Iron oxide (Fe₂O₃) nanoclusters exhibit significant potential in the biomedical and pharmaceutical fields due to their strong magnetic properties, stability in solutions, and compatibility with living systems. They excel in magnetic separation processes, displaying high responsiveness to external magnetic fields. In contrast to conventional Fe₂O₃ nanoparticles that can aggregate in aqueous solutions due to their ferrimagnetic properties, these nanoclusters, composed of multiple nanoparticles, maintain their magnetic traits even when scaled to hundreds of nanometers. In this study, we develop a simple method using solvothermal synthesis to precisely control the size of nanoclusters. By adjusting precursor materials and reducing agents, we successfully control the particle sizes within the range of 90 to 420 nm. Our study not only enhances the understanding of nanocluster creation but also offers ways to improve their properties for applications such as magnetic separation. This is supported by our experimental results highlighting their size-dependent magnetic response in water. This study has the potential to advance both the knowledge and practical utilization of Fe₂O₃ nanoclusters in various applications.

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• Enzymatic properties of iron oxide nanoclusters and their application as a colorimetric glucose detection probe
  Dahyun Bae, Minhee Kim, Jin-sil Choi
  RSC Advances.2025; 15(6): 4573.     CrossRef

This review summarizes the recent progress in iron-oxide-based heat generators. Cancer treatment using magnetic nanoparticles as a heat generator, termed magnetic fluid hyperthermia, is a promising noninvasive approach that has gained significant interest. Most previous studies on improving the hyperthermia effect have focused on the construction of dopant-containing iron oxides. However, their applications in a clinical application can be limited due to extra dopants, and pure iron oxide is the only inorganic material approved by the Food and Drug Administration (FDA). Several factors that influence the heat generation capability of iron-oxide-based nanoparticles are summarized by reviewing recent studies on hyperthermia agents. Thus, our paper will provide the guideline for developing pure iron oxide-based heat generators with high heat dissipation capabilities.

Iron and copper are practically immiscible in the equilibrium state, even though their atomic radii are similar. As non-equilibrium solid solutions, the metastable Fe-Cu alloys can be synthesized using special methods, such as rapid quenching, vapor deposition, sputtering, ion-beam mixing, and mechanical alloying. The complexity of these methods (multiple steps, low productivity, high cost, and non-eco-friendliness) is a hinderance for their industrial applications. Electrical explosion of wire (EEW) is a well-known and effective method for the synthesis of metallic and alloy nanoparticles, and fabrication using the EEW is a simple and economic process. Therefore, it can be potentially employed to circumvent this problem. In this work, we propose the synthesis of Fe-Cu nanoparticles using EEW in a suitable solution. The powder shape, size distribution, and alloying state are analyzed and discussed according to the conditions of the EEW.

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• Identification of the reconstruction induced high-entropy spinel oxide nanosheets for boosting alkaline water oxygen evolution
  Xuexue Wang, Runqing Lu, Shanhe Gong, Shaokang Yang, Wenbo Wang, Zhongti Sun, Xiaozhen Zhang, Jun Liu, Xiaomeng Lv
  Chemical Engineering Journal.2025; 503: 158488.     CrossRef
• Trends in bimetallic nanomaterials and methods for the removal of p-nitrophenol and its derivatives from wastewater
  M. S. Qatan, F. Arshad, M. Miskam, G. A. Naikoo
  International Journal of Environmental Science and Technology.2024; 21(5): 5247.     CrossRef
• Control of cluster coalescence during formation of bimetallic nanoparticles and nanoalloys obtained via electric explosion of two wires
  K.V. Suliz, A.Yu. Kolosov, V.S. Myasnichenko, N.I. Nepsha, N.Yu. Sdobnyakov, A.V. Pervikov
  Advanced Powder Technology.2022; 33(3): 103518.     CrossRef

Metal matrix composites (MMCs), which are a combination of two or more constituents with different physical or chemical properties, are today receiving great attention in various areas, as they have high specific strength, corrosion resistance, fatigue strength, and good tribological properties. This paper presents a research review on the combination of matrix and reinforced materials, fabrication processes, and application status of metal matrix composites. In this paper, we aim to discuss and review the importance of metal composite materials as advanced materials that can be used in various applications such as transportation, defense, sports, and extreme environments. In addition, the applicability and technology development trends in new process technology fields such as additive manufacturing of metal composites will be described.

