• Transactions on Electrical and Electronic Materials
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• 제7권6호
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• pp.319-323
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• 2006

The problem of the partial discharge (PD) extinction is investigated. The transient process takes place in a small spherical inclusion which is located in the dielectric. Both the losses caused by polarization and ohmic losses as the dielectric parameters are taken into account. From the inclusion standpoint the dielectric is considered as an active two-pole element (equivalent generator) and inclusion represents by own current-voltage curve. PD extinction voltage was shown to depend on the polarization loss tangent.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.68-68
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• 2010

Electroluminescence (EL) characteristics of green-emission ZnS:Cu,Cl-based ac-type inorganic powder electroluminescent structures were examined by inserting carbon nanotubes (CNTs) into or next to the dielectric layer. For the top-emission type EL structure, where the luminescent light was emitted from the top of the structure, was fabricated by assembling in order, a top electrode, an emitting layer, a dielectric layer, and a bottom electrode from the top. $BaTiO_3$ powder mixed with CNTs was used as a dielectric layer or CNTs were deposited between the bottom electrode and $BaTiO_3$ dielectric layer in order to improve the role of the dielectric layer in the structure. Luminance of an EL structure with CNTs inclusion was greatly enhanced possibly due to the high dielectric constant in the dielectric layer of $BaTiO_3$/CNTs, which is one of hot research topics utilizing nano-objects for intensifying dielectric constant and reducing dielectric loss at the same time. A variation on the CNTs themselves and their inclusion methods in the dielectric layer has been exhorted, and the underlying mechanism for the role of CNTs in the EL structure will be explained in the poster. In order to extend the flexibility of EL devices, EL devices were fabricated on the paper substrate and their performance was compared other EL devices on the plastic-based substrate.

• 한국세라믹학회지
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• 제30권2호
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• pp.101-106
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• 1993

Effects of CaO on microwave dielectric properties of (Ba, Pb)O-Nd2O3-TiO2 ceramic ystem were investigated. As the content of CaO increases, the sintered bulk density decreases due to the decrease of sinterability. However, with increasing the sintering tmperature, the relative dielectric constants increases. This has been attributed on the formation of the 2nd phase inclusion, TiO2(rutile). The Q values increase due to the compensation effect of Ca ions up to 1 wt%, and then decrease due to the interfacial relaxation effects. The temperature coefficient of resonance frequency increases to a positive direction with increasing the amounts of CaO.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.124-125
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• 2006

Multilayer ceramic capacitor (MLCC) miniaturization has increased the demand for superfine $BaTiO_3$ powder due to its thin dielectric layer. Hydrothermally synthesized $BaTiO_3$ powder a pseudo-cubic phase resulting in poor dielectric properties due to size effect and hydroxyl ion inclusion in the $BaTiO_3$ lattice. We attempted a superfine (lower than 100 nm) highly tetragonal $BaTiO_3$ powder via a solvothermal method without precipitating agent. The lattice parameters and the relative amounts of tetragonal and cubic phases were determined using Rietveld refinement.

• Journal of Information Display
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• 제2권3호
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• pp.32-38
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• 2001

The most important parameter for TV application of LCD is a fast switching time for the display of moving image. To achieve faster switching time, the novel LC single materials with large dielectric anisotropies ($16{\sim}20$), high clearing temperatures ($195.5{\sim}237.4^{\circ}C$), broad nematic ranges (up to 169.9 $^{\circ}C$) and high birefringence ($0.254{\sim}0.2200$) were developed. KUR-series LC mixtures blended these single materials having significantly higher clearing temperatures and dielectric anisotropy values compared with conventional LC mixture. Especially, their clearing temperatures are $10{\sim}30^{\circ}C$ higher than their host mixture. These LC mixtures showing about lOms of high-speed switching time in Tv/Monitor of TFT LCD, is short enough to be addressed in a single time frame of 60Hz (16.7 ms). The threshold voltage $V_{th}$ was low enough to operate at a driving voltage of 5 V. The VHR values were found to be high enough for TFT-LCD in wide temperature range. Our novel LC mixtures are suitable materials for the inclusion in to LC mixtures for TV application of TN-LCD

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.267-272
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• 2012

Considering the properties of the carbon nano tubes (CNT), their inclusion into the polymer matrix vastly increases the properties of the resultant composite. However, this is not the case due to the poor interfacial adhesion of the CNT and the polymer matrix. The present approach focuses on increasing the interaction between the polymer matrix and the CNT through the chemical modification of the CNT resulting in allyl ester functionalized carbon nanotubes (ACNT) and silane functionalized carbon nano tubes (SCNT) which are capable of reacting with the polymer matrix during the curing reaction. The addition of ACNT/SCNT into unsaturated polyester resin (UPR) resulted in the improvement of the electrical properties of resulted nanocomposites in comparison to the CNT. The surface resistivity, volume resistivity, dielectric strength, dry arc resistivity, and the comparative tracking index of the nanocomposites were significantly improved in comparison to CNT. The chemical modification of CNT was confirmed via spectroscopy.

