• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.9-14
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• 2022

Silica aerogel is a porous material with a very low density and high specific surface area. Still, its application is limited due to its weak mechanical properties due to structural features. To solve this problem, a method of complexing it with various polymers has been proposed. We synthesized polyimide cross-linked silica aerogel by the sol-gel process to obtain high mechanical properties. Tetraethyl orthosilicate (TEOS) was used as a precursor to make silica aerogel, and 3- aminopropyltriethoxysilane (APTES) was used as a coupling agent for cross-linking polyimide. Polyimide was synthesized using pyromellitic dianhydride and 3,5-diaminobenzoic acid, and mechanical properties were improved by crosslinking polyimide with 10 repeating units in the polyimide chain using the reaction formula ${\frac{n_1}{n_2}}={\frac{n}{n+1}}$ To realize silica aerogel, polyimide having various weight ratios was added before gelation, resulting in a 19-fold or greater increase in maximum compressive strength compared to pure silica aerogel. From this study, an enhancement of silica aerogel could be enhanced through polymer cross-linking bonds.

• Journal of Biomedical Engineering Research
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• v.44 no.6
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• pp.404-413
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• 2023

In this research, we studied the development of a SUS304 microneedle array based on microfabrication technology and the applicability of Parylene-C thin film, a medical polymer material. First of all, four materials commonly used in the field of medical engineering (SUS304, Ti, PMMA, and PEEK) were selected and a 5 ㎛ Parylene-C thin film was deposited. The applicability of Parylene-C coating to each material was confirmed through SEM analysis, contact angle measurement, surface roughness(Ra) measurement, and adhesion test according to ASTM standards for each specimen. Parylene-C thin film was deposited based on chemical vapor deposition (CVD), and a 5 ㎛ Parylene-C deposition process was established through trial and error. Through characteristic experiments to confirm the applicability of Parylene-C, SUS304 material, which is the easiest to apply Parylene-C coating without pretreatment was selected to develop a microneedle array based on CNC micromachining technology. The CNC micromachining process was divided into a total of 5 steps, and a microneedle array consisting of 19 needles with an inner diameter of 200 ㎛, an outer diameter of 400 ㎛, and a height of 1.4 mm was designed and manufactured. Finally, a 5 ㎛ Parylene-C coated microneedle array was developed, which presented future research directions in the field of microneedle-based drug delivery systems.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.1-6
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• 2024

As the demand for hydrogen electric vehicles for commercial vehicles increases, the durability of PEMFCs must increase more than five times that of passenger cars, so research and development to improve durability is urgent. When the PEMFC membrane electrode assembly (MEA) undergoes chemical degradation, the MEA thickness decreases and pinholes occur. In this study, changes in the performance and durability of the MEA were measured while increasing the clamping pressure of the unit cell after open circuit voltage (OCV) holding, an accelerated chemical degradation experiment. As the clamping pressure increased, the resistance of the polymer membrane and the membrane/electrode contact resistance decreased, improving the I-V performance and reducing the hydrogen permeability. As the hydrogen permeability decreased, the OCV increased. When the pinhole area was removed and the MEA clamping pressure was increased, the hydrogen permeability decreased sharply, confirming that the local degradation has a large effect on the performance and durability of the entire cell. When the pinhole was removed and re-clamping and OCV holding was evaluated, it was confirmed that the durability improved according to the decrease in membrane resistance and hydrogen permeability.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.7-12
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• 2024

The durability of the catalyst support has a significant effect on the durability of proton exchange membrane fuel cells (PEMFC). The accelerated durability evaluation of the catalyst support is performed at a high voltage (1.0 to 1.5 V), and the catalyst and ionomer binder in the catalyst layer are also deteriorated, hindering the evaluation of the durability of the support. The existing protocol (DOE protocol) was improved to find conditions in which the support, which is a durability evaluation target, deteriorates further. A protocol (MDOE) was developed in which the relative humidity was lowered by 35% and the number of voltage changes was reduced. After repeating the 1.0 ↔ 1.5 V voltage change cycle, the catalyst mass activitiy (MA), electrochemical active area (ECSA), electrical double layer capacity (DLC), Pt dissolution and particle growth were analyzed. Reaching 40% reduction in mass activity, the MDOE protocol took only 500 cycles, reducing the number of voltage changes compared to the DOE method and increasing the degradation of the carbon support by 50% compared to the DOE protocol.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.107-114
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• 2024

