• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.281-282
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• 2008

고압절연용 에폭시-나노콤포지트의 전기적, 기계적, 열적특성이 동반적 물성의 상승을 가져오기 때문에 활발한 연구가 진행 중에 있다. 에폭시 메트릭스 내에서 유기화된 층상구조를 갖는 나노입자의 분산정도에 따라 여러 가지 물성에 영향을 나타내고 있다. Centrifugal 분산기법으로 나노콤포지트제조시 에폭시분자의 층간내로 충분한 삽입으로 박리가 발생하였다. 전기적 특성로서 기본적 구조적 특성인 X-RD특성과 TEM의 관찰로 분산을 확인할 수있었고, DSC의 측정으로 가교도를 알 수 있는 Tg값이 원형수지에 비하여 $11^{\circ}C$향상된 여러종류의 나노콤포지트를 개발하였다. 유전특성 및 절연파괴 특성으로도 원형수지에 비하여 나노콤포지트의 향상된 특성을 얻을 수 있었다.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.48-53
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• 2007

Pulverization characteristics of H-kenyaite in vibration mill and exfoliation property in epoxy of pulverized H-kenyaite was investigated by using XRD, SEM, TEM. and particle size analyzer. Pulverization was conducted for 0.5~5 h. The particle morphology of sample pulverized for 1 h preserved plate-shape. However, this plate-shape disappeared in the sample pulverized for 3 h. The XRD pattern of sample pulverized for 1 h showed the characteristic peak of H-kenyaite. However, the peak disappeared in samples pulverized above 3 h, indicating severe destruction of H-kenyaite structure. TEM analysis for the kenyaite/epoxy nanocomposites exhibited only gallery expansion of 3~5 nm in non-pulverized sample, but dramatical large expansion of 5~10 nm in the samples pulverized during 1 h. This results confirm that the pulverization of wide plates composed of H-kenyaite particle have largely affect on the formation of an exfoliated kenyaite-polymer nanocomposite.

• Journal of Adhesion and Interface
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• v.5 no.1
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• pp.29-35
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• 2004

We have prepared polyster/nanQhybridized polyimide films in the range of 1~9 wt% of organophilic synthetic layered silicate (STN). Firstly, poly(amic acid)/STN nanocomposite solutions were prepared via solution blending method in DMAc or THF/MeOH solution, and then cast on the polyester film followed by imidization reaction, thermal and chemical method repestively. XRD and TEM experiment showed that the STN was fully exfoliated through the polyimide matrix. Surface morphologies of nanohybridized polyimide films were characterized by AFM and thermal, mechanical properties were also confirmed by TGA, DMA and UTM each. And also, the water vapor permeabilities highly depended on the content of STN. The sample from chemical imidization route and THF/MeOH solvent system showed better water vapor barrier properties than thermal one and DMAc system.

• Elastomers and Composites
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• v.44 no.4
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• pp.455-465
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• 2009

In this study, Organo-montmorillonite(MMT) was synthesized by intercalation of various amine(Octylamine, Dodecylamine, Dimethyldodecylamine, Octadecylamine) compounds into layered silicate. Natural Rubber(NR)/MMT nanocomposites were prepared by reinforcement of Organo-MMT. X-ray diffraction(XRD) and Scanning electron microscope(SEM) were employed to characterize the layer distance of Organo-MMT and the morphology of the NR/MMT nanocomposites. The structures of the synthesized Organo-MMTs were analyzed by the measurement of FT-IR. Cure characteristics, surface free energy and mechanical properties such as tensile strength, modulus and hardness of NR/MMT nanocomposites were carefully studied by contact angle meter, ODR, UTM, and hardness tester. FT-IR analysis showed a insertion of the alkyl and amine chains into the interlayers of the MMT. It was shown that the cure time of the organo-MMT was more decreased than that of $Na^+$-MMT. Surface free energy and tensile strength of the NR/DDA-MMT nanocomposite were the highest. NR/ODA-MMT nanocomposite was the highest in hardness.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.302-307
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• 2007

In this paper, a flap valve micropump with an ionic polymer-metal composite (IPMC) actuator was designed, fabricated, and experimentally characterized. A multilayered IPMC based on Nafion/layered silicate and Nafion/silica nanocomposites was fabricated for the actuation section of the micropump. The IPMC diaphragm, a key element of the mircopump, was designed so that the IPMC actuator was supported by a flexible polydimethylsiloxane (PDMS) structure at its perimeter. This design feature enabled a significantly high displacement of the IPMC diaphragm. The overall size of the micropump is $20{\times}20{\times}5$ ${mm}^3$. Water flow rates of up to 760 ${\mu}l$/min and a maximum backpressure of 1.5 kPa were recorded. A significant advantage of the proposed micropump is its low driven voltage from only 1-3 V. In addition, a simple and effective design, and an ease of manufacturing are other advantages of the present micropump.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.177-182
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• 2006

