• Journal of the Society of Naval Architects of Korea
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• v.59 no.4
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• pp.207-213
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• 2022

LNG CCS which is a special type of cargo hold operated at -163℃ for transporting liquefied LNG is composed of a primary barrier, plywood, insulation panel, secondary barrier, and mastic. Currently, glass fiber is used to reinforce polyurethane foam. In this paper, we evaluated the possibility of replacing glass fiber-reinforced polyurethane foam with basalt fiber-reinforced polyurethane foam. We conducted a thermal conductivity test to confirm thermal performance at room temperature. To evaluate the mechanical properties between basalt and glass-fiber-reinforced polyurethane foam which is fiber content of 5 wt% and 10 wt%, tensile and an impact test was performed repeatedly. All of the tests were performed at room temperature and cryogenic temperature(-163℃) in consideration of the temperature gradient in the LNG CCS. As a result of the thermal conductivity test, the insulating performance of glass fiber reinforced polyurethane foam and basalt fiber reinforced polyurethane foam presented similar results. The tensile test results represent that the strength of basalt fiber-reinforced polyurethane foam is superior to glass fiber at room temperature, and there is a clear difference. However, the strength is similar to each other at cryogenic temperatures. In the impact test, the strength of PUR-B5 is the highest, but in common, the strength decreases as the weight ratio of the two fibers increases. In conclusion, basalt fiber-reinforced polyurethane foam has sufficient potential to replace glass fiber-reinforced polyurethane foam.

• Clean Technology
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• v.28 no.4
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• pp.301-308
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• 2022

Since nanoporous silica aerogel was first synthesized in 1931, its potential as an ultra-lightweight superinsulation material has been steadily attracting attention. Silica aerogel is the best thermal insulation material to date. However, the potential applications of this lightweight material have so far been hindered by its inherent fragibility and brittleness arising from its ultra-porous nature. Although the monolithic form of silica aerogel has the best ultra-lightweight superinsulation properties, it cannot be used in this form. Instead it is used in the form of powders, particles, and blankets. However, these forms still have shortcomings. Silica aerogel is most widely applied in the form of a fiber-reinforced aerogel blanket, but this form is likely to generate dust when handled. Although silica aerogel particles have been proven to be non-toxic to humans, dust formation remains a major barrier to the widespread application of silica aerogel blankets. This paper will investigate the unique properties of silica aerogel and determine what fields it can be used in or potentially be used in due to its unique properties. In addition, we will review the important advances in silica aerogel synthesis technology and its commercialization so far, and then consider the problems that exist for its widespread commercialization in the future and how to overcome them.

• Analytical Science and Technology
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• v.18 no.5
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• pp.410-418
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• 2005

PCBs had numerous uses such as hydraulic fluid, heat exchange fluid, sealant, lubricant, and carbonless copy paper. They are most likely found in electric utilities, power stations, industrial facilities, electronic manufacturing plants, petrochemical plants, railroad systems, electric equipment repair facilities, mining sites (active or abandoned), and military camps. Due to its outstanding chemical and thermal stabilities and electrical insulation properties, the commercial and industrial products of PCBs, such as Aroclors, Kaneclors, Clophens, Phenaclors etc., had been widely used as thermal oil and transformer oil from 1930s until the 1970s. The transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. Qualitative estimation of oil extracts as carried out with Aroclor 1242, 1248, 1254, 1260. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. Also, commercial screening kit of 20 ppm and 50 ppm were applied to the transformer oil samples.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.99-104
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• 2006

The Langmuir-Blodgett(LB) technique has attracted considerable interest in the fabrication of electrical and electronic devices. Maxwell displacement current (MDC) measurement has been employed to study the dielectric property of Langmuir-films. MDC flowing across monolayers is analyzed using a rod-like molecular model. A linear relationship between the monolayer compression speed u and the molecular area Am. Compression speed a was about 30, 40, 50mm/min. Langmuir-Blodgett(LB)layers of Arachidic acid deposited by LB method were deposited onto slide glass as Y-type film. The structure of manufactured device is Au/Arachidic acid/Al, the number of accumulated layers are 9$\sim$21. Also, we then examined of the Metal-Insulator-Metal(MIM) device by means of I-V. The I-V characteristics of the device are measured from -3 to +3[V]. The insulation property of a thin film is better as the distance between electrodes is larger.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.309-315
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• 2012

Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were $750^{\circ}C$, $400-500^{\circ}C$, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

• ETRI Journal
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• v.35 no.3
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• pp.425-430
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• 2013

