- [English]
- Preparation of Flake-shape Cobalt Powders by High-Energy Ball Milling for rSOC Current Collectors
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Poong-Yeon Kim, Min-Jeong Lee, Hyeon Ju Kim, Su-Jin Yun, Si Young Chang, Jung-Yeul Yun
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J Powder Mater. 2025;32(5):383-389. Published online October 31, 2025
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DOI: https://doi.org/10.4150/jpm.2025.00241
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 Abstract
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- Reversible solid oxide cells (rSOCs), which enable two-way conversion between electricity and hydrogen, have gained attention with the rise of hydrogen energy. However, foam-type current collectors in rSOC stacks exhibit poor structural controllability and limited electrode contact area. To address these limitations, this study aimed to convert spherical cobalt powders into flake-type morphology via high-energy ball milling, as a preliminary step toward fabricating flake-based current collectors.
Milling parameters—specifically, the ball-to-powder ratio (BPR), milling time, and process control agent (PCA) content—were varied. At an 8:1 BPR, over 90% of the powder became flake-shaped after 8 hours, while extended milling caused cold welding. In contrast, a 10:1 BPR resulted in dominant fragmentation. The Burgio–Rojac model quantified energy input and defined the optimal range for flake formation. Increasing the PCA to 4 wt% delayed flake formation to 16 hours and induced cold welding, as shown by bimodal particle size distributions. These results support the development of Co-based current collectors for use in rSOCs.
- [English]
- Fabrication and Pore Characteristics of Metal Powder Filters with a Cross-Sealed Honeycomb Shape Using Material Extrusion Additive Manufacturing
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Minji Kim, Min-Jeong Lee, Su-Jin Yun, Poong-Yeon Kim, Hyeon Ju Kim, Juyong Kim, Jung Woo Lee, Jung-Yeul Yun
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J Powder Mater. 2025;32(4):299-308. Published online August 29, 2025
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DOI: https://doi.org/10.4150/jpm.2025.00234
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Abstract
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- The development of high-performance metal filters is essential for maintaining ultra-clean environments in semiconductor manufacturing. In this study, cross-sealed honeycomb filters were fabricated using STS316L powder via material extrusion additive manufacturing (MEAM) for semiconductor gas filtration. The effects of filter geometry (4 or 9 channels) and sintering temperature (850°C, 950°C, or 1,050°C) on performance were examined. First, 4-channel and 9-channel filters sintered at the same temperature (950°C) exhibited similar porosities of 50.08% and 50.57%, but the 9-channel filter showed a higher pressure-drop (0.26 bar) and better filtration-efficiency (3.55 LRV) than the 4-channel filter (0.19 bar and 3.25 LRV, respectively). Second, for filters with the same geometry (4-channel) increasing the sintering temperature reduced porosity from 64.52% to 40.33%, while the pressure-drop increased from 0.13 bar to 0.22 bar and filtration-efficiency improved from 2.53 LRV to 3.51 LRV. These findings demonstrate that filter geometry and sintering temperature are key factors governing the trade-off between air permeability, pressure-drop, and filtration efficiency. This work provides insights and data for optimizing MEAM-based high-performance metal powder filter design.
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