Journal of Powder Materials

The Present Issues of Rare Earth Magnetic Powder for Bonded Magnets: Dong-Hwan Kim, Ji-Hun Yu; J Korean Powder Metall Inst. 2010;17(2):81-87.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.081

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Preparation of Highly Efficient Nd-Fe-B Magnetic Powders by Reduction/Diffusion Process
Dongsoo Kim, Chunqiang Chen, Younkyoung Baek, Chuljin Choi
Journal of Korean Powder Metallurgy Institute.2013; 20(3): 197. CrossRef

Recycling Technology for End-of-Life LCD Units: Hi-Min Lee, Hyun-Seon Hong, Hang-Chul Jung, Hong-Yoon Kang, Soon-Jik Hong; J Korean Powder Metall Inst. 2010;17(2):88-100.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.088

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The Effect of Milling Conditions for Dissolution Efficiency of Valuable Metals from PDP Waste Panels
Hyo-Seob Kim, Chan-Mi Kim, Chul-Hee Lee, Sung-Kyu Lee, Hyun-Seon Hong, Jar-Myung Koo, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2013; 20(2): 107. CrossRef
Characteristics of Indium Dissolution of Waste LCD Panel Powders Fabricated by High Energy Ball Milling (HEBM) Process with Milling Time
Hyo-Seob Kim, Jun-Je Sung, Cheol-Hee Lee, Hyun-Seon Hong, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2011; 18(4): 378. CrossRef

Research on Synthesis and Sintering Behavior of Nano-sized (Pb, La)TiO₃ Powders Using Mechano Chemical Process: Young-In Lee, Yong-Sung Goo, Jong-Sik Lee, Yong-Ho Choa; J Korean Powder Metall Inst. 2010;17(2):101-106.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.101

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Abstract PDF: In this study, we successfully synthesized a nano-sized lanthanum-modified lead-titanate (PLT) powder with a perovskite structure using a high-energy mechanochemical process (MCP). In addition, the sintering behavior of synthesized PLT nanopowder was investigated and the sintering temperature that can make the full dense PLT specimen decreased to below 1050°C by using Bi_2O_3 powder as sintering agent. The pure PLT phase of perovskite structure was formed after MCP was conducted for 4 h and the average size of the particles was approximately 20 nm. After sintered at 1050 and 1150°C, the relative density of PLT was about 93.84 and 95.78%, respectively. The density of PLT increased with adding Bi_2O_3 and the specimen with the relative densitiy over 96% were fabricated below 1050°C when 2 wt% of Bi_2O_3 was added.

Fabrication and Thermoelectric Properties of Carbon Nanotube/Bi₂Te₃ Composites: Kyung-Tae Kim, Kyeong-Mi Jang, Kyong-Ju Kim, Gook-Hyun Ha; J Korean Powder Metall Inst. 2010;17(2):107-112.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.107

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Abstract PDF: Carbon-nanotube-embedded bismuth telluride (CNT/Bi_2Te_3) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with Bi_2Te_3 alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/Bi_2Te_3 composites by spark plasma sintering process at 350°C for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the Bi_2Te_3 matrix. Seebeck coefficient of CNT/Bi_2Te_3 composites reveals that the composite has n-type semiconducting characteristics with values ranging -55;µV/K to -95;µV/K with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.

Effects of the Sintering Variable on Impact Energy in MA 316L ODS and Wet 316L ODS Stainless Steels: Sung-Soo Kim, Chang-Hee Han, Jin-Sung Jang; J Korean Powder Metall Inst. 2010;17(2):113-122.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.113

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Abstract PDF: Two kinds of oxide-dispersion-strengthened (ODS) 316L stainless steel were manufactured using a wet mixing process(wet) and a mechanical alloying method (MA). An MA 316L ODS was prepared by a mixing of metal powder and a mechanical alloying process. A wet 316L ODS was manufactured by a wet mixing with 316L stainless steel powder. A solution of yttrium nitrate was dried after being in the wet 316L ODS alloy. The results showed that carbon and oxygen were effectively reduced during the degassing process before the hydroisostatic process (HIP) in both alloys. It appeared that the effect of HIP treatment on increase in impact energy was pronounced in the MA 316L ODS alloy. The MA 316L ODS alloy showed a higher yield strength and a smaller elongation, when compared to the wet 316L ODS alloy. This seemed to be attributed to the enhancement of bonding between oxide and matrix particles from HIP and to the presence of a finer oxide of about 20 nm from the MA process in the MA 316L ODS alloy.