Iron oxides currently attract considerable attention due to their potential applications in the fields of lithiumion batteries, bio-medical sensors, and hyperthermia therapy materials. Magnetite (Fe₃O₄) is a particularly interesting research target due to its low cost, good biocompatibility, outstanding stability in physiological conditions. Hydrothermal synthesis is one of several liquid-phase synthesis methods with water or an aqueous solution under high pressure and high temperature. This paper reports the growth of magnetic Fe₃O₄ particles from iron powder (spherical, <10 μm) through an alkaline hydrothermal process under the following conditions: (1) Different KOH molar concentrations and (2) different synthesis time for each KOH molar concentrations. The optimal condition for the synthesis of Fe₃O₄ using Fe powders is hydrothermal oxidation with 6.25 M KOH for 48 h, resulting in 89.2 emu/g of saturation magnetization at room temperature. The structure and morphologies of the synthesized particles are characterized by X-ray diffraction (XRD, 2θ = 20°–80°) with Cu-kα radiation and field emission scanning electron microscopy (FE-SEM), respectively. The magnetic properties of magnetite samples are investigated using a vibrating sample magnetometer (VSM). The role of KOH in the formation of magnetite octahedron is observed.

Rare earth magnets are the strongest type of permanent magnets and are integral to the high tech industry, particularly in clean energies, such as electric vehicle motors and wind turbine generators. However, the cost of rare earth materials and the imbalance in supply and demand still remain big problems to solve for permanent magnet related industries. Thus, a magnet with abundant elements and moderate magnetic performance is required to replace rare-earth magnets. Recently, a”-Fe₁₆N₂ has attracted considerable attention as a promising candidate for next-generation non-rare-earth permanent magnets due to its gigantic magnetization (3.23 T). Also, metastable a”-Fe₁₆N₂ exhibits high tetragonality (c/a = 1.1) by interstitial introduction of N atoms, leading to a high magnetocrystalline anisotropy constant (K₁ = 1.0MJ/m³). In addition, Fe has a large amount of reserves on the Earth compared to other magnetic materials, leading to low cost of raw materials and manufacturing for industrial production. In this paper, we review the synthetic methods of metastable a”-Fe₁₆N₂ with film, powder and bulk form and discuss the approaches to enhance magnetocrystalline anisotropy of a”-Fe₁₆N₂. Future research prospects are also offered with patent trends observed thus far.

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• Failure Cases according to Photocuring-Based Alumina 3D Printing
  So-Young Ko, Shin-Il Go, Kyoung-Jun Jang, Sang-Jin Lee
  Korean Journal of Materials Research.2024; 34(10): 457.     CrossRef

Conductive and dielectric SiC are fabricated using electroless plating of Ni–Fe films on SiC chopped fibers to obtain lightweight and high-strength microwave absorbers. The electroless plating of Ni–Fe films is achieved using a two-step process of surface sensitizing and metal plating. The complex permeability and permittivity are measured for the composite specimens with the metalized SiC chopped fibers dispersed in a silicone rubber matrix. The original noncoated SiC fibers exhibit considerable dielectric losses. The complex permeability spectrum does not change significantly with the Ni–Fe coating. Moreover, dielectric constant is sensitively increased with Ni–Fe coating, owing to the increase of the space charge polarization. The improvements in absorption capability (lower reflection loss and small matching thickness) are evident with Ni–Fe coating on SiC fibers. For the composite SiC fibers coated with Ni–Fe thin films, a -35 dB reflection loss is predicted at 7.6 GHz with a matching thickness of 4 mm.

