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

• Prospectives of Industrial Chemistry
• /
• v.17 no.2
• /
• pp.8-20
• /
• 2014

나노세공체는 고표면적, 균일한 다공성, 분자크기의 세공구조, 높은 흡착용량, 이온교환 특성, 높은 촉매활성, 분자크기의 형상선택성 등의 특징을 갖기 때문에 촉매 및 흡착제로 나노소재 분야에서 가장 오랫동안 활용되어 왔던 중요한 물질 가운데 하나로 정유 및 석유화학 산업을 비롯한 화학산업과 환경 산업에 광범위하게 사용되고 있다. 본 고찰에서는 결정성 나노세공체 가운데 가장 중요한 제올라이트와 최근 연구가 활발한 하이브리드 나노세공체의 산업적 응용 및 기술개발 동향과 향후 발전 전망에 대해 간략히 기술하였다.

• Korean Journal of Materials Research
• /
• v.24 no.11
• /
• pp.573-577
• /
• 2014

The existing metal getters are invariably covered with thin oxide layers in air and the native oxide layer must be dissolved into the getter materials for activation. However, high temperature is needed for the activation, which leads to unavoidable deleterious effects on the devices. Therefore, to improve the device efficiency and gas-adsorption properties of the device, it is essential to synthesize the getter with a method that does not require a thermal activation temperature. In this study, getter material was synthesized using palladium oxide (PdOx) which can adsorb $H_2$ gas. To enhance the efficiency of the hydrogen and moisture absorption, a porous layer with a large specific area was fabricated by an etching process and used as supporting substrates. It was confirmed that the moisture-absorption performance of the $SiO_2/Si$ was characterized by water vapor volume with relative humidity. The gas-adsorption properties occurred in the absence of the activation process.

• Journal of Sensor Science and Technology
• /
• v.29 no.6
• /
• pp.374-381
• /
• 2020

Hydrogen gas has attracted considerable attention as a promising candidate for future energy resources because of its eco-friendly characteristics; however, its highly combustible characteristics should be thoroughly examined to preclude potential disasters. In this regard, a highly sensitive method for the selective detection of H₂ is extremely important. To achieve excellent H₂ selectivity, the utilization of a metal-organic framework (MOF) membrane can physically screen interfering gas molecules by restricting the size of kinetic diameters that can penetrate its nanopores. This paper summarizes the various endeavors of researchers to utilize the MOF molecular sieving layer for the development of highly selective H₂ sensors. Further, the review affords useful insights into the development of highly reliable H₂ sensors.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2005.09a
• /
• pp.183-187
• /
• 2005

Thin films of diblock copolymers may be suitable for semiconductor device applications since they enable patterning of ordered domains with dimensions below photolithographic resolution over wafer-scale area. We obtained nanometer-scale cylindrical structure of dibock copolymer of polystyrene-block-poly(methylmethacrylate), PS-b-PMMA, also demonstrate pattern transfer of the nanoporous polymer using both reactive ion etching. The size of fabricated naonoholes were about 10 nm. Fabricated nanopattern surface was observed by field emission scanning electron microscope (FESEM).

• Carbon letters
• /
• v.25
• /
• pp.103-112
• /
• 2018

Hierarchically porous, chemically activated carbon materials are readily derived from biomass using hydrothermal carbonization (HTC) and chemical activation processes. In this study, empty fruit bunches (EFB) were chosen as the carbon source due to their sustainability, high lignin-content, abundance, and low cost. The lignin content in the EFB was condensed and carbonized into a bulk non-porous solid via the HTC process, and then transformed into a hierarchical porous structure consisting of macro- and micropores by chemical activation. As confirmed by various characterization results, the optimum activation temperature for supercapacitor applications was determined to be $700^{\circ}C$. The enhanced capacitive performance is attributed to the textural property of the extremely high specific surface area of $2861.4m^2\;g^{-1}$. The prepared material exhibited hierarchical porosity and surface features with oxygen functionalities, such as carboxyl and hydroxyl groups, suitable for pseudocapacitance. Finally, the as-optimized nanoporous carbons exhibited remarkable capacitive performance, with a specific capacitance of $402.3F\;g^{-1}$ at $0.5A\;g^{-1}$, a good rate capability of 79.8% at current densities from $0.5A\;g^{-1}$ to $10A\;g^{-1}$, and excellent life cycle behavior of 10,000 cycles with 96.5% capacitance retention at $20A\;g^{-1}$.

