In this study, we developed an automated process technology for the electric resistance spot welding process of direct current fuses (DC fuses), the demand of which is rapidly increasing due to the growing global demand for carbon neutrality and the expansion of the development and utilization of electric vehicles (EVs) and energy storage systems (ESS). To improve the productivity and quality of DC fuse manufacturing, we defined key process variables for the spot resistance welding process, such as welding current, pressure, and welding time. We analyzed the effects of each variable on the heat generation characteristics and melting zone shape during welding. Based on this, we established weld quality evaluation criteria, and through data-driven design of experiments (DOE) and experimental analysis, we derived optimal process conditions and identified defect types and causes. In this experiment, we measured the tensile strength, weld nugget size, and melting degree (no melting, normal melting, and over-melting) at eight points on the upper and lower slopes of the DC fuse (a total of 32 points) using the three-factor, four-level orthogonal array (L16(4 )) method. Through analysis of each main effect and interaction effect, the optimal operating conditions satisfying the tensile strength (1.53 kgf) and weld nugget size (1.47 mm) specifications were identified: a welding current of 6.5 kA, an applied pressure of 1.75 kgf/cm , and a welding time of 1.5 seconds. Furthermore, the strong interaction between current and time confirmed that heat input balance is a key factor in weld quality, with applied pressure playing a supplementary role in stabilizing this balance. Based on this, an automated point resistance welding system was designed and an integrated architecture of mechanical, electrical, instrumentation, and data/MES was established to enable current-time-based heat input control and applied pressure stabilization. A real-time production process monitoring system was established, and a prototype capable of process sequence control was manufactured and successfully tested in the field. This study is expected to contribute to increased corporate sales by enabling high-reliability quality control and enhanced productivity through precision welding of plate-shaped DC fuse elements. Furthermore, the results of this study are expected to contribute to improving the technological level required for the development of electric vehicles and energy storage systems (ESS).
This study reconceptualizes CMF (Color, Material, Finish) as a design instrument for autonomous logistics service robots and proposes an integrative design-service strategy suitable for field deployment, developed via a participatory, service-design process based on the Double Diamond framework [4]. Through surveys, in-depth interviews, field observations, and workshops, we identified user requirements and environmental constraints and derived design principles centered on the visual, tactile, and storytelling-related functions of CMF. We designed and prototyped a set of modular robot concepts from a CMF perspective-robot-arm-integrated, cart-type, lift/roller-type, air-purification/disinfection, and fully integrated units- and evaluated them with preliminary users and domain experts to assess qualitative and quantitative effects. Results indicate that a design-driven application of CMF enhances initial user acceptance, improves the intuitiveness of state awareness, reduces user learning time by an average of 40 similar to 45 %, and increases users' perceived psychological collaboration with the robot. The paper concludes by presenting CMF design guidelines that account for coordination with logistics environments, principles for modular design, and practical considerations for implementation and operation.
Currently, the only established method for stable SiC single-crystal growth is the physical vapor transport (PVT) technique. However, conventional PVT systems often require optimizing the hot-zone and insulation layouts to compensate for thermal non-uniformities inherent in large-diameter crystal growth. To address these limitations, a resistive-heating-based PVT approach has been proposed, enabling more precise and uniform thermal-field control through flexible internal heater design. In this study, a resistive-heating-type PVT furnace was newly constructed, and 4-inch SiC single crystals were grown by optimizing the hot-zone and insulation configurations. The grown crystals exhibited a slightly convex shape and achieved an average growth rate of 116 & micro;m/hr. Ultraviolet fluorescence (UVF) imaging revealed that 4H-SiC crystals containing locally distributed 6H-SiC polytype regions were obtained. High-resolution X-ray diffraction (HR-XRD) measurements showed full width at half maximum (FWHM) values ranging from 71.1 arcsec to 115.9 arcsec. Raman spectroscopy confirmed consistent crystal quality, with the FTO (2/4) phonon mode exhibiting a FWHM of 5.5 cm(-1) to 5.9(-1) cm . Except for areas with 6HSiC polytypes, the dominant 4H-SiC regions exhibited nearly stress-free characteristics with the FTO (2/4) peak close to 776 cm(-1) of typical of free-standing 4H-SiC. These results demonstrate that resistive-heating-based PVT method can yield high-crystallinity, low-stress SiC single crystals, provided that polytype stability is maintained during growth.
