• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.122-130
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• 2005

Layered silicate was synthesized at hydrothermal condition from silica adding to various materials. Nano-clay was synthesized by intercaltion of various amine compounds into synthetic layered silicate. The products were analysed by XRD, SEM, and FT-IR in order to examine the condition of synthesis and intercalation. From the results, it was confirmed that kaolinite was synthesized from precipitated silica and gibbsite at $220^{\circ}C$ during 10 days, and hetorite was synthesized from silica sol at $100^{\circ}C$ during 48 h. Na-Magadiite was synthesized from silica gel at $150^{\circ}C$ during 72 h, and Na-kenyaite was synthesized from silica gel at $160^{\circ}C$ during 84 h. Nano-clay was prepared using synthetic layered silicate intercalated with various amine compounds. Kenyaite was easily intercalated by various organic compounds, and has the highest basal-spacing value among other layered silicates. Basal-spacing was changed according to the length of alkyl chain of amine comopounds. Polymer can be easily intercalated by dispersion with large space of interlayer. Finally, epoxy/nano-clay nanocomposite can be easily prepared.

• Korean Journal of Metals and Materials
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• v.47 no.8
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• pp.516-521
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• 2009

In this study we report a rapid synthesis of nanoporous organo-functional silica (OFS) with unimodal and bimodal pore structures encompassing pores ranging from meso-to macroscale. The problems of tediousness and high production cost in the conventional syntheses are overcome by co-condensation of an inexpensive inorganic precursor, sodium silicate with an organosilane containing trimethyl groups. The insitu covalent anchoring of the non-polar trimethyl groups to the inner pore walls prohibits irreversible shrinkage of the wet-gel during microwave drying at ambient pressure and thus larger size pores (from ca. 20 to ca. 100 nm) can be retained in the dried silica. The drying process of the silylated wet-gels at an ambient pressure can be greatly accelerated upon microwave exposure instead of drying in an oven or furnace. Using this approach, anoporous and superhydrophobic silicas showing a wide variation in texture and morphology can be readily synthesized in roughly two hours. The effects of various sol-gel parameters solely on the textural properties of the organo-functional silica (OFS) have been investigated and discussed.

• Membrane Journal
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• v.24 no.3
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• pp.177-184
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• 2014

Silica membranes with high permeability were prepared using colloidal and polymeric silica sols on a porous stainless steel-tube support by a DRFF and SRFF method. Silica sols were derived with tetraethylorthosilicate (TEOS) by sol-gel method and analyzed with DLS, FE-SEM, and $N_2$ adsorption. The coating of the intermediate layer with colloidal silica sol on the stainless steel-tube support led to a denser surface morphology of the membrane along with a considerable reduction in the number of surface defect. As the polymeric silica sol enclosed the colloidal silica sol with spherical particles during the SRFF method, the separation-layer-coated silica membrane showed a denser surface than the intermediate layer. Moreover, the silica membranes showed high hydrogen gas permeability of $(6.63-9.21){\times}10^{-5}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ with low $H_2/N_2$ perm-selectivity (2.9-3.1) at room temperatures.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.164-171
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• 2012

Rice blast disease caused by Magnaporthe grisea (Hebert) Barr [teleomorph] is one of the most devastating diseases in rice plantation areas. Silicon is considered as a useful element for a large variety of plants. Rice variety MR219 was grown in the glasshouse to investigate the function of silicon in conferring resistance against blast. Silica gel was applied to soil while sodium silicate was used as foliar spray at the rates of 0, 60, 120, 180 g/5 kg soil and 0, 1, 2, 3 ml/l respectively. The treatments were arranged in a completely randomized design. Disease severity and silicon content of leaves were compared between the non-amended controls and rice plants receiving the different rates and sources of silicon. Silicon at all rates of application significantly (${\alpha}$ = 0.05) reduced the severity of disease with highest reduction (75%) recorded in treatments receiving 120 g of silica gel. SEM/EDX observations demonstrated a significant difference in weight concentration of silicon in silica cells on the leaf epidermis between silicon treated (25.79%) and non treated plants (7.87%) indicating that Si-fertilization resulted in higher deposition of Si in silica cells in comparison with non-treated plants. Application of silicon also led to a significant increase in Si contents of leaves. Contrast procedures indicated higher efficiency of silica gel in comparison to sodium silicate in almost all parameters assessed. The results suggest that mitigated levels of disease were associated with silicification and fortification of leaf epidermal cells through silicon fertilization.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.548-554
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• 2004

