Conductive Research Articles

Safety hysteresis comparator design for transient overvoltage detection

This research introduces a safety hysteresis comparator that detects transient overvoltage in the track circuit relay interlocking of railway signaling system. This overvoltage is caused by voltage faults transmitted through the electric conductor on the track feed unit to the receiver equipped with the track relay, which acts as the occupied track circuit controller. The circuit was designed using safety system design principles and concepts. Findings illustrated that the transient overvoltage detection of the safety hysteresis comparator in the track circuit activated when the input voltage (Vin) was higher than the high hysteresis signal level (Vhyst_H). When Vin was less than low hysteresis signal level (VVhyst_L), the output voltage (Vo) state was low. Otherwise, it was high. The hysteresis voltage was 4.4 V. The installation of the transient overvoltage detector in the track circuit was to monitor the transient overvoltage fault in the track circuit and to confirm that the hysteresis comparator was in the safety failure mode, which was the safety function for the track circuit to be compliant with the IEC 61800-5-2 standard to ensure the system stability and reliability. It would maximize the performance of the controlling function and commanding of train arrangement of State Railway of Thailand (SRT).

Deep Learning Assisted Linear Sampling Method for the Reconstruction of Perfect Electric Conductors

Deep Learning Assisted Linear Sampling Method for the Reconstruction of Perfect Electric Conductors

Al-Cu intermetallic phase growth in hybrid metal extrusion & bonding welds exposed to isothermal annealing or direct current cycling

Joining of aluminium (Al) to copper (Cu) is of great interest to power generation, transportation and electronic industry. However, dissimilar metal joining often promotes intermetallic phase formation at the joined interface, which in redundancy can cause mechanical degradation and increased electrical resistance. The welding technique hybrid metal extrusion & bonding (HYB) is proven capable of joining dissimilar metals with a total intermetallic phase layer thickness <▪. To test how Al-Cu HYB joints perform as electrical conductors, a 6101 Al alloy HYB-welded to Cu is exposed to heat treatment at ▪ or cycling of direct current density up to ▪. In-depth micro- and nanostructure characterisation by (scanning) transmission electron microscopy and atom probe tomography are used to describe the structure and chemistry of the formed intermetallic phases.The Al-Cu HYB joints exhibited resilience against intermetallic phase growth during isothermal heat treatment or exposure to electric current. However, a non-symmetry is observed dependent on the current direction, creating voids in Cu near, and in the intermetallic layers when the current goes from Al to Cu. Detailed microstructure characterisation unveils Si and Mg in the intermetallic phase layers. Their origin and role in intermetallic phase growth are discussed.

Prospective cold metal working and analysis of deformation susceptibility of CuMg alloys with high magnesium content

Metal alloys designated for cold metal working exhibit much higher strength properties than pure materials due to solid-solution hardening. However, with the increase of mechanical properties its plasticity and workability decreases. Constant development and demand in this area has led to research on many copper alloys, such as copper alloys with high content of magnesium which were never tested before. The limitations regarding cold metal working of CuMg alloys is the main objective of this paper. Here we show that the tested materials exhibit much higher mechanical properties than currently used as electric conductors and carrying-conducting equipment materials such as pure copper, aluminum, M63 brass or CuNiSi alloy. The results were obtained using Hollomon relation, Considére criterion, Gubkin method and hardness measurements. It lead to assessing the prospective cold metal working of CuMg alloys with 2 wt% of magnesium up to 4 wt% of magnesium. The test range included upsetting with 10–50% of cold deformation. It provided the results on evolution of mechanical properties and deformability of tested alloys. Additional information was provided based on the alloys subjected to 50% of strain. The results have proven that as the amount of magnesium increased so did the assessed values, however, it was also linked with increasing friction coefficient. Measured hardness was 2 times higher and calculated Ultimate Tensile Strength (UTS) was even 2.5 times higher in reference to pure copper in the as-cast state. However, with magnesium content at 3.6 wt% or higher, the elevated amount of α + β phase causes brittleness making it impossible to subject these materials to cold metal working processes. We anticipate our assay to be a starting point for more sophisticated models and experimental research concerning cold metal working processes of CuMg alloys of high-strength, which may lead to developing novel and promising set of alloys.

