We have studied the thermal stability of NCM622 cathode material for Li-ion batteries using real-time synchrotron x-ray scattering below 600°C in both air and vacuum. The expansion of the mean particle size, which reached maximum values of 10.3 μm in air and 10.6 μm in vacuum at 200°C, was attributed to the dehydration of intergranular water within the NCM622 powders. Across all annealing temperatures, the amount of crystal NCM622 phase in air was consistently higher than that in vacuum. The crystal domain sizes in air showed less variation than that in vacuum during annealing from RT to 500°C. These indicate that the crystal NCM622 phase is more thermally stable during annealing in air than in vacuum. This stability is attributed to the presence of 21% oxygen in air, which is absent under vacuum conditions.

Dye adsorption is one of the most time-consuming processes in the fabrication of dye-sensitized solar cells (DSSCs), typically requiring approximately 24 h at room temperature. In this study, the effect of adsorption temperature and time on photovoltaic performance of DSSCs was investigated in order to reduce processing time and improve device productivity. Nanoporous TiO₂ photoelectrodes were immersed in N719 dye solution at 60°C for 3 h, 10 h, 17 h, and 24 h, and their performance was compared with that of cells sensitized at room temperature for 24 h. Photovoltaic characterization under AM 1.5 illumination showed that DSSCs sensitized at 60°C exhibited improved performance compared to those sensitized at room temperature. The device sensitized at 60°C for 3 h showed comparable or higher conversion efficiency than the reference cell sensitized for 24 h at room temperature. The improvement in device performance is attributed to enhanced dye adsorption kinetics resulting from increased reaction rate between the carboxyl groups of N719 dye molecules and hydroxyl groups on the TiO₂ surface. Electrochemical impedance spectroscopy analysis revealed reduced recombination resistance at the TiO₂/dye/electrolyte interface for cells sensitized at elevated temperature. UV–Vis absorption analysis confirmed increased dye loading on the TiO₂ surface for the 60°C condition. These results demonstrate that elevated temperature dye adsorption significantly reduces processing time while maintaining photovoltaic performance, providing an effective strategy for improving manufacturing efficiency of DSSCs.

The dielectric and piezoelectric properties of the ferroelectric BaTiO₃ were measured and analyzed using both strong and weak electric field conditions. To measure the electric field induced polarizations and strains, a high voltage source and the measuring circuit were used and the dielectric constants were measured with an impedance analyzer. The spontaneous polarization of BaTiO₃ at room temperature was calculated as 17 μC/cm² based on the lattice structure and internal ion location, which is in good agreement with the experimental results. The polarization and strain hysteresis curve according to the electric field were analyzed in terms of lattice structure and ion position. The magnitude of remanent polarization is proportional to the offset distance of Ti⁴⁺ ion from the lattice center. The magnitude of dielectric permittivity is proportional to the degree to which Ti⁴⁺ ion can move freely inside the lattice. The magnitude of piezoelectric constant d₃₃ is proportional to how much Ti⁴⁺ ion distorts the lattice as it moves inside the lattice.

The direct utilization of steelmaking by-product gases in solid oxide fuel cells (SOFCs) offers a promising pathway to improve energy efficiency and reduce carbon emissions in the steel industry. In this study, a Sr-deficient and Ni-doped double perovskite oxide, Sr_1.95Fe_1.35Ni_0.15Mo_0.5O_6-δ (SFNM), was investigated as an anode material for direct Linz-Donawitz converter gas (LDG)-fueled SOFCs. A single-phase double perovskite structure was successfully obtained after calcination at 1,200°C for 12 h, while exsolved metallic Ni nanoparticles were generated on the SFNM surface after reduction at 800°C. Electrochemical performance was evaluated using H₂, simulated-LDG, and CO/CO₂ (85:15) fuels at 800°C. The maximum power densities achieved were 1.23, 0.70, and 0.40 W cm^-2 for H₂, simulated-LDG, and CO/CO₂ fuels, respectively. Although CO-containing fuels exhibited lower opencircuit voltages and power outputs than H₂, the SFNM anode maintained stable operation and appreciable performance under direct simulated-LDG utilization. Impedance analysis revealed that the increased polarization resistance in simulated-LDG and CO/CO₂ atmospheres was mainly associated with fuel adsorption/desorption and gas diffusion, while interfacial charge-transfer resistance remained relatively small. The superior performance obtained with simulated-LDG compared to the CO/CO₂ mixture was attributed to the presence of a small amount of H₂, which facilitated anode reaction kinetics. These results demonstrate that SFNM is a promising mixed ionic-electronic conductor anode for the direct electrochemical conversion of CO-rich steelmaking by-product gases into electricity.

