Journal of Powder Materials

Review on Thermoset-carbon Nanotube Nanocomposites: Minh Ton-that; J Korean Powder Metall Inst. 2005;12(2):89-105.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.089

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Effect of Post-heat Treatment on Fatigue Strength of Thermally-Sprayed Stellite Alloy on Steel: Jeong Oh, Jun Komotori, Chang Rhee; J Korean Powder Metall Inst. 2005;12(2):106-111.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.106

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Abstract PDF: The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on 0.35% carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.

Carbothermal Reduction of Oxide Powder Prepared from Waste WC/Co Hardmetal by Solid Carbon: Gil-Geun Lee, Gook-Hyun Ha; J Korean Powder Metall Inst. 2005;12(2):112-116.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.112

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In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste WC-8 wt.%Co hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste WC-8wt.%Co hardmetal has a mixture of WO_3 and CoWO_4. This oxide powder reduced at about 850°C, formed tungsten carbides at about 950°C, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about 1100°C by solid carbon under a stream of argon. The WC/Co composite powder synthesized at 1000°C for 6 hours from oxide powder of waste WC-8wt.%Co hardmetal has an average particle size of 0.3 µm.

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Effects of mechanical milling on the carbothermal reduction of oxide of WC/Co hardmetal scrap
Gil-Geun Lee, Gook-Hyun Ha
Metals and Materials International.2016; 22(2): 260. CrossRef
Recovery of Tungsten from WC/Co Hardmetal Sludge by Alkaline Leaching Hydrometallurgy Process
Gil-Geun Lee, Ji-Eun Kwon
Journal of Korean Powder Metallurgy Institute.2016; 23(5): 372. CrossRef
Recovery of tungsten carbide from hard material sludge by oxidation and carbothermal reduction process
Woo-Gwang Jung
Journal of Industrial and Engineering Chemistry.2014; 20(4): 2384. CrossRef
Trend on the Recycling Technologies for the used Tungsten Carbide(WC) by the Patent and Paper Analysis
Jin-Ki Jeong, Jae-Chun Lee, Sang-Woo Park, Kyung-Seok Kang
Journal of the Korean Institute of Resources Recycling.2012; 21(1): 82. CrossRef

Nano-structured Carbon Support for Pt/C Anode Catalyst in Direct Methanol Fuel Cell: Jae-Sik Choi, Heock-Hoi Kwon, Won Chung, Ho-In Lee; J Korean Powder Metall Inst. 2005;12(2):117-121.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.117

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Platinum catalysts for the DMFC (Direct Methanol Fuel Cell) were impregnated on several carbon supports and their catalytic activities were evaluated with cyclic voltammograms of methanol electro-oxidation. To increase the activities of the Pt/C catalyst, carbon supports with high electric conductivity such as mesoporous carbon, carbon nanofiber, and carbon nanotube were employed. The Pt/e-CNF (etched carbon nanofiber) catalyst showed higher maximum current density of 70 mA cm-2 and lower on-set voltage of 0.54 V vs. NHE than the Pt/Vulcan XC-72 in methanol oxidation. Although the carbon named by CNT (carbon nanotube) series turned out to have larger BET surface area than the carbon named by CNF (carbon nanofiber) series, the Pt catalysts supported on the CNT series were less active than those on the CNF series due to their lower electric conductivity and lower availability of pores for Pt loading. Considering that the BET surface area and electric conductivity of the e-CNF were similar to those of the Vulcan XC-72, smaller Pt particle size of the Pt/e-CNF catalyst and stronger metal-support interaction were believed to be the main reason for its higher catalytic activity.

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Excellent Durability of Substoichiometric Titanium Oxide As a Catalyst Support for Pd in Alkaline Direct Ethanol Fuel Cells
Son Truong Nguyen, Jong-Min Lee, Yanhui Yang, Xin Wang
Industrial & Engineering Chemistry Research.2012; 51(30): 9966. CrossRef
Nano-structured Pt–Cr anode catalyst over carbon support, for direct methanol fuel cell
Jae-Sik Choi, Won Seob Chung, Heung Yong Ha, Tae-Hoon Lim, In-Hwan Oh, Seong-Ahn Hong, Ho-In Lee
Journal of Power Sources.2006; 156(2): 466. CrossRef

Synthesis of Nano-Clay and The Application for Nanocomposite: Soon-Yong Jeong, Eon-Il Jeong; J Korean Powder Metall Inst. 2005;12(2):122-130.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.122

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Layered silicate was synthesized at hydrothermal condition from silica adding to various materials. Nano-clay was synthesized by intercaltion of various amine compounds into synthetic layered silicate. The products were analysed by XRD, SEM, and FT-IR in order to examine the condition of synthesis and intercalation. From the results, it was confirmed that kaolinite was synthesized from precipitated silica and gibbsite at 220°C during 10 days, and hetorite was synthesized from silica sol at 100°C during 48 h. Na-Magadiite was synthesized from silica gel at 150°C during 72 h, and Na-kenyaite was synthesized from silica gel at 160°C during 84 h. Nano-clay was prepared using synthetic layered silicate intercalated with various amine compounds. Kenyaite was easily intercalated by various organic compounds, and has the highest basal-spacing value among other layered silicates. Basal-spacing was changed according to the length of alkyl chain of amine comopounds. Polymer can be easily intercalated by dispersion with large space of interlayer. Finally, epoxy/nano-clay nanocomposite can be easily prepared.

