• Journal of the Korean Ceramic Society
• /
• v.35 no.12
• /
• pp.1336-1336
• /
• 1998

A twt -step carbothermal reduction scheme has been employed for the synthesis of SiC whiskers in an Ar or a H2 atmosphere via vapor-solid two-stage and vapor-liquid-solid growth mechanism respectively. It has been shown that the whisker growth proceed through the following reaction mechanism in an Ar at-mosphere : SiO2(S)+C(s)-SiO(v)+CO(v) SiO(v)3CO(v)=SiC(s)whisker+2CO2(v) 2C(s)+2CO2(v)=4CO(v) the third reaction appears to be the rate-controlling reaction since the overall reaction rates are dominated by the carbon which is participated in this reaction. The whisker growth proceeded through the following reaction mechaism in a H2 atmosphere : SiO2(s)+C(s)=SiO(v)+CO(v) 2C(s)+4H2(v)=2CH4(v) SiO(v)+2CH4(v)=SiC(s)whisker+CO(v)+4H2(v) The first reaction appears to be the rate-controlling reaction since the overall reaction rates are enhanced byincreasing the SiO vapor generation rate.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.396-400
• /
• 2003

A new synthesis process for nano laminating Ti$_3$SiC$_2$ has been developed using TiCx (x=0.67) and Si powder as starting materials by a reaction hot pressing. Bulk Ti$_3$SiC$_2$ was fabricated using a green body consisting of TiCx and Si by a hot pressing under the pressures of 25 MPa at 1420-1550 $^{\circ}C$ for 90 min. The synthesized Ti$_3$SiC$_2$ was consisting of only TiCx and Ti$_3$SiC$_2$. The relative density of sintered bulk Ti$_3$SiC$_2$ was increased as the hot pressing temperature was increased, which was mainly due to the increase in TiCx contents in synthesized Ti$_3$SiC$_2$. The synthesized Ti$_3$SiC$_2$ bulk was consisted of nano sized lamella structure of 20-100 nm in thickness. It was found that TiCx particles in Ti$_3$SiC$_2$ would increase the 3-point bending strength of synthesized Ti$_3$SiC$_2$ bulk. The maximum 3-P. bending strength of synthesized Ti$_3$SiC$_2$ bulk was more than 800 MPa. The Vickers hardness of synthesized Ti$_3$SiC$_2$bulk was as low as 5 Gpa, which was decreased with the indentation load. The quasi-plastic deformation behaviors were observed around indentation mark on Ti$_3$SiC$_2$.

• Journal of the Korean Ceramic Society
• /
• v.53 no.1
• /
• pp.87-92
• /
• 2016

Due to its stability at high temperature and its layered structure, $Ti_3SiC_2$ MAX phase was considered to the interphase of $SiC_f/SiC$ composite. In this study, $Ti_3SiC_2$ MAX phase powder was deposited on SiC fiber via the electrophoretic deposition (EPD) method. The Zeta potential of the $Ti_3SiC_2$ suspension with and without polyethyleneimine as a dispersant was measured to determine the conditions of the EPD experiments. Using a suspension with 0.03 wt.% ball milled $Ti_3SiC_2$ powder and 0.3 wt.% PEI, $Ti_3SiC_2$ MAX phase was successfully coated on SiC fiber with an EPD voltage of 10 V for 2 h. Most of the coated $Ti_3SiC_2$ powders are composed of spherical particles. Part of the $Ti_3SiC_2$ powders that are platelet shaped are oriented parallel to the SiC fiber surface. From these results we expect that $Ti_3SiC_2$ can be applied to the interphase of $SiC_f/SiC$ composites.

• 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 Crystal Growth and Crystal Technology
• /
• v.9 no.1
• /
• pp.14-19
• /
• 1999

Using a single precursor of hexamethyldisilane $(Si_{2}(CH_{3})_{6})$, $\beta$-SiC film was successfully deposited on a Si substrate at $1100^{\circ}C$ by a chemical vapor deposition method. Selectivity of SiC deposition on a Si substrate partially covered with a masking material was investigated by introducing HCl gas into hexamethyldisilane/$H_{2}$ gas system during the deposition. The schedule of the precursor and HCl gas flows was modified so that the selectivity of SiC deposition between a Si substrate and a mask material should be improved. It was confirmed that the selectivity of SiC deposition was improved by introducing HCl gas. Also, the pulse gas flow technique was effective to enhance the selectivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.199-200
• /
• 2009

