• 한국세라믹학회지
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• 제23권1호
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• pp.67-73
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• 1986

SiC and $SiC-Si_3N_4$ powder were synthesized via the carbiding and carbiding-nitriding reaction of Jecheon quartz respectively using graphite as a reducing agent. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbiding-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $H_2$ atmosphere. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbidint-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $N_2-H_2$ atmosphere. The ratio of $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ content in a produced composite could be controlled by adjusting the reaction time and gaseous mixture.

• 연구논문집
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• 통권23호
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• pp.165-171
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• 1993

$Si_3N_4/Sic$. nano-composites were fabricated by hot-pressing, gas pressure sintering. The composites contained up to 50 wt. % of SiC. The mechanical properties such as strength, toughness, and hardness of the composite are compared each other. The flexural strength of the composites was improved significantly by introducing fine SiC particles into $Si_3N_4$ matrix, while the fracture toughness was not improved. The increase in flexural strength is attributed to the formation of uniformly elongated $\beta -Si_3N_4$ grains as well as the reduction of grain size.

• 한국세라믹학회지
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• 제36권10호
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• pp.1007-1015
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• 1999

The Si3N4 composites reinforced with carbon-coated SiC whiskers were fabricated by hot-pressing at 180$0^{\circ}C$ for 2 hours to examine the effects of carbon-coated whiskers on the mechanical properties of SiC whisker reinforced Si3N4 composites. The flexural strength of the Si3N4 composites and Si3N4 monolith respectively. The weak interfacial bond between carbon-coated SiC whiskers and Si3N4 matrix which enhances the crack deflection and whisker pull-out could contribute to the improvement of mechanical properties of the composites.

• Corrosion Science and Technology
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• 제6권1호
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• pp.24-28
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• 2007

Alumina coated SiC whiskers were prepared by homogeneous precipitation of aluminum sulfate. The Si3N4 composites reinforced with coated SiC whiskers were fabricated by hot-pressing at $1800^{\circ}C$ for 2 h under an $N_{2}$ atmosphere of 0.1 MPa to examine the effects of coated whiskers on the mechanical properties of SiC whisker reinforced $Si_{3}N_{4}$ composite. By the addition of alumina coated SiC whiskers instead of as received ones, the fracture toughness of composite was about 6.7 $MPam^{1/2}$ which was slightly lower than as received SiC whisker reinforced composite. This result seems to be caused by the fact that the crack deflection and whisker pull-out were decreased. Thus, alumina coated SiC whiskers were considered to form relatively strong interface bond with $Si_{3}N_{4}$ matrix.

• 한국세라믹학회지
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• 제37권3호
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• pp.280-287
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• 2000

Adsorption behavior and amount of phenolic resin followed silica (SiO2) formation onto silicon nitride(Si3N4) surface were investigated using electrokinetic sonic amplitude (ESA) technique and with UV spectrometer, to fabricate Si3N4/SiC nano-composite based on reaction between SiO2 formed and phenolic resin absorbed onto Si3N4 particle. The amount of SiO2 formed and carbon from phenolic resin absorbed onto Si3N4 surface were calculated quantitatively to adjust the reaction between SiO2 and phenolic resin, resulting in no residual SiO2 and carbon. As a result, pre-heated tempeature for optimized reaction was below 25$0^{\circ}C$, in which there was no residual SiO2 and carbon.

• 한국재료학회지
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• 제6권4호
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• pp.428-435
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• 1996

초미립 SiC분말과 SiC platelet을 2차성으로 Si3N4에 첨가하여 SiC/Si3N4 하이브리드 복합체를 가압소결로 제조한 후 2차상의 영향을 조사한 결과핫프레스법을 이용한 경우 SiC platelet은 Si3N4 기지 복합채의 치밀화를 저해하지 않고 초미립의 SiC 첨가는 Si3N4의 입성장을 효과적으로 억제하여 미세한 $\beta$-Si3N4의 grain을 형성함을 관찰하였다. 초미립 SiC첨가를 통한 복합체의 강도 증진은 상대적으로 $\beta$-Si3N4입자의 미세화에 의한 인성의 저하를 유도하나 SiC platelet을 첨가하여 급격한 강도 저하 없이 높은 인성을 갖는 하이브리드 복합체를 제조할 수 있었으며 SiC/Si3N4 하이브리드 복합체의 인성증진은 elongated $\beta$-Si3N4와 platelet SiC의 debonding에 의한 grain pull-out 영향임을 알 수 있었다.

