• Journal of the Korean Ceramic Society
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• v.36 no.6
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• pp.655-661
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• 1999

${\beta}$-SiC formation mechanism in Si melt-C-SiC system with varying in size of carbon source was investigated. A continuous reaction sintering process using Si melt infiltration method was adopted to control the reaction sintering time effectively. It was found that ${\beta}$-SiC formation mechanism in Si melt-C-SiC system was directly affected by the size of carbon source. In the Si melt-C-SiC system with large carbon source ${\beta}$-SiC formation mechanism could be divided into two stages depending on the reaction sintering time: in early stage of reaction sintering carbon dissolution in Si melt and precipitation of ${\beta}$-SiC was occurred preferentially and then SIC nucleation and growth was controlled by diffusion of carbon throughy the ${\beta}$-SiC layer formed on graphite particle. Furthmore a dissolution rate of graphite particles in Si melt could be accelerated by the infiltration of Si melt through basal plane of graphite crystalline.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.528-533
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• 2009

High purity $\beta$-SiC powders were synthesized using sol-gel processing. TEOS and phenol resin were used as the starting material for the silicon source and carbon source, respectively. The process turned out to be capable of producing high purity SiC powder purity degree with 99.98 %. However, it was difficult to control the shape and size of $\beta$-SiC powders synthesized by sol-gel process. In this study, $\beta$-SiC powder with size of $1{\sim}5$ um an 30 nm were used as the seeds for $\beta$-SiC to control the $\beta$-SiC powder morphology. It was found that $\beta$-SiC powder seeds was effective to increase the powder average size of synthesized $\beta$-SiC using sol-gel process by acting as the preferred growing sites for $\beta$-SiC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.770-776
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• 2009

The composites were fabricated by adding 0, 15, 30, 45[vol.%] $ZrB_2$ powders as a second phase to SiC matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by spark plasma sintering(SPS) were investigated. Reactions between ${\beta}$-SiC and $ZrB_2$ were not observed in the XRD and the phase analysis of the electroconductive SiC ceramic composites. The relative density of mono ${\beta}$-SiC, ${\beta}$-SiC+15[vol.%]$ZrB_2$, ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]$ZrB_2$ composites are respectively 99.24[%], 87.53[%], 96.41[%] and 98.11[%] Phase analysis of the electroconductive SiC ceramic composites by XRD revealed mostly of ${\beta}$-SiC, $ZrB_2$ and weakly of $ZrO_2$ phase. The flexural strength showed the lowest of 114.44[MPa] for ${\beta}$-SiC+15[vol.%]$ZrB_2$ powders and showed the highest of 210.75[MPa] for composite no added with $ZrB_2$ powders at room temperature. The trend of the mechanical properties of the electroconductive SiC ceramic composites is accorded with the trend of the relative density. The electrical resistivity of the electroconductive SiC ceramic composites decreased with increased $ZrB_2$ contents. The electrical resistivity of mono ${\beta}$-SiC, ${\beta}$-SiC+15[vol.%]$ZrB_2$, ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]$ZrB_2$ composites are respectively $4.57{\times}10^{-1},\;2.13{\times}10^{-1},\;2.68{\times}10^{-2}\;and\;1.99{\times}10^{-2}[{\Omega}{\cdot}cm]$ at room temperature. The electrical resistivity of mono ${\beta}$-SiC and ${\beta}$-SiC+15[vol.%]$ZrB_2$ are negative temperature coefficient resistance(NTCR) in temperature ranges from $25[^{\circ}C]\;to\; 100[^{\circ}C]$. The electrical resistivity of ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]ZrB_2$ are positive temperature coefficient resistance(PTCR) in temperature ranges from $25[^{\circ}C]\;to\;100[^{\circ}C]$. It is convinced that ${\beta}$-SiC+30[vol.%]$ZrB_2$ composites by SPS for heater or ignitors can be applied.

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.152-156
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• 1996

Fine (~0.09 $\mu$m) $\beta$-SiC Powders with 3.3wt% of large (~0.44$\mu$m) $\alpha$-SiC of $\beta$-SiC particles (seeds) added were hotpressed at 175$0^{\circ}C$ using $Y_2O_3$, $Al_2O_3$ and CaO as sintering aids and then annealed at 185$0^{\circ}C$ for 4 h to enhance grain growth. The resultant microstructure and polytypes were analyzed by high resolution electron microscopy (HREM).Growth of $\beta$-SiC with high density of microtwins and formation of ${\alpha}/{\beta}$ composite grains consisting of $\alpha$-SiC domain sandwiched between $\beta$-SiC domains were found in both specimens. When large $\alpha$-SiC (mostly 6H) seeds were added, the $\beta$-SiC transformend preferentially to the 6H polytype. In contrast, when large $\beta$-SiC (3C) seeds were added, the fine $\beta$-SiC transformed preferentially to the 4H polytype. Such results suggested that the polytype formation in SiC was influenced by crystalline form of seeds added as well as the chemistry of sintering aids. The ${\alpha}/{\beta}$ interface played and important role in the formation of elongated grains as evidenced by presence of ${\alpha}/{\beta}$ composite grains with high aspect ratio.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.67-73
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• 1986

