• Membrane Journal
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• v.31 no.3
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• pp.200-211
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• 2021

In this study, mixed matrix membranes were prepared by mixing the synthesized zeolitic imidazolate framework-7 (ZIF-7) with poly(ether-b-amide) 2533 (PEBAX2533). A single gas (N₂, CO₂) was permeated through the membrane to investigate the properties of the gas. Through FT-IR, XRD, and FE-SEM, the peaks and shapes of ZIF-7 were confirmed, and it was determined that the synthesis was successful. Through TGA, it was confirmed that ZIF-7 has excellent thermal stability and that when incorporated into the membrane, the thermal stability is improved compared to pure PEBAX2533. It was found that ZIF-7 synthesized through BET had excellent CO₂ adsorption capacity and CO₂/N₂ adsorption selectivity showed a high value of about 49.64. For the gas permeation, as the ZIF-7 content in the mixed membrane increases, the N₂ permeability decreases and the CO₂ permeability slightly decreases, while the CO₂/N₂ selectivity steadily increases. In particular, when 20 wt% of ZIF-7 was added, the CO₂ permeability did not decrease significantly and the CO₂/N₂ selectivity increased considerably, resulting in the performance approaching to the Robeson upper-bound.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.373-380
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• 2023

This study investigated the carbonation of concrete brick cured in a CO₂ environment for the utilization of CO₂ captured in power plants. Concrete brick specimens were produced with electric arc furnace reducing slag (ERS) and electric arc furnace oxidizing slag (EOS), and cured for 3 days in a CO₂ chamber with a concentration of 20 % or in a constant temperature and humidity chamber. The weight change, compressive strength, flexural strength and carbonation depth of concrete bricks were measured. From the results, it was found that when subjected to CO₂ curing, CO₂ was absorbed at the level of 2.4 % of the weight of the specimen. The specimen incorporating ERS showed the highest carbonation depth, and satisfied KS F4004 standards for the concrete brick. Therefore, it is expected that the captured CO₂ can be utilized in the CO₂ curing process of concrete brick.

• Membrane Journal
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• v.33 no.3
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• pp.94-109
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• 2023

1,3-Dioxolane is an exciting material that has attracted widespread interest in the chemical, paint, and pharmaceutical industries as a solvent, electrolyte, and reagent because 1,3-dioxolane is not toxic, carcinogenic, explosive, auto-flammable, and multifunctional, and due to their excellent miscibility in most organic and aqueous solvent conditions. Recently, this material has received increasing attention as a CO₂-selective polymer precursor to separating CO₂ from flue gas and natural gas mixtures. Poly(1,3-dioxolane) (PDXL) possesses higher ether oxygen content than polyethylene oxide (PEO), which demonstrates superior membrane CO₂/N₂ separation properties owing to their polar ether oxygen groups exhibiting strong affinity toward CO₂. Thus, PDXL-based membranes displayed an outstanding CO₂ solubility selectivity over non-polar (N₂, H₂, and CH₄) gases. However, the polar groups of PDXL, like PEO, promote chain packing efficiency and cause polymer crystallization, thereby reducing its gas permeability, which should be improved. In this short review, we discuss the recent advancement and limitations of PDXL membranes in gas separation applications. To conclude, we provide future perspectives for inhibiting the limits of 1,3-dioxolane-based polymers in the CO₂ separation process.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.269-273
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• 2002

The NASICON solid electrolyte films, $Na_{1+x}Zr_2Si_xP_{3-x}O_{12}$(1.5< x < 2.3), was prepared from ceramic slurry by modified doctor-blade process. The NASICON solid electrolyte and fabricated sensors, Pt-electrode/NASICON/Carbonate$(Na_2CO_3-K_2CO_3CaCO_3\; system)$ electrode, were investigated to measure phase, microstructure and e.m.f variation for sensing $CO_2$ concentration. The uniform grain size of $2-4{\mu}m$ and major phase of sodium zirconium silicon phosphate phase, $Na_{1+x}Zr_2Si_xP_{3-x}O_{12}$was identified with X-ray diffraction patterns and scanning electron microscopy, respectively. The Nernst's slope of 84 mV/decade for $CO_2$ concentration from 500 to 8000 ppm was obtained at operating temperature of $400^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.94-98
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• 2021

