. This could be a better choice to build a device with a large stroke. Furthermore, the generated data showed the occurrence of mode-veering, indicating a coupling between the concerned symmetric and asymmetric modes of vibrations, and offering the possibility for such a device to be used as a mode-localized MEMS-based sensor utilizing veering and crossing phenomena. Indeed, where a certain energy is exchanged between symmetric and asymmetric modes of a microbeam, it can be utilized to serve as a foundation for the development of a new class of highly precise resonant sensors that can capture, with a certain level of precision, any of the sensed signal amplitudes. Full article

Cross-borehole electrical resistivity tomography (CHERT) technology has been implemented in field-scale CCS/CCUS (carbon capture and storage/carbon capture, utilization and storage) projects. It is highly desirable to investigate how to optimize the design of the ERT electrode arrays and corresponding working schemes for both laboratory experiments and field applications. A CHERT system was developed for laboratory experiments of CO₂ geological storage applications. An optimization method was established for optimizing the structure of electrode arrays and corresponding working schemes. The developed CHERT system was calibrated systematically to determine the measurement range and accuracy of electrical impedance. Laboratory experiments were designed and implemented to validate the performance of the developed CHERT system. It has been illustrated that: (1) It is an essential step to optimize the structure of electrode arrays and corresponding working schemes of CHERT according to the real application background. The optimization method based on finite-element modelling provides an effective means for designing a field-scale CHERT system. (2) The quality of the images inverted from the CHERT data is highly dependent on the working schemes and specific modes, which is closely related to the size of the data sets used for the inversion. The AM-BN scheme is recommended due to the better uniformity of the resultant sensitivity field and application to larger borehole spacing. (3) Based on the calibration, the measurement range of the developed CHERT system can be determined as 100 Ω to 4.5 kΩ with an error limit of 1.5%. The maximum relative errors of the impedance magnitude and phase angle are 5.0% and 7.0%, respectively. Based on the test results the location of the CO₂-bearing objects can be identified accurately. The shapes of the tested objects present distortion to some extent, but this can be alleviated by selecting working modes with a larger size of data set. Full article

Electrochemical machining (ECM) has become more prevalent in titanium alloy processing. However, the presence of the passivation layer on the titanium alloys significantly impacts the performance of ECM. In an attempt to overcome the passivation effects, a high-temperature electrolyte or the addition of halogen ions to the electrolyte has been used. Still, it often results in compromised machining accuracy and surface roughness. This study applied laser and shaped tube electrolytic machining (Laser-STEM) for titanium alloy drilling, where the laser was guided to the machining zone via total internal reflection. The performance of Laser-STEM using different types of electrolytes was compared. Further, the effects of laser power and pulse voltage on the machining side gap, material removal rate (MRR), and surface roughness were experimentally studied while drilling small holes in titanium alloy. The results indicated that the use of passivating electrolytes improved the machining precision, while the MRR decreased with an increase in laser power during Laser-STEM. The MRR showed an increase while using aggressive electrolytes; however, at the same time, the machining precision deteriorated with the increase in laser power. Particularly, the maximum feeding rate of 6.0 mm/min for the tool electrode was achieved using NaCl solution as the electrolyte during Laser-STEM, marking a 100% increase compared to the rate without the use of a laser. Moreover, the model and equivalent circuits were also established to illustrate the material removal mechanisms of Laser-STEM in different electrolytes. Lastly, the processing of deep small holes with a diameter of 1.5 mm, a depth of 38 mm, and a surface roughness of Ra 2 µm was achieved via Laser-STEM without the presence of a recast layer and heat-affected zones. In addition, the cross-inner flow channels in the titanium alloys were effectively processed. Full article

The effects of electrochemical aging on the mechanical properties of electrodes in lithium-ion batteries are challenging to measure and are largely unknown. Mechanochemical degradation processes occur at different scales within an electrode and understanding the correlation between the degradation of mechanical properties, electrochemical aging, and morphological changes is crucial for mitigating battery performance degradation. This paper explores the evolution of mechanical and electrochemical properties at the layer level in a Ni-rich positive electrode during the initial stages of electrochemical cycling. The investigation involves complementary cross-section analyses aimed at unraveling the connection between observed changes on both macroscopic and microscopic scales. The macroscopic constitutive properties were assessed using a U-shaped bending test method that had been previously developed. The compressive modulus exhibited substantial dependency on both the porous structure and binder properties. It experienced a notable reduction with electrolyte wetting but demonstrated an increase with cycling and aging. During the initial stages of aging, electrochemical impedance spectra revealed increased local resistance near the particle–electrolyte interface. This is likely attributable to factors such as secondary particle grain separation and the redistribution of carbon black. The swelling of particles, compression of the binder phase, and enhanced particle contact were identified as probable factors adding to the elevation of the elastic modulus within the porous layer as a result of cycling. Full article

