• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.167-172
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• 2011

In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

• Design & Manufacturing
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• v.15 no.2
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• pp.11-16
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• 2021

Recently, three-dimensional (3D) cell culture systems, which are superior to conventional two-dimensional (2D) vascular systems that mimic the in vivo environment, are being actively studied to reproduce drug responses and cell differentiation in organisms. Conventional two-dimensional cell culture methods (scaffold-based and non-scaffold-based) have a limited cell growth rate because the culture cannot supply the culture medium as consistently as microvessels. To solve this problem, we would like to propose a 3D culture system with an environment similar to living cells by continuously supplying the culture medium to the bottom of the 3D cell support. The 3D culture system is a structure in which microvascular structures are combined under a scaffold (agar, collagen, etc.) where cells can settle and grow. First, we have manufactured molds for the formation of four types of microvessel-mimicking chips: width / height ①100 ㎛ / 100 ㎛, ②100 ㎛ / 50 ㎛, ③ 150 ㎛ / 100 ㎛, and ④ 200 ㎛ / 100 ㎛. By injection molding, four types of microfluidic chips were made with GPPS (general purpose polystyrene), and a 100㎛-thick PDMS (polydimethylsiloxane) film was attached to the top of each microfluidic chip. As a result of observing the flow of the culture medium in the microchannel, it was confirmed that when the aspect ratio (height/width) of the microchannel is 1.5 or more, the fluid flows from the inlet to the outlet without a backflow phenomenon. In addition, the culture efficiency experiments of colorectal cancer cells (SW490) were performed in a 3D culture system in which PDMS films with different pore diameters (1/25/45 ㎛) were combined on a microfluidic chip. As a result, it was found that the cell growth rate increased up to 1.3 times and the cell death rate decreased by 71% as a result of the 3D culture system having a hole membrane with a diameter of 10 ㎛ or more compared to the conventional commercial. Based on the results of this study, it is possible to expand and build various 3D cell culture systems that can maximize cell culture efficiency by cell type by adjusting the shape of the microchannel, the size of the film hole, and the flow rate of the inlet.

• Membrane Journal
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• v.30 no.6
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• pp.409-419
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• 2020

In this study, PEBAX/ZIF-8 and PEBAX/amineZIF-8 composite membranes were prepared according to the content of zeolitic imidazolate framework-8 (ZIF-8), amine-modified ZIF-8 (amineZIF-8), the gas permeability properties of N2 and CO2 were investigated for each composite membrane. In the case of the PEBAX/ZIF-8 composite membrane, the permeability of N2 and CO2 increased as the ZIF-8 content increased, and in the case of the PEBAX/amineZIF-8 composite membrane, the permeability of N2 and CO2 increased up to 20 wt% of amineZIF-8, but decreased at the higher content. CO2/N2 ideal selectivity increased up to 20 wt% of ZIF-8 and amineZIF-8 contents in both PEBAX/ZIF-8 and PEBAX/ amineZIF-8 composite membranes, and then decreased thereafter, in the case of PEBAX/amineZIF-8 composite membrane was less decreased. The reason for the highest CO2/N2 ideal selectivity at 20 wt% of amineZIF-8 is that amine modification improved the compatibility between PEBAX and amineZIF-8, and thus amineZIF-8 was evenly dispersed in PEBAX, resulting in the greatest effect of the porous ZIF-8 with a 3.4 Å pore size and the amine with affinity for CO2.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.11-16
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• 2022

Metal-organic frameworks (MOFs) are porous materials with nano-sized pores. The degree of gas adsorption and pore size can be controlled according to types of metal ions and organic ligands. Many studies have been conducted on MOFs in the fields of gas storage and separation, and gas sensors. For rapid and quantitative gas adsorption/desorption analyses, it is necessary to form various MOF structures in uniform films on a sensor surface. In this review, some of representative direct methods for uniformly synthesizing MOFs such as MIL-53 (Al), ZIF-8, and Cu-BDC from anodized aluminum oxide, zinc oxide nanorods, and copper thin films, respectively on the surface of a microresonator are highlighted. In addition, the operation principle of quartz crystal microbalance and microcantilever, which are representative microresonators, and the interpretation of signals that change when gas is adsorbed to MOFs are covered. This is intended to enhance the understanding of gas adsorption/desorption analysis of MOFs using microresonators.