Wearable temperature sensors are becoming increasingly important for continuous health monitoring, personalized healthcare, and biointegrated electronic systems. However, conventional temperature-sensing platforms often suffer from limited thermal sensitivity, insufficient mechanical compliance, and unstable performance under repeated deformation, making it difficult to detect subtle physiological temperature variations in real time. Here, this tutorial status report presents a fabrication strategy for highly sensitive wearable temperature sensors based on gold-doped crystalline silicon nanomembranes. Gold diffusion into crystalline silicon introduces deep-level impurity states that modulate the Fermi level and shift the freeze-out region toward the physiological temperature range, enabling an ultrahigh negative temperature coefficient of resistance. By integrating the gold-doped silicon nanomembrane with a polyimide-supported ultrathin platform, neutral mechanical plane design, and serpentine mesh interconnects, the resulting device can provide high thermal sensitivity, fast response, conformal skin attachment, and stable operation under mechanical deformation. This fabrication approach is expected to broaden the use of impurity-engineered silicon nanomembranes in next-generation wearable sensors, flexible bioelectronics, and multifunctional healthcare monitoring systems.

Quantum dots (QDs) are semiconductor nanocrystals with sizes on the order of several nanometers, whose bandgaps can be tuned by controlling the particle size. Owing to this bandgap tunability, QDs can absorb near-infrared (NIR) and short-wave infrared (SWIR) light, spectral regions that are difficult to access with conventional silicon-based devices. However, colloidal QDbased infrared photodetectors still suffer from intrinsically high dark current, trap-induced noise, and limited response speed. As a result, they exhibit fundamental performance gaps in terms of detectivity and speed–bandwidth product compared to epitaxial infrared detectors, highlighting the need for structural and architectural design strategies to overcome these limitations. In this review, we discuss recent advances in enhancing the spectral selectivity and sensitivity of infrared photodetectors through three-dimensional optical architectures, including metasurfaces and metamaterials. We focus in particular on design strategies and the underlying mechanisms responsible for performance enhancement, and we outline how structural approaches can be leveraged to effectively control the sensitivity and wavelength selectivity of QD-based infrared detectors.

This review offers a critical overview of recent developments in lead-free piezoelectric materials and flexible device architectures for self-powered wearable and Internet of Things systems. It examines the scientific and technological rationale for replacing conventional battery-dependent power sources with ambient mechanical energy harvesters, and it evaluates the relative merits of inorganic ceramics, organic polymers, and composite systems in achieving efficient electromechanical conversion under practical operating conditions. The discussion further considers compositional tuning, phase boundary engineering, microstructural optimization, and device-level integration as key strategies for improving piezoelectric output, mechanical compliance, durability, and manufacturability. By connecting fundamental materials design with application-driven device requirements, the review identifies the principal challenges and emerging directions necessary for the realization of reliable, scalable, and sustainable electronic platforms.

