Journal of Powder Materials

Thermoelectric Property of Ball Milled Bi-Te-Sb Powder: Ji-Hun Yu, Seung-Chul Bae, Gook-Hyun Ha, Byoung-Kee Kim, Gil-Gun Lee; J Korean Powder Metall Inst. 2005;12(6):387-392.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.387

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Abstract PDF: The p-type semiconductor Bi_2Te_3-Sb_2Te_3 thermoelectric materials were fabricated by melting, milling and sintering process and their thermoelectric properties were characterized. The compound materials were ball-milled with milling time and the powders were sintered by spark plasma sintering process. The ball milled powders had equiaxial shape and approedmately 1~3µm in size. The figure of meritz of sintered thermoelectric materials decreased with milling time because of lowered electrical resistivity. The thermoelectric properties of Bi_2Te_3-Sb_2Te_3 materials have been discussed in terms of electrical property with ball mill process.

Densification and Some Properties of Carbon Nanotubes-Dispersed Al₂O₃ Nanocomposite Powders: Seung-Hwa Yoo, Jae-Kyo Yang, Sung-Tag Oh, Kae-Myung Kang, Sung-Goon Kang, Yong-Ho Choa; J Korean Powder Metall Inst. 2005;12(6):393-398.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.393

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Abstract PDF: In-situ processing route was adopted to disperse carbon nanotubes (CNTs) into Al_2O_3 powders homogeneously. The Al_2O_3 composite powders with homogeneous dispersion of CNTs could be synthesized by a catalytic route for in-situ formation of CNTs on nano-sized Fe dispersed Al_2O_3 powders. CNTs/Fe/Al_2O_3 nanopowders were densified by spark plasma sintering (SPS). The hardness and bending strength as well as electrical conductivity increased with increasing sintering temperature. However, the electrical conductivity of the composites sintered at above 1500°C showed decreased value with increasing sintering temperature due to the oxidation of CNTs.

Fabrication of Transition-metal-incorporated TiO₂ Nanopowder by Flame Synthesis: Hoon Park, Hyunseock Jie, Seung-Yong Lee, Jae-Pyoung Ahn, Dok-Yol Lee, Jong-Ku Park; J Korean Powder Metall Inst. 2005;12(6):399-405.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.399

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Abstract PDF: Nanopowders of titanium dioxide (TiO_2) incorporating the transition metal element(s) were synthesized by flame synthesis method. Single element among Fe(III), Cr(III), and Zn(II) was doped into the interior of TiO_2 crystal; bimetal doping of Fe and Zn was also made. The characteristics of transition-metal-doped TiO_2 nanopowders in the particle feature, crystallography and electronic structures were determined with various analytical tools. The chemical bond of Fe-O-Zn was confirmed to exist in the bimetal-doped TiO_2 nanopowders incorporating Fe-Zn. The transition element incorporated in the TiO_2 was attributed to affect both Ti 3d orbital and O 2p orbital by NEXAFS measurement. The bimetal-doped TiO_2 nanopowder showed light absorption over more wide wavelength range than the single-doped TiO_2 nanopowders.

Synthesis and Properties of Amorphous Matrix Composites using Cu-based/Ni-based Amorphous Powders: Taek-Soo Kim, Jin-Kyu Lee, Hwi-Jun Kim, Jung-Chan Bae; J Korean Powder Metall Inst. 2005;12(6):406-412.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.406

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This work is to present a new synthesis of metallic glass (MG)/metallic glass (MG) composites using gas atomization and spark plasma sintering (SPS) processes. The MG powders of Cu_54Ni_6Zr_22Ti_18 (CuA) and Ni_59Zr_15Ti_13Nb_7Si_3Sn_2Al_1(NiA) as atomized consist of fully amorphous phases and present a different thermal behavior; T_g (glass transition temperature) and T_x (crystallization temperature) are 716K and 765K for the Cu base powder, but 836K and 890K for the Ni base ones, respectively. SPS process was used to consolidate the mixture of each amorphous powder, being CuA/10%NiA;and;NiA/10%CuA in weight. The resultant phases were Cu crystalline dispersed NiA matrix composites as well as NiA phase dispersed CuA matrix composites, depending on the SPS temperatures. Effect of the second phases embedded in the MG matrix was discussed on the micro-structure and mechanical properties.

Citations

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Micro-deformation behavior of Brittle Hf-based Metallic Glass during Mechanical Milling
Song-Yi Kim, A-Young Lee, Eun-Ji Cha, Do-Hun Kwon, Sung-Uk Hong, Min-Woo Lee, Hwi-Jun Kim, Min-Ha Lee
journal of Korean Powder Metallurgy Institute.2018; 25(3): 246. CrossRef
Synthesis of Ni-based Metallic Glass Composite Fabricated by Spark Plasma Sintering
Song Yi Kim, Bo Kyeong Guem, Min Ha Lee, Bum Sung Kim
Journal of Korean Powder Metallurgy Institute.2013; 20(1): 33. CrossRef

Effect of CeO₂ Coating on the Grain Growth of Cu Particles: Hee-Jun Yoo, Ji-Woong Moon, You Oh, Jooho Moon, Hae Hwang; J Korean Powder Metall Inst. 2005;12(6):413-421.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.413

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Abstract PDF: Copper is able to work as a current collector under wide range of hydrocarbon fuels without coking in Solid oxide fuel cells (SOFCs). The application of copper in SOFC is limited due to its low melting point, which result in coarsening the copper particle. This work focuses on the sintering of copper powder with ceria coating layer. Ceria-coated powder was prepared by thermal decomposition of urea in Ce(NO_3)_3cdot6H_2O solution, which containing CuO core particles. The ceria-coated powder was characterized by XRD, ICP, and SEM. The thermal stability of the ceria-coated copper in fuel atmosphere (H_2) was observed by SEM. It was found that the ceria coating layer could effectively hinder the grain growth of the copper particles.