Feedback cooling of an insulating high-Q diamagnetically levitated plate

Levitated systems in vacuum have many potential applications ranging from new types of inertial and magnetic sensors through to fundamental issues in quantum science, the generation of massive Schrödinger cats, and the connections between gravity and quantum physics. In this work, we demonstrate the passive, diamagnetic levitation of a centimeter-sized massive oscillator, which is fabricated using a method that ensures that the material, though highly diamagnetic, is an electrical insulator. Electrical conductors moving in a magnetic field experience eddy damping—which can severely reduce their motional quality factor. By chemically coating a powder of microscopic graphite beads with silica and embedding the coated powder in high-vacuum compatible wax, we form a centimeter-sized thin square plate which magnetically levitates over a checkerboard magnet array. The insulating coating reduces eddy damping by almost an order of magnitude compared to uncoated graphite with the same particle size. These plates exhibit a different equilibrium orientation from pyrolytic graphite due to their isotropic magnetic susceptibility. We measure the motional quality factor to be Q∼1.58×105 for an approximately centimeter-sized composite resonator with a mean particle size of 12 μm. Furthermore, we apply delayed feedback to cool the vertical motion of frequency ∼19 Hz and achieve center-of-mass temperature decrease by three orders of magnitude.

Computational multiscale modelling of material interfaces in electrical conductors

Material interfaces occur at various length scales and may exhibit significantly different properties than the surrounding bulk. Motivated by their importance for electrical engineering applications such as wire bonds and electrically conductive adhesives, the focus of the present work is on material interfaces in electrical conductors. In order to approximate the physical interphase (of finite thickness) as a (zero-thickness) cohesive zone-type interface in macroscale simulations, scale-bridging relations are established that relate the apparent electro-mechanical interface properties to the underlying microstructure. A finite element-based implementation is discussed with particular focus lying on the efficient calculation of the flux-type macroscale quantities and the associated generalised algorithmic consistent tangent stiffness tensors. Analytical solutions are derived for validation purposes and representative boundary value problems are studied.

Reversibly Sticking Metals and Graphite to Hydrogels and Tissues.

We have discovered that hard, electrical conductors (e.g., metals or graphite) can be adhered to soft, aqueous materials (e.g., hydrogels, fruit, or animal tissue) without the use of an adhesive. The adhesion is induced by a low DC electric field. As an example, when 5 V DC is applied to graphite slabs spanning a tall cylindrical gel of acrylamide (AAm), a strong adhesion develops between the anode (+) and the gel in about 3 min. This adhesion endures after the field is removed, and we term it as hard-soft electroadhesion or EA[HS]. Depending on the material, adhesion occurs at the anode (+), cathode (-), or both electrodes. In many cases, EA[HS] can be reversed by reapplying the field with reversed polarity. Adhesion via EA[HS] to AAm gels follows the electrochemical series: e.g., it occurs with copper, lead, and tin but not nickel, iron, or zinc. We show that EA[HS] arises via electrochemical reactions that generate chemical bonds between the electrode and the polymers in the gel. EA[HS] can create new hybrid materials, thus enabling applications in robotics, energy storage, and biomedical implants. Interestingly, EA[HS] can even be achieved underwater, where typical adhesives cannot be used.

MOF/MXene-loaded PVA/chitosan hydrogel with antimicrobial effect and wound healing promotion under electrical stimulation and improved mechanical properties

Electrical stimulation modulates cell behavior and influences bacterial activity, so highly conductive, antimicrobial hydrogels are suitable for promoting wound healing. In this study, highly conductive and antimicrobial Ti3C2Tx (MXene) hydrogels composed of chitosan and poly(vinyl alcohol) and AgCu- H2PYDC MOF were developed. In PVACS/MOF/MXene (PCMM) hydrogels, the MXene layer acts as an electrical conductor. The electrical conductivity is 0.61 ± 0.01 S·cm−1. PCMM hydrogels modulate cell behavior and provide ES antimicrobial capacity under ES at 1 V. The metal ions of MOF form coordination with chitosan molecules and increase the cross-linking density between chitosan molecules, thus improving the mechanical properties of the hydrogel (tensile strength 0.088 ± 0.04 MPa, elongation at break 233 ± 11 %). The PCMM gels had good biocompatibility. The PCMM hydrogels achieved 100 % antibacterial activity against E. coli and S. aureus for 12 h. 1 V electrical stimulation of PCMM hydrogel accelerated the wound healing process in mice by promoting cell migration and neovascularization, achieving 97 ± 0.4 % wound healing on day 14. The hydrogel dressing PCMM-0.1 with MOF addition of 0.1 % had the best wound healing promoting effect and which is a promising dressing for promoting wound healing and is a therapeutic strategy worth developing.

