• Journal of fish pathology
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• v.35 no.1
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• pp.77-92
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• 2022

Aquaculture development is based on the ideas of increasing production while reducing economic losses. Bacterial diseases are the leading source of fish cases. Citrobacter freundii has been linked to septicemia and mortality all over the world. In the current study, the cause of mortality in O. niloticus was C. freundii MW279218. External hemorrhages were seen on the affected fish, as well as paleness in the liver and kidney congestion. C. freundii MW279218 had a median lethal dosage of 1.5×10⁵ CFU/mL. Zinc oxide and zinc oxide nanoparticles (ZnO-NPs) were tested for their biocidal effectiveness against C. freundii MW279218. The lethal effect of ZnO-NPs for C. freundii MW279218 was 100% when compared to zinc oxide compound, and the inhibition zone width was 2.31.1mm at the highest tested concentrations (70 mg/L) compared to the lowest (35 and 45 mg/L, respectively). Fish were fed three different diets for 28 days: diet 1 (no additives), diet 2 (100 mg of ZnO-NPs/kg of feed), and diet 3 (200 mg of ZnO-NPs/kg of feed). Organs were also collected for histopathology 96 hours after injection (P<0.05). In the groups given 200 mg of ZnO-NPs, there was 10% mortality and 80% RPS. The group fed 100 mg of ZnO-NPs/kg, on the other hand, had 20% mortality and 60% RPS, compared to 50% mortality in the control positive group. Histopathological examinations demonstrated significant alterations in the control positive group and mild lesions in the hepatopancreas of the groups administered 100 mg ZnO-NPs/kg of feed. The groups fed 200 mg of ZnO-NPs/kg diet, on the other hand, showed no histological alterations. ZnO-NPs were found to be effective in the up regulation of both IL-10 and complement 5 immune-related genes.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.301-307
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• 2012

SiAlON glasses are silicates or alumino-silicates, containing Mg, Ca, Y or rare earth (RE) ions as modifiers, in which nitrogen atoms substitute for oxygen atoms in the glass network. These glasses are found as intergranular films and at triple point junctions in silicon nitride ceramics and these grain boundary phases affect their fracture behaviour. This paper provides an overview of the preparation of M-SiAlON glasses and outlines the effects of composition on properties. As nitrogen substitutes for oxygen in SiAlON glasses, increases are observed in glass transition temperatures, viscosities, elastic moduli and microhardness. These property changes are compared with known effects of grain boundary glass chemistry in silicon nitride ceramics. Oxide sintering additives provide conditions for liquid phase sintering, reacting with surface silica on the $Si_3N_4$ particles and some of the nitride to form SiAlON liquid phases which on cooling remain as intergranular glasses. Thermal expansion mismatch between the grain boundary glass and the silicon nitride causes residual stresses in the material which can be determined from bulk SiAlON glass properties. The tensile residual stresses in the glass phase increase with increasing Y:Al ratio and this correlates with increasing fracture toughness as a result of easier debonding at the glass/${\beta}-Si_3N_4$ interface.

• Journal of the Korean Applied Science and Technology
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• v.28 no.4
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• pp.455-463
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• 2011

The average sulfur content of crude oil is 2.2%. Coal is about 0.3 to 4.0 percent of the sulfur gases or particles being discharged into the atmosphere through the chimney as 1 to 2% $SO_3$(Sulfur trioxide) and about 95% of the $SO_2$ is reported. $SO_3$ gas, which has many different causes of, as the combustion of sulfur containing fuel during the air due to the excess $SO_2$ gas is oxidized to $SO_3$ gas. Sulfur trioxide emitted from high sulfur heavy oil fired boiler caused white plume in stack and high temperature and cold end corrosion of facilities. So, in order to control sulfur trioxide concentration of Fuel gas in boiler, various of additives are used in other foreign. They are injected to Fuel Oil and consumed in boiler and reduce ash and the conversion rate of sulfur trioxide. In domestic, MgO compounds are used as additives but the total volume of them are made from other foreign company. In this study, MgO compounds were developed with liquid MgO compounds and field application was accomplished. The effect of newly developed chemicals and process were nearly equal to foreign products. In Consequent, the chemicals and process produced by newly developed technology can be substituted for foreign products and reduce the cost of plant operation.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.173-183
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• 1988

