• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.382-387
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• 2013

Biodegradable polyurethane (PU)/clay nanocomposite films were prepared via extrusion compounding process followed by casting film process. Organically modified montmorillonite (denoted as C30B) with a large amount of hydroxyl groups on its surface was used for the formation of strong bonding with PU resin. From both XRD analysis and TEM observations, the intercalated and exfoliated structure, and dispersion state of silicate platelets in the compounded nanocomposite films were confirmed. In addition, the rheological and tensile properties, optical transparency, oxygen permeability of the prepared nanocomposites were investigated as a function of added nanoclay content, and moreover based on these results, the corelation between the morphology and the resulting properties of the nanocomposites could be presented. The inclusion of nanoclays at appropriate content resulted in remarkable improvement in the nanocomposite performance including tensile modulus, elongation, transparency, and oxygen barrier property, however at excess amount of nanoclays, reduction or very slight increase was observed due to poor dispersion. The biodegradability of the prepared nanocomposite film was evaluated by examining the deterioration in the barrier and tensile properties during degradation period under compost.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.53-59
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• 2009

Low pressure mercury lamp type UV equipments have been widely used for cleaning and modification of PCB surfaces. To enhance the productivity of the process, we newly developed remote DBD type atmospheric pressure plasma equipment. The productivity of both equipments could be compared by measuring surface contact angle for various transferring speed. By the result of the measurement, we could verify that the productivity of the atmospheric pressure plasma be superior to the productivity of the UV equipment. XPS experiments confirmed that the surface effect of the UV and atmospheric pressure plasma processing are similar for each other. Organic contamination level was reduced after the processing and some surface elements were oxidized for both cases. Finally, the atmospheric pressure plasma equipment was adapted to flip chip BGA's flux printing process and it was concluded that the printing uniformity be enhanced by the atmospheric pressure plasma surface treatment.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.155-181
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• 2024

In recent years, significant research has been conducted to enhance the performance of existing membranes for efficient CO₂ capture, aiming to expand their application in carbon capture processes. Membrane technology has emerged as a promising carbon capture approach to addressing the net-zero challenge due to its cost and energy efficiency, continuous operation, and compact process size. Among the various types of membranes studied, mixed-matrix membranes (MMMs) have been proposed as an alternative to conventional membranes to enhance the efficiency of gas separation processes. Various common 2D nanomaterials, characterized by their ease of modification, functionalization, and compatibility with other materials, have been used to create efficient MMMs for gas separation. This article comprehensively reviews the recent developments in MMMs using 2D nanomaterials. It also discusses the current challenges and prospects of 2D nanomaterial-based membranes for CO₂ separation and capture.

• Membrane Journal
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• v.18 no.3
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• pp.206-213
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• 2008

Poly(vinylidene fluoride) (PVDF) membrane surfaces were modified using surface modifying macromolecules (SMMs). The Zonyl BA-L as SMM was used and the various PVDF membranes containing 0 to 2 wt% SMM were prepared. The resulting membranes were characterized through SEM, contact angle measurements and pervaporation separation of water-ethanol system. SMM layers were created in the surface regions of PVDF membranes by SEM images and the contact angles were increased more than untreated PVDF membranes. The pervaporation was carried out at 50, 60 and $70^{\circ}C$, and the PVDF membranes containing 1 and 2 wt% SMM were used for 10, 20, 50 wt% water in the binary water/ethanol mixtures and pure water. PVDF/2 wt% Zrlnyl BA-L membrane showed the permeability 5.3 $g/m^2hr$ and separation factor 287 at $50^{\circ}C$ for water : ethanol = 10 : 50 solution.

• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.45-50
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• 2015

In the present work, to increase the chemical stability of the lithium-ion-conducting ceramic electrolyte ($Li_{1+x+y}Al_xTi_{2-x}Si_yP_{3-y}O_{12}$, LATP) in the strong alkaline solution, the surface of LATP was modified by the nitridation process. The surface and structural properties of nitride LATP solid electrolyte were characterized by X-ray diffraction, X-ray photoelectron spectrometer and scanning electron microscopy and ac-impedance spectroscopy, which were correlated to the chemical stability and electrochemical performance of LATP. The nitrided LATP immersed in the alkaline solution for 30 days exhibits the enhanced chemical stability than the pristine LATP. Moreover, a rechargeable hybrid Li-air battery constructed with the nitrided LATP solid electrolyte shows considerably reduced discharge-charge voltage gaps (enhanced the round-trip efficiency) in comparison to the cell constructed with pristine LATP, which indicate that the surface nitridation process can be the efficient way to improve the chemical stability of solid electrolyte in alkaline media.

