• Journal of Powder Materials
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• v.15 no.3
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• pp.214-220
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• 2008

In this study, consolidation behavior and hardness of commercially available molybdenum powder were investigated. In order to analyze compaction response of the powders, the elastoplastic constitutive equation based on the yield function by Shima and Oyane was applied to predict the compact density under uniaxial pressure from 100MPa to 700MPa. The compacts were sintered at $1400-1600^{\circ}C$ for 20-60 min. The sintered density and grain size of molybdenum were increased with increasing the compacting pressure and processing temperature and time. The constitutive equation, proposed by Kwon and Kim, was applied to simulate the creep densification rate and grain growth of molybdenum powder compacts. The calculated results were compared with experimental data for the powders. The effects of the porosity and grain size on the hardness of the specimens were explained based on the modified plasticity theory of porous material and Hall-Petch type equation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.44.2-44.2
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• 2009

BCP powder was synthesized using microwave hydrothermal process with mixed calcium hydroxide and phosphoric acid. After using replica method, porous BCP scaffold was fabricated. PU (Poly Urethane) was used as the fugitive skeleton to fabricate the porous scaffold. BCP powder was mixed in PVB (Polyvinyl butyral) and ethanol solution and then applied to the PU foam by dip coating. After several times of coating and the subsequent oven drying the coated PU foam was burnt out at $750^{\circ}C$ at air to remove the PU. The resulting networked porous composites were sintered at $1250^{\circ}C$, $1300^{\circ}C$ and $1350^{\circ}C$ in microwave furnace for 30 minutes. Material properties of the porous bodies like compressive strength and porosity were investigated. Detailed microstructure of the BCP porous body was characterized by SEM and XRD and TEM techniques. In our experiments, the relationship between mechanical property and viscosity of powder, sintering temperature was investigated.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.390-395
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• 2011

The objective of our study was to produce an imitation bone material consisting of hydroxyapatite with a compact and spongy structure. This study shows the ideal content of $SiO_2$ and the sintering temperature to produce imitation bone that has the mechanical properties of natural bone. On the basis of our determination of the ideal conditions, a compact part was produced and its mechanical properties were tested. A compact part made of 0.5 wt% $SiO_2$ and sintered at $1350^{\circ}C$ showed excellent mechanical properties. The bioactivity of the compact part under this condition was tested, and it was found to be bioactive. The porous part was produced by controlling the powder size, and the dual structure was manufactured by combining the compact and porous parts. A water permeability test confirmed that the dual structure had an interconnected pore structure. Therefore, this dual-body structure is feasible for use in the creation of implants.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.326-334
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• 2010

Porous and net-shaped tantalum powder for a capacitor was formulated in a SHS (self-propagating high-temperature synthesis) process. However, this powder, which has weak strength among its particles and low flow ability, cannot be used for a capacitor. Therefore, this powder was sintered in a high-vacuum furnace to increase agglomeration to improve the flow ability, bonding strength among the particles, and shrinkage during pellet sintering. Finally, it was deoxidated with 2 wt% Mg powder to remove the increased surface oxygen that arose during the sintering process. The final product was analyzed in terms of its chemical and physical properties and was compared with a commercial powder used by a capacitor manufacturer.

• Journal of Powder Materials
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• v.19 no.6
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• pp.446-450
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• 2012

In order to fabricate the porous Mo with controlled pore characteristics, unique processing by using $MoO_3$ powder as the source and camphene as the sublimable material is introduced. Camphene-based 15 vol% $MoO_3$ slurries, prepared by milling at $50^{\circ}C$ with a small amount of dispersant, were frozen at $-25^{\circ}C$. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green body was hydrogen-reduced at $750^{\circ}C$, and sintered at $1000-1100^{\circ}C$ for 1 h. After heat treatment in hydrogen atmosphere, $MoO_3$ powders were completely converted to metallic W without any reaction phases. The sintered samples showed large pores with the size of about $150{\mu}m$ which were aligned parallel to the camphene growth direction. Also, the internal wall of large pores and near bottom part of specimen had relatively small pores due to the difference in the camphene growth rate during freezing process. The size of small pores was decreased with increase in sintering temperature, while that of large pores was unchanged. The results are strongly suggested that the porous metal with required pore characteristics can be successfully fabricated by freeze-drying process using metal oxide powders.