In this paper, we propose a triple-gate trench power MOSFET (TGRMOS) that is made through a modified RESURF stepped oxide (RSO) process, that is, the nitride_RSO process. The electrical characteristics of TGRMOSs, such as the blocking voltage ($BV_{DS}$) and on-state current ($I_{D,MAX}$), are strongly dependent on the gate configuration and its bias condition. In the nitride_RSO process, the thick single insulation layer ($SiO_2$) of a conventional RSO power MOSFET is changed to a multilayered insulator ($SiO_2/SiN_x/TEOS$). The inserted $SiN_x$ layer can create the selective etching of the TEOS layer between the gate oxide and poly-Si layers. After additional oxidation and the poly-Si filling processes, the gates are automatically separated into three parts. Moreover, to confirm the variation in the electrical properties of TGRMOSs, such as $BV_{DS}$ and $I_{D,MAX}$, simulation studies are performed on the function of the gate configurations and their bias conditions. $BV_{DS}$ and $I_{D,MAX}$ are controlled from 87 V to 152 V and from 0.14 mA to 0.24 mA at a 15-V gate voltage. This $I_{D,MAX}$ variation indicates the specific on-resistance modulation.

• 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.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.171-176
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• 2000

The physical and electrical characteristics of MgO and Pt thin-films on it, deposited by reactive sputtering and rf magnetron sputtering, respectively, were analyzed with annealing temperature and time by four-point probe, SEM and XRD. Under annealing conditions of $1000^{\circ}C$ and 2 hr, MgO thin-film had the properties of improving Pt adhesion to $SiO_2$ and insulation without chemical reaction to Pt thin-film, and the sheet resistivity and the resistivity of Pt thin-film deposited on it were $0.1288\;{\Omega}/{\square}$ and $12.88\;{\mu}{\Omega}{\cdot}cm$, respectively. We made Pt resistance pattern on $SiO_2$/Si substrate by lift-off method and fabricated thin-film type Pt-RTD(resistance thermometer device) for micro thermal sensors by Pt-wire, Pt-paste and SOG(spin-on-glass). In the temperature range of $25{\sim}400^{\circ}C$, the TCR value of fabricated Pt-RTD with thickness of $1.0{\mu}m$ was $3927\;ppm/^{\circ}C$ close to the Pt bulk value. Resistance values were varied linearly within the range of measurement temperature.

• Fire Science and Engineering
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• v.18 no.4
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• pp.57-63
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• 2004

We investigated heat properties of connection terminal in residual current protective devices(RCD) according to contact pressure for low voltage appliance. And we analyzed voltage and current waveform and oxide propagation when the poor-contact happened between terminal and wire. When contact pressure between terminal and connection wire was not applied, the heat was generated and an oxide was formed on the surface of the wire. The temperature of the insulation surrounding terminal was ascended sharply by poor-contact, micro-sparks and continuous arc sound happened in interior terminal. When the poor-contact by vibration occurred inner conductor of terminal and wire, an oxide was propagated on contact surface and the temperature was increased at 869℃. Thus, we found that the risk of electrical disaster is high in terminal and connection wire parts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.40-43
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• 2003

전기방전에 대한 shed 재료의 열화내성과 우수한 발수성의 장기간 유지특성은 폴리머 애자의 장기성능에 있어서 가장 중요한 인자들이다. 애자 제조시 무결점 성형성 또한 중요한데 열화내성을 확보하기 위해 다량의 ATH의 첨가가 수반되기 때문에 적절한 process oil의 사용이 불가피하다. 사용하는 오일의 종류와 량에 따라 옥외절연물의 장기성능에 영향을 주는 표면발수성이나 방전내성은 크게 차이가 나는 것으로 밝혀지고 있다. 본 논문에서는 화학적 구조와 정도가 다른 몇 가지 실리콘 fluid들을 실리콘 고무에 처방하여 기본물성과 초고압 옥외절연물의 shed 재료로서 장기성능에 영향을 주는 방전열화내성과 표면발수성의 회복특성을 평가하였다. 실리콘 고무의 무결점 사출성형에 가소도가 중요한데 동일한 무기물 첨가조건에서 유사한 가소도를 갖게 하는데 필요한 량은 fluid들의 종류에 따라서 상당한 차이가 있었다. 특히 PDMS는 점도는 낮지만 분자량이 커서 많은 량이 첨가되어 기계적 특성저하가 크게 일어났다. 코로나 처리후 발수성 회복특성은 fluid들의 분자크기와 반응기의 종류에 따라 상당히 영향을 받았으며 분자가 클수록 초기회복속도는 다소 느려도 최종의 상시발수성은 다소 높게 유지되었으며 2일 이내에 거의 초기 접촉각으로 회복되었다. 내아크성은 무게손실이 적을수록 오차범위도 작은 안정된 특성을 보였으며 fluid들의 종류에 따른 무게손실의 차이는 크지 않았다. 트래킹 방전에 의한 무게 감소는 fluid의 분자가 크면서 페닐기를 가진 fluid들이 첨가된 고무가 우수한 특성을 보였다.