Journal of Powder Materials

Fabrication and Applications of Cemented Carbide: J Korean Powder Metall Inst. 2003;10(6):365-373.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.365

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Synthesis of WC-10wt.%Co Nanocrystalline Powders with Grain Growth Inhibitor by MTP
Dong Kyu Park, Kwang Chul Jung, Jin Chun Kim, Sung Yeal Bae, In Sup Ahn
Materials Science Forum.2007; 534-536: 1237. CrossRef

Studies on Microstructural Phenomena Caused by Atomic Diffusion in Sintered Materials: Koji Hayashi; J Korean Powder Metall Inst. 2003;10(6):374-382.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.374

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Abstract PDF: During the sintering of powder materials, many these are microstructural phenomena are caused by atomic diffusion. (1) neck formation and compact densification, (2) grain growth, i.e., growth of matrix grains and dispersed grains, (3) alloying or generation of compound, (4) generations of peculiar and hard layers near sintered compact surface, etc. The studies of the present author and co-workers on these phenomena which were carried out during 40 years are briefly introduced.

Powder Metallurgy for Light Weight and Ultra-Light Weight Materials: B. Kieback, G. Stephani, T. Weiβgarber, T. Schubert, U. Waag, A. Bohm, O. Anderson, H. Gohler, M. Reinfried; J Korean Powder Metall Inst. 2003;10(6):383-389.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.383

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As in other areas of materials technology, the tendency towards light weight constructions becomes more and more important also for powder metallurgy. The development is mainly driven by the automotive industry looking for mass reduction of vehicles as a major factor for fuel economy. Powder metallurgy has to offer a number of interesting areas including the development of sintered materials of light metals. PM aluminium alloys with improved properties are on the way to replace ferrous pars. For high temperature applications in the engine, titanium aluminide based materials offer a great potential, e.g. for exhaust valves. The PM route using elemental powders and reactions sintering is considered to be a cost effective way for net shape parts production. Furthermore it is expected that lower costs for titanium raw materials coming from metallurgical activities will offer new chances for sintered parts with titanium alloys. The field of cellular metals expands with the hollow sphere technique, that can provide materials of many metals and alloys with a great flexibility in structure modifications. These structures are expected to be used in improving the safety (crash absoption) and noise reduction in cars in the near future and offer great potential for many other applications.

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Effects of Fused Silica Addition on Thermal Expansion, Density, and Hardness of Alumix-231 Based Composites
Luciano M. Rodrigues, Bojan A. Marinkovic
Materials.2022; 15(10): 3476. CrossRef

Synthesis of Ultrafine Titanium Carbide Powder by Novel Thermo-Reduction Process: Alexandrovskii S.V.; J Korean Powder Metall Inst. 2003;10(6):390-394.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.390

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Ultra fine titanium carbide particles were synthesized by novel metallic thermo-reduction process. The vaporized TiC1_4+CCl_4 gases were reacted with liquid magnesium and the fine titanium carbide particles were then produced by combining the released titanium and carbon atoms. The vacuum treatment was followed to remove the residual phases of MgC1_2 and excess Mg. The stoichiometry, microstructure, fixed and carbon contents and lattice parameter were investigated in titanium carbide powders produced in various reaction parameters.

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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
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
Quantitative Study on the Refinement Behaviors of TiC Powders Produced by Mechanical Milling Under Different Impact Energy
Sung-Mo Hong, Eun-Kwang Park, Kyeong-Yeol Kim, Jin-Ju Park, Min-Ku Lee, Chang-Kyu Rhee, Jin-Kyu Lee, Young-Soon Kwon
Journal of Korean Powder Metallurgy Institute.2012; 19(1): 32. 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

Characteristics of Powder with Change of Temperature in Production of Tantalum Powder by MR-EMR Combination Process: J Korean Powder Metall Inst. 2003;10(6):395-405.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.395

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Abstract PDF: In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of K_2TaF_7. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

Nano Structure and Mechanical Properties of Rapidly Solidified Al_81-(x+y)Si₁₉Ni_xCe_y Alloy: J Korean Powder Metall Inst. 2003;10(6):406-414.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.406

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Abstract PDF: In order to produce good wear resistance powder metallurgy Al-Si alloys with high strength, addition of glass forming elements of Ni and Ce in Al_81Si_19 alloy was examined using SEM, TEM, tensile strength and wear testing. The solubility of Si in aluminum increased with increasing Ni and Ce contents for rapidly solidified powders. These bulk alloys consist of a mixed structure in which fine Si particles with a particle size below 500 nm and very fine A1_3Ni, A1_3Ce compounds with a particle size below 200 nm are homogeneously dispersed in aluminum matrix with a grain size below 600 nm. The tensile strength at room temperature for Al_81Si_19, Al_78Si_19Ni_2Ce_0.5, and Al_76Si_19Ni_4Ce_1 bulk alloys extruded at 674 K and ratio of 10 : 1 is 281,521, and 668 ㎫ respectively. Especially, Al_73Si_19Ni_7Ce_1 bulk alloy had a high tensile strength of 730 ㎫. These bulk alloys are good wear-resistance bel ter than commercial I/M 390-T6. Specially, attactability for counterpart is very little, about 15 times less than that of the I/M 390-T6. The structural refinement by adding glass forming elements such as Ni and Ce to hyper eutectic Al_81Si_19 alloy is concluded to be effective as a structural modification method.d.tion method.