The Characteristic of Titanium Composites Including of Nano-sized TiN_x for Stack Separator: Sung-Bum Park, Tae-Ho Ban, Heung-Sik Woo, Sung-Jin Kim; J Korean Powder Metall Inst. 2010;17(2):123-129.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.123

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The fabrication of interconnect from titanium powders and TiN_x powders is investigated. Corrosion-resistant titanium and TiN_x are used as reinforcement in order to reveal high heat and corrosion resistance at the elevated temperature. We fabricated the plates for interconnect reinforced with TiN_x by mixing titanium powders with 10 wt.% of nano-sized TiN_x. Spark Plasma Sintering (SPS) was chosen for the sintering of these composites. The plate made of titanium powders and TiN_x powders demonstrates higher corrosion resistance than that of the plate of titanium powders alone. The physical properties of specimens were analyzed by performing hardness test and biaxial strength test. The electrochemical properties, such as corrosion resistance and hydrogen permeability at high temperature, were also investigated. The microstructures of the specimens were investigated by FESEM and profiles of chemical compositions were analyzed by EDX.

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Mechanical properties of stainless steel composites with titanium carbonitride consolidated by spark plasma sintering
Bunyod Allabergenov, Oybek Tursunkulov, Amir Abidov, Soon-Wook Jeong, Sungjin Kim
Journal of Composite Materials.2016; 50(12): 1567. CrossRef

Effect of Process Parameters on Microstructure and Magnetic Properties of Sm-Co Alloy Powder Prepared by High Energy Ball Milling: Bo-Sik Kim, Si-Young Chang; J Korean Powder Metall Inst. 2010;17(2):130-135.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.130

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Abstract PDF: Sm-16.7wt%Co alloy powders were prepared by high energy ball milling under the conditions of various milling time and the content of process control agent (PCA), and their microstructure and magnetic properties were investigated to establish optimum processing conditions. The initial powders employed showed irregular shape and had a size ranging from 5 to 110;µm. After milling for 5 h, the shape of powders changed to round shape and their mean powder size was approximately 5;µm, which consisted of the agglomerated nano-sized particles with 15 nm in diameter. The coercivity was reduced with increasing the milling time, whereas the saturation magnetization increased. As the content of PCA increased, the powder size minutely decreased to approximately 7;µm at the PCA content of 10 wt%. The XRD patterns showed that the main diffraction peaks disappeared apparently after milling, indicating the formation of amorphous structure. The measured values of coercivity were almost unchanged with increasing the content of PCA.

Effect of Hydrogen Reduction Treatment on Room-Temperature Thermoelectric Performance of p-type Thermoelectric Powders: Kyung-Tae Kim, Kyeong-Mi Jang, Gook-Hyun Ha; J Korean Powder Metall Inst. 2010;17(2):136-141.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.136

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Bismuth-telluride based (Bi_0.2Sb_0.8)_2Te_3 thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging 400;nm;sim;2;µm. The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at 350°C for 10 min at the heating rate of 100°C/min and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity (0.8;mOmegacdotcm) than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.

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Influence of Metal-Coating Layer on an Electrical Resistivity of Thick-Film-Type Thermoelectric Modules Fabricated by a Screen Printing Process
Kyung-Tae Kim, Hye-Young Koo, Gook-Hyun Ha
Journal of Korean Powder Metallurgy Institute.2011; 18(5): 423. CrossRef

Preparation of Ultrafine C/N Controled TiC_xN_y Powders by Magnesium Reduction: Dong-Won Lee, Byoung-Kee Kim, Jung-Yeul Yun, Ji-Hoon Yu, Yong-Jin Kim; J Korean Powder Metall Inst. 2010;17(2):142-147.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.142

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The ultrafine titanium carbonitride (TiC_xN_y) particles below 100 nm in mean size, including various carbon and nitrogen contents (x=0.55~0.9, y=0.1~0.5), were successfully synthesized by new Mg-thermal reduction process. Nanostructured sub-stoichiometric titanium carbide (TiC_x) particles were initially produced by the magnesium reduction of gaseous TiCl_4+x/2C_2Cl_4 at 890°C and post heat treatments in vacuum were performed for 2 hrs to remove residual magnesium and magnesium chloride mixed with TiC_x. Finally, well C/N-controled TiC_xN_y phases were successfully produced by nitrification heat treatment under normal N_2 gas atmosphere at 1150°C for 2 hrs. The values of purity, mean particle size and oxygen content of produced particles were about 99.3%, 100 nm and 0.2 wt.%, respectively.

