• 한국세라믹학회지
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• 제53권1호
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• pp.99-104
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• 2016

High purity Si-C (99.999%) powder prepared by mechanical alloying was added to a commercial SiC powder as a sintering additive. Reaction bonded silicon carbide balls and jars with high purity (99.98%) were used for the mechanical alloying. As a result, the purity of the sintered Si-C was higher than 99.99%. When sintered at $2200^{\circ}C$ under 50 MPa pressure for 1 h, SiC containing 10 wt% of high purity Si-C showed a relative density of 95.3%, similar to the relative density of commercial SiC (95%). However, the relative density of SiC decreased to 90.6% without the additive when the applied pressure decreased to 40 MPa. In contrast, the relative density was nearly unaffected by the decrease of the pressure when using the Si-C additive. Therefore, the addition of Si-C powder promoted the densification of SiC above $2000^{\circ}C$ under 40 MPa pressure.

• 한국세라믹학회지
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• 제46권5호
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• pp.452-455
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• 2009

A cost-effective route to synthesize $\beta$-SiAlONs from Si mixtures by reaction bonding followed by post-sintering was investigated. Three different z values, 0.45, 0.92 and 1.87, in $Si_{6-z}Al_zO_zN_{8-z}$ without excess liquid phase were selected to elucidate the mechanism of SiAlON formation and densification. For RBSN (reaction-bonded silicon nitride) specimens prior to post-sintering, nitridation rates of more than 90% were achieved by multistep heating to $1400^{\circ}C$ in flowing 5%$H_2$/95%$N_2$; residual Si was not detected by XRD analysis. An increase in density was acquired with increasing z values in post-sintered specimens, and this tendency was explained by the presence of higher amounts of transient liquid phase at larger z values. Measured z values from the synthesized $\beta$-SiAlONs were similar to the values calculated for the starting compositions. Slight deviations in z values between measurements and calculations were rationalized by a reasonable application of the characteristics of the nitriding and post-sintering processes.

• 한국재료학회지
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• 제8권7호
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• pp.596-600
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• 1998

반응결합 알루미나(RBAO)-SiC 세라믹스를 AI금속분말/$AI_2O_3$/SiC 분말혼합체로부터 제조하였다. 하소알루미나와 용융알루미나를 알루미나 분말공급원으로 사용하였다. 출발원료는 단일구경(3mm)또는 혼합구경(3mm+5mm)의 $ZrO_2$볼로 어트리션 밀링 하였다. 정수압 성형한 시편을 $1100^{\circ}C$까지$ 1.5^{\circ}C$/mim로 1차소성한 다음,$ 1500^{\circ}C$~$1600^{\circ}C$까지 $5^{\circ}C$/mim으로 2차소성하였다. 용융알루미나와의 분말혼합체가 하소알루미나와의 분말혼합체보다 분쇄가 더욱 잘 되었다. 또한 단일구가 혼합구보다 분쇄에 더욱 효율적이었다. $AI_2O_3$ 형태에 따른 반응소결거동에는 별 차이가 없었다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
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• pp.26.1-26
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• 2002

• 한국주조공학회지
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• 제15권3호
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• pp.272-282
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• 1995

Iron-based metal matrix composites have been recently investigated for the use of inexpensive abrasion resistance material. This paper carried out to investigate the in-situ reaction effects on the microstructural characteristics and the formation mechanism of tungsten carbides in a white cast iron matrix. The specimens of Fe-3.2%C-2.8%Si alloy cast-bonded with tungsten wire were cast in the metal mold and isothermally heat treated at $950^{\circ}C$ up to 48 hours. The typical microstructure of heat treated specimens showed the reaction layer of WC at the interface of tungsten wire and the carbon depletion zone between the WC layer and the matrix. During the formation of WC layer, if the carbon supply is insufficient due to the decarburization of matrix or the isolation of matrix by cast-bonded W wires, the reaction layer develops coarse hexagonal crystalline WC. From the microstructural investigation, it was found that the volume of WC layer and the carbon depletion zone increased linearly with the isothermal heat treating time. This results supported that the formation rate of WC in the white cast iron matrix is controlled by the interfacial reaction with a constant reaction rate.