• 연구논문집
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• 통권26호
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• pp.103-112
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• 1996

$Al_2O_3/SiC$ Hybrid-Composite이 일반적인 분말공정에 의하여 제조되었다. 소결시 $\gamma-Al_2O_3에서 $\alpha-Al_2O_3$로의 전이에 seed역할을 하는 $\alpha-Al_2O_3의 첨가는 균일한 미세구조를 발달시켜 강도의 증진을 가져왔다. nano size의 SiC의 첨가는 $Al_2O_3$의 소결성과 입성장에 영향을 미쳐 파괴강도의 증진을 가져왔다. $Al_2O_3/SiC$ nano-Composite에 SiC plates의 첨가는 파괴강도의 감소를 가져왔지만, 상대적으로 파괴인성은 증진되었다. SiC plates에 nitride (BN, $Si_3N_4$ 코팅을 할 경우 crack deflection을 더욱 유발하여 파괴인성이 증진되었다.

• 한국정밀공학회지
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• 제18권9호
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• pp.82-88
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• 2001

In order to fulfil the requirements of the various performance profiles of ceramic cutting tools, six different SiC-based ceramics have been fabricated by hot-pressing (SiC--${Si}_3 {N}_4$composites) or by hot-pressing and subsequent annealing (monolithic SiC and SiC-TiC composites). Correlation between the annealing time and the corresponding microstructure and the mechanical properties of resulting ceramics have been investigated. The grain size of both ${Si}_3 {N}_4$and SiC in SiC-${Si}_3 {N}_4$composites increased with the annealing time. Monolithic SiC has the highest hardness, SiC-TiC composite the highest toughness, and the SiC-${Si}_3 {N}_4$composite the highest strength among the ceramics investigated. The hardness of SiC-${Si}_3 {N}_4$composites was relatively independent of the grain size, but dependent on the sintered density. The cutting performance of the newly developed SiC-based ceramic cutting tools will be described in Part 2 of this paper.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.166-168
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• 2006

$Si_3N_4/SiC$ composite ceramics was sintered in order to investigate their bending strength behavior after crack healing. $Y_2O_$ and $TiO_2$ power was added as sintering additives to enhance it's sintering property. A three-point bending specimen was cut out from sintered plates. About $100\;{\mu}m$ semi-circular surface cracks were made on the center of the tension surface of the three-point bending specimen using Vickers indenter. After the crack-healing processing from $500^{\circ}C$ to $1300^{\circ}C$, for 1 h, in air, the bending strength behavior of these crack-healed specimen coated with $SiO_2$ colloidal were determined systematically at room temperature. $Si_3N_4/SiC$ ceramics using additive powder ($Y_2O_3+TiO_2$) was superior to that of additive powder $Y_2O_3$. The additive powder $TiO_2$ exerted influence at growth of $Si_3N_4$. The optimum crack healing conditions coated $SiO_2$ colloidal were $1000^{\circ}C$ at $Si_3N_4/SiC$ using additive powder ($Y_2O_3+TiO_2$), and $1300^{\circ}C$ at $Si_3N_4/SiC$ using additive powder $Y_2O_3$.

• 한국세라믹학회지
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• 제34권4호
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• pp.406-412
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• 1997

Al2O3/SiC hybrid-composite has been fabricated by the conventional powder process. The addition of $\alpha$-Al2O3 as seed particles in the transformation of ${\gamma}$-Al2O3 to $\alpha$-Al2O3 provided a homogeneity of the microstructure. The grain growth of Al2O3 are significantly surpressed by the addition of nano-size SiC particles. Dislocation were produced due to the difference of thermal expansion coefficient between Al2O3 and SiC and piled up on SiC particles in Al2O3 matrix, resulting in transgranular fracture. The high fracture strength of the composite was contributed to the grain refinement and the transgranular fracture mode. The addition of SiC platelets to Al2O3/SiC nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC platelets with nitrides such as BN and Si3N4 enhanced fracture toughness much more than non-coated SiC platelets by enhancing crack deflection.