• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.21-28
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• 1985

The properties of magnetic recording materials largely depend on their shape magnetic anisotropy. The control of their shape and size distribution is very important for improving magnetic properties. The silica-coated goethite$(SiO_2$/$\alpha$-FeOOH=1.5wt%) having acicular shape was prepared. The sillica-coated goethite was heat-treated at 40$0^{\circ}C$~1,00$0^{\circ}C$ 1hr and then reduced at 50$0^{\circ}C$ 2hr. When the silica-coated goethite was heat-treated at 80$0^{\circ}C$ its acicular shape was maintained and its magnetic properties were improved(Hc: 1,325 Oe $\sigma$m:138.8 emu/g, Rs:0.56) However the acicular shape of the paricles was broken for non-coated hematite obtained by dehydration at 80$0^{\circ}C$ They were sintered and showed poor magnetic properties.

• Journal of the Mineralogical Society of Korea
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• v.12 no.1
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• pp.32-42
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• 1999

Microbial mats, the yellow and reddish brown deposits formed from the mine drainage, occur on the bottom of drain and mine tailing pond of the Ilkwang mine in Pusan, Korea. The constituents of microbial mats and their biomineralization were studied by using XRD, IR, and SEM-EDX. The upper part of the microbial mat is yellow-colored and composed of tube-shaped and small spheroid bacterial materials, which are mainly made up of amorphous and poor-crystalline iron-oxide minerals. The shape and composition of bacterial materials suggest that they are probably belong to iron-oxide mineral aggregates. The iron-oxide minerals of the yellow microbial mats are mainly goethite, but those of the reddish brown microbial mats contain abundant hematite along with goethite. This implies that with the evolution of biomats, goethite may be transformed to hematite.

• Journal of Magnetics
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• v.6 no.1
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• pp.5-8
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• 2001

Cheju island is composed of volcanic tuff. The soil in Cheju island has principally sprung from basalt and partially made up of trachyte, and andesite. Also ancient relics, plain coarse pottery kilns and pantiles kilns are homogeneously distributed all over the Cheju island. In this study samples of plain coarse pottery and pantiles from five regions of Cheju island have been examined through X-ray fluorescence spectrometer and Mossbauer spectroscopy. It is thought that these samples be partially formed from neutral volcanic rock like trachyte and the valence state of iron is almost $Fe^{3+}$. Also the magnetic hyperfine field of goethite contained in these samples is less than synthetic goethite. This result shows the degradation of magnetic order caused by the partial substitution of diamagnetic positive ion $Fe^{3+}$ by $Al^{3+}$ in the goethite lattice.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.453-457
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• 1998

The sorption of UO$_2$$^{2+}$showed ionic strength independece for goethite and dependence for kaolinite. In the presence of carbonate, the sorption decreased in the weakly alkaline pH range becase of the formation of aqueous U(VI)-carbonate complexes. The sorption of UO$_2$$^{2+}$onto goethite and kaolinite under various experimental conditions was successfully interpreted using a surface complexation modeling, named triple layer model (TLM). The best fit to the experimental data was obtained by the FITEQL program, and then evaluated with available spectroscopic data. The results showed the versatility of surface complexation modeling over empirical one to predict UO$_2$$^{2+}$ sorption behavior.avior.

• Journal of the Mineralogical Society of Korea
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• v.2 no.1
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• pp.11-17
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• 1989

The kaolin deposits in Hadong-Sancheong area, have been formed by supergene weathering of anorthositic rocks including anorthosite, leucogabbro, and gabbro. Kaolin consists chiefly of halloysite(10$\AA$) and kaolinite with other minerals such as illite, vermiculite, plagioclase, hornblende, quartz amorphous materials(allophane and siica), goethite, and hematite. Goethite and hematite are the major coloring agents of the reddish brown and other colored kaolins. Other common accessory minerals are magnetite, ilmentite, anatase, gibbsite, I/S, C/V, chlorite, lithiophorite, and birnessite. Paragonite, dravite, laumontite, clinozoisite, muscovite, scolecite, stellerite are locally found. Al substitution of Fe in goethite and hematite decreases from the surface zone toward the deeper zone. The kaolin deposits show three horizontal zoning; the upper reddish brown, middle pink, and lower white zones. All the zones are characterized by somewhat different mineralogy. The factors for the formation of kaolin deposits in Hadong-Sancheong area are 1) the presence of anorthositic rocks, 2) the low flat or gentle topography, 3) the favorable climate, and 4) the long-continued preservation of kaolins with-out erosion.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.413-420
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• 2000

Cheju Island has nature of typical trass through volcanic activities in many times. The soil in Cheju Island has principally sprung from basalt and partially made up of trachyte, trachyte's nature and site. Also ancient relics, plain coarse pottery's kilns and pantiles kilns are homogeneously distributed all over the Cheju Island. In this study, as a result of X-ray fluorescence spectrometer and Mossbauer spectroscopy of a sample are from plain coarse pottery and pantiles in 5 regions of Cheju Island. It is thought that these samples are partially formed from neutral volcanic rock like trachyte and Atomicity state of iron is almost Fe$\^$3+/. Also the magnetic hyperfine field length of goethite, contained these samples is less than synthetic goethite magnetic hyperfine field length and this result shows that disintegration of inner magnetic order, created by partial substitution of diamagnetic positive ion containing Fe$\^$3+/ and Al$\^$3+/ in goethite lattice.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.353-357
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• 2004

The influences of the ozone oxidation, reaction temperature and NaOH equivalent ratio on the iron oxide formation were studied with fixed ferrous sulfate concentration(0.5M $FeSO_4$ㆍ$7H_2$O). Geothite($\alpha$-FeOOH) and/or Magnetite ($Fe_3$$O_4$) were synthesized depending on the reaction conditions. The characteristics of the synthesized powders were evaluated by XRD, SEM and quantitative phase analysis. The synthetic conditions to get Goethite were quite different from the results of Kiyama's and the Goethite was conveniently synthesized at low temperature and at low NaOH equivalent ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.107-111
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• 2006

The samples collected from two reactors are analyzed by X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy in this study. It is concluded that the iron oxide crystal attached on anthracite media which possesses catalytic ability is identified to be Ferrihydrite, regardless of the value of pH from the analysis of the iron oxide. Iron oxide in Batch reactor is identified to be Microcrystalline goethite.

• Cement Symposium
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• no.22
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• pp.47-53
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• 1994

• Resources Recycling
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• v.13 no.6
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• pp.9-15
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• 2004

The optimum conditions were studied for the preparation of transparent iron oxide with the air oxidation of FeOOH. The FeOOH obtained by mixing NaOH and FeSO$_4$ solution in various conditions such as R(=2NaOH/FeSO$_4$), FeSO$_4$ concentration. reaction temperature and air flow rate. When the FeSO$_4$ increased gradually, the concentration of iron ion in the solution became high. So, particle size increased precipitating Fe$_3O_4$. Goethite dehydrate at about 200$^{\circ}C$ and ended the reaction at about 320$^{\circ}C$ forming hematite. The lower the reaction temperature was, the shorter the particle length of goethite and particle size decreased. When the flow rate of air as an oxidant increased, the amount of dissolved oxygen in the solution increased, which made oxidation rate increased. And then particle size of goethite decreased.