• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1289-1290
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• 2007

The composites were fabricated 61Vo.% ${\beta}$-SiC and 39Vol.% $TiB_2$ powders with the liquid forming additives of 12wt% $Al_{2}O_{3}+Y_{2}O_{3}$ as a sintering aid by pressure or pressureless annealing at $1650^{\circ}C$ for 4 hours. The present study investigated the influence of annealed sintering on the microstructure and mechanical of SiC-$TiB_2$ electroconductmive ceramic composites. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and In Situ YAG($Al_{5}Y_{3}O_{12}$). The relative density, the flexural strength, the Young's modulus showed the highest value of 86.69[%], 136.43[MPa], 52.82[GPa] for pressure annealed SiC-$TiB_2$ ceramic composites.

• 한국재료학회지
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• 제15권3호
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• pp.177-182
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• 2005

Large amounts of the waste SiC sludge containing small amounts of Si and organic lubricant were produced during the wire cutting process of the single silicon crystal ingots. The waste SiC sludge was purified by the washing process and the purified SiC powders were used to fabricate continuously porous $SiC-Si_3N_4$ composites using a fibrous monolithic process, in which carbon, $6wt\%\;Y_2O_3-2\;wt\%\;A1_2O_3$ and ethylene vinyl acetate were added as a pore-forming agent, sintering additives, and binder, respectively. In the burning-out process, carbon was fully removed and continuously porous $SiC-Si_3N_4$ composites were successfully fabricated. The green bodies containing SiC, Si particles and sintering additives were nitrided at $1410^{\circ}C$ in a flowing $N_2+10\%\;H_2$ gas mixture. Continuously porous composites were combined with SiC, ${\alpha}Si_3N_4,\;\beta-Si_3N_4$ and a few $\%$ of Fe phases. The pore size of the 2nd and the 3rd passed $SiC-Si_3N_4$ composites was $260\;{\mu}m$ and $35\;{\mu}m$ in diameter, respectively.

• 한국재료학회지
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• 제9권9호
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• pp.937-942
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• 1999

Fe계 합금의 적층결함에너지를 감소시키는 것으로 알려진 Mn이 Fe-20Cr-1C-Si 경면처리 합금의 변형유기 상변태거동과 상온 및 고온 마모저항성에 미치는 영향에 대하여 조사하였다. 15ksi의 접촉응력에 대하여 0~25wt.% Mn을 첨가한 시편은 모두 상온에서 마모손실량이 적은 우수한 마모저항성을 보였는데 Mn 첨가량이 5wt.% 이하인 시편의 경우 마모표면에서 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 반면 15wt.% 이상 Mn을 첨가한 시편에서는 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 발생하는 것으로 나타났다. 25$0^{\circ}C$까지 고온 마모시험결과 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 5wt.% 이하 Mn 첨가시편은 Mn 첨가량이 증가할수록 마모손실량이 증가하는 것으로 보아 Mn 첨가는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 있어서 고온 마모저항성을 저하시키는 것으로 생각되며 이는 Mn이 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태의 M(sub)d 온도를 감소시키기 때문으로 생각된다. 반면에 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 일어난 15wt.% 이상 Mn 첨가 시편의 경우 Mn 첨가량 증가에 따른 고온 마모손실량의 차이가 없는 것으로 보아 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 비해 온도의 존성이 적은 것으로 생각된다.

• 자원환경지질
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• 제42권3호
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• pp.177-193
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• 2009

