Journal of Powder Materials

[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

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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.

[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

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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]
Development of Highly Transparent and Thermo-Shielding Flexible Film via Colloidal ITO Nanocrystals: Hyoin Bae, Hyeyeon Jung, Juna Lee, Dahye Shin, Sungyeon Heo; J Powder Mater. 2024;31(6):508-512. Published online December 31, 2024; DOI: https://doi.org/10.4150/jpm.2024.00423

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Abstract PDF: Infrared radiation accounts for approximately 50% of the solar spectrum. Specifically, the near-infrared (NIR) spectrum, ranging from 760 nm to 2500 nm, is primarily responsible for solar heat gain, increasing indoor temperatures and reducing heating and cooling efficiency. To address this issue, we developed a highly transparent thermo-shielding flexible film that maintains a high transmittance of the visible region (T = 80%) while reducing the transmittance of the NIR region (T ≈ 0%). NIR-absorbing indium tin oxide (ITO) nanocrystals were coated onto polyethylene terephthalate (PET) films, and both films were sandwiched to improve the NIR absorption properties and protect the nanocrystal film layer. The fabricated films were applied to a model house and decreased the indoor temperature by approximately 8°C. Our study demonstrates that energy consumption can be reduced by ITO nanocrystal-coated flexible films, with potential implications for the smart window and mobility markets.

[English]
Epsilon Iron Oxide (ε-Fe₂O₃) as an Electromagnetic Functional Material: Properties, Synthesis, and Applications: Ji Hyeong Jeong, Hwan Hee Kim, Jung-Goo Lee, Youn-Kyoung Baek; J Powder Mater. 2024;31(6):465-479. Published online December 31, 2024; DOI: https://doi.org/10.4150/jpm.2024.00290

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Abstract PDF: Iron oxide (ε-Fe₂O₃) is emerging as a promising electromagnetic material due to its unique magnetic and electronic properties. This review focuses on the intrinsic properties of ε-Fe₂O₃, particularly its high coercivity, comparable to that of rare-earth magnets, which is attributed to its significant magnetic anisotropy. These properties render it highly suitable for applications in millimeter wave absorption and high-density magnetic storage media. Furthermore, its semiconducting behavior offers potential applications in photocatalytic hydrogen production. The review also explores various synthesis methods for fabricating ε-Fe₂O₃ as nanoparticles or thin films, emphasizing the optimization of purity and stability. By exploring and harnessing the properties of ε-Fe₂O₃, this study aims to contribute to the advancement of next-generation electromagnetic materials with potential applications in 6G wireless telecommunications, spintronics, high-density data storage, and energy technologies.

[English]
Recovery of Barium, Nickel, and Titanium Powders from Waste MLCC: Haein Shin, Kun-Jae Lee; J Powder Mater. 2024;31(5):374-381. Published online October 31, 2024; DOI: https://doi.org/10.4150/jpm.2024.00192

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Abstract PDF: The development of the electronics industry has led to an increased demand for the manufacture of MLCC (Multilayer Ceramic Capacitors), which in turn is expected to result in a rise in MLCC waste. The MLCC contains various metals, notably barium, titanium, and nickel, whose disposal is anticipated to increase correspondingly. Recently, recycling technologies for electronic waste have garnered attention as they address waste management and raw material supply challenges. This paper investigates the recovery of barium, nickel, and titanium from the MLCC by a hydrometallurgical process. Using citric acid, which is an organic acid, the metal inside the MLCC was leached. Additionally, metal materials were recovered through precipitation and complexing processes. As a result, barium and titanium were recovered from the leachate of the waste MLCC, and 93% of the nickel-based powder was recovered. Furthermore, the optimal recovery process conditions for recycling these metal elements were investigated.

[Korean]
Characterization of Compacted and Pressureless Sintered Parts for Molybdenum Oxide Powder according to Hydrogen Reduction Temperature: Jong Hoon Lee, Kun-Jae Lee; J Powder Mater. 2024;31(4):336-341. Published online August 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00241

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Abstract PDF: Molybdenum, valued for its high melting point and exceptional physical and chemical properties, is studied in diverse fields such as electronics, petrochemicals, and aviation. Among molybdenum oxides, molybdenum dioxide stands out for its higher electrical conductivity than other transition metal oxides due to its structural characteristics, exhibiting metallic properties. It is applied as pellets to gas sensors, semiconductors, and secondary batteries for its properties. Thus, research on molybdenum dioxide compaction and pressureless sintering is necessary, yet research on pressureless sintering is currently insufficient. This study synthesized MoO₃ powder via solution combustion synthesis and reduced it using the 3% hydrogen/argon gas mixture to investigate the effect of reduction temperature on the powder. Additionally, the reduced powder was compacted and subjected to pressureless sintering with temperature as a variable. The density and the microstructure of brown parts were analyzed and discussed.