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A study on the effect of halloysite nanoparticle addition on the strength of glass fiber reinforced plastic
Yun-Hae Kim, Soo-Jeong Park, Jin-Woo Lee, Kyung-Man Moon
Modern Physics Letters B.2015; 29(06n07): 1540003. CrossRef

Sintering Behavior of 7xxx Series Al Blended Powder with Variation of Heating Rate: Shin Kang, Kyung Min, Hyun Park, Si-Young Chang, Young Kim; J Korean Powder Metall Inst. 2005;12(2):131-135.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.131

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7xxx series Al alloy has the most attractive properties including its excellent high specific strength, stress corrosion cracking and corrosion-resistance. However, in case of the Al-Zn system, the liquid phase has a transient aspect because of the high solid solubility of Zn in Al. Therefore, transient liquid phase sintering behavior was observed during the sintering process. And the amount of liquid and its duration were influenced by the process variables including heating rate and final sintering temperature. At high heating rates(100°C/min), the liquid fraction increased during sintering because diffusion was minimized and therefore local saturation could easily occur. The sintered density increased with increasing heating rate.

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Mechanical properties of sintered 7xxx series AI/SiCp composites
Kyung Ho Min, Baek-Hee Lee, Si-Young Chang, Young Do Kim
Materials Letters.2007; 61(11-12): 2544. CrossRef

Fabrication of Graphite-Ni Composite Powders and Effect of Thermal Spray Coating Parameters on Mechanical and Microstructural Properties: Joon-Chul Kwon, Mun-Kwan Cho, Il-Ho Kim, Tae-Whan Hong, Soon-Yong Kweon, Young-Geun Lee, Soon-Wook Park, Soon-Chul Ur; J Korean Powder Metall Inst. 2005;12(2):136-145.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.136

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Graphite-Ni composite powders were synthesized by mechanical alloying(MA) and spray drying(SD). Fabricated powders as well as commercial graphite-Ni powders were thermally sprayed on mild steel substrates using high velocity oxygen fuel (HVOF) thermal spray process and flame thermal spray process. The effects of several process parameters on related properties in thermally sprayed coatings have been investigated and correlated with microstructures in this study. The results indicated that the desired properties can be obtained when commercial powders were applied using HVOF process, while coating properties in case of MA powder application were inferior to those in HVOF process in so far. However, it is suggested that property enhancement can be obtained if the fraction of hexagonal graphite phase can be increased in mechanically alloyed powders.

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The Effect of Graphite Content on the Wear Behavior of Ni/WC/G Composite Coating
Gui Rong Yang, Chao Peng Huang, Wen Ming Song, Ying Ma, Yuan Hao
Advanced Materials Research.2015; 1120-1121: 702. CrossRef

Synthesis and Characterization of CNTs/Metal/Al₂O₃ Nanocomposite Powders by Thermal CVD: Yong-Ho Choa, Seung-Hwa Yoo, Jae-Kyo Yang, Sung-Tag Oh, Sung-Goon Kang; J Korean Powder Metall Inst. 2005;12(2):146-150.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.146

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Abstract PDF: An optimum route to synthesize Al_2O_3-based composite powders with homogeneous dispersion of carbon nanotubes (CNTs) was investigated. CNTs/Metal/Al_2O_3 nanocomposite powders were fabricated by thermal chemical vapor deposition of C_2H_2 gas over metal/Al_2O_3 nanocomposite catalyst prepared by selective reduction of metal oxide/Al_2O_3 powders. The FT-Raman spectroscopy analysis revealed that the CNTs have single- and multi-walled structure. The CNTs with the diameter of 25-43 nm were homogeneously distributed in the metal/Al_2O_3 powders, and their characteristics were strongly affected by a kind of metal catalyst and catalyst size. The experimental results show that the composite powder with required size and dispersion of CNTs can be realized by control of synthesis condition.

Preparation of Porous Graphite by Using Template of Co- and Ni-Magadiite: Soon-Yong Jeong; J Korean Powder Metall Inst. 2005;12(2):151-158.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.151

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Abstract PDF: Porous graphite was synthesized by removal of template in HF after pyrolysis of pyrolyzed fuel oil (PFO) at 900°C using the template of Co or Ni intercalated magadiite. Porous graphite had a plate structure like template, and d-spacing value of about 0.7 nm. The extent of crystallization of porous graphite was dependent on the contents of Co or Ni intercalated in interlayer. It can be explained that the metal such as Co and Ni acts as a promotion catalyst for graphite formation. Porous graphite shows the surface area of 328sim477 m2/g.

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