• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.66-72
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• 2009

The detection methods are required to monitor and diagnose the abnormality on the insulation condition inside a gas-insulated switchgear (GIS). Due to a good sensitivity to the products decomposed by partial discharges (PDs) in $SF_6$ gas, the development of a SWNT gas sensor is actively in progress. However, a few numerical studies on the diffusion mechanism of the $SF_6$ decomposition products by PD have been reported. In this study, we modeled $SF_6$ decomposition process in a chamber by calculating temperature, pressure and concentration of the decomposition products by using a commercial CFD program in conjunction with experimental data. It was assumed that the mass production rate and the generation temperature of the decomposition products were $5.04{\times}10^{-10}$ [g/s] and over 773 K respectively. To calculate the concentration equation, the Schmidt number was specified to get the diffusion coefficient functioned by viscosity and density of $SF_6$ gas instead rather than setting it directly. The results showed that the drive potential is governed mainly by the gradient of the decomposition concentration. A lower concentration of the decomposition products was observed as the sensors were placed more away from the discharge region. Also, the concentration increased by increasing the discharge time. By installing multiple sensors the location of PD is expected to be identified by monitoring the response time of the sensors, and the information should be very useful for the diagnosis and maintenance of GIS.

• Membrane Journal
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• v.33 no.4
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• pp.149-157
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• 2023

Covalent organic frameworks (COFs) have shown promise in various applications, including molecular separation, dye separation, gas separation, filtration, and desalination. Integrating COFs into membranes enhances permeability, selectivity, and stability, improving separation processes. Combining COFs with single-walled carbon nanotubes (SWCNT) creates nanocomposite membranes with high permeability and stability, ideal for dye separation. Incorporating COFs into polyamide (PA) membranes improves permeability and selectivity through a synthetic interfacial strategy. Three-dimensional COF fillers in mixed-matrix membranes (MMMs) enhance CO₂/CH₄ separation, making them suitable for biogas upgrading. All-nanoporous composite (ANC) membranes, which combine COFs and metal-organic framework (MOF) membranes, overcome permeance-selectivity trade-offs, significantly improving gas permeance. Computational simulations using hypothetical COFs (hypoCOFs) demonstrate superior CO₂ selectivity and working capacity relevant for CO₂ separation and H₂ purification. COFs integrated into thin-film composite (TFC) and polysulfonamide (PSA) membranes enhance rejection performance for organic contaminants, salt contaminants, and heavy metal ions, improving separation capabilities. TpPa-SO₃H/PAN covalent organic framework membranes (COFMs) exhibited superior desalination performance compared to traditional polyamide membranes by utilizing charged groups to enable efficient desalination through electrostatic repulsion, suggesting their potential for ionic and molecular separations. These findings highlight COFs' potential in membrane technology for enhanced separation processes by improving permeability, selectivity, and stability. In this review, COF applied for the separation process is discussed.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.623-627
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• 2010

Semiconducting metal oxides have been frequently used as gas sensing materials. While zinc oxide is a popular material for such applications, structures such as nanowires, nanorods and nanotubes, due to their large surface area, are natural candidates for use as gas sensors of higher sensitivity. The compound ZnO has been studied, due to its chemical and thermal stability, for use as an n-type semiconducting gas sensor. ZnO has a large exciton binding energy and a large bandgap energy at room temperature. Also, ZnO is sensitive to toxic and combustible gases. The NO gas properties of zinc oxide-single wall carbon nanotube (ZnO-SWCNT) composites were investigated. Fabrication includes the deposition of porous SWCNTs on thermally oxidized $SiO_2$ substrates followed by sputter deposition of Zn and thermal oxidation at $400^{\circ}C$ in oxygen. The Zn films were controlled to 50 nm thicknesses. The effects of microstructure and gas sensing properties were studied for process optimization through comparison of ZnO-SWCNT composites with ZnO film. The basic sensor response behavior to 10 ppm NO gas were checked at different operation temperatures in the range of $150-300^{\circ}C$. The highest sensor responses were observed at $300^{\circ}C$ in ZnO film and $250^{\circ}C$ in ZnO-SWCNT composites. The ZnO-SWCNT composite sensor showed a sensor response (~1300%) five times higher than that of pure ZnO thin film sensors at an operation temperature of $250^{\circ}C$.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.1
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• pp.37-44
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• 2015