Effects of oxide additives such as MoO3, MnO2 ZrO2 and Fe2O3 on the phase separation and the chemical durability of sodium borosilicate glasses which are the host of waste glasses have been investigated as the basic study on the nuclear-waste immobilization through vitrification. MoO3 and MnO2 were found to be phase separation promotors which increased the temperature as well as catalyzed nucleation and growth for the phase separation of the 10Na2-O-3OB2O3-6OSiO2 (wt%) parent glass within the immiscibility region. The glasses had the interconnected phase-separated structure as the amount of addition increased. On the other hand, ZrO2 and Fe2O3 were inhibitors which showed the reverse effects to the above promotors. It was also found that addition of MoO3 could cause the phase separaton of the 20Na2O-10B2O3-70SiO2(wt%) glass even within the miscibility region. Addition of ZrO2 and Fe2O3 increased the chemical durability of the parent glass within the immiscibility region. Within the miscibility region, however, the addition of 1.96 wt % of MoO3 increased the chemical durability considerably, while MnO2 had little effects.

• Journal of Powder Materials
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• v.26 no.5
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• pp.415-420
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• 2019

SiAlON ceramics are used as ceramic cutting tools for heat-resistant super alloys (HRSAs) due to their excellent fracture toughness and thermal properties. They are manufactured from nitride and oxide raw materials. Mixtures of nitrides and oxides are densified via liquid phase sintering by using gas pressure sintering. Rare earth oxides, when used as sintering additives, affect the color and mechanical properties of SiAlON. Moreover, these sintering additives influence the cutting performance. In this study, we have prepared $Yb_{m/3}Si_{12-(m+n)}Al_{m+n}O_nN_{16-n}$ (m = 0.5; n = 0.5, 1.0) ceramics and manufactured SiAlON ceramics, which resulted in different colors. In addition, the characteristics of the sintered SiAlON ceramics such as fracture toughness and microstructure have been investigated and results of the cutting test have been analyzed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.593-596
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• 2003

A proposed way to prepare $YBa_2Cu_3O_y$ wires or tapes is that Ag is used as substrate and melting point of $YBa_2Cu_3O_y$ is decreased to lower than the melting point of silver ($961\;^{\circ}C$). Therefore after the deposition of $YBa_2Cu_3O_y$ film on Ag substrate, the heat treatment can be carried out below the Ag melting point. Silver (Ag) and Lead oxide(PbO) were selected to be additives for $YBa_2Cu_3O_y$. Different Ag and PbO contents were added in $YBa_2Cu_3O_y$, the melting points of which were measured by DTA. In order to guarantee that the superconductivity of $YBa_2Cu_3O_y$ was not reduced after Ag and PbO added into $YBa_2Cu_3O_y$, their superconductivities were measured. It is proved that as additives, both Ag and PbO can reduce the melting point of $YBa_2Cu_3O_y$. For Ag doped $YBa_2Cu_3O_y$, $T_c$ is about 93K and ${\Delta}Tc$ is $2{\sim}3K$. For PbO doped $YBa_2Cu_3O_y$, $T_c$ is $88K{\sim}92K$ and ${\Delta}T_c$ is $11{\sim}12K$. When 10 wt% of Ag and 10 wt% PbO were added in $YBa_2Cu_3O_y$, the melting point of the mixture of $YBa_2Cu_3O_y$ (80 wt%), Ag (10 wt%) and PbO (l0 wt%) is $943^{\circ}C$. The transition temperatures ($T_c$) of the sample is 91.8 K.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1323-1330
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• 1995