• Carbon letters
• /
• v.13 no.4
• /
• pp.254-259
• /
• 2012

Nanoporous non-woven carbon fibers for a gas sensor were prepared from a pitch/polyacrylonitrile (PAN) mixed solution through an electrospinning process and their gas-sensing properties were investigated. In order to create nanoscale pores, magnesium oxide (MgO) powders were added as a pore-forming agent during the mixing of these carbon precursors. The prepared nanoporous carbon fibers derived from the MgO pore-forming agent were characterized by scanning electron microscopy (SEM), $N_2$-adsorption isotherms, and a gas-sensing analysis. The SEM images showed that the MgO powders affected the viscosity of the pitch/PAN solution, which led to the production of beaded fibers. The specific surface area of carbon fibers increased from 2.0 to $763.2m^2/g$ when using this method. The template method therefore improved the porous structure, which allows for more efficient gas adsorption. The sensing ability and the response time for the NO gas adsorption were improved by the increased surface area and micropore fraction. In conclusion, the carbon fibers with high micropore fractions created through the use of MgO as a pore-forming agent exhibited improved NO gas sensitivity.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.2
• /
• pp.322-326
• /
• 2009

In this work, nanoporous $TiO_2$ powder was fabricated using Ketjen black, and applied in photovoltaic device based on the Dye-sensitized Solar Cells (DSCs). $TiO_2$ powder was fabricated using Ti-isopropoxide and 2-propanol by sol-gel combustion method. For added $0{\sim}2g$ variable of Ketjen black, characteristic of porosity, size of particle and crystallite of obtained $TiO_2$ nano powder was investigated. The photovoltaic efficiency of the prepared DSCs was measured using $TiO_2$ film which prepared on each different heat treatment temperature($100^{\circ}C{\sim}600^{\circ}C$) with paste of $TiO_2$ powder. The porosity and size in particle of $TiO_2$ powder made with Ketjen black Ig was influenced significantly effect to DSCs characteristic. Heat treatment at $500^{\circ}C$ makes the better photovoltaic efficiency which around 6.11%($J_{sc}=13.35mA/cm^2$, $V_{oc}=0.73V$, ff=0.63). The sol-gel combustion method was useful to DSCs fabrication.

• Journal of the Korean institute of surface engineering
• /
• v.54 no.5
• /
• pp.222-229
• /
• 2021

Icing causes various serious problems, where water vapor or water droplets adhere at cold conditions. Therefore, understanding of ice adhesion on solid surface and technology to reduce de-icing force are essential for surface finishing of metallic materials used in extreme environments and aircrafts. In this study, we controlled wettability of aluminum alloy using anodic oxidation, hydrophobic coating and lubricant-impregnation. In addition, surface porosity of anodized oxide layer was controlled to realize superhydrophilicity and superhydrophobicity. Then, de-icing force on these surfaces with a wide range of wettability and mobility of water was measured. The results show that the enhanced wettability of hydrophilic surface causes strong adhesion of ice. The hydrophobic coating on the nanoporous anodic oxide layer reduces the adhesion of ice, but the volume expansion of water during the freezing diminishes the effect. The lubricant-impregnated surface shows an extremely low adhesion of ice, since the lubricant inhibits the direct contact between ice and solid surface.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.7
• /
• pp.1075-1078
• /
• 2005

Hydrogen adsorption on various porous materials have been studied with a volumetric method at low temperature in the pressure of 0-760 torr. Their hydrogen uptakes depend at least partly on microporosity rather than total porosity. However, it is also necessary to consider other parameters such as pore size and pore architecture to explain the adsorption capacity. The heat of adsorption and adsorption-desorption-readsorption experiments show that the hydrogen adsorption over the porous materials are composed of physisorption with negligible contribution of chemisorption. Among the porous materials studied in this work, SAPO-34 has the highest adsorption capacity of 160 mL/g at 77 K and 1 atm probably due to high micropore surface area, micropore volume and narrow pore diameter.