• Korean Journal of Food Science and Technology
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• v.54 no.4
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• pp.414-421
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• 2022

The purpose of this study was to evaluate the quality characteristics and antioxidant activity of Jeung-pyun containing 0, 2.5, 5, 7.5, and 10% Rudbeckia laciniata L. powder. In this study, increase in the content of Rudbeckia laciniata L. powder led to an increase in pH, hardness, adhesiveness, chewiness, and gumminess while moisture of Jeung-pyun had decreased. Scanning electron microscopy analysis showed that the pores in Jeung-pyun merged leading to a decrease in the number of pores, while the pore size increased along with the increase in R. laciniata L. content. In the sensory evaluation tests, Jeung-pyun with 5% R. laciniata L. powder showed the best results. Moreover, the antioxidant activity of Jeung-pyun increased with the addition of R. laciniata L. powder. Based on these results, we conclude that R. laciniata L. has good quality characteristics and antioxidant activity, making it a good ingredient for Jeung-pyun.

• Resources Recycling
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• v.31 no.1
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• pp.29-36
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• 2022

The hydrogen reduction behavior of molybdenum oxides was studied using a horizontal-tube reactor. Reduction was carried out in two stages: MoO₃ → MoO₂ and MoO₂ → Mo. In the first stage, a mixed gas composed of 30 vol% H₂ and 70 vol% Ar was selected for the MoO₃ reduction because of its highly exothermic reaction. The temperature ranged from 550 to 600 ℃, and the residence time ranged from 30 to 150 min. In the second step, pure H₂ gas was used for the MoO₂ reduction, and the temperature and residence time ranges were 700-750 ℃ and 30-150 min, respectively. The hydrogen reduction behavior of molybdenum oxides was found to be somewhat different between the two stages. For the first stage, a temperature dependence of the reaction rate was observed, and the best curve fittings were obtained with a surface reaction control mechanism, despite the presence of intermediate oxides under the conditions of this study. Based on this mechanism, the activation energy and pre-exponential were calculated as 85.0 kJ/mol and 9.18 × 10⁷, respectively. In addition, the pore size within a particle increases with the temperature and residence time. In the second stage, a temperature dependence of the reaction rate was also observed; however, the surface reaction control mechanism fit only the early part, which can be ascribed to the degradation of the oxide crystals by a volume change as the MoO₂ → Mo phase transformation proceeded in the later part.

• Clean Technology
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• v.15 no.4
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• pp.265-272
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• 2009

In this study the experiments on the static adsorption of benzene were carried out using activated carbon made from sewage sludge. The experiment was performed at 303.15 K, 318.15 K and 333.15 K under the pressure up to 7.999kPa. Isothermal adsorption curves were obtained using Langmuir isotherm, Freundlich isotherm and Toth isotherm for comparison. Based on fitting the adsorption quantity of Benzene (q), the isothermal adsorption curves obtained from Langmuir isotherm and Toth isotherm showed the higher accuracy. Although there was little difference in accuracy between result from Langmuir isotherm and that from Toth isotherm, the adsorption quantity of Benzene (q) was expressed in terms of Langmuir isotherm because less parameters were required for Langmuir isotherm than for Toth isotherm. Moreover SEM images of the activated carbon from sewage sludge and the commercial activated carbon were taken to observe the pore size development. The results showed that the perforation development of the commercial activated carbon (DARCO A.C., SPG-100 A.C.) was better than that of activated carbon from sewage sludge. Adsorption quantity of benzene on commercial activated carbon was confirmed to be higher than that on activated carbon from sewage sludge. However the maximum adsorption quantity of benzene on activated carbon from sewage sludge was close to that on SGP-100 A.C. at 303.15K. Therefore, we may conclude that it is feasible to commercialize the process to manufacturing activated carbon from sewage sludge.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.9-15
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• 2023

