Journal of Powder Materials

Research Articles

[Korean]
Flexible Hybrid Energy Harvester based on Thermoelectric Composite Film and Electrospun Piezopolymer Membranes: Hyomin Jeon, Cheol Min Kim, Hyeon Jun Park, Bitna Bae, Hyejeong Choi, HakSu Jang, Kwi-Il Park; J Powder Mater. 2025;32(2):104-112. Published online March 4, 2025; DOI: https://doi.org/10.4150/jpm.2024.00458; Funded: National Research Foundation of Korea, National Research Foundation of Korea

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Abstract PDF: A hybrid energy harvester that consisted of thermoelectric (TE) composite film and electrospun piezoelectric (PE) polymeric membranes was constructed. TE composites were fabricated by dispersing inorganic TE powders inside polyvinylidene fluoride elastomer using a drop-casting technique. The polyvinylidene fluoride-trifluoroethylene, which was chosen due to its excellent chemical resistance, mechanical stability, and biocompatibility, was electrospun onto an aluminum foil to fabricate the ultra-flexible PE membranes. To create a hybrid energy harvester that can simultaneously convert heat and mechanical energy resources into electricity, the TE composite films attached to the PE membrane were encapsulated with protective polydimethylsiloxane. The fabricated energy harvester converted the outputs with a maximum voltage of 4 V (PE performance) and current signals of 0.2 μA (TE performance) under periodical heat input and mechanical bending in hybrid modes. This study demonstrates the potential of the hybrid energy harvester for powering flexible and wearable electronics, offering a sustainable and reliable power source.

[Korean]
Effect of the Initial Porosity of Needle Coke-Pitch Carbonized Blocks on Impregnation-Related Physical Properties: U-Sang Youn, Sang-Hye Lee, Jae-Seung Roh; J Powder Mater. 2025;32(2):138-144. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2025.00038; Funded: Kumoh National Institute of Technology

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Abstract PDF: Carbonized blocks with different porosities were prepared by varying the particle size of the filler and subsequent impregnation. The impregnated carbonized blocks were re-carbonized. The use of smaller particles in the filler in the carbonized block was associated with larger porosity, smaller pore size, and a higher impregnation ratio. The block with the smallest average particle size (53 μm), CB-53, had a porosity of 35.9% and pores of approximately 40 μm, while the block with the largest average particle size (413 μm), CB-413, had a porosity of 30.5% and pores of approximately 150 μm. CB-53 had the highest bulk density, electrical resistivity, flexural strength, and impregnation ratio. This is due to the large porosity, which is believed to be due to the presence of more interfaces between particles during the re-carbonization of the impregnated carbonized block, resulting in a better pore-filling effect.

Critical Review

[English]
A Review of Recent Developments in CoCrFeMnNi High-Entropy Alloys Processed by Powder Metallurgy: Cheenepalli Nagarjuna, Sheetal Kumar Dewangan, Hansung Lee, Eunhyo Song, K. Raja Rao, Byungmin Ahn; J Powder Mater. 2025;32(2):145-164. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2024.00430; Funded: National Research Foundation of Korea

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Abstract PDF: In recent years, high-entropy alloys (HEAs) have attracted considerable attention in materials engineering due to their unique phase stability and mechanical properties compared to conventional alloys. Since the inception of HEAs, CoCrFeMnNi alloys have been widely investigated due to their outstanding strength and fracture toughness at cryogenic temperatures. However, their lower yield strength at room temperature limits their structural applications. The mechanical properties of HEAs are greatly influenced by their processing methods and microstructural features. Unlike traditional melting techniques, powder metallurgy (PM) provides a unique opportunity to produce HEAs with nanocrystalline structures and uniform compositions. The current review explores recent advances in optimizing the microstructural characteristics in CoCrFeMnNi HEAs by using PM techniques to improve mechanical performance. The most promising strategies include grain refinement, dispersion strengthening, and the development of heterogeneous microstructures (e.g., harmonic, bimodal, and multi-metal lamellar structures). Thermomechanical treatments along with additive manufacturing techniques are also summarized. Additionally, the review addresses current challenges and suggests future research directions for designing advanced HEAs through PM techniques.

