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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 23, Issue 3 - Jun 2016
Volume 23, Issue 2 - Apr 2016
Volume 23, Issue 1 - Feb 2016
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Synthesis of KIT-1 Mesoporous Silicates Showing Two Different Macrosporous Strucrtues; Inverse-opal or Hollow Structures
Baek, Youn-Kyoung ; Lee, Jung-Goo ; Kim, Young Kuk ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 189~194
DOI : 10.4150/KPMI.2016.23.3.189
We report a facile method for preparing KIT-1 mesoporous silicates with two different macroporous structures by dual templating. As a template for macropores, polystyrene (PS) beads are assembled into uniform three dimensional arrays by ice templating, i.e., by growing ice crystals during the freezing process of the particle suspension. Then, the polymeric templates are directly introduced into the precursor-gel solution with cationic surfactants for templating the mesopores, which is followed by hydrothermal crystallization and calcination. Later, by burning out the PS beads and the surfactants, KIT-1 mesoporous silicates with macropores are produced in a powder form. The macroporous structures of the silicates can be controlled by changing the amount of EDTANa4 salt under the same templating conditions using the PS beads and inverse-opal or hollow structures can be obtained. This strategy to prepare mesoporous powders with controllable macrostructures is potentially useful for various applications especially those dealing with bulky molecules such as, catalysis, separation, drug carriers and environmental adsorbents.
Spark Plasma Sintering Behavior and Heat Dissipation Characteristics of the Aluminum Matrix Composite Materials with the Contents of Graphite
Kwon, Hansang ; Park, Jehong ; Joo, Sungwook ; Hong, Sanghwui ; Mun, Jihoon ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 195~201
DOI : 10.4150/KPMI.2016.23.3.195
Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.
A Study on Synthesis of Ni-Ti-B Alloy by Mechanical Alloying from Elemental Component Powder
Kim, Jung Geun ; Park, Yong Ho ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 202~206
DOI : 10.4150/KPMI.2016.23.3.202
A Ni-Ti-B alloy powder prepared by mechanical alloying (MA) of individual Ni, Ti, and B components is examined with the aim of elucidating the phase transitions and crystallization during heat treatment. Ti and B atoms penetrating into the Ni lattice result in a Ni (Ti, B) solid solution and an amorphous phase. Differential thermal analysis (DTA) reveals peaks related to the decomposition of the metastable Ni (Ti, B) solid solution and the separation of equilibrium
phases. The exothermal effects in the DTA curves move to lower temperatures with increasing milling time. The formation of a
phase by annealing indicates that the mechanochemical reaction of the Ni-Ti-B alloy does not comply with the alloy composition in the ternary phase diagram, and Ti-B bonds are found to be more preferable than Ni-B bonds.
Spark Plasma Sintering of Fe-Ni-Cu-Mo-C Low Alloy Steel Powder
Nguyen, Hong-Hai ; Nguyen, Minh-Thuyet ; Kim, Won Joo ; Kim, Ho Yoon ; Park, Sung Gye ; Kim, Jin-Chun ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 207~212
DOI : 10.4150/KPMI.2016.23.3.207
In this study, Fe-Cu-Ni-Mo-C low alloy steel powder is consolidated by spark plasma sintering (SPS) process. The internal structure and the surface fracture behavior are studied using field-emission scanning electron microscopy and optical microscopy techniques. The bulk samples are polished and etched in order to observe the internal structure. The sample sintered at
with holding time of 10 minutes achieves nearly full density of 98.9% while the density of the as-received conventionally sintered product is 90.3%. The fracture microstructures indicate that the sample prepared at
by the SPS process is hard to break out because of the presence of both grain boundaries and internal particle fractures. Moreover, the lamellar pearlite structure is also observed in this sample. The samples sintered at 1000 and
exhibit a large number of tiny particles and pores due to the melting of Cu and aggregation of the alloy elements during the SPS process. The highest hardness value of 296.52 HV is observed for the sample sintered at
with holding time of 10 minutes.
Fabrication and Mechanical Characteristics of Bulk Nickel/Carbon Nanotube Nanocomposites via the Electrical Explosion of Wire in Liquid and Spark Plasma Sintering Method
Minh, Thuyet-Nguyen ; Hong, Hai-Nguyen ; Kim, Won Joo ; Kim, Ho Yoon ; Kim, Jin-Chun ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 213~220
DOI : 10.4150/KPMI.2016.23.3.213
In this study, bulk nickel-carbon nanotube (CNT) nanocomposites are synthesized by a novel method which includes a combination of ultrasonication, electrical explosion of wire in liquid and spark plasma sintering. The mechanical characteristics of the bulk Ni-CNT composites synthesized with CNT contents of 0.7, 1, 3 and 5 wt.% are investigated. X-ray diffraction, optical microscopy and field emission scanning electron microscopy techniques are used to observe the different phases, morphologies and structures of the composite powders as well as the sintered samples. The obtained results reveal that the as-synthesized composite exhibits substantial enhancement in the microhardness and values more than 140 HV are observed. However an empirical reinforcement limit of 3 wt.% is determined for the CNT content, beyond which, there is no significant improvement in the mechanical properties.
