Journal of Powder Materials

Powder Metallurgy Process in Bulk Amorphous Alloys: Hwi-Jun Kim, Jung-Chan Bae, Do-Hyang Kim; J Korean Powder Metall Inst. 2006;13(6):387-395.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.387

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A study on the Particulate Properties of Ti-Ni alloy Nanopowders Prepared by Levitational Gas Condensation Method: B.S. Han, Y.R. Uhm, M.K. Lee, G.M. Kim, C.K. Rhee; J Korean Powder Metall Inst. 2006;13(6):396-400.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.396

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Abstract PDF: The Ti-Ni alloy nanopowders were synthesized by a levitational gas condensation (LGC) by using a micron powder feeding system and their particulate properties were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) method. The starting Ti and Ni micron powders 150µm were incorporated into the micron powder feeding system. An ingot type of the Ti-Ni ahoy was used as a seed material for the levitation and evaporation reactions. The collected powders were finally passivated by oxidation. The x-ray diffraction experiments have shown that the synthesized powders were completely alloyed with Ti and Ni and comprised of two different cubic and monoclinic crystalline phases. The TEM results showed that the produced powders were very fine and uniform with a spherical particle size of 18 to 32nm. The typical thickness of a passivated oxide layer on the particle surface was about 2 to 3 nm. The specific surface area of the Ti-Ni alloy nanopowders was 60m2/g based on BET method.

Room-temperature Ferromagnetism in Fe-doped Reduced TiO_2-δ: H.M. Lee, C.S. Kim, Y.R. Uhm, C.K. Rhee; J Korean Powder Metall Inst. 2006;13(6):401-407.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.401

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Abstract PDF: Effects of oxygen deficiency on the room temperature ferromagnetism in Fe-doped reduced TiO_2 have been investigated by comparing the air-annealed Ti_0.97Fe_0.03O_2 compound with secondly post-annealed one in vacuum ambience. The air-annealed sample showed a paramagnetic behavior at room temperature. However, when the sample was further annealed in vacuum, a strongly enhanced ferromagnetic behavior was observed at same temperature. M"ossbauer spectra of air-annealed sample at 295K showed a single doublet of Fe3+

Complex Forming of the High-Functional Intermetallic Compound by the In Process Synthesis: Jung-Hyun Han, Seong-Kab Park, Yong-Ho Park; J Korean Powder Metall Inst. 2006;13(6):408-414.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.408

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Abstract PDF: [ MoSi_2 ] alloys with Al, B or Nb were prepared by an advanced consolidation process that combined mechanical alloying with pulse discharge sintering (complex forming) to improve the mechanical properties. Their microstructure and mechanical properties were investigated. The MoSi_2 alloys fabricated by complex forming method showed very fine microstructure when compared with the sample sintered from commercial MoSi_2 powders. Alloys made from powders milled in Ar gas had fewer silica or alumina phases as compared to their counterparts sintered from powders milled in air. In densification of the sintered body, addition of B was more effective than Al or Nb. Both Victors hardness and tensile test indicated that the alloy fabricated by the complex forming method showed better properties than the sample sintered from commercial MoSi_2 powders. The Al added alloy sintered from the powders milled in air had the superior mechanical properties due to the suppression of SiO_2 and formation of fine Al_2O_3 particles.

Finite Element Analysis of Densification Behavior during Equal Channel Angular Pressing Process of Powders: Seung-Chae Yoon, Pham Quang, Byong-Sun Chun, Hong-Ro Lee, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2006;13(6):415-420.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.415

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Abstract PDF: Nanostructured metallic materials are synthesized by bottom-up processing which starts with powders for assembling bulk materials or top-down processing starting with a bulk solid. A representative bottom-up and top-down paths for bulk nanostructured/ultrafine grained metallic materials are powder consolidation and severe plastic deformation (SPD) methods, respectively. In this study, the bottom-up powder and top-down SPD approaches were combined in order to achieve both full density and grain refinement without grain growth, which were considered as a bottle neck of the bottom-up method using conventional powder metallurgy of compaction and sintering. For the powder consolidation, equal channel angular pressing (ECAP), one of the most promising method in SPD, was used. The ECAP processing associated with stress developments was investigated. ECAP for powder consolidation were numerically analyzed using the finite element method (FEM) in conjunction with pressure and shear stress.

Effect of Heat Treatment on the Microstructure and Mechanical Properties for Al-Si Alloyed Powder Material by Gas Atomizing and Hot Extrusion Process: Ki-Young Nam, Hyeong-Ho Jin, Yong-Jin Kim, Seog-Young Yoon, Yong-Ho Park; J Korean Powder Metall Inst. 2006;13(6):421-426.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.421

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Abstract PDF: The microstructural and mechanical properties of Al-Si alloyed powder, prepared by gas atomization fallowed by hot extrusion, were studied by optical and scanning electron microscopies, hardness and wear testing. The gas atomized Al-Si alloy powder exhibited uniformly dispersed Si particles with particle size ranging from 5 to 8µm. The hot extruded Al-Si alloy shows the average Si particle size of less than 1µm. After heat-treatment, the average particle size was increased from 2 to 5µm. Also, mechanical properties of extruded Al-Si alloy powder were analyzed before and after heat-treatment. As expected from the microstructural analysis, the heat-treated samples resulted in a decrease in the hardness and wear resistance due to Si particle growth. The friction coefficient of heat-treated Al-Si alloyed powder showed higher value tough all sliding speed. This behavior would be due to abrasive wear mechanism. As sliding speed increases, friction coefficient and depth and width of wear track increase. No significant changes occurred in the wear track shape with increased sliding speed.