• 한국세라믹학회지
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• 제35권4호
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• pp.406-412
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• 1998

The reaction bonded alumina ceramics was prepared through the addition of each SiC and ZrO2 powder to the mixture of Al metal powder and Al2O3 The mono sized (3mm) and biodal sized (3mm+5mm) balls were used in attrition milling of Al and starting powders. The milling efficiency of both cases was compared by the analysis of particle size and X-ray diffraction. After the forming and sintering of each powder batchs the weight gains dimensional changes and densities were determined. The specimens were investigated by X-ray diffraction analysis and scanning electron microscope. Bimodal sized balls had better milling effect than single ball size in the milling of Al powder. However in the milling which ceramic powders mono sized the green body during the reaction sintering at 1$600^{\circ}C$ for 5 hour was about 10% The densities attained the values of 92-98% theoretical. The SiC added specimen that was milled with 3mm ball media had 96% theoretical density and dense microstructure.

• 한국세라믹학회지
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• 제26권4호
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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.

• 한국세라믹학회지
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• 제21권3호
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• pp.253-258
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• 1984

This paper deals with the reaction-bonded silicon nitride I terms of its microstructural development during nitrida-tion. Silicon powder compacts were reacted with nitrogen at 1185$^{\circ}C$ and 13$65^{\circ}C$ according to the nitriding schedule. Microstructures of nitrided specimens were examined by means of optical and scanning electron microscope to discuss the nitridation or microstructural development at initial and intermediat stage of nitridation. Reaction products were also analysed by X-ray diffraction method at each stage of nitridation. The results indicate that ho-mogeneous and uniform microstructure with find porosity can be obtained only under the reaction condition. such as slow and relatively constant reaction rate with time.

• 한국세라믹학회지
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• 제36권2호
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• pp.193-202
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• 1999

Al 분말과 AlN 분말에 SiC 휘스커와 소결조제를 첨가하여 습식혼합한 후 성형체를 제조하고 600~140$0^{\circ}C$의 온도에서 5시간 동안 질화반응을 진행시켰다. 반응소결체의 꺾임강도를 측정한 결과 질화율이 높아질수록, 그리고 SiC 휘스커의 첨가량이 많아질수록 증진되는 것을 확인할 수 있었다. Al과 AlN이 50:50으로 혼합된 시편을 140$0^{\circ}C$에서 5시간 동안 질화반응을 시킨 결과 97% 이상의 질화율과 2%미만의 수축율을 나타내었고, 상대밀도값은 78%이었다. 그리고 반응소결체의 최대 꺾임강도는 250 MPa이었다. 완전히 질화반응을 시켜 미반응 Al이 잔존하지 않는 시편들을 1$700^{\circ}C$, 180$0^{\circ}C$, 190$0^{\circ}C$의 온도에서 2시간 동안 재소결한 결과 수축은 6% 미만이었으며, 최고 86%의 상대밀도를 나타내었다. 180$0^{\circ}C$이상의 온도에서 2시간 동안 재소결한 결과 수축은 6%미만이었으며, 최고 86%의 상대밀도를 나타내었다. 180$0^{\circ}C$이상의 온도에서 재소결한 시편들의 경우 AlN과 SiC 휘스커가 고용체를 형성하여 SiC 휘스커 첨가에 의한 기계적 물성의 증진 효과는 거의 나타나지 않았다. 그리고 재소결한 시편의 최대 꺾임강도는 295 MPa이었다.

• 한국세라믹학회지
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• 제22권1호
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• pp.53-59
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• 1985

Experiments related to nitriding silicon with addition of $Si_3N_4$ have provided information on the effects of such inclusion on the phase relationships of Reaction Bonded Silicon Nitride. In the current work specimens containing 0-25wt% Si3N4 which have 55.5wt% $\alpha$ 4.5wt% $eta$, 40wt% amorphous phase were nitrided for 7-20 hours at 1300-135$0^{\circ}C$ The evaluation of nitridation was per-formed by means of $\alpha$-and $\beta$-phase contents determination in nitrided specimens, In order to observe nitrided region between silicon and silicon nitride scanning electron microscopy was used to study reacted region between silicon and silicon nitride particle. For this purpose semiconductor-grade silicon wafer single crystal was used as a silicon source. The incorporation of small amount of $Si_3N_4$ powder is contributed to enhancing the rate of formation of $\alpha$-phase.