• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1261-1265
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• 1999

Effect of SiC particle size of the densification of Al2O3-SiC composite during pressureless sintering was investigated. Two types of SiC powders having average particle size of 0.15${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$ were used. Densification rate of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was slower than that of the specimen containg 3${\mu}{\textrm}{m}$ SiC particles. Although the relative density of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was below 90% of theoretical density after sintering at 155$0^{\circ}C$ the complete closure of open pores occurred. Therefore full densification could be obtained by subsequent HIP. On the other hand in the specimen containing 3${\mu}{\textrm}{m}$ SiC particles the complete closed pore was observed at 95% of theoretical density. Such a fast pore closure in the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles is likely to occur as a result of dense reaction layer formation on the specimen surface which is attributed to the high reactivity of small size particles with sintering atmosphere.

• The Korean Journal of Ceramics
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• v.1 no.3
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• pp.147-151
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• 1995

Porous composite of $Al_2O_3$ and AIN based mullite and SiC can be prepared by alumium reaction synthesis and atmosphere controllied sintering in order to improve the durability of a gas filter body. The porous $Al_2O_3$-AIN-mullite, which has a strength of 168 kg/$\textrm{cm}^2$ and porosity of 51.59%, could be obtained by stmospheric firing at $1600^{\circ}C$ and the porous $Al_2O_3$-AIN-SiC with a porosity of 33% and strength of 977 kg/$\textrm{cm}^2$, could also be prepared. The average pore size has been changed from 0.2$\mu\textrm{m}$ in a reduction atmosphere and to 2$\mu\textrm{m}$ in an air atmosphere, respectively.

• Korean Journal of Materials Research
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• v.6 no.10
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• pp.1043.1-1048
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• 1996

알루미나 매트릭스 복합재료를 AIZnMg(7075)-합금의 직접적인 용융산화를 통하여 제조하였다. 충전재료는 17$\mu\textrm{m}$ 크기의 모서리가 둥근 연마재용 SiC 입자를 사용하였다. 산화촉진재 SiO2를 사용한 경우와 사용하지 않은 경우를 비교하였다. 매트릭스 형성 매카니즘과 반응거동을 온도와 SiO2사용량을 중심으로 연구하였으며, 얻어진 AI2O3/SiC/금속 복합재료의 미세구조를 관찰하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.29-33
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• 2001

In the present study, AZ91Mg/$\textrm{Al}_2\textrm{O}_3$ short fiber+SiC particulates hybrid metal matrix composites(MMCs) were fabricated by squeeze casting method. Different particulate sizes of 45, 29 and $9\mu\textrm{m}$ were hybridized with 5% volume fraction to investigate the effect of SiC particulates size on microstructure, mechanical and thermal properties such as hardness, flexural strength, wear resistance and thermal expansion. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements. Some aggregation of SiC particulates caused by particle pushing was observed especially in the hybrid composites containing in fine particulates($9\mu\textrm{m}$). The hardness and flexural strength were improved by decreasing particulates size, whereas wear resistance improved by increasing particulates size because of large particulates restricting matrix wear from contacted stress. Regardless of particulates size, thermal expansion of composites was the same. This may be because the content of particulates was in all cases 5 volume fraction.1

• Korean Journal of Materials Research
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• v.9 no.8
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• pp.817-824
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• 1999

The $Al_2$$O_3$-SiC composite powder was prepared by Self-propagating High-Temperature Synthesis(SHS) process using $SiO_2$Al and C powders as raw material. The effects of the molar ratio in raw material, compaction pressure, initial temperature of reactants on the products and combustion process were studied. Self-propagating high temperature synthesis of $SiO_2$/Al/C system should be preheated above $400^{\circ}C$ owing to the low combustion temperature. As the result of the combustion reaction, the purity of final product became better than that of reactants. In this system, the optimum molar ratio of $SiO_2$:Al:C was 3.0:4.0:6.0. The free carbon was removed by roasting at $650^{\circ}C$ for 30min. In this study, pressureless sintering was very dffective both for controlling the disintegration of specimen with powder bed and for obtaining dense sintered-body at $1700^{\circ}C$. The sintered-body produced with hot-pressing was about 98% of the theoretical relative density.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.359-367
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• 2000