SiC and $SiC-Si_3N_4$ powder were synthesized via the carbiding and carbiding-nitriding reaction of Jecheon quartz respectively using graphite as a reducing agent. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbiding-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $H_2$ atmosphere. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbidint-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $N_2-H_2$ atmosphere. The ratio of $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ content in a produced composite could be controlled by adjusting the reaction time and gaseous mixture.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.473-480
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• 1997

$\beta-SiC$powder with or without the addition of 1-3 wt% of $\beta-SiC$ whiskers (seeds) was hot-pressed at $1850^{\circ}C$ for 1 h using $Al_2O_3$ and $Y_2O_3$ as sintering aids. The hot-pressed materials were subsequently annealed at $1950^{\circ}C$ to enhance grain growth. The introduction of $\beta-SiC$ whiskers into $\beta-SiC$ does not affect the microstructure as well as mechanical properties significantly because the whiskers are not viable in the presence of liquid phase during hot-pressing. The strengths and fracture toughnesses of the hot-pressed and subsequently 5 h-annealed materials with 1 wt% $\beta-SiC$ whiskers and without $\beta-SiC$ whiskers were 465 MPa and 5.8 MPaㆍ$m^{1/2}$, and 451 MPa and 5.5 MPaㆍ$m^{1/2}$, respectively.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.853-858
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• 1999

To investigate the effect of H2 flow rate and TMS[Si(CH3)4] concentration on synthesizing ultrafine ${\beta}$-SiC powder by vapor phase reaction the experiment was performed at 1100$^{\circ}C$ of the reaction temperature under the condition of 200-2000 cc/min of H2 gas flow rate and 1-10% of TMS concentration respectively. The shape of ${\beta}$-SiC particles synthesized was spherical and the size of particles decreased and the distribution of particles was more uniform with increasing H2 gas flow rate. In this case Si powders were coexisted with ${\beta}$-SiC Pure and ultrafine ${\beta}$-SiC powders without Si were obtained under the condition of above 2% of TMS concentration and below 1500 cc/min of H2 gas flow rate.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.9-14
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• 1986

$\beta$-SiC bonded SiC bodies were prepared from various conditions such as several compositions of(Si+C)/$\alpha$ -SiC ratio and different firing schedules and were respectively investigated compressive strength MOR and mi-crostructure. One firing schedule which produced the specimens that had $\beta$-SiC neck form with the highest strength was selected and experimented by each firing temperature. results obtained are as follows : 1) The amount of (Si+C) for th highest MOR of SiC-(Si+C) sintered body is 20wt% 2) By adding 20wt% content of (Si+C) and heating up to 1, 500 with soaking 3hrs respectively at 1,150$^{\circ}C$ 1,250$^{\circ}C$ 1,350$^{\circ}C$ and 1,400$^{\circ}C$ the highest MOR of fired specimen was resulted and its microstructure of ma-trix was composed of close $\beta$-SiC neck. 3) Microstructure of $\beta$-SiC were different greatly from each other by firing time and/or quantity of adding mix-ture and it was confirmed that they were composed of neck particle-like and heterogeneous texture. 4)$\beta$-SiC synthesis proceed rapidly at the temperature between 1,250$^{\circ}C$ and 1,350$^{\circ}C$ 5) All of the properties of 85 SiC-20(Si+C) specimen improved according to increasing temperature above 1,350$^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1259-1264
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• 1994

$\beta$-Sialon has been regarded as one of promising materials showing high strength, fracture toughness, corrosion resistence and wear resistence. The improvement of the fracture toughness and tribological properties of $\beta$-Sialon (Z=1) has been attempeted by fabricating the $\beta$-Sialon/ SiC whisker composite. Each of green body composed of following ingredients, i.e., Si3N4, AlN, Y2O3 nd SiC, respectively, was first fired at 178$0^{\circ}C$ for 3hrs in N2 atmosphere and then post-HIPed at 173$0^{\circ}C$ for 1 hr under 170 MPa for N2 gas pressure. The fracture toughness, flexural strength and tribological properties increased with increasing SiC whisker content, despite the reduction of the relative density and hardness. $\beta$-Sialon/15 vol% SiC whisker showed a significant enhancement of wear resistance compared to the monolithic $\beta$-Sialon. The addition of SiC whisker caused the reduction of the density and hardness, but induced the increment of wear resistance.

• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.163-168
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• 1997

Most of heteroepitaxial $\beta$-SiC thin films have been successfully grown on Si(100) adapting a carburizing process, by which a few atomic layers of substrate surface is chemically converted to very thin SiC layer using hydrocarbon gas sources. Using an organo-silicon precursor, bis-trimethylsilymethane (BTMSM, [$C_7H_{20}Si_2$]), heteropitaxial $\beta$-SiC thin films were successfully grown directy on Si substrate without a carburized buffer layer. The defect density of the $\beta$-SiC thin films deposited without a carburized layer was as low as that of $\beta$-SiC films deposited on carburized buffer layer. In addition, void density was also reduced by the formation of self-buffer layer using BTMSM instead of carburized buffer layer. It seems to be mainly due to the characteristic bonding structure of BTMSM, in which Si-C was bonded alternately and tetrahedrally (SiC$_4$).