• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.3 s.234
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• pp.425-431
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• 2005

The efficiency of complex slurry preparation route for developing the high performance SiC matrix of $RS-SiC_{f}/SiC$ composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of molten silicon were prepared with various C/SiC complex slurries, which associated with both the sizes of starting SiC particles and the blending conditions of starting SiC and C particles. The characterization of Rs-SiC materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the process optimization is also discussed. The flexural strength of Rs-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.583-587
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• 1989

Various $\alpha$-silicon carbied and colloidal graphite particles were sintered at 155$0^{\circ}C$ in vacuum atmosphere by reaction bonding sintering method, and the physical properties and microstructural analysis of specimen were investigated. With decreasing particle size, sintered density and 3-point bending strength of materials were increased and 3.2${\mu}{\textrm}{m}$ specimen showed high density and strength, 3.05g/㎤, 40kg/$\textrm{mm}^2$, respectively. The results of X-ray diffractometer and optical micrographs analysis showed that graphite and silicon melt reacted to convert to fine $\beta$-SiC particle and the body was changed to dense material.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.228-234
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• 1989

Pressureless-sintering of SiC with additions of yttria and alumina was studied. SiC could be densified to about 97% of its theoretical density at 185$0^{\circ}C$ which is about 20$0^{\circ}C$ below the normal sintering temperature of SiC with boron and carbon. Yttria and alumina formed intergranular liquid phases at the sintering temperature and promoted densification by the liquid phase sintering mechanism. The microstructure of sintered specimens was equiaxed and the liquid phase appeared to wet and dissolve SiC grains. The fracture toughness was measured by indentation method and found to be 5.3MPa.m1/2. Processing flaws near the surface of specimens appeared to be the major fracture origin during 3-point bending tests.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.503-510
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• 2002

Silicon carbide candle filters for the pressurized fluidized bed combustion system were fabricated by extrusion process. Carbon black was added to control the porosity. Inorganic additives such as clay and calcium carbonate were added to exhibit appropriate strength. Silicon carbide layer with a finer pore size (mean pore diameter ~$10{\mu}m$) was coated on the silicon carbide support layer (mean pore diameter ~$47{\mu}m$, porosity ∼40%). After that, the filter was sintered at 1400${\circ}C$ in air. We evaluated the filtration performances of the filter at 500${\circ}C$ and $5kgf/cm^2$ of pressure. As a result, high separation efficiency, >99.999% was measured. It is expected that silicon carbide candle filter can be successfully used for the pressurized fluidized bed combustion system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.338-344
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• 2019

B₄C-SiC composites were fabricated using hot press sintering method without sintering additives at 1,900~2,000℃ under a pressure of 40 MPa. The crystal phase, relative density, microstructure, and mechanical properties of B₄C-SiC composites were evaluated. When B₄C and SiC were uniformly dispersed in the composite, grain growth was inhibited, and a sintered body with a fine and uniform microstructure, with improved mechanical properties, was fabricated. The relative density of B₄C-SiC composites sintered under 2,000℃ of temperature and 40 MPa of pressure was over 99.8 %, and the bending strength and Vicker's hardness at 50 wt% of B₄C were 645 MPa and 30.6 GPa, respectively.

• Composites Research
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• v.25 no.6
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• pp.172-177
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• 2012

For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed ${\alpha}$-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine ${\beta}$-SiC particle and the structure was changed to dense material. The amount of fine ${\beta}$-SiC particle was gradually increased as carbon content increase. According to mixed composite, it's mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.541-547
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• 2004

Addition of large particles restrains densification by small particles in mixed particle systems. In the present study, large SiC whiskers or particles were introduced into small particles for restraining densification and the mixtures were sintered using yttrium aluminum garnet (Y$_3$A1$\sub$5/O$\sub$12/, YAG) as a sintering additive. By controlling the content of large SiC whiskers or particles and the applied pressure during sintering, porous SiC ceramics, with a porosity ranging from 0.3% to 39%, were fabricated. Porosity increased with increasing the content of restraining materials. SiC whiskers were more effective than large SiC partcles for restraining densification. Permeability of the porous SiC ceramics increased with increasing the porosity. Flexural strength decreased with increasing porosity. A noticeable increase in strain to failure was observed in the porous ceramics with a porosity ranging from 18% to 39%.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.266-270
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• 2004

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine because it has excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing jiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at $1800^{\circ}C$ under 20MPa using $Al_2O_3,\;Y_2O_3\;and\;SiO_2$ as sintering additives in order to low sintering temperature and sintering pressure. The starting powder was high purity $\beta-SiC$ nano-powder with all average particle size of 30mm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, tire compositions of sintering additives are discussed.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.294-299
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• 2003

The efficiency of complex slurry preparation route for the development of high performance RS-SiCf/SiC composites has been investigated. The green bodies for RS-SiC and RS-SiCf/SiC composite materials prior to the infiltration of molten silicon were prepared with various C/SiC complex matrix slurries, which associated with both different sizes of starting SiC particles and blending ratios of starting SiC and carbon particles. The reinforcing materials in the composite system were uncoated and C coated Tyranno SA SiC fiber. The characterization of RS-SiC and RS-SiCf/SiC composite materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, process optimization methodology is discussed.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.413-419
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• 1998

${\beta}$-silicon carbides with yttrium aluminum garnet of 2,5,10 mol% were prepared by a liquid--phase sint-ering and the microstructural evolution and phase transformation were investigated during sintering as functions of liquid-phase amount and sintering time. The rate of grain growth decreases with the addition of the amount of yttrium aluminum garnet (YAG) in the SiC starting powder however the apparent density and the aspect ratio of grains in sintered body increase. The phase transformation from ${\beta}$-SiC to ${\alpha}$-SiC were dependent on the liquid-phase amount and sintering time.