In the growth of silicon carbide (SiC) single crystals using the induction-heated physical vapor transport (PVT) method, designing an innovative hot-zone structure is essential to mitigate internal thermal stress. Key design parameters, such as the top insulation characteristics and graphite seed holder geometry, play a critical role in shaping the thermal distribution. This study focuses on modifying the thickness and cavity area of the seed holder platform to achieve an optimal axial temperature gradient and uniform radial thermal distribution. Three cavity-structured designs were evaluated based on the cavity surface area relative to the platform: Design A (0 %, baseline), Design B (50 %), and Design C (80 %). Numerical simulations and experimental growth were conducted under identical growth conditions. The results revealed that the radial temperature gradient (shape of the crystal) from the center to the periphery decreased as the cavity area increased, yielding gradients of 2.6 degrees C (concave) for Design A, 1.5 degrees C (flat) for Design B, and 1.8 degrees C (flat) for Design C. Comprehensive characterization via XRD 2theta-omega scans, Raman mapping for FWHM of the FTA phonon, and defect (etch pit) density analysis through surface etching confirmed that Design B exhibited the highest quality crystals. Specifically, Design B exhibited the lowest internal stress of-0.0033 GPa, superior crystalline uniformity with an average FWHM of 44.1 arcsec, and significantly reduced defect density. These findings demonstrate that precise cavity engineering of the seed holder platform is a straightforward yet highly effective strategy for achieving high-quality SiC crystals.
As air and water quality continue to deteriorate, the market is increasingly saturated with products whose effectiveness has not been clearly verified. In response, this project aims to develop a future-oriented, compact, and modular product with enhanced performance and clearly demonstrated effectiveness. To realize this objective, the project will place emphasis on the development of UV-C LED device and process element technologies, together with highefficiency and miniaturization technologies based on photocatalytic applications. Through this research, we present 'Air purification and disinfection product' study involving the development of a UV-C LED device with a 300 nm emission wavelength and the achievement of a 70 % acetaldehyde removal rate.
This study investigates the effects of spray distance (250, 300, and 350 mm) and gun traverse speed (4, 7, and 10 mm/s) in the High Velocity Oxygen Fuel (HVOF) process on the microstructural, crystallographic, and mechanical properties of WC-10Co-4Cr coatings. The WC-Co-Cr feedstock powder consists of agglomerated 1 similar to 2 mu m primary particles, which inherently promotes the formation of partially molten and unmelted particles during spraying due to heterogeneous internal and external melting behavior. When the spray distance was reduced to 250 mm at a gun traverse speed of 7 mm/ s, the shortened particle flight time resulted in insufficient melting, leading to an increased fraction of unmelted particles and interfacial delamination (9.48 %). As a consequence, poor inter-splat bonding caused a reduction in Almen/bending thickness (90 mu m) and an increase in residual stress (0.35 mm). In contrast, at a spray distance of 350 mm, the extended flight time increased particle exposure to oxygen, resulting in a higher defect content (0.872 %). Despite this, stabilization of the jet flow improved particle impact angle and lamellar stacking, yielding the highest bonding strength (77.3 MPa) and hardness (1,400 Hv). Variations in gun traverse speed significantly altered the surface thermal history and splat solidification behavior. Compared with the reference condition (300 mm, 7 mm/s), both slower (4 mm/s) and faster (10 mm/s) traverse speeds produced denser lamellar structures and enhanced splat continuity. At 4 mm/s, localized re-melting and increased binder fluidity reduced porosity but slightly degraded bonding strength due to excessive thermal input. Conversely, at 10 mm/s, suppressed surface overheating and reduced particle scattering led to a more uniform splat structure, accompanied by a slight increase in W2C relative peak intensity and improved bonding strength (74.1 MPa). Overall, spray distance and gun traverse speed are critical parameters governing particle melting, cooling, flight stability, and binder continuity, which collectively determine splat morphology, defect distribution, decarburization behavior, and mechanical performance of WC-Co-Cr coatings.
The advancement of Artificial Intelligence (AI), mobile, and Internet of Things (IoT) technologies has driven the demand for high integration, high-speed signal transmission, and fine patterning in semiconductor packaging. While organic substrates are commonly used, they present limitations in planarity, thermal/mechanical stability, and dielectric properties. Glass substrates offer superior characteristics, but their brittleness hinders fine-pattern processing, particularly in forming Through Glass Via (TGV). This study presents a TGV fabrication method using photosensitive glass based on Ce- and Agdoped lithium aluminosilicate (LAS). Selective crystallization of lithium metasilicate (LMS) was achieved via UV exposure and thermal treatment, followed by hydrofluoric acid etching to form vias. Key process parameters were analyzed for their impact on via formation and quality, and the proposed process enhanced controllability over via morphology while offering practical insights into advanced packaging applications using photosensitive glass.
