• Title/Summary/Keyword: Mesoporous $SiO_2$

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Surface Charge and Morphological Characterization of Mesoporous Cellular Foam Silica/Nafion Composite Membrane by Using EFM (정전기력 현미경을 사용한 메조포러스 실리카/나피온 합성 이온교환막의 표면 전하 및 모폴로지 연구)

  • Kwon, Osung
    • New Physics: Sae Mulli
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    • v.68 no.11
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    • pp.1173-1182
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    • 2018
  • Mesoporous silica allows proper hydration of an ion exchange membrane under low relative humidity due to its strong hydrophilicity and structural characteristic. A mesoporous silica and Nafion composite membrane shows good proton conductivity under low relative humidity. An understanding of ion-channel formation and proton transfer through an ion-channel network in mesoporous silica and Nafion composite membranes is essential for the development and the optimization of ion exchange membranes. In this study, a mesoporous cellular foam $SiO_2/Nafion$ composite membrane is fabricated, and its proton conductivity and performance are measured. Also, the ion-channel distribution is analyzed by using electrostatic force microscopy to measure the surface charge density of the mesoporous cellular foam $SiO_2/Nafion$ composite membrane. The research reveals a few remarkable results. First, the composite membrane shows excellent proton conductivity and performance under low relative humidity. Second, the composite membrane is observed to form ion-channel-rich and ion-channel-poor region locally.

Toluene Decompositions over Al-W-incorporated Mesoporous Titanosilicates Photocatalysts

  • Lee, Ye-Ji;Kim, Young-Mi;Jeong, Ha-Rim;Yeo, Min-Kyeong;Kang, Mi-Sook
    • Bulletin of the Korean Chemical Society
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    • v.30 no.1
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    • pp.107-113
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    • 2009
  • This study investigated the decomposition activities of toluene on 10 mol% Al-W-incorporated mesoporous titano (15 mol %) silicates. The mesopore sizes observed in the transmission electron microscopy images ranged from 2.0 to 5.0 nm, and the pores were irregular on the addition of 10 mol% Al or W ions, but changed to regular hexagonal forms with the simultaneous additions of Al and W. The X-ray photon spectroscopy results showed a shift of the special peak for Ti2p in Al-incorporated mesoporous titanosilicates to a stronger binding energy compared to those of mesoporous titanosilicates and Al-incorporated mesoporous titanosilicates. Three O1s peaks in the spectra of the Al and W coexisted samples were observed at 530.5 and 531.7, 533, and 533.7eV, which were assigned to $Ti-Os\;in\;TiO_2\;and\;Ti_2O_3,\;Si-O\;in\;SiO_2\;and\;Al-O\;in\;Al_2O_3$, respectively. The toluene molecules desorbed at lower temperatures over W-incorporated mesoporous titanosilicates, and the amounts of toluene desorbed were also small; however, Al-incorporated mesoporous titanosilicates adsorbed much more toluene, particular over $Al_7.5-W_2.5-Ti_15-Si_75$. The photocatalytic decomposition of toluene was more enhanced over $Al_7.5-W_2.5-Ti_15-Si_75$ than over Al- or W-incorporated mesoporous titanosilicates only.

Preparation and Characterization of Mesoporous Ceramic Materials (메조기공 세라믹 소재의 형성과 특성 분석)

  • Ha, Tae-Jung;Park, Hyung-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.8
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    • pp.593-601
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    • 2012
  • Ordered mesoporous oxide films have been focused because of their low density, high interior specific surface area, and high thermal insulation. Specially, the ordered mesoporous oxide films prepared by self-assembly has many advantages due to easy process and high reproducibility. In this work, ordered mesoporous $SiO_2$, $Al_2O_3$, and $TiO_2$ films were synthesized by control of composition and processing parameter. Also, their structural, thermal, and mechanical properties were characterized variously. In conclusion, ordered mesoporous oxides will be one of core materials in new technology due to their excellent and unique properties.