• 한국세라믹학회지
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• 제20권2호
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• pp.153-160
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• 1983

This study was carried out to research the change of mineral phases and the characteristics(apparent specific gra-vity water absorption firing shrinkage modulus of rupture thermal expansion and specific dielectric constant) of the sintered bodies manufactured by kaolin and limestone. Samples were composed of the same theoretical composition as it of anorthite and fired up to 145$0^{\circ}C$ Investigated the change and micro-structure of the mineral phases by XRD and SEM the characterisdtics of the sintered bodies by TMA Automatic Capacitance Bridge and etc. The results were as follow. 1. Reactions of sintering are occurred between 860-95$0^{\circ}C$ and 1200-138$0^{\circ}C$ and state of bloating is occurred at 1410-145$0^{\circ}C$ 2. For the inclusion of feldspar and its fine particles of materials the temperature of producing and collapsing is decreased. 3. Pseudo-wollastonite and gehlenite are formed about 95$0^{\circ}C$ 4. At 114$0^{\circ}C$ anorthite are begin to forming and increase continuously to 138$0^{\circ}C$. Above 141$0^{\circ}C$ content of anorthite are decreased. 5. The variations of bending strength with sintering temperature reflect similar trend of sintered contraction and in-crease continuously from 120$0^{\circ}C$. At 145$0^{\circ}C$ reached about 680kg/cm2. 6. Specific dielectric constant$($\varepsilon$_s)$ of specimen sintered at 141$0^{\circ}C$ is 7.12 and that value is most favorable.

• KSBB Journal
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• 제21권2호
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• pp.151-156
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• 2006

본 연구에서는 용매증발법을 이용하여 대표적 생리활성 물질인 Vitamin-C의 불안정성을 극복하기 위하여 HP-${\beta}$-CD와의 포접복합체를 제조하고 수용액상에서의 안정성을 분석하였다. Vitamin-C와 HP-${\beta}$-CD 간의 몰비를 변화시켜 제조한 포접복합체의 안정성 시험 결과 포접 몰비는 1:1로 추정되며, 포접복합체 제조에 사용된 용매의 유전상수가 커질수록 Vitamin-C의 안정성이 향상되는 것을 확인할 수 있었다. 3차 증류수를 용매로 하여 제조된 포접복합체의 경우 순수한 Vitamin-C보다 Vitamin-C의 겉보기 1차 분해속도 상수 값이 감소하는 것을 확인하였는데 이는 결과적으로 Vitamin-C의 안정성이 향상되었음을 의미한다. 따라서 HP-${\beta}$-CD와의 포접복합체 형성은 Vitamin-C의 안정성을 향상시켜 생체이용률을 향상시킬 수 있음을 확인하였으며 불안정한 여러 생리활성물질에 적용할 수 있을 것으로 기대된다.

• 전기학회논문지P
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• 제57권2호
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• pp.140-145
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• 2008

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, ${\beta}-PVF_2$) organic thin films using the vapor deposition method. Vapor deposition was performed under the following conditions: the temperature of evaporator, the applied electric field, and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm, and $2.0{\times}10^{-5}\;Torr$, respectively. The molecular structure of the evaporated organic thin films were evaluated by a FT-IR. The results showed that the characteristic absorption peaks of $\beta$-form crystal increase from 72% to 95.5% with an increase in the substrate temperature. In the analysis of the electric characteristics, the abnormal increases in the relative dielectric constant and the dielectric loss factor in the regions of low frequency and high temperature are known to be caused by inclusion of impurity carriers in the PVDF organic thin films. In order to analyze quantitatively the abnormalities in the conductivity mechanism caused by ionic impurities, the product of the ion density and the mobility that affect the electrical property in polymeric insulators is analyzed. In the case of a specimen produced by varying the substrate temperature from $30^{\circ}C$ to $105^{\circ}C$, the product of mobility and the ion density decreased from $4.626{\times}10^8$ to $8.47{\times}10^7/V{\cdot}cm{\cdot}s$. This result suggests that the higher the substrate temperature is maintained, the better excluded the impurities are, and the more electrically stable material can be obtained.