• Title/Summary/Keyword: Silicon Carbide Whiskers

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Effect of Silicon Nitride Whisker Content on the Flexural Strength of Silicon Nitride-Boron Nitride-Silicon Carbide Multi-Layer Composites

  • Park, Dong-Soo;Cho, Byung-Wook
    • Journal of the Korean Ceramic Society
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    • v.40 no.9
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    • pp.832-836
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    • 2003
  • Multi-layer ceramic composites were prepared by tape casting followed by hot pressing using silicon nitride layer with silicon nitride whiskers, silicon nitride layer with silicon carbide particles and boron nitride-alumina layer. The whiskers were aligned during the casting. As the whisker content of the silicon nitride layer was increased up to 10 wt%, the flexural strength of the multi-layer composite was increased. However, further increase of the whisker content in the layer resulted in a rapid decrease of the strength of the composite. The results suggest that the strength of multi-layer ceramic composite showing non-catastrophic failure behavior can be significantly improved by incorporating the aligned whiskers in the layers.

SiC Synthesis by Using Sludged Si Power (폐슬러지 Si 분말을 이용한 SiC 제조)

  • 최미령;김영철;장영철
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.3
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    • pp.67-71
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    • 2003
  • Sawing silicon ingot with abrasive slurry generates sludge that includes abrasive powders, cutting oil, and silicon powders. The abrasive powders and cutting oil are being separated and reused. Mixing the remained stodged silicon powders with carbon powders and subsequent heat-treatment are conducted to produce silicon carbide. The size of SiC whiskers and powders was smaller than the conventionally grown silicon carbide whiskers that were synthesized by adding micron-size metal impurities. Impurity related mechanism is attributed to the formation of the silicon carbide whiskers, as metal impurities are contained in the stodged silicon powders.

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Synthesis of $\beta$-SiC Whiskers by the Carbothermal Reduction of Kaolin (카올린의 환원 열탄화법에 의한 베타 탄화규소 휘스커의 합성)

  • 오세정;류종화;조원승;최상욱
    • Journal of the Korean Ceramic Society
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    • v.35 no.12
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    • pp.1249-1256
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    • 1998
  • ${\beta}$-Silicon carbide(${\beta}$-SiC) whiskers could be synthesized by the carbothermal reduction of kaolin at tem-peratures between 1400 and 1500$^{\circ}C$. The whiskers were grown up to about 1150 of aspect ratio by VS mechanism (showing tapering tips) and to about 45 of that by VLS mechanism (showing round droplet tips) respectively. Hydrocarbon like methane in the reaction atmosphere promoted the formation of gaseous il-icon monoxide(SiO) from silicon dioxide(SiO2) and subsequently reacted with it to form whiskers. The for-mation of ${\beta}$-SiC whiskers increased with increasing carbon content(to 30 wt%) and reaction temperatures. The max. yield of ${\beta}$-SiC whiskers was 15% at 1500$^{\circ}C$ under 20%CH4/80%H2.

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Synthesis of Silicon Carbide Whiskers (II): Stacking Faults (탄화규소 휘스커의 (II): 적층결함)

  • 최헌진;이준근
    • Journal of the Korean Ceramic Society
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    • v.36 no.1
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    • pp.36-42
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    • 1999
  • Stacking faults in SiC whiskers grown by three different growth mechanisms; vapor-solid(VS), two-stage growth(TS), and vapor-liquid-solid (VLS) mechanism in the carbothermal reduction system were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The content of stacking faults in SiC whiskers increased with decreasing the diameter of whiskers, i.e., the small diameter whiskers (<1 $\mu\textrm{m}$) grown by the VS, TS, and VLS mechanisms have heavy stacking faults whereas the large diameter whiskers(>2$\mu\textrm{m}$) grown by the VLS mechanism have little stacking faults. Heavy stacking faults of small diameter whiskers was probably due to the high specific lateral surface area of small diameter whiskers.

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Formation and Characterization of Silicon Carbide Whiskers by Acheson Method (에치슨법에 의한 탄화규소 휘스카의 성장과 특성분석)

  • 주한용;김형준
    • Journal of the Korean Ceramic Society
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    • v.27 no.1
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    • pp.136-146
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    • 1990
  • Whiskers of SiC were grown from the mixture of silica and graphite powders by Acheson method(direct heating method). The structrua, morphological and chemical characterizations have been performed by X-ray diffractometer(XRD), transmission electron microscopy(TEM), optical microscopy(OM), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS). The growth mechanism of SiC whiskers is also discussed.

