Journal of Powder Materials

Nanotechnology and Computational Materials Simulation: J Korean Powder Metall Inst. 2003;10(2):71-82.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.071

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Study of Synthesis and Magnetic Properties of Ni and Ni-Cu Nano Metal Powders Prepared by the Pulsed Wire Evaporation(PWE) Method: J Korean Powder Metall Inst. 2003;10(2):83-88.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.083

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Nanocrystalline materials of Ni and Ni-Cu alloy have been synthesized by the pulsed wire evaporation (PWE) method and these abnormal magnetic properties in the magnetic ordered state have been characterized using both VSM and SQUID in the range of high and low magnetic fields. Ni and Ni-Cu particles with an average size of 20 to 80 nm were found to influence magnetic hysterisis behavior and the results of powder neutron diffraction patterns and saturation magnetization curves are shown to indicate the absence of the NiO phase. The shifted hysterisis loop and irreversibility of the magnetization curve in the high field region were observed in the magnetic-ordered state of both Ni and Ni-Cu. The virgin magnetization curve for Ni slightly spillover on the limited hysterisis loop (pm20kOe). This irreversibility in the high field of 50 kOe can be explained by non-col-linear behavior and the existence of the metastable states of the magnetization at the surface layer (or core) of the particle in the applied magnetic field. Immiscible alloy of Cu-Ni was also found to show irreversibility having two different magnetic phases.

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Fabrication of Ni-free Fe-based Alloy Nano Powder by Pulsed Wire Evaporation in Liquid: Part 2. Effect of Solvent and Comparison of Fabricated Powder owing to Fabrication Method
Ho-Jin Ryu, Yong-Heui Lee, Kwang-Ug Son, Young-Min Kong, Jin-Chun Kim, Byoung-Kee Kim, Jung-Yeul Yun
Journal of Korean Powder Metallurgy Institute.2011; 18(2): 112. CrossRef
Fabrication of Ni-free Fe-based Alloy Nano Powder by Pulsed Wire Evaporation in Liquid: Part I. Effect of Wire Diameter and Applied Voltage
Ho-Jin Ryu, Yong-Heui Lee, Kwang-Ug Son, Young-Min Kong, Jin-Chun Kim, Byoung-Kee Kim, Jung-Yeul Yun
Journal of Korean Powder Metallurgy Institute.2011; 18(2): 105. CrossRef
Cu–Ni–P alloy nanoparticles prepared by electrical wire explosion
Wonbaek Kim, Je-shin Park, Chang-yul Suh, Jong-Gwan Ahn, Jae-chun Lee
Journal of Alloys and Compounds.2008; 465(1-2): L4. CrossRef
A New Method for the Production of Alloy Nanoparticles by Electrical Wire Explosion
Wonbaek Kim, Je-shin Park, Chang-yul Suh, Jae-chun Lee, Junghwan Kim, Yong-Jun Oh
MATERIALS TRANSACTIONS.2007; 48(7): 1973. CrossRef

Effects of Mixing Ratio of the Milled Powder on Microstructure and Mechanical Properties of Sintered Valve Seats: J Korean Powder Metall Inst. 2003;10(2):89-96.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.089

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The recent trend of miniaturization and high performance of vehicle engines has put an urgent necessity for the development of valve seats which can operate under more severe conditions. In order to develope valve seat material that has the most excellent wear resistance at operating temperature of engine through improvement of the progress of work. the effects of mixing ratio of the milled powder on sintered and Cu-infiltrated properties of sintered valve seats have been studied. The resultant radial crushing strength and hardness of sintered specimens were gradually increased with increasement of volume of milled powders. It is because increasement of sintering density by increasing of surface diffusion. The hardness of Cu-infiltrated specimens became lower than that of the commercial powders as the increasement of volume of milled powders. It was due to the decrease of the amount of the martensite. By results of this research, It has been found that martensite is formed around of the Cu-infiltrated site and the decrease of the amount of the martensite is due to decrease of the amount of the Cu-infiltrated site by the decrease of gas channel.