In order to produce high-yield pitch-based activated carbon, pitch was synthesized by blending pyrolysis fuel oil (PFO) and coal-tar. Pitch was synthesized by varying the amount of coal-tar from 0~20% compared to PFO and reacting at 380~420 ℃ for 3 h. The synthesized pitch had a softening point between 80 and 260 ℃, and yields ranged from 10 to 40%. At all synthesis temperatures, as the coal-tar blending ratio increased, the yield increased and the softening point decreased. After considering the selected pitches (softening points: 230~260 ℃), pitches containing coal-tar were more volatile at a low boiling point and had a higher residual carbon content. This is a difference in the composition of coal-tar and PFO, and it was con- firmed that coal-tar has a lot of aromatics and PFO has a lot of aliphatics. The selected pitch was heated to 950 ℃ in a tubular reactor and physically activated with steam for 1 hour. Activated carbon containing coal-tar showed higher yield and microporosity compared to only PFO. In this study, the effect of increasing activated carbon yield by blending pitch raw materials was confirmed, and the physical activation characteristics according to the coal-tar mixing ratio were examined.

• Herbal Formula Science
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• v.31 no.4
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• pp.215-230
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• 2023

Objectives : Schisandra chinensis (Turcz.) Baill contains many nutrients and exhibits high physiological functions. It has been shown that Schisandra seed and pamace contains more nutrients than fruits and thus have higher antioxidant efficacy. In this study, seed and pamace of Schisandra chinensis (Turcz.) Baill (SPSC) were treated with hot-melt extrudate (HME) extrusion to produce water-soluble nanoparticles. Methods : SPSC was treated with HME to prepare nanoparticles. In this process, excipients (hydroxypropyl methylcellulose, pullulan, 2-hydroxylpropyl-beta-cyclodextrin, lecithin) were added to prepare a hydrophilic polymer matrix. To compare and analyze the antioxidant effect and schizandrin content, total flavonoid content, total phenol content and ABTS assay were measured. To confirm the effect of increasing the water solubility of the particles, particle size and water solubility index measurements were performed. The molecular of the material was analyzed using Fourier transform infrared spectroscopy (FT-IR). Results : The particle size of HME extrudates decreased, while total phenols, flavonoids, schizandrin, antioxidant effect, and solubility increased. Through FT-IR, it was confirmed that the SPSC and the extrudate exhibit the same chemical properties. In addition, it was confirmed that when extracted with water, it exhibited a higher antioxidant effect than the ethanol extract. Conclusions : HME technology increased the solubility of SPSC, which are processing by-products, and improved their antioxidant effect to a higher degree. It was confirmed that SPSC could be used as an eco-friendly, high value-added material.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.1
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• pp.11-18
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• 2024

Recently, there have been attempts to claim the hair moisturizing effect for a hair care product, however there has not yet been an official evaluation method because heating temperature for hair has not been established. This study was conducted to establish a quantitative evaluation for hair water content. In order to observe the behavior of water inside hair, heat was applied to hair with various temperatures using thermogravimetric dry residue. As the heating temperature increased, the amount of moisture released from the hair increased. As a result of evaluating hair using a differential scanning calorimeter (DSC), a unique phenomenon in which a rapid endothermic reaction occurs around 75 ℃ was observed. This phenomenon was also observed in different ethnic hair. In hair that damaged the hair cuticle barrier with oxidation and heat, this rapidly rising endothermic reaction temperature occurred at 77 ℃, which was slightly higher, and 73 ℃ was observed when this hair was applied with polar oil, conditioning polymer, or keratin protein. To determine how this reaction affects the hair surface, friction test was performed using an atomic force microscope. When heated above 75 ℃, cuticle friction increased, however when heated above 90 ℃, there was no change in hair cuticle friction. Finally, it was confirmed that around 75 ℃ is the critical temperature at which desorption of water bound to the hair occurs. It is suggested that a heating temperature of 75 ℃ is the optimal temperature for detecting and quantifying the moisture content of hair, and that approximately 10% detected at 75 ℃ can be a standard value for hair moisture content.

