• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.37-44
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• 1993

Calcia stabilized zirconia polycrystal (Ca-TZP) powders synthesized by hydrothermal treatment was sintered at a temperature range of $1200^{\circ}C~1400^{\circ}C$ and investigated the properties of sintered body and the behaviors of isothermal phase transformation. The sintered bodies of Ca-TZP were shown the density of about 97% and the average mean tetragonal grain size of about $0.1~0.25{\mu}m$. Also, Ca-TZP specimen was more stable during aging at $250^{\circ}C$ than that of Y-TZP ceramics.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.749-756
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• 2019

Na-X and Na-A zeolites that give high adsorption capacity for heavy metals in an aqueous system were synthesized from the coal fly ash obtained from a thermoelectric power plant using a fusion method. The characteristics and Cu(II) adsorption capacity of the synthetic zeolites were also compared to those of using a commercial zeolite. For the selection of optimum conditions of zeolite synthesis, the effects of major parameters in the fusion method such as a dosage ratio of NaOH, aging time, hydrothermal reaction time, and also the dosage ratio of NaAlO₂ (Na-A) on the characteristics and Cu(II) adsorption capacity of the synthetic zeolites were studied. For the analysis of characteristics of the synthetic zeolites, X-ray diffraction (XRD), cation exchange capacity (CEC), Brunaue-Emmett-Teller (BET) and scanning electron microscopy (SEM) were used. The optimum conditions for the synthesis of zeolites with a high adsorption capacity for cationic heavy metals including Cu(II) were the aging time of 6 h, hydrothermal reaction time of 6 h and NaOH and NaAlO₂ dosage ratio of 1.5 and 0.5 (Na-A), respectively. According to the Langmuir isotherm test, maximum Cu(II) adsorption capacities of the synthetic and commercial Na-X and Na-A zeolites were found to be 90.1, 105.26, 102.05, and 109.89 mg/g, respectively. This indicates that the adsorption capacity of synthetic zeolites was comparable to commercial ones. The results of this study also suggest that the coal fly ash can be potentially used as a raw material for the zeolite synthesis.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.102-108
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• 1997

ZrO2 powders stabilized with Y2O3 and CeO2 of various compositions were prepared by the coprecipitation of water-soluble ZrOCl2.8H2O, YCl3.6H2O and Ce(NO3)3.6H2O, and their compacts were pressurelessly sintered at 1400 and 150$0^{\circ}C$ for 2hrs in air. 2mol% Y2O3-ZrO3 showed the most superior strength (1003MPa) and microhardness (12.6GPa), while 10 mol%CeO2-ZrO2 had the hightest toughness (13.3 MPa.m1/2) after sintering at 140$0^{\circ}C$. The addition of Y2O3 into Y2O3-ZrO3 decreased mean grain size and increased strength and hardness but decrease toughness. On the other hand, the addition of CeO2 into Y2O3-ZrO2 enhanced the stability of tetragonal phase during low-temperature aging for a long time under hydrothermal atmosphere.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.2
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• pp.113-121
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• 2022

In this study, fermented Lycium chinense (L. chinense) extract was used to analyze the efficacy of nitric oxide (NO) and anti-aging inhibition to verify its usefulness as a functional cosmetic material. L. chinense was extracted with hydrothermal and 70% ethanol as a solvent, fermented, concentrated, and freeze-dried to prepare a sample, followed by MTT assay, NO inhibition assay, western blot assay, and UPLC analysis.As a result of the analysis of NO inhibitory efficacy, fermented L. chinense water extract (FLW) and fermented L. chinense 70% ethanol extract (FLE) showed excellent NO inhibitory efficacy of 47.96% and 56.71%, respectively. As a result of measuring the expression patterns of the wrinkle-related proteins MMP-1, and TRPV-1 through Western blot, both FLW and FLE confirmed the inhibitory efficacy of MMP-1 and TRPV-1. Based on the results of the experiment, the fermented L. chinense extract is expected to have a high application value as a functional cosmetic material related anti-inflammatory, and anti-aging.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.541-548
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• 2019

Zirconia (ZrO₂) materials are widely used in a variety of energy systems and devices. When nanorod-shaped ZrO₂ is used as energy materials, ionic conductivity and mechanical strength can be improved compared to the characteristics of conventional spherical-shaped nanomaterials. In this study, we synthesized ZrO₂ nanorods and investigated the shape change of them depending on various synthesis conditions such as precursor concentration, synthesis temperature, synthesis period, and aging period. The obtained nanorods were casted into a membrane for alkaline water electrolysis system and subjected to basic performance evaluation for use as a separator. The structure and the shape of the nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the like.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1177-1185
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• 1996