As a surface-strengthening technology, electro-spark deposition (ESD) is widely used in the strengthening and repair of key components of high-end equipment. In this paper, a fusion and solidification model of ESD coating is established. The method of heat–fluid–solid interaction is adopted to simulate the material’s flow and fusion process in the droplet dropping into the molten pool. The distribution law of the coating-matrix material inside the coating was studied. Through the heat transfer between the molten material and the matrix material, the condensation and solidification process of the coating-matrix material is simulated, the temperature change in the coating area during the solidification process is analyzed, and the solidification law of the molten material is studied. The results show that the deposition time reaches 80 μs, and the content of electrode material at the bottom of the molten pool reaches 4.5%. The content of electrode material in the upper region of the material gushing out of the molten pool is higher than that in the bottom region. The material outside the molten pool solidifies first, and the molten material in the molten pool gradually solidifies from the bottom up; the shape of the solidification interface is similar to the boundary of the molten pool. Through the single-point deposition experiment of electro-spark deposition, the surface morphology of the deposition point was observed. The depth of the concave part of the contour can reach 16 μm. The difference between the two contour curves in the horizontal direction is not much; the error of the diameter is about 4%. The element distribution of the surface and the section of the deposition point are analyzed. The diffusion distance in the depth direction of the coating is about 4μm, and the transverse diffusion distance inside the coating is 364 μm. The error is 7.6% compared with the experimental results. The cross-section structure of the deposition point was observed, and the error between the experimental results and the simulation results in diameter is about 11%. It was found that the material distribution in the sedimentary area is basically consistent with the simulation results, and the simulation results are verified from the side. Full article

In this study, a dissimilar material joining of high-strength steel sheet and aluminum alloy using die- and punch-shaped electrodes was investigated. First, when resistance spot welding was performed using die- and punch-shaped electrodes, it is shown that the joint underwent large plastic deformation and that the deformation state changed as the current value was varied. Next, the IMC condition under the appropriate current condition revealed that relatively thin IMCs of 2 μm or less were distributed across the entire joining interface. Finally, the cross-tension strength of the joints was significantly improved compared to conditions using conventional R-type electrodes. Full article

Manufacturing of dies, molds, and their allied components requires the machining of holes with different profiles. Electric discharge machining (EDM) die-sinking is a crucial process used in the dies and molds manufacturing industry. By nature, EDM die-sinking is a relatively slow process in terms of material removal rate (MRR) and there are high amounts of tool material loss in terms of tool wear rate (TWR) which directly influence dimensional accuracies and surface roughness (SR). Therefore, the process is continuously evolving to address these limitations. The present research is aligned in this direction such as to bring improvements in MRR, TWR, and SR through modifications to the conventional electrode design and its geometrical parameters. Traditional designs of EDM electrodes have a uniform cross-section through the tool’s entire length and have only one geometrical parameter, i.e., the tool’s cross-section. To improve the EDM performance, traditional designs are completely modified by introducing several geometrical parameters such as relief angles, land thickness, cross-sectional area, shank height, circular relief, and non-circular relief, etc. Electrode designs are employed to mill non-circular profiles including triangular, square, and hexagonal shaped holes. The EDM performance measures strongly depend on the tool’s geometrical parameters (design type, relief angle, land thickness), machining profile (circular, square, triangle, hexagon), as well as the height/depth of the machining feature. By selecting proper tool designs and corresponding geometrical parameters, the EDM performance measures can be improved significantly. Full article

Features of the nanosecond discharge development in a non-uniform electric field are studied experimentally. High spatial resolution imaging showed that thin luminous tracks of great length with a cross-section of a few microns are observed against the background of discharge glow in air and argon. It has been established that the detected tracks are adjacent to brightly luminous white spots on the electrodes or in the vicinity of these spots, and are associated with the flight of small particles. It is shown that the tracks have various shapes and change from pulse to pulse. The particle tracks may look like curvy or straight lines. In some photos, they can change their direction of movement to the opposite. It was found that the particle’s track abruptly breaks and a bright flash is visible at the break point. The color of the tracks differs from that of the spark leaders, while the bands of the second positive nitrogen system dominate in the plasma emission spectra during the existence of a diffuse discharge. Areas of blue light are visible near the electrodes as well. The development of glow and thin luminous tracks in the gap during its breakdown is revealed using an ICCD camera. Physical reasons for the observed phenomena are discussed. Full article

The study was performed to determine the optimum flushing condition for electrical discharge machining (EDM) of functional material titanium VT6 obtained by plasma cladding with a thermal cycle. Copper is used as an electrode tool (ET) to machine functional materials. The optimum flushing flows are analyzed theoretically by using ANSYS CFX 20.1 software which is also validated by an experimental study. It was observed that while machining the functional materials to adepth of 10 mm or more, the turbulence fluid flow dominates when nozzle angles are 45° and 75°, consequently drastically affecting the quality of flushing and the performance of the EDM. For the highest machining performance, the nozzles should be at an angle of 15° relative to the tool axis. The optimum flushing at deep hole EDM process minimizes the occurrence of debris deposition on tool electrodes, thus facilitating stable machining of functional materials. The adequacy of the obtained models was confirmed experimentally. It has been established that EDM of a hole with a depth of 15 mm, an intense accumulation of sludge, is observed in the processing zone. There arebuild-ups exceeding 3 mm in cross-section after EDM. This build-up leads to a short circuit and a reduction in surface quality and productivity. It has been proven that not correct flushing leads to intensive wear of the tool and a change in its geometric shape and, accordingly, to a decrease in the quality of EDM. Full article

This work presents a novel, highly sensitive, and directional piezoelectric cantilever-based micro-electro-mechanical system (MEMS) device conceived using a biomimetic approach of a fish’s lateral line system for marine sensing robotics. The device will consist of twelve cantilevers with different lengths in a cross-shaped configuration made with a piezoelectric thin film (PZT, ZnO, BaTiO₃) embedded between the top and bottom metals, Platinum (Pt) and Aluminum (Al), used as electrodes. This unique design of cantilevers in circular shapes has the advantage of directional response. A comparative study of these piezoelectric materials was performed analytically through the finite element method to design, model, and simulate our device in COMSOL software. Cantilever microstructures were simulated with lengths ranging from 100 to 1000 mm. The results show that PZT has the best performance with these materials. The maximum potential voltage was shown as 1.9 mV using the PZT material cantilever with 29 µm displacement. Full article