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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Powder Metallurgy Institute
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Journal DOI :
Korean Powder Metallurgy Institute
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Volume & Issues
Volume 16, Issue 6 - Dec 2009
Volume 16, Issue 5 - Oct 2009
Volume 16, Issue 4 - Aug 2009
Volume 16, Issue 3 - Jun 2009
Volume 16, Issue 2 - Apr 2009
Volume 16, Issue 1 - Feb 2009
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Battery Electrode Characteristics of Si-based Composite by Mechanical Alloying Method
Lee, Churl-Kyoung ; Lee, Jong-Ho ; Lee, Sang-Woo ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 389~395
DOI : 10.4150/KPMI.2009.16.6.389
A Si-CuO-graphite composite was prepared by a mechanical alloying (MA) method. The Si-CuO composite has a mixture structure, where CuO is homogeneously dispersed in Si. Also,
phases were formed during MA and heat treatment. Graphite with the Si-CuO composite was mixed in the same mill for 30 minutes with weight ratio of Si-CuO composite and graphite as 1:1. The Si-CuO composite was homogeneously covered with graphite. SiC phase was not formed. Electrochemical tests of the composite have been investigated, and the first charge and discharge capacities of the material were about 870mAh/g and 660mAh/g, respectively. Those values are about 76% of the first cycle efficiency. The cycle life of the composite showed that the initial discharge capacity of 660 mAh/g could be maintained up to 92% after 20 cycles.
Effects of Doping Elements and the Amounts of Oxygen/Nitrogen Contents in Final Nitrides on the Characteristics of Red Pigment of Tantalum Nitrides (Ta
Park, Eun-Young ; Pee, Jae-Hwan ; Kim, Yoo-Jin ; Cho, Woo-Seok ; Kim, Kyeong-Ja ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 396~402
DOI : 10.4150/KPMI.2009.16.6.396
Tantalum nitrides (
) have been developed to substitute the Cd based pigments for non-toxic red pigment. Various doping elements were doped to reduce the amount of high price Tantalum element used and preserve the red color tonality. Doping elements were added in the synthesizing process of precursor of amorphous tantalum oxides and then Tantalum nitrides doped with various elements were obtained by ammonolysis process. The average particle size of final nitrides with secondary phases was larger than the nitride without the secondary phases. Also secondary phases reduced the red color tonality of final products. On the other hand, final nitrides without secondary phase had orthorhombic crystal system and presented good red color. In other words, in the case of nitrides without secondary phases, doping elements made a solid solution of tantalum nitride. In this context, doping process controlled the ionic state of nitrides and the amount of oxygen/nitrogen in final nitrides affected the color tonality.
Microstructural Evolution of Thick Tungsten Deposit Manufactured by Atmospheric Plasma Spray Forming Route
Lim, Joo-Hyun ; Baik, Kyeong-Ho ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 403~409
DOI : 10.4150/KPMI.2009.16.6.403
Plasma spray forming is recently explored as a near-net-shape fabrication route for ultra-high temperature metals and ceramics. In this study, monolithic tungsten has been produced using an atmospheric plasma spray forming and subsequent high temperature sintering. The spray-formed tungsten preform from different processing parameters has been evaluated in terms of metallurgical aspects, such as density, oxygen content and hardness. A well-defined lamellae structure was formed in the as-sprayed deposit by spreading of completely molten droplets, with incorporating small amounts of unmelted/partially-melted particles. Plasma sprayed tungsten deposit had 84-87% theoretical density and 0.2-0.3 wt.% oxygen content. Subsequent sintering at 2500
promoted the formation of equiaxed grain structure and the production of dense preform up to 98% theoretical density.
A Study on Magnetic Properties of BaFe
Fabricated by Self-assembly Method
Choi, Moon-Hee ; Yu, Ji-Hun ; Kim, Dong-Hwan ; Lee, Hye-Mum ; Kim, Su-Min ; Kim, Yang-Do ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 410~415
DOI : 10.4150/KPMI.2009.16.6.410
Hexagonal barium ferrite (
) nano-particles have been successfully synthesised using selfassembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations.
powders were synthesized with addition Fe ions to Ba-DEA complex and then heat treated at temperature range of 800-1000
. The molar ratio of Ba/DEA and heat-treatment temperature significantly affected the magnetic properties and morphology of
powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at 1000
for 1 hour showed the coercive forces (iHc) of 4.84 kOe with average crystal size of about 200 nm.
