Journal of Powder Materials

Volume 17(5); October 2010

Improvement of the Magnetic Properties of (Nd, Dy)-Fe-B Sintered Magnets by Modification of HD and Annealing Processes: S. NamKung, Y.H. Lee, M.K. Kim, T.S. Jang; J Korean Powder Metall Inst. 2010;17(5):359-364.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.359

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In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at 400°C increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive 2nd and 3rd step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

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Magnetic Properties of (Nd, Dy)-Fe-B Sintered Magnets Mixed with Dy Compounds
S. NamKung, M.W. Lee, I.S. Cho, Y.D. Park, T.H. Lim, S.R. Lee, T.S. Jang
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 29. CrossRef
Effect of Cu Content on Microstructural and Magnetic Properties of a Nd-Fe-B Strip Cast
Song-E Park, Tae-Hoon Kim, Seong-Rae Lee, Dong-Hwan Kim, Seok NamKung, Tae-Suk Jang
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 24. CrossRef

Effect of Sintering Temperature on Microstructure and Mechanical Properties for the Spark Plasma Sintered Titanium from CP-Ti Powders: Kyeong-Sik Cho, In-Beom Song, Min-Hyeok Jang, Ji-Hye Yoon, Myung-Hoon Oh, Jae-Keun Hong, Nho-Kwang Park; J Korean Powder Metall Inst. 2010;17(5):365-372.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.365

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The evolution of sinterability, microstructure and mechanical properties for the spark plasma sintered(SPS) Ti from commercial pure titanium(CP-Ti) was studied. The densification of titanium with 200 mesh and 400 mesh pass powder was achieved by SPS at 750sim1100°C under 10 MPa pressure and the flowing H_2+Ar mixed gas atmosphere. The microstructure of Ti sintered up to 800°C consisted of equiaxed grains. In contrast, the growth of large elongated grains was shown in sintered bodies at 900°C with the 400 mesh pass powder and the lamella grains microstructure had been developed by increasing sintering temperature. The Vickers hardness of 240~270 HV and biaxial strength of 320~340 MPa were found for the specimen prepared at 950°C.

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Sintering pressure effect on the performances of near-zero thermal expansion xLFCS/Cu metal matrix composites
Chang Zhou, Hong Zhong, Hao Lu, Xuelu Pang, Congfa Zhang, Haowu Wang, Qiang Cong, Yuzhu Song, Naike Shi, Jiong Zhao, Xiangxu Meng, Jun Chen
Ceramics International.2023; 49(17): 27958. CrossRef
Spark plasma sintered Al-0.5 wt% MWCNT nanocomposite: Effect of sintering pressure on the densification behavior and multi-scale mechanical properties
Lavish K. Singh, Alok Bhadauria, Akash Oraon, Tapas Laha
Diamond and Related Materials.2019; 91: 144. CrossRef
Manufacturing and Properties of CGI-based Composite Coating Layer Utilizing a Warm Spray Process and Cu-Ga and Cu-In Mixed Powders
Min-Gwang Jeon, Myeong-Ju Lee, Hyeong-Jun Kim, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2014; 21(3): 229. CrossRef
Effect of particle size distribution on microstructure and mechanical properties of spark-plasma-sintered titanium from CP-Ti powders
Je Ha Shon, In-Beom Song, Kyeong-Sik Cho, Yong-il Park, Jae-Keun Hong, Nho-Kwang Park, Myung-Hoon Oh
International Journal of Precision Engineering and Manufacturing.2014; 15(4): 643. CrossRef
Effects of various sintering methods on microstructure and mechanical properties of CP-Ti powder consolidations
Je-ha SHON, Jong-moon PARK, Kyeong-sik CHO, Jae-keun HONG, Nho-kwang PARK, Myung-hoon OH
Transactions of Nonferrous Metals Society of China.2014; 24: s59. CrossRef
Sintering and Rolling Behavior of Cu-50In-13Ga Ternary Alloy Powder for Sputtering Target
Dae-Won Kim, Yong-Ho Kim, Jung-Han Kim, Dae-Guen Kim, Jong-Hyeon Lee, Kwang-Bo Choi, Hyeon-Taek Son
Journal of Korean Powder Metallurgy Institute.2012; 19(4): 264. CrossRef
Effect of Heat Treatment Environment on the Properties of Cold Sprayed Cu-15 at.%Ga Coating Material for Sputtering Target
Byung-Chul Choi, Dong-Yong Park, Hyung-Jun Kim, Ik-Hyun Oh, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2011; 18(6): 552. CrossRef