Particulate composites of Al2O3/SiC, Al2O3/ZrO2 and Al2O3/ZrO2/SiC have been fabricated to investigate their R-curve behaviors and toughening mechanisms. Al2O3 containing 30 vol% SiC particles of 3${\mu}{\textrm}{m}$ showed rising R-curve behavior owing to the strong crack bridging by SiC particles. The fracture toughness reached 9.1 MPa {{{{ SQRT {m} }} at the crack length of 1000${\mu}{\textrm}{m}$. On the other hand, ZrO2-toughened Al2O3 had a high flat R-curve since it rose steeply in the short crack region due to the well known transformation toughening. For Al2O3/ZrO2/SiC composites, the R-curve behavior was similar to that of Al2O3/SiC but with slightly higher toughness. The SiC particles in this composite decreased the amount of transformable tetragonal phase to reduce the effect of transformation toughening by 50%. It was also found that the fracture toughness of this composite with two different toughening mechanisms was markedly lower than that estimated by the simple addition of two contributions.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.125-130
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• 2004

The effect of SiC particle size on the microstructures and mechanical properties of A1$_2$O$_3$-SiC composite was investigated. Two types of SiC powders having average particle sizes of 0.15 ${\mu}{\textrm}{m}$ and 3 ${\mu}{\textrm}{m}$ were used. The grain growth in the specimen containing 0.15 ${\mu}{\textrm}{m}$ SiC was effectively inhibited due to the fine SiC particles. However, after the formation of some abnormal grains, fast and exaggerated grain growth occurred which led to the microstructure of large grains with irregular shape. Fracture strength decreased due to the abnormal large grains. On the other hand, for specimen containing 3 ${\mu}{\textrm}{m}$ SiC showed normal grain growth behavior from initial sintering stage. Large SiC particles, however, effectively inhibited exaggerated grain growth after nucleation of a few abnormal grains. As a consequence, microstructure consisted of homogeneous elongated grains. In the A1$_2$O$_3$-2.5SiC(0.15 ${\mu}{\textrm}{m}$)-2.5SIC(3 ${\mu}{\textrm}{m}$) composite fabricated by mixing the two types of SiC powder, abnormal grain growth occurred. However, the good fracture strength was maintained regardless of microstructural changes in this specimen.

• Composites Research
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• v.16 no.1
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• pp.1-12
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• 2003

This study developed SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites for electronic packaging to which reinforcements were added with the volume fractions of 49%, 56% and 63% by the squeeze casting method. 0.8 wt. % of the inorganic binder as well as the A1$_2$O$_3$ fiber and SiC Particles with the volume fraction of 1:10 were added to the composites, which were produced in the newly designed mold. For the produced SiC/Al composites, the CTEs (coefficients of thermal expansion) were measured from 30 to 300 and compared with the FEM numerical simulation to analyze the temperature dependent properties. The experiment showed the CTEs of SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites that were intermediate values of those of Rule of Mixture and Turner's Model. The CTEs were close to Turner's Model in the room temperature and approached the Rule of Mixture as the temperature increases. These properties analyzed from the difference of the average stress acting between the matrix and the reinforcements proposed in this study.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.123-130
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• 1993

Dispersed type Al2O3-SiC composite powders were synthesized from Al-isopropoxide (Al(i-OC3H7)3) and Si(OC2H5)4 precursors by hydrolysis of mixed alkoxides and carbothermal reaction method. The characteristics of the synthesized (dispersed type) Al2O3-SiC composite powders were investigated using XRD, SEM, TEM, BET and particle size analyzer. Carbothermal reaction to produce Al2O3-SiC composite was completed in 10h at 135$0^{\circ}C$ on 3~4㎤/s (0.21~0.28cm/s) of H2 flow rate and about 1/1 of carbon/oxides(=SiO2＋Al2O3) molar ratio. The synthesized powders were observed to have the mean particle size range of 0.4~1.26${\mu}{\textrm}{m}$ and showed finer particle size with increasing SiC content.

• Composites Research
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• v.16 no.3
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• pp.75-84
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• 2003

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/A12O3/Al and Saffil/SiC/Al hybrid metal matrix composites fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, $\textrm{Al}_2\textrm{O}_3$ particles and SiC particles on the wear behavior of the composites were investigated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction(COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffi1/$\textrm{Al}_2\textrm{O}_3$/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.