• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.328-328
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• 2008

As a low K material for high frequency high integration modules, glass/ceramic composites were investigated. Glass composition were selected from $SiO_2-B_2O_3-Al_2O_3-R_2O$-RO system which having very low dielectric constant and cordierite was used as a ceramic filler. These composites were sintered at temperature range from $850^{\circ}$ to $950^{\circ}$ and XRD, SEM microstructure analysis of sintered bodies were performed for understanding sintering behavior. Any crystallization was not occurred and dense sintered bodies were attained. Dielectric and mechanical properties of these sintered glass/cordierite composites were analysed by network analyzer and UTM. Glass/ceramic composite with 50 wt% cordierite showing a dielectric constant (${\varepsilon}_r$) of 5.4, Q${\times}f_0$ (Q) of 1600 at 1 GHz and maximum bending strength of 163 MPa was attained.

• 한국세라믹학회지
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• 제43권6호
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• pp.344-350
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• 2006

Porous cordierite was synthesized by the mechano-chemical processing using fly ash. The phase evolution of cordierite was investigated as a function of processing variables such as milling time and sintering temperature. In this study, the phase transition path of cordierite from fly ash was followed by sapprine/spinel ${\to}$ mullite/spinel ${\to}{\alpha}$-cordierite. Porous cordierite fabricated after 32 h of milling time and sintering at $1150^{\circ}C$ showed relatively low thermal expansion coefficient ($2.5{\times}10^{-6}/^{\circ}C\;(25{\sim}1000^{\circ}C$)) and high porosity (75%).

• 한국세라믹학회지
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• 제27권2호
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• pp.256-264
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• 1990

Cordierite(2MgO$.$2Al2O3$.$5SiO2) was known to display low thermal expansions over wide temperature ranges, but showed poor mechanical strength. The present studies have been concerned with the sintering of cordierite based ceramics containing pure or stabilized zirconia. The crystallographic and microstructural results were not affected by the fact whether added zirconia was stabilized or not. As the contents of zirconia were increased, M.O.R., KIC, bulk densities were increased but the thermal expansion coefficients were decreased.

• 한국세라믹학회지
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• 제41권2호
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• pp.151-157
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• 2004

안정한 산화물 세라믹스 재료로서 mullite와 cordierite는 우수한 열적, 화학적 특성 때문에 구조재료에서부터 전자재료에 이르는 폭넓은 용도에 사용되어지고 있다. 그럼에도 불구하고, mullite는 천연에서는 산출되지 않기 때문에 합성에 의해서만 제조되고 있다. 또한, cordierite는 합성온도폭이 좁아 고순도의 미립 분말을 제조하기 어려운 재료이다. Mullite 역시 고상반응법 등의 합성법으로는 균질한 재료로의 합성이 어렵다. 그렇기 때문에 sol-gel법 등의 다양한 합성법에 의해 이들 재료에 관한 연구가 계속되고 있다. 본 연구에서는 국내의 원료를 이용하여 sol-gel법에서와 같은 고순도의 미립의 분말을 좀 더 낮은 온도에서 합성이 가능하며, 상대적으로 저가의 원료를 사용함으로서 경제적인 방법인 PVA를 polymer carrier로서 이용한 solution-polymerzation 합성법에 의해 mullite와 cordierite를 합성하였다. 그 결과, mullite, cordierite는 각각 120$0^{\circ}C$, 125$0^{\circ}C$에서 단일의 결정상이 생성되었으며 비표면적 20$m^2$/g 이상의 미립의 분말이 생성됨을 확인할 수 있었다.

• 한국세라믹학회지
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• 제44권4호
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• pp.230-234
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• 2007

Cordierite ceramics were fabricated via a reaction sintering process using ceramics-filled polysiloxane as a precursor for cordierite ceramics. In this study, the effects of the additive composition, additive content, and sintering temperature on the sintered density and compressive strength of cordierite ceramics have been investigated The sintered densities of reaction-sintered cordierite ceramics containing $TiO_2$ as an additive were insensitive to the additive composition, additive content, and sintering temperature and ranged from $1.92g/cm^3\;to\;2.06g/cm^3$. In contrast, the cordierite ceramics containing $Y_2O_3$ showed a maximal density of $2.21g/cm^3$ at 5 wt% addition and at a sintering temperature of $1400^{\circ}C$. The compressive strength of cordierite ceramics showed the same tendency with the density. Typical compressive strength of cordierite ceramics containing 5 wt% $Y_2O_3$ as a sintering additive and sintered at $1400^{\circ}C\;was\;{\sim}480MPa$.

