• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.52-59
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• 2000

The reaction gel mixtures of molar composition (0.3${\sim}$2.1) $SiO_2:\;(0.10{\sim}0.50)\;CTABr:\;0.15{\sim}0.23)\;TMAOH:\;(20{\sim}100)\;H_2O$ we prepared and then aged at room temperature for a definite duration. The aged gel is reacted hydrothermally at $150^{\circ}C$ for 2 days. The pH of reaction gel during synthesis is strongly influenced by the concentration of TMAOH and silica source. The pH change affects the phase of product, which is monitored by X-ray diffractometer. With increasing the TMAOH ratio from 0.19 to 0.23, the gel becomes more basic, and the product involves more lamellar phase. At TMAOH ratio lower than 0.19, the hexagonal phase is lower with decrease of pH. The content of the lamellar phase increases at a lower $SiO_2$ concentration, and higher concentrations have a clear detrimental effect on the crystallinity ofMCM-41 due to an excess silica source. The best quality MCM-41 is synthesized from a reaction gel composition of $1.0\;SiO_2:\;0.27\;CTABr:\;0.19\;TMAOH:\;40\;H_2O$. The pH values of this gel, aged one for 24 hr, and reacted one at $150^{\circ}C$ for 2 days are 12.3, 11.5, and 10.5, respectively. Gel aging for 24 h is essential for preparing high quality MCM-41. Longer aging causes a decrease of hexagonal phase.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.130-132
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• 2006

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.1
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• pp.43-48
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• 2006

In this Part 2, the grain growth processes of $Al_2O_3$ ceramics is numerically simulated using Monte Carlo method (MCM) and finite element method (FEM) and the pore sizes are analyzed. As the green ceramics whose thermal conductivities in high temperatures are generally low are sintered by the plasma heat and are rapidly cooled, the grain growth of the sintered body in the center is different from that in the outer. Also, even in the same sintering temperature, the pore size differs according to the pressing pressure. In order to prove the difference, the temperature distribution of the sintered body was analyzed using the finite element method and then the grain growth process associated with pressing pressures and relative densities was simulated using Monte Carlo method.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.6
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• pp.673-679
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• 2008

In this study, Mesoporous silica were prepared from hydrothermal synthesis using gel mixture of tetraethylorthosilcate (TEOS) as silica source and cetyltrimethylammonium bromide(CTMABr) as a template. In the optimum synthesis cause, molar ratio of template and silica changed. The surface and structure properties of Mesoporous silica were determined by XRD, SEM, and BET. N$_2$ adsorption isotherm characteristics, including the specific surface area(S$_{BET}$), total pore volume(V$_T$), and average pore diameter(D$_{BJH}$), were determined by BET. Also, the adsorption character of Pb(II) and Cd(II) ion on Mesoporous silica were measured using ICP. As a result, a SBET of 100$\sim$1,500 m$^2$/g was determined from the N$_2$ adsorption isotherm. Also, the average pore diameter of 2$\sim$4 nm. The adsorption of Pb ion and Cd ion on Mesoporous silica become different depending on the pH of solution. The adsorption amount of Mesoporus silica had higher than that of silicagel.