• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.779-785
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• 2012

The epoxy/micro-and nano-mixed silica composites(EMNC) systems were prepared and the AC insulation breakdown strength was evaluated. Glass transition temperature (Tg) and crosslink density were also measured by dynamic mechanical analyzer(DMA) in order to correlate them with the electrical and mechanical properties, and the effect of silane coupling agent on the electrical properties was also studied. Electrical properties and crosslink density of epoxy/micro-silica composite were noticeably improved by addition of nano-silica and silane coupling agent, and the highest breakdown strength was obtained by addition of 0.5~5 phr of nano-silica and 2.5 phr of silane coupling agent, and the highest tensile and flexural strength were obtained by addition of 2.5 phr of nano-silica.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.570-575
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• 2023

Demand and necessity for eco-friendly offshore wind farms have been increasing. Research on submarine cables is constantly being considered for a reliable and stable power transmission. This study aimed to evaluate the thermal aging characteristic of submarine cables inside the J-tube of offshore wind farms. In this study, a submarine cable was set in three sections: The first is the part exposed to the air above the sea level at high temperature. The second is the section exposed to repeated temperature fluctuation as the sea level rises and falls. The third is the part submerged at low temperature below the sea level. Aged samples were tested by using the method of electrical evaluation to obtain insulation characteristics. The experimental results show that the dielectric breakdown of the sample with temperature fluctuation was 7% lower than the sample with a constant temperature; thereby, demonstrating that the section where the temperature fluctuation occurred in the submarine cables was weaker than the other. The sections of submarine cable with temperature fluctuations are believed as a weak point during operation; therefore, this part should be monitored preferentially.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.117-123
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• 2018

The increase in energy efficiency has became a significantly important issue for building construction and maintenance. The energy efficiency is known to be achieved by using a material with lower thermal conductivity, and the best method is to increase the internal porosity of the material. Typical ways to increase internal porosity within cementitious composite are to use foaming agents or to use reactive powder such as aluminum. However, in this work, hydrogen peroxide was chosen as an alternative material to make lightweight cement mortar. The volume expansion of fresh cement mortar and unit weight, compressive strength and thermal conductivity of 28 day old cement mortar were measured. According to the experimental results, the incorporation of hydrogen peroxide increased internal porosity, and thereby reducing the compressive strength and thermal conductivities of cement mortar. It was found that hydrogen peroxide can be successfully used to produce lightweight mortar for thermal insulation purposes of buildings.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.45-47
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• 2001

The function of the thermal shield(TS) is to eliminate the thermal radiation from the room temperature side to the coil temperature(4.5K) region so as to reduce the thermal load on the He refrigerator. The TS is composed of multilayer insulation(MLI) which is coated very thin aluminum on the insulating material, cryopanel which is cooled by cold gaseous He, and supports which stand the cryopanel and MLI on the room temperature part. The thermal shield for the TF coils and PF coils has been located between the coils and vacuum vessel. The thermal shielding cryopanel is cooled under 80 K by a forced flow of helium gas using cooling pipes on the cryopanel.

• KIEAE Journal
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• v.14 no.4
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• pp.133-138
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• 2014

The present study was carried out to assess the basic material properties and thermal behavior of light-weight foamed concrete panel mixed with PCM (Phase Changing Material). To do so, this study fabricated light-weight foamed concrete (1.0kg/m3) in pre-foaming method and mixed it with PCM micro capsule of 1-dodecanol and melamine to examine its physical and thermal properties. The results confirmed strength reinforcement effect by proper replacement ratio of fly-ash, which is an industrial by-product, and PCM. In addition, it found out that PCM-mixed light-weight foamed concrete had time delay and temperature reduction effect within the range of PCM phase transition according to the rise of outdoor temperature. It was also observed that the insulation performance of PCM-mixed light-weight foamed concrete was more dependent upon thickness than PCM replacement ratio.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.570-574
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• 2010

The main function of conventional insulation materials is only to block the heat transfer and reduce heat loss from the building. On the other hand, thermal storage materials can work as an energy saver by absorbing or emitting heat within a specific temperature range. Thermal storage materials for building can maintain a constant temperature by effectively regulating the cycle of indoor temperature. As a result, we can enhance the performance of a cooling and heating system efficiently. In this study, phase change materials (PCMs) were added as thermal storage materials into gypsum boards which are extensively used for building material and we found out the thermal environmental characteristics. In addition, we checked out some problems when applying the thermal storage materials to buildings. Finally, This study set out to examine the degree of environmental-friendly characteristics of thermal storage building materials by analyzing the amount of TVOC and HCHO contents with the possibility of pollutants emission.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.199-202
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• 1998

Power capacitors are highly reliable equipment due to their completely enclosed configuration. Aging diagnosis system using partial discharge(PD) and acoustic emission(AE) is being highlighted as a research area for degradation of power capacitors. Their dielectric strength can be however reduced due to some stresses such as over-voltage or thermal degradation of the insulation material during their long period of operation. In this paper, it has been developed to express the AE of the EVENT(average amplitude) and HIT(pulse count) according to the source location. And real time measurement of PD signals for aging diagnosis of power capacitors.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1510-1515
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• 2006

A self-priming and photosensitive aqueous-basedevelopable benzocyclobutene (BCB)-based dielectric material curable in air is described. Patterned films have high resolution. Whether cured in nitrogen or in air, the formulation produces a film with optical, electrical, thermal, and mechanical properties desired for many microelectronic applications, such as a planarization layer or insulation layer in display applications. A self-priming, air-curable nonphoto- sensitive BCB material is also described.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.389-394
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• 2019

In this study, a functional inorganic insulation as TiO₂ and inorganic wet fly ash were used to evaluate the physical performance and thermal environment of an exterior finish that can improve the thermal environment of a building. The performance evaluation of the finish was based on the KS F 4715 thin coating material and the thermal environment. When TiO₂ was added, the physical performance was lowered at 10% or more, and the inorganic wet-treated fly ash increased the physical performance by 10%. In the thermal environmental evaluation, the surface temperature reduction effect of the inorganic wet-treated fly ash was low, but when used in combination with TiO₂, it was effective to reduce the surface temperature and the internal temperature. As a result, the optimum combination of TiO₂ and inorganic wet-treated fly ash for thermal environment control was found to be optimal when 5% of each mixture was used.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1166-1172
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• 2018

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.