• 한국전기전자재료학회논문지
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• 제29권2호
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• pp.101-105
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• 2016

The basic characteristics of glass are highly fragile and brittle consequences the ultimate purpose of glass manufacturing is to make a transparent glass with complex shape. In order to solve this problem, mechanical properties of glass can be increased by crystallization of its amorphous glass. However, glass-ceramics has become opaque through crystallization process due to the distracted interface of glass by precipitated particles. This study has been investigated thermal processing conditions of LAS transparent glass-ceramic by using DTA (differential thermal analysis), in order to control size of precipitated particle and then fabricate transparent glass-ceramic. DTA indicated that crystallization peak area was declined with increased nucleation temperature. Subsequently, we have been established optimum temperature for crystallization depending on the nucleation temperature. The transmission and thermal expansion were measured after crystallization, and the size of precipitated particle was identified in range of 20~100 nm by FE-SEM. In addition, by setting the optimized crystallization condition, with high transmission and low thermal expansion glass was synthesized through this experiment.

• 한국세라믹학회지
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• 제25권5호
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• pp.431-436
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• 1988

The properties of scid-resistance to boiling HCl, thermal expansion coefficient and softening temperature of mother glass and glass-ceramic of LAS systems were investigated at the contents of SiO2 varing from 57 to 67wt%. The nucleation and growth of crystalline phase of LAS compositions were carried out at 50$0^{\circ}C$ and $700^{\circ}C$. The crystalline phase jconsists of lithium alumino silicate, lithum meta silicate, lithium disilicate, $\alpha$-crystobalite and $\alpha$-quartz. Lithium alumino silicate(virgilite) is the major crystalline phase in the glass ceramics. The degree of acid resistant property was increased in proportion with the silica content for both glass and ceramics. Glass-ceramic gives lower acid-resistance and thermal expansion coefficient while softening temperature shows higher for glass-ceramic than for mother glass.

• 한국세라믹학회지
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• 제44권8호
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• pp.451-456
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• 2007

This paper presents results and observations obtained from a study of sintering behavior and crystallization in $Li_2O-Al_2O_3-SiO_2$ (LAS) Glass by screen printing method. The variable experimental conditions were determined carefully by Thermal-Mechanical Analyzer (TMA), Differential Thermal Analyzer (DTA) for setting the optimum transparent sintering conditions in LAS glass system, $10.5Li_2O-14.7Al_2O_3-58.1SiO_2-16.7B_2O_3(wt%)$, such as glass-ceramics which usually have low crystallization temperatures. Crystallization glasses generated during sintering was observed from diffraction patterns by X-Ray Diffraction (XRD), transmittance by UV-Vis spectrometer. Finally, the optimum sintering condition of LAS glass and the relation between factors and results in several sintering conditions were given by using Response Surface Methodology (RSM). From this study, we confirmed that crystallization interrupted densification during glass powder sintering. Furthermore, we observed that main effect of factors in glass powder sintering with concurrent crystallization depended on experimental conditions from main effects plot by MINTAB-14.

• 한국재료학회지
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• 제14권7호
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• pp.505-510
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• 2004

The glass-ceramic based on LAS($Li_{2}O-Al_{2}O_3-SiO_{2}$) system was observed using SEM(Scanning Electric Microscopy) and AFM(Atomic Force Microscopy) and it was expected to get a correlation between the crystal size and the surface roughness through the result. At heat treatment conditions (the nucleation: $740\~800^{\circ}C$, the crystal growth: $900\~1150^{\circ}C$), the crystal size was increased from 72 to 450 nm so that the mean of surface roughness was also risen from 0.8 to 6.3 nm. Based on the results, the surface roughness of glass-ceramic is controlled by the factors, crystal size, crystallines, and the condition of heat treatment.

• 한국결정성장학회지
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• 제29권4호
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• pp.154-159
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• 2019

용융 온도를 낮추고 균질화에 영향을 줄 수 있는 yttrium oxide(산화 이트륨)과 iron oxide(산화철)를 사용하여 $LI_2O-Al_2O_3-SiO_2$ 계 결정화 유리를 제조하였다. 조핵제는 Zirconium sulfate(황산지르코늄)을 사용했고, 유리 점도를 낮추기 위해 calcium phosphate(인산칼슘)을 사용해 유리 유동성을 원활하게 하였다. 결정화 유리는 열충격 $750^{\circ}C$ 이상을 만족했고, $800^{\circ}C$ 이상에서 열팽창계수가 급격하게 상승하는 온도를 약 $30^{\circ}C$ 이상 시프트 하였다. 따라서 yttrium oxide와 iron oxide 포함하는 LAS 계 유리는 고온에서 양호한 용융 상태와 우수한 열팽창 저항성을 확인하였고 특수 주방용 재료 분야에 충분히 활용이 가능하리라 판단되었다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
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• pp.163.1-163
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• 2003