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Characteristics of Stainless Steel Composites with Nano-sized TiCxNy
Tae-Ho Ban, Sung-Bum Park, Soo-Jeong Jo, Dong-Won Lee, Farkhod R. Turaev, Yong-Il Park, Sung-Jin Kim
Journal of Korean Powder Metallurgy Institute.2011; 18(3): 290. CrossRef

Phase Evolution and Thermo-physical Properties of Rare-earth Oxides for Thermal Barrier Systems: Byung-Chul Shim, Kil-Ho Kwak, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, Byung-Koog Jang, Seong-Won Kim; J Korean Powder Metall Inst. 2010;17(2):148-153.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.148

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Thermal barrier systems have been widely investigated over the past decades, in order to enhance reliability and efficiency of gas turbines at higher temperatures. Yttria-stabilized zirconia (YSZ) is one of the most leading materials as the thermal barriers due to its low thermal conductivity, thermodynamic stability, and thermal compatibility with metal substrates. In this work, rare-earth oxides with pyrochlore phases for thermal barrier systems were investigated. Pyrochlore phases were successfully formed via solid-state reactions started from rare-earth oxide powders. For the heat-treated samples, thermo-physical properties were examined. These rare-oxide oxides showed thermal expansion of 9sim12times10-6/K and thermal conductivity of 1.2~2.4 W/mK, which is comparable with the thermal properties of YSZ.

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Phase Evolution and Thermal Conductivities of (La1-xGdx)2Zr2O7Oxides for Thermal Barrier Coatings
Chang-Sup Kwon, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, Byung-Koog Jang, Seong Won Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(6): 429. CrossRef
Phase Evolution and Thermo-physical Properties of La2(Zr1-xHfx)2O7Oxides for Thermal Barrier Coatings
Seong-Won Kim, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, Byung-Koog Jang
Journal of Korean Powder Metallurgy Institute.2011; 18(6): 568. CrossRef

Sintering Behavior and Phase Analysis of (Nd, Dy)-Fe-B Powder: Se-Hoon Kim, Jin-Woo Kim, Young-Do Kim; J Korean Powder Metall Inst. 2010;17(2):154-159.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.154

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In this study, the sintering behavior of (Nd, Dy)-Fe-B powder which fabricated by strip-casting was investigated with various sintering temperatures and holding times. The relative density over 99% could be obtained by both sintering at 1070°C for 1h and sintering at 970°C for 20h. The grain growth was observed in sintered specimen at 1050°C compared to one at 970°C. The isothermal sintering process below 1000°C led to suppress grain growth showing the improved magnetic properties. The phase transformation of Nd-rich was confirmed by X-ray diffraction pattern.

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Crystallographic and Mössbauer studies of sintered Nd-Fe-B magnet
Yong Hui Li, Jung Tae Lim, Chul Sung Kim, Sung Yong An, Kang Ryong Choi, Moonhee Choi
Journal of the Korean Physical Society.2013; 62(11): 1641. CrossRef
Mechanical properties of (Nd,Dy)–Fe–B magnets sintered via cyclic sintering
Jin Woo Kim, Se Hoon Kim, Young Do Kim
Materials Science and Engineering: A.2012; 535: 325. CrossRef
Magnetic Properties and Sintering Behavior of (Nd,Dy)-Fe-B Permanent Magnet by Spark Plasma Sintering
Sun-Yong Song, Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(2): 105. CrossRef
Pt and Polymer Electrolyte Membrane Fuel Cell
Hye-Sook Joo, Jung-Yeul Yun, Han-Shin Choi
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 1. CrossRef
High coercive Nd–Fe–B magnets fabricated via two-step sintering
Se Hoon Kim, Jin Woo Kim, Tae Sun Jo, Young Do Kim
Journal of Magnetism and Magnetic Materials.2011; 323(22): 2851. CrossRef
The Coercivity Enhancement of (Nd,Dy)-Fe-B Sintered Magnet by Microstructure Control
Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 18. CrossRef

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