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• Magnetic sputtering of FeNi/C bilayer film on SiC fibers for effective microwave absorption in the low-frequency region
  Tong Guo, Ben Huang, Changgeng Li, Yumin Lou, Xiu-Zhi Tang, Xiaozhong Huang, Jianling Yue
  Ceramics International.2021; 47(4): 5221.     CrossRef

Cu-Fe alloys (CFAs) are much anticipated for use in electrical contacts, magnetic recorders, and sensors. The low cost of Fe has inspired the investigation of these alloys as possible replacements for high-cost Cu-Nb and Cu-Ag alloys. Here, alloys of Cu and Fe having compositions of Cu_100-xFe_x (x = 10, 30, and 50 wt.%) are prepared by gas atomization and characterized microstructurally and structurally based on composition and powder size with scanning electron microscopy (SEM) and X-ray diffraction (XRD). Grain sizes and Fe-rich particle sizes are measured and relationships among composition, powder size, and grain size are established. Same-sized powders of different compositions yield different microstructures, as do differently sized powders of equal composition. No atomic-level alloying is observed in the CFAs under the experimental conditions.

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of 1300°C or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. Yb₂O₃ and SiO₂ are used as the raw starting materials to form ytterbium disilicate (Yb₂Si₂O₇). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., SiO₂, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

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• Fabrication, Microstructure and Adhesive Properties of BCuP-5 Filler Metal/Ag Plate Composite by using Plasma Spray Process
  Seong-June Youn, Young-Kyun Kim, Jae-Sung Park, Joo-Hyun Park, Kee-Ahn Lee
  Journal of Korean Powder Metallurgy Institute.2020; 27(4): 333.     CrossRef

In this study, Fe-Cu-C alloy is sintered by spark plasma sintering (SPS). The sintering conditions are 60 MPa pressure with heating rates of 30, 60 and 9°C/min to determine the influence of heating rate on the mechanical and microstructure properties of the sintered alloys. The microstructure and mechanical properties of the sintered Fe-Cu-C alloy is investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The temperature of shrinkage displacement is changed at 450°C with heating rates 30, 60, and 90°C/min. The temperature of the shrinkage displacement is finished at 650°C when heating rate 30°C/min, at 700°C when heating rate 60oC/min and at 800°C when heating rate 90oC/min. For the sintered alloy at heating rates of 30, 60, and 90oC/min, the apparent porosity is calculated to be 3.7%, 5.2%, and 7.7%, respectively. The hardness of the sintered alloys is investigated using Rockwell hardness measurements. The objective of this study is to investigate the densification behavior, porosity, and mechanical properties of the sintered Fe-Cu-C alloys depending on the heating rate.

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• Effect of Milling Time and Addition of PCA on Austenite Stability of Fe-7%Mn Alloy
  Seung-Jin Oh, In-Jin Shon, Seok-Jae Lee
  Journal of Korean Powder Metallurgy Institute.2018; 25(2): 126.     CrossRef

A sintered body of TiB₂-reinforced iron matrix composite (Fe-TiB₂) is fabricated by pressureless-sintering of a mixture of titanium hydride (TiH₂) and iron boride (FeB) powders. The powder mixture is prepared in a planetary ball-mill at 700 rpm for 3 h and then pressurelessly sintered at 1300, 1350 and 1400°C for 0-2 h. The optimal sintering temperature for high densities (above 95% relative density) is between 1350 and 1400°C, where the holding time can be varied from 0.25 to 2 h. A maximum relative density of 96.0% is obtained from the (FeB+TiH₂) powder compacts sintered at 1400°C for 2 h. Sintered compacts have two main phases of Fe and TiB₂ along with traces of TiB, which seems to be formed through the reaction of TiB₂ formed at lower temperatures during the heating stage with the excess Ti that is intentionally added to complete the reaction for TiB₂ formation. Nearly fully densified sintered compacts show a homogeneous microstructure composed of fine TiB₂ particulates with submicron sizes and an Fe-matrix. A maximum hardness of 71.2 HRC is obtained from the specimen sintered at 1400°C for 0.5 h, which is nearly equivalent to the HRC of conventional WC-Co hardmetals containing 20 wt% Co.