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.98-98
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• 2003

초내열성 결정화유리는 전기전자부품, 천체만원경의 반사경, 직화용 조리기기, 군사용 부품 등에 광범위하게 이용되고 있는데 이중 LAS 계가 가장 오랫동안 알려진 조성 계이다. 이 결정화유리는 주입성형후 열처리에 의하여 결정상을 생성하여 사용되는데 표면이 매우 낮은 조도를 갖는 것으로 알려져 있으나 실제로는 제조상에 조도가 높게 나타나는 문제점이 제기되고 있다. 따라서 본 연구에서는 미세조직적인 측면에서 이러한 점을 연구하고자 Li$_2$O-AL$_2$O$_3$-SiO$_2$를 주성분으로 하고 소량의 MgO와 핵생성제로서 TiO$_2$, ZrO$_2$를 사용하여 시편을 제조하였다. 제조된 결정화유리의 결정화도의 차이에 따라 AFM, $\alpha$-STEP등으로 표면의 조도를 정량화였다. 결정상의 종류, 크기, 결정화도, 결정상간의 간격 등이 표면의 조도에 어떻게 영향을 주는가 에 대하여 연구한 결과를 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1494-1496
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• 2002

내열 충격성 및 적외선 투과를 갖는 LAS($Li_2O-Al_2O_3-SiO_2$)계 글라스세라믹스를 제조하였다. 본 연구에서는 LAS계에 $TiO_2$를 핵형성제로, 점도를 감소시키기 위해 $P_2O_5$를 첨가하여 유리를 제조한 후, 글라스세라믹 결정상을 석출시켰다. 석출된 주 결정상은 ${\beta}$-eucryptite(SS)이었으며, 열팽창 계수가 거의 제로에 가까운 값을 얻었다. 또한 선택적인 스펙트럼의 흡수를 위한 color dopants에 대한 기초 자료 등이 조사되었다.

• 한국분말재료학회지
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• 제27권4호
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• pp.287-292
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• 2020

The subject of this study is a zeolite generated as a by-product of recycling LAS (lithium-aluminum-silicate) resources, a kind of glass and ceramic produced by induction. The zeolite by-product is modified into Mg-zeolite using Mg as a cation to absorb Pb, a heavy metal generated from water pollution caused by recent industrial wastewater. An ion-exchange method is used to carry out the modification process, from zeolite byproduct to Mg-zeolite, and simultaneously absorb the Pb in the heavy-metal solution (99.032 mg/L). It is found that the sodium zeolite in the raw material residue can be modified to magnesium zeolite by reacting it with a mixture solution at 1 M concentration for 24 h. As a result, it is found that the residual Pb (0.130 mg/L) in the heavy metal solution is shown to be absorbed by 99.86%, with successful formation of a Mg-modified zeolite.

• 한국세라믹학회지
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• 제32권2호
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• pp.171-182
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• 1995

Five eucryptite and ten spodumene compositional powders were syntehsized from three sillimanite group, two kaolin group, and five pyrophyllite group silicate minerals. Those powders were isotatically pressed and fired at 1200~135$0^{\circ}C$ for 2 hrs, and then the sintered bodies were characterized. Silicate minerals with molar ratio of Al2O3 to SiO2 correspond to those of eucryptite and spodumene are kaolin and pyrophyllite group silicate minerals, respectively. Sintering characteristics of eucryptite from kaolin group and spodumene from pyrophyllite group mineral were superior to those from other silicate minerals. Eucryptite sintered bodies with 95~97% relative densities and densified microstructures can be obtained using Hadong pink kaolin as starting materials by sintering over broad temperature zone(1250~135$0^{\circ}C$). The eucryptite sintered bodies which were fired at 130$0^{\circ}C$ for 2hrs, from Hadong pink kaolin had within 3.0wt% microstructural compositional variations compaired with stoichiometric compound, and had good negative thermal expansiion property with -3.55$\times$10-6/$^{\circ}C$ thermal expansion coefficient. Spodumene sintered bodies which were prepared from pyrophyllite group silicate minerals, had dense microstructures and high densities by densification through liquid phase sintering with enlarged temperature range. The specimens which were fired at 130$0^{\circ}C$ for 2 hrs from Gusipyrophillite, had dense microstructure with crystallines mainly, and low thermal expansion property with 0.62$\times$10-6/$^{\circ}C$ thermal expansion coefficient. The porous texture and residual glass phase in LAS system ceramics which were prepared from silicate minerals, tend to increase the thermal expansion properties of sintered bodies to positive direction.