Search Results (36)

Watchmaking manufacturers obtain their bracelet links from machining drawn metal profiles. But, today, there is another process that represents an alternative to manufacture them: metal injection molding using metal powders (MIM technology). This process is less expensive than the machining of drawn metal profiles. The aim of this study was to evaluate the corrosion behavior and the nickel cation release of two stainless steel alloys: 316L MIM and 904L MIM. The general corrosion behavior was evaluated by the rotating electrode technique; the galvanic corrosion measurements were conducted with a 316L AISI bulk coupling partner. The pitting corrosion behavior was evaluated in FeCl3 0.5 M media (according to ASTM G48-11). For comparison, a complementary study was conducted on 316L and 904L bulk alloys. The Ni cation release tests were conducted on 316L and 904L MIM and bulk samples according to EN 1811. Different electrochemical parameters were measured and calculated (open circuit potential, polarization resistance, corrosion current and Tafel slopes, coulometric analysis). Generally, if MIM steels are compared with conventional steels, their corrosion resistance behavior is inferior. In the couplings studied, the galvanic currents generated are very important. The shape of the curves also reveals the presence of localized corrosion phenomena. According to tests in ferric chloride, MIM steels were noted to have inferior behavior compared to conventional steels. MIM type 904L steels are comparable in behavior to conventional type 316L steels. The quantities of nickel released according to EN 1811 were very significant (2 mg cm⁻² week⁻¹ up to 24 mg cm⁻² week⁻¹) and did not meet the requirements of the European directive (0.5 µg cm⁻² week⁻¹). In conclusion, conventional steels studied under the same experimental conditions revealed a better behavior compared to MIM steels independently of the phenomenological parameters chosen. Full article

Electrical discharge machining (EDM) and its variant methods are used to fabricate three-dimensional and complex geometrical features from micro level to nano dimensions. Researchers have successfully experimented with high-strength alloys and composite materials, finding wide applications in defense, automobile, and medical industries to shape precision micro-grooves (straight, tapered, and angular-based). Motion-type EDM methods (when the tool electrode is moving) utilize capabilities to rotate the tool electrode or work material to manufacture grooves (applications included in the micro-electronics sector, aircraft engines, and diffraction gratings). In the present investigation, experimental studies were performed to fabricate the grooves of high-strength NI-based alloy using the EDM electrode (cylindrical in shape) using Taguchi’s L-18 orthogonal array. SEM studies were performed at different magnifications to check and analyze the recast layer formation on the surface of the groove at different parametric settings. The analysis of the effect of input parameters was tested on machine performance responses viz. MRR, EWR, and surface roughness. This was revealed, and the optimum levels of process parameters were analyzed, showing the best surface finish with a maximum metal removal rate after analyzing using SEM. The MRR was found to increase with an increase in the thickness of the disk electrode (0.1–0.6) at all parametric settings. Also, roughness increased with an increase in the current settings from 6 to 12 A. SEM analysis depicts that groove thick ness at the bottom (565 µm) and top of the groove (1.14 mm). Full article

Microelectromechanical system (MEMS) inertial sensors are integral components in a variety of smart electronic devices, most notably MEMS vibrating gyroscopes, which are rotational inertial sensors. The applications of MEMS vibrating gyroscopes range from household appliances to GPS and even to military applications. However, the stability and reliability of these MEMS inertial sensors in space applications still pose challenges. In this research study, we introduce a simple design for a vibrating ring gyroscope with eight semicircular support springs connected to outside-placed anchors. The symmetric design structure with semicircular support springs provides higher sensitivity while minimizing mode mismatch. The design and modelling analysis of the vibrating ring gyroscope was conducted using Ansys 2023 R1. The proposed vibrating ring gyroscope has a ring radius of 1000 µm, a 210 µm radius for the semicircular support springs, a ring and support spring thicknesses of 10 µm, and an area of 80 × 80 µm² for the outside-placed anchors. The vibrating ring gyroscope operates at two identical elliptical-shape resonant modes, one for driving resonance frequency and the other for sensing resonance frequency. Both simulated resonance frequencies were measured at 48.78 kHz and 48.80 kHz. The modelled result achieved a mode mismatch of 0.02 kHz, which can be easily rectified with tuning electrodes. Full article