Renewable energy harvesting technologies, which convert ambient resources such as wind into electrical energy, have attracted significant attention as sustainable power sources for self-powered systems. However, the long-term applicability of wind energy harvesters in remote or extreme environments has not yet been fully discussed, particularly in terms of structural robustness and environmental adaptability. In this study, we designed a double-clamped flutter-type triboelectric generator (DFTEG) for efficient wind energy harvesting and evaluated its output performance under various simulated outdoor conditions. The DFTEG features a modular acrylic frame with a magnet-based assembly for easy maintenance and film replacement, utilizing PTFE films and aluminum electrodes to maximize the charge density difference according to the triboelectric series. Structural optimization revealed that a single-film configuration with a length of 110 mm produced the most stable flutter vibration and a large effective contact area, achieving a maximum open-circuit voltage of 42.28 V and a short-circuit current of 2.89 μA. Furthermore, performance evaluations under various environmental variables, including relative humidity, temperature, and sand particles interference, confirmed consistent electrical output across diverse environmental conditions. These results demonstrate the potential of the proposed DFTEG as an environmentadaptive independent power source capable of stable operation under complex environmental factors.

The development of a large-area solution process for CuO nanowires, which are promising p-type thin film transistors (TFT) channel materials, is required. To overcome the limitations of the existing high-vacuum and high-cost deposition process, a large-area Cu nanowire network was formed on the substrate using the Mayer rod coating method, and a CuO channel was implemented by subsequent thermal annealing. Consequently, p-type TFT with an on/off current ratio of 1.4×10⁴ and a field-effect mobility µ_FE≈10^-4 cm²/(V⋅s). was fabricated and optimized. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that the sample annealed at 200°C exhibited an incomplete oxidation state with a mixed Cu/Cu₂O phase and a high fraction of M-OH species (58.78%), resulting in a low on/off current ratio (≈1.2). In contrast, annealing at 450°C leads to a CuOdominant phase, where the fraction of lattice oxygen(O1) increases to 31.11% and the oxygen vacancy (VO) component increases to 7.15%, indicating a significant improvement in hole concentration and charge transport. These phase transitions and surface chemical changes are identified as the key mechanisms for the enhanced TFT switching characteristics. The low-cost, large-area Mayer rodbased solution process proposed in this study provides a basic process platform for p-type TFTs applicable to flexible wearables and display technologies and suggests the possibility of commercialization through additional optimization of bias stability in the future.

With the rapid expansion of electric vehicles (EVs) and energy storage systems (ESS), ensuring the operational safety of lithium-ion batteries has become a critical technical challenge. Conventional battery management systems (BMS) primarily rely on threshold-based rule logic, which is limited in detecting coupled anomalies and early-stage degradation patterns. In this study, a deep learning-based framework for multivariate anomaly detection is proposed using BMS sensor data, including voltage, current, temperature, state of charge (SOC), and state of health (SOH). Five representative fault scenarios were defined, including thermal runaway precursors, cell voltage imbalance, SOC inconsistency, internal resistance increase, and communication delay. The proposed CNN-LSTM model was compared with conventional Rule-based methods and machine learning models, including Isolation Forest, Autoencoder, and LSTM. Experimental results show that the proposed model achieved the highest performance, with an F1-score of 0.885, an AUC of 0.94, and a detection delay of 8.1 s. In contrast, the Rule-based method exhibited a significantly higher false negative rate of 42.0%, indicating limitations in detecting complex anomaly patterns. These results demonstrate that the proposed spatiotemporal deep learning approach can significantly improve the accuracy and responsiveness of battery anomaly detection. Furthermore, the proposed method is expected to contribute to enhancing safety, reliability, and predictive diagnostics in next-generation intelligent BMS platforms.

This study proposes an optimization strategy for the over-current protection (OCP) parameters of a lithium iron phosphate (LiFePO₄, LFP) battery system used in electric golf carts operating under high motor-load conditions. Real-world hillclimbing tests were conducted under four clearly defined payload/passenger conditions to analyze the transient discharge-current pro-file, voltage sag, and cell-temperature response. The maximum discharge current reached -238.2 A under the 200 kg cargopayload and one-passenger condition, and the current interval exceeding 150 A lasted up to 27 s. The maximum instantaneous power was 11.05 kW. Thermal analysis showed that the cell-temperature rise was within 2°C and the maximum measured cell temperature was 22.3°C. Linear regression of voltage and current yielded R² = 0.9368 and dV/dI = 0.0126 Ω, which was used as the DC internalresistance estimate. Based on these quantitative results and the cell specification limit of 300 A continuous discharge, the OCP threshold was reviewed from 250 A to 280 A to improve driving continuity while remaining below the allowable continuous-discharge current. EIS-based SOH estimation and the AI-BMS variable protection logic are presented as an extension framework for reflecting temperature and aging effects in future OCP-setting decisions.

