• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.21-26
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• 2014

Red clay has been used for making rakuyaki for the past 400 years. Because the resources for red clay in Japan are being depleted, many potters in Japan began to develop new materials which can replace red clay. In this study, It is analyzed that the chemical and physical properties of red clay from Shigaraki (Shiga, Japan), and developed a novel engobe which can be used for making Rakuyaki instead of Shigaraki red clay. Results from Raman spectroscopic examination showed that ferric oxide content in Shigaraki red clay is 9.4 % (Goethite 5 %, Wustite 4.4 %), and that the mechanism of red color development by the firing at $900^{\circ}C$ for 10 min is the chemical transformation of Goethite into Hematite, and the subsequent formation of solid solution with Alumina and Silica. To make similar ferric oxide content to that of Shigaraki red clay, we added 5 g of Goethite and 9 g of Wustite to 100 g of White kaolin from Hadong area (Gyeongsangnam-do, Korea). The $L^*a^*b^*$ color scale of the mixture was 56.83, 27.22, and 23.28, respectively, and stable red color was successfully developed under the same firing condition used for Shigaraki red clay.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.23-31
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• 2005

This study was performed to investigate the effect of humic acid on the adsorption of arsenic onto hematite and its binding mechanism through the chemical speciation modeling in the binary system and the adsorption modeling in the ternary system. The complexation modeling of arsenic and humic acid was suitable for the binding model with the basis of the electrostatic repulsion and the effect of bridging metal. In comparison with the experimental adsorption data in the ternary system, the competitive adsorption model from the binary intrinsic equilibrium constants was consistent with the amount of arsenic adsorption. However, the additive rule showed the deviation of model in the opposite way of cationic heavy metals, because the reduced organic complexation of arsenic and the enhanced oxyanionic competition diminished the adsorption of arsenic. In terms of the reaction mechanism, the organic complex of arsenic, neutral As(III) and oxyanionic As(V) species were transported and adsorbed competitively to the hematite surface forming the inner-sphere complex in the presence of humic acid.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.837-843
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• 2010

This research investigated classification of clay activity degree by different clay mineral components. Based on compositions of different clay and oxide minerals within 390 soil series in Korea, 7 soils were selected to analyze for CEC and specific surface area of clay minerals. As a result, soils were mainly composed with Chlorite originated from sandstone, Smectite originated from Andesite porphyry and combination of Allophane and Ferrihydrite originated from volcanic ash, if the ratio of CEC value to clay content (degree of clay activity) was greater than 0.7. If the degree of clay activity was ranged between 0.3 and 0.7, soils were composed mainly with Kaolin originated from anorthite. Soils with this ratio also was composted with combinations of Kaolin, Illite and Vermiculite originated with river deposits. When the degree of the activity was less than 0.3, soils were commonly red-yellowish color and composed with two different minerals. One type of composition was Kaolin originated from granite and granite gneiss and the soils contained Geothite and Hematite. The other type was composited mainly with Illite and Vermiculite minerals originated from granite. These soils contained Gibbsite, Geothite and Hematite. The degree of clay activity was highly related with CEC and specific surface area. The greater degree of the activity displayed greater values of clay CEC and specific surface area. It is not easy to measure actual quantity and compositions of clay minerals, while the degree of clay activity can be measured from routine soil analyses. As a conclusion, the degree of clay activity may be not just a simple but also powerful tool to estimate physical-chemical properties of soils and to evaluate the soil classification in Korean soils.

• Proceedings of the Petrological Society of Korea Conference
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• 1999.06a
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• pp.107-111
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• 1999

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.14-21
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• 2016

This study evaluated the applicability of stabilization of arsenic (As)-contaminated soil with iron (Fe) oxides at the former Janghang smelter site. Three Fe oxides (magnetite, goethite, and hematite) were tested as stabilizing agents to one soil sample collected from the study site. Amendment of 5% of magnetite, goethite, or hematite for one week showed the 64, 58, and 36% of reduction of the SBRC (Solubility/Bioavailability Research Consortium)-extractable (bioaccessible) As, respectively. Duration of stabilization more than one week did not show an additional reduction in SBRC-extractable As. Amendment of 5% of magnetite, which showed the highest As stabilization efficiency, was applied to 24 soil samples collected from the same site for one week, and 72% of reduction in the bioaccessible As was observed. The potential carcinogenic human health risk at the study site caused by As was $1.7{\times}10^{-5}$, which could be reduced to $8.1{\times}10^{-6}$ by the amendment of 5% magnetite for one week.