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• Optimizing the Microstructure and Properties of Fe–Ni–Cu–Mo–C Sintered Steel by TiB2
  Zenglin Liu, Yankang Wang, Weilong Lu, Feng Liu, Wei Han, Wuqiang He
  Science of Advanced Materials.2024; 16(6): 707.     CrossRef
• Effect of Ce Addition on the As-Cast and As-Forged Microstructure of Fe-TiB2 Composites
  Lin Zhang, Jianwen Gao, Minghao Huang, Engang Wang
  JOM.2019; 71(11): 4144.     CrossRef
• Microstructure, mechanical, and tribological properties of pressureless sintered and spark plasma sintered Fe TiB2 nanocomposites
  Hak-Rae Cho, Ji-Soon Kim, Koo-Hyun Chung
  Tribology International.2019; 131: 83.     CrossRef

Carbon nanofiber (CNF) composites coated with spindle-shaped Fe₂O₃ nanoparticles (NPs) are fabricated by a combination of an electrospinning method and a hydrothermal method, and their morphological, structural, and chemical properties are measured by field-emission scanning electron microscopy, transmission electron microscopy, Xray diffraction, and X-ray photoelectron spectroscopy. For comparison, CNFs and spindle-shaped Fe₂O₃ NPs are prepared by either an electrospinning method or a hydrothermal method, respectively. Dye-sensitized solar cells (DSSCs) fabricated with the composites exhibit enhanced open circuit voltage (0.70 V), short-circuit current density (12.82 mA/cm2), fill factor (61.30%), and power conversion efficiency (5.52%) compared to those of the CNFs (0.66 V, 11.61 mA/cm2, 51.96%, and 3.97%) and spindle-shaped Fe₂O₃ NPs (0.67 V, 11.45 mA/cm2, 50.17%, and 3.86%). This performance improvement can be attributed to a synergistic effect of a superb catalytic reaction of spindle-shaped Fe₂O₃ NPs and efficient charge transfer relative to the one-dimensional nanostructure of the CNFs. Therefore, spindle-shaped Fe₂O₃-NPcoated CNF composites may be proposed as a potential alternative material for low-cost counter electrodes in DSSCs.

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• Ni Nanoparticles-Graphitic Carbon Nanofiber Composites for Pt-Free Counter Electrode in Dye-Sensitized Solar Cells
  Dong-Hyeun Oh, Bon-Ryul Koo, Yu-Jin Lee, HyeLan An, Hyo-Jin Ahn
  Korean Journal of Materials Research.2016; 26(11): 649.     CrossRef

With the stabilization of Korea’s industrialization, it has become interested in the efficient use of rare metals, climate change and industrial environment and safety etc. It is thus making efforts to implement economic policies that address such issues. Therefore it is necessary to understand the demand, supply and use of metal materials. Since 2010, the Korean government has developed the integrated material flow methodology and has been trying to examine the demand, supply and use of metal materials. In 2013, the Korean government surveyed the material flow of chromium. Material flow analysis and environment emission of chromium were investigated 8 steps; (1) raw material, (2) first process, (3) Intermediate product, (4) End product, (5) Use/accumulation, (6) Collection, (7) Recycling, (8) Disposal. Chromium was used for stainless steel, alloy steel, coated sheets, refractory material and coating materials. Recycling was done mainly in use of stainless steel scrap. To ensure efficient use of chromium, process improvement is required to reduce the scrap in the intermediate product stage. In the process of producing of the products using chromium, it was confirmed that chromium was exposed to the environment. It requires more attention and protection against environment emission of chromium.

In this study, the reduction kinetics and behaviors of oxides in the water-atomized iron powder have been evaluated as a function of temperature ranging 850-1000°C in hydrogen environment, and compared to the reduction behaviors of individual iron oxides including Fe₂O₃, Fe₃O₄ and FeO. The water-atomized iron powder contained a significant amount of iron oxides, mainly Fe₃O₄ and FeO, which were formed as a partially-continuous surface layer and an inner inclusion. During hydrogen reduction, a significant weight loss in the iron powder occurred in the initial stage of 10 min by the reduction of surface oxides, and then further reduction underwent slowly with increasing time. A higher temperature in the hydrogen reduction promoted a high purity of iron powder, but no significant change in the reduction occurred above 950°C. Sequence reduction process by an alternating environment of hydrogen and inert gases effectively removed the oxide scale in the iron powder, which lowered reduction temperature and/or shortened reduction time.

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• Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder
  B. Ali, S.H. Choi, S.J. Seo, D.Y. Maeng, C.G. Lee, T.S. Kim, K.T. Park
  Archives of Metallurgy and Materials.2017; 62(2): 1119.     CrossRef