Search Results (104)

This report is on Co and Ti substituted M-type barium and strontium hexagonal ferrites that are reported to be single phase multiferroics due to a transition from Neel type ferrimagnetic order to a spiral spin structure that is accompanied by a ferroelectric polarization in an applied magnetic field. The focus here is the nature of magnetoelectric (ME) interactions in the bilayers of ferroelectric PZT and Co and Ti substituted BaM and SrM. The ME coupling in the ferrite-PZT bilayers arise due to the transfer of magnetostriction-induced mechanical deformation in a magnetic field in the ferrite resulting in an induced electric field in PZT. Polycrystalline Co and Ti doped ferrites, Ba (CoTi)_x Fe_12−2xO_19, (BCTx), and Sr (CoTi)_x Fe_12−2xO₁₉ (SCTx) (x = 0–4) were found to be free of impurity phases for all x-values except for SCTx, which had a small amount of α-Fe₂O₃ in the X-ray diffraction patterns for x ≤ 2.0. The magnetostriction for the ferrites increased with applied filed H to a maximum value of around 2 to 6 ppm for H~5 kOe. BCTx/SCTx samples showed ferromagnetic resonance (FMR) for x = 1.5–2.0, and the estimated anisotropy field was on the order of 5 kOe. The magnetization increased with the amount of Co and Ti doping, and it decreased rapidly with x for x > 1.0. Measurements of ME coupling strengths were conducted on the bilayers of BCTx/SCTx platelets bonded to PZT. The bilayer was subjected to an AC and DC magnetic field H, and the magnetoelectric voltage coefficient (MEVC) was measured as a function of H and frequency of the AC field. For BCTx-PZT, the maximum value of MEVC at low frequency was ~5 mV/cm Oe, and a 40-fold increase at electromechanical resonance (EMR). SCTx–PZT composites also showed a similar behavior with the highest MEVC value of ~14 mV/cm Oe at low frequencies and ~200 mV/cm Oe at EMR. All the bilayers showed ME coupling for zero magnetic bias due to the magnetocrystalline anisotropy field in the ferrite that provided a built-in bias field. Full article

The surface profile and structural alignment of fibers and yarns in fabrics are critical factors affecting the electrical properties of conductive textile surfaces. This study aimed to investigate the impact of fabric surface roughness and the geometrical parameters of woven fabrics on their electrical resistance properties. Surface roughness was assessed using the MicroSpy^® Profile profilometer FRT (Fries Research & Technology) Metrology™, while electrical resistance was evaluated using the Van der Pauw method. The findings indicate that rougher fabric surfaces exhibit higher electrical resistance due to surface irregularities and lower yarn compactness. In contrast, smoother fabrics improve conductivity by enhancing surface uniformity and yarn contact. Fabric density, particularly weft density, governs the structural alignment of yarns. A 35% increase in weft density (W19–W27) resulted in a 13–15% reduction in resistance, confirming that denser fabrics facilitate current flow. Higher weft density also increases directional resistance differences, enhancing anisotropic behavior. Angular distribution analysis showed lower resistance and greater anisotropy at perpendicular orientations (0° and 180°, the weft direction; 90° and 270°, the warp direction), while diagonal directions (45°, 135°, 225°, and 315°) exhibited higher resistance. Surface roughness further hindered current flow, whereas increased weft density and surface mass reduced resistance and improved the directional dependencies of the electrical resistances. This analysis was conducted based on research using woven fabrics produced from silver-plated polyamide yarns (Shieldex^® 117/17 HCB). These insights support the optimization of these conductive fabrics for smart textiles, wearable sensors, and e-textiles. Fabric variants W19 and W21, with lower resistance variability and better isotropic behavior under the S electrode arrangement, could be proposed as suitable materials for integration into compact sensing systems like heart rate or bio-signal monitors. Full article