Scattering from a semi‐elliptical cavity with arbitrary orientation placed in a perfect electric conductor plane

AbstractA semi‐analytic solution for scattering from a semi‐elliptical cavity with arbitrary orientation placed in a perfect electric conductor plane is suggested. By imposing the boundary conditions at an elliptical border, three independent equations containing the Mathieu functions series are extracted. Finally, the solution of the problem is reduced to the solution of a simple system of linear equations by using Mathieu function addition theorem and the orthogonal properties of the angular Mathieu functions. Some examples are presented to demonstrate the reliability and the accuracy of the proposed solution.

Prediction of new 212 M2AB2 borides as a promising candidate for future engineering: DFT calculations

The elemental diversity is critical for identifying ternary MAB phases with exceptional properties by tuning bonding types and strength between constitutive atoms. The interactions between M and A atoms significantly impact the physical and chemical properties of MAB phases. M2AB2 (where M = Hf, Zr; A = Ga, Ge) was studied using first-principles density functional theory (DFT). Lattice constants (a, c) and internal coordinates have been found after optimization. The lattice parameters in terms of structure exhibit conformity with findings from earlier research. The electronic band structure (EBS) density of states (DOS) and density of states (DOS) have been determined. According to the band structures and density of states investigation, these compounds are electrical conductors. The elastic constants were computed using the stress-strain method. The computed elastic constants and phonon dispersion patterns support this newly found compound's mechanical and dynamical stability. The isotropic elastic moduli bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (v), and Vickers hardness (Hv) have been explored within the framework of the Voigte-Reusse-Hill approximation. Specific heat capacity, Debye temperature, entropy, Helmholtz free energy, and internal energy changes of M2AB2 (where M = Hf, Zr; A = Ga, Ge) compounds were investigated using thermodynamic characteristics. The minimum thermal conductivity (Kmin) and melting temperature (Tm) of the compounds have also been computed to assess whether they are suitable as thermal barrier coating (TBC) materials or for high-temperature applications. These compounds' optical properties have been studied, demonstrating their usefulness as coating materials for reducing solar heat absorption. The examined physical characteristics of M2AB2 (where M = Hf, Zr; A = Ga, Ge) are contrasted with those of comparable 212 and 211 MAB phases.

Analysis of Sliding Vibration of an Electric Shoegear Against a Conductor Rail in Medium- and Low-Speed Maglev Trains

In recent years, medium- and low-speed maglev trains have been put into use in China. It was discovered during testing that the electric shoegear and conductor rail system generate significant vibration and noise when the electric shoegear passes through expansion and intermediate joints. By analyzing the sound pressure level (SPL) of the noise signal, it was found that the A-weighted SPL of the noise was between 77.83 dBA and 91.80 dBA, when the maglev trains were running normally, which reached the level of annoyance. Based on the theory of self-excited frictional vibrations, the finite element models of an electric shoegear and conductor rail system (shoe–rail system) were established. The main frequency of the vibration signal calculated by the transient dynamic analysis method was 1510.05 Hz. The self-excited frictional vibrations of the system were further studied using the complex eigenvalue analysis (CEA), and the causes of the noise are analyzed. The results show that the system has unstable vibration when the friction coefficient was greater than or equal to 0.21. The parameter sensitivity analysis showed that the slip shoe material of the electric shoegear, vertical damping of the suspension device, and tuned mass damper (TMD) structure have an important influence on the generation of vibration and noise of the system. Installing an appropriately tuned mass damper structure can suppress or eliminate the unstable vibration of the system.

Bioresorbable molybdenum temporary epicardial pacing wires

Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Occasionally, TEPW cannot be mechanically extracted and remain in the thorax, where they may rarely cause serious complications like migration and infection. We aim to develop bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. In the present study, we demonstrate a completely bioresorbable design using molybdenum (Mo) as electric conductor and the resorbable polymers poly(D, L-lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) for electrically insulating double-coating. We compared the pacing properties of these Mo TEPW demonstrators to conventional steel TEPW in Langendorff-perfused rat hearts and observed similar functionality. In vitro, static immersion tests in simulated body fluid for up to 28 days elucidated the degradation behaviour of uncoated Mo strands and the influence of polymer coating thereon. Degradation was considerably reduced in double-coated Mo TEPW compared to the uncoated and the PLGA-coated condition. Furthermore, we confirmed good biocompatibility of Mo degradation products in the form of low cytotoxicity in cell cultures of human cardiomyocytes and cardiac fibroblasts. Statement of significanceTemporary pacing wires are routinely implanted on the heart surface to treat rhythm disturbances in the days following cardiac surgery. Subsequently, these wires are to be removed. When removal attempts are unsuccessful, wires are cut at skin level and the remainders are left inside the chest. Retained fragments may migrate within the body or become a centre of infection. These complications may be prevented using resorbable pacing wires. We manufactured completely resorbable temporary pacing wires using molybdenum as electrical conductor and assessed their function, degradation and biological compatibility. Our study represents an important step in the development of a safer approach to the treatment of rhythm disturbances after cardiac surgery.