The Tribological Behaviors of Mesoporous $SiO_2$ Thin Film Formed by Sol-Gel and Self-Assembly Method (졸겔법과 자가조립법을 통해 제조된 메조포러스 $SiO_2$ 박막의 트라이볼로지 특성)

  • Lee, Young-Ze;Shin, Yun-Ha;Kim, Ji-Hoon;Kim, Ji-Man;Kim, Tae-Sung
    • Tribology and Lubricants
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    • v.23 no.6
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    • pp.298-300
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    • 2007
  • Frictional characteristics of mesoporous $SiO_2$ thin films were evaluated with different pore sizes. The films were manufactured by sol-gel and self-assembly methods to have a porous structure. The pores on the surface may play as the outlet of wear particle and the storage of lubricant so that the surface interactions could be improved. The pores were exposed on the surface by chemical mechanical polishing (CMP) or plasma-etching after forming the porous films. The ball-on-disk tests with mesoporous $SiO_2$ thin films on glass specimen were conducted at sliding speed of 15 rpm and a load of 0.26 N. The results show considerable dependency of friction on pore size of mesoporous $SiO_2$ thin films. The friction coefficient decreased as increasing the pore size. CMP process was very useful to expose the pores on the surface.

Mesoporous SiO2 Mediated Polybenzimidazole Composite Membranes for HT-PEMFC Application (고온 PEMFC 응용을 위한 다공성 SiO2 기반 폴리벤즈이미다졸 복합막)

  • HAN, DAEUN;YOO, DONG JIN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.2
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    • pp.128-135
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    • 2019
  • In this study, the mesoporous $SiO_2$ (5, 10, or 15 wt%) was incorporated into the polybenzimidazole matrix in order to improve the proton conduction as well as physiochemical properties of composite membrane. The chemical structure of mesoporous $SiO_2$ and crystallinity of as-prepared membranes were analyzed by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis, respectively. The thermal stability of the pristine $X_1Y_9$ and composite membranes were evaluated by thermogravimetric analyzer (TGA). On other side, the physical and chemical properties of the pristine $X_1Y_9$ and composite membranes were also determined by acid uptake and oxidative stability tests, respectively. With the incorporation of 15 wt% $SiO_2$, the composite membrane exhibits the higher proton conductivity that may be applicable for non-humidified high temperature fuel cell applications.

Preparation of Mesoporous Molecular Sieve by the Reaction of Na2SiO3 and H2SiF6 in the Presence of an Aqueous Nonionic Surfactant Solution (비이온성 계면활성제 수용액에서 Na2SiO3와 H2SiF6의 반응을 통한 메조포러스 실리카의 제조)

  • Kim, Jin-Yeong;Kwon, Oh-Yun
    • Applied Chemistry for Engineering
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    • v.29 no.1
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    • pp.122-126
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    • 2018
  • Mesoporous molecular sieves were prepared by the reaction of $Na_2SiO_3$ and $H_2SiF_6$ using nonionic micelle templates in an aqueous solution. Well-crystalline mesoporous molecular sieves were obtained after several seconds at atmospheric conditions. Powder samples exhibited d-spacing of 3.8-5.1 nm with the sharpness of the d00l peak, showing well-crystalline mesoporous molecular sieves, pore size distributions of 2.5-3.1 nm and large specific surface areas of $290-1,018m^2/g$, depending on types of surfactants. SEM images of samples showed well-divided spherical particles with an uniform size of ${\sim}0.5{\mu}m$ and TEM images demonstrated uniform pores with a worm hole shape.

One-pot Synthesis of Multifunctional Mn3O4/mesoporous Silica Core/shell Nanoparticles for Biomedical Applications

  • Lee, Dong Jun;Lee, Nohyun;Lee, Ji Eun
    • Applied Chemistry for Engineering
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    • v.33 no.1
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    • pp.113-118
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    • 2022
  • Multifunctional nanomaterials based on mesoporous silica nanoparticles (MSN) and metal oxide nanocrystals are among the most promising materials for theragnosis because of their ease of modification and high biocompatibility. However, the preparation of multifunctional nanoparticles requires time-consuming multistep processes. Herein, we report a simple one-pot synthesis of multifunctional Mn3O4/mesoporous silica core/shell nanoparticles (Mn3O4@mSiO2) involving the temporal separation of core formation and shell growth. This simple procedure greatly reduces the time and effort required to prepare multifunctional nanoparticles. Despite the simplicity of the process, the properties of nanoparticles are not markedly different from those of core/shell nanoparticles synthesized by a previously reported multistep process. The Mn3O4@mSiO2 nanoparticles are biocompatible and have potential for use in optical imaging and magnetic resonance imaging.

