• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.195-200
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• 2007

We fabricated thermally-evaporated 10 nm-Ni/70 w-Poly-Si/200 $nm-SiO_2/Si$ and $10nm-Ni_{0.5}Co_{0.5}/70$ nm-Poly-Si/200 $nm-SiO_2/Si$ structures to investigate the microstructure of nickel monosilicide at the elevated temperatures required fur annealing. Silicides underwent rapid anneal at the temperatures of $600{\sim}1100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process formed on top of the polycrystalline silicon substrate mimicking the gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope and an Auger depth profile scope were employed for the determination of cross sectional microstructure and thickness. 20nm thick nickel cobalt composite silicides on polycrystalline silicon showed low resistance up to $900^{\circ}C$, while the conventional nickle silicide showed low resistance below $900^{\circ}C$. Through TEM analysis, we confirmed that the 70nm-thick nickel cobalt composite silicide showed a unique silicon-silicide mixing at the high silicidation temperature of $1000^{\circ}C$. We identified $Ni_3Si_2,\;CoSi_2$ phase at $700^{\circ}C$ using an X-ray diffractometer. Auger depth profile analysis also supports the presence of this mixed microstructure. Our result implies that our newly proposed NiCo composite silicide from NiCo alloy films process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Journal of Powder Materials
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• v.11 no.3
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• pp.259-264
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• 2004

Aluminum based metal matrix composite reinforced with SiC particles was fabricated by the powder-in sheath rolling method. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1mm was used as a sheath. Mixture of aluminum powder and SiC particles of which volume content was varied from 5 to 20vol.% was filled in the tube by tap filling and then rolled to 75% reduction at ambient temperature. The rolled specimen was sintered at 56$0^{\circ}C$ for 0.5hr. The tensile strength of the (SiC)$_{p}$/Al composite increased with the volume content of SiC particles, and at 20vol.% it reached a maximum of 100㎫ which is 1.6 times higher than unreinforced material. The elongation decreased with the volume content of $Al_{2}$O$_{3}$ particles. The mechanical properties of the (SiC)$_{p}$/Al composite fabricated by the powder-in sheath rolling is compared with that of (Al$_{2}$O$_{3}$)$_{p}$/Al composite by the same process.ess.

• Journal of Powder Materials
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• v.8 no.3
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• pp.179-185
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• 2001

Through the observation of wear scar of two ceramic materials, microstructural wear mechanisms was investigated. As for the $Al_2O_3$-5 vol% SiC nanocomposite, the grain boundary fracture was suppressed by the presence of SiC nano-particles. The intragranular SiC particles have inhibited the extension of plastic deformation through the whole grain. Part of plastic deformation was accommodated around SiC particles, which made a cavity at the interface between SiC and matrix alumina. On the other hand, gas-pressure sintered silicon nitride showed extensive grain boundary fracture due to the thermal fatigue. The lamination of wear scar was initiated by the dissolution of grain boundary phase. These two extreme cases showed the importance of microstructures in wear behavior.

• The Korean Journal of Ceramics
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• v.2 no.1
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• pp.39-42
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• 1996

${\alpha}-SiC$ powder with or without the addition of 0.1 wt% of large ${\alpha}-SiC$ partices(seeds) was pressureless-sintered at $1950^{\circ}C$ for 0.5, 2, and 4 h using $Y_3Al_5 O_{12}$ (yttrium aluminum garnet, YAG) as a sintering aid. The materials without seeds had an equiaxed grain struture. In contrast, the materials with seeds sintered for 2 and 4 h had a duplex microstructure with large elongated grains and amall equiaxed grains. Addition of large ${\alpha}-SiC$ seeds into ${\alpha}-SiC$ accelerated the grain growth of some ${\alpha}-SiC$ grains during sintering and resulted in the increased fracture toughness of the sintered materials. The fracture toughnesses of materials with or without seeds sintered for 4 h were 6.6 and $5.2 MPa \;m^{12}$, respectively.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.233-239
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• 2000

Sr0.9Bi2+xTa2O9(x=0, 0.1, 0.2, 0.3) thin films on IrO2/SiO2/Si or Pt/Ti/SiO2/Si substrate were prepared by spin coating method using SBT stock solutions synthesized by MOD process. SBT thin films on IrO2 transformed to layered perovskite phase at $700^{\circ}C$, but showed low breakdown voltage due to their porous microstructure. The smaple of Sr0.9Bi2+xTa2O9 composition showed the best dielectric and electrical properties. When the sample of the same composition was annealed at 80$0^{\circ}C$, the dielectric and electric properties were improved due to the grian growth and dense surface. the remanent polarization values(2Pr) at $\pm$3 V for IrO2 and Pt electrodes were 10.5, 7.15$\mu$C/$\textrm{cm}^2$, respectively. The SBT thin film with IrO2 electrode showed the lower coercive field. The leakage current density and breakdown voltage of SBT thin films on IrO2 were higher than those on Pt.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.89.2-89.2
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• 2010

