• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.21-25
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• 1985

For studying the influence of addition of Polyvinyl alcohol (PVA)-montmorillonite complex on the hydration of Portland cement the PVA-montmorillonite derivatives were prepared in advance an characterized system-of Portland cement the PVA-montmorillonite derivatives were prepared in advance and characterized systema-tically. PVA with the polymerizationdegree ranging from 500 to 2000 have been intercalated into the lamellar structure of hydrated montmorillonites which were fractionated under 2㎛ by Stock's rule. In all cases the constant basal spacing of ∼20Å was determined whatever the molecular weight of PVA used. And the carbon chain orientation of PVA in the interfoliar space has been deduced to be parallel with bilayer structure.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.960-962
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• 1999

Organically modifidied montmorillonites were synthesized from sodium montmorillonite and alkylammonium halids (stearyltrimethyl bromide and cetyltrimethyl bromide) by solid-solid reaction. The structure of the products by solid-solid reactions was similar to that observed in a conventional solution method.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.79-85
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• 2006

Olefinic compatibilized blend(R-PP/R-PE)/layered silicate composites have been prepared by melt intercalation technique directed from $Na^{+}$ montmorillonite(MMT) or organophilic montmorillonites while using magnesium hydroxide as flame retardant. Morphology and flammability properties were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), thermogravimetry analysis(TGA), limiting oxygen index(LOI), UL94 test. It is found that the compatibilized blend/layered silicate(Cloisite 20A) nanocomposites have a mixed immiscible-intercalated structure and there is better intercalation when a compatibilizer is combined with the polymer and layered silicate to be melt blended. A very large increase in the LOI value was observed with hybrid filler addition and further enhancement in thermal stability and compatibility of blend was obtained for the compatibilized blend containing small amount of layered silicate.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.63-65
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• 2008

The increased interest in reducing the environmental effects caused by releasing organic compounds and aqueous waste has motivated the development of polymeric materials in supercritical fluids. Recently, supercritical fluids have been used in material synthesis and processing because of their special properties, such as high diffusivity, low viscosity, and low surface tension. Supercritical carbon dioxide is the most attractive because it is non-toxic, non-flammable, and has moderate critical temperature and critical pressure values. Supercritical carbon dioxide can also swell most polymers. In this study, we prepared polymer/clay nanocomposites using supercritical fluids. Cloisites 10A, 15A, 25A, and 30B used in this study are montmorillonites modified with a quaternary ammonium salt. The nanocomposites of polymer/clay were characterized by X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

• Bulletin of the Korean Chemical Society
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• v.22 no.7
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• pp.678-684
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• 2001

Porous silica-pillared montmorillonites were prepared by simultaneous intercalation of dodecylamine-TEOS [tetraethylorthosilicate, Si(OC2H5)4] into the H-montmorillonite and intragallery amine-catalyzed hydrolysis of TEOS. Mixtures of the H-montmorillonite, dodecylamine and TEOS at molar ratios of 1 : 2 : 15-30 and 1 : 2-6 : 20 resulted to swollen and viscous gel once at room temperature, allowing intercalation compounds which dodecylamine and TEOS were simultaneously intercalated into interlayer of H-montmorillonite. The hydrolysis of the gallery TEOS was conducted in water solution for 40 min at room temperature, affording siloxane-pillared H-montmorillonite. Calcination of samples at 500 $^{\circ}C$ in air resulted in silica-pillared montmorillonite with large specific surface areas between 403 and 577 m2 /g, depending on the reaction stoichiometry. The reaction at H-montmorillonite : dodecylamine : TEOS reaction stoichiometries of 1 : 2 : 15 and 1 : 4 : 20 resulted in high specific surface areas and mesopores with a narrow pore size distribution. Result indicates that the intragallery-amine catalyze the hydrolysis of gallery-TEOS and simultaneously have a role of gallery-templated micellar assemblies.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.1-8
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• 1995

The smectite-rich clays were found locally in Paleozoic calcareous sedimentary rocks in the Samcheok area. Their occurrences were investigated in detail, and the physico-chemical properties of the clays were also determined by X-ray diffraction, chemical analysis, thermal analysis and cation exchanging experiment. The smectite clays occur as the fissure filling dyke developed in calcareous sedimentary rock and as alteration products of intrusive rhyolite. Most of clays occur at the contact between the sedimentary rock and the rhyolite, and the alteration zone was observed only in rhyolite body close to the contact. Judging from their occurrences, it is believed that the smectite-rich clays in this area were formed by the hydrothemal alteration. The smectite clays from the area are mainly composed of Ca-montmorillonite, and associated with small quantities of quartz, opal-CT and feldspar. The montmorillonites from this area are lower in Fe content, and higher in exchangeable Ca ion, compared to those of bentonite from the Yangnam-Yeongil area.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.307-315
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• 1999