This paper describes the electrical properties of polycrystalline (poly) 3C-SiC thin films with different nitrogen doping concentrations. The in-situ-doped poly 3C-SiC thin films were deposited by using atmospheric-pressure chemical vapor deposition (APCVD) at $1200^{\circ}C$ with hexamethyldisilane (HMDS: $Si_2$ $(CH_3)_6)$ as a single precursor and 0 ~ 100 sccm of $N_2$ as the dopant source gas. The peaks of the SiC (111) and the Si-C bonding were observed for the poly 3C-SiC thin films grown on $SiO_2/Si$ substrates by using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, respectively. The resistivity of the poly 3C-SiC thin films decreased from $8.35\;{\Omega}{\cdot}cm$ for $N_2$ of 0 sccm to $0.014\;{\Omega}{\cdot}cm$ with $N_2$ of 100 sccm. The carrier concentration of the poly 3C-SiC films increased with doping from $3.0819\;{\times}\;10^{17}$ to $2.2994\;{\times}\;10^{19}\;cm^{-3}$, and their electronic mobilities increased from 2.433 to $29.299\;cm^2/V{\cdot}S$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.4
• /
• pp.626-631
• /
• 1997

AlSiCa powders were prepared from the domestic Hadong Kaolin ($Al_2O_3{\cdot}2SiO_2{\cdot}2H_2O$). As a result of the reaction of Hadong Kaolin and carbon powder at reducing atmosphere, $Al_2O_3{\cdot}SiC$ composite started to form at $1300^{\circ}C$ and completed at $1400^{\circ}C$. The optimum amount of carbon was 1:4 in mole ratio. It was found that only bright-green $\beta-SiC$ phase forms when the mixture was packed without carbon powder in alumina crucible.

• Journal of the Korean Ceramic Society
• /
• v.51 no.5
• /
• pp.459-465
• /
• 2014

In this study, Si-SiC composites were fabricated using a Si melt infiltration method using ${\beta}$-SiC/C composite powders synthesized by the carbothermal reduction of $SiO_2-C$ precursors made from a TEOS and a phenol resin. The purity of the synthesized SiC-C composite powders was higher than 99.9993 wt% and the average particle size varied from 4 to $6{\mu}m$ with increasing carbon contents of the $SiO_2-C$ precursors. It was found that the Si-SiC composites fabricated in this study consist of ${\beta}$-SiC and residual Si, without any trace of ${\alpha}$-SiC. The 3-point bending strengths of the fabricated Si-SiC composites were measured and found to be higher than 550 MPa, although the density of the fabricated Si-SiC composite was less than $2.9g/cm^3$. The bending strengths and the densities of the fabricated Si-SiC composites were found to decrease with increasing C/Si mole ratios in the SiC-C composite powders. The specific resistivities of the Si-SiC composites fabricated using the SiC-C composite powders were less than $0.018{\Omega}cm$. With increasing C content in the SiC-C composite powders used for the fabrication of Si-SiC composites, the specific resistivity of the Si-SiC composites was found to slightly increase from 0.0157 to $0.018{\Omega}cm$.

• Journal of the Korean Ceramic Society
• /
• v.34 no.8
• /
• pp.825-833
• /
• 1997

Silicon carbide films were deposited by low pressure chemical vapor deposition(LPCVD) using MTS(CH3SICl3) in hydrogen atmosphere on (100) Si substrate. To prevent the unstable interface from being formed on the substrate, the experiments were performed through three deposition processes which were the deposition on 1) as received Si, 2) low temperature grown SiC, and 3) carbonized Si by C2H2. The microstructure of the interface between Si substrates and SiC films was observed by SEM and the adhesion between Si substrates and SiC films was measured through scratch test. The SiC films deposited on the low temperature grown SiC thin films, showed the stable interfacial structures. The interface of the SiC films deposited on carbonized Si, however, was more stable and showed better adhesion than the others. In the case of the low temperature growth process, the optimum condition was 120$0^{\circ}C$ on carbonized Si by 3% C2H2, at 105$0^{\circ}C$, 5 torr, 10 min, showed the most stable interface. As a result of XRD analysis, it was observed that the preferred orientation of (200) plane was increased with Si carbonization. On the basis of the experimental results, the models of defect formation in the process of each deposition were compared.

• Journal of the Korean Ceramic Society
• /
• v.35 no.8
• /
• pp.807-812
• /
• 1998

Mechanical properties of two types of polycrystlline {{{{ { { Ti}_{3 }SiC }_{2 } }} with different grain size were investigated. A fine grain {{{{ { { Ti}_{3 }SiC }_{2 } }} has a higher fracture strength and hardness. Plot of strength versus Vickers indentation load indicated that {{{{ { { Ti}_{3 }SiC }_{2 } }} has a high flaw tolerance. Hertzian indentation test using a spherical indenter was used to study elastic and plastic behavior in {{{{ { { Ti}_{3 }SiC }_{2 } }}. Indentation stress-strain curves of each material are made to evaluate the plasticity of {{{{ { { Ti}_{3 }SiC }_{2 } }} Both find and coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} showed high plasticity. In-dentation stress-strain curve of coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} deviated even more from an ideal elastic limit in-dicating exceptional plasticity in this material. Deformation zones were formed below the contact as well as around the contact area in both materials but the size of deformation zone in coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} was much larger than that in fine grain {{{{ { { Ti}_{3 }SiC }_{2 } }} Intragrain slip and kink would account for high plasticity. Plastic behavior of {{{{ { { Ti}_{3 }SiC }_{2 } }} was strongly influenced by grain size.