• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.15-18
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• 2009

To enhance near UV-visible absorption region and to applied phosphor convert-white LEOs (PC-WLEDs), a red phosphor composed of ${Y_2}{SiO_5}:\;EU^{3+}$, $Bi^{3+}$ compounds was prepared by the conventional solid-state reaction. The photoluminescence (PL) shown that samples were excited by near UV light 395 nm for measurement of PL spectra. Emission spectra of samples have shown red emissions at 612 nm ($^5D_0{\to}^7F_2$). The enhanced near $UV{\sim}$ visible excitation spectrum with a broad band centered at 258 nm and 282 nm originated in the transitions toward the charge transfer state (CTS) due to the $Eu^{3+}-Bi^{3+}-O^{2-}$ interaction. The other excitation band at $350\;nm{\sim}480\;nm$, corresponding to the transitions $^7F_0{\to}^5L_9$ (364 nm), $^7F_0{\to}^5G_3$ (381 nm), $^7F_0{\to}^5L_6$ (395 nm), $^7F_0{\to}^5D_3$, (415 nm) and $^7F_0{\to}^5D_2$ (466 nm), occurred due to enhanced the f-f transition increasing $Bi^{3+}$ and $Eu^{3+}$ ions. The PL intensity increased with increased as concentration of $Bi^{3+}$ and the emission intensity becomes with a maximum at 0.125 mol.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.287-293
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• 2009

The passivation films with epoxy layer on LiF, $SiN_x$ and LiF/$SiN_x$ inorganic layer were fabricated on OLED to protect device from the direct damage of $O_2$ and $H_2O$ and to apply for a buffer layer between OLED device and passivation multi-layer with organic/inorganic hybrid structure as to diminish the thermal stress and expansion. Red OLED doped with 1 vol.% Rubrene in $Alq_3$ was used as a basic device. The device structure was multi-layer of ITO(150 nm) / ELM200_HIL(50 nm) / ELM002_HTL(30 nm) / $Alq_3$: 1 vol.% Rubrene(30 nm) / $Alq_3$(30 nm) / LiF(0.7 nm) / Al(100 nm). LiF/epoxy applied as a protective layer didn't contribute to the improvement of life time. While in case of $SiN_x$/epoxy, damage was done in the passivation process because of difference in heat expansion between films which could occur during the formation of epoxy film. Using LiF/$SiN_x$/epoxy improved lifetime significantly without suffering damage in the process of forming films, therefore, the best structure of passivation film with inorganic/epoxy layers was LiF/$SiN_x$/E1.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.615-619
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• 2019

Various fluorides, i.e., CaF₂, Na₃AlF₆, K₂SiF₆, MnF₃, MgF₂, were added to the flux cored wire, and their effects on the oxygen content of the weld metal were investigated. The investigation showed that the oxygen content of weld metal was not influenced by the type of metallic elements in the fluoride; rather, it was influenced by the stability of the arc during welding. While the wire containing MgF₂ showed the most stable arc and the least amount of oxygen in the weld metal, the wire containing MnF₃ showed the least stable arc and the greatest amount of oxygen. Since the deoxidation of the weld metal was not affected by the deoxidation elements, such as Ca and Mg, it was possible to predict the oxygen content of the weld metal by the equilibrium Si-Mn deoxidation thermodynamic model.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.65-66
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• 2000

Various fluoride films on a glass substrate were prepared and characterized to provide a seed layer for crystalline Si film growth. The XRD analysis on $CaF_2/glass$ illustrated (220) preferential orientation and showed lattice mismatch less than 5 % with Si. We achieved a fluoride film with breakdown electric field of 1.27 MV/cm, leakage current density about $10^{-6}$ $A/cm^2$, and relative dielectric constant less than 5.6. This paper demonstrates microcrystalline silicon $({\mu}c-Si)$ film growth by using a $CaF_2/glass$ substrate. The ${\mu}c-Si$ films exhibited crystallization in (111) and (220) planes, grain size of $700\;{\AA}$, crystalline volume fraction over 65 %, dark- and photo-conductivity ratio of 124, activation energy of 0.49 eV, and dark conductivity less than $4{\times}10^{-7}$ S/cm.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.149-153
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• 2001

Three-dimensional thermoluminescence(TL) spectra of LiF: Mg, Cu, Na, Si TL material based on temperature, wavelength and intensity were measured and analyzed. The glow curves were obtained by integration of luminescence intensity for wavelength at each temperature, and various trapping parameters related to the trap formation were determined by analyzing these curves. Computerized glow curve deconvolution(CGCD) method which based on general order kinetics(GOK) model were used for the glow curve analysis. The glow curves of LiF:Mg, Cu, Na, Si TL material were deconvoluted to six isolated glow curves which have peak temperature at 333 K, 374 K, 426 K, 466 K, 483 K and 516 K, respectively. The 466 K main glow peak had an activation energy of 2.06 eV and a kinetic order of 1.05. This TL material was also found to have three recombination centers, 1.80 eV, 2.88 eV and 3.27 eV by TL spectra analysis based on Franck-Condon model. It showed that 2.88 eV is the dominant center, followed by 3.27 eV level, and 1.80 eV center is ascertained as emission center of this material even though its very weak emission intensity.