In this work, we have prepared organophilic MMT having thermal stability by ion exchange reaction of various aromatic ammonium salts with MMT containing sodium ion. The organic modifiers having alkyl side chains and amine functional group were successfully synthesized by effectively introducing the surfaces of MMT via ion exchange reaction to form organophilic MMTs with a view to improve the reactivity and thermal stability. The WAXD patterns of organophilic MMT showed the more increased gallery spacing by $3.3{\AA}$ than that of the pristine MMT and also the onset of initial decomposition of organophilic MMT was $275^{\circ}C$ as determined by a thermogravimetric analysis. The polyimide (PI) nanocomposite films based on poly(amic acid) and organophilic MMT were prepared by a solution blending followed by cyclodehydration reaction. We have investigated the dispersity of organophilic MMTs in PI matrix by using WAXD and the effect of the organophilic MMT content on the mechanical properties of PI nanocomposite films was studied.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.173-183
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• 2012

The nature of surface deformation of Tono granite was investigated using a confocal laser scanning microscope (CLSM) under water-saturated stress relaxation conditions. A new apparatus was developed for this experiment, enabling continuous measurements of stress-strain and simultaneous observations of surface deformation by CLSM. The amounts of grain contact deformation and intra-granular surface deformation were calculated using a finite element method. The results reveal that intense grain contact deformation and intra-granular surface deformation occurred during the period of stress relaxation, and that the intensity of this deformation increased with increasing applied stress. Finite element method (FEM) results show that the strain of grain boundary was greater than strain of inter-granular surface. Contour maps of these local strains were compiled for individual grains and their boundaries, revealing intense deformation at the boundaries between biotite and quartz under compressional stress. This result was a consequence of the mechano-chemical effect of biotite and quartz minerals. Biotite in granite has a layered structure of iron-magnesium-aluminum silicate sheets that are weakly bonded together by layers of potassium ions. In contrast, quartz occurs as stable spherical grains.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.491-508
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• 2002

While about 80% of Jeju soils are classified as Andisols, the soils derived from volcanic ash in Dangsanbong are not Andisols. There is a significant difference of precipitation in localities of Jeju island. The study area is characterized by the lowest amount of annual rainfall in Jeju Island, and by the layered silicates as dominant solid phase in clay fraction. The purpose of this study was to characterize the mineralogy of the non-Andie soils in detail, especially hydroxy-interlayered silicates. Two major soil horizons are recognized in the soil profile developed in the Dangsanbong area, which can be designated as A and C. The soil pH($H_{2}0$), ranges from 6.6 to 7.3 increasing with depth, is higher than that of typical Andisols(pH<6.0). While the pH(NaF), ranges from 9.49 to 9.81, indicates that significant amount of amorphous phases might be present as exchanging complexes. It is estimated to about 1.542.88 wt% by using chemical selective dissolution. The organic content of surface horizon is about 2 wt%. This soil are composed of quartz, feldspar and olivine as major constituents with minor of silicate clays. Quartz is frequently observed in A and distinctly decreases in its amount with depth, while olivine is dominant phase in C and rarely observed in A. In the <0.2$\mu\textrm{m}$ size fraction, smectite and kaolinite/smectite interstratification are dominant with minor of illite. The amounts of smectite decrease with depth, while the amounts of kaolinite/smecite interstratification increase with depth, which indicates the trend of mineral transformation with increasing the degree of weathering. The proportion of kaolinite in kaolinite/smectite interstratification is about 85%, and is not changed significantly through the profile. In the 2-0.2$\mu\textrm{m}$size fraction, vermiculite, smectite, illite and kaolinite are major components with minor of chlorite. Most of chlorite are interstratified with smectite. Chlorite which is not interstratified with smectite occurs only in surface horizon. The proportion of the chlorite in the chlorite/smectite interstratification is 59-70(%) and increases with depth. Hydroxy-interlayered vermiculite(HIV) with hydroxy-Fe/AI in their interlayers occurs in both A and C horizon. The amounts of hydroxy-Fe/AI decrease with depth. Hydroxy-interlayered smectite(HIS) of which interlayers might be composed of hydroxy-Mg/Al occurs only in C horizon. As the results of mineralogical investigation for the soil profile in the study area, clay minerals might be changed and evolved through the following weathering sequences: 1) Smectite Kaolinite, HIS, Vermiculite, 2) Vermiculite HIV Chlorite.