Mechanical Properties and Fabrication of TiAl Alloy by Pulsed Current Activated Sintering: Song-Lee Du, Na-Ri Kim, Won-Baek Kim, Sung-Wook Cho, In-Jin Shon; J Korean Powder Metall Inst. 2010;17(5):373-378.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.373

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Abstract PDF: Nanostuctured TiAl powder was synthesized by high energy ball milling. A dense nanostuctured TiAl was consolidated using pulsed current activated sintering method within 2 minutes from mechanically synthesized powders of TiAl and horizontally milled powders of Ti+Al. The grain size and hardness of TiAl sintered from horizontally milled Ti+Al powders and high energy ball milled TiAl powder were 35 nm, 20 nm and 450 kg/mm2, 630 kg/mm2, respectively.

Size Control of Bismuth Nanoparticles by Changes in Carrier-Gas Flow Rate and Chamber Pressure of Gas Condensation Apparatus: Gyoung-Ja Lee, Chang-Kyu Kim, Min-Ku Lee, Chang-Kyu Rhee; J Korean Powder Metall Inst. 2010;17(5):379-384.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.379

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Abstract PDF: In the present work, bismuth nanopowders with various particle size distributions were synthesized by controlling argon (Ar) gas flow rate and chamber pressure of a gas condensation (GC) apparatus. From the analyses of transmission electron microscopy (TEM) images and nitrogen gas adsorption results, it was found that as Ar gas flow rate increased, the specific surface area of bismuth increased and the average particles size decreased. On the other hand, as the chamber pressure increased, the specific surface area of bismuth decreased and the average particles size increased. The optimum gas flow rate and chamber pressure for the maximized electrochemical active surface area were determined to be 8 L/min and 50 torr, respectively. The bismuth nanopowders synthesized at the above condition exhibit 13.47 m2g-1 of specific surface area and 45.6 nm of average particles diameter.

Hydrogenation Behavior of Sponge Titanium: Ji-Hwan Park, Dong-Won Lee, Jong-Ryoul Kim; J Korean Powder Metall Inst. 2010;17(5):385-389.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.385

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Titanium powders have been usually produced by de-hydrogenating treatment in vacuum with titanium hydride (TiH_2) powders prepared by milling of hydrogenated sponge titanium, TiH_x. The higher stoichiometry of x in TiH_x, whose maximum value is 2, is achieved, crushing behavior is easier. TiH_x powder can be, therefore, easy to manufactured leading to obtain higher recovery factor of it. In addition, contamination of the powder can also minimized by the decrease of milling time. In this study, the hydrogenation behavior of sponge titanium was studied to find the maximum stoichiometry. The maximum stoichiometry in hydride formation of sponge titanium could be obtained at 750°C for 2 hrs leading to the formation of TiH_sim1.99 and the treating temperatures lower or higher than 750°C caused the poor stoichiometries by the low hydrogen diffusivity and un-stability of TiH_x, respectively. Such experimental behavior was compared with thermodynamically calculated one. The hydrogenated TiH_1.99 sponge was fully ball-milled under -325 Mesh and the purity of pure titanium powders obtained by de-hydrogenation was about 99.6%.