In recent years, flexible piezoresistive sensors based on polydimethylsiloxane (PDMS) matrix materials have developed rapidly, showing broad application prospects in fields such as human motion monitoring, electronic skin, and intelligent robotics. However, achieving a balance between structural durability and fabrication simplicity remains challenging. Traditional methods for preparing PDMS flexible substrates with high porosity and high stability often require complex, costly processes. Breaking through the constraints of conventional material systems, this study innovatively combines the high elasticity of polydimethylsiloxane (PDMS) with the stochastically distributed porous topology of a sponge-derived biotemplate through biomimetic templating replication technology, fabricating a heterogeneous composite system with an architecturally asymmetric spatial network. After 5000 loading cycles, uncoated samples experienced a thickness reduction of 7.0 mm, while PDMS-coated samples showed minimal thickness changes (2.0–3.0 mm), positively correlated with curing agent content (5:1 to 20:1). The 5:1 ratio sample demonstrated exceptional mechanical stability. As evidenced, the PDMS film-encapsulated architecturally asymmetric spatial network demonstrates superior stress dissipation efficacy, effectively mitigating stress concentration phenomena inherent to symmetric configurations that induce matrix fracture, thereby achieving optimal mechanical stability. Compared to the pre-test resistance distribution of 10–248 Ω, after 5000 cyclic loading cycles, the uncoated samples exhibited a narrowed resistance range of 10–50 Ω, while PDMS-coated samples maintained a broader resistance range (10–240 Ω) as the curing agent ratio increased (from 20:1 to 5:1), demonstrating that increasing the curing agent ratio helps maintain conductive network stability. The 5:1 ratio sample displayed the lowest resistance variation rate attenuation—only 3% after 5000 cycles (vs. 80% for uncoated samples)—and consistently minimal attenuation at all stages, validating superior electrical stability. Under 0–6 kPa pressure, the 5:1 ratio device maintained a linear sensitivity of 0.157 kPa⁻¹, outperforming some existing works. Human motion monitoring experiments further confirmed its reliable signal output. Furthermore, the architecturally asymmetric spatial network of the device enables superior conformability to complex curvilinear geometries, leveraging its structural anisotropy to achieve seamless interfacial adaptation. By synergistically optimizing material composition and structural design, this study provides a novel technical method for developing highly durable flexible electronic devices. Full article

In this paper, we conduct a detailed in silico study of the role of topological features in the electronic transport properties of all-carbon films. To create all-carbon film supercells, we used AA- and AB-stacked bilayer graphene, as well as (5,5), (6,0), (16,0), (12,6), and (8,4) single-walled carbon nanotubes (SWCNTs). For the first time, the simultaneous influence of several topological features on the quantum transport of electrons in graphene–nanotube films are considered. Topological features are understood as the topological type of nanotubes (chiral or achiral), the stacking order in bilayer graphene (AA or AB), and the mutual orientation of bilayer graphene and nanotubes. A characteristic feature of the studied all-carbon films is the presence of electrical conductivity anisotropy. Moreover, depending on the topological features of all-carbon films, the values of electrical resistance can differ by tens of times in different directions of electron transport. The patterns of formation of the profile of the electron transmission function of the studied structural configurations of all-carbon film are established. It is found that the mutual orientation of bilayer graphene and nanotubes plays an important role in the electronic transport properties of all-carbon films. The obtained results make a significant contribution to the understanding of the mechanisms controlling the electrical conductivity properties of all-carbon films at the atomic level. Full article

Microswimmers are key for unveiling new physical phenomena underlying their propulsion, especially when driven inside complex fluids. Liquid crystals are anisotropic complex fluids that feature long-range orientational order. The propulsion of non-charged dielectric particles can be accomplished in these systems by breaking the particles’ fore-aft symmetry thanks to anisotropies in the conductivity and dielectric permittivity parameters of the liquid crystal. Under the application of an AC electric field, asymmetric osmotic flows are generated to propel non-spherical particles, whose direction of motion depends on the orientational order of the liquid crystal molecules around the inclusions. This means that, by controlling the LC orientation, one will be able to steer driven colloidal inclusions. In this experimental work, we show that a homogeneous magnetic field that is able to control the orientation of the liquid crystal molecules also allows us to determine the direction of motion of driven particles without significant changes in the propulsion mechanism. Additionally, we show that a radial configuration of the magnetic field lines can be used to generate topological defects in the liquid crystal orientational field that attract colloidal particles, leading to their clustering as rotating mills. The generated clusters were tested to study the collective motion of particles, suggesting the presence of particle–particle interactions. Full article