Interfacial Characteristics and Mechanical Properties of HPHT Sintered Diamond/SiC Composites
Park, Hee-Sub ; Ryoo, Min-Ho ; Hong, Soon-Hyung ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 416~423
DOI : 10.4150/KPMI.2009.16.6.416
Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.
The Characteristic Changes of Electromagnetic Wave Absorption in Fe-based Nanocrystalline P/M Sheets Mixed with Ball-Milled Carbon Nanotubes
Kim, Sun-I ; Kim, Mi-Rae ; Sohn, Keun-Yong ; Park, Won-Wook ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 424~430
DOI : 10.4150/KPMI.2009.16.6.424
Electromagnetic wave energies are consumed in the form of thermal energy, which is mainly caused by magnetic loss, dielectric loss and conductive loss. In this study, CNT was added to the nanocrystalline soft magnetic materials inducing a high magnetic loss, in order to improve the dielectric loss of the EM wave absorption sheet. Generally, the aspect ratio and the dispersion state of CNT can be changed by the pre-ball milling process, which affects the absorbing properties. After the various ball-milling processes, 1wt% of CNTs were mixed with the nanocrystalline
base powder, and then further processed to make EM absorption sheets. As a result, the addition of CNT to Fe-based nanocrystalline materials improved the absorption properties. However, the increase of ball-milling time for more than 1h was not desirable for the powder mixture, because the ballmilling caused the shortening of CNT length and the agglomeration of the CNT flakes.
Effects of Chemical Composition and Particle Size of Starting Aluminum Source on the Spheroidization in the Flame Fusion Process
Eom, Sun-Hui ; Pee, Jae-Hwan ; Lee, Jong-Keun ; Hwang, Kwang-Taek ; Cho, Woo-Seok ; Kim, Kyeong-Ja ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 431~437
DOI : 10.4150/KPMI.2009.16.6.431
Various inorganic fillers improve the thermal conductivity and physical properties of organic products. Alumina has been used a representative filler in the heat radiation sheet for the heat radiation of electric device. The high filling rate of alumina increases the thermal conductivity and properties of products. We successfully developed the spherical alumina by flame fusion process using the oxygen burner with LPG fuel. In the high temperature flame (2500
) of oxygen burner, sprayed powders were melting and then rotated by carrier gas. This surface melting and rotation process made spherical alumina. Especially effects of chemical composition and particle size of stating materials on the melting behavior of starting materials in the flame and spheroidization ratio were investigated. As a result, spheroidization ratio of boehmite and aluminum hydroxide with endothermic reaction of dehydration process was lower than that of the sintered alumina without dehydration reaction.
Microstructure Control of Mg Alloy Powder Using a Repeated Extrusion Process
Kim, Jeong-Gon ; Choi, Han-Shin ; Kim, Taek-Soo ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 438~441
DOI : 10.4150/KPMI.2009.16.6.438
Mg-Cu composites were successively fabricated using a combination of rapid solidification and extrusion processes. In addition, the microstructural variation of the composite was investigated by performing the extrusion repeatedly. It resulted that the composite formed an uniform and dense structure by the extrusion, and the microstructure became fine as the extrusion conducted repeatedly. The microstructural variation was known to be dependent on the number of extrusion and the area reduction ratio. The tensile strength was also measured as a function of the microstructural variation.
Fabrication of ZrB
-based Composites for Ultra-high Temperature Materials
Kim, Seong-Won ; Chae, Jung-Min ; Lee, Sung-Min ; Oh, Yoon-Suk ; Kim, Hyung-Tae ; Nahm, Sahn ;
Journal of Korean Powder Metallurgy Institute, volume 16, issue 6, 2009, Pages 442~448
DOI : 10.4150/KPMI.2009.16.6.442
-based composites are candidate materials for ultra-high temperature materials (UHTMs).
has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation.
powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of
. In this study,
?based composites were successfully synthesized and densified through two different processing paths.
25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400
?20 vol.%SiC was fully densified with
as a sintering additive after hot pressing at 1900
. The synthesis mechanism and the effect of sintering additives on densification of
?SiC composites were also discussed.