• Korean Journal of Materials Research
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• v.32 no.12
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• pp.545-552
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• 2022

Tin-antimony sulfide nanocomposites were prepared via hydrothermal synthesis and a N₂ reduction process for use as a negative electrode in a sodium ion battery. The electrochemical energy storage performance of the battery was analyzed according to the tin-antimony composition. The optimized sulfides exhibited superior charge/discharge capacity (770 mAh g^-1 at a current density of 100 mA g^-1) and stable lifespan characteristics (71.2 % after 200 cycles at a current density of 500 mA g^-1). It exhibited a reversible characteristic, continuously participating in the charge-discharge process. The improved electrochemical energy storage performance and cycle stability was attributed to the small particle size, by controlling the composition of the tin-antimony sulfide. By optimizing the tin-antimony ratio during the synthesis process, it did not deviate from the solubility limit. Graphene oxide also acts to suppress volume expansion during reversible electrochemical reaction. Based on these results, tin-antimony sulfide is considered a promising anode material for a sodium ion battery used as a medium-to-large energy storage source.

• Journal of Powder Materials
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• v.30 no.2
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• pp.107-115
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• 2023

Li_1.3Al_0.3Ti_1.7(PO₄)₃(LATP) is considered a promising material for all-solid-state lithium batteries owing to its high moisture stability, wide potential window (~6 V), and relatively high ion conductivity (10^-3-10^-4 S/cm). Solid electrolytes based on LATP are manufactured via sintering, using LATP powder as the starting material. The properties of the starting materials depend on the synthesis conditions, which affect the microstructure and ionic conductivity of the solid electrolytes. In this study, we synthesize the LATP powder using sol-gel and co-precipitation methods and characterize the physical properties of powder, such as size, shape, and crystallinity. In addition, we have prepared a disc-shaped LATP solid electrolyte using LATP powder as the starting material. In addition, X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopic measurements are conducted to analyze the grain size, microstructures, and ion conduction properties. These results indicate that the synthesis conditions of the powder are a crucial factor in creating microstructures and affecting the conduction properties of lithium ions in solid electrolytes.

• Composites Research
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• v.21 no.3
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• pp.24-30
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• 2008

Durability problems may arise in the concrete, which is one of the major construction materials, used in the construction field. Bridge piers and foundation piles are usually made with concrete and they are exposed to the moisture and hence the durability of the concrete reduced significantly due to oxidization of re-bar and icing of concrete. To mitigate such problems, FRP tube has been developed and the concrete filled FRP tube (CFFT) has been investigated to find the confinement effect which is provided additionally. It was reported that if the concrete is wrapped with FRP, strength and chemical resistance are improved significantly. In order to apply such a member in the construction field, structural behavior and applicable design guideline or design criteria must be thoroughly investigated. In the experimental investigation, the results are compared with the previous research results and the relationship which can predict the ultimate strength and strain is suggested. In addition, some comments found at the compression tests are given briefly.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.1
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• pp.36-43
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• 2023

To establish a culture system with enhanced cellular nutrition, we investigated the effects of light quality (blue, 450 nm; yellow, 590 nm; and red, 630 nm) of a light-emitting diode (LED) on the biochemical composition of Tetraselmis suecica and T. tetrathele. The protein content of both species was higher (42-69%) than the content of other biochemical substances under all wavelengths. Carbohydrate, protein, and lipid contents were higher under the yellow wavelength, which showed a low growth rate, than those under other wavelengths. The contents of all biochemical substances were low under the red wavelength, which showed a high growth rate. These results indicated that protein synthesis occurs in response to decreased cell division rate, while lipid and carbohydrate synthesis occurs owing to altered chemical composition and enzymatic activity. Therefore, we suggested a two-phase LED culture system, which emitted red LED during the early-middle exponential phase and yellow LED during the late exponential and stationary phases, to increase the yield of useful biochemical substances of T. suecica and T. tetrathele.

• Journal of the Korean institute of surface engineering
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• v.56 no.3
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• pp.208-218
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• 2023

Photocatalysts are advanced materials which accelerate the photoreaction by providing ordinary reactions with other pathways. The catalysts have various advantages, such as low-cost, low operating temperature and pressure, and long-term use. They are applied to environmental and energy field, including the air and water purification, water splitting for hydrogen production, sterilization and self-cleaning surfaces. However, commercial photocatalysts only absorb ultraviolet light between 100 and 400 nm of wavelength which comprises only 5% in sunlight due to the wide band gap. In addition, rapid recombination of electron-hole pairs reduces the photocatalytic performance. Recently, studies on blackening photocatalysts by laser, thermal, and plasma treatments have been conducted to enhance the absorption of visible light and photocatalytic activity. The disordered structures could yield mid-gap states and vacancies could cause charge carrier trapping. Herein, liquid phase plasma (LPP) is adopted to synthesize Ag-doped black ZnO for the utilization of visible-light. The physical and chemical characteristics of the synthesized photocatalysts are analyzed by SEM/EDS, XRD, XPS and the optical properties of them are investigated using UV/Vis DRS and PL analyses. Lastly, the photocatalytic activity was evaluated using methylene blue as a pollutant.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.439-445
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• 2023