Single-phase alpha-, beta-, and gamma-MnO2 nanoparticles with high crystallinity were successfully synthesized by a hydrothermal process using different Mn precursors, such as Mn(OAc)(2), MnSO4, MnCl2, and Mn(NO3)(2). The crystal structure and morphology of the MnO2 particles could be effectively controlled by changing the Mn source. The use of Mn(OAc)(2) and MnSO4 as precursors resulted in rod-shaped alpha- and beta-MnO2 particles, whereas MnCl2 and Mn(NO3)(2) yielded aggregated angular nanoparticles of gamma-MnO2. X-ray photoelectron spectroscopic analysis revealed that beta-MnO2 had a high ratio of Mn4+ and O-latt on the particle surface, whereas alpha- and gamma-MnO2 samples had a lower valence state of Mn, such as Mn3+ and Mn2+, on the surface, and the ratio of O-latt was also relatively low.
This paper presents a numerical simulation of double diffusive convection in a rectangular enclousre during physical vapor transport of Hg2Cl2. The flow characteristics are numerically investigated as a function of the partial pressure of Br-2 at 10 Torr and 200 Torr at a temperature difference of 10 degrees C (290 degrees C -> 280 degrees C) between the source and crystal regions, and the velocity vectors, streamlines, isotherms, and isomass concentration contours are presented. In addition, both the average Nusselt number and the average Sherwood number decrease linearly and exponentially, respectively, with increasing a partial pressure of Br-2. For pressures of Br-2 for 10 Torr and 200 Torr, the average Nusselt number in the crystal region is larger than in the crystal region, and conversely, the average Sherwood number in the crystal region is three times larger than in the source region.
In this study, polydimethylsiloxane (PDMS)-Cu2O composites were fabricated to enhance the triboelectric performance of triboelectric nanogenerators (TENGs), and the effects of synthesis conditions and filler content were systematically investigated. Cu2O nanoparticles were synthesized through an alkaline precipitation followed by ascorbic acid reduction, and their crystallinity and microstructure were tailored by controlling the synthesis temperature. XRD and SEM analyses revealed that higher synthesis temperatures promoted more uniform particle size distribution. When incorporated into the PDMS matrix, the Cu2O fillers significantly improved the output performance of the TENG devices. The pristine PDMS-based TENG exhibited a voltage of 119 V and a current density of 28.69 mA/m(2), whereas the composite with 7 wt% Cu2O achieved 410 V and 44.76 mA/m(2), corresponding to approximately 3.4- and 1.6-fold enhancements, respectively. Dielectric measurements confirmed that the effective permittivity of the composites increased with Cu2O loading, directly contributing to enhanced charge storage capability. Moreover, the well-dispersed Cu2O particles generated micro-scale surface roughness, which enlarged the effective contact area, while interfacial charge trapping at the Cu2O-PDMS boundary contributed to reduced charge recombination and improved output stability.
Hexaferrites with nominal chemical formula of Sr 2-y CayZn2-N CozFe28Ox (y = 0, 0.5; z = 0, 1, 2) were synthesized by a solid state reaction to investigate the phase evolution, magnetic behavior, and electromagnetic (EM) wave absorption properties. X ray diffraction revealed that the Sr2Co2Fe28Ox sample (y = 0, z = 2) calcined at 1300 degrees C formed a nearly single X type phase, whereas the Ca substituted samples (y = 0.5; z = 0, 1) exhibited dominant W type phases. The magnetic properties strongly depended on cation substitution and phase composition: the Sr1.5Ca0.5ZnCoFe28Ox sample (y = 0.5 and z = 1) showed the highest saturation magnetization (M-S) of 75.7 emu/g and the lowest coercivity (H-C) of 63 Oe. Microwave absorption analysis of epoxy (10 wt%) composites indicated excellent reflection loss (RL) performance with RLmin = -44.9 dB at 8.5 GHz (2.6 mm thickness) for Sr1.5Ca0.5ZnCoFe28Ox and RLmin = -49.0 dB at 5.6 GHz (3.3 mm) for Sr1.5Ca0.5ZnCoFe28Ox. These results demonstrate that X and W type hexaferrite composites possess high permeability, and broadband EM wave absorption capabilities suitable for X band (8-12 GHz) absorber applications.
