• 한국세라믹학회지
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• 제48권5호
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• pp.360-367
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• 2011

Macroporous silicon carbide (SiC) ceramics were fabricated by powder processing and polymer processing using carbon-filled polysiloxane as a precursor. The effects of the starting SiC polytype, template type, and template content on porosity and flexural strength of macroporous SiC ceramics were investigated. The ${\beta}$-SiC powder as a starting material or a filler led to higher porosity than ${\alpha}$-SiC powder, owing to the impingement of growing ${\alpha}$-SiC grains, which were transformed from ${\beta}$-SiC during sintering. Typical flexural strength of powder-processed macroporous SiC ceramics fabricated from ${\alpha}$-SiC starting powder and polymer microbeads was 127 MPa at 29% porosity. In contrast, that of polymer-processed macroporous SiC ceramics fabricated from carbon-filled polysiloxane, ${\beta}$-SiC fillers, and hollow microspheres was 116MPa at 29% porosity. The combination of ${\alpha}$-SiC starting powder and a fairly large amount (10 wt%) of $Al_2O_3-Y_2O_3$ additives led to macroporous SiC ceramics with excellent flexural strength.

• 한국표면공학회지
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• 제29권1호
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• pp.26-35
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• 1996

The Ni-SiC composite plating was performed in a Watt nickel solution and the wear resistance of the composite layer was studied on a pin-on-flat type wear tester. The volume losses and friction coefficients were measured. It was found that the quantity of SiC powder in the composite layers was affected by SiC concentration, pH, temperature, and agitation speed in the Watt nickel solution. The hardness and wear resistance of the coatings increased with SiC content. The quantity of SiC powder in the coating from a nickel sulfamate solution is larger than that of the Watt nickel solution, because the amount of nickel ions absorbed on the SiC powder in the nickel sulfamate solution is greater than that in the Watt's solution.

• 열처리공학회지
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• 제16권5호
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• pp.260-266
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• 2003

In order to study the interfacial reaction between Nb thin sheet and Fe-C-(Si) alloy with different Chemical compositions, they were cast-bonded. The growth of carbide layer formed at the interface after isothermal heat treatment at 1173K, 1223K, 1273K and 1323K for various times was investigated. The carbide formed at the interface was NbC and the thickness of NbC layer was increased linearly in proportional to the heat treating time. Therefore, It was found that the growth of NbC layer was controlled by the interfacial reaction. The growth rate constant of NbC layer was slightly increased with increase of carbon content when the silicon content is similar in the cast irons. However, as silicon content increases with no great difference in carbon content, the growth of NbC layer was greatly retarded. The calculated activation energy for the growth of NbC layer was varied in the range of 447.4~549.3 kJ/moI with the compositions of cast irons.

• 한국표면공학회지
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• 제42권2호
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• pp.73-78
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• 2009

Quinary Ti-Al-Si-C-N films were successfully synthesized on SUS 304 substrates and Si wafers by a hybrid coating system combining an arc ion plating technique and a DC reactive magnetron sputtering technique. In this work, the effect of Si content on the microstructure and mechanical properties of Ti-Al-C-N films were systematically investigated. It was revealed that the microstructure of Ti-Al-Si-C-N coatings changed from a columnar to a nano-composite by the Si addition. Due to the nanocomposite microstructure of Ti-Al-Si-C-N coatings, the microhardness of The Ti-Al-Si-C-N coatings significantly increased up to 56 GPa. In addition the average friction coefficients of Ti-Al-Si-C-N coatings were remarkably decreased with Si addition. Therefore, Ti-Al-Si-C-N coatings can be applicable as next-generation hard-coating materials due to their improved hybrid mechanical properties.

