• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.169-178
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• 1990

The sintering characteristics of ZrO2 were analyzed in terms of pore microstructure and kinetics of pore elimination. The pore structue of the ZrO2 sample prepared from colloid suspension was characterized by three distinct types of pores ; intradomain, interdomain, and intergglomerate pores. Sintering data at 1600$^{\circ}C$ showed that pores larger than a certain critical size(∼3$\mu\textrm{m}$) were difficult to remove, and this was analyzed in terms of the interagglomerate pore formed from the suspension under the condition of low kinetic stability, that is, the stability ratio smaller than its critical value. A theoretical equation for densification rate was derived and was applied to the densification rate of the ZrO2 polycrystalline body containging both the matrix(the 1st-generation) pores and the interagglomerate (the 2nd-generation) pores under the condition of slow grain growth.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.561-563
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• 2006

This paper summarizes the results of these efforts by offering the PV generation system with solar tracking. The status of PV generation system with solar tracking components and interconnection and effects are semmarized. Hence this paper duscusses only points that might be useful for application.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.82-87
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• 1998

In the oxidation process of the $NH_3/O_2$ oxidation method, adding $NH_3$ gas to $O_2$ gas, the detected outlet gases in the reaction quartz chamber are N2, $O_2$ and $H_2O$ and in addition, a very small quantity of $CO_2$, NO and $NO_2$ are detected. Two kinds of species ($O_2$ and H2O) contribute to oxidation, so the growth rate is determined by oxidation temperature and by also partial pressure of the NH3 and $O_2$ gases. The slop of growth rate is identified to be medial and in parallel between that of the dry and wet oxidation. Auger electron spectroscopy (AES) indicates that $NH_3/O_2$ oxide film has a certain stoichiomerty of $SiO_2$, this oxidation method restrains the generation of defects in the $SiO_2/Si$ interface, minimizing fixed charges. The breakdown voltage of $NH_3/O_2$ oxide film (470$\AA$) is 57.5 volts, and the profile of the C-V curve including flat band voltage (0.29 volts) agree with the ideal curve.

• Journal of Surface Science and Engineering
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• v.47 no.4
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• pp.210-214
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• 2014

We investigated emission characteristics of tandem organic light emitting devices (OLEDs) with p-type materials as charge generation layer. The tandem OLEDs were fabricated by using $MoO_x$, $WO_x$, C60 and HATCN as p-type material or not using p-type material for charge generation. When HATCN was used as p-type material, it showed high current density at low applied voltage, but increase of efficiency was small because of charge unbalance in emitting layer. In case of tandem OLED not using p-type material, applied voltage increased remarkably because of difficulty of hole injection. In case of $MoO_x$, $WO_x$ or C60 as p-type material, current emission efficiency increased greatly. In particular, current emission efficiency of tandem OLED using $MoO_x$ as p-type material increased up to 3 times than current emission efficiency of single OLED. The Commission Internationale de l'Eclairage (CIE) 1931 color coordinates were changed by overlapping of 504 nm emission wavelength. As a result, emission efficiency of tandem OLED improved compared with single OLED, but driving voltage also increased by increase of organic layer thickness.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.76-86
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• 2021

Technologies for lithium secondary batteries are now increasingly expanding to simultaneously improve the safety and higher energy and power densities of large-scale battery systems, such as electric vehicles and smart-grid energy storage systems. Next-generation lithium batteries, such as lithium-sulfur (Li-S) and lithium-air (Li-O₂) batteries by adopting solid electrolytes and lithium metal anode, can be a solution for the requirements. In this analysis of battery technology trends, solid electrolytes, including polymer (organic), inorganic (oxides and sulfides), and their hybrid (composite) are focused to describe the electrochemical performance achievable by adopting optimal components and discussing the interfacial behaviors that occurred by the contact of different ingredients for safe and high-energy lithium secondary battery systems. As next-generation rechargeable lithium batteries, Li-S and Li-O₂ battery systems are briefly discussed coupling with the possible use of solid electrolytes. In addition, Electronics and Telecommunications Research Institutes achievements in the field of solid electrolytes for lithium rechargeable batteries are finally introduced.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.249-254
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• 2011

A nonthermal plasma reactor in conjunction with a tubular type with a ferroelectric (high-dielectric ceramic) pellet layer was designed and constructed. $SrBiTaO_9$ (SBT) pellets with 2.0 mm in diameter were held within the tube arrangement by two metal mesh electrodes (20 mm separation) connected to a high-voltage AC power supply. The dielectric constant of SBT pellets was 150 at room temperature and 500 at curie temperature ($335^{\circ}C$). The generation rate of ozone in the plasma reactor almost linearly increased with increasing applied voltage. In the case of the plasma reactor packed with SBT pellets the generation rate of ozone sharply increased at the applied voltage more than 20 kV. The ozone generation rate at the negative corona discharge was higher than that of the positive corona discharge. However, the destruction efficiency of toluene and methylene chloride was not increased in proportion to ozone concentration.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.1-6
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• 2008