In this study, pure and Co3O4/CoFe2O4-loaded Indium oxide (In2O3) nanofibers were synthesized by the electrospinning of an Indium/Polyvinylpyrrolidone precursor solution containing cobalt and iron bimetallic zeolitic imidazolate frameworks and subsequent heat treatment. The ethanol, toluene, p-xylene, benzene, carbon monodxide, and hydrogen gas sensing characteristics of the solution were measured at 250-400 ℃. 0.5 at%-Co3O4/CoFe2O4-loaded In2O3 nanofibers exhibited extreme response (resistance ratio - 1) to 5 ppm of ethanol (210.5) at 250 ℃ and excellent selectivity over the interfering gases. In contrast, pure In2O3 nanofibers exhibited relatively low responses to all the analyte gases and low selectivity above 250-400 ℃. The superior response and selectivity toward ethanol is explained by the catalytic roles of Co3O4 and CoFe2O4 in gas sensing reaction and the electronic sensitization induced by the formation of p (Co3O4/CoFe2O4)-n (In2O3) junctions.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.587-592
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• 2023

Cobalt oxide (Co₃O₄·CoO) ultra fine particles were synthesized by liquid phase precursor method. cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) was as a starting material. A plant-derived crystalline cellulose was used as impregnating materials. A impregnated precursor was calcined at a temperature of 350 to 900℃ to obtain cobalt oxide particles having a particle size of 1 to 10㎛. The crystallization process and morphology according to the calcination temperature were examined, and the properties of the synthesized powder were evaluated using SEM and XRD. It was confirmed that a crystal phase of Co₃O₄ began to form around 350℃ and crystal growth occurred up to 900℃. At a temperature above 500℃, the Co₃O₄ crystal was changed to another crystal phase CoO.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.52-58
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• 2020

Electrochemical characterization and thermal stability were investigated for MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ cathode. The ratio of MgF₂ was controlled by 0.5, 1, 3 wt%. Cyclic voltammetry, charge-discharge profiles, rate capability, cycle life were measured for electrochemical properties. DSC analysis was measured for thermal stability. The first discharge capacities of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were decreased at 0.1C-rate compared to pristine LiNi_0.8Co_0.15Al_0.05O₂. But the rate capability and cycle life of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were improved at 2C-rate. In DSC analysis result, the exothermic temperature of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ was increased and peak height was decreased.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.392-396
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• 2021

Expensive PCBN or ceramic cutting tools are used for processing of difficult-to-cut materials such as Ti and Ni alloy materials. These tools have the problem of breaking easily due to their high hardness but low fracture toughness. To solve these problems, cutting tools that form various coating layers are used in low-cost WC-Co hard material tools, and research on various tool materials is being conducted. In this study, binderless-WC, WC-6 wt%Co, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are densified using horizontal ball milled WC-Co, WC-Co-Mo₂C powders, and spark plasma sintering process (SPS process). Each SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are almost completely dense, with relative density of up to 99.5 % after the simultaneous application of pressure of 60 MPa and almost no significant change in grain size. The average grain sizes of WC for Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are about 0.37, 0.6, 0.54, and 0.43 ㎛, respectively. Mechanical properties, microstructure, and phase analysis of SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are investigated.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.25-31
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• 2023

The purpose of this study is to increase the thermal efficiency of a landfill gas (LFG) power generation engine by capturing carbon dioxide (CO₂) from landfill gas (LFG) using monoethanolamine (MEA), which is widely used in the chemical CO₂ absorption process. Since the use of LFG as an energy source can be a means of reducing greenhouse gas emissions, MEA can be used to reduce CO₂ in LFG and increase the concentration of CH₄ to improve the efficiency of power generation. In this study, experiments were conducted to measure the solubility of CO₂ and CH₄ in MEA solution, increase the solubility under different conditions, and analyse the dissolution characteristics. It was found that the CO₂ absorption rate increased as the ratio of MEA to reaction gas increased. There is an optimum MEA concentration to maximise CO₂ solubility, and even if the concentration is increased above this concentration, the solubility does not improve significantly. This study provided fundamental work to develop a more practical fuel by capturing CO₂ from LFG and increasing the concentration of CH₄ while reducing greenhouse gas emissions.

• Journal of Industrial Technology
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• v.42 no.1
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• pp.1-5
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• 2022

Although the mileage of electric vehicles can be increased based on the excellent energy density of the LiNi_0.9Co_0.05Mn_0.05O₂, it is known that the reason for limiting its use is the low lifespan and poor surface stability due to the structural deformation of the LiNi_0.9Co_0.05Mn_0.05O₂. To improve the structural stability of LiNi_0.9Co_0.05Mn_0.05O₂, electrochemical performance is improved by La coating on the surface. La-modified LiNi_0.9Co_0.05Mn_0.05O₂ shows an initial capacity of 210.6 mAh/g, a capacity retention rate of 89.9 % after 50 cycles, and a retention rate of 52.5% at 6.0 C. These are superior performances than the pristine sample, because the structural stability of the LiNi_0.9Co_0.05Mn_0.05O₂ cathode is improved by the La coating.