Study of Hydrolysis of Al Powder and Compaction of Nano Alumina by Spark Plasma Sintering(SPS): Y. Uhm, M. Lee, C. Rhee; J Korean Powder Metall Inst. 2005;12(6):422-427.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.422

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Abstract PDF: The Al_2O_3 with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite (beta-Al(OH)_3) phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of 100°C per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from 100°C;to; 1100°C, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of Al(OH)_3toeta-Al_2O_3totheta-Al_2O_3toalpha-Al_2O_3 sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to gamma-Al_2O_3;at;350°C. It shows AlO(OH) gamma-Al_2O_3todelta-Al_2O_3toalpha-Al_2O_3 sequences. The gamma-Al_2O_3 compacted at 550°C shows a high surface area (138m2/g).

Preparation of Silver-doped Hydroxyapatite Using Sol-gel Method: Byung-Bae Mun, Ho-Kun Kim; J Korean Powder Metall Inst. 2005;12(6):428-432.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.428

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Abstract PDF: In the present study, silver-doped antibacterial hydroxyapatites were successfully prepared by the sol-gel method. For the starting solution, the molar ratio of Ca(NO_3)_2cdot4H_2O, P(OC_2H_5)_3,;C_2H_5OH,;and;H_O was set to 0.075:0.045:20:0.135; AgNO_3 was added to a ratio of Ag to total cation concentration of 0.5-12 mol%. The prepared sol was dried at 100°C for 48h and heat-treated at 1000°C for 2h to obtain particles in the 200-500nm size range. The product from the synthesis of silver-doped hydroxyapatite was investigated through X-ray diffraction experiments and scanning electron microscopy. The product showed high antibacterial properties, with a disinfection ratio of Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922) over 99.9°C as calculated from an antimicrobial effects evaluation by the shake flask method.

Hydrogen Absorption Properties of Nanocrystalline Zr₅₇V₃₆Fe₇ Getter alloy: Je-Shin Park, Chang-Youl Suh, Won-Baek Kim; J Korean Powder Metall Inst. 2005;12(6):433-440.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.433

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Abstract PDF: The hydrogen sorption speed of Zr_57V_36Fe_7 nanocrystalline and amorphous alloys was evaluated at room temperature. Nanocrystalline alloys of Zr_57V_36Fe_7 were prepared by planetary ball milling. The hydrogen sorption speed of nanocrystalline alloys was higher than that of the amorphous alloy. The enhanced sorption speed of nanocrystalline alloys was explained in terms of surface oxygen stability which has been known to retard the activation of amorphous alloys. The retardation can be reduced by formation of nanocrystals, which results in the observed increase in sorption properties.

The study of Synthesis of Dihydropyrimidine for Cardiotropic Drugs Using New Catalysts on the Basis of Nano Cu Oxides: Y. Uhm, M. Lee, C. Rhee; J Korean Powder Metall Inst. 2005;12(6):441-446.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.441

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Abstract PDF: The copper oxide nano powders were synthesized by levitational gas condensation (LGC) method, and were applied to catalyst to fabricate 3,4-dihydropyrimidin-2-(1H)-one. Processes of adsorption of Biginelli reaction reagents on the copper nanooxide surface Cu_2O°CuO were studied by IR-spectroscopy. It was shown that benzaldehyde coordination, acetoacetic ether on the oxide surface is carried out with participation of carbonyl fragments, urea by N-H bonds which affects positively on the reagents reactivity.

Synthesis of Titanium Silicide by Electro-Discharge-Sintering of Ti and Si Powder Mixture: Y. Cheon, N. Oh, Y. Kim, C. Byun, S. Lee, W. Lee; J Korean Powder Metall Inst. 2005;12(6):447-452.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.447

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Abstract PDF: The synthesis and consolidation of titanium silicide by electro-discharge-sintering has been investigated. As-received Ti powder was in flaky shape and the mean particle size was 45.0µm, whereas the mean particle size of the pre-milled Si powder with angular shape was 8.0µm. Single pulse of 2.5 to 5.0 kJ/0.34g-elemental Ti and pre-milled Si powder mixture with the composition of Ti-37.5at.% Si was applied using 300µF capacitor. The solid with Ti_5Si_3 phase has been successfully fabricated by the discharge with the input energy more than 2.5kJ in less than 129µsec. Hv values were found to be higher than 1000kgf/mm2. The formation of Ti_5Si_3 occurred through a fast solid state diffusion reaction.

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