• Herbal Formula Science
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• v.26 no.4
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• pp.295-306
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• 2018

Schisandra chinensis (SC) and Lycium chinense (LC) were widely distributed in Asia and the fruit has been used traditionally for medicinal herbs. The processing method was solid-state fermentation using Aspergillus oryzae for 48 h after stir-frying treatment at $220^{\circ}C$ for 12 min. In this study, in vitro the anti-inflammatory effect and in vivo hangover reduction were compared to unprocessed SC and LC water extract. Anti-inflammatory effects have been evaluated in pro-inflammatory mediators which were secreted by lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Nitric oxide (NO) was determined using Griess reaction. Proinflammatory cytokines such as tumor necrosis factor $(TNF)-{\alpha}$ and interleukin $(IL)-1{\beta}$ were measured by enzyme-linked immunosorbent assays (ELISA). Alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities were compared to processed SC or LC and mixtures thereof (1:1). In vivo study was compared to hangover relief in alcohol-fed mice. After administering a mixture of SC and LC (300 mg/kg) water extract (1:1), mice were fed 3 g/kg of ethanol. Serum was collected at 1, 3, and 5 h intervals to analyze ethanol and acetaldehyde levels using a colorimetric assay kit. The processed SC and LC water extracts compared to raw materials significantly inhibited LPS-induced NO and inflammatory cytokine production in RAW 264.7 cells. The results of the hangover mouse model are also consistent with anti-inflammatory effects. These results suggest that processed SC and LC extracts may be functional materials for the treatment of inflammation and hangover.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.165-173
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• 2019

Lithium anodes (13, 15, 17, and 20 wt% Li) were fabricated by mixing molten lithium and iron powder, which was used as a binder to hold the molten lithium, at about $500^{\circ}C$ (discharge temp.). In this study, the effect of applied pressure and lithium content on the discharge properties of a thermal battery's single cell was investigated. A single cell using a Li anode with a lithium content of less than 15 wt% presented reliable performance without any abrupt voltage drop resulting from molten lithium leakage under an applied pressure of less than $6kgf/cm^2$. Furthermore, it was confirmed that even when the solid electrolyte is thinner, the Li anode of the single cell normally discharges well without a deterioration in performance. The Li anode of the single cell presented a significantly improved open-circuit voltage of 2.06 V, compared to that of a Li-Si anode (1.93 V). The cut-off voltage and specific capacity were 1.83 V and $1,380As\;g^{-1}$ (Li anode), and 1.72 V and $1,364As\;g^{-1}$ (Li-Si anode). Additionally, the Li anode exhibited a stable and flat discharge curve until 1.83 V because of the absence of phase change phenomena of Li metal and a subsequent rapid voltage drop below 1.83 V due to the complete depletion of Li at the end state of discharge. On the other hand, the voltage of the Li-Si anode cell decreased in steps, $1.93V{\rightarrow}1.72V(Li_{13}Si_4{\rightarrow}Li_7Si_3){\rightarrow}1.65V(Li_7Si_3{\rightarrow}Li_{12}Si_7)$, according to the Li-Si phase changes during the discharge reaction. The energy density of the Li anode cell was $807.1Wh\;l^{-1}$, which was about 50% higher than that of the Li-Si cell ($522.2Wh\;l^{-1}$).

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1308-1314
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• 2018

$Er^{3+}$ and $Yb^{3+}$ co-doped $Y_3Ga_5O_{12}$ polycrystalline powders were prepared by using a solid-state reaction method, and their crystallinities were measured using X-ray diffraction. According to the results of X-ray diffraction, the powders showed a polycrystalline tetragonal structure. The photoluminescence and the upconversion luminescence properties of the $(Y_{0.85-x}Yb_{0.15})_3Ga_5O_{12}:Er^{3+}_x$ (x = 0.03, 0.06, 0.09, 0.12 and 0.15) phosphors were investigated in detail. Green and red upconversion emissions were observed for the phosphors excited by 980 nm radiation from a semiconductor laser. The powders exhibited strong green and weak red upconversion emission peaks at 553 and 660 nm, respectively. Also, their upconversion processes were explained using an energy-diagram analysis and the strongest upconversion intensity was emitted by the powder with a 0.12 mol $Er^{3+}$ ion concentration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.1
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• pp.1-7
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• 2021

This study investigated the structural, dielectric, ferroelectric, and strain properties of (0.98-x)Bi1/2Na1/2TiO3-0.02BiFeO3-xSrTiO3 (BNT-BF-100xST, x＝0.20, 0.22, 0.24, 0.26, and 0.28). All samples were successfully synthesized using the conventional solid-state reaction method and sintered at 1,175℃ for 2 h. The average grain size of the BNT-BF-100x ceramics decreased with increasing ST content. Furthermore, we observed that the ferroelectric- relaxor transition temperature (TF-R) decreased with increasing ST content, which eventually vanished in the BNT-BF-24ST ceramics. The results indicated that a ferroelectric to relaxor phase transition could be induced by ST modification. Consequently, a large electromechanical strain of 633 pm/V at 4 kV/mm was observed for the BNT-BF-26ST ceramics. These results imply that our materials have the competitive advantage of larger strain under lower operating field conditions compared with other BNT-based lead-free piezoelectric ceramics. We expect that BNT-BF-ST lead-free piezoelectric ceramics are promising candidates as a novel ternary BNT-based system and can find potential applications in actuators.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.9-13
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• 2022

