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Jeong D.-Y.,Inha University | Lee S.-I.,Pennsylvania State University | Lee H.-Y.,Myongji University | Kim M.-K.,SAMWHA CAPACITOR Co. | Yoon J.-R.,SAMWHA CAPACITOR Co.
Japanese Journal of Applied Physics | Year: 2013

The influence of glass power morphology on the electrical and microstructural properties of BaTiO3-based multilayer ceramic capacitors (MLCCs) was investigated to enhance the reliability of MLCCs. For a sintering additive, glass particles of different sizes and shapes were prepared by jetmilling and RF plasma treatment. Plasma treatment decreased the glass particle size and transformed the irregular shape of glass particles into homogeneous spherical shapes. It was found that MLCCs sintered with plasma-treated glass powder have a more homogeneous microstructure, a clear core-shell structure, a more stable capacitance against voltage and temperature changes, and a higher degradation resistance. It is inferred that nanosized spherical glass powder prepared by plasma treatment helps so-called magic dopants. such as rare-earth elements to be distributed homogeneously around the BaTiO3 particles. © 2013 The Japan Society of Applied Physics. Source


Yoon J.R.,SAMWHA CAPACITOR Co. | Shin D.S.,SAMWHA CAPACITOR Co. | Jeong D.Y.,Inha University | Lee H.Y.,Korea University
Transactions on Electrical and Electronic Materials | Year: 2012

BaTiO 3 based multilayer ceramic capacitors with Ni electrodes can be explained as 2-2 composites with different thermal expansion coefficient and sintering behaviors. To achieve the high capacitance and reliability of MLCCs, a homogenous Ni electrode configuration with high connectivity is required. We controlled the heating rates during sintering to achieve densification by suppressing grain growth. Experimental results revealed that a large heating rate gave high connectivity of Ni electrode, high capacitance, small dissipation factor, high breakdown voltage, and high reliability of MLCC chips. © 2012 KIEEME. All rights reserved. Source


Lee Y.J.,Seoul National University | Jung J.C.,Seoul National University | Park S.,Seoul National University | Seo J.G.,Seoul National University | And 4 more authors.
Current Applied Physics | Year: 2010

Carbon aerogel was prepared by polycondensation of resorcinol and formaldehyde using sodium carbonate as a catalyst with a resorcinol to catalyst ratio of 500. Co-doped carbon aerogels were then prepared by an impregnation method with a variation of cobalt content (1, 3, 5, 7, 10, and 15 wt.%), and their performance for supercapacitor electrode was investigated by measurement of specific capacitance in 1 M H2SO4 electrolyte at a scan rate of 10 mV/s. Among the samples prepared, 7 wt.% Co-doped carbon aerogel showed the highest capacitance (100 F/g) and stable cyclability. The enhanced capacitance of Co-doped carbon aerogel was attributed to the faradaic redox reactions of cobalt oxide. On the basis of this result, 7 wt.% Cu-, Fe-, Mn-, and Zn-doped carbon aerogels were also prepared by an impregnation method for use as a supercapacitor electrode. Among the metal-doped carbon aerogels, Mn-doped carbon aerogel showed the highest capacitance (107 F/g) while Cu- and Fe-doped carbon aerogels exhibited the most stable cyclability. © 2009 Elsevier B.V. All rights reserved. Source


Lee Y.J.,Seoul National University | Jung J.C.,Seoul National University | Yi J.,Seoul National University | Baeck S.-H.,Inha University | And 2 more authors.
Current Applied Physics | Year: 2010

Carbon aerogels were prepared by polycondensation of resorcinol with formaldehyde using sodium carbonate as a catalyst in ambient conditions, and they were used as an electrode of electrical double-layer capacitor. The effect of resorcinol to catalyst ratio (R/C ratio) on volume shrinkage, BET surface area, and electrochemical property of carbon aerogels was investigated by changing R/C ratio from 50 to 2000. In order to minimize volume shrinkage, solvent exchange was performed with acetone at 50 °C for 1 day. Volume shrinkage was <2% after 2-day gelation in the absence of CO2 supercritical drying. BET surface area was strongly dependent on R/C ratio. Carbon aerogel prepared at R/C ratio of 500 showed the highest BET surface area (706 m2/g) with average pore diameter of 10.9 nm. Electrochemical property of carbon aerogels as an electrode of electrical double-layer capacitor was investigated by cyclic voltammetry measurement. Specific capacitance of carbon aerogel prepared at R/C ratio of 500 was found to be 81 F/g in 1 M H2SO4 electrolyte at the scan rate of 10 mV/s. © 2009 Elsevier B.V. All rights reserved. Source


Lee Y.J.,Seoul National University | Jung J.C.,Myongji University | Park S.,Seoul National University | Seo J.G.,Seoul National University | And 4 more authors.
Korean Journal of Chemical Engineering | Year: 2011

Carbon aerogels were prepared by polycondensation of resorcinol with formaldehyde in ambient conditions. The effect of resorcinol-to-catalyst ratio (R/C ratio) on volume shrinkage, BET surface area, and electrochemical property was investigated by changing R/C ratio from 50 to 2000. Carbon aerogel prepared at R/C ratio of 500 showed less than 2% of volume shrinkage and the highest BET surface area (706 m2/g). Specific capacitance of carbon aerogel prepared at R/C ratio of 500 was found to be 81 F/g in 1M H2SO4 electrolyte. Cobalt-doped carbon aerogels were then prepared by an impregnation method with a variation of cobalt content, and their performance was investigated. Among the samples prepared, 7 wt% cobalt-doped carbon aerogel showed the highest capacitance (100 F/g) and the most stable cyclability. The enhanced capacitance of cobalt-doped carbon aerogel was attributed to the faradaic redox reactions of cobalt oxide. © 2010 Korean Institute of Chemical Engineers, Seoul, Korea. Source

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