• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.440-446
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• 2008

To manufacture the MLCC with X7R for high voltage stability, $BaTiO_3-MgO-MnO_2-Y_2O_3$ with $(Ba_{0.4}Ca_{0.6})SiO_3$ glass frit was formulated. Based on this composition, the addition of $Er_2O_3$ showed that TCC(Temperature Coefficient Capacitance) at $85^{\circ}C$ was improved from 5 % to ${\sim}0\;%$, but the dielectric constant and IR (Insulation Resistance) were decreased. The glass frit improved the dielectric constant and IR, so the appropriate contents of $Er_2O_3$ and glass frit were 0.6 mol% and 1 wt%, respectively. It showed that the dielectric constant and RC constant were 2,550 and 2,000 (${\Omega}F$), respectively in the sintering condition at $1250^{\circ}C$ in PO2 $10^{-7}$ Mpa. The MLCC with $3.2{\times}1.6$ (mm) size and $1\;{\mu}F$ was also suited for X7R with the above composition.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.5-9
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• 2007

This study carried out to investigate the removal capacity of heavy metals such as Cu (II), Zn (II) and Cd (II) dissolved in aqueous solution in the soils collected from Hyeon-Dong (HD), San-seong (SS), Keum-chon (KC) and Keum-Hac (KH) located in the upper Banbyun stream. The pH of all the soils was weak alkali such as 8.8 9.2. According to the analysis of chemical composition of the soils, the amount of $SiO_2$, $AlO_2$ and CaO were similar in all tested soils. However, the amount of $K_2O$, $FeO_3$ and MgO were different from each soil. The XRD measurement with these soils showed that quartz and feldspar were presented in all tested soils, and the distribution of kaoline, illite, montmorillonite, vermiculite and calcite were different from each soil. The results of the removal capacity of heavy metals indicated that all the soils had more than 98% of the removal efficiency of Cu (II), Zn (II) and Cd (II), and among the heavy metals, Cu (II) was removed the most effectively. These results suggested that the soils collected from the upper Banbyun stream have the high removal capacity of heavy metals, and these soils could be used for the banking a river around the abandoned mine area, containing the higher concentrations of heavy metals than the usual stream.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.197-202
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• 1995

고주파용 전원의 필요성이 대두되면서 고주파에서 낮은 자기손실을 가진 재료의 개발이 요구되고 있다. Mn-Zn 페라이트의 자기손실은 전기비저항의 증거나 소결시 미세구조의 제어로 줄일 수 있다. 본 연구에서는 연쇄고온합성법(Self-propagation High- temperature Synthesis)에 의해 제조된 $_Mn_{0.72}$Z $n_{0.22}$)$_{0.94}$ (F $e_{2}$ $O_{3}$)$_{1.06}$ 조성의 Mn-Zn페라이트에서 첨가물이 미세구조와 자기적 성질에 미치는 영향에 대해 조사하였다. $SiO_{2}$와 Ca $Co_{3}$의 복합첨가에 의해 미세구조의 미세화와 아울러 낮은 자기손실 특성을 얻을 수 있었다. 그러나 첨가 물의 과다 첨가시에는 비정상입자성장 조직이 나타났으며 자기적 성질이 현저히 저하 하였다. 전기비저항, 자기손실의 주파수 의존 결과에 근거하여 주된 자기손실기구 및 이에 미치는 첨가물 효과에 대해 논하였다.

• Journal of the Korean Ceramic Society
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• v.18 no.3
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• pp.171-181
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• 1981

Alkaline-earth porcelains have been prepared from mixture of kaolin, quartz, and synthetic calcines obtained by calcining a mixture of kaolin and more than two different kinds of alkaline-earth carbonates. They were magnesium, calcium and barium carbonates which are inexpensive and readily available. The vitrification behavior of the batch mixes was investigated in the firing range of 1240$^{\circ}$to 1380$^{\circ}$, in relation to the body compositions. It appeared that the density and the firing temperature depended largely on the content of alkaline-earth oxides in the body. These porcelains posses excellant dielectric properties, and are especially valuable as bases for deposited carbon resistors for which they were developed. An illustrative composition is 50% Dong Hwa kaolin, 22.4% Chang Shin quartz, 27.6% calcine. The composition of the calcine is 70% Dong Hwa kaolin, 10.7% BaCO3, 13.5% CaCO3, 5.8% MgCO3. The specific resistance of this body is $1.2{\times}10^{15}$ ohm-cm at 5$0^{\circ}C$, $2.5{\times}10^{14}$ ohm-cm 10$0^{\circ}C$, $2.5{\times}10^{13}$ ohm-cm at 15$0^{\circ}C$, $1.8{\times}10^{12}$ohm-cm at 20$0^{\circ}C$.

• Journal of the Mineralogical Society of Korea
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• v.29 no.4
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• pp.239-254
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• 2016

The Hwangto cave is a sea cave which is located near shore in the Taeha-ri, Ulleung Island, being composed of the reddish tuff wall rock, the topic of this study, and the trachyte ceiling rock. The chemical compositions of the red tuff layer are 49.81-63.63% of $SiO_2$, 13.05-24.91% of $Al_2O_3$, 2.67-5.82% of $Fe_2O_3$, 2.87-6.92% of $Na_2O$, 2.37-3.85% of $K_2O$, 0.55-0.81% of $TiO_2$, 0-0.53% of MnO, 0.39-1.75% of MgO, and 0.60-1.40% of CaO with a pH ranging from 4.5 to 8. The reddish tuff are composed of 23.7-39.4% of anorthoclase, 16.9-33.3% of sanidine, 15.8-26.1% of illite, 5.1-9.0% of hematite, 0-3.7% of goethite, 6.9-9.9% of titanium oxide, and 0.9-9.5% of halite in mineral composition. Although it only includes anorthoclase, sanidine, and illite as major minerals, there can be additional vitric minerals that could not detected by the XRD. The mineralogy and textures of the tuff layer indicate that it became reddish due to the formation of amorphous palagonite and the oxidation of the iron as a heat from the trachytic lava affects the underlying tuff to altered. This iron oxides are enriched in the palagonite, or form microcrystalline or amorphous minerals. We thus suggest that the red tuff layer was generated by the combination of the thermal oxidation involved in the trachytic lava flow on the tuff layer, the palagonitization of the matrix of the tuff, and the oxidation of iron-bearing minerals.