삼광광상은 선캠브리아기 경기육괴의 화강편마암내에 발달된 단열대(NE, NW)를 따라 충진한 8개의 괴상맥으로 구성된 중열수 석영맥광상이다. 이 광상의 광화작용은 여러번의 단열작용에 의해 형성된 두시기의 석영+방해석시기(광화I시기)와 방해석시기(광화II시기)로 구성된다. 광화I시기의 열수작용에 의한 변질작용은 견운모화, 녹니석화, 탄산염화, 황철석화, 규화, 및 점토화작용등이 관찰되며 견운모대는 석영맥과 접촉한 부분에서 녹니석대는 석영맥으로부터 멀어짐에 따라 관찰된다. 견운모대의 모암변질광물은 대부분이 견운모 및 석영이며 일부 일라이트, 탄산염광물, 녹니석으로 구성된다. 녹니석대의 모암변질광물은 주로 녹니석, 석영과 소량 견운모, 탄산염광물 및 녹염석으로 구성된다. 견운모의 Fe/(Fe+Mg) 값은 0.45${\sim}$0.50(0.48$\pm$0.02)이며 백운모-펜자이트족에 해당되고 녹니석의 Fe/(Fe+Mg) 값은 0.74${\sim}$0.81(0.77$\pm$0.03)이고 대부분 브런스비자이트에 해당된다. 견운모와 녹니석에 대한 $Al_{IV}$-FE/(FE+Mg)의 다이어그램은 변질시 같은 광종의 견운모와 녹니석의 형성온도를 나타내는 지시자로써 유용하다. 이것은 계산된 녹니석 단종의 활동도가 $a3(Fe_5Al_2Si_3O_{10}(OH)_6$=0.0275${\sim}$0.0413, $a2(Mg_5Al_2Si_3O_{10}(OH)_6$=1.18E-10${\sim}$7.79E-7, $a1(Mg_6Si_4O_{10}(OH)_6$=4.92E-10${\sim}$9.29E-7로서 삼광광상의 녹니석은 iron-rich 녹니석으로 비교적 고온 (T>450$^{\circ}C$에서 모암과 평형상태에서 온도가 감소함에 따라 형성되었음을 알 수 있다. 모암변질시 ${\alpha}Na^+$, ${\alpha}K^+$, ${\alpha}Ca^{2+}$ 및 ${\alpha}Mg^{2+}$는 각각 ${\alpha}Na^+$=0.0476($400^{\circ}C$), 0.0863($350^{\circ}C$), ${\alpha}K^+$=0.0154($400^{\circ}C$), 0.0231($350^{\circ}C$), ${\alpha}Ca^{2+}$=2.42E-11($400^{\circ}C$), 7.07E-10($350^{\circ}C$), ${\alpha}Mg^{2+}$=1.59E-12($400^{\circ}C$), 1.77E-11($350^{\circ}C$)이며 열수용액의 pH는 5.4${\sim}$6.4($400^{\circ}C$), 5.3${\sim}$5.7($350^{\circ}C$)로서 모암변질시 열수용액는 약산성이었음을 알 수 있다. 모암변질시 이득원소(부화원소)는 $TiO_2$, $Fe_2O_3(T)$,CaO, MnO, MgO, As, Ag, Cu, Zn, Ni, Co, W, V, Br, Cs, Rb, Sc, Bi, Nb, Sb, Se, Sn 및 Lu 등이며 특히 대부분의 광상에서 Ag, As, Zn, Sc, Sb, S,$CO_2$ 등의 원소가 현저하게 증가하므로 중열수 및 천열수 금-은광상의 탐사에 지시원소로서 활용될 수 있을 것이다.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.400-403
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• 1999

The mechanical and electrical properties of hot-pressed and annelaed $\beta$-SiC+39vol.% $ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_2O_3+Y_2O_3$(6:4 wt%). In this microstructures, no reactions and elongated $\alpha$-SiC grains with equiaxed $ZrB_2$ grains were observed between $\beta$-SiC and $ZrB_2$. The properties of the $\beta$-SiC+39vol.%$ZrB_2$ composites with 4wt% $Al_2O_3+Y_2O_3$ at R.T. are as follows: fracture toughness is 6.37 MPa.m1/2, electical resistivity is $1.51\times10^{-4}\Omega \cdot\textrm{cm}$ and the relative density is 98.6% of the theoretical density. The fracture toughness of the $\beta$-SiC+39 vol.% $ZrB_2$ composites were weakly decreased with increasing amount of $Al_2O_3+Y_2O_3$ additives. Internal stresses due to the difference of $\beta$-SiC and $ZrB_2$ thermal expansion coefficient and elastic modulus mismatch appeared to contribute to fracture toughening in $\beta$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composites.

• 한국결정성장학회지
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• 제8권2호
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• pp.324-331
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• 1998

2, 5, 10 mol% YAG(yttrium aluminum garnet) 분말을 액상 소결조제로 $\alpha$상 탄화규소 분말에 첨가한 후 $1850^{\circ}C$에서 소결시간을 달리하여 소결체를 제조한 다음, 소결시 일어나는 미세구조 변화를 첨가된 액상량과 소결시간의 변화에 대하여 고찰하였다. 각 조성중 2시간 소결한 시편에서 가장 높은 밀도를 나타냈으며, 소결시간이 길수록 액상의 기화로 인하여 중량감소량이 점차 증가하였다. 또한 첨가된 YAG 액상량이 증가할 수록 상대밀도(apparent density)와 중량감소량은 증가하였으나 입성장속도는 감소하였다. 액상량이 적은 시편에서는 소결시간이 길수록 일부 6H상의 탄화규소 입자가 4H상 탄화규소 입자로 상전이 되었으며, 이로 인하여 막대상 입자들이 일부 존재하였다.