• 한국자기학회지
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• 제5권5호
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• pp.864-873
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• 1995

비정질 $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ 리본을 DSC 곡선상의 최초 발열반응 전 후의 온도인 $500^{\circ}C$ 및 $552^{\circ}C$에서 열처리하여 열처리 시간에 따른 초미립상의 생성 과정을 뫼스바우어 분광법으로 분석하였다. 열처리된 시료에 생성된 결정상은 대부분 $DO_{3}Fe-Si$이었으며, $t-Fe_{3}B$로 추정되는 강자 성상도 소량 확인되었으며, 비정질상도 잔류하여 공존함을 확인하였다. $DO_{3}Fe-Si$내의 Si 조성 즉, Si/(Fe+Si)는 $500^{\circ}C$ 60분 열처리에서 0.218 이었으며, $552^{\circ}C$ 10분 열처리에서 0.222이었다. 열처리 시간이 120분이 될 때까지 이들 두 값은 감소한 후 계속된 열처리에서 0.210으로 거의 일정하게 유지되었다. 열처리 시간 에 따른 Si 조성의 변화는 초미세자기장과 이성질체이동의 변화를 유발시킨 것으로 분석할 수 있었다. 즉, Fe-Si의 평균초미세자기장의 증가와 평균이성질체이동의 감소는 Si 조성의 증가에 기인됨을 알 수 있었다. 잔류비정질의 체적분율은 초기에 급격히 감소하여 $500^{\circ}C$와 $552^{\circ}C$ 둘 다의 열처리 온도에서 120분 이후 거의 일정해 진다. 120분 이후 Fe-Si와 잔류비정질의 체적분율의 미소한 변화에도 불구하고 잔류비 정질의 평균초미세자기장의 현저한 감소는 잔류비정질내의 Nb와 B 원소의 양의 증가에 기인된다. 결정질의 체적분율은 예측과는 달리 $500^{\circ}C$에서 180분 열처리될 경우 81 %, $552^{\circ}C$에서 960분 열처리될 경우 77 % 이었다.

• 한국세라믹학회지
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• 제30권3호
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• pp.243-249
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• 1993

Coated type Al2O3-SiC composite powders were synthesized by surface modification method. Transformation temperature to $\alpha$-Al2O3 of Al2O3 monolith was 115$0^{\circ}C$ whereas increased to 1200, 1250, 130$0^{\circ}C$ with increment of SiC content to 5, 15, 25wt%. Transformation temperature to $\alpha$-Al2O3 was lowered by $\alpha$-Al2O3 seeding. FTIR data analysis and electron micrographs showed that Al2O3 particles were effectively coated on SiC particles.

• 한국세라믹학회지
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• 제30권2호
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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.

• 한국세라믹학회지
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• 제25권5호
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• pp.502-508
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• 1988

The $\alpha$ to $\beta$ phase transformation of $\alpha$-Si3N4 whisker and related microstructural changes have been investigated. When only $\alpha$-Si3N4 whisker was heat treated in the range 1650~175$0^{\circ}C$, the $\alpha$ to $\beta$ phase transformation occured. In this case, it eas suggested that the oxygen content in $\alpha$-Si3N4 whisker affected the transformation behavior. Although $\alpha$-Si3N4 whisker with Si was heat treated under the same condition, however, the variation of $\beta$- fraction had a similar tendency with heat treating time. Therfore, it was considered that the oxygen content in $\alpha$-Si3N4 whisker affected the transformation behavior dominently rather than the content of added Si. The added $\beta$ phase did not affect the transformation behaviro of $\alpha$-Si3N4 whisker.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.139-142
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• 2000

The SiCp/AC8A composites were fabricated by the pressureless metal infiltration process successfully. The effect of additional Mg, which were mixed with SiC particles to promote interfacial wetting between the reinforcement and matrix alloy, and particle size on the mechanical properties was investigated. By increasing the additional Mg content the hardness of SiCp/AC8A composites was increased due to the hard reaction products, but the bending strength was decreased by the excess reaction of Mg and high porosity level when the additional Mg content is over 7%. The Hardness and bending strength was increased by decreasing the size of SiC particle.

• 한국세라믹학회지
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• 제43권7호
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• pp.427-432
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• 2006

The preparation of SiC powder by SHS in the system of $SiO_2-Mg-C$ was investigated in this study. The effects of various processing parameters such as the initial pressure of inert gas in reactor, the content of Mg and C in mixture and the size of $SiO_2$ particles on the synthesis of SiC by SHS methode were investigated. The minimum initial pressure of inert gas in reactor for SHS reaction in this system was 5 atm, and as the pressure increased, and the concentration of unreacted Mg decreased. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure SiC was $SiO_2+2.5Mg+1.2C$. SiC powder synthesized in this condition had a mixture of ${\alpha}-SiC\;and\;{\beta}-SiC$ with an irregular shape and the particle size of $0.5{\sim}0.8{\mu}m$.