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Texture Development in Liquid-Phase-Sintered β -SiC by Seeding with β -SiC Whiskers

  • Kim, Won-Joong;Roh, Myong-Hoon
    • Journal of the Korean Ceramic Society
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    • v.43 no.3 s.286
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    • pp.152-155
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    • 2006
  • Silicon carbide ceramics seeded with 10-30 wt% SiC whiskers are fabricated by hot pressing and annealing. A quantitative texture analysis including calculation of the Orientation Distribution Function (ODF) is used for obtaining the degrees of preferred orientation of the fabricated samples. The microstructure and crystallographic texture are discussed with respect to the effect of ${\beta}-SiC$ whisker seeds on the resulting fracture toughness values. The SEM microstructures and the texture data reveal a correlation between texture and fracture toughness anisotropy.

Synthesis of Silicon Carbide Nanowhiskers from Coconut Fibres and Sol-Gel Derived Silica

  • Raman, V.;Bhatia, G.;Mishra, A.;Saha, M.;Sengupta, P.R.;Srivastava, A.K.
    • Carbon letters
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    • v.7 no.3
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    • pp.166-170
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    • 2006
  • Silicon carbide whiskers ($SiC_w$) having the diameter in the range of 20-80 nm were synthesised from coconut fibres through sol-gel process. The coconut fibres were impregnated with tetraethoxysilane and methyltriethoxysilane derived sol and pyrolyzed at $1400^{\circ}C$ in argon. X-ray of the pyrolyzed samples showed the formation of ${\beta}$-SiC.

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Synthesis of Silicon Carbide Whiskers (I) : Reaction Mechanism and Rate-Controlling Reaction (탄화규소 휘스커의 합성(I) : 반응기구의 율속반응)

  • 최헌진;이준근
    • Journal of the Korean Ceramic Society
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    • v.35 no.12
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    • pp.1329-1336
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    • 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.

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Zirconia Coating of SiC Whiskers Using the Aqueous Solutions of Zr(SO4)2 ($Zr(SO_4)_2$ 수용액을 이용한 SiC 휘스커의 지르코니아 코팅)

  • Kim, Duk-Jun;Kim, Hwan
    • Journal of the Korean Ceramic Society
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    • v.33 no.12
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    • pp.1380-1386
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    • 1996
  • The effects of urea addition and reaction conditions were examined in the prepareation of zirconia coated SiC whiskers through surface precipitation taking place during high-temperature aging of Zr(SO4)2 solutions containing the whiskers. More dense zirconia-hydrate was precipitated on the surfaces of the whiskers in the presence of urea. The ratio of the concentration of Zr(SO4)2 to the amount of added whiskers was the most important factor to confine the precipitation of zirconia-hydrate only at the surfaces of the whiskers The from of the coating layers was unchanged after heat-treatment leading to the dehydration and crystallization of the layers.

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The Effect of Chemical Vapor Infiltrated SiC Whiskers on the Change in the Pore Structure of a Porous SiC Body

  • Joo, Byoung-In;Park, Won-Soon;Choi, Doo-Jin;Kim, Hai-Doo
    • Journal of the Korean Ceramic Society
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    • v.43 no.4 s.287
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    • pp.199-202
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    • 2006
  • In this study, SiC whiskers were grown on a porous SiC diesel particulate filter for nanoparticle filtering. To grow the whiskers at the inner pore without closing the pores, we used chemical vapor infiltration with a solution source and a dilute. As the deposition time increased, the whiskers grew and formed a network structure. After 180 min of deposition, the mean diameter of the whiskers was 174 nm and the compressive strength was 58.4 MPa. The pores shrank from $10{\mu}m\;to\;0.4{\mu}m$ and, because the whiskers filed the inner pores, the gradient of permeability decreased as the deposition time increased. However, by using the network structure of whiskers deposited for 120 min and 180 min, we obtained a diesel particulate filter with pores of $0.98{\mu}m\;and\;0.4{\mu}m$, respectively. Furthermore, the filter shows better permeability than a porous body with pores of $1{\mu}m$. In short, by filtering the nanoparticulate materials, the network structure of whiskers improves the strength, reduces the pore size and minimizes the permeability drop.