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2006, Vol.16, No.1

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    The identification of amethyst origins by using FT-IR, UV-VIS spectrum analysis

    YON SEOG JOO | 윤시내 | 2006, 16(1) | pp.25~31 | number of Cited : 0
    Abstract PDF
    Many amethysts of diferent origins such as South America, Aftrica, and Asia were compared. According toICP-AES analysis, the colorizing elements were Fe, Cr, Cu, and Co. Amethysts from South America showed higherconcentrations of the elements. UV-VIS analysis showed that both natural and synthetic amethysts were characterized bysynthetic amethysts. According to FT-IR analysis, the synthetic amethysts were distinguished from the natural amethysts inthat they had a typical absorption band of 3543 cm1. The amethyst from South America showed strong absorption bandsof 3584 cm1 and 3435 cm1, and African amethyst had absorption bands of 329 cm1 and 3196 cm1. 3381 cm1 absorptionband was shown strongly for Asian origins.Key words Amethyst, ICP-AES, UV-VIS, FT-IR, SyntheticFT-IR, UV-VIS ..... .. .......†.. ........ ..... , .. , 520-714(2006. 1. 9. .. )(2006. 2. 1. .... ). . .. , .... , ... ... .... .... ... . ICP-AES .... ... ..... Fe, Cr, Cu,Co.. ..... .. .... ..... .... .. .... . UV-VIS .... ...... ......350 nm ... 550 nm .... .... .... ... .... .... ... .. ... .. .... . FT-IR .
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    Photoluminescent and low voltage cathodoluminescent properties of LaNbO4 : X (X = Bi, Eu)phosphors

    Kim Youhyuk | 온지원 | 2006, 16(1) | pp.32~37 | number of Cited : 0
    Abstract PDF
    Rare-earth niobates, LnNbO4 (Ln = Y, La, Gd) are well-known self-activated phosphors due to charge transfer inNbO43 showing a broad and strong emission band in the spectral region around 410 nm. In order to find new blue and redphosphors for FED, LaNbO4 : X (X = Bi, Eu) phosphors are prepared through solid-state reactions at high temperature.at 1250oC for 2 h followed by second firing at 1400oC for 1 h. Under irradiation at 254 nm, 1 mol% Bi3+ doped LaNbO4phosphor shows strong blue emission band with a range of 420~450 nm. Also 10 mol% Eu3+ doped LaNbO4 phosphorshows the maximum emission intensity at about 610 nm. Emission peaks at 415~460 nm, 530~560 nm and 570~620 nm areobserved in phosphors below 10 mol% Eu3+ doped LaNbO4. Similar results are obtained in cathodoluminescent property ofthese phosphors.Key words Low voltage cathodoluminescent, Photoluminescent, Lanthanide niobates, FED, Solid state reaction, Phosphor,Excitation spectrum, Emission spectrumLaNbO4 : X (X = Bi, Eu) .... .. . . .. ... .. ....... ...†..... .... ... , ...... ... , .. , 330-714(2005. 10. 5. .. )(2005. 12. 27. .... ). . .... niobates. LnNbO4(Ln = Y, La, Gd). .. ..... NbO43 ... .. ... .. .. .. .. .. ..... 410 nm.. .... . . ..... ... FED. .. . .. .... .... ... LaNbO4 :X (X = Bi, Eu) .... ...... , 1250oC.. 2.. ... . 1400oC.. 1.. ..... . .. ....... . ... . 254 nm. ..... LaNbO4 : Bi. 420~450 nm .... .. .. .. ..... .... ...Bi3+ .. ... 1mol%. . .. ..... ... . LaNbO4 : Eu. ... ... Eu3+ .. ... 10 mol% . . .610 nm.. .. .. .. ..... .... .. . Eu3+ .. ... 10 mol% ..... 415~460 nm, 530~560 nm .570~620 nm .... ... .... .. . .. .... ... ..... . .. ... ... ... ... .1. . .
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    Computer aided simulation of spark plasma sintering process (Part 1 : formulation)

    Young Tag Keum | 전종훈 | 2006, 16(1) | pp.38~42 | number of Cited : 0
    Abstract PDF
    Spark plasma sintering processes have been rapidly introduced recently to improve the quality and productivity of ceramic products and to solve the problem of environmental pollutions. Sintering temperatures and pressing pressures in the spark plasma sintering process are known to be the important factors highly affecting the quality of the ceramics. In this research, in order to see the effects of sintering temperatures and pressing pressures on the grain growth during the spark plasma sintering process of Al2O3, the grain growth processes associated with sintering temperatures and pressing pressures are simulated by the Monte Carlo method (MCM) and the finite element method (FEM). In this Part 1, the formulations for the simulation, which is the theoretical background of Part 2, are introduced.럭
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    Computer aided simulation of spark plasma sintering process (Part 2 : analysis)

    Young Tag Keum | Jung, Sang Chul | 전종훈 | 2006, 16(1) | pp.43~48 | number of Cited : 0
    Abstract PDF
    In this Part 2, the grain growth processes of Al2O3 ceramics is numerically simulated using Monte Carlo method (MCM) and finite element method (FEM) and the pore sizes are analyzed. As the green ceramics whose thermal conductivities in high temperatures are generally low are sintered by the plasma heat and are rapidly cooled, the grain growth of the sintered body in the center is different from that in the outer. Also, even in the same sintering temperature, the pore size differs according to the pressing pressure. In order to prove the difference, the temperature distribution of the sintered body was analyzed using the finite element method and then the grain growth process associated with pressing pressures and relative densities was simulated using Monte Carlo method.