This study investigates the effect of Czochralski (CZ) growth conditions on the structural and optical properties of high-purity CaF2 single crystals, with a focus on application in deep ultraviolet (DUV) optical applications. Two (111) single crystals, grown under different pulling and cooling rates (C2308 and C2408), were compared to elucidate the influence of thermal gradients on residual stress development and defect formation. The C2408 (slow-pulling, gradual-cooling) condition reduced thermal gradients, resulting in the suppression of structural defects and stress birefringence. These results demonstrate that controlling growth and cooling rates is a critical factor in determining the overall structural and optical properties of CaF2 single crystals, including crystallinity, stress-induced birefringence, and defect density.
In spray forming the variations of droplet temperatures with flight distance are very important in determining the thermal condition and overall solid fraction of the spray at the point of deposition. Gas and droplet velocities, droplet temperature and solid fraction with flight during spray forming have been predicted in Inconel 718 alloy. As the size of the droplet increases, the starting and completing points of solidification move toward a longer flight distance, and the solidification process also proceeds over a wider range of flight distance. The solidification mechanism of the droplets has a relatively small effect on the dynamic and thermal behavior of the spray droplets, while the size of the droplets has a strong effect.
The optimization of growth conditions, hot zone design, and insulation structure is crucial for high-quality SiC single crystal growth using Physical Vapor Transport (PVT) techniques. Inadequate growth design can lead to polytype inclusions, crack formation, and increased defect density within the crystal, ultimately deteriorating the quality of the final SiC single crystal. In this study, a new insulation design was developed to enhance the axial and radial temperature gradients at the top of the crucible compared to the conventional graphite insulation structure. Additionally, nitrogen gas was employed during the growth process to ensure polytype stability. Simulations using VR reactor software were conducted to analyze the internal temperature distribution within the crucible and the migration pathways of SiC source chemical species resulting from the enhanced upper insulation. Ingots grown using each design achieved growth rates in the mid-100 & micro;m/hr range. In crystals grown with the conventional Design A, polytype inclusions and cracking were observed throughout the ingot. In contrast, crystals grown with Designs B and C showed significant suppression of polycrystalline formation at the ingot periphery and markedly improved crystallinity. Notably, the application of Design C, which featured enhanced upper crucible insulation and nitrogen gas employed during the growth process, resulted in high-quality 4H-SiC crystals.
This study investigates the effects of MoO excess on the crystal structure and microstructure of MnTeMoO (MTMO), a candidate ULTCC material for high-frequency devices. MTMO powders were prepared by solid-state reaction with 0.5, 1.0, and 2.0 mol% MoO additions and sintered at 700 C. X-ray diffraction confirmed a single orthorhombic phase across all samples without secondary phases. SEM analysis suggested excess MoO could modify the chemistry of interface liquids, reduce grain shape anisotropy, and regulate grain growth. This reduction in anisotropy is attributed to increased atomically disordered interfaces and a lowered critical driving force for grain growth, consistent with the predictions of two-dimensional nucleation and growth theory. The findings demonstrate that controlled MoO addition enables microstructure tuning, improving process compatibility and performance for ULTCC applications.
beta-Ga2O3, with an ultrawide bandgap of similar to 4.9 eV, a high critical electric field, and excellent stability, has emerged as a promising candidate material for next-generation power and optoelectronic devices. Wafer technology has rapidly advanced through large-diameter bulk growth using the EFG (Edge-defined Film-Fed Growth) and VB (Vertical Bridgman) methods; however, exploiting the strong anisotropy inherent to its monoclinic crystal structure remains a critical challenge. The electrical and optical properties vary significantly with crystallographic orientation, both out-of-plane and in-plane of beta-Ga2O3. In particular, the (100) surface has been widely employed for device fabrication but has attracted attention due to its low surface energy and tendency to form twin boundaries. In this study, unintentionally doped (UID) beta-Ga2O3 single crystals grown by the EFG method were processed into a (100) oriented sample, and its orientation was identified using high-resolution X-ray diffraction (HR-XRD) and Raman spectroscopy. Raman analysis revealed that phonon mode intensities varied markedly among the orientations depending on lattice symmetry. Angle-resolved Raman measurements on the (100) surface further showed that A(g) and B-g modes exhibited 2-fold, 4-fold, or complete symmetry, indicating a strong dependence on the interaction between the incident light polarization and the crystallographic orientation of beta-Ga2O3. These results demonstrate that Raman spectroscopy is an effective, non-destructive technique for probing crystallographic orientation and anisotropy in beta-Ga2O3 single crystals, providing fundamental insights for device design, optimization of wafer fabrication process, and the evaluation of stress and defects in beta-Ga2O3-based technologies.