• Journal of Radiation Protection and Research
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• v.26 no.1
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• pp.7-12
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• 2001

Sintered LiF:Mg,Cu,Na,Si thermoluminescence (TL) pellets were developed for application in radiation dosimetry. In the present study, the TL dosimetric properties of LiF:Mg,Cu,Na,Si TL pellets have been investigated for emission spectrum, dose response, energy response, and fading characteristics. LiF:Mg,Cu,Na,Si TL pellets were made by using a sintering process, that is, pressing and heat treatment from TL powders. Photon irradiations for the experiments were carried out using X-ray beams and a $^{137}Cs$ gamma source at the Korea Atomic Energy Research Institute (KAERI). The average energies and the dose were in the range of 20-662 keV and $10^{-6}-10^{-2}\;Gy$, respectively. The glow curves were measured with a manual type TLD reader(System 310, Teledyne) at a constant nitrogen flux and a linear heating rate. For a constant heating rate of $5^{\circ}C\;s^{-1}$, the main dosimetric peak of glow curve appeared at $234^{\circ}C$, the activation energy was 2.34 eV and frequency factor was $1.00{\times}10^{23}$. TL emission spectrum is appeared at the blue region centered at 410 nm. A linearity of photon dose response was maintained up to 100 Gy. The photon energy responses relative to $^{137}Cs$ response were within ${\pm}20%$ at overall photon energy region. The fading of TL sensitivity of the pellets stored at the room temperature was not found for one year.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.570-574
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• 2011

Large colorless single crystals of analcime with diameters up to 0.20 mm have been synthesized from gels with the composition of $3.00SiO_2$ : $1.50NaAlO_2$ : 8.02NaOH : $454H_2O$ : 5.00TEA. The fully $Na^+$-exchanged analcime have been prepared with aqueous 0.1 M NaCl (pH adjusted from 6 to 11 by dropwise addition of NaOH). The single-crystal structure of hydrated $|Na_{0.94}(H_2O)|[Si_{2.06}Al_{0.94}O_6]$-ANA per unit cell, a=13.703(3) ${\AA}$, has been determined by single-crystal X-ray diffraction technique in the orthorhombic space group Ibca at 294 K. The structure was refined using all intenties to the final error indices (using only the 1,446 reflections for which $F_o$ > $4{\sigma}(F_o))R_1/wR_2$ = 0.054/0.143. About 15 $Na^+$ ions are located at three nonequivalent positions and octahedrally coordinated. The chemical composition is $Na_{0.94}(H_2O)Si_{2.06}Al_{0.94}O_6$. The Si/Al ratio of synthetic analcime is 2.19 determined by the occupations of cations, 14.79, in the single-crystal determination work.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.224-225
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• 2006

The Ethylene polymerization behavior of a series of polymethylene bridged dinuclear CGC $[Zr({\eta}^{5}:{\eta}^{1}-C_{9}H_{5}SiMe_{2}NCMe_{3})Me_{2}]_{2}[(CH_{2})_{n}]\;[_{n}=6(1),\;9(2),\;12(3)]$ in the cocatalytic activation with $Ph_{3}C^{+}B^{-}(C_{6}F_{5})_{4}\;(B_{1})\;or\;Ph_{3}C^{+}(C_{6}F_{5})_{3}B^{-}C_{6}F_{4}B^{-}(C_{6}F_{5})_{3}Ph_{3}C^{+}\;(B_{2})\;or\;B(C_{6}F_{5})_{3}\;(B_{3})$ were investigated to study the nuclearity effects as well as the counteranion effects. The ethylene polymerization and ethylene/1-hexene copolymerization were conducted at $30^{\circ}C$ It was found that both in ethylene polymerization and ethylene/1-hexene copolymerization, activities increased in the order of 1 < 2 < 3, which indicates the presence of longer bridge between two active sites contributes more efficiently to facilitate the polymerization activity.

• Journal of the Korean Society of Radiology
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• v.9 no.3
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• pp.169-174
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• 2015

$LiGd_9(SiO_4)_6O_2:Ce^{3+}$ phosphors were synthesized by solid-state reaction method. The structural characteristic was investigated by X-ray powder diffraction analysis. The emission and excitation spectra of the $Ce^{3+}$ ions doped $LiGd_9(SiO_4)_6O_2$ phosphors were obtained under the UV excitation. The emission spectra of $LiGd_9(SiO_4)_6O_2:Ce^{3+}$ shows the band at 410 nm corresponding to the $^2F_{5/2}$ and $^2F_{7/2}$ states of $Ce^{3+}$. The red shift of $Ce^{3+}$ emission is found as the $Ce^{3+}$ concentration increases, which could be explained by the change in crystal-field symmetry and strength with increasing $Ce^{3+}$ concentration. Fluorescence decay time of $Ce^{3+}$ was about 20 ns. When the concentration of $Ce^{3+}$ increases life time was slightly reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.926-933
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• 2012

Phosphoric acid used for the production of phosphate fertilizers is synthesized by the reaction of phosphate rock and sulfuric acid. As the reaction is exothermic, yield of phosphoric acid is poor at elevated temperature. Therefore, enhancement in its yield requires the process temperature be maintained by releasing the vapor ($80^{\circ}C$) containing HF and SiF4 through a vacuum cooler. However, these valuable resources; Fand Si, which can be utilized for the manufacture of refrigerant and polysilicon, respectively, are being wasted in the treatment process. We performed lab-scale experiments to estimate the amount of recoverable H2SiF6, a by-product of phosphoric acid manufacturing process. The experimental results showed a decrease of fluorine concentration by 0.12wt% in the liquid phase. Preliminary estimation showed a possible recovery of 5,509 ton/yr of fluorine considering the scale of the fertilizer manufacturing plant. Furthermore, field-scale experiment showed that H2SiF6 could be enriched in liquid phase from 0.35wt% to 7.33wt% and the vapor flow-rate from vacuum cooler was estimated at $51,000m^3/hr$. Anew, the efficiency of fluorine recovery in the pilot-scale experiment was found to be 76.74% and the production of H2SiF6 was estimated at 5,340 ton/yr.