Synthesis and characterization of graphene oxide as dielectric material for parallel plate capacitor

Graphite acts as an electrical conductor due to the delocalization of electrons between the surfaces. Graphene oxide (GO) is produced by using graphite via the Hummers method. Reduced GO (rGO) is a form of GO where the oxygen content has been reduced due to chemical, thermal, and other processes. In this study, we have produced a prototype of capacitors containing the synthesized rGO with variation of the rGO mass, i.e.: 0 g., 0,2 g; and 0,8 g. Than we compare the capacitance values obtained from the capacitors using a multitester. Characterizations of the rGO are conducted using XRD, UV-Vis, and FTIR. The results of the UV-Vis test show peak at a wavelength of 300 nm indicating absorption of rGO. The XRD test shows a transition from GO to rGO in an amorphous phase. Finally, the FTIR tests produce transmittance bands from the functional groups of CO2, CO, and OH. This paper shows that the capacitance values of the capacitor using rGO material is greater than using graphite material. It means that rGO is capable of storing more charges than graphite. The highest capacitance value is obtained for the capacitor with 0.2 g rGO, i.e.: 165,02 µF.

Solving Surface-volume Integral Equations for PEC and Inhomogeneous/Anisotropic Materials with Multibranch Basis Functions

Multibranch basis functions have been confirmed to be effective for local refinement of domain decomposition methods in the application of solving surface and volume integral equations. Surface-volume integral equations (SVIEs) are applied for solving the hybrid electromagnetic scattering problems involving perfect electric conductors (PEC) and dielectrics, especially inhomogeneous and anisotropic media. In this paper, multibranch Rao-Wilton-Glisson basis functions (MB-RWGs) are applied in conjunction with multibranch Schaubert-Wilton-Glisson basis functions (MB-SWGs) for solving the SVIEs. Block diagonal preconditioners (BDPs) are used to accelerate the iteration convergence based on generalized minimum residual (GMRES) algorithms. The numerical results demonstrate the accuracy of the multibranch basis functions in solving SVIEs, and also show that proper BDPs can accelerate the iteration convergency.

Anharmonic lattice dynamics dominated ion diffusion in γ-Li3PO4

Understanding the influences of lattice dynamics on ionic transport holds the potential to shed light on advanced strategies for designing ionic conductors. However, their utilization remains infrequent due to a limited grasp of anharmonic lattice dynamics within ionic conductors. Herein, we focused on the anharmonic lattice dynamics of γ-Li3PO4, a prototype material for lithium superionic conductor, by combining x-ray diffraction, in situ Raman spectra and first principles calculation. We found that the diffusion process of Li-ion is primarily determined by two Raman modes, with one responsible for the activity of Li-ion and the other dominating the diffusion process. The two Raman modes all show strong anharmonicity and decay into three acoustical phonon modes even in low-temperature region. Our findings indicate that the diffusivity in ionic conductors can be increased by phonon engineering through driving the specific phonons without necessarily changing the compound chemistry.

Resorbable conductive materials for optimally interfacing medical devices with the living.

Implantable and wearable bioelectronic systems are arising growing interest in the medical field. Linking the microelectronic (electronic conductivity) and biological (ionic conductivity) worlds, the biocompatible conductive materials at the electrode/tissue interface are key components in these systems. We herein focus more particularly on resorbable bioelectronic systems, which can safely degrade in the biological environment once they have completed their purpose, namely, stimulating or sensing biological activity in the tissues. Resorbable conductive materials are also explored in the fields of tissue engineering and 3D cell culture. After a short description of polymer-based substrates and scaffolds, and resorbable electrical conductors, we review how they can be combined to design resorbable conductive materials. Although these materials are still emerging, various medical and biomedical applications are already taking shape that can profoundly modify post-operative and wound healing follow-up. Future challenges and perspectives in the field are proposed.

A Novel Approach to the Production of Printed Patch Antennas

This paper presents the manufacturing of a patch antenna using an advanced 3D printing technology called lights-out digital additive manufacturing (LDM). This 3D LDM printing technology is mainly used for printing circuit boards (PCBs); however, it has also been used to print a patch antenna from conductive (CI) and dielectric ink (DI). This 3D LDM-printed antenna was compared with antennas on different dielectric substrates (Arlon 25N and FR4). The obtained results are compared and analyzed in this paper.

