• Korean Journal of Materials Research
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• v.2 no.2
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• pp.126-132
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• 1992

Experiment has been performed to investigate the thermal and magnetic properties of Mn-ferrite by electrolysis. Using the 0.2%C mild steel as soluble anode and SUS 304 stainless steel as cathode, Mn-ferrite could be made from the sulfuric acid leaching of the wasted manganese dry cell and $MnSO_4$reagent by electrolysis. As the result of X-ray diffraction, thermal analysis and magnetic measurement, Mn-ferrite was the spinel type in $Mn_{x}Fe_{3-x}O_4$ (X=1), the weight loss rate of $Mn_{x}Fe_{3-x}O_4$ were linearly increased up to the $200^{\circ}C$. Ms, Mr and Hc values were decreased with increasing Mn content and heating temperature. When Mn-ferrite was formed by $MnCl_2$reagent electrolysis, Ms values were higher than those formed from the sulfuric acid leaching of the wasted manganese dry cell and $MnSO_4$reagent by electrolysis. In Mn-ferrite, which was formed from the sulfuric acid leaching of the wasted manganese dry cell by electrolysis, Ms and Mr values were higher, Hc values were lower than which was formed by $MnSO_4$ reagent electrolysis at $200^{\circ}C\;and\;300^{\circ}C, while the same values at $100^{\circ}C$. The shape of particles was spherical type, the sizes of them were about $0.1{\mu}m$ sub-micron in $MnSO_4$reagent electrolysis, $0.5{\mu}m$ in the sulfuric acid leaching of the wasted manganese dry cell by electrolysis.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.471-481
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• 2007

The Landslide in natural slope is occurred mostly by a heavy rain of the summer. This landslide is influenced in soil property of the surface than the rock mass. Soils in natural slope are created by weathering phenomena of the bedrock. These soils differed to the geological conditions such as sedimentary rock, metamorphic rock and volcanic rock. Therefore, estimation of landslide in natural slope is the most important analysis of the bedrock distributions and soil characteristics. This study analyzed the soil property to the natural slopes of Busan area where is distributed to volcanic rock, granite and sedimentary rock. Soil sample conducted various soil tests for estimate the soil physical property and soil engineering characteristics, and analysis of the correlation of geological conditions. In the experiment result, soils were mainly classified by a clayey sand. It is also established that $1.07{\sim}1.99kg/cm^3$ for wet density, $28.2{\sim}39.6^{\circ}$ for angle of shearing resistance, and $8.10{\times}10^{-5}{\sim}8.38{\times}10^{-2}cm/sec$ for coefficient of permeability. From the physical parameter, the soils are estimated to the permeable ground with good shear strength, and soil properties are showed a differential tendency for each geological condition.

• Korean Journal of Environmental Agriculture
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• v.24 no.3
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• pp.203-209
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• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.656-662
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• 2013

The iron oxide ($Fe_3O_4$) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1143-1148
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• 2002

Precipitated calcium carbonate is one of the most versatile mineral fillers and is consumed in an wide range of products including paper, paint, plastics, rubber, textiles, sealants, adhesives and printing ink and can be produced by several methods. Calcium carbonate has three isomorphism; vaterite, aragonite and calcite, with numerous variations of morphology in the natural mineral or organism. Formation process of vaterite in the reaction of system $Ca(OH)_2-CH_3OH-H_2O-CO_2$ were investigated by measuring the electrical conductivity, $Ca^{2+}$ ion concentration, pH in the slurries and by means of X-ray diffraction and electron microscopic observation. It was clearly established that the reaction temperature is important variable in the carbonation process; in general over 50${\circ}C$, the vaterite was precipitated with the calcite and aragonite. SEM and XRD observations revealed that the vaterite formation could be prepared the temperature range of 40 to 50${\circ}C$ and mean size of particles in this range is controlled from 0.5 to 0.8 ${\mu}m$.

