Carbon capture and storage is a vital strategy for mitigating rising atmospheric carbon dioxide, and metal–organic frameworks (MOFs) have gained attention as promising sorbents. Numerous simulations have examined factors governing CO2 capture in MOFs—such as diffusion in MOF-74 under varying temperatures and process modeling of MOF-5—but most were limited to specific structures or conditions, hindering a systematic understanding of diffusion across diverse MOFs. Conventional computational methods also face constraints: density functional theory mainly provides static energy evaluations, while molecular dynamics relies on fixed force fields with poor transferability and an inability to describe reactive events. To overcome these limitations, this study employs molecular dynamics simulations driven by neural network potentials to evaluate CO2 diffusivity in 17 types of MOFs. Results reveal significant variation in transport behavior, with zeolitic-imidazolate framework-3 showing the highest diffusivity and MOF-74 the lowest—an approximately 19-fold difference. These findings highlight the capability of neural-network-based molecular dynamics to deliver consistent and quantitative assessments of CO2 transport in MOFs, providing a reliable framework for the rational design of next-generation capture materials.
Secondary batteries are crucial for eco-friendly systems, but existing technologies struggle with energy density and safety issues. This study aims to develop a next-generation battery utilizing quasi-solid electrolytes (QSE), which combine the advantages of both liquid and solid electrolytes. However, QSEs often lack the mechanical strength necessary to prevent lithium dendrite growth. To address this challenge, two strategies were proposed and experimentally validated. The first strategy involves creating a QSE-separator composite (QSE-PI) by integrating QSE with a polyimide (PI) separator. Among the various options, PI with a thickness greater than 20 μm and a pore size of 2-5 μm exhibited superior electrolyte absorption and dendrite suppression. This configuration allowed for rapid lithium plating/stripping, high ionic conductivity (1.7 × 10-3 S cm-1), and excellent Coulombic efficiency (99.94%).The second strategy incorporates silica (SiO2) as a ceramic filler in the QSE-PI to enhance mechanical strength and ion transport. The addition of SiO2 disrupted polymer crystallinity, increased the amorphous regions, and effectively suppressed dendrite formation. Notably, SiO2 particles larger than 10 μm improved cycle stability, with the composite maintaining performance for over 50 cycles, compared to only 30 cycles for the version without filler.
This paper extensively explores and analyzes the latest research trends in Ionic Polymer-Metal Composites (IPMC) sensors. IPMC sensors are known for their flexibility, lightness, and high responsiveness. They show great promise across different fields. They can respond sensitively to various stimuli such as mechanical deformation, humidity, and pressure, making them ideal for bio-responsive detection, health monitoring, and energy harvesting. This paper introduces actuation and sensing mechanisms of IPMCs, discusses their manufacturing processes, and explores how these processes can influence the responsiveness and stability of sensors. Moreover, through case studies of IPMC-based research that can perform self-sensing functions, it presents possibilities brought by the integration of sensors and actuators. This paper emphasizes the potential for research and development of IPMC sensors to expand into various industrial fields and explores ways to continuously improve the accuracy and reliability of sensors. IPMC-based sensors are expected to play a significant role in advancing medical devices and wearable technologies, thereby facilitating innovation in the field.
In this study, to improve the performance of a solid oxide fuel cell based on a porous metal support, a fuel cell using a multi-layered anode functional layer was fabricated and electrochemical performance analysis was performed. Surface and cross-sectional microstructures according to particle size control were confirmed through FE-SEM. The pore size of the multi-layer anode functional layer was gradually reduced compared to that of a single-structure anode functional layer. As a result, it was confirmed that the surface roughness was lower than that of the single structure. This led to a reduction in polarization resistance through smooth transmission of gas generated from the electrode. As a result, it was confirmed that electrochemical performance was improved by more than 1.25 times in fuel cells using a multi-layered anode functional layer compared to that with a single structure.
This research developed a CAM S/W, which generates an adaptive 5-axis tool path, to optimize the quality of Direct Energy Deposition (DED) 3D printing. After reconstructing part shapes and generating printing paths in each shape, the path simulation including automatic collision detection was implemented. Productivity and printing quality were improved through equipment improvement and process optimization. In addition, high-quality parts with desirable physical and mechanical properties were produced by generating an adaptive 5-axis path specialized in the printing process that reflects various physical phenomena and monitoring results. Finally, the performance of CAM S/W was verified through the production of prototypes for industrial components.
We have developed a direct conductive patterning method with micro-scale line widths using the laser-induced-forward transfer (LIFT) and liquid metal. As this method does not need post-thermal processing, there is no thermal damage even on heat-sensitive polymer substrates by low-power laser irradiation on the dynamic release layer (DRL). Unlike other liquid metal patterning processes, this procedure can easily achieve fine line widths of a few tens of micrometers corresponding to laser spot size. The solid-state UV pulse laser with 266 nm wavelength and 20 ns pulse duration was used to transfer Eutectic Gallium Indium (EGaIn) liquid metal and the results for the single and multi-pulse laser irradiation were investigated to determine the effective process conditions. The applicability of flexible circuit fabrication and selective circuit repair was successfully tested on Polyimide (PI) substrate. After the LIFT process, the electrical properties of liquid metal on the pattern were measured to be approximately 5~8 x 10-3 Ω/m of resistance.
