• Journal of Environmental Science International
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• v.21 no.7
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• pp.787-795
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• 2012

The purpose of this study is to synthesize transition metal doped mesoporous silica catalyst and to characterize its surface in an attempt to decomposition of $N_2O$. Transition metal used to surface modification were Ru, Pd, Cu and Fe concentration was adjusted to 0.05 M. The prepared mesoporous silica catalysts were characterized by X-ray diffraction, BET surface area, BJH pore size, Scanning Electron Microscopy and X-ray fluorescence. The results of XRD for mesoporous silica catalysts showed typical the hexagonal pore system. BET results showed the mesoporous silica catalysts to have a surface area of 537~973 $m^2/g$ and pore size of 2~4 nm. The well-dispersed particle of mesoporous silica catalysts were observed by SEM, the presence and quantity of transition metal loading to mesoporous surface were detected by XRF. The $N_2O$ decomposition efficiency on mesoporous silica catalysts were as follow: Ru>Pd>Cu>Fe. The results suggest that transition metal doped mesoporous silica is effective catalyst for decomposition of $N_2O$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.159.1-159.1
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• 2014

We report a simple method for preparing hydrophobic mesoporous silica and its use as a pre-concentrating agent of gas analytes. Hydrophobic mesoporous silica was prepared by coating PDMS (polydimethylsiloxane) thin layer on commercial mesoporous silica with thermal deposition method in a sealed chamber. By using this method, we were able to coat PDMS layer on inner-walls of pores larger than 15 nm. Also, contact angle measured on a surface consisting of PDMS-coated mesoporous silica exceeded $150^{\circ}$, implying that the surface has high water repellency. Pre-concentration ability of PDMS-coated mesoporous silica and baremesoporous silica was tested under dry and humid conditions. Adsorption and molecular desorption of gas analytes was much enhanced by PDMS-coating on mesoporous silica under both dry and humid conditions. Therefore we suggest that PDMS-coated mesoporous silica can be an efficient pre-concentration agent in order to enhance sensitivity of various detectors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.159-159
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• 2007

In order to reduce a signal delay in ULSI, low resistive metal and intermetal dielectric material of low dielectric constant are required. Ordered mesoporous silica film is proper to intermetal dielectric due to its low dielectric constant and superior mechanical properties. In this study, ordered mesoporous silica films was synthesized using TEOS (tetraethoxysilane) / MTES (methyltriethoxysilane) mixed silica precursor and Brij-$76^{(R)}$ surfactant. These films had the porosity of 40% and dielectric constant of 2.5. To lower dielectric constant, the ordered mesoporous silica films were surface-modified by HMDS (hexamethyldisilazane) treatment. HMDS substituted -OH groups on the surface of silica wall for -Si$(CH_3)_3$ groups. After the HMDS treatment, ordered mesoporous silica films were calcined at various calcination temperatures. Through the investigation, it was concluded that the proper calcination temperature is necessary as aspects of structural, electrical, and mechanical properties.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.167-169
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• 2021

In this study, monodispersive silica nanoparticles with double mesoporous shells were synthesized, and the pore size of synthetic mesoporous silica nanoparticles was controlled. Cetyltrimethylammonium chloride (CTAC), N, N-dimethylbenzene, and decane were used as soft template and induced to form outer mesoporous shell. The resultant double mesoporous silica nanoparticles were consisted of two layers of shells having different pore sizes, and it has been confirmed that outer shells with larger pores (Mean pore size > 2.5 nm) are formed directly on the surface of the smaller pore sized shell (Mean pore size < 2.5 nm). It was confirmed that the regulation of the molar ratio of pore expansion agents plays a key role in determining the pore size of double mesoporous shells.

• 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 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.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1562-1566
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• 2006

Mesoporous silica films with three different pore sizes were prepared by using cationic surfactant, non-ionic surfactant, or triblock copolymer as structure directing agents with tetramethylorthosilicate as silica source in order to control the pore size and wall thickness. They were synthesized by an evaporation-induced self-assembly process and spin-coated on Si wafer. Mesoporous silica films with three different pore sizes of 2.9, 4.6, and 6.6 nm and wall thickness ranging from $\sim$1 to $\sim$3 nm were prepared by using three different surfactants. These materials were optically transparent mesoporous silica films and crack free when thickness was less than 1 m m. The photoluminescence spectra found in the visible range were peaked at higher energy for smaller pore and thinner wall sized materials, consistent with the quantum confinement effect within the nano-sized walls of the silica pores.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.186-190
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• 2011

Periodically ordered mesoporous manganese oxides were synthesized in a single and double replication procedure. Mesoporous SBA-15 and -16 silica and their reverse replica carbons were successively used as hard templates. The silica and carbon pore systems were infiltrated with $Mn(NO_3)_2{\cdot}xH_2O$ or $Mn(AcAc)_2$, which was then converted to $Mn_2O_3$ at 873 K; the silica and carbon matrix were finally removed by NaOH solution or calcinations in air. The structure of the mesoporous $Mn_2O_3$, using a carbon template, corresponds to that of the original SBA-15 and SBA-16 silica. The products consist of hexagonally arranged cylindrical mesopores with crystalline pore walls or cubic mesoporous pores. The structure of replica has been confirmed by XRD, TEM analysis, and its electrochemical properties were tested with cyclic voltammetry. Formation of $Mn_2O_3$ inside the mesoporous carbon pore system showed much improved electrical properties.

• Journal of the Korean Institute of Gas
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• v.13 no.5
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• pp.26-32
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• 2009

Ni catalysts on mesoporous silica and commercial silica were prepared for the methanation. XRD and TPR analyses indicated that Ni/mesoporous silica had smaller metal particle size and higher metal dispersion than that of Ni/commercial silica. In addition, Ni/mesoporous silica had stronger metal-support interaction. In methanation, Ni/mesoporous silica showed higher CO conversion and methane yield (65%) than Ni/commercial silica (58%). In the characterization results of catalysts after reaction, Ni/commercial silica was deactivated by the collapse of structure and metal sintering, but Ni/mesoporous silica showed stable catalytic performance.

• Journal of Environmental Science International
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• v.22 no.7
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• pp.837-845
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• 2013

This study was designed to synthesize mesoporous carbon, porous carbonic material and to characterize its surface in an attempt to adsorption methane gas($CH_4$). Synthesis of mesoporous carbon was carried out under two steps ; 1. forming a RF-silica complex with a mold using CTMABr, a surfactant, and TEOS, raw material of silica, and 2. eliminating silica through carbonization and HF treatment. The mesoporous carbon was synthesized under various conditions of synthesis time and calcination. Eight different types of mesoporous carbon, which were designated as MC1, MC2, MC3, MC4, MCT1, MCT2, MCT3, and MCT4, were prepared depending upon preparation conditions. The analysis of mesoporous carbon characteristics showed that the calcination of silica stabilized the mixed structure of silica and carbonic complex, and made the particle uniform. The results also showed that hydrothermal synthesis time did not have a strong influence on the size of pore. The bigger specific surface area was obtained as the hydrothermal synthesis time was extended. However, the specific surface area was getting smaller again after a certain period of time. In adsorption experiments, $CH_4$ was used as adsorbate. For the case of $CH_4$, MCT3 showed the highest adsorption efficiency.