• Journal of Sericultural and Entomological Science
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• v.29 no.2
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• pp.73-81
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• 1987

This investigation was carried cut to obtain the reeling water conditions in Korea. The analyzed items of water were pH, colority, turbidity, acidity, alkalinity, solids electric conductibity hardness and heavy metal ions. About 40% of the reeling water were found to be agreeable, 30% were acceptable provided with some quality control and the others were out of acceptable range mainly based on the M-alkalinity, acidity, pH and total hardness. It was found that there was a following relationship between total hardness and electric conductibity with the relative correlation coefficient r=0.9145. y=15.967+0.22774x Where x, y are electric conductivity and total hardness respectively.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.231-237
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• 2014

The supercritical fluids (SCFs) have been widely used for material synthesis and processing due to their remarkable properties including low viscosity, high diffusivity and low surface tension. Carbon dioxide is one of the suitable solvents in SCFs processes in terms of its advantages such as easy processibility (with low critical temperature and pressure), inexpensive, nonflammable, nontoxic, and readily available. However, it has generally low solubility for high molecular weight polymers with the exception of fluoropolymers and siloxane polymers. Therefore, hydrocarbon solvents and hydrochlorofluorocarbons have been used for various SCFs process by its high solubility for high molecular weight polymers. In this report, a PMMA/clay nanocomposites were fabricated by using supercritical fluid process. The $Na^+$-MMT(montmorillonites)was modified by a fluorinated surfactant which is able to enhance compatibility with the chlorodifluoromethane(HCFC-22) and thus, improve dispersability of the clay in the polymer matrix. The PMMA/fluorinated surfactant modified clay nanocomposite shows enhanced mechanical and thermal properties which characterized by X-raydiffraction(XRD), Thermo gravimetric analysis(TGA), Dynamic mechanical analysis (DMA) and Transmission electron microscopy (TEM).

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.176-182
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• 2012

The methane dry reforming has received the considerable attention in recent years, mainly as an attractive route to produce synthesis gas (CO, $H_2$) from green-house gases ($CH_4$, $CO_2$) for resources. However, this process has not been commercialized due to the high temperature and catalyst deactivation. In this study, Co-Ru-Zr catalysts supported on $SiO_2$ were studied for the characterization of methane dry reforming reaction and the preliminary data for process development were achieved. The crystal structure of catalysts was measured by XRD, the surface area and pore size were analyzed by BET, and the element composition of catalyst were analyzed by EDS. Conversions of methane and carbon dioxide were analyzed by GC. In addition, reaction rate constants were obtained from the reaction kinetic study and the optimum catalyst size that does not affect mass transfer from reactants was also determined. The selected pellet-type catalyst maintained activation for 720 h at $850^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.17-24
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• 2021

The development of a new sorbent for carbon dioxide depends on several factors, such as fast adsorption/absorption velocity, hydrophobicity, and lower regeneration temperature than commercial sorbent. In this study, aminosilane grafted activated carbon was synthesized to capture CO2. Methyltrimethoxysilane (MTMS) and 3-aminopropyl-triethoxysilane (APTES) were used as the grafting precursor of the amine functional group. The APTES grafting activated carbon showed higher sorption property than MTMS used one. The characteristics of the separation mechanism of carbon dioxide were examined by measuring the adsorption capacity according to temperature and carbon dioxide partial pressure. The absorption capacity of carbon dioxide was similar to amine grafting activated carbon and activated carbon at 25℃, but amine-grafted activated carbon was higher at 75℃. The amine functional group-grafted activated carbon showed higher absorption capacity than activated carbon with a 1% carbon dioxide partial pressure. Aminosilane grafting of activated carbon was chemically absorbed but also showed the characteristics of physical adsorption. The reforming activated carbon with an amine functional group grafted solid absorption/adsorption sorbent would significantly impact the material engineering industry and carbon dioxide adsorption process. The functionalized sorbent is a high-performance composite material. The developed sorbent may have applications in other industrial processes of absorption/adsorption and separation.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.537-542
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• 2016

In this study, we have prepared mesophase pitch from pyrolysis fuel oil (PFO) by heterogeneous reforming process. This process was conducted by direct fluorination at various temperature and followed by the heat treatment at $390^{\circ}C$. The reformed pitch was then investigated by softening point analysis, elemental analysis, fourier-transform infrared spectroscopy, high resolution X-ray diffraction and polarization microscope analysis. Carbon contents of reformed pitch increased according to increasing the reaction temperature of fluorination, while oxygen, nitrogen and sulfur contents were completely eliminated. As the fluorination temperature increased, the creation, growth, coalescence and alignment process of mesophase spheres were observed. Also the interlayer spacing of carbon hexagonal planar structure decreased, while its crystalline size increased. In addition, aromatic ring compound contents increased by the condensation polymerization of aliphatic compound. These results can be attributed to the radical reactivity of the fluorine increased as the reaction temperature increased. It was considered that the fluorination reaction could help PFO to generate aromatic compounds, via promoting polymerization by radical reaction.