Ta₂AlC is an emerging ceramic material characterized by its high melting point, high hardness, excellent thermal stability, and superior mechanical properties, which allow for broad application prospects in aerospace and defense fields. This paper investigates the physical mechanisms underlying the modulation of the mechanical and photoelectric properties of Ta₂AlC through doping using the first-principles pseudopotential plane-wave method. We specifically calculated the geometric structure, mechanical properties, electronic structure, Mulliken population analysis, and optical properties of Ta₂AlC doped with V, Ga, or Si. The results indicate that doping induces significant changes in the structural parameters of Ta₂AlC. By applying the Born’s criterion as the standard for mechanical stability, we have calculated that the structures of Ta₂AlC, both before and after doping, are stable. The mechanical property calculations revealed that V and Si doping weaken the material’s resistance to deformation while enhancing its plasticity. In contrast, Ga doping increases the material’s resistance to lateral deformation and brittleness. Doping also increases the anisotropy of Ta₂AlC. Electronic structure calculations confirmed that Ta₂AlC is a conductor with excellent electrical conductivity, which is not diminished by doping. The symmetric distribution of spin-up and spin-down electronic state densities indicates that the Ta₂AlC system remains non-magnetic after doping. The partial density of states diagrams successfully elucidated the influence of dopant atoms on the band structure and electronic state density. Mulliken population analysis revealed that V and Ga doping enhance the covalent interactions between C-Ta and Al-Ta atoms, whereas Si doping weakens these interactions. Optical property calculations showed that V and Si doping significantly enhance the electromagnetic energy storage capacity and dielectric loss of Ta₂AlC, while Ga doping has minimal effect. The reflectivity of doped and undoped Ta₂AlC reaches over 90% in the ultraviolet region, indicating its potential as an anti-ultraviolet coating material. In the visible light region, both doped and undoped Ta₂AlC exhibit a similar metallic gray appearance, suggesting its potential as a temperature control coating material. The light loss of Ta₂AlC is limited to a narrow energy range, indicating that doping does not affect its use as a light storage material. These results demonstrate that different dopants can effectively modulate the mechanical and photoelectric properties of Ta₂AlC. Full article

The aim of this work was to determine the anisotropy of the electrophysical and mechanical properties of rubber reinforced with a hybrid filler CNTs&CB (carbon nanotubes and carbon black) as a function of CNT content and the technological parameters of the production process. A significant difference in electrical conductivity (σ) and dielectric permittivity (ε) in three perpendicular directions was found for CNT concentrations ranging from 0 to 0.007 in volume fraction. The highest values of σ and ε were observed in the calendering direction, with slightly lower values in the perpendicular direction. This effect was attributed to the orientation of polymer molecules and CNTs along the direction of movement during calendering, as well as the disruption of the cluster structure in the transverse direction. Although the calculated percolation threshold values of the investigated system differed slightly, a correlation was observed between the mechanical and electrophysical properties of CNTs&CB rubber. This correlation enables rubber products to be designed with optimal properties tailored to the desired direction. Full article

Background/Objectives: Although multiple magnetic resonance imaging (MRI) indices are known to be sensitive to the noninvasive assessment of myelin integrity, their relative sensitivities have not been directly compared. This study aimed to identify the most sensitive MRI index for characterizing myelin composition in the spinal cord’s gray matter (GM) and white matter (WM). Methods: MRI was performed on a deer’s ex vivo cervical spinal cord. Quantitative indices known to be sensitive to myelin, including the myelin water fraction (MWF), magnetization transfer ratio (MTR), the signal ratio between T1- and T2-weighted images (T1W/T2W), fractional anisotropy (FA), mean diffusivity (MD), electrical conductivity (σ), and T1, T2, and T1ρ relaxation times were calculated. Their mean values were compared using repeated measures analysis of variance (ANOVA) and post hoc Bonferroni tests or Friedman and post hoc Wilcoxon tests to identify differences across GM and WM columns possessing distinct myelin distributions, as revealed by histological analysis. Relationships among the indices were examined using Spearman’s rank-order correlation analysis. Corrected p < 0.05 was considered statistically significant. Results: All indices except σ differed significantly between GM and all WM columns. Two of the three WM columns had significantly different MWF, FA, MD, and T2, whereas one WM column had significantly different MTR, σ, T1, and T1ρ from the others. A significant moderate to very strong correlation was observed among most indices. Conclusions: The sensitivity of MRI indices in distinguishing spinal cord regions varied. A strategic combination of two or more indices may allow the accurate differentiation of spinal cord regions. Full article