• Journal of Plant Biology
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• v.13 no.2
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• pp.21-31
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• 1970

The rice variety, Nongkwang was used in two factorial experiments with the combination of 15 kg and 20 kg of N per 10 a, 3 levels of P2O5 (0, 4 and 8 kg per 10 a) and 4 levels of potash(0, 2, 4 and 8 kg per 10 a) in the reclaimed soil areas containing 0.48% on the average salt content throughout the year(0.67% at the end of April). The absorption of N, K and Ca was accelerated by increased N applications. The absorption of P itself was not enhanced by the increased application of P2O5 but the absorption of K2O reduced the absorption of Mg was affected. The increased application of K2O reduced the absorption of Si and seemed to increase the content of carbohydrate in the rice plants. Twenty kg of N and 4kg of P2O5 per 10 a produced satisfactory yields of rough rice, potash applications are ineffective in this experiment on rice grain production.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.31-43
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• 2014

The Yeongdeok granite emplaced in the eastern Yeongyang subbasin is typically a medium- to coarse-grained massive biotite granite. It intruded into Precambrian schist & gneiss complex and is unconformably overlain by Cretaceous sedimentary rocks. In this study, we attempt to investigate the magma type which formed Yeongdeok granite and estimate the emplacement depth using Al-in-hornblende geobarometer to mineral composition. According to the magma fractionation, $TiO_2$, $Al_2O_3$, $Fe_2O_3{^*}$, FeO, $Fe_2O_3$, MnO, MgO, CaO, $Na_2O$ and $P_2O_5$ show positive trend but $K_2O$ indicate negative trend with $SiO_2$ contents. Those are identified as calc-alkaline series in AFM diagram and show the chemical characteristics of the I-type magma through the oxidation tendency of the iron ion and the portion of the alkaline composition. When calculated using the equation of Hollister et al. (1987), the emplacement depths of the Yeongdeok granite range from 8.98 to 17.19 km and average depth was estimated 13.03 km approximately.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.152-162
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• 1988

In recent years, attention has been paid to the ceramic material next to metals and plastics due to its inherent characteristics, i.e., good hardness, resistance to heat and corrosion. Recently, various kinds of ceramic dielectrics have been developed for application in industry. It is of prime importance to know the thermophysical properties for wider use of these new materials. However, no extensive effort has been made for systematic measurement of the properties. In this paper, the dielectric constant of five different kinds of ceramic dielectrics ware measured. We call these samples as MgO.SiO$_{2}$, MgTiO$_{3}$, TiO$_{2}$, CaTiO$_{3}$, and BaTiO$_{3}$. Which are currently in commercial sue. The values of thermal dirrusivities, specific heats, and thermal conductivities of these ceramic dielectrics sere measured as a function of temperature ranging from room temperature to about 1300k.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.255-259
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• 1999

높은 투자율과 낮은 손실특성을 지닌(Mn, Zn)ferrite의 전자기적 특성은 소결공정과 소결분위기에 따라 상당히 다양하게 나타난다. 본 연구에서는(Mn, Zn)ferrite를 소결시킬 때의 승온속도와 냉각속도에 따른 초투자율 특성과 미세구조의 관계에 관하여 고찰하였다. 승온속도의 영향을 고찰하기 위하여 spinel ferrites 생성 및 결정입 성장 거동에 가장 중요한 온도인 800~120$0^{\circ}C$의 범위에서 속도를 변화시켰고, 냉각속도 영향을 살펴보기 위하여 1100~80$0^{\circ}C$ 온도범위를 택하였다. 열처리 온도범위 800~120$0^{\circ}C$에서 승온속도가 증가함에따라 초투자율이 7$^{\circ}C$/min까지는 증가했으나 그 이상의 승온속도에서는 오히려 초투자율이 감소하였다. 또한 1100~80$0^{\circ}C$ 온도범위에선 냉각속도가 증가될수록 초투자율이 감소하는 경향을 나타내었다. 치밀화 및 투자율을 높이기 위하여 첨가된 CaO, SiO2, V2O5의 분포상태를 분석한 결과, 이들 첨가물들은 입자와 입계를 따라 균일하게 분포하는 것으로 나타났다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.82-82
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• 2009

본 연구에서는 Glass ceramic $SiO_2-CaO-Al_2O_3$를 사용하여 적층형 칩 퓨즈를 제조하였다. 퓨즈의 용단 특성 및 IR특성을 개선하기 위하여 기공조제로써 Corn starch 파우더(x=5, 10, 20, 30, 40, 50wt%)를 혼합하여 기공을 형성하게 하였다. 미세구조 관찰 결과 Corn starch 파우더의 함량이 증가함에 따라 기공률이 증가하였다. 또한 전극의 선폭(x=50, 100, 150, $200{\mu}m$)을 변화 시킴으로써 전극의 폭이 커질수록 저항값이 줄어든다는 것을 알 수가 있었다. 기공층 도입을 통하여 적층형 칩 퓨즈의 용단 특성의 개선 및 ARC 억제가 가능하였다.