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Study on Manufacture of High Purity TiCl₄ and Synthesis of High Purity Ti Powders
Jieun Lee, Jin-Ho Yoon, Chan Gi Lee
Journal of Korean Powder Metallurgy Institute.2019; 26(4): 282. CrossRef
Effect of Heat Treatment Temperature and Atmosphere on the Microstructure of TiH2-WO3 Powder Mixtures
Han-Eol Lee, Yeon Su Kim, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2017; 24(1): 41. CrossRef
Titanizing on the surface of iron metal foam
Su-In Lee, Jung-Yeul Yun, Tae-Soo Lim, Byoung-Kee Kim, Young-Min Kong, Jei-Pil Wang, Dong-Won Lee
Thermochimica Acta.2014; 581: 87. CrossRef
Study on synthesis of Zr–Ti alloy powder using molten magnesium
D.-W. Lee, Y.-K. Baek, W.-J. Lee, J.-P. Wang
Materials Research Innovations.2013; 17(sup2): s113. CrossRef
Direct synthesis of zirconium powder by magnesium reduction
Dong-Won Lee, Jung-Yeul Yun, Sung-Won Yoon, Jei-Pil Wang
Metals and Materials International.2013; 19(3): 527. CrossRef
Synthesis of Zr-Ti Alloy Powder by Magnesium Reduction
Dong-Won Lee, Geun-Tae Park, Tae-Soo Lim, Hye-Moon Lee, Ji-Hun Yu
Journal of Korean Powder Metallurgy Institute.2011; 18(4): 359. CrossRef

Synthesis of Gold Nanoparticles by Chemical Reduction Method for Direct Ink Writing: Young-Sang Cho, Soo-Jung Son, Young-Kuk Kim, Kook-Chae Chung, Chul-Jin Choi; J Korean Powder Metall Inst. 2010;17(5):390-398.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.390

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Aqueous gold nanoparticle dispersion was synthesized by chemical reduction method using diethanolamine as reducing agent and polyethyleneimine as dispersion stabilizer. The synthesis conditions for the stable dispersion of the gold nanoparticle suspension were determined by changing the amount of the reducing agent and dispersant during the wet chemical synthesis procedures. The face centered cubic lattice structure of the gold nanoparticles was confirmed by using X-ray diffraction and the morphologies of the nanoparticles were observed by transmission electron microscope. The synthesized gold nanoparticle dispersion was concentrated by evaporating the dispersion medium at room temperature followed by the addition of ethyleneglycol as humectant for the increase of the elastic properties to obtain gold nanoparticle inks for direct ink writing process. The line patterns were obtained with the gold nanoparticle inks during the writing procedures and the morphologies of the fine patterns were observed by scanning electron microscope.

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Fabrication Of Colloidal Clusters Decorated With Dye Molecules For Potential Application As Photonic Molecules
Y.-S. Cho
Archives of Metallurgy and Materials.2015; 60(2): 1221. CrossRef
Synthesis of Nickel and Copper Nanopowders by Plasma Arc Evaporation
Young-Sang Cho, Jong Woo Moon, Kook Chae Chung, Jung-Goo Lee
Journal of Korean Powder Metallurgy Institute.2013; 20(6): 411. CrossRef
Low Temperature Debinding Process Using Oxygen Plasma for Flexible Printed Electronics
Young-In Lee
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 343. CrossRef
Fabrication of Fecralloy Foil Coated by Fecralloy Nanoparticles Using Electrospray Processing
Jung-Yeul Yun, Sang-Sun Yang, Hye-Young Koo, Hye-Moon Lee
Journal of Korean Powder Metallurgy Institute.2011; 18(6): 526. CrossRef

MnO₂ as an Effective Sintering Aid for Enhancing Piezoelectric Properties of (K,Na)NbO₃ Ceramics: Seong-Kyu Jeong, In-Ki Hong, Nam-Binh Do, Vu Diem Ngoc Tran, Seong-Youl Cho, Weon Pil Taib, Jae-Shin Lee; J Korean Powder Metall Inst. 2010;17(5):399-403.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.399

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The effects of MnO_2 doping on the crystal structure, ferroelectric, and piezoelectric properties of (K,Na)NbO_3 (KNN) ceramics have been investigated. MnO_2 was found to be effective in enhancing the densification and grain growth during sintering. X-ray diffraction analysis indicated that Mn ions substituted B-site Nb ions up to 2 mol%, however, further doping induced unwanted secondary phases. In comparison with undoped KNN ceramics, the well developed microstructure and the substitution to B-sites in 2 mol% Mn-doped KNN ceramics resulted in significant improvements in both piezoelectric coupling coefficient and electromechanical quality factor.