• Economic and Environmental Geology
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• v.31 no.4
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• pp.325-338
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• 1998

105 oriented samples (19 matrix samples, 86 cobble samples) were collected from the Silla Coglomerate Formation in Jinju and Goryeong areas to clarify the regional remagnetization of Cretaceous Kyongsang supergroup. Both the alternating field and thermal demagnetizations were conducted for the collected samples. The characteristic remanent magnetizations of these samples divided into three types in the Silla Conglomerate Formation: The ingredient magnetic minerals are magnetite, hematite, or both magnetite and hematite in a specimen. The characteristic remanent directions of cobble samples did not clustered to any direction. And the characteristic remanent directions of interbedded sandstones in the Silla Conglomerate Formation is $D/I=20.6^{\circ}/54.5^{\circ}$ (${\alpha}_{95}=11.1^{\circ}$, k=48.8) after tilting correction, agree with previous paleomagnetic studies on the Hayang group. These results implied that conglomerate test was passed indicating no regional remagnetization in the studied area after deposition of the Silla Conglomerate Formation.

• The Korea Journal of Herbology
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• v.20 no.2
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• pp.17-26
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• 2005

Objectives : The study has been undertaken to scrutinize the results of Halloysitum Rubrum before and after physical and chemical manipulation. Methods : I used X-rays diffracted analysis system(Phillips X'Pert - MPD System) on condition of 40Kv, Anode of Cu Ka to grasp the compositions of crude Halloysitum Rubrums which have been from here and there after pulverization them below 200 mesh. X-rays fluorescence analysis system have been used to check the chief elements content of the ore on condition of 40Kv, 95mA. ICP-MS analysis system(Perkin Elmer, Elan 6100)have been used after a micro-elements and a heavy metals take advantage of mixed acid were dissolved completely. Results : The compositions of the ore Halloysitum Rubrum are composed of large amount of Halloysite and Kaolinite, and small amount of Hematite, Alum, quartzite. The chief elements content of the ore Halloysitum Rubrum are composed of Al and Si. A heavy metals in Halloysitum Rubrum are As, Cd, Cr, Cu, Pb, Zn, etc. As and Zn's amounts was lessen after physical and chemical manipulation Halloysitum Rubrum are decreased at $400^{\circ}C\;and\;450-500^{\circ}C$ each by heat analysis system. Conclusion : Results of this study show that Halloysitum Rubrum can be used in a diverse ways to treat many kinds of disease.

• Resources Recycling
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• v.7 no.2
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• pp.23-30
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• 1998

Aiming to rccycle the valuable mrnpunenl such as iron oxiiles and carbon from blast turnace sludge, [he physlco-chemical property and classification charactei~stics by hydrocyclone wcie invcstigxted. Carbon in sludge wils analysed to bo cxated mostly in coarse particles of sludge as a form of graphite whereas zinc lnortly in fine particles as zinc sulfides. On thc contrxy, iron oxides wne proved to be in the form of hematite, magnetile without any segregations according to particlc sizes of sludge. From the results of classiIication test using hydmcyclane of 75 mm dm, the recovcry and dczincificatian rate of low zinc sludge wcrc in the range of 67.9-73.6%, and 72.7-86 8%, respectively.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1119-1123
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• 2002

Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.3
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• pp.281-287
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• 2012

The internal oxide scale of twelve superheater and reheater tubes were tested which were serviced for 30,000~120,000 hours in thermal power plants. The oxide scale was formed in three layers. The Cr-rich area was observed beneath the original metal surface. The hematite ($Fe_2O_3$) phase was formed on the outer surface. The intermediate layer was magnetite ($Fe_3O_4$). The thickness of Cr-rich layer was about half of the total scale. All layers grew during the operation hour of the plant. The thickness of thickest scale was 0.2mm in superheater tubes. This can increase the tube metal temperature about $7^{\circ}C$ more than initial state. $7^{\circ}C$ tube metal temperature can reduce tube life about 30%, but the boiler tube's design margin is big enough therefore it has been analyzed that it would not effect on the life span.