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Study on Micro Grooving of Tungsten Carbide Using Disk Tool Min Ki Kim, Chan Young Yang, Dae Bo Sim, Ji Hyo Lee, Bo Hyun Kim Journal of the Korean Society for Precision Engineering.2024; 41(2): 123. CrossRef
In this study, we demonstrated a triboelectric nanogenerator composed of a vertical column, and a cylindrical shell, for omnidirectional wind energy harvesting. With a simple structure using a metal wire, the height between the two triboelectric materials can be maintained, and the Al coated shell can also be electrically connected to the electrode. When the shell is deformed by wind, its Al layer and Polytetrafluoroethylene (PTFE) on the outside of the column can be triboelectrically charged. Thus, wind energy can be harvested through a triboelectric energy conversion mechanism. In particular, due to the high flexibility of the shell, the nanogenerator operates even at wind speeds as low as 1 m/s. Although the output voltage is asymmetrical depending on the wind direction due to the metal wire, it was experimentally confirmed that the device can harvest wind energy from all directions. The measured output RMS power was approximately 15 μW at a wind speed of 6 m/s.
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Wind-powered Triboelectric Nanogenerator Using Contact-separation of Two Cylindrical Structures Jong-An Choi, Jingu Jeong, Mingyu Kang, Soonjae Pyo Journal of the Korean Society for Precision Engineering.2023; 40(12): 939. CrossRef
The ultrasonic metal welding technique has been widely used because of the need to weld different materials for meeting high quality performance requirements. The key part in this type of welding is the horn, which plays an important role in the weld quality. Longitudinal vibration has so far been the most popular vibration mode for ultrasonic horns, but the longitudinal mode coupled with torsional mode is gaining a lot of attention these days owing to its better performance compared to the pure longitudinal mode. Although there are many studies on the performance of these two mode horns, comparative studies based on the performance of these two modes, particularly in ultrasonic metal welding, are very rare. This study focuses on the welding performance comparison of these two horns with 20 kHz resonant frequency. Experimental results show that the performance of the longitudinal-torsional horn is better than that of the longitudinal horn in terms of welding strength.
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Trade-off between dynamic recrystallization and material ejection during ultrasonic welding of cylindrical cell current collector plate and positive terminal Mounarik Mondal, Savyasachi Nellikode, Seong-Beom Park, Jun Mitsuyuki, Soomin Lee, Do-Hyeong Kim, Yeong-Do Park The International Journal of Advanced Manufacturing Technology.2025; 137(11-12): 5837. CrossRef
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The necessity of converting toxic gas has arisen from the usage of perfluorinated compounds (PFCs), volatile organic compounds (VOCs), and hydrocarbon gases in the semiconductor process and laboratories. Also, recent strong regulations on the emission gas from vehicles also present the need for the highly efficient chemical conversion of toxic emission gases. In this study, we present the fabrication of platinum and ruthenium alloy metal catalysts on the yttria-stabilized zirconia balls, and the application of the metal catalysts to the catalytic converter for methane oxidation. The platinum and ruthenium alloy metal catalysts showed better performance than the platinum catalyst, i.e., 75% increase in the methane conversion efficiency at 500℃. Such improvement seems to be because of the facile oxygen supply from the ruthenium surface. Also, the platinum and ruthenium alloy catalysts with the doped cerium oxide interlayer showed better thermal stability than the platinum and ruthenium alloy metal catalysts, possibly because of the stronger bonding between the metal and oxide support.
As products life cycles are becoming shorter, the reduction of die and mold manufacturing cost and time is becoming more crucial in the machinery, automotive, and electronics industries. Over the past decades, many initiatives have been made to develop high performance free-machining steels without significant degradation of mechanical properties. To develop a modified AISI P20 free-machining steel, we studied the effects of B, N, and S additives on the variations of the cutting forces and metal structures such as grain size, density, and distribution of free-machining inclusions. From a set of experiments, it was observed that an appropriate addition of B and N additives reduces the resulting cutting force by approximately 6.3% and delays the tool wear progress. During the solidification B and N additives form hBN precipitates, with a layered and planar structure, within the steel matrix. The hBN precipitates’ weak shear strength results in lowering the required milling force. It is also confirmed that machinability is prominently improved when a large number of microsized hBN precipitates are distributed uniformly in the steel matrix. This study could contribute to the development of high performance BN-added free-machining steels for die and mold applications.