ZnO/SiO2 Prepared by Atomic Layer Deposition as Adsorbents of Organic Dye in Aqueous Solution and Its Photocatalytic Regeneration

  • Jeong, Bora;Jeong, Myung-Geun;Park, Eun Ji;Seo, Hyun Ook;Kim, Dae Han;Yoon, Hye Soo;Cho, Youn Kyoung;Kim, Young Dok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.167.2-167.2
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    • 2014
  • In this work, ZnO shell on mesoporous $SiO_2$ ($ZnO/SiO_2$) was prepared by atomic layer deposition (ALD). Diethylzinc (DEZ) and $H_2O$ were used as precursor of ZnO shell. $ZnO/SiO_2$ sample was characterized by X-ray diffraction (XRD), N2 sorption isotherms, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR). $ZnO/SiO_2$ showed higher adsorption capacity of MB than that of bare mesoporous $SiO_2$ and the adsorption capacities of $ZnO/SiO_2$ could be regenerated by UV exposure through the photocatalytic degradation of the adsorbed MB. This system could be used for removing organic dye from water by adsorption and reused after saturation of adsorption due to its photocatalytic regeneration.

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Carbon Dioxide Reforming of Methane Over Mesoporous $Ni/SiO_2$ Catalyst

  • Kim, Dae Han;Sim, Jong Ki;Seo, Hyun Ook;Jeong, Myung-Geun;Kim, Young Dok;Lim, Dong Chan;Kim, Sang Hoon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.166-166
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    • 2013
  • Mesoporous $SiO_2$-supported Ni catalysts (Ni/$SiO_2$ and Ni/$TiO_2$/$SiO_2$) were fabricated by atomic layer deposition (ALD), and their catalytic activity and stability were investigated in carbon dioxide reforming of methane (CRM) reaction at $800^{\circ}C$ The Ni/$SiO_2$ catalysts showed high stability as a result of confinement of Ni particles with a mean size of ~10 nm within the pores of $SiO_2$ support. Besides, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the Ni nanoparticles were partially buried inside the $SiO_2$ support. The strong interaction between Ni and the $SiO_2$ support could also be advantageous for long-term stability of the catalyst. In case of the Ni/$TiO_2$/$SiO_2$ catalyst, it was found that the catalytic activity of 10 nm-sized Ni nanoparticles was not much influenced by $TiO_2$ addition.

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Adsorption Behavior of Environmental Hormone Bisphenol A onto Mesoporous Silicon Dioxide

  • Fan, Xianghong;Tu, Bing;Ma, Hongmei;Wang, Xuefen
    • Bulletin of the Korean Chemical Society
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    • v.32 no.8
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    • pp.2560-2564
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    • 2011
  • Mesoporous silicon dioxide (meso-$SiO_2$) was prepared using cetyltrimethylammonium bromide as the structure-directing reagent and tetraethyl orthosicate as the silicon source. The influence of pH value on the adsorption behavior of bisphenol A (BPA) was investigated. The adsorption capacity of BPA onto meso-$SiO_2$ increases slightly with pH value from 2 to 6, and then gradually decreases as further improving pH value. The effect of temperature was also studied, and the adsorption capacity of BPA gradually declines with increasing temperature. The adsorption kinetics and thermodynamics of BPA were examined. It is found that the adsorption of BPA onto meso-$SiO_2$ is in good agreement with Langmuir adsorption model. The rate constant of adsorption is $5.17{\times}10^{-3}g\;mg^{-1}\;min^{-1}$, and the maximum adsorption capacity is as high as 353.4 $mg\;g^{-1}$ at 20 $^{\circ}C$.