Ni₃Sn₄ intermetallic compound (IMC) is a critical material in modern electronic packaging and soldering technology. Although Ni₃Sn₄ enhances the strength of solder joints, its brittleness and anisotropy make it prone to crack formation under mechanical stress, such as thermal cycling or vibration. To improve the plasticity of Ni₃Sn₄ and mitigate its anisotropy, this study employs first-principles calculations to investigate the mechanical properties and electronic structure of the doped compounds Ce_x Ni_3−xSn₄ (x = 0, 0.5, 1, 1.5, 2) by adding the rare earth element Ce. The results indicate that the structure Ce_0.5 Ni_2.5Sn₄ has a lower formation enthalpy (${\mathrm{H}}_{\mathrm{f}}$) compared to other doped structures, suggesting enhanced stability. It was found that all structures exhibit improved plasticity with Ce doping, while the Ce_0.5 Ni_2.5Sn₄ structure shows relatively minor changes in hardness (H) and elastic modulus, along with the lowest anisotropy value (${\mathrm{A}}^{\mathrm{U}}$). Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals that the electronic properties are primarily influenced by the Ni-d and Ce-f orbitals. At the Fermi level, all Ce_x Ni_3−xSn₄ (x = 0, 0.5, 1, 1.5, 2) structures exhibit metallic characteristics and distinct electrical conductivity. Notably, the TDOS value at the Fermi level for Ce_0.5 Ni_2.5Sn₄ lies between those of Ni₃Sn₄ and other doped structures, indicating good metallicity and conductivity, as well as relative stability. Further PDOS analysis suggests that Ce doping enhances the plasticity of Ni₃Sn₄. This study provides valuable insights for the further application of rare earth elements in electronic packaging materials. Full article

In the context of rising power densities in electrical machines, additive manufacturing presents an opportunity to develop more powerful thermal solutions. However, the physical properties of objects manufactured using this process remain unclear. This research examines the directional thermal and electrical conductivities of aluminum alloy (AlSi10Mg) and silicon steel (Fe-3.7%wt. Si) samples produced via laser powder bed fusion (LPBF), both prior to and following heat treatment. The findings indicate that the as-built aluminum samples exhibit higher conductivities in the orientation parallel to the LPBF build direction, while annealing results in higher conductivities overall and an absence of anisotropy. On the other hand, the silicon steel samples show constant conductivities and lack of anisotropy both before and after heat treatment. These results have practical applications in the design of additively manufactured electrical machines, where the thermal and electrical resistance of the materials have a major impact on thermal and electromagnetic performance. Full article

Pure copper (Cu) is widely used across numerous industries owing to its exceptional thermal and electrical conductivity. Additive manufacturing has facilitated the rapid and cost-effective prototyping of Cu components. Laser powder bed fusion (LPBF) has demonstrated the capability to produce intricate Cu components. However, LPBF-fabricated components exhibit anisotropic features, which stem from their inherent thermal gradients, resulting in properties that depend on the grain orientation. In the present study, pure Cu samples were fabricated via micro-laser powder bed fusion (μLPBF), resulting in improved mechanical properties, specifically, enhanced strength and ductility. The as-printed pure Cu sample exhibited thermal stability owing to its high-density grain boundaries and dislocations, enabling it to maintain relatively high levels of strength and ductility even when exposed to an elevated temperature of 300 °C. Furthermore, the heat treatment resulted in the disappearance of the initial microstructural characteristics, such as molten pool boundaries. As the heat-treatment temperature increased, the anisotropic yield strength decreased. Overall, the anisotropy of the properties of pure Cu components fabricated via μLPBF can be mitigated through heat-treatment-induced microstructural adjustments. Full article

