• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.36-39
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• 2002

Polycrystalline silicon (poly-Si) thin film transistor (TFT) technology is emerging as a key technology for active matrix liquid crystal displays (AMLCD), allowing the integration of both active matrix and driving circuit on the same substrate (normally glass). As high temperature process is not used for glass substrate because of the low softening points below 450$^{\circ}C$. However, high temperature process is required for getting high crystallization volume fraction (i.e. crystallinity). A poly-Si thin film transistor has been fabricated to investigate the effect of high temperature process on the molybdenum (Mo) substrate. Improve of the crystallinity over 75% has been noticed. The properties of structural and electrical at high temperature poly-Si thin film transistor on Mo substrate have been also analyzed using a sputtering method

• Journal of the Korean Ceramic Society
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• v.27 no.4
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• pp.521-528
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• 1990

Li2O.2SiO2 glass-ceramics were made from the melt by the nucleation and growth treatment. The optimum nucleation temperature and time were determined from DTA curves of as-quenched and thermally treated glasses, and found to be 44$0^{\circ}C$ and 3hrs. The optical microscopic technique was also used to support this result. The volume fractions of crystals present in the partially crystallized specimens were measured using the optical microscopy and the amorphous X-ray scattering methods. The degree of crystallization increased with increasing the crystallization temperature and time. The crystalline phase identified by X-ray diffraction was lithium disilicate. As the crystallinity increased up to 95%, the transmittance of glass-ceramics was decreased linearly. It was also found that for the same heat treatment condition (575$^{\circ}C$, 30min), a thicker specimen showed higher transmittance, presumably due to less crystallinity.

• Carbon letters
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• v.7 no.2
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• pp.87-96
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• 2006

This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.406-412
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• 2017

$70V_2O_5-10Fe_2O_3-13P_2O_5-7B_2O_3$ glasses were prepared to study the electrical conductivity and catalytic properties of the structural change with crystallization. The structural changes were analyzed by determining the molecular volume from the sample density; using X-Ray Diffraction (XRD) analysis, which indicated that $V_2O_5$, $VO_2$ and $B_2O_3$ crystals in heat-treated more than 1h samples. Especially a new crystalline phase of non-stoichiometric $Fe_{0.12}V_2O_5$ was formed after 6 h heat treatment. The V-O bonding change after crystallization was analyzed by Fourier Transform Infrared Spectroscopy (FTIR); V ion change from $V^{5+}$ to $V^{4+}$ was shown by XPS. Conductivity and catalytic properties were examined based on the polaronic hopping of V and Fe ions, which exhibited different valence states with crystallization.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.238-241
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• 2010

The purification of indole from 54.3wt% indole fraction (temperature range of distillate: $250{\sim}255^{\circ}C$) recovered by extraction-distillation combination of coal tar fraction (temperature range of distillate: $240{\sim}265^{\circ}C$) was examined by solute crystallization. The feed consists of eight components such as quinoline, iso-quinoline, indole, quinaldine, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl and phenyl ether. Hexane and an aqueous solution of methanol (50 : 50 vol%) were used as the crystallization solvent and the coolant, respectively. A batch stirred tank of glass material was used as a crystallization apparatus. By increasing the operation temperature and the volume ratio of solvent to feed at initial, the purity of indole increas ed, but yields of indole showed a decreasing tendency. Solute crystallization method using hexane as a solvent was excellent because the purity of 99.3 wt% indole was recovered at the yield of 50% without washing operation.

• Journal of Korean Society on Water Environment
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• v.23 no.1
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• pp.138-143
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• 2007

This study goes in for the observation of the characteristics of nitrogen removal from swine wastewater by struvite crystallization. In addition, the struvite formation potential in supernatants after struvite crystallization was investigated. In the study for nitrogen removal by struvite crystallization, the effects of pH and molar ratio of magnesium (Mg) injected using bittern as Mg source were investigated. Also, the potential of struvite formation in the supernatant with amount of Mg added was carefully observed. As the results, the optimum pH in the removal of nitrogen was 8.8 and sludge volume was increased as pH was raised from 7 to 12 under the condition that the molar ratio of $Mg^{2+}$ to ${NH_4}^+$-N to ${PO_4}^{3-}$-P was 1:1:1. An optimum removal efficiency of ammonia-N was observed at 1 molar ratio of Mg to ${NH_4}^+$-N, showing no further increase at over 1 molar ratio and dramatical deterioration at under 1 molar ratio. However, the sludge volume was increased by increasing the molar ratio of Mg. In the experiments for the potential of struvite formation in the supernatants, initial -log([$Mg^{2+}$][${NH_4}^+$][${PO_4}^{3-}$]) value was much lower than $pK_{sp}$ and gradually reached $pK_{sp}$ at 2 days, as the molar ratio of Mg increased over 1.2. At 31 days, -log([$Mg^{2+}$][${NH_4}^+$][${PO_4}^{3-}$]) value was returned to the initial value. In addition, the supernatants had a potential precipitation of hydroxylapatite due to calcium contained in bittern, $K_2Mg(SO_4)_3$ and $K_3Na(SO_4)_2$ resulting from the decrease of sodium and potassium in supernatants formed after struvite crystallization as times go by. Based on the results, it appears that some retention time and proper dosage of Mg may be needed for the prevention of scale in pipe line.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.130-135
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• 2003