• Industry Promotion Research
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• v.9 no.1
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• pp.21-29
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• 2024

In the rapidly advancing information society, electronic devices, including smartphones and tablets, are increasingly digitized and equipped with high-performance features such as flexible displays. This study focused on optimizing the manufacturing process for Transparent Conductive Films (TCF) by using the cost-effective conductive polymer PEDOT and transparent substrate PET as alternatives to expensive materials in flexible display technology. The variables considered are production speed (m/min), coating maximum temperature (℃), and PEDOT supply speed (rpm), with surface resistivity (Ω/□) as the response parameter, using Response Surface Methodology (RSM). Optimization results indicate the ideal conditions for production: a speed of 22.16 m/min, coating temperature of 125.28℃, and PEDOT supply at 522.79 rpm. Statistical analysis validates the reliability of the results (F value: 18.37, P-value: < 0.0001, R²: 0.9430). Under optimal conditions, the predicted surface resistivity is 145.75 Ω/□, closely aligned with the experimental value of 142.97 Ω/□. Applying these findings to mass production processes is expected to enhance production yields and decrease defect rates compared to current practices. This research provides valuable insights for the advancement of flexible display manufacturing.

• Industry Promotion Research
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• v.9 no.1
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• pp.31-38
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• 2024

In this study, evaluated the properties of layered silicate-based nanocomposite sensitive film. For the fabrication of nanocomposite materials, we selected organically modified layered silicate materials, specifically Cloisite^® and Bentone^®, which were treated with quaternary ammonium salts. The impedance of the humidity sensors containing organically modified montmorillonite/hectorite clay decreased with increasing relative humidity(RH%). In the case of the Cloisite^® humidity sensor exhibited slightly better impedance linearity and hysteresis compared to the Bentone^® 38 humidity sensor. Additionally the impedance of the sensor with Bentone^® 38 addition was the lowest when compared to the Cloisite^®-modified sensor. Comparing the Cloisite^®-modified sensors individually, we observed different moisture absorption characteristics based on the hydrophilic properties of the organic-treated materials. The response speed of Cloisite^® 93A tended to be slower due to differences in moisture evaporation rates influenced by the hydrophilic organic components. Based on these results, moisture barriers utilizing organically modified layered silicate materials may exhibit slightly lower moisture absorption properties compared to conventional polymer-based moisture barriers. However, their excellent stability, simple processing, and cost-effectiveness make them suitable for humidity sensor applications.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.32-39
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• 2024

The key components of a Phosphoric acid fuel cell (PAFC) are an electrode catalyst, an electrolyte matrix and a gas diffusion layer (GDL). In this study, we introduced a microporous layer on the GDL of PAFC to enhance liquid electrolyte management and overall electrochemical performance of PAFC. MPL is primarily used in polymer electrolyte membrane fuel cells to serve as an intermediate buffer layer, effectively managing water within the electrode and reducing contact resistance. In this study, electrodes were fabricated using GDLs with and without MPL to examine the influence of MPL on the performance of PAFC. Internal resistance and polarization curves of the unit cell were measured and compared to each other to assess the impact of MPL on PAFC electrode performance. As the results, the application of MPL improved power density from 170.2 to 192.1 mW/cm². MPL effectively managed electrolyte and water within the matrix and electrode, enhancing stability. Furthermore, the application of MPL reduced internal resistance in the electrode, resulting in sustained and stable performance even during long-term operation.