• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.306-315
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• 2016

Amorphous vanadium titanates (aVTOs) are examined for use as a negative electrode in lithium-ion batteries. These amorphous mixed oxides are synthesized in nanosized particles (<100 nm) and flocculated to form secondary particles. The $V^{5+}$ ions in aVTO are found to occupy tetrahedral sites, whereas the $Ti^{4+}$ ions show fivefold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural defects. The first reversible capacity of an aVTO electrode ($295mAhg^{-1}$) is larger than that observed for a physically mixed electrode (1:2 $aV_2O_5$ | $aTiO_2$, $245mAhg^{-1}$). The discrepancy seems to be due to the unique four-coordinated $V^{5+}$ ions in aVTO, which either are more electron-accepting or generate more structural defects that serve as $Li^+$ storage sites. Coin-type Li/aVTO cells show a large irreversible capacity in the first cycle. When they are prepared under nitrogen (aVTO-N), the population of surface hydroxyl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and $Li_2O$), leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.1-10
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• 2014

Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted phophomolybdic acid(Cs-MoPA) with cross-linking agent contents of 0.01mL. In conclusion, CL-SPEEK/$Cs_{(2.5)}$-MoPA/ceria(1%) membrane showed the optimum results such as 0.1095S/cm of proton conductivity at $80^{\circ}C$, 2.906meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 49.73MPa of tensile strength which were better than Nafion 117 membrane.

• Elastomers and Composites
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• v.55 no.1
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• pp.26-39
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• 2020

The physical properties of silica-filled SBR compounds (WSBR) prepared using silica-SBR wet masterbatches (WMB) were systematically investigated to understand the effect of the surface treatment of silica on the reinforcement performance of SBR. Treatment of silica with bis(triethoxysilylpropyl)tetrasulfide (TESPT) in the liquid phase, followed by mixing with an SBR solution and recovery by water stripping, easily produced silica-SBR WMB. However, insufficient surface treatment in terms of the amount and stability of the incorporated TESPT led to considerable silica loss and inevitable TESPT elution. Pretreatment of silica in the gas phase with TESPT and another organic material that enabled the formation of organic networks among the silica particles on the surface provided hydrophobated silica, which could be used to produce silica-SBR WMB, in high yields of above 99%. The amount and type of organic material incorporated into silica greatly influenced the cure characteristics, processability, and tensile and dynamic properties of the WSBR compounds. The TESPT and organic material stably incorporated into silica increased their viscosity, while the organic networks dispersed on the silica surface were highly beneficial for reducing their rolling resistance. Excessive dosing of TESTP induced low viscosity and a high modulus. The presence of connection bonds formed by the reaction of glycidyloxy groups with amine groups on the silica surface resulted in physical entanglement of the rubber chains with the bonds in the WSBR compounds, leading to low rolling resistance without sacrificing the mechanical properties. Mixing of the hydrophobated silica with a rubber solution in the liquid phase improved the silica dispersion of WSBR compounds, as confirmed by their low Payne effect, and preservation of the low modulus enhanced the degree of entanglement.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.437-447
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• 2012

Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted tungstophosphoric acid (Cs-TPA) with cross-linking agent contents of 0.01 mL. In conclusion, CL-SPEEK/Cs-TPA/ceria (1%) membrane showed the optimum results such as 0.130 S/cm of proton conductivity at $80^{\circ}C$, 2.324 meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 65.03 MPa of tensile strength which were better than Nafion 117 membrane.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.390-397
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• 2010

0.5wt% Ru/$\alpha-Al_2O_3$ catalysts are prepared by deposition-precipitation method for the preferential CO oxidation In order to investigate the effect of pH on the Ru dispersion and particle size, the pH of precursor solution is adjusted to between 5.5 and 9.5. 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH of 6.5 has high Ru dispersion of 17.9% and small particle size of 7.7nm. In addition, 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH 6.5 is easily reduced at low temperatures below $150^{\circ}C$ due to high dispersion of $RuO_2$ particle and shows high CO conversion over 90% in the wide temperature range between $100^{\circ}C$ and $160^{\circ}C$. Moreover, the deposition-precipitation is a feasible method to improve the Ru dispersion as compared to the impregnation method. The 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared by deposition-precipitation exhibits higher CO conversion than 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts prepared by impregnation due to higher metal dispersion and better reducibility at low temperature.

• Journal of the Optical Society of Korea
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• v.16 no.4
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• pp.331-335
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• 2012

A miniaturized laser beam transmitter, in which a visible laser module at ${\lambda}$=650 nm is precisely stacked upon an infrared (IR) module at ${\lambda}$=905 nm, has been proposed and constructed to provide an IR collimated beam in conjunction with a collinear monitoring visible beam. In particular, the IR beam is selectively dispersed through a perforated sheet diffuser, so as to create a rapidly diverging close-range beam in addition to a highly defined long-range beam simultaneously. The complementary close-range beam plays a role in mitigating the blind region in the vicinity of the transmitter, which is inevitably missed by the main long-range beam, thereby uniformly extending the transmitter's effective trajectory that is sensed by a receiver. The proposed transmitter was designed through numerical simulations and then fabricated by incorporating a diffuser sheet, perforated with an aperture of 2 mm. For the manufactured transmitter, the IR long-range beam was observed to have divergences of ~2.3 and 1.6 mrad in the fast and slow axes, respectively, while the short-range beam yielded a divergence of ~24 mrad. The angular alignment between the long-range IR and visible beams was as accurate as ~0.5 mrad. According to an outdoor feasibility test involving a receiver, the combination of the IR long- and short-range beams was proven to achieve a nearly uniform trajectory over a distance ranging up to ~600 m, with an average detectable cross-section of ${\sim}60{\times}80cm^2$.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.1
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• pp.41-52
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• 2021