In this study, silver nanoparticles were synthesized by reducing silver nitrate with PVA, and the solution prepared by adding carboxymethyl cellulose (CMC) to the silver nanoparticles was coated on a PET substrate to prepare a coating film with antibacterial and antifogging function. When the coating films were in contact with water vapor at 80 ℃, the uncoated PET substrate was blurred due to the scattering of light due to the occurrence of fog, while the coating film coated with silver nanosol with CMC remained transparent despite contact with water vapor, showing excellent antifogging function. In addition, the antibacterial properties of the coating films were measured by film adhesion method for Staphylococcus aureus, gram-positive bacteria, and Escherichia coli, gram-negative bacteria. The uncoated PET substrate showed a large number of colonies of Staphylococcus aureus and Escherichia coli, while the coating film coated with the silver nanosol greatly inhibited the growth of Staphylococcus aureus and Escherichia coli, resulting in excellent antibacterial effect.

• Composites Research
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• v.36 no.2
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• pp.101-107
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• 2023

In this study, aluminum nitride (AlN) reinforced aluminum (Al) matrix composites are fabricated via plasma arc melting under a nitrogen atmosphere. Within a minute of the chemical reaction between Al and N, dispersed AlN with the shape of transient and lamellar layers is in situ formed in the Al matrix. The composite contains 10 vol.% AlN reinforcements with low thermal resistance and strong bonding at the interfaces, which leads to the unique combination of thermal expansivity and conductivity in the resulting composites. The coefficient of thermal expansion of the composite can be further reduced when Si was alloyed into the Al matrix, which proposes the potential of the in situ Al matrix composites for thermal management applications.

• Analytical Science and Technology
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• v.19 no.6
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• pp.519-528
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• 2006

An analytical method for the determination of thyroid hormones in urine samples has been studied by using solid-phase extraction and high-performance liquid chromatography/diode array detector/electro-spray mass spectrometry. Seven thyroid hormones were successfully separated by gradient elution on the reverse phase Hypersil ODS column (4.6 mm I.D., 100 mm length, particle size $5{\mu}m$) with ammonium formate buffer and acetonitrile, and UV spectra and mass fragment could be confirmed. The extraction recoveries of thyroid hormones in the urine samples (pH 3) were in the range of 89.0-113.1% with solid-phase extraction by C18, followed by elution with 4 ml of methanol/ammonium hydroxide (9 : 1). The calibration curves showed good linearity with the correlation coefficients ($r^2$) varying from 0.992 to 0.998 and the detection limits of all analytes were obtained in the range of 2-4 ng/ml (3.8-13.0 pmol/ml).

• Analytical Science and Technology
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• v.19 no.1
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• pp.50-57
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• 2006

Well known environmental wastes from dye industry were separated by the micellar electrokinetic capillary chromatography(MECC). These wastes include H-acid modifier and 2-naphthylamine-1,5-disulfonic acid, and are known to be the diazo components of the azo dye. The results of the separation were compared with the result obtained by the HPLC using ion-pairing mechnism. MECC method was also applied to separate a few direct dyes including Direct Blue 2, Direct Blue 6 and Direct Blue 15, and reactive dye such as Reactive Orange 4. Informations about the diazo components of any azo dye could be obtained by comparison of electropherogram of the reduction solution of given dye with those obtained from standard materials such as H-acid, J-acid, ${\gamma}$-acid, orthanilic acid, sulfanilic acid and 2-naphthylamine-1,5-disulfonic acid which are used as diazo components of the typical azo dyes. It has been concluded that MECC and HPLC with ion-pairing mechanism could be successfully applied for the analysis of unknown dyes and their diazo components.

• Analytical Science and Technology
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• v.19 no.1
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• pp.31-38
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• 2006

Micellar electrokinetic capillary chromatography(MECC) and HPLC with ion-pairing mechanism were applied for the separation of the well known environmental wastes from dye industry. These compounds include H-acid, J-acid, ${\gamma}$-acid, orthanilic acid, sulfanilic acid and 2-naphthylamine-1,5-disulfonic acid, and are known to be the diazo components of the azo dye. MECC method was also applied to separate few acid dyes including Acid Orange 7, Acid Orange 5 and Acid Blue 92 and direct dye such as Direct Red 80. Informations about the diazo components of any azo dye could be obtained by comparison of electropherogram of the reduction solution of a given dye with those obtained from standard materials such as H-acid, J-acid, ${\gamma}$-acid, orthanilic acid, sulfanilic acid and 2-naphthylamine-1,5-disulfonic acid. It has been concluded that MECC and HPLC with ion-pairing mechanism could be successfully applied for the analysis of unknown dyes and their diazo components.