The effects of various additives on the microstructures of sintered ZnO varistors were examined. Bi2O3, Sb2O3 and Cr2O3 were added to ZnO step by step to identify the effect of each component. The specimens were prepared by sintering at 110$0^{\circ}C$ and 120$0^{\circ}C$ in ambient atmosphere. In ZnO-Bi2O3-Sb2O3 ternary system, decrease of averge grain size due to antimony oxide addition depends on sintering temperature as well as Bi2O3 content. When Sb2O3 was partly or completely replaced by Cr2O3, grain size was further reduced. A significant amount of pyrochlore phase which was not transformed to spinel and Bi2O3-rich liquid phase seemed to remain during sintering at 110$0^{\circ}C$. Unlike ZnO-Bi2O3-Sb2O3 system, the $\alpha$-spinel phase containing significant amount of Cr did not transform to pyrochlore during furnace cooling. Fine spinel particles around 1${\mu}{\textrm}{m}$ size were ovserved within ZnO grains and grain boundaries, which were believed to be responsible for grain-growth inhibition in ZnO-Bi2O3-Sb2O3.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.118-125
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• 1986

A small scale combustion unit was built to evaluate the CO suppression effects by various chemical additives added to coal briquettes. Among the additives tested comprising various transition metal compounds with catalytic activities, natural minerals and oxidizing agents, the copper component has shown the best CO suppression effect, and in particular, copper oxide dispersed on porous supports such as ${\gamma}-Al_2O_3$ was most effective. For instance, 0.5% of copper added to coal briquettes in this way bas exhibited 1.4 % CO in the combustion gas at the ignition and beginning stage of combustion and 0.3 % CO at the final stage. The effects of calcium compounds on the fixation of sulfur in coal were also evaluated to reduce the contents of sulfur compounds in the combustion gases.

• Current Optics and Photonics
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• v.5 no.4
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• pp.450-457
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• 2021

Upconversion (UC) properties of Y₂O₃:Ho³⁺/Yb³⁺ spherical particles synthesized by spray pyrolysis were investigated by changing the dopant concentration and calcination temperature. Citric acid (CA), ethylene glycol (EG) and N, N-dimethylformamide (DMF) were used to control the microstructure of Y₂O₃:Ho³⁺/Yb³⁺ particles. In terms of achieving the highest UC green emission intensity, the optimal concentrations of Ho³⁺ and Yb³⁺ were found to be 0.3% and 3.0%, respectively. In addition, the UC intensity of Y₂O₃:Ho³⁺/Yb³⁺ showed a linear relationship with the crystallite size. The use of organic additives allows Y₂O₃:Ho³⁺/Yb³⁺ particles to have a spherical and dense structure, resulting in significantly reducing the surface area while maintaining high crystallinity. As a result, the UC emission intensity of Y₂O₃:Ho³⁺/Yb³⁺ particles having a dense structure showed the UC emission intensity about 3.8 times higher than that of hollow particles prepared without organic additives. From those results, when Y₂O₃:Ho³⁺/Yb³⁺ particles are prepared by the spray pyrolysis process, the use of the CA/EG/DMF mixtures as organic additives has been suggested as an effective way to substantially increase the UC emission intensity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.410-417
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• 2019

The enhancement effects of sea mustard extract (SME), starfish collagen peptide (SCP) and a mixture of the two (MIX) on skin activity were evaluated to investigate the possibility of using marine-derived extracts as cosmetic additives. The anti-inflammatory activity, whitening activity and skin elasticity activity of the extracts were analyzed to evaluate their skin-activating effects. Inhibiting the generation of nitric oxide (NO) and the tyrosinase and elastase inhibitory activities were assessed as the bio-markers for evaluating skin activity. SME, SCP and MIX did not show cytotoxicity within the concentration range of 1.0-50 ㎍/mL. In addition, SME, SCP and MIX all increased NO production and the tyrosinase and elastase inhibitory activities in a concentration-dependent manner. The activity of MIX was significantly increased compared to that with using SME or SCP alone. Taken together, when natural extracts are applied as cosmetic additives, the results demonstrate that using a mixture of SME and SCP may have a greater synergistic effect than that when using only a single extract. Therefore, this study contributes to the knowledge about the kinds and composition of several natural extracts when they are used as cosmetic additives.