• Membrane Journal
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• v.21 no.4
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• pp.360-366
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• 2011

The effect of cross-flow velocity and transmembrane pressure (TMP) on membrane fouling was observed from pilot-scale operation of thermophilic anaerobic membrane bioreactor (AnMBR) treating food waste leachate. It was found that fouling rate was reduced significantly as cross-flow velocity increased at constant TMP mode of operation while this effectiveness was more pronounced at lower TMP. Higher TMP resulted in less permeable fouling layer possibly due to compressibility of foulant material on membrane surface. Particle sizes of membrane concentrate ranged from 10 to $100{\mu}m$, implying that shear-induced diffusion enhance back transport of these particle sizes away from the membrane effectively. From the continuous operation of AnMBR, it was confirmed that shear rate played an important role in the reduction of membrane fouling. Membrane autopsy works at the end of operation of AnMBR showed clearly that both organic and inorganic fouling were significant on membrane surface. Surface shear by cross-flow velocity was expected to be less effective to remove irreversible fouling which can be mainly caused by the adsorption of organic colloidal materials into membrane pores.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.367-373
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• 2015

In this study, fundamental properties of cement were reviewed to apply high fineness cement at low temperature environment. The classified high fineness cement has large proportion of particles below $10{\mu}m$ which affects early hydration: an overall reaction of cement hydration faster. As a result of using high fineness cement, setting time of concrete was reduced and compressive strength was higher than OPC at all ages. Especially, compressive strength was more than double its value compared with OPC after three days curing in low temperature. Faster reaction and higher heat of hydration was verified by calorimetry early and maximum heat of hydration was analyzed by adiabatic temperature raising test. The analysis of this study confirmed that high fineness cement can be suitable to be used in low temperature environment.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.234-239
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• 1999

A Abstract Yttria-stabilized zirconia(YSZ) thin films were synthesized by plasma enhanced chemical vapor deposition process. $Zr[TMHD]_4$ $Y[TMHD]_3$ precursors and oxygen were used with the deposition temperature of $425^{\circ}C$ and rf power ranging 0-100 watt. Effects of the deposition parameters were studied by X-ray diffraction and thickness anal­ysis. YSZ thin films have cubic crystal structure with (200) orientation. From the results of EDX analysis, the converte ed content of TEX>$Y_2O_3$ was determined to be 0-36%, and the film thickness was increased with bubbling temperature which is considered to be due to increasing TEX>$Y_2O_3$ flux. The depth profiles of Zr, Y and 0 appeared relatively $\infty$nstant through film thickness. Columnar grains of $1000~2000\AA$ grew vertical to the substrate surface for the case of Ar carri­er gas. In case of He carrier gas, the grain size was observed to be about $1000~2000\AA$. X-ray diffraction data showed the increase of lattice constant with TEX>$Y_2O_3$ content. It was that the presence of the cracks formed during film deposition, partially released the stress generated by the increase of lattice constant.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.727-740
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• 2018

The media in the undersaturated zone is defined as the uppermost layer of the water table at which the groundwater is unsaturated or saturated discontinuously. The properties of the unsaturated zone can affect the reduction of contaminants that flow from the lower part of soil to the water table. In recent, there have been problems in evaluating groundwater contaminations vulnerability because weighted value for permeability is given, regardless of anisotropy and heterogeneity in the unsaturated media. Geological media have various ranges of permeability. When applying the weighted value, representative of permeability for grain sizes standardized, to construction of contamination vulnerability, it will produce more exaggerated result than the case that considers unsaturated geological properties. In this study, we performed laboratory column tests considering two sets of the unsaturated layers in order to investigate the permeability in anisotropic unsaturated zone with anisotropy. On the basis of the tests, average permeability coefficients were calculated considering the properties of unsaturated media obtained from drill cores in the field. The final contamination vulnerability map constructed shows that the contamination vulnerability map applying the properties of geological media of the unsaturated zone coincides much better with the results measured in the field, compared to the case of contamination vulnerability considering the weighted value in the unsaturated zone.