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Thermal Properties and Microstructural Changes of Fe-Co System Valve Seat Alloy by High Densification Process
In-Shup Ahn, Dong-Kyu Park, Kwang-Bok Ahn, Seoung-Mok Shin
Journal of Korean Powder Metallurgy Institute.2019; 26(2): 112. CrossRef

Mechanical Properties of Al/Al₂O₃ Composite Fabricated by a Powder-in Sheath Rolling Method: J Korean Powder Metall Inst. 2003;10(2):97-102.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.097

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Abstract PDF: The powder-in sheath rolling was applied to the fabrication of Al/Al_2O_3 composite. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1 mm was used as a sheath. Mixture of aluminum powder and Al/Al_2O_3 particles of which volume content was varied from 5 to 20 vol.% was filled in the tube by tap filling and then rolled to 75% reduction at ambient temperature. The re]]ed specimen was sintered at 560°C for 0.5 hr. The Al/Al_2O_3 composite fabricated by the sheath rolling and subsequent sintering showed the relative density higher than 0.96. The tensile strength of the composite increased with the volume content of Al_2O_3 particles, and it reached a maximum of 90 MPa which is 1.5 times higher than unreinforced material. The elongation decreased with the volume content of Al_2O_3 particles. It is concluded that the powder-in sheath rolling is an effective method for fabrication of Al/Al_2O_3 composite.

Microstructures and Texture of Al/Al₂O₃ Composites Fabricated by a Powder-in Sheath Rolling Method: J Korean Powder Metall Inst. 2003;10(2):103-107.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.103

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Aluminum-based Al/Al_2O_3 composites were fabricated by a powder-in sheath rolling method. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1 mm was used as a sheath. A mixture of aluminum powder and Al_2O_3 particles of which volume content was varied from 5 to 20%, was filled in the tube by tap filling and then rolled by 75% reduction in thickness at ambient temperature. The rolled specimen was then sintered at 560°C for 0.5 h. The mixture of Al powders and Al_2O_3 particles was successfully consolidated by the sheath rolling. The Al/Al_2O_3 composite fabricated by the sheath rolling showed a recrystallized structure, while unreinforced Al powder compact fabricated by the same procedure showed a deformed structure. The unreinforced Al powder compact was characterized by a deformation (rolling) texture of which main component is 112<111>, while the Al/Al_2O_3 composite showed a mixed texture oi deformation and recrystallization. The sintering resulted in recrystallization in Al powder compact and grain growth in the composite.

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Fabrication and Evaluation of Carbon Nanotube Reinforced Al Matrix Composite by a Powder-in-sheath Rolling Method
Seong-Hee Lee, Dongmin Hong
Journal of Korean Powder Metallurgy Institute.2014; 21(1): 50. CrossRef
Microstructure and Mechanical Properties of CNT/Al Composite Fabricated by a Powder-in-Sheath Rolling Method utilizing Copper Tube as a Sheath
Seong-Hee Lee
Journal of Korean Powder Metallurgy Institute.2014; 21(5): 343. CrossRef
Fabrication and Evaluation of 5 vol%CNT/Al Composite Material by a Powder in Sheath Rolling Method
동민 홍, 성희 이, 우진 김
Korean Journal of Materials Research.2013; 23(11): 607~612. CrossRef

One-Step Synthesis of WC and Dense WC-10 vol.%Co Hard Materials and Their Mechanical Properties: J Korean Powder Metall Inst. 2003;10(2):108-117.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.108

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Abstract PDF: WC and dense WC-10 vol%Co materials with grain size of~1µm were synthesized by high-frequency induction heated combustion synthesis (HFIHCS) method in one step from elemental powders of W, C and Co within several minutes. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. In the absence of cobalt additive, WC can be formed, but its relative density was low (about 73%) under simultaneous application of a 60 MPa pressure and the induced current. However, in the presence of 10 vol.%Co, the relative density increased to 99% under the same experimental condition. The percentages of the total shrinkage occurring before and during the synthesis reaction of WC-10 vol.%Co were 5% and 51%, respectively. The fracture toughness and hardness values of WC-10 vol.%Co were 10 MPa . m1/2 and 1840 kg/mm2, respectively.

