• 제목/요약/키워드: $LAS(Li_2O-Al_2O_3-SiO_2)$

검색결과 19건 처리시간 0.028초

LAS($Li_2O.Al_2O_3.SiO_2$)계 소지의 소결특성에 관한 연구 (The Study of Sintering Characteristics in LAS(Li2O.Al2O3.SiO2) System)

  • 이응상;박현;김동환
    • 한국세라믹학회지
    • /
    • 제29권2호
    • /
    • pp.127-135
    • /
    • 1992
  • It has been reported that natural petalite showed a low negative thermal coefficient and wide coefficient and wide coexisting region with liquid phase in Li2O-Al2O3-SiO2 system. Therefore, we investigated variation of microstructure and thermal and mechanical properties when the amount of SiO2 content in petalite compound and MgO addition to it compound were changed. As SiO2 content exceeded 80 wt%, crystal phases of $\beta$-cristobalite and $\beta$-spondumene solid solution were formed. Generally, the densification and bending strength were increased by the addition of MgO, but the positive thermal coefficient was found in the case of MgO 10 wt% addition because of second phase and glassy phase.

  • PDF

RSM 법에 의한Li2O-Al2O3-SiO2 (LAS) 유리의 소결 거동과 결정화에 대한 연구 (A Study of Sintering Behavior and Crystallization in Li2O-Al2O3-SiO2 (LAS) Glass System by RSM)

  • 이규호;김영석;정영준;김태호;서진호;류봉기
    • 한국세라믹학회지
    • /
    • 제44권8호
    • /
    • pp.451-456
    • /
    • 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.

고상반응법을 이용한 LAS계의 CaCO3와 ZrO2 첨가에 따른 소결체 특성 연구 (Sintered body characteristics of LAS by addition of CaCO3 and ZrO2 using a solid-state reaction)

  • 김상훈;강은태;김응수;황광택;조우석
    • 한국결정성장학회지
    • /
    • 제21권5호
    • /
    • pp.218-224
    • /
    • 2011
  • 저열팽창 특성을 갖는 난소결 물질인 LAS($Li_2O-Al_2O_3-SiO_2$)계를 고상 소결로 제조하였다. LAS계의 ${\beta}$-spodumene($Li_2O-Al_2O_3-4SiO_2$) 조성에 소결 조제로 $CaCO_3$를 첨가하였고, 강도 증가를 위하여 $ZrO_2$를 첨가하였다. 첨가제의 양의 변화와 소결 온도의 변화에 따른 소결 특성, 미세 구조, 기계적 특성 및 열팽창 특성에 대하여 조사하였다. 0.1 mol%의 $CaCO_3$을 첨가하였을 때, 치밀화가 증진됨을 미세구조 관찰에 의해 확인하였으며, $ZrO_2$의 첨가로 강도가 증진됨을 확인하였다. Dilatometer로 측정한 열팽창 계수는 선택된 전 조성에서 값이 $1.2{\sim}1.7{\times}10^6/^{\circ}C$임을 확인하였다.

결정화도에 따른 LAS$(Li_2O-Al_2O_3-SiO_2)$계 결정화유리의 표면조도특성 (Surface Roughness of Glass-Ceramic $(Li_2O-Al_2O_3-SiO_2)$ System Based on Different Crystallinities)

  • 김유진;정병해;이창훈;김형순
    • 한국재료학회:학술대회논문집
    • /
    • 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
    • /
    • pp.98-98
    • /
    • 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.

  • PDF

Li2O-Al2O3-SiO2(LAS)계 결정화유리에서 결정크기와 표면조도 관계 (Relationship between Surface Roughness and Crystal size of Li2O-Al2O3-SiO2(LAS) Glass-Ceramic System)

  • 김유진;황성진;김형순
    • 한국재료학회지
    • /
    • 제14권7호
    • /
    • pp.505-510
    • /
    • 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.

$Li_2O-Al_2O_3-SiO_2$계 소지내에 Zircon상 형성에 따른 내열 강화 특성 (A Study on the Thermal Resistance Strength with the Formation of the Zircon Phase in LAS System)

  • 전덕일;김정욱;이응상
    • 한국세라믹학회지
    • /
    • 제29권12호
    • /
    • pp.935-941
    • /
    • 1992
  • The LAS system with good thermal properties has a narrow range of firing and sintering temperature near the melting point. So it is difficult to sinter LAS to dense sintered body. In this study, the petalite (Li2O.Al2O3.8SiO2) with good thermal properties, was taken as a base composition, and zironia was added in this composition to broaden the firing range, increase the mechanical strength, and control the thermal expansion. The thermal and mechanical properties were investigated. The results are as follows; 1. Zirconia phase was formed in LAS matrix and apparent porosity was decreased from 0.9% to 0.5%, and the mechanical strength was kincreased from 112 MPa to 190 MPa, by the densification of body. 2. The composition Li2O.Al2O3.8SiO2 has a negative thermal expansion, but the thermal expansion was changed from negative to positive with the densification and the increase of amount of synthesized zircon phase which had positive thermal expansion. The coefficient of thermal expansion, with the increase of the amount of additives, was low as -0.74~9.06$\times$10-7/$^{\circ}C$ in 20~$600^{\circ}C$, and 7.95~20.13$\times$10-7/$^{\circ}C$ in 20~80$0^{\circ}C$. 3. The mechanical strength of LZ15 (added with ZrO2.SiO2 15 wt%) composition thermal-shocked was stable in the temperature range of 0~$600^{\circ}C$, but rapidly decreased due to the increase of thermal expansion above $600^{\circ}C$.

