• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
• /
• pp.810-812
• /
• 1988

This paper is to investigate dielectric properties and new fabrication method of Glass-Cloth/Epoxy composite materials. According to the results of this paper, gelling point temperature is affected significantly on the ambient temperature. And Tan${\delta}$ characteristics of Glass-Colth/Epoxy composite materials is also affected significantly on the state of interior void of glass cloth and interface coupling between epoxy resin and glass cloth.

• 한국세라믹학회지
• /
• 제31권9호
• /
• pp.981-988
• /
• 1994

Crystallizable glasses with precipitation of celsian were prepared for the purpose of insulating dielectric layers for the devices such as integrated circuit substrates. Crystallization behavior of these glasses were studied by DTA, SEM, XRD analysis and by the measurement of dielectric properties. The base composition of the glass-ceramic consists in weight percent of 30% SiO2, 10% Al2O3, 26% BaO, 10% CaO, 10% ZnO, 8%TiO2 and 6% B2O3. 2-6 wt% Y2O3 were selected as the nucleating agent to promote monoclinic celsian formation. As a result, in barium-rich glasses containing 4~6wt% Y2O3 , monoclinic celsian was developed as major crystalline phase in the temperature range of 850~90$0^{\circ}C$. Also, the dielectric constant and quality factor of these glass-ceramics were about 9 and more than 1000, respectively.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
• /
• pp.34-34
• /
• 2010

This paper describes effect of the bending deformation of high voltage composite bushing with winding tension. The composite bushing can be formed, by adding silicone rubber sheds to a tube of composite materials. The FRP tube is internal insulating part of a composite bushing and is designed to ensure the mechanical characteristics. Generally the properties of FRP tube can be influenced by the winding angle, wall thickness and winding tension. As winding tension is increased glass contents was increased in the range of 70.4~76.6%. In the bending test, winding tension is increased residual deflection was decreased in the range of 14.0~12.2 mm.

• 공업화학
• /
• 제16권6호
• /
• pp.760-767
• /
• 2005

소다석회유리 조성의 폐 유리를 발포유리의 원료로 활용하기 위하여 가수분해에 의해 수화된 폐유리를 발포시켜 발포유리의 제조를 시도하였다. 소다석회 유리 조성의 수화된 폐유리들은 판유리, 병유리 또는 그 색깔에 관계없이 발포조제로서 흑연의 량은 수화된 폐유리의 중량에 대한 중량비로 0.003, 소성온도 $925^{\circ}C$, 소성발포시간 10~20 min, 원료유리의 입도는 수화되기전의 유리의 입도로서 -325 mesh가 최적의 발포유리제조의 조건이었다. 상기의 조건하에 혼합된 폐유리의 수화유리를 발포시킨 결과 밀도 $0.2g/cm^3$이고 열전도도는 $0.05kcal/mh^{\circ}C$이 발포유리를 제조하였다.

• Transactions on Electrical and Electronic Materials
• /
• 제18권6호
• /
• pp.338-340
• /
• 2017

Breakdown of solid insulating materials in power equipment could result in undesired outages and replacements, and may be due to an increase in electric stress on the material. Therefore, it is necessary to conduct a proper diagnosis of materials before their practical use. In this work, a few inherent properties of different non-cellulosic insulating materials, such as Nomex, Teflon, laminated Nomex, glass bonded mica, epoxy resin bonded mica paper, and epoxy resin bonded fiberglass, have been evaluated by performing non-destructive dielectric diagnostic measurements, and an attempt has been made to correlate these basic parameters to evaluate the breakdown strength (BDS). An equation has been proposed using a basic theory which defines the correlation between the BDS, dielectric constant, dissipation factor, sample thickness, and volume resistivity. The results obtained from the equation are also compared with the experimental values. The suggested equation will be helpful to predict the BDS of any non-cellulosic material without experimentation in the laboratory.

