• Title, Summary, Keyword: sol-gel technique

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Sol- Gel Synthesis and Luminescent Properties of ${Y_2}{SiO_5}:Ce$ Blue Phosphors (${Y_2}{SiO_5}:Ce$ 청색 형광체의 졸-겔 합성 및 발광특성)

  • Lee, Jun;Han, Cheong-Hwa;Park, Hee-Dong;Yun, Sock-Sung
    • Korean Journal of Materials Research
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    • v.11 no.9
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    • pp.740-744
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    • 2001
  • The $Y_2SiO_5:Ce$ phosphors were synthesized by sol-gel technique in order to improve the performance of blue emitting phosphors for field emission display(FED). The resulted$Y_2SiO_5:Ce$ phosphors enhanced the emission intensity. In addition, calcination temperature of sol-gel technique(1300~140$0^{\circ}C$) was lower than that of the solid state reaction(>1$600^{\circ}C$). Under 365 nm and low voltage electron excitations. $Ce^{3+}$ -activated $Y_2SiO_5$phosphors showed blue emission band with a range of 400~ 430nm. Especially, 2mol% $Ce^{3+}$ doped $Y_2SiO_5:Ce$phosphors showed the maximum emission intensity. We have also controlled drying temperature of wet gel, pH, and $H_2O$/TEOS molar ratio for the optimum condition of TEOS hydrolysis.

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Preparation of Glass-Ceramics in $Li_2O-Al_2O_3-TiO_2-SiO_2$ System by Sol-Gel Technique : (II) Crystallization of $Li_2O-Al_2O_3-TiO_2-SiO_2$ Monolithic Gel Prepared by Sol-Gel Method (Sol-Gel 법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 다공성 결정화 유리의 제조 : (II) Sol-Gel 법에 의해 제조된 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 괴상겔의 결정화)

  • 조훈성;양중식
    • Journal of the Korean Ceramic Society
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    • v.32 no.4
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    • pp.507-515
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    • 1995
  • The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

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Preparation of Glass-Ceramics in $Li_2O-Al_2O_3-TiO_2-SiO_2$ System by Sol-Gel Technique : (I) Preparation of Porous Monolithic Gel in $Li_2O-Al_2O_3-TiO_2-SiO_2$ System by Sol-Gel Method (Sol-Gel법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$계 다공성 결정화 유리의 제조 : (I) Sol-Gel 방법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$계 다공성 겔체의 제조)

  • 조훈성;양중식;권창오;이현호
    • Journal of the Korean Ceramic Society
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    • v.30 no.7
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    • pp.535-542
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    • 1993
  • It was investigated in this study that a preparation method, activation energy, surface area, pore volume, pore size distribution and DTA analysis of the dry gel in process of producing monolithic porous gel in Li2O-Al2O3-TiO2-SiO2 system by the sol-gel technique using metal alkoxides. Activation energy for gellation according to the variation of water concentration and the kind of catalysts ranged from 10 to 20kcal/mole. Monolithic dry gels were prepared after drying at 9$0^{\circ}C$ when the amount of water for gellation was 4~8 times more than the stoichiometric amount, that was necessary for the full hydrolysis of the mixed metal alkoxide. The specific surface area, the pore volume, the average pore radius of the dried gel at 18$0^{\circ}C$ according to the various kinds of catalyst were about 348~734$m^2$/g, 0.35~0.70ml/g and 10~35$\AA$, respectively. It showed that the dry gels were porous body. As a result ofthe analysis of DTA, it was confirmed that the exothermaic peaks at 715$^{\circ}C$ and 77$0^{\circ}C$ was clue to the crystallization of dried gel.

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Image Analysis of Surimi Sol and Gel in Composite System

  • Yoo, Byoung-Seung;Lee, Chong M.
    • Preventive Nutrition and Food Science
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    • v.3 no.3
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    • pp.292-294
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    • 1998
  • Surimi sol and gel were prepared by mixing egg albumin, starch, oil and carrageenan, which are used as representative ingredients in the surimi composite, at different ratio. Structural properties in surimi composite were investigated by examining the phase changes and dispersion pattern (average particle size, size range and the averge number of particle) of the particulate ingredients in sol and gel with an image analyzer. A staining technique of the specimen containing egg albumin in surimi gel was developed by adjusting pH of a toluidine staining solution. Image analysis revealed that size and density of ingredient particles were function of the level and dispersion of ingredients except of starch-incorporated surimi gel which showed maximum particle size at 6%.

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Effect of Co-dopant (Cr, Ti) in Zn2Si04:Mn Green Phosphors by Sol-Gel technique.