Consolidation to Bulk Ceramic Bodies from Oyster Shell Powder
Cho, Kyeong-Sik ; Lee, Hyun-Kwuon ; Min, Jae Hong ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 221~227
DOI : 10.4150/KPMI.2016.23.3.221
Waste oyster shells create several serious problems; however, only some parts of them are being utilized currently. The ideal solution would be to convert the waste shells into a product that is both environmentally beneficial and economically viable. An experimental study is carried out to investigate the recycling possibilities for oyster shell waste. Bulk ceramic bodies are produced from the oyster shell powder in three sequential processes. First, the shell powder is calcined to form calcium oxide CaO, which is then slaked by a slaking reaction with water to produce calcium hydroxide
. Then, calcium hydroxide powder is formed by uniaxial pressing. Finally, the calcium hydroxide compact is reconverted to calcium carbonate via a carbonation reaction with carbon dioxide released from the shell powder bed during firing at
. The bulk body obtained from waste oyster shells could be utilized as a marine structural porous material.
Synthesis of Copper Nanoparticles by a Chemical Reduction Method
Choi, Min Woo ; Bae, Min Hwan ; Ahn, Jung-Ho ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 228~234
DOI : 10.4150/KPMI.2016.23.3.228
Copper nanoparticles attract much attention as substitutes of noble metals such as silver and can help reduce the manufacturing cost of electronic products due to their lower cost and good conductivity. In the present work, the chemical reduction is examined to optimize the synthesis of nano-sized copper particles from copper sulfate. Sodium borohydride and ascorbic acid are used as reducing and antioxidant agents, respectively. Polyethylene glycol (PEG) is used as a size-control and capping agent. An appropriate dose of PEG inhibits the abnormal growth of copper nanoparticles, maintaining chemical stability. The addition of ascorbic acid prevents the oxidation of nanoparticles during synthesis and storage. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate the size of the synthesized nanoparticles and the coordination between copper nanoparticles and PEG. For chemical reduction, copper nanoparticles less than 100 nm in size without oxidized layers are successfully obtained by the present method.
Fabrication of Ti Porous body with Improved Specific Surface Area by Synthesis of CNTs
Choi, Hye Rim ; Byun, Jong Min ; Suk, Myung-Jin ; Oh, Sung-Tag ; Kim, Young Do ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 235~239
DOI : 10.4150/KPMI.2016.23.3.235
This study is performed to fabricate a Ti porous body by freeze drying process using titanium hydride (
) powder and camphene. Then, the Ti porous body is employed to synthesize carbon nanotubes (CNTs) using thermal catalytic chemical vapor deposition (CCVD) with Fe catalyst and methane (
) gas to increase the specific surface area. The synthesized Ti porous body has
-sized macropores and
-sized micropores. The synthesized CNTs have random directions and are entangled with adjacent CNTs. The CNTs have a bamboo-like structure, and their average diameter is about 50 nm. The Fe nano-particles observed at the tip of the CNTs indicate that the tip growth model is applicable. The specific surface area of the CNT-coated Ti porous body is about 20 times larger than that of the raw Ti porous body. These CNT-coated Ti porous bodies are expected to be used as filters or catalyst supports.
The Effect of Oxide Compound on Electrical Resistivity and Oxidation Stability in High-temperature for Ferritic P/M Stainless Steel
Park, Jin-Woo ; Ko, Byung-Hyun ; Jung, Woo-young ; Park, Dong-Kyu ; Ahn, In-Shup ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 240~246
DOI : 10.4150/KPMI.2016.23.3.240
In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at
up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form
and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.
Analyses of Creep Properties of Ni-base Superalloy Powders as Cooling Rate after Solid Solution Heat Treatment
Jun, Chan ; Lee, Youngseon ; Bae, Byeong Beom ; Kim, Hong-Kyu ; Hong, Seong Suk ; Kim, Donghoon ; Yun, Jondo ; Yoon, Eun Yoo ;
Journal of Korean Powder Metallurgy Institute, volume 23, issue 3, 2016, Pages 247~253
DOI : 10.4150/KPMI.2016.23.3.247
In this study, solid solution heat treatment of consolidated nickel-based superalloy powders is carried out by hot isotactic pressing. The effects of the cooling rate of salt quenching, and air cooling on the microstructures and the mechanical properties of the specimens are analyzed. The specimen that is air cooled shows the formation of serrated grain boundaries due to their obstruction by the carbide particles. Moreover, the specimen that is salt quenched shows higher strength than the one that is air cooled due to the presence of fine and close-packed tertiary gamma prime phase. The tensile elongation at high temperatures improves due to the presence of grain boundary serrations in the specimen that is air cooled. On the contrary, the specimen that is salt quenched and consists of unserrated grain boundaries shows better creep properties than the air cooled specimen with the serrated grain boundaries, due to the negative creep phenomenon.