Research Articles

[English]
Ultra-Low-Temperature (4.2 K) Tensile Properties and Deformation Mechanism of Stainless Steel 304L Manufactured by Laser Powder Bed Fusion: Seung-Min Jeon, Young-Sang Na, Young-Kyun Kim; J Powder Mater. 2025;32(2):95-103. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2025.00066; Funded: Korea Institute of Materials Science, National Research Foundation of Korea

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Abstract PDF: This study investigated the ultra-low-temperature (4.2 K) tensile properties and deformation mechanisms of stainless steel 304L manufactured via laser powder bed fusion (LPBF). The tensile properties of LPBF 304L were compared to those of conventional 304L to assess its suitability for cryogenic applications. The results revealed that LPBF 304L exhibited a significantly higher yield strength but lower ultimate tensile strength and elongation than conventional 304L at 4.2 K. The temperature dependence of the yield strength also favored LPBF 304L. Microstructural analysis demonstrated that LPBF 304L features a high density of dislocation cells and nano-inclusions, contributing to its greater strength. Furthermore, strain-induced martensitic transformation was observed as a key deformation mechanism at cryogenic temperatures, where austenite transformed into both hexagonal-closed packed (HCP) and body-centered cubic (BCC) martensite. Notably, BCC martensite nucleation occurred within a single HCP band. These findings provide critical insights into the mechanical behavior of LPBF 304L at cryogenic temperatures and its potential for applications in extreme environments.

[Korean]
Effect of Cellulose Fiber Density Variation on Energy Harvesting Performance in a Hydrovoltaic Generator: Seung-Hwan Lee, So Hyun Baek, Hyun-Woo Lee, Yongbum Kwon, Kanghyuk Lee, Kee-Ryung Park, Yoseb Song, Bum Sung Kim, Ji Young Park, Yong-Ho Choa, Da-Woon Jeong; J Powder Mater. 2025;32(2):113-121. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2025.00052; Funded: Korea Institute of Industrial Technology, Development of DLE-type carbon-neutral next-generation lithium-ion concentration technology

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Abstract PDF: Energy harvesting has become a crucial technology for sustainable energy solutions; in particular, the utilization of ambient water movement in hydrovoltaic generators has emerged as a promising approach. However, optimizing performance requires an understanding of structural factors affecting energy harvesting, particularly capillary effects. This study aimed to improve hydrovoltaic generator performance by adjusting internal fiber density, which influences water transport and ion mobility. Using cold isostatic pressing, cellulose acetate (CA) loading in a urethane mold was varied to optimize internal density. As CA loading increased, the fiber arrangement became denser, narrowing capillary pathways and reducing proton mobility. While open-circuit voltage (VOC) remained stable, short-circuit current (ISC) decreased with higher CA mass. The sample with a loading of 0.3 g exhibited the highest energy harvesting efficiency, achieving ISC = 107.2 μA, VOC = 0.15 V, and power (P) = 16.7 μW. This study provides insights into methods of improving hydrovoltaic generator efficiency through internal structural modifications.

[Korean]
Effect of Building Orientation on Tensile Properties of Hastelloy X alloy Manufactured by Laser Powder Bed Fusion: Seong-June Youn, GooWon Noh, Seok Su Sohn, Young-Sang Na, Young-Kyun Kim; J Powder Mater. 2025;32(2):131-137. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2025.00080; Funded: Korea Institute of Materials Science, National Research Foundation of Korea

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Abstract PDF: In this study, the effect of build orientation on the mechanical properties of Hastelloy X fabricated by laser powder bed fusion (LPBF) process was investigated. Initial microstructural analysis revealed an equiaxed grain structure with random crystallographic orientation and annealing twins. Intragranular precipitates identified as Cr-rich M23C6 and Mo-rich M6C carbides were observed, along with a dense dislocation network and localized dislocation accumulation around the carbides. Mechanical testing showed negligible variation in yield strength with respect to build orientation; however, both ultimate tensile strength and elongation exhibited a clear increasing trend with higher build angles. Notably, the specimen built at 90° exhibited approximately 22% higher tensile strength and more than twice the elongation compared to the 0° specimen.