Y-TZP/Ce-TZP ceramics having relative sintered densities of>95% average grain sizes of 0.36$\mu\textrm{m}$ microhar-dness of 1150 kg/mm2 fracture strength of 390-830 MPa and toughness of 6.4-10.2 MPa$.$mm1/2 were prepared by conventional sintering of 3 mol% Y2O3-ZrO2 and 12 mol% CeO2-ZrO2 powders at 1400 and 1500$^{\circ}C$ The average grain sizes of Y-TZP/Ce-TZP ceramics were mainly governed by those of Ce-TZP. White increasing Ce-TZP content toughness increased while microhardness and fracture strength decreased. With comparing microhardness and toughness fracture strength was more sensitive on not only grain size but also other factors such as microstructural and compositional variations. The densification of Y-TZP/Ce-TZP cermaics was not greatly affected by composition and soaking time at temperature over 1400$^{\circ}C$ With increasing CE-TZP content the stability of t-ZrO2 decreased under thermal aging in air whereas increased in hydrothermal atmosphere and aqueous solution.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.4
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• pp.653-662
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• 2010

This study investigates the effect of particle size on the detergency of particulate soil using an $\alpha-Fe_2O_3$ particle as the model. Monodispersed spherical $\alpha-Fe_2O_3$ particles were prepared by the hydrothermal aging of an acidic $FeCl_3$ and HCl solution. The $\xi$-potential of PET fiber was measured by the streaming potential method. The potential energy of interaction between the particle and fiber was calculated using the heterocoagulation theory for a sphere-plate model. The $\xi$-potential of PET fiber and potential energy of interaction between particles and fiber increased with a decreasing particle size in a DBS solution. However, in the nonionic surfactant solution, the $\xi$-potential signs of PET fiber and $\alpha-Fe_2O_3$ particles were (-) and (+), respectively; there was no repulsive power between the particles and substrate. The adhesion of particles to the fabric increased with increasing particle size in the anionic surfactant solution and their removal from the fabric increased with a decreasing particle size. The adhesion of particles to the fabric and their removal from the fabric was biphasic with a maximum and minimum at 0.1% concentration of the surfactant solution. In the nonionic surfactant solution the adhesion of particles to fabric and their removal from the fabric were greater than the ones in the anionic surfactant DBS solution.

• Journal of Applied Biological Chemistry
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• v.62 no.3
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• pp.305-313
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• 2019

Men's climactic syndrome, andropause, or testosterone deficit syndrome, is one of the new problems with the health of older men in the age of aging. This phenomenon is a natural phenomenon occurring in men as they age, clinically characterized by a decrease in blood testosterone levels and a marked decrease in physical and mental activity. The purpose of this study was to investigate the effect of hydrothermal extract of Taraxacum coreanum by comparing the levels of nitric oxide (NO) in the cavernosum and the levels of male hormone in the blood. Taraxacum coreanum extract increased NO production in vitro and in vivo in a dose-dependent manner. Levels of dihydrotestosterone and 17-hydroxyysteroid dehydrogenases, as well as levels of neurogenic nitric oxide synthase and cGMP, increased significantly in elderly rats (22 weeks) after 4 weeks of daily intake of Taraxacum coreanum extract. However, prostaglandin $E_2$, testosterone, and sexually-hormone-binding globulin levels were not different among all groups. Furthermore, total sperm and motile sperm counts were also no significant difference. Overall, these results suggest the possibility of Taraxacum coreanum extract as a safe and effective natural substance for enhancing NO, cGMP and free testosterone.

• Membrane Journal
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• v.29 no.5
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• pp.263-275
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• 2019

In the present study, thickness of MOR zeolite membranes was controlled by changing seed size, seeding amount, and aging time of hydrothermal solution, and then effect of membrane thickness on pervaporative ethanol dehydration for 90 wt.% ethanol-water mixture was investigated. First, nanosize MOR zeolite seeds with a diameter of 20 to 30 nm was successfully prepared by planetary milling a laboratory synthesized MOR zeolites and the coating amount was controlled by seed concentration and infiltration volume of coating solution during vacuum-assisted seeding. As seeding amount decreased, membrane thickness was reduced up to around $4{\mu}m$. The MOR zeolite membrane having a thickness of $4{\mu}m$ showed a water/ethanol separation factor of 760 and water flux of $1.0kg/m^2h$. The excellent water flux was due to the reduced membrane thickness which was derived from the nanosize seed. Therefore, it could be concluded that membrane thickness control by using nanosize seed can be a crucial factor to improve pervaporative water flux of MOR zeolite membrane.