A sol-gel method was applied to coat TiO$_2$ on porous silica prepared using slurry foaming method from silica. from the results of XRD, SEM, and BET, the anatase phase was firstly observed at the coated supports with the heated of 50$0^{\circ}C$. The coated supports with the heated of $700^{\circ}C$ had the maximum anatase peak, and the particle size of coated TiO$_2$ was about 1 ${\mu}{\textrm}{m}$. Bending strength and gas permeability of the porous silica were measured for the feasibility as a catalytic supports. In case of the uncoated porous materials with the strength of 2.4 MPa, the strength increased to 3.9∼4.3 MPa after the coating process regardless of the heating temperature. On the other hand, the permeability of the uncoated porous materials decreased from 770${\times}$10$^{-13}$ $m^2$ to 363${\times}$10$^{-13}$ $m^2$ after the coating process, and it decreased with the increasing heating temperature.

• Korean Journal of Materials Research
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• v.13 no.3
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• pp.144-149
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• 2003

This study shows an experimental investigation of a reversible nano colloidal damper, which is statically loaded. The porous matrix is composed from silica gel (labyrinth or central-cavity architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis are described. Influence of the pore and particle diameters, particle architecture and length of the grafted molecule upon the reversible colloidal damper hysteresis is investigated, for distinctive types and mixtures of porous matrices. Variation of the reversible colloidal damper dissipated energy and efficiency with temperature, pressure, is illustrated. As a result, he proposed nano damper is effective one, which can be replaced the conventional damper.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.146-146
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• 2003

If rare earth ions could be activated by electrical means after introducing into an appropriate semiconductor host, it might be possible to achieve the electrically-driven optical amplifier. Futhermore, some groups report that rare earth doped semiconductor nanoparticls show the sensitized emission. In this study, we try to prepare the Er/PbS nanoparticles encaupsulated by phenyl modified silica shell via sol-gel process. Er/PbS nanoparticles were characterized by UV-vis absorption, XRD, FT-IR and TEM etc. Finally we will present the luminescence properties of Er doped PbS nanoencapsulation.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.264-272
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• 1998

The effect of catalytic condition on the properties of SiO2 aerogels has been investigated and then the dri-ed aerogels were partially densified to induce mechanical strength by heat treatment in order to prepare Type-VI silica by Sol-Gel method. Aerogel made by 1-step base process had the highest skeletal density lowest shrinkage and the smallest particle size. But in case of using acid catalyst in both 1st and 2nd step had the lowest skeletal density highest shrinkage and the largest particle size The aerogel synthesized by 1-step base process was most transparent because of its homogeneous microstructure. During heat treatments cracks occurred below 200$^{\circ}C$ for aerogel with the skeletal density lower than 1.9 g/cm3 but the with the higher skeletal density did not cracked up to 800$^{\circ}C$ shrinkage and skeletal density increased as heating temperature increased due to condensation and viscous sintering mechanism.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.605-609
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• 2008

This work describes the preparation of functionalized magnetic nanoparticles(MNPs) and their bioapplication to human DNA separation. Silica coated MNPs were prepared by changing the volume ratio of tetraethyl orthosilicate(TEOS) for controlled coating thickness on the original nanoparticle of MNPs. The sol-gel process in silica coating on MNPs surface was adapted for relatively mild reaction condition, low-cost, and surfactant-free. And then amino functionalized magnetic nanoparticles were synthesized using amine groups as surface modifiers. The result of adsorption efficiency for human DNA with amino-functionalized silica coated MNPs was calculated as a function of the number of amine groups.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.69-73
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• 2004

A series of $H_3PO_4$-doped composite membranes based on poly(vinyl alcohol)(PVA) and silica have been prepared by sol-gel process. The proton conductivity, as well as properties of swelling, methanol permeation, was measured in this study. The proton conductivity increased with the molar ratio of $H_3PO_4$ to silica. With the silica content increasing, swelling degree decreased and methanol permeability showed a slight increase. It suggested that the former was mainly determined by hydrophilicity of the membrane, while the latter was dominated by the interconnectivity of matrix. According to the value of on, the optimal conformations of these composite membranes were 60, 70, 80 wt.$\%$ of PS-x in membranes, where x were 1.5, 1.0, and 0.5, respectively. These composite membranes were thermal stability up to $200^{\circ}C$.