Bullets flying with a light from the back are called "tracers". Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called "thermoluminescence (TL)". This study aims to compare the TL emission of Dy³⁺, La³⁺ and Ho³⁺ doped MgB₄O₇ phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB₄O₇. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy³⁺, La³⁺ and Ho³⁺ (at different concentrations of 5, 10, 15 and 20 %) doped MgB₄O₇ were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.24-31
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• 2022

This study investigated microstructures, crystal structures, polarization, dielectric and electromechanical properties of 0.76Bi_1/2Na_1/2TiO₃-0.24SrTiO₃ (BNT-24ST)-based piezoceramcs by adding Li₂CO₃ and B₂O₃ (LB) as sintering aids for low-temperature sintering. All samples were successfully synthesized using conventional solid-state reaction method and sintered at 950, 1,000, 1,050, 1,100 and 1,175℃ for 2 hours. Without LB, specimens required sintering temperatures over 1,175℃ for sufficient densification, while the addition of 0.10-mol LB decreased the sintering temperatures down to 950℃. The average grain size and dielectric properties of BNT-24ST-10LB ceramics were enhanced with increasing sintering temperature. We found that the low-temperature sintered BNT-24ST piezoceramics by adding LB showed the d₃₃*value of 402 pm/V at 4 kV/mm after sintering at 1,050℃, which was better than that of high-temperature fired specimens sintered at 1,175℃ without LB (242 pm/V). We believe that the results of this study promise a candidate for low-cost multilayer ceramic actuator applications.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.15-22
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• 2023

Recent studies have actively investigated ways to improve the economic feasibility and efficiency of the Fischer-Tropsch process by increasing the yields of the monocyclic aromatic compounds (BTEX). In this study, ethylene was selected as a model of F-T-derived hydrocarbons, and the ethylene-to-aromatics (ETA) reaction was investigated according to changes in acid characteristics, mesopores, and crystallinity of HZSM-5 (HZ5). Fluorinated HZ5 was prepared by calcination followed by impregnation of an aqueous NH₄F solution having different molar concentrations in HZ5, and the structural and chemical properties of F/HZ5 were investigated through Brunauer-Emmett-Teller (BET), solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), NH₃-temperature-programmed desorption (TPD), and pyridine-IR spectroscopy. The ETA reactions were performed at 673 K under 0.1 MPa, and fluorinating HZ5 by an aqueous NH₄F solution of 0.17 M improved ethylene conversion, BTEX selectivity, and catalytic stability due to acidity, mesopore fraction, and crystallinity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.136-142
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• 2022

The crystal structure, grain growth behavior, and dielectric properties of BaTiO₃ have been studied with the addition of Dy₂O₃. The powders were synthesized at ratios of (100-x)BaTiO₃-xDy₂O₃ (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250℃ for 2 hours in air. As the amount of added Dy₂O₃ was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba₁₂Dy_4.67Ti₈O₃₅ appeared when Dy₂O₃ was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy₂O₃ increased. It can be explained that the grain growth behavior of the Dy₂O₃ added-BaTiO₃ occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.42-50
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• 2023

In this study, hexagonal ferrite powder with chemical formula SrZn_2-xCo_xFe₁₆O₂₇ was synthesized by a solid-state reaction method and its electromagnetic (EM) wave absorption characteristics were evaluated in the frequency range of 0.1-18 GHz with absorber thickness range of 0 - 10 mm. Reflection loss (RL) affecting electromagnetic wave absorption performance was calculated based on the transmission line theory using measured complex permeabilities and permittivities. RL spectra were also directly measured for some samples. They were well matched with calculated results. High-frequency complex permeability characteristics were changed gradually according to the amount of Co substitution (x). The EM wave absorption frequency band could be tuned accordingly. Hexaferrite samples with x = 1.0, 1.25, and 1.5 exhibited remarkable maximum electromagnetic wave absorption performances with minimum RL (RL_min) lowered than -50 dB. They also showed a very broad frequency band (Δf > 10 GHz) in which more than 90% of the EM wave energy absorption occurred (RL ≤ -10 dB).

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.330-336
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• 2023

The effects of Ni²⁺ substitution for Mg²⁺-sites on the microwave dielectric properties of (Mg_1-xNi_x)(Ti_0.95(Mg_1/3Ta_2/3)_0.05)O₃ (0.01 ≤ x ≤ 0.05) (MNTMT) ceramics were investigated. MNTMT ceramics were prepared by conventional solid-state reaction. When the MgO / TiO₂ ratio was changed from 1.00 to 1.02, MgTi₂O₅ was detected as a secondary phase along with the MgTiO₃ main phase in the MNTMT specimens sintered at 1,400 ℃ for 4h. For the MNTMT specimens with MgO / TiO₂ = 1.07 sintered at 1,400 ℃ for 4h, a single phase of MgTiO₃ with an ilmenite structure was obtained from the entire range of compositions. The relative density of all the specimens sintered at 1,400 ℃ for 4h was higher than 95 %. The quality factor (Qf) of the sintered specimens depended strongly on the degree of covalency of the specimens, and the sintered specimens with x = 0.01 showed the maximum Qf value of 489,400 GHz. The dielectric constant (K) decreased with increasing Ni²⁺ content because Ni²⁺ had a lower dielectric polarizability (1.23ų) than Mg²⁺ (1.32ų). As Ni²⁺ content increased, the temperature coefficient of resonant frequency (TCF) improved, from -55.56 to -21.85 ppm/℃, due to the increase in tolerance factor (t) and the lower dielectric constant (K).