[English]
A Review of Inorganic Solid Electrolytes for All-Solid-State Lithium Batteries: Challenges and Progress: Seul Ki Choi, Jaehun Han, Gi Jeong Kim, Yeon Hee Kim, Jaewon Choi, MinHo Yang; J Powder Mater. 2024;31(4):293-301. Published online August 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00206

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Abstract PDF: All-solid-state lithium batteries (ASSLBs) are receiving attention as a prospective next-generation secondary battery technology that can reduce the risk of commercial lithium-ion batteries by replacing flammable organic liquid electrolytes with non-flammable solid electrolytes. The practical application of ASSLBs requires developing robust solid electrolytes that possess ionic conductivity at room temperature on a par with that of organic liquids. These solid electrolytes must also be thermally and chemically stable, as well as compatible with electrode materials. Inorganic solid electrolytes, including oxide and sulfide-based compounds, are being studied as promising future candidates for ASSLBs due to their higher ionic conductivity and thermal stability than polymer electrolytes. Here, we present the challenges currently facing the development of oxide and sulfide-based solid electrolytes, as well as the research efforts underway aiming to resolve these challenges.

[Korean]
TiO₂ Thin Film Coating on an Nb-Si–Based Superalloy via Atomic Layer Deposition: Ji Young Park, Su Min Eun, Jongmin Byun, Byung Joon Choi; J Powder Mater. 2024;31(3):255-262. Published online June 27, 2024; DOI: https://doi.org/10.4150/jpm.2024.00052

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Abstract PDF: Nano-oxide dispersion–strengthened (ODS) superalloys have attracted attention because of their outstanding mechanical reinforcement mechanism. Dispersed oxides increase the material’s strength by preventing grain growth and recrystallization, as well as increasing creep resistance. In this research, atomic layer deposition (ALD) was applied to synthesize an ODS alloy. It is useful to coat conformal thin films even on complex matrix shapes, such as nanorods or powders. We coated an Nb-Si–based superalloy with TiO2 thin film by using rotary-reactor type thermal ALD. TiO2 was grown by controlling the deposition recipe, reactor temperature, N2 flow rate, and rotor speed. We could confirm the formation of uniform TiO2 film on the surface of the superalloy. This process was successfully applied to the synthesis of an ODS alloy, which could be a new field of ALD applications.

[Korean]
Hydrogen Reduction Behavior of NCM-based Lithium-ion Battery Cathode Materials: So-Yeong Lee, So-Yeon Lee, Dae-Hyeon Lee, Ho-Sang Sohn; J Powder Mater. 2024;31(2):163-168. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00017

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Abstract PDF: As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 °C and hydrogen partial pressure above 0.5 atm, Ni and Li2O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H2O, and Li2CO3, with about 0.02 wt% Al as an impurity.

[Korean]
Inorganic Compound and Cycloserine Composite Particles for Improved Stability: Dongwon Kim, Heeseo Kim, Hongjun Yoon, Hyuk Jun Cho, Sung Giu Jin; J Powder Mater. 2024;31(2):126-131. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00002

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Abstract PDF: The aim of this study was to improve the chemical stability of cycloserine containing organic and inorganic compounds. Composite particles were manufactured with a 1:1 weight ratio of organic/inorganic compounds and cycloserine. The influence of organic/inorganic compounds on the stability of cycloserine was investigated under accelerated stress conditions at 60°C/75% RH for 24 hours. In addition, the properties of the composite particles were evaluated using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and the dissolution of the drug was assessed by preparing it as a hard capsule. Among the organic and inorganic compounds investigated, calcium hydroxide most improved the stability of cycloserine under accelerated stress conditions (53.3 ± 2.2% vs 1.7 ± 0.2%). DSC results confirmed the compatibility between calcium hydroxide and the cycloserine, and SEM results confirmed that it was evenly distributed around the cycloserine. Calcium hydroxide also showed more than 90% cycloserine dissolution within 15 minutes. Therefore, the calcium hydroxide and cycloserine composite particles may be candidates for cycloserine oral pharmaceuticals with enhanced drug stability.