Organic solar cells based on bulk heterojunction (BHJ) structures have attracted considerable attention because of their low fabrication cost, mechanical flexibility, and compatibility with solution-processing techniques. In BHJ organic photovoltaic devices, nanoscale morphology and crystallinity of the photoactive layer critically influence photovoltaic performance. In this study, the effects of solvent selection and thermal annealing on crystallization evolution and photovoltaic characteristics of P3HT:PCBM organic solar cells were systematically investigated. Three different solvents, including toluene, chlorobenzene (CB), and dichlorobenzene (DCB), were employed for active-layer fabrication, followed by post-thermal annealing treatment. UV–visible absorption spectroscopy revealed solvent-dependent differences in molecular ordering and intermolecular π–π interactions within the active layer. X-ray diffraction analysis confirmed that thermal annealing significantly enhanced crystallinity and lamellar ordering of P3HT domains, particularly for CB-processed films. Electrical characterization demonstrated that solvent evaporation behavior strongly affects photovoltaic performance. Among the investigated devices, the thermally annealed CB-processed device exhibited the highest power conversion efficiency of 1.83% with an enhanced short-circuit current density of 7.057 mA cm⁻². The improved device performance is attributed to optimized crystallization behavior and balanced nanoscale phase separation induced by the moderate evaporation characteristics of CB. In contrast, although DCB-assisted films exhibited relatively strong optical absorption and enhanced crystallinity, excessively slow solvent evaporation likely induced excessive aggregation and coarse phase separation, limiting efficient photovoltaic characteristics. These results demonstrate that solvent engineering combined with thermal annealing is an effective strategy for controlling morphology evolution and crystallization behavior in P3HT:PCBM bulk heterojunction solar cells.

This paper reviews the energy yield enhancement characteristics of bifacial photovoltaic systems combined with solar tracking, focusing on their performance relative to conventional monofacial fixed-tilt configurations. The fundamental mechanisms of yield improvement are summarized, highlighting the largely additive contributions of solar tracking, which increases front-side irradiance, and bifacial modules, which utilize rear-side reflected and diffuse radiation. Reported results from previous studies indicate that bifacial systems with single-axis tracking typically achieve 25–35% higher annual energy yield compared with standard monofacial fixed-tilt systems, with variations depending on environmental and design conditions. Key design and environmental considerations influencing system performance are discussed to provide practical insights for the application of bifacial tracking systems in utilityscale photovoltaic installations.

The expansion of smart healthcare and wearable electronics has intensified the need for fabric-based sensors that integrate conformally with the human body for continuous bio signal monitoring. However, the heavy reliance of conventional devices on external batteries remains a major obstacle to commercialization, necessitating the development of flexible piezoelectric energy harvesters that convert biomechanical energy into sustainable power. Here, we present a highly flexible and wearable piezoelectric energy harvester (PEH) fabricated by a screen-printing of BaTiO₃ nanoparticlePDMS composites onto a fabric substrate. An optimized piezo-ceramic filler concentration of 70 wt% yielded a peak output voltage of 0.52 V and a current of 40 nA under the mechanical bending deformations. The fabricated PEH demonstrated exceptional mechanical and electrical stability, showing no performance degradation of over 5,000 repetitive bending cycles. These results indicate that a PEH can function as a stable self-powered source within complex clothing environments, offering a promising pathway for next-generation autonomous wearable sensor systems.

