Journal of Powder Materials

Current Status and Prospect of Nanopowder Technology: Jong-Ku Park; J Korean Powder Metall Inst. 2004;11(6):445-450.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.445

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Sliding Wear and Friction Behavior of Electro-Pressure Sintered Co-Fe and Co-Ni Compacts: Yong Kwon, Tai-Woung Kim, Yong-Suk Kim; J Korean Powder Metall Inst. 2004;11(6):451-461.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.451

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Abstract PDF: Dry sliding wear behavior of electro-pressure sintered Co-Fe and Co-Ni compacts was investigated. Pin-on-disk wear tests were performed on the sintered Co-Fe, Co-Ni disks against alumina (Al_2O_3) and silica (SiO_2) balls at various loads ranging from 3N to 12N. A constant sliding speed of 0.1m/sec was employed. Wear rate was calculated by dividing the weight loss of a specimen by the measured specific gravity and sliding dis-tance. Worn surfaces and cross-sections of the specimens were examined using an SEM and EDS to investigate wear mechanism of the compacts. The wear behavior of the compacts were discussed as a function of their com-position. Effects of mechancial properties of the compact as well as oxide layers formed on wearing surface on the wear were also discussed.

Preparation of Bi-materials by Powder Metallurgy Method: In-Gyu Lee, Kwang-Sik Lee, Si-Young Chang; J Korean Powder Metall Inst. 2004;11(6):462-466.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.462

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Abstract PDF: The bi-materials composed of Al-5wt%Mg and its composite reinforced with SiC particles were prepared by ball-milling and subsequent sintering process. The size of powder in Al-Mg/SiCp mixture decreased with increasing ball-milling time, it was saturated above 30 h when the ball and powder was in the ratio of 30 to 1. Both Al-5wt%Mg powders mixture and Al-5wt%Mg/SiCp mixture were compacted under a pressure of 350MPa and were bonded by sintering at temperatures ranging from 873K to 1173K for 1-5h. At 873k, the sound bi-mate-rials could not be obtained. In contrast, the bi-materials with the macroscopically well-bonded interface were obtained at higher temperatures than 873K. The length of well-bonded interface became longer with increasing temperature and time, indicating the improved contact in the interface between unreinforced Al-Mg part and Al-Mg/SiCp composite part. The relative density in the bi-materials increased as the sintering temperature and time increased, and the bi-materials sintered at 1173K for 5h showed the highest density.

Preparation of Nano-sized Indium Tin Oxide (ITO) Powders and Their Sintering Behavior: In-Gyu Lee, Seung-Moo Heo; J Korean Powder Metall Inst. 2004;11(6):467-471.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.467

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Abstract PDF: In order to fabricate a high density sintered body of ITO, nano-sized ITO powders were synthesized by coprecipitation methods. Aqueous solutions of indium and tin salts were mixed and coprecipitated by changing their pH. Coprecipitated ITO powders possessed 20-30 nm crystallite size and a relatively high BET value (35m2/g), however, aggregation of particles were occurred. Therefore, a novel recrystallization technique was applied in order to eliminate the aggregates. The recrystallized ITO material consists of a little bit larger needlelike crystals, 20nmtimes80nm, and it possesses a higher BET value (57m2/g) compared to the plain coprecipitated material (35m2/g). Metastable phase formation and higher content of aggregated particles were observed in the coprecipitated materials. Densification was 95% to 98% complete after 5 hour sintering at 1500°C for the recrystallized powders while densities of the coprecipitated powders were below 75%.

Fabrication of Injection Molded Fe-50%Ni Sintered Bodies: Ki-Hyun Kim, Hyeong-Chul Yoon, Chul-Jin Choi, Byong-Taek Lee; J Korean Powder Metall Inst. 2004;11(6):472-476.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.472

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The Fe-Ni compact bodies were fabricated using Fe-Ni mixed powders with 50 nm in diameter by injection molding process. The relationship between microstructure and material properties was characterized with respect to the volume ratio of powder/binder and sintering temperature with SEM and TEM. In the compact body having the volume percent ratio of 45(Fe-Ni) : 55(binder), which was sintered at 900°C the values of relative density and hardness were low about 97.7% and 277.1 Hv, respectively. Using the composition of 50(Fe Ni) : 50(binder) and sintered at 900°C, the values of relative density and hardness were 98.5%, 294.4 Hv, respec-tively. The grain size of sintered bodies strongly depended on the sintering temperature. In both samples sintered at 600°C and 900°C, the average grain sizes were about 150 nm and 500 nm in diameter, respectively.