[Korean]
Extraction of MgSO₄ from dolomite and synthesis of Mg(OH)₂ in Bittern: HyunSeung Shim, Jiyeon Kim, Areum Choi, Nuri Oh, YooJin Kim; J Powder Mater. 2025;32(2):122-130. Published online April 30, 2025; DOI: https://doi.org/10.4150/jpm.2025.00073; Funded: Ministry of Trade, Industry and Energy

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Abstract PDF: We synthesized magnesium hydroxide using bittern and dolomite, which are domestic resources. In Bittern, there is a high concentration of Mg2+ ions, but the impurity Ca2+ ion content is also significant, requiring a purification process to remove it. There are two main methods for this purification. Firstly, there is a separation method that utilizes the difference in solubility between Mg2+ ions and Ca2+ ions by using sulfuric acid on dolomite. Adding MgSO4 solution from dolomite to Bittern removes Ca2+ ions as CaSO4. This process simultaneously purifies Ca impurities and increases the Mg/Ca ratio by adding extra Mg2+ ions. In this study, purified bittern was obtained by using dolomite and sulfuric acid to extract MgSO4, which was then used to purify Ca2+ ions. High-purity Mg(OH)2 was synthesized by optimizing the NaOH and NH4OH ratio as an alkaline precipitant.

Critical Review

[English]
Recent Advances in Thermoelectric Materials and Devices: Improving Power Generation Performance: Momanyi Amos Okirigiti, Cheol Min Kim, Hyejeong Choi, Nagamalleswara Rao Alluri, Kwi-Il Park; J Powder Mater. 2025;32(1):1-15. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00395; Funded: National Research Foundation of Korea, National Research Foundation of Korea

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Abstract PDF: Thermoelectric materials have been the focus of extensive research interest in recent years due to their potential in clean power generation from waste heat. Their conversion efficiency is primarily reflected by the dimensionless figure of merit, with higher values indicating better performance. There is a pressing need to discover materials that increase output power and improve performance, from the material level to device fabrication. This review provides a comprehensive analysis of recent advancements, such as Bi2Te3-based nanostructures that reduce thermal conductivity while maintaining electrical conductivity, GeTe-based high entropy alloys that utilize multiple elements for improved thermoelectric properties, porous metal-organic frameworks offering tunable structures, and organic/hybrid films that present low-cost, flexible solutions. Innovations in thermoelectric generator designs, such as asymmetrical geometries, segmented modules, and flexible devices, have further contributed to increased efficiency and output power. Together, these developments are paving the way for more effective thermoelectric technologies in sustainable energy generation.

Research Articles

[English]
Effect of the Cross-rolling Process on the Microstructures and Mechanical Properties of 9Cr-1W ODS Steel: Bu-An Kim, Sanghoon Noh; J Powder Mater. 2025;32(1):37-42. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00332; Funded: Pukyong National University

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Abstract PDF: This study employed a cross-rolling process to fabricate oxide dispersion strengthened (ODS) steel plates and investigated their microstructures and mechanical properties. The 9Cr-1W ODS ferritic steel was fabricated using mechanical alloying and hot isostatic pressing. The hot cross-rolling process produced thick ODS ferritic steel plates with a well-extended rectangular shape. The working direction greatly affected the grain structure and crystal texture of the ODS ferritic steel. Cross-rolled plates showed fine micro-grains with random crystal orientation, while unidirectionally rolled plates exhibited a strong orientation with larger, elongated grains. Transmission electron microscopy revealed a uniform distribution of nano-oxide particles in both rolling methods, with no major differences. Tensile tests of the ODS ferritic steel plates showed that the unidirectional rolled plates had anisotropic elongation, while cross-rolled plates exhibited isotropic behavior with uniform elongation. Cross-rolling produced finer, more uniform grains, reducing anisotropy and improving mechanical properties, making it ideal for manufacturing wide ODS steel components.

