• Bulletin of the Korean Chemical Society
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• v.17 no.1
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• pp.66-68
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• 1996

It has been found that mesoporous structures of MCM-41 and MCM-48 disintegrate readily in distilled water around 370 K, while the structures can be stable in 100%-steam of 1 atmospheric pressure at much higher temperatures around 820 K. Thus, the structure disintegration is thermodynamically more favorable in water than under the steaming condition. X-ray powder diffraction and magic angle spinning 29Si NMR spectroscopy indicate that the disintegration of the mesoporous structures in water occurs due to silicate hydrolysis.

• Carbon letters
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• v.18
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• pp.62-66
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• 2016

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.379-384
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• 1997

High quality MCM-41 is prepared from a gel of molar composition SiO2:0.20 CTACl:0.18 TMAOH:25 H2O aged at 20 ℃ for 24 hours before crystallization lasting for 48 hours. The (110) and (200) peaks of XRD pattern of high quality MCM-41 are unusually well resolved and the FWHM (full-width-at-half-maximum) of the (100) peak is 0.13° for as-prepared MCM-41 and 0.21° for calcined one, which indicate well-developed crystals. The properties of the crystal depend on the source and concentration of the reactants and the gel aging time. There is no induction period in the course of the synthesis, which is conveniently monitored by pH measurement. Gel aging, during which a spatial distribution of silicate polyanions and micellar cations is established, is essential for preparing high quality MCM-41. Surfactants with the same cationic organic group but different counteranions change the crystallization behavior. Highly basic gel (pH=12.6) favours the lamellar product; the quality of MCM-41 is lower as insufficient TMAOH is available to dissolve the silica.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.144-146
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• 2011

Al-MCM-48 molecular sieves (Si/Al = 25, 50, 75 and 100) were synthesized hydrothermally using cetyltrimethyl ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and TEM images. The catalytic performance was evaluated in the vapour phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol (selectivity: 78%). Delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Though ester was used as the alkylating agent, phenyl isopropyl ether was not formed

• Journal of Environmental Science International
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• v.19 no.6
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• pp.681-687
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• 2010

Mesoporous silica was prepared from hydrothermal synthesis using gel mixture of tetraethylorthosilcate (TEOS) as silica source and cetyltrimethylammonium bromide (CTMABr) as a surfactant. 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, TEM and BET. Also, surface potential of mesoporous silica was measured using zeta potential. $N_2$ 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. As a result, SBET of $100m^2/g{\sim}1500m^2/g$ was determined from the $N_2$ adsorption isotherm. Also, the average pore diameter was 2 nm∼4 nm. Mesoporous silica's surface potential of minus charge was determined from zeta potential.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.2
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• pp.49-52
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• 1998

이동통신용 핵심 부품인 W-LAN용 RF-Switch를 설계 및 제작하였다. 본 연구에서 는 CAD를 이용한 전송선로 설계기술, 소형화, 다층화 설계기술, 이동통신용 MCM 부품의 패턴설계를 개발하였으며 RF-Switch 설계하는기법 소형화 및 다층화를 위한 MCM공법을 얻을수 있었다. Ant-Rx On시 삽입손실은 0.48dB로 나타났다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1915-1922
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• 2012

In this study, synthesis of mesoporous silica such as, SBA-15, MCM-41, MCM-48, KIT-6 according to various experimental conditions. The CMK(Carbon Mesoporous Korea) was synthsized by various mesoporous silica. Finally, the mesoporous transition metal structure synthesized using CMK structure. Nitrogen adsorption/ desorption, SEM, low angle X-ray diffraction were carried for analysis of each sample. The optimum synthesis condition of mesoporous transition metal structure derived from characteristic analysis. The SBA-15 is best precursor for synthesis of mesoporous transition metal structure. The surface area of copper mesorporous structure from CMK(SBA-15) is $225m^2/g$, pore diameter is 2.91nm by BET analysis.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.258-262
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• 2008

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2007.05a
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• pp.328-330
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• 2007

• Clean Technology
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• v.14 no.1
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• pp.40-46
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• 2008

The dehumidifiers were prepared by the impregnation of the zeolites such as MCM 48, USY, beta on the silica ceramic paper. Their capacities for $H_2O$ absorption and regeneration of the bed were tested in a fixed bed reactor system. The $H_2O$ absorption capacities of the dehumidifiers impregnated with the zeolites were $1.5{\sim}2$ times higher than those without the zeolites. Especially, the humidifier using MCM 48 and colloidal silica showed an excellent capacity (42.1g $H_2O/g$ absorbent). It was found that the $H_2O$ absorption capacities of the dehumidifiers were improved because the amount of silica gel, the main component in absorbing $H_2O$, increased due to the large surface area and pore volume of the zeolites. In addition, $H_2O$ was easily desorbed from the dehumidifiers with zeolites at $80^{\circ}C$ of regeneration temperature and the desorption amount of $H_2O$ was the same as that absorbed. It was confirmed that the $H_2O$ absorption capacities of the dehumidifiers impregnated with zeolite were maintained without deactivation through the repeated cyclic experiments.