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Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3‐Modified (Li,K,Na)(Nb,Ta)O3 Lead‐Free Piezoceramics
Qing Liu, Fang‐Yuan Zhu, Lei Zhao, Ke Wang, Longtu Li, Jing‐Feng Li, W. Jo
Journal of the American Ceramic Society.2016; 99(11): 3670. CrossRef

Enhancement in Piezoelectric Properties of PZT-Based Ceramics by High Energy Ball-Milling Treatment of Solid-State Synthesized Powders: Dae-Uk Kim, Han-Bok Lee, Nguyen Viet Hung, Ky Nam Pham, Hyoung-Su Han, Jae-Shin Lee; J Korean Powder Metall Inst. 2010;17(5):404-408.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.404

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Abstract PDF: The effects of high energy ball-milling (HEBM) on the sintering behavior and piezoelectric properties of 0.1 wt% Li_2CO_3 doped 0.8Pb(Mg_1/3Nb_2/3)O_3-0.2Pb(Zr_0.475Ti_0.525)O_3 (PMN-PZT) ceramics were investigated. It was found that HEBM treatment was quite effective to reduce the average particle size down to 300 nm, leading to increased density as well as enhanced piezoelectric properties of a sintered specimen even though prolonged HEBM resulted in unwanted secondary phases that caused a degradation of piezoelectric properties. The dielectric constant (varepsilon_r), piezoelectric coupling factor (k_p) and piezoelectric constant d_33 of 0.1 wt% Li_2CO_3 doped PMN-PZT ceramics prepared via HEBM for 10 h reached 2040, 0.68 and 554 pC/N, respectively.

Characterization of TiO₂ Synthesized in Acidic Conditions at Low Temperature by Sol-gel Method: Thanh Binh Nguyen, Moon-Jin Hwang, Seon-Sam Lee, Dong-Eon Choe, Kwang-Sun Ryu; J Korean Powder Metall Inst. 2010;17(5):409-414.; DOI: https://doi.org/10.4150/KPMI.2010.17.5.409

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Titanium dioxide (TiO_2), which is one of the most basic materials in our daily life, plays a key role for environment purification. We synthesized TiO_2 nanoparticles by the hydrolysis reactions of titanium tetraisopropoxide using HNO_3 as a peptizing agent or CH_3COOH as a chelating agent in the sol-gel method. The powder consisted of a rod shape or a spherical shape according to the concentration and kind of acid. The physical properties of TiO_2 nanoparticles were investigated with X-ray diffraction, SEM, BET analysis, and UV-Vis spectrophotometer.

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Mesoporous Tud-C Supported Tungsten Oxide-Doped Titania Photocatalysts for Cyclohexane Photooxidation
Siew Ling Lee, Chui Min Ling, Leny Yuliati
SSRN Electronic Journal .2022;[Epub] CrossRef
Effect of TiO2−x nanoparticle defect structure on hydroxyl radical scavenging activity under X-ray irradiation
V.V. Seminko, I.I. Bespalova, P.O. Maksimchuk, K.O. Hubenko, O.D. Opolonin, S.L. Yefimova
Colloids and Surfaces A: Physicochemical and Engineering Aspects.2022; 651: 129734. CrossRef
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Imad Eddine Aouissi, Sheela Chandren, Norazah Basar, Wan Nazihah Wan Ibrahim
Bulletin of Chemical Reaction Engineering & Catalysis.2022; 17(4): 683. CrossRef

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