• Journal of the Korean Ceramic Society
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• v.19 no.1
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• pp.13-18
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• 1982

The crystallization of metastable "orthorhombic" phase from the glass in the system of Na $AlSi_3O_8-CaAl_2Si_2O_8$ is studied. These crystals are crystallized in the range of composition from $Ab_80An_20$ to An100. The symmetry of these crystals show orthorhombic as a possible space group P22121. Two probable twin models are proposed. proposed.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.92-98
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• 2006

Molecular dynamics simulations were performed to study interface structures between an $Al_2O_3$ crystalline phase and a interface phase of $CaAl_2Si_2O_8$. We calculated atomic structures and excess interface energies in systems with different thicknesses of the interface film. It was found that excess interface energies at first readily decreased with increasing film thickness, but increased for larger thicknesses of more than 2 nm. The excess energies of $Al_2O_3/CaAl_2Si_2O_8$ interfaces exhibit a minimum at a thickness around 1 nm. In this range of film thicknesses, the atoms in the interface film show a short-range ordered structure and slow diffusion rather than the random structure and rapid diffusion expected to an observation of an equilibrium thickness for interface films in ceramics.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.189-194
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• 1999

Crystallization of glasses in the system (Ca, Sr, Ba)$O-Al_2O_3-B_2O_3-SiO_2-TiO_2$ and dielectric properties of crystallized glasses were investigated. As increasing B2O3 content and decreasing SiO2 content in the glass, the major crystalline phase changed from $(Sr, Ba)_2TiSi_2O_8$ to (Ca, Sr, Ba)TiO3, the dielectric constant of crystallized glasses increased and the Temperature Coefficient of Capacitance (TCC) changed to negative. The dielectric constant and TCC was estimated for (Sr, Ba)2TiSi2O8 phase as 18 and -440 $ppm/^{\circ}C$, respectively and for (Ca, Sr, Ba)TiO3 phase as 307 and -1900 $ppm/^{\circ}C$, respectively. The dielectric properties of (Ca, Sr, Ba)TiO3 phase (in this study) were similar to those of (Ca, Ba) TiO_3 solid-solution^12)$, but $(Sr, Ba)_2TiSi_2O_8$ phase (in this study) and $Sr_2TiSi_2O_\;8^4$ showed the different properties.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.615-620
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• 2006

The reduction behavior of $TiO_{2}$ in Al and Al/CaSi containing self-reducing $TiO_{2}$ briquettes(SRTB) was investigated. The maximum yield of Ti was expected with the slag composition of 45-55%CaO in the $CaO-Al_{2}O_{3}$ system. When $CaCO_{3}$ was used as a flux, the oxidation loss of reducing agent by $CO_{2}$ should be compensated, and therefore it leads to excessive requirement of the reducing agent. By using Al and CaSi mixture as a reducing agent of $TiO_{2}$, the reaction products both oxide and metal could be liquefied, and separated effectively with each other. As a result, the yield of Ti increases remarkably. The optimum mixing ratio of CaSi to Al is 78%CaSi-22%Al.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1017-1024
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• 2000

Effect of the microwave dielectric properties and the microstructure on a mole fraction(x=0.1~0.9) of (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ ceramics was investigated. When (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$(x=0.1~0.9) ceramics were sintered at 130$0^{\circ}C$, 135$0^{\circ}C$ and 140$0^{\circ}C$ for 2hr, the microwave dielectric properties were obtained $\varepsilon$r=6.8~8.3, Q.f$_{0}$=36000~77600. On the other hand, the temperature coefficients of resonant frequency($\tau$$_{f}$) were obtained in the properties of -62ppm/$^{\circ}C$ to -49ppm/$^{\circ}C$. In order to adjust the temperature coefficient of resonant frequency($\tau$$_{f}$), CaTiO$_3$was added in (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ceramics. 0.7Mg$_2$SiO$_4$-0.2ZnAl$_2$O$_4$-0.1CaTiO$_3$ceramics sintered at 135$0^{\circ}C$ for 2hr showed the excellent microwave dielectric properties of $\varepsilon$r=7.7, Q.f$_{0}$=32000, and $\tau$$_{f}$=-7.9 ppm/$^{\circ}C$.EX>.>.EX>.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.291-299
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• 1993

Hydrothermal synthesis of 1.13nm tobermorite was performed to obtain the mixing ratio of raw materials, the optimum reaction time and the effect of aluminum in two systems, $CaO-SiO_2-H_2O$ and cement sludge-$SiO_2-H_2O$. 1.13nm tobermorite($5CaO{\cdot}6SiO_2{\cdot}5H_2O:C_5S_6H_5$) was synthesized excellently from $CaO-SiO_2-H_2O$ system on each mole ratio (0.4, 0.8) of $CaO/SiO_2$ at $180^{\circ}C$. But a tobermorite crystals had a sign of crystal conversion after 6 hours of reaction times in the case of $CaO/SiO_2=0.4$ and 4 hours of reaction time in the case of $CaO/SiO_2=0.8$. However, a tobermorite synthesized from cement sludge wastes did not show the crystal conversion on each mole ratio(0.4, 0.8) of $CaO/SiO_2$ within 10 hours of reaction times. It is considered that aluminum ions dissolved from cement sludge wastes retarded the recrystallization of tobermorite. This role of aluminum ion was confirmed in $CaO-SiO_2-H_2O+Al$ powder system. According as added amount of Al powder was increased from 0.8% to 3.0%, the crystal had a highly flatter and larger shape. Recrvstallization was not detected within the same reaction times when aluminum was added.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.111-118
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• 1996

