• Korean Journal of Materials Research
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• v.25 no.5
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• pp.258-263
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• 2015

To fabricate porous SiC-Si composites for heating element applications, both SiC powders and Si powders were mixed and sintered together. The properties of the sintered SiC-Si body were investigated as a function of SiC particle size and/or Si particle contents from 10 wt% to 40 wt%, respectively. Porous SiC-Si composites were fabricated by Si bonded reaction at a sintering temperature of $1650^{\circ}C$ for 80 min. The microstructure and phase analysis of SiC-Si composites that depend on Si particle contents were characterized using scanning electron microscope and X-ray diffraction. The electrical resistivity of SiC-Si composites was also evaluated using a 4-point probe resistivity method. The electrical resistivity of the sintered SiC-Si body sharply decreased as the amount of Si addition increased. We found that the electrical resistivity of porous SiC-Si composites is closely related to the amount of Si added and at least 20 wt% Si are needed in order to apply the SiCSi composites to the heating element.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.1
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• pp.43-48
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• 2006

In this Part 2, the grain growth processes of $Al_2O_3$ ceramics is numerically simulated using Monte Carlo method (MCM) and finite element method (FEM) and the pore sizes are analyzed. As the green ceramics whose thermal conductivities in high temperatures are generally low are sintered by the plasma heat and are rapidly cooled, the grain growth of the sintered body in the center is different from that in the outer. Also, even in the same sintering temperature, the pore size differs according to the pressing pressure. In order to prove the difference, the temperature distribution of the sintered body was analyzed using the finite element method and then the grain growth process associated with pressing pressures and relative densities was simulated using Monte Carlo method.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.448-456
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• 1994

The reaction-sintered alumina and zirconia-alumina ceramics were fabricated from the Al/Al2O3 or Zl/ZrO2(Ca-PSZ) powder mixtures via the attrition milling. And the effects of the milling characteristics of used raw powders on reaction sintering were investigated. After attrition milling and isopressing at 400 MPa the Al/Al2O3 specimen was oxidated at 1200℃ for 8 hours followed by sintering at 1550℃ for 3 hours. Because mixed powders of flake-type Al with coarse alumina was much more effectively comminuted than the globular-type Al with coarse alumina powders, it's sintered body of more than 97% theoretical density was achived, but low contents of Al leads to relatively higher shrinkage of about 8%. And because coarse alumina particles was much more beneficial in cutting and reducing the ductile Al particles, using the coarse alumina powder was much more effective in reaction sintering. Fused Ca-PSZ powder was reaction sintered with Al at 1550℃ for 3 hours and low shrinkage ZrO2-Al2O3 composites were fabricated. But because Al/Ca-PSZ powder mixtures were not effectively milled the reaction sintering and densification was difficult. And the Ca ion in Ca-PSZ grains diffused into alumina grains during sintering so that the unstabilization of Ca-PSZ body was occured which gave the microcracks in the specimens.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.354-359
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• 2011

Silicon nitride ceramics were prepared by microwave gas phase reaction sintering. By this method higher density specimens were obtained for short time and at low temperature, compared than ones by conventional pressureless sintering, even though sintering behaviors showed same trend, the relative density of sintered body inverse-exponentially increases with sintering temperature and/or holding time. And grain size of ${\beta}$-phase of the microwave sintered body is bigger than one of the conventional pressureless sintered one. Also they showed good bending strengths and thermal shock resistances.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.472-476
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• 2004

The Fe-Ni compact bodies were fabricated using Fe-Ni mixed powders with 50 nm in diameter by injection molding process. The relationship between microstructure and material properties was characterized with respect to the volume ratio of powder/binder and sintering temperature with SEM and TEM. In the compact body having the volume percent ratio of 45(Fe-Ni) : 55(binder), which was sintered at $900^{\circ}C$ the values of relative density and hardness were low about 97.7% and 277.1 Hv, respectively. Using the composition of 50(Fe Ni) : 50(binder) and sintered at $900^{\circ}C$, the values of relative density and hardness were 98.5%, 294.4 Hv, respec-tively. The grain size of sintered bodies strongly depended on the sintering temperature. In both samples sintered at $600^{\circ}C$ and $900^{\circ}C$, the average grain sizes were about 150 nm and 500 nm in diameter, respectively.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.408-414
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• 2006

[ $MoSi_2$ ] alloys with Al, B or Nb were prepared by an advanced consolidation process that combined mechanical alloying with pulse discharge sintering (complex forming) to improve the mechanical properties. Their microstructure and mechanical properties were investigated. The $MoSi_2$ alloys fabricated by complex forming method showed very fine microstructure when compared with the sample sintered from commercial $MoSi_2$ powders. Alloys made from powders milled in Ar gas had fewer silica or alumina phases as compared to their counterparts sintered from powders milled in air. In densification of the sintered body, addition of B was more effective than Al or Nb. Both Victors hardness and tensile test indicated that the alloy fabricated by the complex forming method showed better properties than the sample sintered from commercial $MoSi_2$ powders. The Al added alloy sintered from the powders milled in air had the superior mechanical properties due to the suppression of $SiO_2$ and formation of fine $Al_2O_3$ particles.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.227-233
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• 1995

By using homestyle microwave oven, Al-Al2O3 powder mixture could be oxidized and sintered into Al2O3 body. The differences in powder characteristics among the differently processed raw materials affect the oxidation and sintering behaviours, and these effects were more pronounced in case of microwave oven than of conventional furnace. Al-Al2O3 powder mixture was oxidized and sintered within 2hrs, which could save both processing time and energy.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.75-76
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• 1998

Fly ash 70wt% contained green bodies were sintered by using a 2.45 Ghz microwave oven and their properties were investigated. Samples were sintered at 1,150$^{\circ}C$ and kept at that temperature up 50 minutes by 10 minutes intervals. Numerical analysis on the microwave heated system was carried out in order to figure out the heat transfer phenomena in the cavity.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.413-418
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• 1995

The (B.Si)C composite was prepared form the mixture of metal boron, silicon, and carbon powders in Ar atmosphere by Self-propagating High-temperature Synthesis Chemical Furnace. The characterization of synthesized power and sintered body were investigated. The microstructure of sintered body suggested that SiC boundary was made between B4C grains. The most excellent mechanical properties, the relative density of 95% oftheoretical value, 3 point flexural strength of 360MPa, and fracture toughness of 3.6MN/m3/2 could be obtained in 80wt% B4C-20 wt% SiC composite were obtained.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.235-242
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• 1987

This study was about to make zirconia ceramics with yttria, using spraying precipitation method for the purpose of powder control. The powder properties and the characterization of sintered body, were studied. As the results, 1. The synthesized powder had homogeneity of spherical shape, and average particle size was 2-3 um. 2. Crystallization temperature increased with Y2O3 content. 3. Apparent density of sintered body (fired above 1500$^{\circ}C$) was higher than 98% of theoretical value in 3 mol% Y2O3 content. 4. High KIC values(19kg/㎣/2) in 3 mol % Y2O3 content resulted from sintering density increasement.