Materials Properties of Gas Atomized and Extruded Mg-Zn-Y Alloys: Hong-Jun Chae, Jin-Kyu Lee, Jung-Chan Bae, Taek-Soo Kim; J Korean Powder Metall Inst. 2006;13(6):427-431.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.427

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Mg-4.3Zn-0.7Y (at%) alloy powders were prepared using an industrial scale gas atomizer, followed by warm extrusion. The powders were almost spherical in shape. The microstructure of atomized powders and those extruded bars was examined using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscope (EDS) and X-ray Diffractometer (XRD). The grain size of the powders was coarsen as the initial powder size increased. After the extrusion, the grain size became fine due to the severe plastic deformation during the extrusion with the ratio of 10:1. Both the ultimate strength and elongation were enhanced with the decrease of initial particle size.

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Fabrication and Dynamic Consolidation Behaviors of Rapidly Solidified Mg Alloy Powders
Hong-Jun Chae, Young-Do Kim, Taek-Soo Kim
Journal of Korean Powder Metallurgy Institute.2011; 18(4): 340. CrossRef

Synthesis of Aluminum Nitride Nanopowders by Carbothermal Reduction of Aluminum Oxide and Subsequent In-situ Nitridization: Kyung-Won Seo, Seong-Yong Lee, Jong-Ku Park, Sung-Hyun Kim; J Korean Powder Metall Inst. 2006;13(6):432-438.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.432

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Aluminum nitride (AlN) nanopowders with low degree of agglomeration and uniform particle size were synthesized by carbothermal reduction of alumina and subsequent direct nitridization. Boehmite powder was homogeneously admixed with carbon black nanopowders by ball milling. The powder mixture was treated under ammonia atmosphere to synthesize AlN powder at lour temperature. The effect of process variables such as boehmite/carbon black powder ratio, reaction temperature and reaction time on the synthesis of AlN nanopowder was investigated.

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A Scale-Up Test for Preparation of AlN by Carbon Reduction and Subsequent Nitridation Method
Hyung-Kyu Park, Sung-Don Kim, Chul-Woo Nam, Dae-Woong Kim, Moon-Soo Kang, Gwang-Hee Shin
Journal of the Korean Institute of Resources Recycling.2016; 25(5): 75. CrossRef

Occurrence Mechanism of Magnetic Properties in BiSrCaCuO Superconductor: Sang-Heon Lee; J Korean Powder Metall Inst. 2006;13(6):439-444.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.439

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Abstract PDF: An electromagnetic properties in BiSrCaCuO superconductor were studied. In the measurement of current-voltage properties, the voltage was measured when applying an external magnetic field. The voltage continues to appear after the removal of the magnetic field. This phenomenon was considered as a nonvolatile magnetic effect. The voltage increased with the applied magnetic flux, but it became constant at about 10-2T. The appearance of the voltage was ascribed to the trapping of magnetic flux.

An Empirical Study on Drilling Characteristics of Titanium Carbide Metal Matrix Composites (1): Jeong-Keun Lee; J Korean Powder Metall Inst. 2006;13(6):445-449.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.445

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Abstract PDF: The experimental data from the central composite design runs were utilized for mathematical models far the drilling characteristics containing linear, quadratic and interactive effects of the parameters such as volume fraction of TiC in the composites, drill speed, feed rate and drill diameter. The models were developed via stepwise selection where the insignificant effects were removed using t-test. The models were subjected to optimization of maximizing drill life and satisfying the other constraints.

Abrasiveness Behavior of Counterpart Sliding Against Titanium Carbide Based Metal Matrix Composite: Jeong-Keun Lee; J Korean Powder Metall Inst. 2006;13(6):450-454.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.450

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Abstract PDF: Wear of steel plate was measured during unlubricated sliding against TiC composites. These composites consist of round TiC grains and steel matrix. TiC grain itself exhibits low surface roughness and round shape, which does not bring its counterpart into severe damage from friction. In our work a classical experimental design was applied to find out a dominant factor in counterpart wear. The analysis of the data showed that only the applied load has a significant effect on the counterpart wear. Wear rate of counterpart increased non-linearly with applied load. Amount of wear was discrepant from expectation of being in proportion to the load by analogy with friction force. Our experimental result from treating matrix variously revealed bimodal wear behavior between the composites and counterpart where a mode seems to result from the special lubricant characteristic of TiC grains, and the other is caused by metal-to-metal contact. The two wear mechanisms were discussed.

Measurement of High Temperature Dielectric Property at Microwave Frequency Using Cavity Perturbation Method: Dong-Eun Kim, Jin-Ho Jung, Sung-Min Lee, Hyung-Tae Kim; J Korean Powder Metall Inst. 2006;13(6):455-461.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.455

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High temperature dielectric constants of the various ceramic materials have been measured using cavity perturbation method. The measurements were applied to refractory, traditional and fine ceramic powder compacts from room temperature to 1200°C. Calibration constant in the equation suggested by Hutcheon et al., was determined from the dielectric constants of reference specimen (teflon and alumina) at room temperature. From these results, informations on the refectory materials were obtained for the microwave kiln design and understanding of the microwave heating effects of ceramics have been improved.

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Dielectric Properties of β-SiAlON at High Temperature Using Perturbation Method
Young Hoon Seong, Ha Neul Kim, Do Kyung Kim
Key Engineering Materials.2008; 403: 121. CrossRef

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