In order to grow AlN single crystals, HVPE (hydride vapor phase epitaxy) method was used and the sapphire substrates were adapted to the seed for the growth of single crystal AlN. The nitrogen gas, the carrier gas, was used to supply the HCl gas and NH3 and to keep the flow in the reactor. This redearch was carried out in order to evaluate the growth behavior of AlN crystal growth due to the change of the V/III gas ratio. By fixing the amount of nitrogen carrier gas, which is supplied during growth, there was a change in the grown crystal phase depending on the change in the supply ratio of nitrogen (N) and aluminum (Al). The grown AlN thick films had the variation result along the change of the V/III gas ratio. The growth behavior of AlN crystal was characterized by observation using an optical microscope and SEM, and the results are discussed and reported.
This study aimed to reduce the weight and improve the performance of an electric vehicle (EV) front axle knuckle by utilizing topology optimization using CFRP materials. Aluminum alloy-based steering knuckles are currently used in major vehicle models production. To further improve the energy efficiency and maneuverability of electric vehicles and reduce unsprung mass, CFRP composites material change and finite element analysis and topology optimization technology were applied to predict weight loss and performance of the front steering knuckle carriers. Through the application of composite materials and the optimal design, we achieved a weight reduction of about 50.7 % compared to the existing aluminum alloy steering knuckle products. From the analysis results under various load conditions (static loading, driving, braking, cornering), it was found that the shape of the CFRP steering knuckle can improve stress distribution and demonstrate excellent safety while maintaining high rigidity and stability. In addition, it is expected that this weight reduction will be applied to contribute to the improvement of vehicle energy efficiency and driving performance. We intend to apply these research results to the industrial field and use them as technical data for the development of new product concepts.
Nickel selenides have emerged as promising electrocatalysts for the oxygen evolution reaction (OER) due to their high conductivity, tunable electronic structure, and ability to transform into catalytically active oxyhydroxides under alkaline conditions. In this study, nickel selenides were directly synthesized on Ni foam via a simple hydrothermal process using elemental selenium powder and hydrazine as precursors. The synthesis temperature was systematically varied from 120 to 200 degrees C to investigate its influence on phase formation, morphology, and electrocatalytic activity. Structural analysis by X-ray diffraction (XRD) revealed a gradual evolution from poorly crystallized products at low temperature to highly crystalline NiSe2/Ni3Se2 phases at elevated temperature, with the NS-160 sample (160 degrees C) exhibiting the most balanced crystalline structure. FE-SEM and EDS analyses confirmed that NS-160 possessed a uniform nanosheet-like morphology and a homogeneous Ni-Se distribution. Electrochemical evaluation demonstrated that NS-160 delivered the best OER performance, requiring the lowest overpotential (eta(100)) to achieve 1 00 m A center dot cm(-2), the smallest Tafel slope, and the lowest charge-transfer resistance, along with the highest double-layer capacitance (C-dl) and electrochemically active surface area (ECSA). These results highlight that optimized crystallinity and morphology at 160 degrees C yield superior electrocatalytic activity by maximizing accessible active sites and facilitating rapid charge transport. This work provides a cost-effective and scalable route for fabricating efficient nickel selenide-based electrodes for alkaline water electrolysis.
We investigated optical anisotropy and homogeneity of a n-doped InP single crystal wafer grown by Vertical Bridgeman method. As circularly polarized light at 1,060 nm wavelength was incident to the wafer surface, output light polarization was analyzed to see optical birefringence-induced change in polarization. We also scanned the position on the wafer to which light was incident to see position-dependent optical anisotropy of the wafer, i.e, inhomogeneity. The change of polarization was seen to be correlated to some extent with etch pit density of the wafer. The polarization-based optical analysis can also be applied to other kinds of single crystal wafers which have crystallographic symmetries for the shake of straightforward examination of crystal defects such as dislocations as a function of wafer position and homogeneity of optical anisotropy.