  • PDF

$Li_2O$-$Al_2O_3$-$SiO_2$계 소지의 내열 강화특성(I) (The Thermally Resistance Strength of LAS($Li_2O$-$Al_2O_3$-$SiO_2$)System(I))

  • 이응상;최성철;박현;조우석
    • 한국세라믹학회지
    • /
    • 제27권2호
    • /
    • pp.283-287
    • /
    • 1990
  • The study was aimed at investigating sintering characteristics, the overall properties from the ternary Li2O-Al2O3-SiO2 system. This system, which was considered without additives and selected five compositions, was studied with variation of the amount of SiO2. The reactivity of the system was observed by D.T.A.. Characteristics of sintering, microstructure, property and stability of produced phase were studied. It was found that because the range of sintering was narrow and the temperature of sintering was close to the melting temperature, the sintering by the general method was difficult. Also, these linear thermal expansion coeffecients were measured.

  • PDF

Li2O-Al2O3-SiO2계 결정화 유리의 특성(I) (Properties of Li2O-Al2O3-SiO2 Glass Ceramic System(I))

  • 양준환;정헌생
    • 한국세라믹학회지
    • /
    • 제25권5호
    • /
    • pp.431-436
    • /
    • 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.

  • PDF

실리케이트 광물을 이용한 내열충격성 LAS계 세라믹스의 제조에 관한 연구: (I) Sillimanite와 Kaolin족 광물을 이용한 Eucryptite 분말합성 (The Study on Fabrication of LAS System Ceramics for Thermal Shock Resistance from Silicate Minerals: (I) Preparation of Eucryptite Powders with Sillimanite Group, Kaolin Group Minerals)

  • 박한수;조경식;문종수
    • 한국세라믹학회지
    • /
    • 제31권5호
    • /
    • pp.572-580
    • /
    • 1994
  • With low thermal expansion coefficients, eucryptite (Li2O.Al2O3.2SiO2) and spodumene (Li2O.Al2O3.4SiO2) in LAS ceramic system show good thermal shock resistance. In this study, sillimanite or kaolin group silicate minerals and Li2CO3 were used as starting materials, and if necessary SiO2 or Al2O3 were added for making stoichiometrically formed specimens. By this process, eucryptite powders were synthesized and characterized. The powder mixtures of lithiumcabonate and silicate minerals calcined at 80$0^{\circ}C$ for 2 hrs were made into powder compacts. $\beta$-Eucryptite single phase was formed via intermediate phases of Li2SiO3 and LiAlO2 et al, by heating at 110$0^{\circ}C$ or 120$0^{\circ}C$ for 10 hrs from those powder compacts. When using the sillimanite group minerals, Virginia kyanite or andalusite was reacted to form eucryptite at 120$0^{\circ}C$and CMK International kyanite were completed at 110$0^{\circ}C$. When kaolin group minerals were used, it was found that the synthesizing temperature (100$0^{\circ}C$) of $\beta$-eucryptite from the mixture of New Zealand white kaolin was lower than that from Hadong pink kaolin (110$0^{\circ}C$). The Microstructure of systhesized powder showed the irregular lump shape such as densed crystallines.

  • PDF

Sol-Gel 반응으로 유도된 LAS의 상 생성과 점성 특성 (Phase Formation and Rheological Characteristics of LAS Derived from the Monophasic Sol-Gel Route)

  • 장현명;김광수;정창주
    • 한국세라믹학회지
    • /
    • 제28권5호
    • /
    • pp.365-372
    • /
    • 1991
  • LAS (lithium aluminosilicate) sol was synthesized using the hydrolysis-condensation reaction of TEOS, chelated Al(OBus)3 and Li-salt with H2O in alcohol (EtOH+2-Propanol) medium. Effects of important reaction parameters on the properties of sol and gel-derived LAS were examined. The crystallization of the sol-gel derived LAS with ${\beta}$-spodumene composition began at ∼600$^{\circ}C$, and a series of polymorphic transformations occurred as temperature was increased to 1100$^{\circ}C$: amorphous LAS\longrightarrowhexagonal LiAl(SiO3)2\longrightarrow${\beta}$-spodumene. Lowering Li content in the gel enhanced densification and retarded the crystallization significantly. Optimum reaction conditions of LAS sol formation for thin coating applications were derived from rheological measurements, and these can be summarized as: H2O/total alkoxides molar ratio=4, pH=∼2.5, and aging time of ∼250h.

  • PDF