• 대한금속재료학회지
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• 제48권2호
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• pp.133-140
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• 2010

10 nm thick Ni layers were deposited on 200 nm $SiO_2/Si$ substrates using an e-beam evaporator. Then, 60 nm or 20 nm thick ${\alpha}$-Si:H layers were grown at low temperature (<$200^{\circ}C$) by a Catalytic-CVD. NiSi layers were already formed instantaneously during Cat-CVD process regardless of the thickness of the $\alpha$-Si. The resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness with the additional rapid thermal annealing up to $500^{\circ}C$ were examined using a four point probe, HRXRD, FE-SEM, TEM, AES, and SPM, respectively. The sheet resistance of the NiSi layer was 12${\Omega}$/□ regardless of the thickness of the ${\alpha}$-Si and kept stable even after the additional annealing process. The thickness of the NiSi layer was 30 nm with excellent uniformity and the surface roughness was maintained under 2 nm after the annealing. Accordingly, our result implies that the low temperature Cat-CVD process with proposed films stack sequence may have more advantages than the conventional CVD process for nano scale NiSi applications.

• 대한금속재료학회지
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• 제49권2호
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• pp.121-127
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• 2011

The mechanical properties of the various heat treatment conditions on Ti-15Mo-3Nb-3Al-0.2Si alloy plates were examined. XRD patterns from the surface of Ti-15Mo-3Nb-3Al-0.2Si were analyzed as a solution-treated Ti alloy has the single-phase ${\beta}$ structure whereas the aged Ti alloys have the ${\beta}$ matrix embedded with ${\alpha}$ needles. High strength (~1500 MPa) with decent ductility (7%) was obtained by the Ti alloy double aged at $300^{\circ}C$ and $520^{\circ}C$ for 8 hours each. The double-aged alloy exhibits the finer structure than the single-aged alloy at $300^{\circ}C$ for 8 hours because of the higher nucleation rate of ${\alpha}$ needles at an initial low aging temperature ($320^{\circ}C$). TEM observation revealed that the fine nanostructure with ${\alpha}$ needles in the ${\beta}$ matrix ensured the excellent mechanical properties in the double aged Ti-15Mo-3Nb-3Al-0.2Si alloy. In the solution treated alloy, the yield drop, stress-serrations and the ductility minimum typically associated with dynamic strain aging can be attributed to the dynamic interaction between dislocations and oxygen atoms. The yield drop and the stress serration were not observed in aged samples because the geometrically introduced dislocations due to phase precipitates suppressed the dynamic strain aging.

• 한국세라믹학회지
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• 제25권4호
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• pp.415-423
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• 1988

Mixtures of carbon and silica (about 0.46${\mu}{\textrm}{m}$) which was synthesized by the hydrolysis of ethyl silicate, the molar ratio of silica/carbon was fixed as 1/10(weight ratio : 1/2), were nitrided in the temperature range 135$0^{\circ}C$~150$0^{\circ}C$. The phse of the product Si3N4 was $\alpha$ phase and the morphology was hexagnoal prism and the nitridation reaction was completed in 5 hrs at 150$0^{\circ}C$ or 7hrs at 145$0^{\circ}C$. The reaction rate above 150$0^{\circ}C$ was diffusion-controlled, following Jander equation. Activation energy Q was derived from the Arrhenius plot and the value was about 101kcal/mol. Axis ratio of Lattice constants(c/a) was 0.726 and unit volume was $\AA$3, the larger the molar ratio of carbon/Alkoxide was, the smaller the particle size of $\alpha$Si3N4 was.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1303-1304
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• 2007

The composites were fabricated, respectively, using 61[vol.%]SiC-39[vol.%]$TiB_2$ and using 61[vol.%]SiC-39[vol.%]$ZrB_2$ powders with the liquid forming additives of 12[wt%] $Al_{2}O_{3}+Y_{2}O_{3}$ by hot pressing annealing at $1650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. ${\beta}{\rightarrow}{\alpha}$-SiC phase transformation was occurred on the SiC-$TiB_2$ and SiC-$ZrB_2$ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 226.06[Mpa] and 86.38[Gpa] in SiC-$ZrB_2$ composite at room temperature respectively. The electrical resistivity showed the lowest value of $7.96{\times}10^{-4}[{\Omega}{\cdot}cm]$ for SiC-$ZrB_2$ composite at $25[^{\circ}C]$. The electrical resistivity of the SiC-$TiB_2$ and SiC-$ZrB_2$ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$. The resistance temperature coefficient of composite showed the value of $6.88{\times}10^{-3}/[^{\circ}C]$ and $3.57{\times}10^{-3}/[^{\circ}C]$ for SiC-$ZrB_2$ and SiC-$TiB_2$ composite in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$.