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Microstructure and High Temperature Oxidation Behaviors of Fe-Ni Alloys by Spark Plasma Sintering
Chae Hong Lim, Jong Seok Park, Sangsun Yang, Jung-Yeul Yun, Jin Kyu Lee
Journal of Korean Powder Metallurgy Institute.2017; 24(1): 53. CrossRef

Synthesis of Flake Ag Powder by Polyol Process: Dong-Jin Kim, Huanzhen Liang, Jong-Gwan Ahn, Jae-Ryeong Lee, Hun-Saeng Chung; J Korean Powder Metall Inst. 2004;11(6):477-485.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.477

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Abstract PDF: Monodispersed flaky silver powder was obtained by controlling the ratios of H_2O_2/NH_3 and Agin in a mixed solution of ethylene glycol and ammonia with an addition of PVP. The effects of NH_3/Ag,; H_2O_2/Ag;and;H_2PtCl_6/Ag on its morphology and size were investigated. In H_2O_2-NH_3-AgNO_3;system,;NH_3/Ag molar ratio was found to be an important reaction factor for the nucleation and crystal growth of Ag powder. The synthesis of flaky powder was optimized at over 6 of NH_3/Ag ;and;5;of;H_2O_2/Ag;under;1.0times10-3;of;Pt/Ag.;Moreover,;as;the; NH_3/Ag molar ratio increased, the size of precipitates was increased regardless of the amount of Pt. In the absence of H_2PtCI, the morphology and size of reduced Ag powder were found to be irregular in shape 2-4µm in diameter. However, homogenized fine Ag powder was obtained due to heterogeneous nucleation when H_2PtCI used as a cat-alyst, and flaky one was synthesized with the addition of Pt over 1.0times10-3 of Pt/Ag.

Crystallization and Magnetic Properties of Non-Equilibrium Al(Fe-Cu) Alloy Powders Produced by Rod Milling and Chemical Leaching: Hyun-Goo Kim; J Korean Powder Metall Inst. 2004;11(6):486-492.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.486

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Abstract PDF: We report the crystallization and magnetic properties of non-equilibrium Al_0.6(Fe_xCu_1-x)_0.4(x=0.25, 0.50, 0.75) alloy powders produced by rod-milling as well as by new chemical leaching. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h or 500 h milling, only the broad peaks of nano bcc crystalline phases were detected in the XRD patterns. The crystallite size, the peak and the crystallization temperatures increased with increasing Fe. After being annealed at 600circC for 1 h for as-milled alloy powders, the peaks of bcc AlCu_4;and;Al_13Cu_4Fe_3;for;x=0.25,;bcc;AlCu_4;and;Al_5Fe_2;for;x=0.50,;and;Al_5Fe_2,;and;Al_0.5Fe_0.5;for;x=0.75 are observed. After being annealed at 500circ;and;600circCfor 1 h for leached specimens, these non-equi-librium phases transformed into fcc Cu and CuFe_2O_4phases for the x=0.25 specimen, and into bcc alpha-Fe,;fcc;Cu,;and;CuFe_2O_4 phases for both the x=0.50 and the x=0.75 specimens. The saturation magnetization decreased with increasing milling time for Al_0.6(Fe_xCu_1-x)_0.4 alloy powders. On cooling the leached specimens from 800~850°C,;the magnetization first sharply increase at about 491.4°C,;745°C,;and;750.0°C for x=0.25, x=0.50, and x=0.75 specimens, repectively.

Effect of Reaction Factors on the Fabrication of Nano-Sized Indium Oxide Powder by Spray Pyrolysis Process: Jae-Keun Yu; J Korean Powder Metall Inst. 2004;11(6):493-502.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.493

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In this study, nano-sized indium oxide powder with the average particle size below 100 nm is fab-ricated from the indium chloride solution by the spray pyrolysis process. The effects of the reaction temperature, the concentration of raw material solution and the inlet speed of solution on the properties of powder were studied. As the reaction temperature increased from 850 to 1000°C, the average particle size of produced powder increased from 30 to 100 nm, and microstructure became more solid, the particle size distribution was more irregular, the intensity of a XRD peak increased and specific surface area decreased. As the indium concentration of the raw material solution increased from 40 to 350 g/l, the average particle size of the powder gradually increased from 20 to 60 nm, yet the particle size distribution appeared more irregular, the intensity of a XRD peak increased and spe-cific surface area decreased. As the inlet speed of solution increased from 2 to 5 cc/min., the average particle size of the powder decreased and the particle size distribution became more homogeneous. In case of the inlet speed of 10 cc/min, the average particle size was larger and the particle size distribution was much irregular compared with the inlet speed of 5 cc/min. As the inlet speed of solution was 50 cc/min, the average particle size was smaller and microstructure of the powder was less solid compared with the inlet speed of 10 cc/min. The intensity of a XRD peak and the variation of specific area of the powder had the same tendency with the variation of the average par-ticle size.