Polymer nanocomposites incorporating inorganic nanofillers have emerged as highly promising electromagnetic interference (EMI) shielding materials, combining mechanical compliance with robust conductive percolation networks. Carbon nanotubes (CNTs) are particularly attractive as conductive fillers because their high aspect ratio facilitates percolation at low loadings. Also, CNTs offer superior mechanical durability under deformation compared to rigid, fracture-prone metal nanowires. For EMI shielding, high electrical conductivity is critical as it enhances both reflection and absorption through efficient charge dissipation and conduction losses. However, achieving highly aligned conductive pathways without degrading the intrinsic electrical properties of CNTs remains a significant challenge. Here, we demonstrate a non-destructive magnetic surface-functionalization and alignment strategy. Using a polydopamine (PDA)-mediated route, pristine multiwalled CNTs are uniformly decorated with Fe₃O₄ nanoparticles (FMWCNTs). This enables highly effective magnetic field-driven alignment at fields as low as 10 mT, promoting the strategic formation of percolation networks. By optimizing the Fe₃O₄/MWCNT ratio for high saturation magnetization and uniform coverage, the aligned FMWCNTs exhibit significant electrical anisotropy, delivering a 10.7-fold higher electrical conductivity in the parallel configuration compared to the vertical configuration. These findings present a scalable, room-temperature platform for engineering directionally enhanced conductivity in polymer nanocomposites, with broad applicability in advanced EMI shielding, flexible electronics, and advanced packaging technologies.

GaN nanowire (NW)-based hybrid structures have attracted attention for optoelectronic applications due to their high surface area and efficient carrier transport. However, the optical transparency of GaN NWs is often limited by unintended residual species accumulated on the surface and in the inter-wire regions, as well as defect-related absorption, leading to reduced light transmission. In this work, we demonstrate that thermal annealing significantly improves the optical transparency of GaN NWs grown on indium tin oxide (ITO)/glass substrates. The transmittance increased from 47.9% to 78.5% at 550 nm after rapid thermal annealing at 800^oC for 3 min, while a comparable value (~75.5%) was achieved at 600^oC for 5 min. PbBr₃ was deposited onto the GaN NWs to form hybrid structures, and temperature-dependent photoluminescence (TDPL) measurements revealed enhanced emission stability with suppressed peak shift and reduced spectral broadening. Arrhenius analysis based on a two-channel model revealed that the activation energy of the dominant non-radiative recombination pathway increased from 62 meV in the as-grown sample to 85 meV after thermal annealing, while its relative contribution remained nearly unchanged. In contrast, the shallow trap-assisted pathway exhibited a similar activation energy of approximately 6 meV in both samples, but its contribution decreased from 0.35 to 0.17 after annealing. As a result, the internal quantum efficiency (IQE) improved from 75.9% to 87.4%. These results show that thermal annealing improves optical transparency by removing residuals and suppresses defect-related recombination, leading to enhanced carrier dynamics and improved optical performance of PbBr₃-based hybrid structures.

This paper proposes a circular sequential lighting control method to reduce current imbalance and luminance deviation among multiple LED modules in AC-powered LED lighting systems. Conventional fixed-sequence lighting control repeatedly prioritizes the same LED modules in every rectified voltage cycle, which leads to unequal current distribution, luminance non-uniformity, and the accelerated degradation of specific modules during long-term operation. To address these limitations, a circular sequential lighting strategy is introduced, in which the lighting order is cyclically rotated at every rectified cycle, ensuring that all LED modules experience equal lighting opportunities. A prototype AC-LED lighting system consisting of four series-connected LED modules was implemented and experimentally evaluated. The results demonstrate that, while the conventional fixed-sequence method produces a maximum average current deviation of up to 1.6 mA among modules, the proposed method equalizes the average current across all modules to approximately 17.1 mA. Furthermore, the flicker index remains at 0.13, which is comparable to that of the conventional method, indicating that luminance uniformity is improved without degradation of optical performance. The proposed circular sequential lighting control effectively distributes electrical stress, enhances luminance uniformity, and improves long-term reliability, making it a practical and efficient solution for high-quality AC-LED lighting applications.