• 한국재료학회지
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• 제25권7호
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• pp.330-335
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• 2015

A low thermal expansion ceramic, cordierite ($2MgO{\cdot}2Al_2O_3{\cdot}5SiO_2$), was synthesized using pyrophyllite. Pyrophyllite usually consists of $SiO_2$ and $Al_2O_3$, which are the main components of cordierite. $MgCO_3$ and $Al(OH)_3$ were added in various amounts to pyrophyllite and fired for synthesis and sintering. ${\alpha}$-cordierite crystallized from $1000^{\circ}C$ with mixing of 20 wt% $MgCO_3$ and 1.7 wt% $Al(OH)_3$, and un-reacted cristobalite was also detected with the cordierite. As the temperature was increased to $1400^{\circ}C$, the cordierite yield was gradually increased. Powder compacts of the synthesized cordierite were sintered between $1250^{\circ}C{\sim}1400^{\circ}C$; the sintered samples showed a low thermal expansion coefficient of $2.1{\times}10^{-6}/^{\circ}C$ and typical sintering behavior. It is anticipated that it will be possible to synthesize cordierite ceramics on a mass production scale using the mineral pyrophyllite.

• 한국세라믹학회지
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• 제44권5호
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• pp.184-189
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• 2007

In this study, a novel-processing route for producing microcellular cordierite ceramics has been developed. The proposed strategy for making the microcellular cordierite ceramics involves three steps: (i) fabricating ceramic-filled preceramic foams by heating a mixture of polysiloxane, expandable microspheres, talc, and alumina in a mold, (ii) cross-linking the foamed body, and (iii) transforming the body into microcellular cordierite ceramics by sintering. Cu jig was used for near net shaping in the foaming step. The experimental variables such as the shape of foaming jig and the content of expendable microsphere were investigated. By controlling the content of expendable microsphere, it was possible to make the porous cordierite ceramics with cell density of ${\sim}1.0{\times}10^9\;cells/cm^3$.

• 한국세라믹학회지
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• 제23권5호
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• pp.9-16
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• 1986

The effect of $TiO_2$ addition to the 90wt% Cordierite-10wt% Enstatite base glass was investi-gated to understand the crystallization behavior of the glass. Glasses with addition of $TiO_2$ less than 7, 5wt% had a tendency of surface crystallization and were cracked when heat treated and in this case the crystalline phase formed was indialite. glasses with addition of $TiO_2$ more than 10wt% to 15wt% were crystallized in bulk when heat treated and were suitable for glass-ceramics. The highest microhardness 1640kg/$mm^2$ was obtained when the glass of 12.5wt% $TiO_2$ addition was heat treated at 762$^{\circ}C$ for 60 minutes for nucleation and at 1135$^{\circ}C$ for 20 minutes for crystal growth and in general higher microhardness was obtained when crystalline phase of magnesium aluminum titanate and $\mu$-cordierite were developed. Avrami equation for crystal growth kinetics was applicable in glasses of less than 7.5 wt% $TiO_2$ addition and in case of glasses of more than 10wt% $TiO_2$ addition it was not applicable because of too fast crystal growth.

• 한국세라믹학회지
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• 제41권9호
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• pp.663-669
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• 2004

Mullite와 cordierite는 우수한 열적, 화학적 특성을 나타내는 안정된 산화물로서 다양한 구조재료 및 전자재료에 사용되어지고 있으나, mullite의 경우 내열충격성이, cordierite의 경우 고온강도가 떨어지는 단점이 있다. 이와 같은 단점을 서로 보완하기 위한 mullite-cordierite 복합체에 대한 연구가 진행되고 있다 본 연구에서는 fused silica, aluminium nitrate, magnesium nitrate와 PVA의 혼합을 이용한 solution-polymerization 합성법에 의해, mullite-cordierite복합분말을 합성하고 생성상 및 결정성, 밀도 및 비표면적 등의 특성을 분석하였다 그 결과, 본 실험의 모든 조성에서 있어서 130$0^{\circ}C$로 열처리하였을 경우, mullite와 cordierite의 상이 공존하는 복합분말이 생성되는 것을 확인할 수 있었다. 이 mullite-cordierite복합 분말을 planetary milli로 1시간 분쇄하였을 때 비표면적은 약 20 $m^2$/g로서 미립의 분말이 확인되어졌고, 분쇄시간의 증가에 따라 4시간에서는 23$m^2$/g, 8시간에서는 24$m^2$/g로 비표면적이 증가하였다.

• 한국세라믹학회지
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• 제12권4호
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• pp.19-28
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• 1975

In order to obtain the superior refractory setter having better spalling resistance, cordierite was synthesized from domestic raw materials. Raw mixtures were fired between 125$0^{\circ}C$ and 140$0^{\circ}C$, and qualitative determination of crytallization was investigated by x-ray diffraction analysis. The results obtained are as follows; 1) The optimum batch composition of synthesized cordierite is 80.5% of Hadong kaolin (pink), 14% of Kyulsung tromolite talc and 5.5% of magnesia clinker, and the firing temperature is 1375$^{\circ}C$. 2) The composition of the refractory setter which exhibits the best values for the thermal properties is 40% of synthesized cordierite, 30% of kaolin chamotte(contains more than 60% of mullite), and 30% of Japanese clay. 3) The optimum particle size distribution of ternary mixture consists of 50% of coarse articles (3.327-1.168mm), 25% of intermediate particles (1.168-0.208mm) and 25% of fine particles (0.208-0.000mm).