• Electrical & Electronic Materials
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• v.10 no.2
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• pp.141-149
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• 1997

L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders were prepared by both GNP(Glycine-Nitrate Process) and solid state reaction method in various of calcination temperature(800-1000.deg. C) and time in air. Also, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contacts on YSZ(Yttria-Stabilized Zirconia) substrate were prepared by screen printing and sintering method as a function of sintering temperature(1100-1450.deg. C) in air. Sintering behaviors have been investigated by SEM(Scanning Electron Microscope) and porosity measurement. Compositional and structural characterization were carried out by X-ray diffractometer and ICP AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Electrical characterization was carried out by the electrical conductivity with linear 4 point probe method. As the calcination period increased in solid state reaction method, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ phase increased. Although L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ single phase was obtained only for 48hrs at 1000.deg. C, in GNP method it was easy to get single and ultra-fine L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders with submicron particle size at 650.deg. C for 30min. The particle size and thickness of L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contact by solid state reaction method did not change during the heat treatment, while those by GNP method showed good sintering characteristics because initial powder size fabricated from GNP method is smaller than that fabricated from solid state reaction method. Based on enthalpy change from thermodynamic data and ICP-AES analysis, it was suggested to make cathode contact in composition of (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$ Mn $O_{3}$ which have little second phase (L $a_{2}$Z $r_{2}$ $O_{7}$) for high efficient solid oxide fuel cells applications. As (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$Mn $O_{3}$ cathode contact on YSZ substrate was sintering at 1250.deg. C the temperature that liquid phase sintering did not occur. It was possible to obtain proper cathode contacts with electrical conductivity of 150(S/cm) and porosity content of 30-40%.m) and porosity content of 30-40%.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.167-173
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• 2014

The adsorption characteristics of the pellet-type adsorbent prepared from water treatment sludge for trimethylamine and ammonia were studied. The surface area and pore volume of the pellet-type adsorbent increased during calcination at $500^{\circ}C$. It was confirmed that the adsorbent prepared from water treatment sludge contained Br$\ddot{o}$nsted and Lewis acid sites. The breakthrough time of the adsorbent for both trimethylamine and ammonia was measured at different adsorbent weights and linear velocities while maintaining constant amounts of trimethylamine and ammonia. The kinetic saturation capacity and the adsorption rate constant for trimethylamine and ammonia were determined at different linear velocities by using the Wheeler equation. It was found that the kinetic saturation capacity and the adsorption rate constant were dependent on the linear velocity. An experimental equation could be derived to predict the breakthrough time of the adsorbent prepared from water treatment sludge for trimethylamine and ammonia at different adsorption conditions.

• Resources Recycling
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• v.3 no.3
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• pp.21-26
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• 1994

In present study an attempt has been made to extract the high purity $Al_2O_3$from domestic aluminous shale. The processes of the salt roasting with ammonium sulfate, extraction with sulfuric acid and calcination were adopted. In the extraction of alumina, the effects of the sulfuric acid concentration, the reaction time and the temperature has been investigated. The reaction products were analyzed by X-ray diffraction, DTA-TG, chemical analysis and SEM. The results are summerized as follows: 1)The pretreatment conditions were 0.6M-$(NH_4)_2SO_4$and $650^{\circ}C$ in sintering temperature. 2) The optimum extraction conditions were $10%-H_2SO_4$ and 240 minutes in acid treating time. 3)Physical properties of sintering materials were confirmed as $\alpha-Al_2O_3$ by X-ray diffraction method and the purity of $\alpha-Al_2O_3$ was 99.23%.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.247-259
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• 2008