The rapid advancement of large-scale language models and artificial intelligence technologies has highlighted the importance of data processing efficiency. This study outlines a measurement optimization method for high-speed pulse equipment to accurately analyze the operating dynamics of ReRAM, a core hardware component for simulating neural networks. An optimized evaluation methodology combining connection compensation and a dual-channel configuration was established to minimize measurement errors caused by parasitic resistance and capacitance during pulse measurements using the Keithley 4200A-SCS and 4225-PMU modules, and to address HRS/LRS measurement errors caused by mismatches between the measurement range and source limits. The proposed precision measurement guidelines can be applied to the evaluation of semiconductor devices that require pulse measurements, such as transistors and DRAM.

Metamaterials, as artificially engineered structures with unconventional mechanical and acoustic properties, have recently emerged as a transformative platform for enhancing the capabilities of triboelectric nanogenerator (TENG) systems. Since the invention of TENG devices, extensive efforts have been devoted to improving charge density, output stability, and overall performance. Conventional performance optimization strategies mainly rely on device-level improvements such as surface chemistry modification, microstructuring, and nanopatterning. However, limited emphasis has been given to system-level development of smart self-powered intelligent systems. The integration of metamaterials into TENG devices opens a new era by enabling frequency-selective localization, mechanical impedance matching, and controllable deformation pathways. These engineered mechanical structures not only improve energy harvesting efficiency but also introduce new functionalities into the system. This review systematically summarizes recent advances in metamaterial-integrated TENG systems across four major application domains: (i) energy harvesting, (ii) acoustic telecommunication and acoustic-to-electric conversion, (iii) self-powered sensing, and (iv) vibration suppression and monitoring. Overall, the integration of metamaterials into TENG systems will pave the way for next-generation sustainable, intelligent, self-powered devices with diverse functionalities.

Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.

Long lifetime, low power consumption, and environmental friendliness have enabled light-emitting diode (LED) lighting to rapidly replace conventional light sources such as incandescent and fluorescent lamps. In particular, AC-LED lighting systems can be directly powered by commercial alternating current (AC) sources; however, they suffer from significant luminance deviation caused by uneven current distribution among LED light-emitting modules. This paper proposes a lighting control method that improves flicker performance while maintaining lamp brightness and effectively reduces luminance deviation in AC-LED lighting. The proposed method reduces luminance deviation by controlling the lighting order of multiple LED light-emitting modules. Among four LED modules, only the required number of modules is continuously turned on, and the lighting priority alternates between rectification cycles. Specifically, during odd rectification cycles, LED modules are activated sequentially in ascending order (11→12→13→14), whereas during even rectification cycles, they are activated in descending order (14→13→12→11). By alternately applying continuous lighting control with opposite activation orders, the proposed reverse alternating lighting control method equalizes the current distribution among LED modules. As a result, luminance uniformity is improved, electrical stress concentration on specific modules is reduced, and the operational lifetime of the LED modules is extended compared with the conventional fixed-sequence lighting control method.

This review introduces Corning’s Ribbon Ceramic process and the broader idea of ribbon ceramics―continuous, ultra-thin ceramic sheets made by tape or slot-die casting and fast, continuous sintering―covering key materials such as Al₂O₃, YSZ/ScSZ, PZT, LLZO, and LCO. Motivated by the need for scalable, energy-efficient ceramic components for electrification (green-hydrogen SOECs), next-generation Li-metal batteries, and compact piezo devices, we summarize capabilities and use cases using only publicly available information. Our main contribution is a clear platform view: continuous roll-to-roll conveyance with minutes-scale firing produces fully dense, fine-grained, high-purity ceramics at ~10-100 μm thickness with smooth native surfaces and controlled shapes, delivered as long rolls (up to ~300 ft), panels (~100 mm wide), or narrow strips (~0.5 mm). Illustrative results include 20-40 μm 3YSZ electrolytes for SOECs (high oxygen-ion conductance, ~1 GPa bend strength), LLZO garnet separators that cycle at 25℃ with interlayers, and free-standing LCO cathode ribbons tunable from dense to ~30% porous. For piezo acoustics, 60-80 μm PZT sheets (d33 ~300 pC/N) enable fine metallization and on-screen speakers, while fast firing reduces volatile loss and yields smaller grains. Together, these advances point to high-volume, lower-footprint manufacturing and faster adoption of novel ceramic membranes and substrates in SOEC/green-hydrogen systems, solid-state or hybrid lithium batteries, RF/power electronics, and piezo applications.

