• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.169-175
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• 2014

Digital ink-jet printing system has many advantages such as fast and fine printing of various images, high efficiency and low cost process. Generally digital ink-jet printing requires ceramic pigments of cyan, magenta, yellow and black with thermal and glaze stability above $1000^{\circ}C$ for the application of porcelain product design. In this study, pink-red colored $CaO-SnO_2-Cr_2O_3-SiO_2$ pigment was synthesized using solid state reaction. The synthesis conditions of $Ca(Cr,Sn)SiO_5$ pigment such as annealing temperature, amount of mineralizer and non-stoichiometric composition were optimized. Crystal structure and morphology of the obtained $Ca(Cr,Sn)SiO_5$ pigment were analyzed using XRD, SEM, PSA, FT-IR and effect of Cr substitution on the pigment color was analyzed using Uv-vis. spectrophotometer and CIE $L^*a^*b^*$ measurement.

• Clean Technology
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• v.19 no.2
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• pp.165-172
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• 2013

In this study, the hydrogen chloride removal using K-based dry sorbents ($K_2CO_3/Al_2O_3$, KEPRI, Korea) was studied with varying the pressure in a fixed bed reactor (15 cm tall bed with 0.5 cm I.d.). Working temperature was $400^{\circ}C$ and feed gas concentration was 750 ppm (HCl vol%, $N_2$ balance). The chloride sorption capacity of sorbent increases with increasing pressure (1, 5, 10, 15 and 20 bar). Also, after forming KCl crystal by reaction with $K_2CO_3$ and HCl, owing to the strong bonding energy, sorbent regeneration was practically impossible. Its optical, physical and chemical characterizations were evaluated by SEM, EDAX, BET, TGA and XRD. At $400^{\circ}C$ and 20 bar condition, working condition for the dehalogenation process after gasification, K-based dry sorbent showed high HCl sorption capacity and HCl/$N_2$ separation performances comparing with Ca-based and Mg-based dry sorbents.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.52-59
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• 2000

The reaction gel mixtures of molar composition (0.3${\sim}$2.1) $SiO_2:\;(0.10{\sim}0.50)\;CTABr:\;0.15{\sim}0.23)\;TMAOH:\;(20{\sim}100)\;H_2O$ we prepared and then aged at room temperature for a definite duration. The aged gel is reacted hydrothermally at $150^{\circ}C$ for 2 days. The pH of reaction gel during synthesis is strongly influenced by the concentration of TMAOH and silica source. The pH change affects the phase of product, which is monitored by X-ray diffractometer. With increasing the TMAOH ratio from 0.19 to 0.23, the gel becomes more basic, and the product involves more lamellar phase. At TMAOH ratio lower than 0.19, the hexagonal phase is lower with decrease of pH. The content of the lamellar phase increases at a lower $SiO_2$ concentration, and higher concentrations have a clear detrimental effect on the crystallinity ofMCM-41 due to an excess silica source. The best quality MCM-41 is synthesized from a reaction gel composition of $1.0\;SiO_2:\;0.27\;CTABr:\;0.19\;TMAOH:\;40\;H_2O$. The pH values of this gel, aged one for 24 hr, and reacted one at $150^{\circ}C$ for 2 days are 12.3, 11.5, and 10.5, respectively. Gel aging for 24 h is essential for preparing high quality MCM-41. Longer aging causes a decrease of hexagonal phase.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.199-204
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• 2011

$(YSmNd)_{1.8}Ba_{2.4}Cu_{3.4}O_{7-x}$ [(YSN)1.8] high $T_c$ superconductor was directionally grown by zone melt growth process, in air atmosphere. In this study, optimum melting temperature and growth rate were $1100^{\circ}C$ and 3.5 mm/hr, respectively. The microstructure of well-textured (YSN)1.8 samples were examined by XRD, optical microscopy, TEM and SQUID magnetometer. The critical current density of these samples were measured by the direct transporting current method. In the observation using an optical microscopy, nonsuperconducting $(YSmNd)_2BaCuO_5$[(YSN)211] inclusions of (YSN)1.8 superconductor uniformly distributed within the superconducting (YSmNd)$Ba_2Cu_3O_x$[(YSN)123] matrix. The directionally melt-textured (YSN)1.8 superconductor showed an onset $T_c{\geq}90\;K$ and sharp superconducting transition. The transport $J_c$ values were 830 A and $3.93{\times}10^4$ (A/$cm^2$) at 77 K self-field, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.89-93
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• 2017

GaN single crystals were grown by controlling of various processing parameters such as growing temperature, V/III ratio and growing rate. We optimized thickness of bulk GaN single crystal by analyzing defect of surface and inside of the GaN single crystal for application to high brightness and power device. 2-inch bulk GaN single crystals were grown by HVPE (hydride vapor phase epitaxy) on sapphire and their thickness was 0.3~7.0 mm. Crystal structure of the grown bulk GaN was analyzed by XRD (X-ray diffraction). The surface characteristics of the grown bulk GaN were observed by OM (optical microscope) and SEM (scanning electron microscopy) with measuring EPD (etch pits density) of the GaN crystals.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.453-458
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• 2009