The cement is a typical CO₂ emission industry. Manufacturing process improvements and increased use of alternative materials are needed to reduce energy consumption and CO₂ emissions. This study confirmed the basic characteristics of cement hydration by sintering CAF at low temperature as a CO₂ adsorbent material. For the hydration product of the synthetic CAF, crystal phase analysis, porosity, and structural images were confirmed, and the compressive strength was measured. The replacement rate of SCAF was 10, 20, and 100 %, and the compressive strength tended to decrease as the replacement rate increased. In addition, when the SCAF substitution rate is 100 %, the hydration products of the early age are calcium aluminum oxide hydrate (Ca₃Al₂O₆ x H₂O) and calcium iron hydroxide (Ca₃Fe(OH)₁₂), and at substitution rates of 10 and 20 %, CAF compounds other than general cement hydrates brownmillerite was observed. As for the porosity, the pore size increased and the porosity increased with the increase of the replacement ratio. As a result of this study, CAF manufactured by low-temperature sintering seems to be difficult to use alone and general curing for utilization as a CO₂ adsorbing material.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.221-232
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• 2023

Carbon neutrality requires carbon dioxide reduction technology and alternative green energy sources. Palygorskite is a clay mineral with a ribbon structure and possess a large surface area due to the nanoscale pore size. The clay mineral has been proposed as a potential material to capture carbon dioxide (CO₂) and possibly to store eco-friendly hydrogen gas (H2). We report our preliminary results of grand canonical Monte Carlo (GCMC) simulations that investigated the adsorption isotherms and mechanisms of CO₂ and H₂ into palygorskite nanopores at room temperature. As the chemical potential of gas increased, the adsorbed amount of CO₂ or H₂ within the palygorskite nanopores increased. Compared to CO₂, injection of H₂ into palygorskite required higher energy. The mean squared displacement within palygorskite nanopores was much higher for H₂ than for CO₂, which is consistent with experiments. Our simulations found that CO₂ molecules were arranged in a row in the nanopores, while H₂ molecules showed highly disordered arrangement. This simulation method is promising for finding Earth materials suitable for CO₂ capture and H₂ storage and also expected to contribute to fundamental understanding of fluid-mineral interactions in the geological underground.

• Parasites, Hosts and Diseases
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• v.34 no.3
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• pp.169-176
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• 1996

A scanning electron microscopic study was performed to observe the surface ultrastructures of the third-stage larvae of Gnathostoma hispidun. The early third-stage larvae (EL3) were collected from the viscera of Chinese loaches by the artificial digestion method . The advanced third-stage larvae (AdL3) were recovered from mice experimentally infected with EL3. Both larval worms were fixed with 2.5% glutaraldehyde, dehydrated in graded alcohol. dryad in critical point dryer, and coated with gold. The specimens were observed with a SEM (DS- l30C). On the head bulb of both larval stage, the mouth had a pair of lateral lips of equal size and of half moon shape. Each lip had a couple of labial papillae and a small amphid located between the two papillae. The hooklets on the head bulb had single-pointed tips and curved posteriorly. The cuticular spines of EL3 were larger and more densely distributed in the anterior area (about 1.8 Mm in length) and gradually decreased in size and number posteriorly. The cuticular spines in the anterior area of AdL3 were sharp-pointed and about 4.5 Mm in length, and those in the middle area were about 1.75 Mm. The velvety cuticular folds and dot-like cuticular spines were distributed in the posterior area. A cervical papilla was located between the 7th and 8th transverse striations. A dome-like body papilla was located at the posterior 1/4 of body. An ellipsoidal excretory pore was located between the 17th and 18th striations. From the above results, it is suggested that the characteristic SEM findings obtained from this study may be helpful on the species identification of larval Gncthostomn.