A new co-rotating electrochemical machining method is presented to machine the complex structure inside annular parts such as flame tubes and aero-engine casings. Due to the unique shape and motion of electrodes, it is difficult to accurately compute the electric field intensity in the machining area. In this paper, the complex electric field model is simplified by conformal transformation, and the analytical solution of electric field intensity is exactly calculated. A material removal model is built on the basis of the electric field model, and the dynamic simulation of the material removal process is realized. The effects of the cathode radius, applied voltage, feed rate and initial interelectrode gap on the interelectrode gap (IEG) and material removal rate (MRR) are analyzed. The simulation results indicate that the MRR is always slightly less than the feed rate in a quasi-equilibrium state, resulting in a slow reduction in IEG. In addition, the final machining state is not affected by the initial IEG, and the MRR in a quasi-equilibrium state is determined by the feed rate. Several comparative experiments were carried out using the optimized processing parameters, in which the MRR and IEG were measured. The convex structures were successfully machined inside the annular workpiece with optimum machining parameters. The experimental results are in good agreement with the theoretical results, indicating that the established model can effectively predict the evolution process of MRR and IEG. Full article

Piezoelectric micromachined ultrasonic transducers (PMUTs) have attracted widespread attention due to their high performance, miniaturization, and easy integration with semiconductor processes. In this paper, a PMUT device based on high-performance and lead-free Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBBT) piezoelectric single-crystal thin films was designed for the application of medical high-frequency ultrasonics. Three-dimensional modeling and analysis of PMUT elements on the proposed structure were performed via the finite element method. The relationship between structure configuration in terms of the top electrode and the cavity shape of the bottom was studied. The PMUT properties and its device performance, including resonant frequency, effective electromechanical coupling factor ($k_{eff}^2$), and the static sensitivity of different device structures, were analyzed. In addition, by rotating the Euler Angle $\gamma$ of the NBBT piezoelectric single-crystal film, the static sensitivity and $k_{eff}^2$ of the model are improved to 1.34 when $\gamma$ is rotated to 45 ± 5°. It was shown that the PMUT using rotated NBBT demonstrated an enhanced relative pulse-echo sensitivity of −46 dB and a bandwidth of 35% when the reflective surface was 200 μm. We conclude that the PMUT in accordance with an NBBT piezoelectric single-crystal film designed by simulation offers a high frequency, larger$k_{eff}^2$, and high sensitivity, which provides application prospects in high-resolution and high-frequency medical ultrasonic imaging. Full article

Efficient oxygen reduction reaction (ORR) electrocatalysts are the key to advancement of solid-state alkaline zinc–air batteries (ZAB). We demonstrate an electrocatalyst, spinel lithium-manganese oxide LiMn₂O₄ (LMO) by a simple hydrothermal method. Scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectra indicate that the as-synthesized LiMn₂O₄ presents nanoscale irregular-shaped particles with the well-known spinel structure. The polarization curve, chronoamperometery curve, and linear scanning voltammograms of rotating disk electrode (RDE) results reveal that the as-synthesized LiMn₂O₄ possesses a higher electrocatalytic activity than that of electrolytic manganese dioxide for the ORR. A solid-state zinc–air cell with LiMn₂O₄ as the air electrode catalyst has a long voltage plateau of discharge and a discharge capacity of 188.4 mAh at a constant discharge current density of 10 mA·cm⁻². In summary, spinel LiMn₂O₄ in which the JT effect enables electron hoping between Mn³⁺ and Mn⁴⁺ can be regarded as an effective robust oxygen reduction catalyst. Full article

The electrophysiological activities of head direction (HD) cells under visual and vestibular input dissociation are important to understanding the formation of the sense of direction in animals. In this paper, we fabricated a PtNPs/PEDOT:PSS-modified MEA to detect changes in the discharge of HD cells under dissociated sensory conditions. The electrode shape was customized for the retrosplenial cortex (RSC) and was conducive to the sequential detection of neurons at different depths in vivo when combined with a microdriver. The recording sites of the electrode were modified with PtNPs/PEDOT:PSS to form a three-dimensional convex structure, leading to closer contact with neurons and improving the detection performance and signal-to-noise ratio of the MEA. We designed a rotating cylindrical arena to separate the visual and vestibular information of the rats and detected the changes in the directional tuning of the HD cells in the RSC. The results showed that after visual and vestibular sensory dissociation, HD cells used visual information to establish newly discharged directions which differed from the original direction. However, with the longer time required to process inconsistent sensory information, the function of the HD system gradually degraded. After recovery, the HD cells reverted to their newly established direction rather than the original direction. The research based on our MEAs revealed how HD cells process dissociated sensory information and contributes to the study of the spatial cognitive navigation mechanism. Full article