Effect of Phase Stability on the Microstructure Development of α-SiAlON Ceramics: Joosun Kim, Hae-Weon Lee, I-Wei Chen; J Korean Powder Metall Inst. 2003;10(2):118-122.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.118

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Abstract PDF: Alpha-SiAlON ceramics having various compositions and modifying cations were investigated with respect to their phase stability, transformation kinetics. and resulting microstructures. Each composition was heat treated at 1500°C for 1h and measured the alpha-SiAlON transformation. The phase-boundary composition in the single-phase alpha-SiAlON region showed sluggish transformation from alpha-Si_3N_4 to alpha-SiAlON compared to the phase-center composition in the diagram. Using the different rare earth modifying cations, dependence of transformation kinetics on the phase stability in a fixed composition was also explained. By changing size of the stable u-phase region with exchanging cations, systematic change in transformation was observed. Transformation rate of alpha-SiAlON at low temperature has an important role on controlling the final microstructure. Less transformation gives more chances to develop elongated grain in the microstructure.

Photocatalytic Properties of TiO₂ Nanopowder Synthesized by Chemical Vapor Condensation Process: J Korean Powder Metall Inst. 2003;10(2):123-128.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.123

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Abstract PDF: TiO_2 nanopowder was synthesized by chemical vapor condensation (CVC) process and its photocatalytic property depending on microstructure was considered in terns of decomposition rate of organic compound. In order to control microstructure of TiO_2 nanopowder such as particle size and degree of agglomeration, precursor flow rate representing number concentration was changed as a process variable. In TEM observation, spherical TiO_2 nanoparticles with average size of 20 nm showed gradual increases in particle size and degree of agglomeration with increase of precursor flow rate. Also decomposition rate of organic compound increased with decreasing precursor flow rate. Thus, it was concluded that photocatalytic property was enhanced by targe surface area of disperse TiO_2 nanoparticles synthesized at lower precursor flow rate condition in CVC process.

Synthesis of MnFeP_1-xAs_x Nanocrystalline Powders by High-Energy Ball Milling: J Korean Powder Metall Inst. 2003;10(2):129-135.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.129

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Nanocrystalline powders of MnFeP_1-xAs_x(x=0.45-0.6) have been synthesized by mechanochemical reaction at room temperature using high-energy ball milling from mixtures of Mn, Fe, P, and As Powders. It has been found that a mechanically induced self-propagating reaction (MSR) occurs within 2 hours of milling and it produces very fine polycrystalline powder having a hexagonal Fe_2P structure. Further milling up to 24 hours did not change the crystalline and average particle sizes or the phase composition of the milling product. When x is 0.65, no reaction among the reactants has been observed even after 24 hours of milling. As the P content decreases in MnFeP_1-xAs_x, the incubation time for the MSR has increased and the lattice constants in both a and c axes have changed.

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Magnetic transition of (MnFe)yP1−xAsx prepared by mechanochemical reaction and post-annealing
Y.K. Kim, Y.W. Cho
Journal of Alloys and Compounds.2005; 394(1-2): 19. CrossRef

Photocatalysis Characteristics of Nano Cu/TiO₂ Composite Powders Fabricated from Salt Solution: J Korean Powder Metall Inst. 2003;10(2):136-141.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.136

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Abstract PDF: In the present study, TiO_2 imbedded copper matrix powders have been successfully prepared from the (CuSO_4+TiO_2+Zn) composite salt solution. The composite Cu/TiO_2 powders were formed by drying the solution at 200sim~400°C in the hydrogen atmosphere. Photocatalytic characteristics was evaluated by detecting TOC (total organic carbon) amount with TOC analyzer (model 5000A Shimadzu Co). Phase analysis of Cu/TiO_2 composite powders was carried out by XRD, DSC and powder size was measured with TEM. The mean particle size of composite powders was about 100 nm and a few zinc and copper oxide phases was included. The reduction ratio of TOC amount was 60% by the composite Cu/TiO_2 powders under the UV irradiation for 8 hours.

MCP에 의한 나노분말합성 연구 동향: J Korean Powder Metall Inst. 2003;10(2):142-147.; DOI: https://doi.org/10.4150/KPMI.2003.10.2.142

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