• 한국초전도ㆍ저온공학회논문지
• /
• 제13권4호
• /
• pp.10-13
• /
• 2011

For the operation of high temperature superconducting (HTS) power equipments, it is necessary to develop insulating materials and high voltage (HV) insulation technology at cryogenic temperature of bushing. In this paper, the surface flashover characteristics of various insulating materials in $LN_2$ are studied. These results are studied at both AC and impulse voltage under a non-uniform field. The negative impulse breakdown voltage of GFRP is slightly higher than the positive impulse breakdown voltage. The use of glass fiber reinforced plastic (GFRP) and polytetrafluoroethylene (PTFE, Teflon) as insulation body for HTS bushing should be much desirable. Especially, GFRP is excellent material not only surface flashover characteristics but also mechanical characteristics at cryogenic temperature. The surface flashover is most serious problem for the shed design in $LN_2$ and operation of superconducting equipment.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2003년도 추계학술대회 논문집
• /
• pp.226-229
• /
• 2003

Following the successful development of practical high temperature superconducting (HTS) wires, there has been renewed activity in the development of superconducting power equipments. HTS equipments must be operated in the coolant, such as liquid nitrogen (L$N_2$) or cooled by cooler, such as GM-cryocooler to maintain the temperature below critical temperature. In this paper, dielectric strength of some insulating materials, such as epoxy, teflon, and glass fiber reinforced plastic (GFRP) in L$N_2$was measured. Surface breakdown voltage of GFRP which is basic property in design of HTS solenoid coil was measured. Epoxy is a goof insulating material but it is fragile at cryogenic temperature. The multi-layer insulating method of current lead is suggested to compensate this fragile property. It consists of teflon tape layer and epoxy layer fixed with texture. Based on these measurements, the 6.6㎸ class HTS magnet for DC reactor type high-T$_{c}$ superconducting fault current limiter (SFCL) was successfully fabricated and tested.d.

• 센서학회지
• /
• 제9권1호
• /
• pp.83-89
• /
• 2000

TFELD의 절연층으로 사용하기 위해 ITO 유리위에 BST박막을 rf 마그네트론 스퍼터링법으로 증착시켰다. $O_2/(Ar+O_2)$의 혼합비는 10%, 기판온도는 상온에서 $500^{\circ}C$까지 변화를 주었고, 분위기압은 5 mTorr에서 30 mTorr까지 변화시켰다. 다양한 증착조건에서 성장된 BST박막의 전기적, 광학적, 구조적 및 화학량론적인 특성을 조사하였다. BST박막성장의 최적조건은 기판온도 $400^{\circ}C$, 분위기압 30 mTorr에서 구할 수 있었다. 주파수 1 kHz에서 비유전율은 254였고, 누설전류밀도는 5 MV/cm의 전계에서 $3.3{\times}10^{-7}\;A/cm^2$이하로 나타났으며, 가시광영역에서 광투과율은 82%였다.

• 한국재료학회지
• /
• 제22권10호
• /
• pp.531-538
• /
• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.

• Restorative Dentistry and Endodontics
• /
• 제26권5호
• /
• pp.387-392
• /
• 2001

When cavity floor is near the pulp, polymerization of light-activated restorations results in temperature increase. This temperature increase cause by both the exothermic reaction process and the energy absorbed during irradiation. Therefore instating base is required. Most frequently used insulating base is glass ionmer. The purpose of this study was to evaluate intrapulpal temperature changes of glass ionomer according to various curing intensity and curing time. Caries and restoration-free mandibular molars extracted within three months were prepared Class I cavity of 3$\times$6mm with high speed handpiece. 1mm depth of dentin was evaluated with micrometer in mesial and distal pulp horns. Pulp chambers were filled with 37.0$\pm$0.1$^{\circ}C$ water to CEJ. Chromium-alumina thermocouple was placed in pulp horn for evaluating of temperature changes. glass ionomer material was placed in 2mm. total curing time was 40s: continuous 40s, intermittent 20s, intermittent 10s. Glass ionomer material was cured with 300mW/$\textrm{cm}^2$, 550mW/$\textrm{cm}^2$ light curing unit. The results were as follows : 1. Temperature in pulp increased as curing unit power is increased. 2. Temperature in pulp more increased continuous emission than intermittent emission.