Microelectromechanical system (MEMS) devices have gained tremendous attention in the field of smart electronics applications. A MEMS vibrating gyroscope is a rotational inertial sensor that is exhaustively used in many applications, from GPS, household, smart appliances, and space applications. The reliability of MEMS devices for space applications is a big concern. The devices need to be robust in harsh environments. This paper reports a double-ring MEMS vibrating ring gyroscope with sixteen worm-shaped support springs. The inclusion of the two rings with sixteen worm-shaped springs enhances the sensitivity of the gyroscope. The design symmetry and the worm-shaped springs increase the robustness, mode matching, and gyroscopic sensitivity against harsh environments. The design modeling of the gyroscope is investigated using the ANSYSTM software. The design of the vibrating ring gyroscope incorporates two 10 µm thick rings with an outer ring radius of 1000 µm and an inner ring radius of 750 µm. Both rings are attached with sixteen worm-shaped springs, and a centrally placed anchor supports the whole structure with a radius of 260 µm. The proposed gyroscope operates in two identical wine glass modes. The first targeted resonant mode was recorded at 29.07 kHz, and the second mode of the same shape was recorded at 29.35 kHz. There is a low-mode mismatch of 0.38 kHz observed between the two resonant frequencies, which can be resolved with tuning electrodes. The initial modeling results show a good prospect for the design of a vibrating gyroscope for space applications. Full article

In this study we demonstrate a high-performance polarization rotator (PR) based on flat-shaped photonic crystal fiber. The flat surfaces of the fiber are plated on gold films as electrodes, and the core of the structure is filled with liquid crystal. The polarization rotation characteristics of the flat-shaped fiber can be effectively adjusted by applying external voltage. The optical properties are analyzed using the finite element method (FEM). The results show that the magnitude of the modulation voltage is closely related to the thickness of the flat fiber. When the fiber thickness is 20 μm, only 100 V is required to achieve the highest PR performance. In the wavelength of the 1.55 μm band (~200 nm bandwidth), the conversion length of the PR is only 3.99 μm, the conversion efficiency is close to 100%, and the minimum crosstalk value is −26.2 dB. The presented PR, with its excellent performance, might enable promising applications in the communication system and the photonic integrated circuits. Full article

This paper provides numerical and experimental investigations of a ring-shaped piezoelectric 5-DOF robot that performs planar and angular motions of spherical payload. The robot consists of a piezoelectric ring glued on a special stainless-steel ring with three spikes oriented in the radial direction of the ring. The spherical payload is placed on top of the piezoelectric ring and is moved or rotated when a particular excitation regime is used. An alumina oxide ball is glued at the end of each spike of the steel ring and is used as contacting element. The spikes are used to transfer vibrations of the piezoelectric ring to contacting elements and to induce the planar motion of the payload. Additionally, three alumina oxide balls are glued on the top surface of the piezoelectric ring and are used to generate rotational motion of the spherical payload by impacting it. Finally, the top electrode of the piezoceramic ring is divided into six equal sections and is used to control the direction of angular and planar motion of the payload. Numerical modeling of the robot showed that vibration modes suitable for angular and planar motions are obtained at a frequency of 28.25 kHz and 41.86 kHz, respectively. Experimental investigation showed that the maximum angular velocity of the payload is 30.12 RPM while the maximum linear motion of the robot is 29.34 mm/s when an excitation voltage of 200 V_p-p was applied and a payload of 25.1 g was used. Full article

In addition to lubricating and cooling, aero-engine lubricating oil is also a transport medium for wear particles generated by mechanical wear. Online identification of the number and shape of wear particles is an important means to directly determine the wear state of rotating parts, but most of the existing research focuses on the identification and counting of wear particles. In this paper, a qualitative classification method of wear particle morphology based on support vector machine is proposed by using the wear particle capacitance signal obtained by the coaxial capacitive sensing network. Firstly, the coaxial capacitive sensing network simulation model is used to obtain the capacitance signals of different shapes of wear particles entering the detection space of different electrode plates. In addition, a variety of intelligent optimization algorithms are used to optimize the relevant parameters of the support vector machine (SVM) model in order to improve the classification accuracy. By using the processed data and optimized parameters, a SVM-based qualitative classification model for wear particles is established. Finally, the validity of the classification model is verified by real wear particles of different sizes. The simulation and experimental results show that the qualitative classification of different wear particle morphologies can be achieved by using the coaxial capacitive sensing network signal and the SVM model. Full article