Feasibility analysis for the application of conduction tracks on textiles by means of laser radiation

Textiles are not only used for clothing but also have found applications in many other areas. Textiles fulfilling functional or technical properties are called “technical textiles.” Incorporation of conductive components, sensors, or materials reacting to environmental influences convert those into so-called “smart textiles.” Common methods of applying conductive tracks to textiles are embroidery, which can cause damage to the textile, or printing of a low-conductivity paste that may include toxic chemicals. A new method of applying electrical conductors to textiles for contacting is laser welding. In this process, a thin metal foil is welded on locally with an absorber placed above the metal foil to ensure that sufficient energy is applied to partially melt the textile underneath the metal foil. One variant for welding conductive tracks is the use of a globo-optics and a diode laser system with a wavelength of 975 nm. With these optics, the glass sphere focuses the laser beam and serves as a mechanical pressure tool for achieving a zero gap between fabric and foil. Parameters that are varied are the processing speed and the laser power receiving different track widths, as well as the type of textile. In this work, their influence is evaluated by microscopy, electrical resistance measurements during Martindale tests for abrasion resistance, and tensile tests. The investigations clarify the durability and utility of welded conductive tracks on textiles. It is possible to produce conductive tracks out of beaten copper joined on textiles using laser radiation showing conductivity after 10,000 abrasion cycles. The tensile strength of textiles totally made of thermoplastics is more influenced by the heat input of the laser than blended textiles, but their abrasion resistance is worse. Furthermore, an outlook on the possibility of welding using a laser source with a wavelength of 450 nm (blue laser) and a scanner as optics will be given.

Synthesis and characterization of novel banana-graphene nanofibrous membrane from viscous liquid for bandgap formation

Organic semiconductors with wide bandgaps have potential applications in organic light-emitting diode displays, organic photovoltaic devices, organic field-effect transistors and solar cells. However, organic semiconductors are not good conductors of electricity. This study synthesizes the banana-graphene nanofibrous membrane using an electric spin process to form a tunable bandgap to enhance conductivity. The chemical process was followed to prepare liquid viscous from banana stalks. Different percentages of graphene (1.2 wt.%, 2.4 wt.% and 3.6 wt.%) were used with the liquid viscous to form sizeable and tunable bandgaps in the composites and enhance the conductivity of the materials. The results showed 5.67 %, 24.5 %, and 27.8 % lower bandgap for 1.2 wt.%, 2.4 %, and 3.6 wt.% graphene-contained samples, respectively, as compared to the polyvinyl alcohol (PVA) viscous fibre (3.35 eV). With the addition of graphene with PVA viscous fibre, the properties of electrospun nanofibrous graphene were changed from insulator to semiconductor. The band gap property was controlled by incorporating graphene with various percentages. The morphology of the surfaces showed that nanofibers are bonded with each other, and graphene nanoparticles are uniformly distributed. The results of this work can be considered to further progress in manufacturing nanocomposites for organic semiconductor applications.

Influence of Different Drying Processes on the Chemical and Texture Profile of Cucurbita maxima Pulp.

The effects of hot air (HAD), vacuum (VAD) and conductive (CD) drying on the chemical and textural profiles of Cucurbita maxima pulp were investigated to find suitable drying conditions to avoid postharvest losses of pumpkin. The results showed that the drying methods had a significant effect (p < 0.05) on the chemical and textural profiles of pumpkin pulp. The ash content was lower in VAD (up to 7.65%) than in HAD (up to 9.88%) and CD pulp (up to 9.21%). The samples of HAD, CD and VAD had a higher fat content, up to 3.07, 2.66 and 2.51%, respectively, than fresh pulp (1.55%). The total fibre content is lower for VAD (up to 8.78%) than for HAD (up to 15.43%) and CD pulp (13.94%). HAD pulp at 70 °C (~15.51%) and VAD and CD pulp processed between 50 and 60 °C (~22%) are good sources of protein. HAD and CD pulp at 70 °C and VAD at 50 °C resulted in a high sugar content (up to 83.23%). In addition to drying, the extraction time of 40 min used in ultrasound-assisted extraction is optimal, especially for protein and sugar recovery in dried samples. Drying also led to strong changes in the textural properties of the pulp, so that an excellent dried intermediate product is the one obtained using HAD at a temperature of 70 °C and an airflow of 0.5 m/s.