• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.25-28
• /
• 2006

This paper dealt with the LPS process for the development of high performance SiC materials, based on the detailed analysis of their microstructure and mechanical properties. The submicron SiC powder was used for the fabrication of LPS-SiC materials. A mixture of $Al_2O_3$ and $Y_2O_3$ particles was also used as a sintering additive in the LPS process. LPS-SiC materials were fabricated at different temperatures, using various additive composition ratio ($Al_2O_3/Y_2O_3$). The total amount of additive materials ($Al_2O_3+Y_2O_3$) was fixed as 10 wt%. The characterization Of LPS-SiC materials was investigated by means of SEM, XRD and three point bending test. The LPS-SiC material represented a relative density of about 98 % and a flexural strength of about 800MPa, when it was fabricated at the temperature of $1820^{\circ}C$ and the additive compositional ratio of 1.5.

• Journal of the Korean Ceramic Society
• /
• v.50 no.6
• /
• pp.410-415
• /
• 2013

$ZrB_2$-SiC ceramics are fabricated via hot pressing with different ratios of submicron or nano-sized SiC in a $ZrB_2$-20 vol%SiC system, in order to examine the effect of the SiC size ratio on the microstructures and physical properties, such as thermal conductivity, hardness, and flexural strength, of $ZrB_2$-SiC ceramics. Five different $ZrB_2$-SiC ceramics ($ZrB_2$-20 vol%[(1-x)SiC + xnanoSiC] where x = 0.0, 0.2, 0.5, 0.8, 1.0) are prepared in this study. The mean SiC particle sizes in the sintered bodies are highly dependent on the ratio of nano-sized SiC. The thermal conductivities of the $ZrB_2$-SiC ceramics increase with the ratio of nano-sized SiC, which is consistent with the percolation behavior. In addition, the $ZrB_2$-SiC ceramics with smaller mean SiC particle sizes exhibit enhanced mechanical properties, such as hardness and flexural strength, which can be explained using the Hall-Petch relation.

• Journal of the Korean Vacuum Society
• /
• v.9 no.2
• /
• pp.99-101
• /
• 2000

The fabrication of the submicron size hole has been interesting due to the potential application of the near field optical sensor or liquid metal ion source. The 2 micron size dot array was photolithographically patterned. After formation of the V-groove shape by anisotropic KOH etching, dry oxidation at $1000^{\circ}C$ for 600 minutes was followed. In this procedure, the orientation dependent oxide growth was performed to have an etch-mask for dry etching. The reactive ion etching by the inductively coupled plasma (ICP) system was performed in order to etch ~90 nm $SiO_2$ layer at the bottom of the V-groove and to etch the Si at the bottom. The negative ion energy would enhance the anisotropic etching by the $Cl_2$ gas. After etching, the remaining thickness of the oxide on the Si(111) surface was measured to be ~130 nm by scanning electron microscopy. The etched Si aperture can be used for NSOM sensor.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.05a
• /
• pp.211-212
• /
• 2012

ZnO submicron particles were grown on Au-catalyzed Si substrate by a vapor phase transport (VPT) growth process under different mixture gas ratio at growth temperature of $900^{\circ}C$. The structural and optical properties of the ZnO submicron particles were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL). The ZnO submicron particles could be clustered with the $O_2/Ar$ mixture gas ratio(%) higher than 10%, and it was mainly determined by the gas ambient. Particularly, when the $O_2/Ar$ mixture gas ratio was 30%, it was observed the ZnO submicron particles with diameters in the range of 125 to 500 nm and the narrowest full width at half maximum (FWHM) of XRD and PL spectra with $0.121^{\circ}$ and 92 meV, respectively. It was found that the structural and optical properties of the ZnO submicron particles were improved with increasing the $O_2/Ar$ mixture gas ratio through the XRD and PL spectra.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.234-238
• /
• 2008

The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-$SiC_f$/SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of $Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$/SiC composites were fabricated with hot press under the sintering temperature and applied pressure of $1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$/SiC composites.

• Journal of Powder Materials
• /
• v.19 no.5
• /
• pp.379-384
• /
• 2012

This paper reports the microstructures and thermal conductivities of $ZrB_2$-SiC composite ceramics with size and amount of SiC. We fabricated sintered bodies of $ZrB_2$-x vol.% SiC (x=10, 20, 30) with submicron and nanosized SiC densified by spark plasma sintering. Microstructure retained the initial powder size of especially SiC, except the agglomeration of nanosized SiC. For sintered bodies, thermal conductivities were examined. The observed thermal conductivity values are 40~60 W/mK, which is slightly lower than the reported values. The relation between microstructural parameter and thermal conductivity was also discussed.