MoS₂ has attracted significant attention as a next-generation semiconductor material to overcome the physical scaling limits of silicon-based devices due to its atomic thinness and excellent electrical properties. However, high contact resistance and the formation of Schottky barriers resulting from interface defects during the metal deposition process remain major bottlenecks that degrade overall device performance and reliability. In this study, we fabricated MoS₂ FETs by employing Sb₂Te₃, van der Waals (vdW) contacts. Minimized interface inhomogeneity was achieved through a hemispherical stamp-based dry transfer of h-BN for device encapsulation. h-BN encapsulation decreased the hysteresis window in the ±25 V gate voltage range from 17 V to 11.5 V compared to un-capped devices, confirming that charge trapping phenomena induced by external environmental factors were suppressed. Consequently, the dry transfer technique of h-BN using a hemispherical stamp demonstrated in this study provides a potential solution for securing the long-term reliability of MoS₂ devices with vdW contact by minimizing interface contamination.

The safety and stability concerns of liquid electrolytes in conventional lithium-ion batteries have accelerated the development of solid-state alternatives. NASICON type ceramics Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) offer promising properties, including high bulk ionic conductivity and good compatibility with lithium anodes. However, their practical application is hindered by grain boundary resistance and relatively low total ionic conductivity. This study investigates the effect of Ta₂O₅ doping on LATP to overcome these limitations. Doping with 5 wt% Ta₂O₅ improved the ionic conductivity to 2.95 × 10-4 S/cm by enhancing lattice structure, reducing grain boundary resistance, and suppressing the formation of secondary phase. Additionally, Ta₂O₅ positively influenced the sintering behavior, resulting in a denser, and more uniform microstructure. These enhancements suggest that Ta₂O₅-doped LATP is a strong candidate for next-generation all-solid-state lithium-ion batteries.

Bismuth layer-structured ferroelectrics with high Curie temperatures have recently attracted significant attention as promising candidates for high-temperature piezoelectric applications. However, the conventional solid-state reaction method entails high-temperature processing that induces bismuth volatilization, thereby degrading device reliability. In this study, we employed a co-precipitation method enabling atomic-level mixing to significantly lower the synthesis temperature of Nb/Tadoped Bi₄Ti₃O₁₂ ceramics compared to the solid-state reaction method. Experimental results demonstrated that the coprecipitation method yielded a pure single phase at 600℃ without intermediate phases. Furthermore, the synthesized nanopowders, with an average size of 100 nm, lowered the onset temperature of sintering shrinkage to 650℃, approximately 200℃ lower than that of the solid-state counterpart. The low-temperature synthesis process proposed in this work is expected to contribute to the performance enhancement of high-temperature piezoelectric devices by effectively suppressing bismuth volatilization and ensuring compositional stability.

This review systematically examines the structural characteristics, compositional design strategies, and recent research trends of layered double hydroxides (LDHs), which are recognized as promising electrocatalyst materials in electrochemical nitrate-to-ammonia conversion. Despite the rapid growth in related research, achieving simultaneous high selectivity and efficiency remains a significant technical challenge due to the complex mechanisms of the nitrate reduction reaction (NitRR) and its inherent competition with the hydrogen evolution reaction (HER). In this study, we analyzed the structural contributions of LDH catalysts for maximizing nitrate reduction efficiency and systematically established key catalyst design indicators required to ensure optimal performance. Specifically, we provide a detailed investigation of the physicochemical mechanisms for enhancing NH₃ production by precisely regulating the adsorption energies of reaction intermediates and maximizing charge transfer efficiency through compositional control and defect engineering. Furthermore, we discuss advanced structural design strategies, such as core-shell tandem structures, MOF-derived architectures, and interlayer anion control, as effective methods for enhancing catalytic performance and optimizing mass transport processes. These insights offer a strategic roadmap for designing high-performance LDH catalysts and represent a critical step toward the practical implementation of sustainable green ammonia production systems, particularly for integration into high-efficiency membrane electrode assembly (MEA) technologies.