  • Ahn, Joong-In;Han, Cheong-Hwa;Park, Hee-Dong
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.840-844
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    • 2003
  • The main objective of this investigation is to improve the photoluminescent of $Zn_{2}SiO_{4}:Mn$ phosphors prepared by the sol-gel technique. We try to use adding a new co-dopan such as Cr and Ti. The calcination temperature of sol-gel technique(1100 $^{\circ}C$) was lower than that of the solid state reaction (1300 $^{\circ}C$). Under 147nm excitation, the maximum emission intensity was obtained when the concentration of Cr and Ti was 0.1mol% with respect to $Zn_{2}SiO_{4}:Mn$. In order to study the effect of co-dopant, the content of Mn and the ratio of water to TEOS were fixed at 2mol% and 36:1, respectively.

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Luminescence Properties of Low Temperature Sol-Gel Organic-inorganic Hybrid Films Contained Rare-earth Ions

  • Que, Wenxiu;Cheng, L.;Jia, C.Y.;Sun, M.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1181-1184
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    • 2008
  • $GeO_2$/ormosil organic-inorganic hybrid films doped with neodymium ions and $TiO_2$/Ormosil organic-inorganic hybrid films dispersed with neodymium oxide nanocrystals are prepared by combining an inverse microemulsion technique and a low-temperature sol-gel technique. The effects of $Nd^{3+}$ concentration, $Nd_2O_3$ nanocrystal content, and heat treatment temperature on up-conversion and photoluminescence luminescence properties of the hybrid films are studied.

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SOL-GEL PROCESSING AND MATERIAL SCIENCE

  • Korobova, N.E.;Soh, Deawha;Chu, Sun-Nam
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.477-480
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    • 1998
  • Sol-gel processing, which started some decades back as a laboratory curiosity, has proved to be a powerful and versatile technique for the synthesis of materials. The utility of the sol-gel method for producing glass and ceramic materials in the form of powders, fibers, thin films and bulk shapes with high purity, functional microstructures and potentially high chemical homogeneity at relatively low temperature (compared to conventional processing) has been discussed.

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Change of Luminescent Properties of Phosphors Through pH and Rw Control in Sol-gel Reaction (졸-겔반응에서 pH 및 Rw제어를 통한 Sr3-xMgSi2O8:EUx (0.01≤x≥0.1) 형광체의 발광특성 변화)

  • Ahn Joong-In;Han Cheong-Hwa;Kim Chang-Hae
    • Korean Journal of Materials Research
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    • v.15 no.6
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    • pp.419-425
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    • 2005
  • In this paper, we describe the luminescent properties of the phosphors synthesized via sol-gel technique. When the phosphor prepared by sol-gel technique, reaction factors, such as pH condition, $R_w$ and drying temperature affected the luminescent intensity, particle size and morphology of final product. Therefore, we attempt to control these reaction factors in order to improve the luminescent efficiency of phosphors. As a result of our study, when the acid catalyst (HCl) was used, emission intensity was higher than the case of base catalyst $(NH_4OH)$. The product prepared at $R_w=60$ indicated the maximum intensity. As the increase of the $R_w$ value, the particle was agglomerated and emission intensity was decreased. Finally, optimum drying temperature of gel was found to be$ 180^{\circ}C$.

The Effect of Far Infrared Radiation of $\beta$-Spodumene Glass-Ceramics Flims Coated on Iron Substrate by Sol-Gel Technique (졸-겔법에 의한 금속기판상의 $\beta$-spodumene 결정성유리의 박영도포와 원적외선상세성)

  • 양중식;신현택;박종옥
    • Journal of the Korean institute of surface engineering
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    • v.27 no.2
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    • pp.99-108
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    • 1994
  • Films of glass-ceramics $Li_2O-Al_2O_3-SiO_2$(LAS)system were prepared on substrate of an iron plate(SCP) by sol-gel technique using metal alkoxide such as Si$(OC_2H_5)_4$,Al$(OC_2H_9)_3$) and Ti$(OC_2H_6)_4$). Sol which was made by means of simple spray coating, on the substrate was hydrolyzed at 75~$80^{\circ}C$ in moisture cabinet (80~90 % humidity) to form the multicomponent gel. The films up to about 0.8~1.0$mu extrm{m}$ in thickness can be obtained by repeating operation, spraylongrightarrowhydrolysis and condensationlongrightarrowdryinglongrightarrowheating and crystallization at $700^{\circ}C$ for 3~5min. The far-infrared radiation spectra of the coated films on substrate were examined by FT-IR and of films was also observed by scanning electron micrograph technique. The thermal evaluation of the gel-film is followed by TG/DTA measurements. The structure evaluation is followedd X-ray diffraction. These results suggest that this process is applicable to far-infrared radiat at thin film technique.

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