Metal additive manufacturing using electron beam melting (EBM) process applies electron beam for heating, sintering, and melting of powders to fabricate a three-dimensional component. The component may contain residual porosity internally and may be subjected to poor surface finish externally. To improve the quality of the surface finish and densification, re-melting is conducted. The purpose of this paper was to estimate the appropriate process conditions for a plasma electron beam remelting process using heat transfer finite element analyses (FEAs). The impact of the travel speed of table and thickness of the deposited part on temperature distributions were examined. The size of molten pool was estimated from the results of the thermal FEA. From the estimated size of molten pool, the travel speed of table and the hatch spacing between remelting tracks are discussed and selected as the appropriate process conditions for electron beam re-melting process from the perspective of minimum overlapping region of the molten pool.
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Investigation of elimination of powder spreading in manufacture of thin and wide preheating beads from Co–Cr alloy powders using a P-ebeam Ho-Jin Lee, Dong-Gyu Ahn Journal of Materials Research and Technology.2021; 14: 1873. CrossRef
We propose a novel fin-tube expanding process using a spiral-grooved-expanding ball, prepared by the metal additive manufacturing process, to improve heat exchange performance in a fin-tube type heat exchanger. In this study, deformation of inner grooves in a tube, was minimized during the expanding process. For this, we developed lab-scale expanding equipment, and a spiral-grooved-expanding ball, was newly designed and fabricated. Comparing to a conventional tube expanding process, it was deduced that a deformation rate of groove height was reduced to approximately 8.3%, when the proposed process was used. Through this fundamental study, we validate that the developed process can be used to fabricate large-surface grooved tubes, for application to a high efficiency heat exchanger.
The objective of this study was to investigate the effect of heat treatment on electrochemical performance of aluminum (Al)-air battery. We prepared a pure Al and an annealed Al under an annealing environment [a mixture gas of Ar (97%) and H2 (3%)] of 400°C for 1 hr. Based on electron backscatter diffraction analysis of Al at the anode, the relative misorientation of the pristine Al was higher than that of the annealed Al. Electrochemical performances of the pristine Al-air and the annealed Al-air were also compared. The annealed Al-air battery showed slightly higher power density than the pristine Alair battery. These results suggest that annealing with heat treatment is an important process to improve the electrochemical performance of aluminum-air battery.
Chiefly, the metal wire-feed and laser additive manufacturing (AM) is a deposition process to produce larger mechanical parts required for aerospace, shipbuilding, automobile, and mold repair industries. The principal advantage of metal wire-feed AM is the high deposition rate compared to an assisted metal powder-feed AM, and metal powder-based fusion AM. During the wire-feed deposition process, the feed orientation is a critical parameter managed at all stages of processing. A better surface finish is attained when the melted wire flows smoothly through the process, and a wire feed direction that is utilized opposite to the deposition direction yields the best results. To improve the surface quality of metal 3D printing, we designed a rotating wire feeder, the feed direction of which varies with the direction of deposition; all free-form lines which thus exhibit identical surface qualities. Here, we use a rotating stage to orient the wire-feed direction according to the bead direction, a slip ring to supply electrical power to the feeder motor, and utilized two rotating channels on a plate to supply Ar gas and extract fumes safely during the processing stage. We evaluated the rotating wire feeder by building various parts as needed to the equipment.
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Directed Energy Deposition (DED) Process: State of the Art Dong-Gyu Ahn International Journal of Precision Engineering and Manufacturing-Green Technology.2021; 8(2): 703. CrossRef
Estimation Method of Interpass Time for the Control of Temperature during a Directed Energy Deposition Process of a Ti–6Al–4V Planar Layer Bih-Lii Chua, Dong-Gyu Ahn Materials.2020; 13(21): 4935. CrossRef
Investigation of Influence of Laser Parameters and Powder Porosity on Thermal Characteristics in the Powder Bed of a SLM Process Kwang-Kyu Lee, Ho-Jin Lee, Hyun-Sik Kim, Dong-Gyu Ahn, Yong Son Journal of the Korean Society for Precision Engineering.2019; 36(8): 761. CrossRef
CAPP for 3D Printer with Metallic Wire Supplied from the Front Ho-chan Kim, Jae-gu Kim Journal of the Korean Society of Manufacturing Process Engineers.2018; 17(5): 155. CrossRef
A study about superhydrophobic surface started from the analysis of lotus leaf, and superhydrophobic surface fabrication methods have been researched. These methods cannot be used on various metals because the fabrication methods have complex and material-selective processes. In this work, we report a simple fabrication method using abrasive blasting and a self-assembled monolayer coating to produce a superhydrophobic surface. Abrasive blasting was used to create microstructures on metal surfaces. Random peak and valley microstructures were created after abrasive blasting, and a surface profile was measured to analyze the relationship between blasting pressure and a roughness parameter. A hydrophobic material coating was performed by a self-assembled monolayer method. Six kinds of metal surfaces displayed superhydrophobic properties. This utilitarian method could be applied to diverse applications.
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