Silicon carbide (SiC) MOSFETs provide superior performance compared to traditional silicon devices under hightemperature and high-power conditions, making them particularly valuable for power electronics applications requiring highfrequency switching and high-energy efficiency. As the electric vehicle (EV) market expands, these devices are commonly packaged into six-pack modules, which can show their different electrical characteristics between the bare-die device and the package due to packaging that improves heat dissipation and other properties. This study uses bare-die SiC MOSFETs to explore their intrinsic characteristics and evaluate their performance in a half-bridge configuration. A half-bridge circuit was constructed, and performance was assessed by varying driving frequencies (10 kHz and 50 kHz) and adjusting the duty cycle between 20% and 80%. Analysis revealed that, at a fixed switching frequency, the average output voltage and average output current are proportional to the duty cycle.

Breakdown strength is an essential parameter for evaluating the electrical performance and degradation behavior of cable insulation and IEC 60243 also emphasizes its importance for detecting changes in insulation characteristics due to aging. However, the current IEC standards are mainly limited to specifying electrode configurations and test voltage conditions for breakdown tests, while the influence of insulating oil, is not clearly addressed. In this study, the breakdown strength of a 66 kV wet-type submarine cable was experimentally evaluated using insulating oils with different kinematic viscosities of 10, 100, 500, and 1,000 cSt in order to achieve reliable and reproducible breakdown measurements. The experimental results show that the measured breakdown strength decreases by up to approximately 20% depending on the oil viscosity. This indicates that the viscosity of the insulating oil has a significant influence on the measured breakdown strength during breakdown test. Therefore, it is necessary to perform breakdown strength measurements under identical test conditions, including the physical properties of the insulating oil, to ensure reliable comparison and accurate assessment of insulation performance and degradation characteristics.

The increasing global demand for renewable energy has accelerated the deployment of offshore wind farms, thereby highlighting the need for advanced development and performance assessment techniques for dynamic submarine cables used in floating offshore wind systems. These cables are continuously subjected to combined thermal, electrical, and mechanical stresses, with mechanical loading playing a particularly dominant role. As a result, dynamic submarine cables exhibit degradation behaviors that differ significantly from those of conventional fixed submarine cables. This paper presents the design and implementation of a comprehensive evaluation system capable of applying combined thermal, electrical, and mechanical stresses to dynamic submarine cables. The system was validated using a 66 kV wet type submarine cable through commissioning tests and insulation performance measurements. Electrical stress of 72 kV, thermal stress exceeding 95°C, and mechanical stress corresponding to a bending radius of 20 times the cable diameter over 20 cycles were applied to verify system reliability. The subsequent insulation assessments quantitatively confirmed performance variations induced by the combined stresses. The results demonstrate that the proposed platform is the first system capable of simultaneously applying thermal, electrical, and mechanical stresses to dynamic submarine cables, and its operational performance has been successfully validated. This platform enables realistic reliability evaluation of dynamic cables used in floating offshore wind farms and is expected to improve the overall operational reliability of offshore wind power systems.

As electric vehicles (EVs) are rapidly adopted worldwide, large numbers are now transported by sea on dedicated car carriers. With this trend, concerns are increasing about fires and explosions caused by battery thermal runaway during marine transport, while existing SOC limits before loading remain largely empirical. This study experimentally investigates gas generation and explosion characteristics of EV lithium-ion cells under thermal runaway conditions representative of enclosed vehicle decks. We identify and quantify the main off-gas components and clarify the flammability behavior and explosion limits of key combustible species. The results provide basic data for assessing EV battery accidents at sea and support the development of safer ventilation and gas-management strategies for ships.