• Korean Journal of Materials Research
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• v.17 no.6
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• pp.318-322
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• 2007

Porous ${\beta}-tricalcium$ phosphate $({\beta}-TCP)$ bioceramic was fabricated by pressureless sintering using commercial HAp and different volume percentages of PMMA powders (30-60 vol.%). The range of spherical pore size was about $200-250\;{\mu}m$ in diameter. By increasing the PMMA content, the number of pores and their morphology were dramatically changed as well as decreased the material properties. In case of using 60 vol.% PMMA content, network-type pores were found, due to the necking of the PMMA powders. The values of relative density, elastic modulus, bending strength and hardness of the 60 vol.% PMMA content sample, sintered at $1500^{\circ}C$, were about 46%, 22.2 GPa, 5MPa and 182 Hv respectively. Human osteoblast-like MG-63 cells and osteoclast-like Raw 264.7 cells were well grown and fully covered all of the porous ${\beta}-TCP$ bodies sintered at $1500^{\circ}C$.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.61-66
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• 2016

In order to fabricate porous mullite ceramics with controlled pore structure and improved mechanical strength, a freeze casting route has been processed using camphene mixed with tertiary-butyl alcohol (TBA) and coal fly ash/alumina as the solvent and the ceramic material, respectively. After sintering, the solidification characteristics of camphene and TBA solvent were evident in the pore morphology, i.e., dendritic and straight pore channels formed along the solidification directions of camphene and TBA ice, respectively, after sublimation. Also, the presence of microcracks was observed in the bodies sintered at $1500^{\circ}C$, mainly due to the difference in solidification volume change between camphene and TBA. The compressive strength of the sintered bodies was found generally to be dependent, in an inverse manner, on the porosity, which was mainly determined by the processing conditions. After sintering at $1300{\sim}1500^{\circ}C$ with 30~50 wt% solid loading, the resulting mullite ceramics showed porosity and compressive strength values in ranges of 83.8~43.1% and 3.7~206.8 MPa, respectively.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1301-1302
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• 2008

In this study, the fracture strength for fracture mechanism porous calcium phosphate made from sintered with ${\beta}$-tricalcium phosphate obtained by wet precipitation procedure is analyzed using finite element method and experiment measurement. First, three $3{\times}3{\times}3mm^3$ and $5{\times}5{\times}5mm^3$ specimens are prepared and tomographic images of one $5{\times}5{\times}5mm^3$ specimen are obtained by micro focus X-ray CT. The compression tests using the specimens are carried out to measure the elastic modulus and fracture strength to analyze the fracture mechanism of porous calcium phosphate specimen. The tomographic images are reconstructed by 3D reconstruction program. The finite elements are directly built up in the reconstructed specimen. The numerical simulation for the compression tests is performed using the element. The mechanism of calcium phosphate of simulation are obtained by the compression tests using there cylindric specimen of height 19.5 mm and diameter 10 mm. From the results, the applicability of porous calcium phosphate is evaluated to care fracture and vacant bone of a patient as the reinforcement material.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1078-1079
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• 2006

The paper presents the possibilities of obtaining new composite materials based on sintered porous ceramics with particles and fibre of $Al_2O_3$ infiltrated by aluminum alloy. The EN AC - AlSi12 alloy features the matrix material, whereas the RF50AX-301 preform, of Saffil Automotive, was used as the reinforcement. Examinations of ceramics preforms permeability were made. Metallographic examination of composite materials made on light microscope and in scanning electron microscope show that aluminum alloys fill micropores in the matrix. New composite materials show twice higher value of hardness in comparison with matrix. Results indicate that it is possible to infiltrate porous ceramic with liquid aluminum alloy to obtain new composite materials were advantageous properties of each component are connected.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.467-471
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• 2018

Diatomite powder, a naturally occurring porous raw material, was used to make ceramic materials with porosity and high strength. The sintering behavior of the diatomite powder at various sintering temperatures suggests that diatomite monoliths with a high porosity and strength can be prepared at $1100^{\circ}C$. The compressive strength of the sintered diatomite monoliths increased as the sintering temperature increased, and the molding pressure of 2 MPa and the binder of 18.6 wt.% were excellent. When the sintering temperature rises, the diatomite powder is melted, and its pores gradually disappear. SEM images show that strengthening begins with the formation of inter-particle bonds at a low sintering temperature.