Thermoelectric properties of calcium cobalt layer structure oxide system, $Ca_3Co_2O_6$ and $Ca_3Co_4O_9$ were investigated at the temperature range of 300 to 1000K for the application of thermoelectric generation. In the composition, the Ca site was partially substituted with Bi, Sr, La, K and the Co site was partially substituted with Mn, Fe, Ni, Cu, Zn. The thermoelectric properties of Bi substituted $Ca_3Co_4O_9$. $Ca_{2.7}Bi_{0.3}Co_4O_9$ for electrical conductivity, Seebeck coefficient and power factor were $85.4({\Omega}$cm)^{-l}, $176.2{\mu}V/K$ and $265.2{\mu}W/K^m$, respectively. The unit thermoelectric couple was fabricated with the p-type of $Ca_{2.7}Bi_{0.3}Co_4O_9$ and n-type ($Zn_{0.98}Al_{0.02}$)O thermoelectrics whose figure-of-merit(Z) were $0.87{\times}10^{-4}/K$ and $0.41{\times}10^4/K$, respectively. The generated thermoelectric power was about 30mV at the temperature difference of 120K in the unit thermoelectric couple.

• Ceramist
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• v.9 no.6
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• pp.12-17
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• 2006

One of characteristic of $Cr_2O_3-containing$ refractory is excellent resistance to corrosion. However, there is a problem that hexa-valent chromium, which is noxious to the human body, is easily formed by reaction between the refractory and slag with CaO, $Na_2O$ and/or $K_2O$. In this article, the reason why the $Cr_2O_3-containing$ refractory has excellent corrosion resistance qualities, he conditions under which hexa-valent chromium formed, methods for suppressing generation of hexa-valent chromium and the possibility of the refractory components excluding $Cr_2O_3$ for the furnace are described as a base of development of further excellent refractories.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 1999.09a
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• pp.1-63
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• 1999

Generation of abnormally large grains in the microstructure of small grains has been investigated on some ferrites. Some fractions of large grains were observed in the microstructure of sintered ZnFe$_2$O$_4$, Mn-ZnFe$_2$O$_4$, Fe$_3$O$_4$(in N$_2$) and MnFe$_2$O$_4$(in air). On the other hand, the large grains were not observed in NiFe$_2$O$_4$ and CoFe$_2$O$_4$, independent of calcining and sintering conditions. The large grains seem to be generated in such ferrites that are easy to vary their compositions or valencies at high temperatures. As the sintering proceeded, the number of large grains was increasing to form a continuous structure consisting of large grains, while the size of large grains did not increase remarkably. In addition, the growth of small grains was also very slow during the generation of the large grains. The large grains appeared to be suddenly generated after some induction periods. Avrami equation could be applied to the relation between net volume of large grains and sintering time. Thus, the grain boundaries may be strongly stabilized when the large grains are generated. The large grain in generated by the local activation of the stabilized grain boundaries, which is caused by the variation of compositions or valencies during sintering. It is concluded that the essence of the abnormal grain growth is not the generation of abnormally large grains, but the abnormal stabilization and the local activation of the grain boundaries.

• Fisheries and Aquatic Sciences
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• v.24 no.12
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• pp.428-436
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• 2021

The aim of this study was to isolate and identify secondary metabolites from Sonchus brachyotus and evaluate their antioxidant and anti-inflammatory activities. In this study, we isolated three flavonoids from a 70% EtOH extract by Medium Pressure Liquid Chromatography (MPLC) and prep-High-Performance Liquid Chromatography (HPLC). To evaluate the biological activities (antioxidant and anti-inflammatory) of these flavonoids, their in vitro inhibitory activities against lipopolysaccharide (LPS)-induced reactive oxygen species (ROS) generation, nitric oxide (NO) production, and prostaglandin E₂ (PGE₂) secretion were determined. We successfully identified three flavonoids, namely luteolin (1), luteolin-7-O-β-D-glucoside (2), and luteolin-7-O-β-D-glucuronide (3) by spectral analyses. Luteolin (1) at 20 ㎍/mL inhibited ROS generation, NO production, and PGE₂ secretion by 48.6%, 61.28% and 12.10%, respectively, and luteolin-7-O-β-D-glucoside (2) inhibited NO and PGE₂ generation by 67.03% and 20.82%, respectively. Luteolin (1) and luteolin-7-O-β-D-glucoside (2) showed similar anti-inflammatory activities; however, luteolin (1) was observed to be a stronger antioxidant. Besides antioxidant and anti-inflammatory activities, S. brachyotus extract containing luteolin (1) and luteolin-7-O-β-D-glucoside (2) is considered to possess diverse biological activities. The results indicate that S. brachyotus is an edible medicinal plant, which is believed to be significant resource of functional foods.