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Sintering densification of ITO targets with low tin oxide content for depositing TCO films as electrodes of solar cells
Tan Wang, Jiwen Xu, Guisheng Zhu, Fei Shang, Huarui Xu
Ceramics International.2024; 50(3): 5532. CrossRef

Dispersion Properties and Photocatalytic Activities of TiO₂ Powders Obtained by Homogeneous Precipitation Process at Low Temperature in a Acrylic Resin: S. Woo, W. Kim, C. Rhee; J Korean Powder Metall Inst. 2004;11(6):503-509.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.503

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Abstract PDF: Dispersion stabilities and photocatalytic activities of rutile TiO_2 powders with unique nano-structure synthesized by homogeneous precipitation process at low temperature(HPPLT) have been investigated in the acrylic resin containing fluorostyrene in the range of 0~0.16 mole. Isoelectric point of TiO_2 in the acrylic resin placed in the neutral region whereas that of TiO_2 in the water placed in the acidic region, indicating that zeta potential and agglomeration of TiO_2 powder is strongly dependent on the pH and the type of solvent. To prepare an adhesion, an acrylic resin containing fluorostyrene was synthesized by a radical polymerization. The adhesion of coating layer was increased with increasing fluorostyrene's contents without changing the dispersion stabilities and degrading photocatalytic properties.

Characterization of Fe Nanocapsules synthesized by Plasma Arc Discharge Process: Woo-Young Park, Cheol-Su Youn, Ji-Hun Yu, Young-Woo Oh, Chul-Jin Choi; J Korean Powder Metall Inst. 2004;11(6):510-514.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.510

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Abstract PDF: Iron-carbon nanocapsules were synthesized by plasma arc discharge (PAD) process under various atmosphere of methane, argon and hydrogen gas. Characterization and surface properties were investigated by means of HRTEM, XRD, XPS and Mossbauer spectroscopy. Fe nanocapsules synthesized were composed of three phases (alpha-Fe,;Y-Fe;and;Fe_3C) with core/shell structures. The surface of nanocapsules was covered by the shell of graphite phase in the thickness of 4~5nm.

Synthesis and Microstructure of Fe(C) Nanocapsules by Chemical Vapor Condensation: Jung-Han Lee, Sung-Duk Kim, Jin-Chun Kim, Chul-Jin Choi, Chan-Gyu Lee; J Korean Powder Metall Inst. 2004;11(6):515-521.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.515

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Abstract PDF: Fe(C) nanocapsules were prepared by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl (Fe(CO)_5). Their characterizations were studied by means of X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy. The long-chained Fe(C) nanocapsules hav-ing the mean size of under 70 nm could be obtained below 1100°C in different gas flow rates. The particle size of the powders was increased with increasing decomposition temperature, but it was decreased with increasing CO gas flow rate. The Fe powders produced at 500°C consisted of three layers of alpha-Fe/Fe_3C/amorphous phases, but it had two phase core-shell structure which consited of Fe_3C phase of core and graphite of shell at 1100°C.

Preparation of FeAl nanopowders by Plasma Arc Discharge Process: Woo-Young Park, Cheol-Su Youn, Ji-Hun Yu, Young-Woo Oh, Chul-Jin Choi; J Korean Powder Metall Inst. 2004;11(6):522-527.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.522

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Abstract PDF: Nano sized FeAl intermetallic particles were successfully synthesized by plasma arc discharge pro-cess. The synthesized powders shouted core-shell structures with the particle size of 10-20 nm. The core was metallic FeAl and shell was composed of amorphous AI_2O_3;and;a;little;amount;of;metallic;Fe_3O_4. Because of the difference of Fe and Al vapor pressure during synthesis, the Al contents in the nanoparticles depended on the Al contents of master alloy.

Microstructure and Sintering Behavior of Injection Molded Fe Sintered Body Using Rapid Thermal Heating Process: Ki-Hyun Kim, Jae-Kil Han, Ji-Hun Yu, Chul-Jin Choi, Byong-Taek Lee; J Korean Powder Metall Inst. 2004;11(6):528-534.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.528

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Abstract PDF: Using the nano Fe powders having 50 nm in diameter, Fe compact bodies were fabricated by injec-tion molding process. The relationship between microstructure and material properties depending on the volume ratio of powder/binder and sintering temperature were characterized by SEM, TEM techniques. In the compact body with the volume percentage ratio of 45(Fe powder) : 55(binder), which was sintered at 700°C, the relative density was about 97%, and the values of volume shrinkage and hardness were about 66.3% and 242.0 Hv, respec-tively. Using the composition of 50(Fe powder) : 50(binder) and sintered at 700°C, the values of relative density, volume shrinkage and hardness of Fe sintered bodies were 73.3%,;47.6% and 152.8 Hv, respectively. They showed brittle fracture mode due to the porous and fine microstructure.

휴대폰용 기구 부품의 기술 동향: J Korean Powder Metall Inst. 2004;11(6):534-536.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.534

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