$TiO_2$ coatings on kaolinite powders by sol-gel method were carried out using mixture of titanium isopropoxide, ethanol as solvent, HCl as a catalyst and $H_{2}O$ for hydrolysis. The mole ratio of reaction mixture, stirring time. aging time, crystallization time and crystallization temperature influenced to the crystallization of $TiO_2$ coated on kaolinite and metakaolinite Powders. Optimum condition for $TiO_2$ coatings on kaolinite was as follows; TIP 0.1 mol, $H_{2}O$ 0.15 mol, HCl 0.005 mol, ethanol 100 ml, raw kaolinite 50 g, stirring time 4 hrs, aging time 24 hrs, crystallization time 2 hrs and crystallization temperature $1050^{\circ}C$. The crystallinity of the anatase under optimum condition was about 17.61%. The anatase crystallinity of the $TiO_2$ coated on raw kaolinitc powders (17.61% at $1050^{\circ}C$) was higher at the lower calcination temperature compared with metakaolinite (17.39% at $1200^{\circ}C$).

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.208-213
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• 2013

Zirconium hydroxide was synthesized by varying the aging time of the zirconyl chloride octahydrate at $100^{\circ}C$ in aqueous solution and the resulting hydroxides were calcined at $700^{\circ}C$ for 6 h to obtain the crystalline $ZrO_2$. The materials used in this study were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), $N_2$-sorption, transmission electron microscopy (TEM), $NH_3$ temperature-programmed desorption ($NH_3$-TPD), $CO_2$-TPD and iso-propanol TPD analyses to correlate with catalytic activity for the dehydration of iso-propanol. The pure tetragonal $ZrO_2$ phase was obtained after 24 h aging of zirconium hydroxide and successive calcination at $700^{\circ}C$. The increase of aging time showed the production of smaller particle size $ZrO_2$ resulting that the higher specific surface area and total pore volume. $NH_3$-TPD results revealed that the relative acidity of the catalysts increased along with the increase of aging time. On the other hand, the results of $CO_2$-TPD showed the reverse trend of $NH_3$-TPD results. The best catalytic activity for the dehydration of iso-propanol to propylene was shown over $ZrO_2$ catalyst aged for 168 h which had the highest $S_{BET}$ ($178\;m^2\;g^{-1}$). The catalytic activity could be correlated with high surface area, relative acidity and easy desorption of iso-propanol.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.59-70
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• 1991

ZnO fine powder was prepared by the batch precipitation process using $ZnCl_2$ and hexamethylenetetramine solution as a mother solution. When the concentrations of $ZnCl_2$solution were $0.1mol/\ell$ and 0.05mol/-, the particles of rod shape were obtained when the conentration of $ZnCl_2$solution was $0.01mol/\ell$, the particle of plate shape was obtained. When the hexamethylenetetramine as a precipitants was used, pH was raised slow during a few minute be-cause of slow hydrolysis rate of hexamethylenetetramine. For rapid raising of pH during initial reac-tion time, $NH_4$OH was added as nucleant. When $NH_4$OH as a nucleant was added, obtained particle was shape of granular and the mean particle size was $0.41\mu\textrm{m}$. After calcination at $500^{\circ}C$ during 1hour, all of remained organic phase was removed but the shape of particles was not changed. But pa-rticles were slightly shrunk in comparision with before calcined particles.

• Carbon letters
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• v.22
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• pp.48-59
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• 2017

This study synthesized pure anatase carbon doped $TiO_2$ photocatalysts supported on a stainless steel mesh using a sol-gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide (DMF)/$TiCl_4$. The influence of the pyrolysis temperature and holding time on the morphological characteristics, particle sizes and surface area of the prepared catalyst was investigated. The prepared catalysts were characterized by several analytical methods: high resolution scanning electron microscopy (HRSEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The XRD patterns showed that the supported $TiO_2$ nanocrystals are typically anatase, polycrystalline and body-centered tetragonal in structure. The EDS and XPS results complemented one another and confirmed the presence of carbon species in or on the $TiO_2$ layer, and the XPS data suggested the substitution of titanium in $TiO_2$ by carbon. Instead of using calcination, PAN pyrolysis was used to control the carbon content, and the mesoporosity was tailored by the applied temperature. The supported $TiO_2$ nanocrystals prepared by pyrolysis at 300, 350, and $400^{\circ}C$ for 3 h on a stainless steel mesh were actual supported carbon doped $TiO_2$ nanocrystals. Thus, $PAN/DMF/TiCl_4$ offers a facile, robust sol-gel related route for preparing supported carbon doped $TiO_2$ nanocomposites.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.497-504
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• 1993