Four organic polymers were mixed with mothmorillonite. Two cationic polymers a hi로 molecular weight polyacrylamide (494C) and a low molecular weight polymer (587C).Two anionic polymers include a high molecular weight polymer (aerotil). Each clay supension series were allowed to stand for 24 hours and were centrifuged, and the clay plugs were washed and dried. The dried samples investigated by XRD, IR and CEC measurement. The suspended clay containing anionic polymers was not flocculated at any concentratuons of polymer. But the suspendions containing two cationic polymers were rapidly flocculated at almost all concentrations. the d(001) spacings of Na-montmorillonite after being with cationic polymer 587C show about 15$\AA$ suggesting the polymers may have entered the interlayer spaces. The polymer 494C-treated sample produced double peaks of about 12 and 15$\AA$ in XRD. It indicates that the high molecular weight polymer. And cationic polymer 494C may be adsorbed mainy on the outside surface of clay, and some polymers may peretrate into olny interlayers in the margin of montmorillonite particles because of its high molecular weught. CEC of polumer 587-treated sample was reduecd mmarkedly suggesting polymer blocks CEC sites. The d(001) spacings of Ca-montmorillonite after being treated with cationic polymers show about 15$\AA$ suggesting that the interlayer spaces have not been expanded. In the experiment using a dilute Ca-bearing solution, the suspended caly containinf anionic polymers was flocculated. The results indicate that the flocculation behavior of montmorillonite-polymer supension depends on not only polymer properties such as concentration, electric charge and molecular weight but also compositions of solvent.

• Geotechnical Engineering
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• v.14 no.6
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• pp.73-80
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• 1998

In order to identify clay minerals in the soft ground, which has been deposited along the coastline of the Korean peninsula, 14 samples have been taken at different locations and then X-ray diffraction analysis is carried out for them. It is known from the analysis that the various kinds of clay minerals mixed with different portions exist in the soft ground, but halloysite is not traced in any samples. It is featured regionally that kaolinite and illite are found in the western coast and the southern coast. Montmorillonites exists only in the western coast. This feature of regional occurrences can be explained with the help of geology of the region. Activities determined from physical properties of the soils do not coincide with those of clay minerals identified from X-ray diffraction analysis.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1405-1407
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• 2001

It was studied to prepare high temperature heating elements using molybdenum disilicide($MoSi_2$). Molybdenum disilicide is widely used as material for manufacturing high temperature heating elements. $MoSi_2$ heating elements could be used at 1700-1900$^{\circ}C$. However, it is relatively expensive, and its demand depends on import. $MoSi_2$ powders was mixed with 4-5wt% of montmorillonites type bentonite as plasticizer and a small amount of $Si_3N_4$, $ThO_2$, and B as additives to prepare specimen of heating elements. Then, it was extruded, dried, sintered and machined followed by heating test. Effects of sintering conditions and amount of additives were investigated, It was sintered effectively at 1,350$^{\circ}C$ for five hours. Electrical resistivity was decreased with increasing of sintering temperature and time, and related with apparent density of the specimens. It was linealy decreased with increasing of sintered density. The heating elements thus prepared was stable at 1700$^{\circ}C$ and the physical properties such as specific electrical resistivity, hardness, apparent density, thermal expansion coefficient, and bending strength were almost identical with those of commercial heating elements.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.175-184
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• 1988

Ten under 2 micron size fractions of the montmorillonite from Yongdongri area, Gyeongsangbug-Do were studied using X-ray powder diffraction, cation exchange measurement, differential thermal analysis, thermogravimetric analysis, differential thermal scanning calorimetry and chemical analysis. Montmorillonites occurring at same deposit show limited variation in chemical composition whereas in thermal properties they do not. Their dehydroxylation endothermic peaks are "abnormal" type with a small range of variation of peak temperature reflecting tetrahedral substitution of Al for Si. Data from DSC show that divalent-cation saturated montmorillonite has relatively a higher endothermic heat capacity than monovalent-cation saturated montmorillonite, indicating that cations with higher electronegativity hold more water molecules.