• Journal of the Korean Ceramic Society
• /
• v.28 no.7
• /
• pp.561-567
• /
• 1991

Submicron ${\alpha}-SiC$ powder with $Al_2O_3$ addition was hot-pressed under the controlled heating and pressurizing schedule. $SiO_2$ layer on ${\alpha}-SiC$ powder was effective for the sintering of ${\alpha}-SiC$ powder when $Al_2O_3$ was used as an additive. Applying of pressure under the controlled schedule accelerated the rearrangment of SiC grains, yielding 98% of theoretical density of SiC even at $1900^{\circ}C$. Flexural strength of the specimen containing 2 wt% $Al_2O_3$ was increased as increasing the hot-pressing temperature up to $2050^{\circ}C$ and maximum value was 800 MPa, while the flexural strength of the specimen containing 10 wt% $Al_2O_3$ was decreased as increasing the hot-pressing temperature above $2000^{\circ}C$ due to the formation of continuous grain boundary phase. Fracture toughness of the specimens was in the range of $3.5~4.5\;MNm^{-3/2}$ regardless of the amount of $Al_2O_3$ addition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.288-291
• /
• 2002

Application of metal silicides such as TiSi$_2$ and CoSi$_2$ as contacts and gate electrodes are being studied. However, TiSi$_2$ due to the linewidth-dependance, and CoSi$_2$ due to the excessive Si consumption during silicidation cannot be applied to the deep-submicron MOSFET device. NiSi shows no such problems and can be formed at the low temperature. But, NiSi shows thermal instability. In this investigation, NiSi was formed with a Ti-capping layer to improve the thermal stability. Ni and Ti films were deposited by the thermal evaporator. The samples were then annealed in the N$_2$ ambient at 300-800$^{\circ}C$ in a RTA (rapid thermal annealing) system. Four point probe, FESEM, and AES were used to study the thermal properties of Ti-capped NiSi layers. The Ti-capped NiSi was stable up to 700$^{\circ}C$ for 100 sec. RTA, while the uncapped NiSi layers showed high sheet resistance after 600$^{\circ}C$. The AES results revealed that the Ni diffusion further into the Si substrate was retarded by the capping layer, resulting in the suppression of agglomeration of NiSi films.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.328-328
• /
• 2011

Wetting phenomena have been heavily studied for industrial and academic researches especially tuning the wettability between hydrophilicity and hydrophobicity. Wicking through the surface texture is shown on superhydrophilic surface while rolling (or dewetting) on the patterns of superhydrophobic surface. These wetting phenomena are known to be affected by surface wettability determined with physical surface patterns as well as chemical composition of surface layer. In this research, we introduce a method to control the wettability of a thin C-SiOx film from hydrophobic to hydrophilic using a mixture gas of HMDSO/$O_2$ by plasma polymerization with rf-CVD (radio frequency-Chemical Vapor Deposition). Wettability was finely controlled by changing the ratio of HMDSO/$O_2$. Hydrophilicity increased as the ratio decreased, while hydrophobicity was enhanced by the ratio. Moreover, fine control from superhydrophilicity to superhydrophobicity was achieved by C-SiOx coating on the Si wafer with prepatterns of submicron-sized pillar array formed by $CF_4$ plasma etching.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.3
• /
• pp.28-33
• /
• 2011

The thermal shock properties of SiC materials were investigated for high temperature applications. In particular, the effect of thermal shock temperature on the flexural strength of SiC materials was evaluated, in conjunction with a detailed analysis of their microstructures. The efficiency of a nondestructive technique using ultrasonic waves was also examined for the characterization of SiC materials suffering from a cyclic thermal shock history. SiC materials were fabricated by a liquid phase sintering process (LPS) associated with hot pressing, using a commercial submicron SiC powder. In the materials, a complex mixture of $Al_2O_3$ and $Y_2O_3$ powders was used as a sintering additive for the densification of the microstructure. Both the microstructure and mechanical properties of the sintered SiC materials were investigated using SEM, XRD, and a three point bending test. The SiC materials had a high density of about 3.12 Mg/m3 and an excellent flexural strength of about 700 MPa, accompanying the creation of a secondary phase in the microstructure. The SiC materials exhibited a rapid propagation of cracks with an increase in the thermal shock temperature. The flexural strength of the SiC materials was greatly decreased at thermal shock temperatures higher than $700^{\circ}C$, due to the creation of microcracks and their propagation. In addition, the SiC materials had a clear tendency for a variation in the attenuation coefficient in ultrasonic waves with an increase in thermal shock cycles.