The effect of DCCA (Drying Control Chemical Additives) on the drying of gel was investigated in order to determine an optimum drying condition of mullite precursor through sol-gel process. Aluminium sec-butoxide was synthesized from aluminium foil and then mullite powders were synthesized from Tetra-ethyl-ortho-silicate (TEOS) and the aluminium sec-butoxide. N, N-dimethyl formamide (DMF), Glycerol, 1, 4-Dioxane, and Oxalic acid were used as DCCA. Mullite powders that were calcined at 200, 900, 1100, and $1250^{\circ}C$ for 2hr were analysed by XRD, TG-DTA, FT-IR, and SEM in order to investigate structural change and characteristics of calcined powders. The results of this work showed that the drying time of gel was reduced to about half in the presence of 0.1mol DMF compared with the absence of DCCA and also calcined powders were obtained without remarkable structural change despite of the addition of DCCA.

• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.739-752
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• 2018

Purpose: The purpose of this study was to investigate the relationship between kiln processing parameters and NOx emissions that occur in the sintering and calcination steps of the cement manufacturing process and to derive the main factors responsible for producing emissions outside emission limit criteria, as determined by category models and classification rules, using data mining techniques. The results from this study are expected to be useful as guidelines for NOx emission control standards. Methods: Data were collected from Precalciner Kiln No.3 used in one of the domestic cement plants in Korea. Thirty-four independent variables affecting NOx generation and dependent variables that exceeded or were below the NOx emiision limit (>1 and <0, respectively) were examined during kiln processing. These data were used to construct a detection model of NOx emission, in which emissions exceeded or were below the set limits. The model was validated using SPSS MODELER 18.0, artificial neural network, decision treee (C5.0), and logistic regression analysis data mining techniques. Results: The decision tree (C5.0) algorithm best represented NOx emission behavior and was used to identify 10 processing variables that resulted in NOx emissions outside limit criteria. Conclusion: The results of this study indicate that the decision tree (C5.0) can be applied for real-time monitoring and management of NOx emissions during the cement firing process to satisfy NOx emission control standards and to provide for a more eco-friendly cement product.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.303-306
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• 2011

[ $V_2O_5$ ]doped Karrooite pigments were synthesized by the solid state method to get stabilized brown pigment in oxidation and reduction atmosphere. Optimum substitution condition and limited dopant with $V_2O_5$ for Karrooite pigment was investigated. With calcination at $1250^{\circ}C{\sim}1400^{\circ}C$, compositions were designed varying $V_2O_5$ molar ratio by increasing 0.02mole to the formula $Mg_1-xTi_2-xM_{2x}O_5$(x = 0.01~0.09 mole). Synthesized pigments were analyzed by XRD, Raman spectroscopy and UV-vis. When $V_2O_5$ was doped from 0.01 to 0.05 mole, single phase of Karrooite was observed at temperature $1300^{\circ}C$ and soaking time 4h by Raman spectroscopy. However, it was found that excess $VO_2$ peak appeared with 0.07 and 0.09 mole of $V_2O_5$ doped to $MgTi_2O_5$. This result indicated that the maximum limit of solid solution is 0.05 mole $V_2O_5$. Karrooite pigments were applied as a ceramic pigment to achieve brown colors in lime magnesia glaze and lime barium graze at both of oxidation and reduction atmosphere. CIE color coordinates are $L^*$ = 40.34, $a^*$ = 9.94, $b^*$ = 21.40 in lime magnesia glaze.