Polycrystalline silicon thin films have been used for low cost thin film device application. However, it was very difficult to fabricate high performance poly-Si at a temperature lower than $600^{\circ}C$ for glass substrate because the crystallization process technologies like conventional solid phase crystallization (SPC) require the number of high temperature (600-$1000^{\circ}C$) process. The objective of this paper is to grow poly-Si on flexible substrate using a rapid thermal crystallization (RTC) of amorphous silicon (a-Si) layer and make the high temperature process possible on molybdenum substrate. For the high temperature poly-Si growth, we deposited the a-Si film on the molybdenum sheet having a thickness of 150 $\mu\textrm{m}$ as flexible and low cost substrate. For crystallization, the heat treatment was performed in a RTA system. The experimental results show the grain size larger than 0.5 $\mu\textrm{m}$ and conductivity of $10^{-5}$ S/cm. The a-Si was crystallized at $1050^{\circ}C$ within 3min and improved crystal volume fraction of 92 % by RTA. We have successfully achieved a field effect mobility over 67 $\textrm{cm}^2$/Vs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.632-635
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• 2001

Microcrystalline Si films have been deposited by using five W-wire filaments of 0.5 mm diameter for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD grown films with the film exposed to transformer couple plasma system for the modification of seed layer. W-wire filament temperature was maintained below 1600$^{\circ}C$ to avoid metal contamination by thermal evaporation at the filament. Deposition conditions were varied with H$_2$dilution ratio, with and without plasma treatment. From the Raman spectra analysis, we observed that the film crystallization was strongly influenced by the H$_2$dilution ratio and weakly depended on the distance between the wire and a substrate. We were able to achieve the crystalline volume fraction of about 70% with an SiH$_4$/H$_2$ratio of 1.3%, a wire temperature of 1514$^{\circ}C$, a substrate separation distance of 4cm, and a chamber pressure of 38 mTorr. We investigated the influence of ${\mu}$c-Si film properties by using a plasma treatment. This article also deals with the influence of the H$_2$dilution ratio in crystallization modification.

• BMB Reports
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• v.31 no.6
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• pp.600-603
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• 1998

A highly thermostable xylose isomerase from Thermus thermophilus has been expressed in Escherichia coli and crystallized. The purified enzyme shows its optimum temperature at $90^{\circ}C$. It has been crystallized at room temperature using polyethylene glycol 4000 as the precipitant. The crystal belongs to the orthorhombic space group $P2_12_12_1$, with unit cell parameters of a = 73.34 ${\AA}$, b = 144.05 ${\AA}$, c = 155.07 ${\AA}$. The presence of one molecule of tetrameric xylose isomerase in the asymmetric unit gives a crystal volume per protein mass ($V_m$) of 2.32 ${\AA}^3/Da$ and the solvent content of 47.0% by volume. The diffraction pattern extends to 1.9 ${\AA}$ Bragg spacing with synchrotron radiation and a set of native data has been collected to 2.3 ${\AA}$.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.13-20
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• 1989

After sintering Si3N4 containing 20wt% of variable composition ratio of Y2O3 and Al2O3 at 1$600^{\circ}C$, the specimens were annealed at 125$0^{\circ}C$ and 135$0^{\circ}C$ for 5, 10, 15 hours in order to crystallize the remanining oxynitride glass phases. The main grain-boundary crystalline phases in the Si3N4-Y2O3-Al2O3 system were melilite and YAG. By annealing 15hrs. at 125$0^{\circ}C$, almost all of the glasses were crystallized. During the growth of melilite, lattice volyume of $\beta$-Si3N4 was increased as Al3+ and O2- ions in the oxynitride glass diffuse into $\beta$-Si3N4 lattice, but during the growth of YAG, lattice volume of $\beta$-Si3N4 was decreased by reverse diffusion of Al3+ and O2- ions. In case of crystallization of glass phase to melilite, thermal expansion of sample was decreased, but in case of crystallization to YAG, inverse phenomen on was observed.