In order to improve the chemical durability of glass in the $Na_2O$-CaO-$SiO_2$ system, it was investigated in the effect of $B_2O_3$ and ZnO addition and changing amount of each composition, $Na_2O$, $Al_2O_3$, $Li_2O$. In this minimize the change of softening point of glass was as follow.(wt%)$B_2O_3$:3.36%, ZnO:2.88%, $Na_2O$:9.93%, $Al_2O_3$, $Li_2O$:0.19%, $SiO_2$:70.56%, CaO:11.22%, $K_2O$:0.14%

• The Journal of the Petrological Society of Korea
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• v.1 no.1
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• pp.42-48
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• 1992

The equilibrium pressure-temperature curve of the reaction: 6 Ca$_2$Al$_3$(OH)Si$_3$O$_{12}$=6 CaAl$_2$Si$_2$O$_{8}$+2 Ca$_3$Al$_2$Si$_3$O$_{12}$+Al$_2$O$_3$+3 H$_2$O zoisite anorthite grossularite corundum was experimentally determined using both externally and internally heated pressure vessels in the pressure range of 2-4 kbar. Synthetic zoisite, anorthite, grossularite and corundum were used as starting materials. Starting materials were synthesized at 13-16 kbar using the piston-cylinder apparatus. The dehydration temperature of zoisite at 2 kbar is 550${\pm}$12$^{\circ}C$ and at 4 kbar is 575${\pm}$20$^{\circ}C$. Low thermal stability of synthetic zoisite relative to natural zoisite at 4 kbar is attributed to the structural disorder of synthetic anorthite.

• Journal of the Microelectronics and Packaging Society
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• v.3 no.2
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• pp.39-50
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• 1996

본 연구에선 주어진 조성의 알루미나 green sheet에 대하여 텅스텐의 입경 및 산화 물의 조성을 변화시키므로써 수축률을 제어하여 camber를최소화하여 결합강도를 최대로 하 는 텅스텐 페스트조성을 찾아내는 것을 목적으로 하였다. 본 실험에서 사용한 텅스텐 분말 의 입경은 0.35$\mu$m, 0.6$\mu$m, 0.72$\mu$m, $1.5\mu$m, 1.9$\mu$m, 3.2$\mu$m이며 frit는 Al2O3, MgO, SiO2 와 Al2O3, CaO, SiO2를 사용하여 각각의 조성에 따라 함량을 변화시키며 실험하였다. 소성 은 154$0^{\circ}C$로 습윤 수소분위기에서 시행하였으며 사용된 알루미나 green sheet의 알루미나 중심 입경은 2.8$\mu$m이었다. 분석은 주사전자 현미경으로 미세구조를 관찰하였고 EPMA Line Profile로 원소 분석을 하였으며 잔류응력을 측정하기 위하여 XRD분석을 하였다. Frit 을 함유하지 않은 경우 텅스텐 분말의 입경이 1.9$\mu$mdlfEo 최대 접합 강도를 나타내었다. Frit을 함유한 경우 Mgo계 frit조성에서는 MgO/Al2O3/SiO3=1/1/1일 때 CaO계 frot 조성에 서는 CaO/Al2O3/SiO2=1/2/1일 때 최대 접합 강도를 나타내었다. Frit 함량을 변화시킨 경우 MgO계는 10wt%함유하였을 때 CaO 계는 5wt%함유하였을 때 최대 접합강도를 나타내었 다. Frit 함량을 변화시킨 경우 MgO계는 10wt%함유하였을 때, CaOr계는 5wt%함유하였을 때 최대 접합강도를 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.272-273
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• 2006

LTCC(low temperature co-fired ceramics)용 glass/ceramic 복합체를 제조하기 위해 4 종류의 borosilicate계 glass를 선정하고 filler로 $Al_2O_3$ ceramics를 filler 사용하여 30~50 vol% glass frit에 따른 소결 및 유전 특성에 대하여 조사하였다. Glass frit은 $SiO_2$와 $B_2O_3$ 함량비를 고정한 후 R(CaO, BaO, ZnO, $Bi_2O_3$)에 따라 유리 연화온도(Ts)와 함량이 소결에 미치는 영향 및 유전 특성 변화를 고찰한 결과, CaO-$B_2O_3-SiO_2$ glass의 경우 다량의 2 차상이 형성되었고, 이에 $900^{\circ}C$ 이하에서 완전 소결이 이루어지지 않았으며, BaO-$B_2O_3-SiO_2$ glass는 celsian($BaAl_2Si_2O_8$) 결정이 형성되면서 소결성의 저하를 갖고 왔으며, ZnO-$B_2O_3-SiO_2$ glass는 소결이 진행됨에 따라 주상이 $Al_2O_3$에서 gahnite($ZnAl_2O_4$) 결정이 형성되면서 품질계수가 크게 증가하였으며, $Bi_2O_3-B_2O_3-SiO_2$ glass는 45 vol%일 때 $900^{\circ}C$에서부터 일정한 선수축율 특성을 나타내었지만, 다량의 액상으로 인하여 유전 특성의 저하를 나타내었다.