In this paper, we have investigated a selective assembly method of single-walled carbon nanotubes (SWCNTs) on a silicon substrate using only photolithographic process and then proposed a fabrication method of field effect transistors (FETs) using SWCNT-based patterns. The aminopropylethoxysilane (APTES) patterns, which are formed for positively charged surface molecular patterns, are utilized to assemble and align millions of SWCNTs and we can more effectively assemble on a silicon (Si) surface using this method than assembly processes using only the 1-octadecyltrichlorosilane (OTS). We investigated a selective assembly method of SWCNTs on a Si surface using surface-programmed APTES and OTS patterns and then a fabrication method of FETs. photoresist(PR) patterns were made using photolithographic process on the silicon dioxide (SiO2) grown Si substrate and the substrate was placed in the OTS solution (1:500 v/v in anhydrous hexane) to cover the bare SiO2 regions. After removing the PR, the substrate was placed in APTES solution to backfill the remaining SiO2 area. This surface-programmed substrate was placed into a SWCNT solution dispersed in dichlorobenzene. SWCNTs were attracted toward the positively charged molecular regions, and aligned along the APTES patterns. On the contrary, SWCNT were not assembled on the OTS patterns. In this process, positively charged surface molecular patterns are utilized to direct the assembly of negatively charged SWCNT on SiO2. As a result, the selectively assembled SWCNT channels can be obtained between two electrodes(source and drain electrodes). Finally, we can successfully fabricate SWCNT-based multi-channel FETs by using our self-assembled monolayer method.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.238-245
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• 2024

The lactate electrode can be utilized either as an electrode for lactate sensor to monitor the patient's health status, stress level, and athlete's fatigue in real time or lactate fuel cell. In this study, we fabricated a high-performance electrode composed of lactate oxidase, catalase, and mitochondria, and investigated the surface analysis and electrochemical properties of this electrode. Carbon paper modified with single-walled carbon nanotubes (CP-SWCNT) had significantly improved electrical conductivity compared to before modification. The electrode to which lactate oxidase, catalase, and mitochondria were attached (CP-SWCNT-LOx-Cat-Mito) produced a higher current than the electrode to which lactate oxidase and catalase were attached. The amount of reduction current produced by the bilirubin oxidase (BOD)-attached electrode (CP-SWCNT-BOD) was greatly affected by the presence or absence of oxygen in the electrolyte. The fuel cell composed of CP-SWCNT-LOx-Cat-Mito (anode) and CP-SWCNT-BOD (cathode) produced maximum power (29 ㎼/cm²) at a discharge current density of 133 ㎂/cm². From this study, we had proved that mitochondria is essential for improving lactate sensor and fuel cell performance.

• Science of Emotion and Sensibility
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• v.24 no.2
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• pp.65-74
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• 2021

With recent innovations in the ICT industry, the demand for wearable sensing devices to recognize and respond to biological signals has increased. In this study, a three-dimensional (3D) spacer fabric was embedded in a single-wall carbon nanotube (SWCNT) dispersive solution through a simple penetration process to develop a monolayer piezoresistive pressure sensor. To induce electrical conductivity in the 3D spacer fabric, samples were immersed in the SWCNT dispersive solution and dried. To determine the electrical properties of the impregnated specimen, a universal testing machine and multimeter were used to measure the resistance of the pressure change. Moreover, to examine the changes in the electrical properties of the sensor, its performance was evaluated by varying the concentration, number of penetrations, and thickness of the specimen. Samples that penetrated twice in the SWCNT distributed solution of 0.1 wt% showed the best performance as sensors. The 7-mm thick sensors showed the highest GF, and the 13-mm thick sensors showed the widest operating range. This study confirms the effectiveness of the simple process of fabricating smart textile sensors comprising 3D spacer fabrics and the excellent performance of the sensors.

• Science of Emotion and Sensibility
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• v.25 no.1
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• pp.67-78
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• 2022

Interest in bio-signal monitoring of wearable devices is increasing significantly as the next generation needs to develop new devices to dominate the global market of the information and communication technology industry. Accordingly, this research developed a resistive textile strain sensor through a wetting process in a single-wall carbon nanotube dispersion solution using an E-Band with low hysteresis. To measure the resistance signal in the E-Band to which electrical conductivity is applied, a universal material tester, an Arduino, and LCR meters that are microcontroller units were used to measure the resistance change according to the tensile change. To effectively handle various noises generated due to the characteristics of the fabric textile strain sensor, the filter performance of the sensor was evaluated using the moving average filter, Savitsky-Golay filter, and intermediate filters of signal processing. As a result, the reliability of the filtering result of the moving average filter was at least 89.82% with a maximum of 97.87%, and moving average filtering was suitable as the noise filtering method of the textile strain sensor.