고체산화물 연료전지는 $800{\sim}1000^{\circ}C$인 고온에서 작동하므로 적용되는 밀봉재의 요구조건은 매우 중요하다. 본 연구에서는 SOFC 밀봉재로서 $SiO_2-B_2O_3-RO$계 결정화 유리를 선정하였으며 작동온도 부근에서 결정화를 유도하여 고온점성유동을 제어하고자 하였다. 따라서 $SiO_2-B_2O_3-RO$계에 RO인 CaO, SrO, BaO, MgO를 상호 치환하였을 때 결정상의 생성, 생성온도, 생성결정의 종류가 sealing 특성에 어떠한 영향을 주는가를 검토하였다. 결정화유리를 $800^{\circ}C$로 유지하였을 때 생성되는 주 결정상은 Calsium silicate, Strontium silicate, Barium silicate, Magnesium silicate이였으며 Strontium silicate 의 생성속도가 가장 빨랐으며 결정상은 불산으로 에칭하여 SEM으로 관찰하였다. Barium silicate를 유도한 결정화 유리가 $800^{\circ}C$에서 1000시간 유지하였을 경우 가장 내화학성이 우수하며 강도값도 154MPa로 가장 높았다. 또한 부분 결정화를 통해 $800^{\circ}C$ 점성유동이 제어됨을 고온현미경을 통해 관찰하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.233-239
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• 1998

SiC thin films were deposited by chemical vapor deposition method using tetramethylsilane (TMS) and hexamethyldisilane (HMDS). The chamber pressure during the deposition was kept at about 1 torr. Precursor was transported to the reaction chamber by $H_2$gas and SiC deposition was carried out at the reaction temperature of $1200^{\circ}C$. Si-wafer masked with tantalum and MgO single crystal covered with platinum and molybdenum were used as substrates. The selectivity of SiC deposition was observed by comparing the microstructure between metal (Ta, Pt, and Mo) surfaces and substrate surfaces (Si and MgO). The deposited films were identified as the $\beta-SiC$ phase by X-ray diffraction pattern. Also, the deposition -behavior of SiC on each surface was investigated by the scanning electron microscope analysis.

• Journal of the Korean institute of surface engineering
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• v.35 no.2
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• pp.113-121
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• 2002

We have investigated insulating properties of $SiO_2$ interlayer for the thin film strain gauge, which were prepared by RF magnetron sputtering method in various deposition conditions, such as Ar pressure, gas flow rates and sputtering gases. SEM, AFM and FT-IR techniques were used to analyze its structures and composition. As the Ar pressure and the flow rate increased, the insulating interlayer showed low insulating resistance due to its porous structure and defects. Oxygen deficiency in $SiO_2$ was decreased as fabricated by hydrogen reactive sputtering. We could enhance the surface mobility of sputtered adatoms by using Ar/$H_2$ sputtering gas and obtain a good surface roughness and insulating property. The optimum insulating resistance of 9.22 G$\Omega$ was obtained in Ar/30% $H_2$ mixed gas, flow rate 10sccm, and 1mTorr.

• Journal of Conservation Science
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• v.8 no.1 s.11
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• pp.10-15
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• 1999

The chemical compositions and microstructure of the punch'ong excavated from Bokwangri, Kangnung were investigated by the scanning electron microscope (SEM) with an energy dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD), and dilatometer. The compositions of body were $SiO_2(73-78\%),\;Al_2O_3(13-16\%)$, $RO{\cdot}R_2O(4-5\%,\;R=Ca,\;Mg,\;Na,\;K),\;R_xO_y(3-6\%,\;R=Fe,Ti)$ in weight ratio, which were higher silica and flux $(RO{\cdot}R_2O)$ but lower alumina. Owing to the high content$(21-30\%)$ of calcium oxide the glaze is considered lime type. Firing temperature range for the ceramic was presumed to about $1150^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.191-193
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• 2004

The composites were fabricated, respectively, using 61vol.% SiC-39vol.% $TiB_2$ and using 61vol.% SiC-39vol.% $ZrB_2$ powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ 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. The result of phase analysis of composites by XRD revealed SiC(6H, 3C), $TiB_2$, $ZrB_2$ and $YAG(Al_5Y_3O_{12})$ crystal phase on the SiC-$TiB_2$, and SiC-$ZrB_2$ composites. The ${\beta}\;{\alpha}$-SiC phase transformation was occurred on the $SiC-TiB_2$, $SiC-ZrB_2$ composites. The relative density, the flexural strength and Young's modulus showed respectively value of 98.57%, 226.06Mpa and $86.37{\times}10^3Mpa$ in SiC-$ZrB_2$ composites.