A theoretical framework is presented for calculating the polarization, electro-rotation, travelling-wave dielectrophoresis, electro-hydrodynamics and induced-charge electroosmotic flow fields around a freely suspended conducting dimer (two touching spheres) exposed to non-uniform direct current (DC) or alternating current (AC) electric fields. The analysis is based on employing the classical (linearized) Poisson–Nernst–Planck (PNP) formulation under the standard linearized ‘weak-field’ assumption and using the tangent-sphere coordinate system. Explicit expressions are first derived for the axisymmetric AC electric potential governed by the Robin (mixed) boundary condition applied on the dimer surface depending on the resistance–capacitance circuit (RC) forcing frequency. Dimer electro-rotation due to two orthogonal (out-of-phase) uniform AC fields and the corresponding mobility problem of a polarizable dimer exposed to a travelling-wave electric excitation are also analyzed. We present an explicit solution for the non-linear induced-charge electroosmotic (ICEO) flow problem of a free polarized dimer in terms of the corresponding Stokes stream function determined by the Helmholtz–Smoluchowski velocity slip. Next, we demonstrate how the same framework can be used to obtain an exact solution for the electro-hydrodynamic (EHD) problem of a polarizable sphere lying next to a conducting planar electrode. Finally, we present a new solution for the induced-charge mobility of a Janus dimer composed of two fused spherical colloids, one perfectly conducting and one dielectrically coated. So far, most of the available electrokinetic theoretical studies involving polarizable nano/micro shapes dealt with convex configurations (e.g., spheres, spheroids, ellipsoids) and as such the newly obtained electrostatic AC solution for a dimer provides a useful extension for similar concave colloids and engineered particles. Full article

Detailed studies of the electrochemical oxygen reduction reaction (ORR) on catalyst materials are crucial to improving the performance of different electrochemical energy conversion and storage systems (e.g., fuel cells and batteries), as well as numerous chemical synthesis processes. In the effort to reduce the loading of expensive platinum group metal (PGM)-based catalysts for ORR in the electrochemical systems, many carbon-based catalysts have already shown promising results and numerous investigations on those catalysts are in progress. Most of these studies show the catalyst materials’ ORR performance as current density data obtained through the rotating disk electrode (RDE), rotating ring-disk electrode (RRDE) experiments taking cyclic voltammograms (CV) or linear sweep voltammograms (LSV) approaches. However, the provided descriptions or interpretations of those data curves are often ambiguous and recondite which can lead to an erroneous understanding of the ORR phenomenon in those specific systems and inaccurate characterization of the catalyst materials. In this paper, we presented a study of ORR on a newly developed carbon-based catalyst, the nitrogen-doped graphene/metal-organic framework (N-G/MOF), through RDE and RRDE experiments in both alkaline and acidic mediums, taking the LSV approach. The functions and crucial considerations for the different parts of the RDE/RRDE experiment such as the working electrode, reference electrode, counter electrode, electrolyte, and overall RDE/RRDE process are delineated which can serve as guidelines for the new researchers in this field. Experimentally obtained LSV curves’ shapes and their correlations with the possible ORR reaction pathways within the applied potential range are discussed in depth. We also demonstrated how the presence of hydrogen peroxide (H₂O₂), a possible intermediate of ORR, in the alkaline electrolyte and the concentration of acid in the acidic electrolyte can maneuver the ORR current density output in compliance with the possible ORR pathways. Full article

The sliding freestanding layer triboelectric nanogenerator (SF-TENG) is a sustainable power source that can convert mechanical energy from linear or rotating mechanical motion to electrical energy. This paper proposes a double-layer staggered chain teeth TENG. Comparing the staggered electrode TENG and the double-layer staggered electrode TENG, the output voltage difference is relatively small. The electrode of the TENG is designed to the shape of chain teeth, which proves that TENG can be combined with a zipper, and the best distance among chain teeth in the TENG is determined through experiments. Compared with traditional zippers, the double-layer staggered chain teeth TENG can generate electrical energy during the continuous pulling of the zipper. The double-layer staggered chain teeth TENG has good performance. When the external load is 20 MΩ, the maximum output power reaches 20.18 µW. After the rectification and transformation, the generated electricity can light up 30 LED lights or more, and can also supply power to electronic devices. Through the chain teeth array, the open circuit voltage and transfer charge generated by the zipper during the continuous pulling process are improved. The double-layer staggered chain teeth TENG has a good usage environment in life, and this work will provide valuable insights for the development of SF-TENG technology. Full article

A new type of nano-adsorbent zinc-silver nanoparticles ornamented by multi-walled carbon nanotubes (Zn-Ag MWCNT) was efficiently synthesized by double arc discharge using a newly designed rotating cylinder electrode. Zn-Ag MWCNT was characterized by different instrumental methods to get information about the sample shape, size, and crystallinity. Without irradiation, Zn-Ag MWCNT indicated significant potential for elimination against methylene blue (MB) which is dissolved in deionized water. When the adsorbent concentration was 0.1 g/L at normal 8 pH, the Zn-Ag MWCNTs were efficient in removing 97% of the MB from 40 mg/L that was dissolved in water for 10 min. The dye removal activity of (Zn-Ag) decorated MWCNTs was attributed to the influence of silver and zinc nanoparticles on the MWCNTs. Finally, this approach was both cost-effective and efficient. Full article