Iron-containing TNU-9 zeolites were prepared by aqueous ion exchange in the range of Fe contents 0.6~3.3 wt%. Direct decomposition of $N_2O$ was performed varying $N_2O$ concentrations and reaction temperatures. Fe-TNU-9 zeolites used were characterized using XRD, $N_2$ sorption, SEM/EDX. A 2.7 wt% Fe-TNU-9 zeolite showed high activities and above this contents of Fe the effect of catalytic activity was little dominated. Fe-TNU-9 zeolites after ion exchange conserved their TNU-9 structure although the degree of crystallinity was decreased until ca. 60% in 3.1 wt% Fe-TNU-9 zeolite after ion exchange in 0.01 M Fe solution. The decrease in the degree of crystallinity could be correlated with the decrease of surface area and pore volume. The partial reaction order of $N_2O$ in the decomposition of $N_2O$ was dependent on the reaction temperature from 0.69 at $420^{\circ}C$ to 0.97 at $494^{\circ}C$. The activation energy of $N_2O$ was also dependent on the $N_2O$ concentration and its value is ranged to 34~43 kcal/mol.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.413-421
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• 2005

This study focused on the decomposition of toluene in a plasma-photocatalytic hybrid system. Hexagonally packed meso-structured Mn-titanosilicates (Mn-Ti-MCM-41), as the photocatalysts, have been prepared by the hydrothermal method. The physical properties of the photocatalysts were characterized using XRD, XPS, TEM, BET/ICP, and $NH_3$/Toluene-TPD. Experiments were carried out at the applied voltage of 9.0 kV and at room temperature of $20^{\circ}C$. In the plasma only system, the activity of the toluene decomposition was higher than that in the photocatalytic system. However, the amount of by-products, such as phenol, $C_2{\sim}C_4$ alkene, was also increased in the plasma only system. However, the by-products decreased remarkably in a plasma-photocatalytic hybrid system. When Mn5mol%-Ti-MCM-41 was used as a photocatalyst in a plasma-photocatalytic hybrid system, the $CO_2$ selectivity in products was increased dramatically compared to other catalysts. It was confirmed that a plasma-photocatalytic hybrid system was better for toluene decomposition compared to photocatalytic and plasma only systems.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.589-594
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• 2006

The recycling of industrial wastes in the concrete manufacturing is of increasing interest worldwide, due to the high environmental impact of the cement and concrete industries and to the rising demand of infrastructures, both in industrialized and developing countries. The production of municipal wastes in the South Korea is estimated at about 49,902 ton per day and only 14.5% of these are incinerated and principally disposed of in landfill. These quantities will increase considerably with the growth of municipal waste production, the progressive closing of landfill, so the disposal of municipal solid waste incinerator(MSWI) ashes has become a continuous and significant issue facing society, both environmentally and economically. MSWI ash is the residue from waste combustion processes at temperature between $850^{\circ}C\;and\;1,000^{\circ}C$. And the main components of MSWI ash are $SiO_2,\;CaO\;and\;Al_2O_3$. The aim of this study is to find a way to useful application of MSWI ash(after treatment) as a structural material and to investigates the hydraulic activity, compressive strength development composition variation of such alkali-activated MSWI ashes concrete. And it was found that early cement hydration, followed by the breakdown and dissolving of the MSWI-ashes, enhanced the formation of calcium silicate hydrates(C-S-H). The XRD and SEM-EDS results indicate that, both the hydration degree and strength development are closely connected with a curing condition and a alkali-activator. Compressive strengths with values in the 40.5 MPa were obtained after curing the activated MSWI ashes with NaOH+water glass at $90^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.370-374
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• 2004

Sr$_{l-x}$Ba$_{x}$Al$_2$O$_4$:Eu (x = 0, 0.1, 0.2, and 0.3 mol) phosphor was synthesized by the hydrothermal method and its properties of photoluminescence and long-afterglow were investigated. The mixtures of Sr(NO$_3$)$_2$, Al(NO$_3$)$_3$9$H_2O$, and Eu(NO$_3$)$_3$$.$6$H_2O$ salts dissolved in distilled water, after controlling their pH by NH$_4$OH solution, put into an Autoclave reactor with high temperature and pressure to react. Such synthesized SrAl$_2$O$_4$:Eu powders showed homogeneous and ultra-fine particles of sub-micron size. In order to have the photoluminescence characteristic, powders were heat treated at 1100 -140$0^{\circ}C$ for 2 h in Ar/H$_2$ reduction atmosphere. Photoluminescence spectra showed a excitation along the wide wavelength of 250 ∼ 450 nm, and broaden emission with maxima peak at 520 nm. Also, it showed a good long afterglow with decaying over 1000 sec after excitation illumination for 10 min. In addition, the microstructure and crystal structure of SrAl$_2$O$_4$:Eu powders were investigated by an SEM and XRD, respectively.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.7-13
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• 2007

We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.