NiO and Co3O4-doped porous La(CoNi)O3 perovskite oxides were prepared from excess Ni addition by a hydrothermal method using porous silica template, and characterized as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for Zn-air rechargeable batteries in alkaline solution. Excess Ni induced to form NiO and Co3O4 in La(CoNi)O3 particles. The NiO and Co3O4-doped porous La(CoNi)O3 showed high specific surface area, up to nine times of conventionally synthesized perovskite oxide, and abundant pore volume with similar structure. Extra added Ni was partially substituted for Co as B site of ABO3 perovskite structure and formed to NiO and Co3O4 which was highly dispersed in particles. Excess Ni in La(CoNi)O3 catalysts increased OER performance (259 mA/㎠ at 2.4 V) in alkaline solution, although the activities (211 mA/㎠ at 0.5 V) for ORR were not changed with the content of excess Ni. La(CoNi)O3 with excess Ni showed very stable cyclability and low capacity fading rate (0.38 & 0.07 ㎶/hour for ORR & OER) until 300 hours (~70 cycles) but more excess content of Ni in La(CoNi)O3 gave negative effect to cyclability.

• Korea Journal of Cosmetic Science
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• v.2 no.1
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• pp.21-31
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• 2020

The aim of this study is to develop a sunscreen stick formulation technology with excellent water resistance and washability. Consumers' needs for sunscreen products are diversifying. Water resistance and ease of washing are both important factors in sunscreen products. However, it is difficult to develop a sunscreen formulation that satisfies these two factors at the same time, because these two elements are in conflict. Fatty acid has a hydrophobic property against the water with low or neutral pH, but when it contacts with soapy water which has high pH, saponification occurs and the fatty acids become surfactants and can be dispersed in the water. Using the reaction characteristics of fatty acids, we can make sunscreen that is highly resistant to water or sweat, but is only selectively removed from soapy water. We found that the sunscreen stick containing fatty acids had better water resistance and washability than the sunscreen sticks without fatty acid. The sunscreen stick containing fatty acids showed a tendency to improve water resistance by scattering ultraviolet rays of long wavelength area by forming insoluble precipitation with divalent ions in tap water after immersion. In addition, an increase in the fatty acid content tended to also increase the ease of cleaning the sunscreen stick. Solid fatty acid was advantageous in improving water resistance than liquid fatty acid, but there was no difference between solid fatty acids and liquid fatty acid in washability. When it comes to stability, the sunscreen stick using liquid fatty acids maintained a high hardness and melting point, and showed no sweating. Based on this study, it is possible to develop an easy washable sunscreen stick formulation technology that has excellent water resistance but is selectively removed only in soapy water.

• Journal of the Korean Society of Safety
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• v.38 no.3
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• pp.43-50
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• 2023

Silicone tetrachloride (SiCl₄) leak accidents cause enormous human and environmental damage because it is highly toxic. Some handling facilities use water curtains to reduce the impact range of SiCl₄. Although the water curtain is known as one of the most efficient technologies for post-release mitigation, its effect on reducing SiCl₄ concentration needs to be investigated scientifically and quantitatively. In this study, three-dimensional computational fluid dynamics (CFD) was used to investigate the physical and chemical effects of water curtains as a release-mitigation system for SiCl₄. SiCl₄ is released and dispersed five seconds prior to the operation of the water curtain. Once the water curtain works, the SiCl₄ reacts chemically with the water and its concentration decreases rapidly; it reaches an emergency response planning guidelines level 2 (ERPG-2) of 5 parts per million (ppm) at about 570 m. We observed, however, that the physical effect of water curtains on reducing SiCl₄ concentration is insignificant when the chemical effect is eliminated. These results are crucial since they can be a scientific and quantitative basis for the 'technical guidelines for estimating the accident affected range'. In order to protect the public from chemical accidents, more toxic gas mitigation technologies need to be developed.

• Journal of Ecology and Environment
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• v.46 no.1
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• pp.54-61
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• 2022

Background: In South Korea, African swine fever virus (ASFV) has spread among wild boars through Gangwon-do to Dangyang-gun, Chungcheongbuk-do on the southern border of Gangwon-do. To prevent the spread of ASFV to African swine fever (ASF)-free areas, it is necessary to identify areas with a high probability of finding ASFV-infected carcasses and to reduce the density of wild boars in those areas. In this study, we described the propagation trend of ASFV among wild boars, constructed the habitat suitability maps for ASFV-infected carcasses, and suggested areas with a high probability of finding ASFV-infected carcasses and an important route of ASFV transmission. Results: Despite the active quarantine policies in Korea to prevent the spread of ASFV through wild boars, there was no significant difference in the monthly average of number of ASFV-infected carcasses observed between 2020 and 2021. The ASFV-infected carcasses were found more in winter and spring (January to April). Since the first ASF outbreak in wild boars on October 2, 2019, the maximum width of ASFV-infected carcass distribution area was 222.7 km for about 26 months till November 20, 2021. The habitat suitability map, based on GPS coordinates of ASFV-infected wild boar carcasses, shows that highly detectable areas of ASFV-infected carcasses were sporadically dispersed in western and southwestern parts of Gangwon-do, and ranged from north to south of the province along the Baekdudaegan Mountains, whereas poorly detectable areas ranged along the north to the south in the middle parts of the province. Conclusions: Our suitability model, based on the GPS coordinates of ASFV-infected carcasses, identifies potential habitats where ASFV-infected carcasses are likely to be found and ponential routes where ASFV is likely to spread. Among ASF-free areas, the areas with high suitability predicted in this study should be given priority as survey areas to find ASFV-infected carcasses and hunting areas to reduce wild boar populations.