[Korean]
Fabrication of Bi₂Te_2.5Se_0.5 by Combining Oxide-reduction and Compressive-forming Process and Its Thermoelectric Properties: Young Soo Lim, Gil-Geun Lee; J Powder Mater. 2024;31(1):50-56. Published online February 28, 2024; DOI: https://doi.org/10.4150/KPMI.2024.31.1.50

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[Korean]
Fabrication of Nanowire by Electrospinning Process Using Nickel Oxide Particle Recovered from MLCC: Haein Shin, Jongwon Bae, Minsu Kang, Kun-Jae Lee; J Powder Mater. 2023;30(6):502-508. Published online December 1, 2023; DOI: https://doi.org/10.4150/KPMI.2023.30.6.502

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Abstract PDF: With the increasing demand for electronic products, the amount of multilayer ceramic capacitor (MLCC) waste has also increased. Recycling technology has recently gained attention because it can simultaneously address raw material supply and waste disposal issues. However, research on recovering valuable metals from MLCCs and converting the recovered metals into high-value-added materials remains insufficient. Herein, we describe an electrospinning (E-spinning) process to recover nickel from MLCCs and modulate the morphology of the recovered nickel oxide particles. The nickel oxalate powder was recovered using organic acid leaching and precipitation. Nickel oxide nanoparticles were prepared via heat treatment and ultrasonic milling. A mixture of nickel oxide particles and polyvinylpyrrolidone (PVP) was used as the E-spinning solution. A PVP/NiO nanowire composite was fabricated via Espinning, and a nickel oxide nanowire with a network structure was manufactured through calcination. The nanowire diameters and morphologies are discussed based on the nickel oxide content in the E-spinning solution.

[Korean]
Evaluation of Microstructures and Mechanical Properties of Ni-Y₂O₃ Sintered Alloys Based on the Powder Preparation Methods: Gun-Woo Jung, Ji-Ho Cha, Min-Seo Jang, Minsuk Oh, Jeshin Park; J Powder Mater. 2023;30(6):484-492. Published online December 1, 2023; DOI: https://doi.org/10.4150/KPMI.2023.30.6.484

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Abstract PDF: In this study, Ni-Y₂O₃ powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y₂O₃ powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y₂O₃ crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y₂O₃ nanoparticles, and the MA powder formed small Y₂O₃ crystals on the surface of large Ni particles by milling the mixture of Ni and Y₂O₃. The average grain size of Y₂O₃ in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y₂O₃ particles and Ni grains.

[Korean]
Phase Formation and Mechanical Property of YSZ‒30 vol.% WC Composite Ceramics Fabricated by Hot Pressing: Jin-Kwon Kim, Jae-Hyeong Choi, Nahm Sahn, Sung-Soo Ryu, Seongwon Kim; J Powder Mater. 2023;30(5):409-414. Published online October 1, 2023; DOI: https://doi.org/10.4150/KPMI.2023.30.5.409

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Abstract PDF: YSZ (Y₂O₃-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

[Korean]
Controlling Particle Size of Recycled Copper Oxide Powder for Copper Thermite Welding Characteristics: Hansung Lee, Minsu Kim, Byungmin Ahn; J Powder Mater. 2023;30(4):332-338. Published online August 1, 2023; DOI: https://doi.org/10.4150/KPMI.2023.30.4.332

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Abstract PDF

Thermite welding is an exceptional process that does not require additional energy supplies, resulting in welded joints that exhibit mechanical properties and conductivity equivalent to those of the parent materials. The global adoption of thermite welding is growing across various industries. However, in Korea, limited research is being conducted on the core technology of thermite welding. Currently, domestic production of thermite powder in Korea involves recycling copper oxide (CuO). Unfortunately, controlling the particle size of waste CuO poses challenges, leading to the unwanted formation of pores and cracks during thermite welding. In this study, we investigate the influence of powder particle size on thermite welding in the production of Cu-thermite powder using waste CuO. We conduct the ball milling process for 0.5–24 h using recycled CuO. The evolution of the powder shape and size is analyzed using particle size analysis and scanning electron microscopy (SEM). Furthermore, we examine the thermal reaction characteristics through differential scanning calorimetry. Additionally, the microstructures of the welded samples are observed using optical microscopy and SEM to evaluate the impact of powder particle size on weldability. Lastly, hardness measurements are performed to assess the strengths of the welded materials.

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Friction Welding of Casted SCM440 and Sintered F-05-140 Dissimilar Steels and Their Joint Properties under Various Welding Conditions
Jisung Lee, Hansung Lee, Eunhyo Song, Byungmin Ahn
Journal of Powder Materials.2024; 31(5): 414. CrossRef

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