[Korean]
Fabrication and Optimization of Al₂O₃ Microchannels Using DLP-Based 3D Printing: Jun-Min Cho, Yong-Jun Seo, Yoon-Soo Han; J Powder Mater. 2025;32(1):59-66. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00346; Funded: Korea Planning & Evaluation of Industrial Technology

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Abstract PDF: This study focused on optimizing the digital light processing (DLP) 3D printing process for high-precision ceramic components using alumina-based slurries. Key challenges, such as cracking during debinding and precision loss due to slurry sedimentation, were addressed by evaluating the exposure time and the nano-to-micro alumina powder ratios. The optimal conditions—exposure time of 15 seconds and a 1:9 mixing ratio—minimized cracking, improved gas flow during debinding, and increased structural precision. Microchannels with diameters above 1.2 mm were successfully fabricated, but channels below 0.8 mm faced challenges due to slurry accumulation and over-curing. These results establish a reliable process for fabricating complex ceramic components with improved precision and structural stability. The findings have significant potential for applications in high-value industries, including aerospace, energy, and healthcare, by providing a foundation for the efficient and accurate production of advanced ceramic structures.

[English]
The Effect of a CNT/MnO₂ Nanoparticle Composite–Based Multi-Shell Typed Electrode for a Fiber Supercapacitor (FSC): Yeonggwon Kim, Hyung Woo Lee; J Powder Mater. 2025;32(1):30-36. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00416; Funded: Pusan National University

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Abstract PDF: Fiber supercapacitors have attracted significant interest as potential textile energy storage devices due to their remarkable flexibility and rapid charge/discharge capabilities. This study describes the fabrication of a composite fiber supercapacitor (FSC) electrode through a multi-shell architecture, featuring layers of carbon nanotube (CNT) conductive shells and MnO₂ nanoparticle active shells. The number of layers was adjusted to assess their impact on FSC energy storage performance. Increasing the number of shells reduced electrode resistance and enhanced pseudocapacitive characteristics. Compared to the MnS@1 electrode, the MnS@5 electrode exhibited a high areal capacitance of 301.2 mF/cm², a 411% increase, but showed a higher charge transfer resistance (RCT) of 701.6 Ω. This is attributed to reduced ion diffusion and charge transfer ability resulting from the thicker multi-shell configuration. These results indicate that fine-tuning the quantity of shells is crucial for achieving an optimal balance between energy storage efficiency and stability.

[Korean]
Optimized Process and Mechanical and Electrical Analysis of Polyimide/Pb(Zr,Ti)O₃-Based Flexible Piezoelectric Composites: Junki Lee, Sang-il Yoon, Hyunseung Kim, Chang Kyu Jeong; J Powder Mater. 2025;32(1):16-22. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00444; Funded: National Research Foundation of Korea, Commercializations Promotion Agency for R&D Outcomes

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Abstract PDF: Piezoelectric composites have attracted significant research interest as sustainable power sources for electronic devices due to their high mechanical stability and electrical output characteristics. This study investigated the optimal processing conditions for fabricating a flexible piezoelectric energy harvester based on Pb(Zr,Ti)O₃ (PZT) powder and a polyimide (PI) matrix composite. Various parameters, including the optimal mixing ratio of PI/PZT, ultrasonic treatment, homogenization, vacuum oven, and UV/O₃ treatment, were optimized to achieve a uniform piezoelectric composite. A PZT content of 30 wt% and 20 minutes of homogenization were identified as the most effective conditions for increasing the uniformity of the composite. The optimized composite exhibited a high piezoelectric coefficient, a typical P-E hysteresis loop, and dielectric properties, exhibiting a voltage output that adjusts in response to variations in the applied touch force. This study provides foundational data for the uniform fabrication of flexible piezoelectric energy harvesters and next-generation miniaturized electronic devices.