Fabrication of Al Flake Powder for Pigment: J Korean Powder Metall Inst. 2003;10(6):415-421.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.415

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Abstract PDF: The study for producing the flake powders by milling of aluminum foil and gas atomized powders was carried out. The effects of lifter bars on the ball motions and milling of aluminum foils were also investigated. The aluminum foils were laminated each other, elongated, fragmented into small foils and finally formed into the flake powders during the dry ball-milling. The spherical atomized-powders were milled to coarse flake powders with high aspect ratio and then changed to fine flake powders with lower aspect ratio. Even though long times were required for making flake powders by milling of foils, the water covering areas of them were higher than those of powders milled using gas-atomized powders, suggesting aluminum foils were more plastically deformed by micro-forging. On the other hand, as the number of lifter bars increased, the necessary rotation speeds of milling jar for cascading mode and cataracting mode decreased drastically. It was possible to achieve same quality of milled flake powder by using the lifter bars under the lower milling speeds. The painting test showed that the appearance of painted surface was good and optimum content range of aluminum paste in car paint to maximize the degree of gloss was 3-5%.

A Study on the Reduction Mechanism of Tungsten and Copper Oxide Composite Powders: Seong Lee, Moon-Hee Hong, Eun-Pyo Kim, Sung-Ho Lee, Joon-Woong Noh; J Korean Powder Metall Inst. 2003;10(6):422-429.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.422

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Abstract PDF: The reduction mechanism of the composite powders mixed with WO_3 and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 200°C to 300°C. Then, WO_3 powder is reduced to W O_2 via W O_2.9 and W O_2.72 at higher temperature region. Finally, the gaseous phase of WO_3(OH)_2 formed by reaction of WO_2 with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and WO_3 powder.

Characteristics of Nano-dispersed Powder by Electric Explosion of Conductors: Young-Soon Kwon, Ji-Soon Kim, Jin-Soo Moon, Hwan-Tae Kim, Alexander-P Ilyin, Chang-Kyu Rhee, Geun-Hie Rim; J Korean Powder Metall Inst. 2003;10(6):430-435.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.430

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Abstract PDF: The phenomenon of electrical explosion of conductors is considered in the context of the changes in the energy and structural states of the metal at the stages of energy delivery and relaxation of the primary products of EEC. It is shown that these changes are related to the forced interaction of an intense energy flux with matter and to the subsequent spontaneous relaxation processes. The characteristics of nano-sized metal powders are also discussed. The preferential gas media during EEC is Ar+H_2. An increase in e/e_s (in the range of values studied) leads to a reduction in the metal content. For reactive powders obtained with high metal content, it is necessary to separate the SFAP fractions, which settled on the negative electrode of the electric filter.

Synthesis Of Nd₂Fe₁₄B Powders by Spray-Drying and Reduction-Diffusion Process: J Korean Powder Metall Inst. 2003;10(6):436-442.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.436

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Abstract PDF: The magnetic Nd-Fe-B powders were prepared by a thermochemical method, consisting of the processes of spray-drying, debinding, milling, H_2-reduction, Ca-reduction, and washing. The optimum process conditions were studied by microstructural and thermal analysis. The resultant Nd-Fe-B powder was spherical with the size of 1 µtextrmm. Effects of the process parameters of each step on the microstructure of the powders were investigated, and their magnetic properties were evaluated.

In-situ Synthesis of Cu-TiB₂ Nanocomposite by MA/SPS: Young-Soon Kwon, Ji-Soon Kim, Hwan-Tae Kim, Jin-Soo Moon, Dudina D.V, Lomovsky O.I.; J Korean Powder Metall Inst. 2003;10(6):443-447.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.443

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Abstract PDF: Nano-sized TiB_2 was in situ synthesized in copper matrix through self-propagating high temperature synthesis (SHS) with high-energy ball milled Ti-B-Cu elemental mixtures as powder precursors. The size of TiB_2 particles in the product of SHS reaction decreases with time of preliminary mechanical treatment ranging from 1 in untreated mixture to 0.1 in mixtures milled for 3 min. Subsequent mechanical treatment of the product of SHS reaction allowed the TiB_2 particles to be reduced down to 30-50 nm. Microstructural change of TiB_2-Cu nanocomposite during spark plasma sintering (SPS) was also investigated. Under simultaneous action of pressure, temperature and electric current, titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a interpenetrating phase composite with a fine-grained skeleton.

Effect of the Flow Rate of Flame Gases on the Crystal Structure of TiO₂ Nanopowder Synthesized by Flame Method: J Korean Powder Metall Inst. 2003;10(6):448-455.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.448

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TiO_2 nanopowder has been synthesized by means of the flame method using a precursor of titanium tetraisopropoxide (TTIP, Ti(OC_3H_7)_4). In order to clarify the effect of cooling rate of hot flame on the formation of TiO_2 crystalline phases, the flame was controlled by varying the mixing ratio and the flow rate of gases. Anatase phase was predominantly synthesized under the condition having the steep cooling gradient in flame, while a slow cooling gradient enabled to form almost rutile TiO_2 nanopowder of above 95%.

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HRTEM Study of Phase Transformation from Anatase to Rutile in Nanocrystalline TiO₂ Particles
Kyou Hyun Kim, Hoon Park, Jae Pyong Ahn, Jael Chul Lee, Jong Ku Park
Materials Science Forum.2007; 534-536: 65. CrossRef

Heat Sink용 분말재료의 현황 및 전망: J Korean Powder Metall Inst. 2003;10(6):456-462.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.456

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