In this research paper, the factors impacting electrical conductivity of the flexible graphite foils (GFs) produced by different forming processes, namely, either by rolling or pressing, were studied. The relationship between electrical conductivity and texture and structure that formed when producing the material was examined. Correlation was determined between the texture sharpness and anisotropy of electrical conductivity, as well as the extent of impact from the substructural characteristics on the properties’ values. Besides, it was demonstrated that the higher values of micro-strains, as well as the secondary phase substructure, reduced conductivity in foils. Electrical conductivity calculation was optimized for different directions in foils using the Kearns texture parameters and taking into consideration the foil structural characteristics. Full article

The use of additive manufacturing to fabricate current collectors with increased surface area opens new opportunities for controlling electrode morphology, improving conductivity, and thereby boosting the overall performance of batteries. This can be achieved by increasing the contact area between the active mass and the current collector. This paper focuses on the investigation of 3D current collectors with an enhanced surface area for cathodes obtained by laser powder bed fusion. The quality and dimensional accuracy of the 3D current collector structures as well as the electrical characteristics and longevity of batteries were analyzed in this study. It has been demonstrated that the utilization of printing parameters comprising a laser power of 200 W, a scanning speed of 500 mm/s, and a hatch distance of 0.25 mm, with a layer thickness of 0.03 mm, results in a decrease in the number of defects in the 3D current collector. In the first cycle, the capacitance characteristics exhibited discharge capacities of 189.79 mAh/g for Al-f and 192.06 mAh/g for AlSi10Mg. The Coulomb efficiencies for the samples were 86 and 92.5%, respectively. Anisotropy of conductive properties arises during the printing process, which must be considered when designing the 3D current collectors, as it may have an impact on the capacitive and cyclic characteristics of the samples. Full article

Chiral electroactive materials have attracted attention for the effects of electrical magnetochiral anisotropy (eMChA) and chirality-induced spin selectivity (CISS). The combination of tetrathiafulvalene (TTF) with chiral moieties is one way to access chiral electroactive materials. In this paper, we have focused on the fused 2,3-dimethylcyclohexene (DMCh) ring as a substituent with chiral carbon atoms and without heteroatoms, which has not been used in the field of molecular conductors, and we synthesized a new TTF derivative (rac-DMCh-EDT-TTF). We have developed novel molecular conductors (rac-DMCh-EDT-TTF)₂X (X⁻ = PF₆⁻, AsF₆⁻ and ClO₄⁻), which have bilayer conducting sheets composed of the two crystallographically independent molecules. All salts exhibited semiconducting behavior from room temperature down to low temperatures, and a resistivity anomaly was observed at 180–250 K. X-ray structure analysis at 100 K and 263 K and molecular orbital calculations using the results of X-ray structure analysis indicated the emergence of a charge disproportionation between Layers 1 and 2 at the low-temperature phase. Full article

In response to the challenges posed by the complexity and potential hazards of traditional chemical methods for detecting the surface density of carbon fiber prepreg materials, this paper explores the use of eddy current testing principles. It establishes the relationship between coil impedance variation and the surface density of carbon fiber prepreg materials and designs a quadrupolar excitation eddy current detection probe. This probe can detect the surface density of both single-line and woven carbon fiber prepreg structures. The overall structure and dimensions of the designed quadrupolar probe were optimized using finite element simulation software. The results show that the number of coil turns significantly affects the sensor performance, with more turns leading to increased sensitivity. Moreover, with the same number of coil turns, smaller inner diameters and larger outer diameters of the coil enhance sensor sensitivity. A comprehensive comparison between unidirectional and woven carbon fiber models suggests that woven structures have superior electrical conductivity at identical excitation frequencies, while unidirectional models show more pronounced electrical anisotropy. These findings provide valuable insights for analyzing electrical properties, numerical simulations, and eddy current testing in composite materials. Full article