[Korean]
3D-Printed Stretchable Electrodes Enabled by a Titanium/Acrylamide-Based Hydrogel Nanocomposite: Se Jin Choi, Han Eol Lee; J Powder Mater. 2025;32(1):67-72. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00465; Funded: National Research Foundation of Korea, National Research Foundation of Korea, Korean Government Ministry of Science ICT, Korea Research Institute of Standards and Science

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Abstract PDF: Wearable electronics have been the focus of considerable interest in various fields, such as human-machine interfaces, soft robotics, and medical treatments, due to their flexibility, stretchability, and light weight. To address the shortcomings of existing metal thin film-based wearable devices, stretchable conductive polymers have been developed. In particular, double networking hydrogels are being actively studied as a polymer with a three-dimensional stereoscopic structure that can be patterned. Nonetheless, they have shortcomings such as poor electrical properties and cumbersome manufacturing processes, making it difficult to apply them in electronic devices. Herein, we report 3D-printed stretchable electrodes enabled by a titanium/polyacrylamide-alginate-based hydrogel nanocomposite. This research suggests the strategy for resolving the challenges of high costs and complex fabrication processes associated with stretchable electrode, providing a solution to accelerate the commercialization of wearable electronic devices.

[Korean]
Effect of Hatch Spacing on the Microstructure and Mechanical Properties of SA508 Gr.3 Steel Fabricated by Laser Powder Bed Fusion: Yuanjiu Huang, Ho Jin Ryu, Kee-Ahn Lee; J Powder Mater. 2025;32(1):50-58. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00479; Funded: Korea Institute for Advancement of Technology, National Research Foundation of Korea

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1 Citations

Abstract PDF

This study investigated the effect of the hatch spacing parameter on the microstructure and mechanical properties of SA508 Gr.3 steel manufactured by laser powder bed fusion (L-PBF) for a nuclear pressure vessel. Materials were prepared with varying hatch spacing (0.04 mm [H4] and 0.06 mm [H6]). The H4 exhibited finer and more uniformly distributed grains, while the H6 showed less porosity and a lower defect fraction. The yield strength of the H4 material was higher than that of the H6 material, but there was a smaller difference between the materials in tensile strength. The measured elongation was 5.65% for the H4 material and 10.41% for the H6 material, showing a significantly higher value for H6. An explanation for this is that although the H4 material had a microstructure of small and uniform grains, it contained larger and more numerous pore defects than the H6 material, facilitating stress concentration and the initiation of microcracks.

Citations

Citations to this article as recorded by

Extremely low temperature mechanical behavior of in-situ oxide containing 304L stainless steel fabricated by laser powder bed fusion
Kwangtae Son, Seung-Min Jeon, Brian K. Paul, Young-Sang Na, Kijoon Lee, Young-Kyun Kim
Journal of Materials Science & Technology.2025; 234: 319. CrossRef

[English]
Comparative Study of Reduced Graphene Oxide Aerogels and Films for Supercapacitor Electrodes: Sunghee Choi, Seulgi Kim, Seojin Woo, Dongju Lee; J Powder Mater. 2025;32(1):23-29. Published online February 28, 2025; DOI: https://doi.org/10.4150/jpm.2024.00472; Funded: Convergence and Open Sharing System

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Abstract PDF: Supercapacitors, renowned for their high power density and rapid charge-discharge rates, are limited by their low energy density. This limitation has prompted the need for advanced electrode materials. The present study investigated reduced graphene oxide (rGO) in two distinct structures, as a film and as an aerogel, for use as supercapacitor electrodes. The rGO film, prepared by vacuum filtration and thermal reduction, exhibited a compact, lamellar structure, while the aerogel, synthesized through hydrothermal treatment, was a highly porous three-dimensional network. Electrochemical analyses demonstrated the aerogel’s superior performance, as shown by a specific capacitance of 121.2 F/g at 5 mV/s, with 94% capacitance retention after 10,000 cycles. These findings emphasize the importance of structural design in optimizing ion accessibility and charge transfer. They also demonstrate the potential of rGO aerogels for increasing the energy storage efficiency of advanced supercapacitor systems.

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