• Title, Summary, Keyword: thermal property

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Improving Thermal Resisting Property of PZT Ceramics by Thermal Aging (열에이징에 의한 PZT세라믹스의 내열특성 개선)

  • Lee, Gae-Myung;Kim, Byung-Hyo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.1
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    • pp.43-49
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    • 2005
  • Temperature stabilities of resonance frequencies of the substrates are very important in piezoelectric ceramics oscillators and fitters. In this study, it was investigated thermal resisting property of the length-extensional vibration mode of PZT ceramics. The mode can be utilized in fabricating ultra-small 55 kHz IF devices. We fabricated the ceramic specimens with x = 0.51, 0.52, 0.53, 0.54, and 0.55 in the Pb(Zr$\sub$x/Ti$\sub$1-x/)O$_3$ system. And their resonance frequencies were measured before 1st thermal aging, after 1st and 2nd thermal aging. In order to investigate the influence of thermal aging on thermal resisting properties, thermally aged specimens were once mote thermally aged. Before 1st thermal aging, the specimens of the compositions with morphotropic phase, x = 0.53 and rhombohedral phase, x = 0.54 have weak thermal resisting property of resonance frequency, while tetragonal phase, x = 0.51 has robust thermal resisting property of resonance frequency. 1st thermal aging improved thermal resisting property of resonance frequency in all specimens.

Development of the Soil Thermal Property and Temperature Measurement System for the Real-time Ampacity Estimation of Underground Power Cables (실시간 지중 전력케이블 용량 평가를 위한 토양 열 특성 및 온도 측정 시스템 개발)

  • Jeong, Seong-Hwan;Kim, Dae-Kyeong;Choi, Sang-Bong
    • Proceedings of the KIEE Conference
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    • pp.22-24
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    • 2002
  • This paper introduces the real-time soil thermal property analyzer and temperature measuring system which is combined with radio telecommunication technique. To measure the thermal parameters in real-time, the radio telecommunication technique are used the personal communication service (PCS) which is in the world-wide serviced commercially firstly by CDMA. The thermal property analyzer has an ability of measuring thermal resistivity, thermal diffusivity and thermal stability. To estimate the soil thermal properties, the curve fitting algorithm by means of the least square method are used. TCP/IP protocol and MTM are used to install the real-time soil thermal property and temperature measurement system at multiple locations along routes of the underground power cables and to reduce the cost of telecommunication.

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Thermal Shock Resistance Property of TaC Added Ti(C,N)-Ni Cermets (TaC 첨가 Ti(C,N)-Ni 서멧의 내열충격 특성)

  • Shin, Soon-Gi
    • Korean Journal of Materials Research
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    • v.24 no.10
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    • pp.526-531
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    • 2014
  • Thermal shock resistance property has recently been considered to be one of the most important basic properties, in the same way that the transverse-rupture property is important for sintered hard materials such as ceramics, cemented carbides, and cermets. Attempts were made to evaluate the thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermets using the infrared radiation heating method. The method uses a thin circular disk that is heated by infrared rays in the central area with a constant heat flux. The technique makes it possible to evaluate the thermal shock strength (Tss) and thermal shock fracture toughness (Tsf) directly from the electric powder charge and the time of fracture, despite the fact that Tss and Tsf consist of the thermal properties of the material tested. Tsf can be measured for a specimen with an edge notch, while Tss cannot be measured for specimens without such a notch. It was thought, however, that Tsf might depend on the radius of curvature of the edge notch. Using the Tsf data, Tss was calculated using a consideration of the stress concentration. The thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermet increased with increases in the content of nitrogen and Ni. As a result, it was considered that Tss could be applied to an evaluation of the thermal shock resistance of cermets.

Study of Thermal Conductivity and Mechanical Property of Elastic Epoxy (탄성형 에폭시의 열전도율 및 기계적 특성에 대한 연구)

  • Lee, Kwan-Woo;Lee, Kyoung-Yong;Choi, Yong-Sung;Park, Bok-Ki;Park, Dae-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.319-322
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    • 2004
  • In this paper, we studied on the thermal conductivity and a mechanical property of the elastic epoxy. According to industrial development, insulation materials have various properties. They are solid, liquid, gas state, there are various type. Epoxy, a kind of insulation material, demand of not only high hardness but also elastic property. When the electric current flows into the conductor and the place where the heat occurs, this heat becomes the cause which shortens the life of the electrical appliance. Therefore, for the heat occurred transmit quickly, thermal conductivity of the insulation material is highly demanded. We studied on the thermal conductivity of elastic epoxy on the high voltage. In this result, thermal conductivity confirmed that it followed thermal property of mixed epoxy and addictives. Hardness is decreased when addictives increased.

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Effect of enzyme treatment on the DSC and TGA behavior of silkworm powder

  • Jo, You-Young;Bae, Sung Min;Kim, HyunBok;Lee, Kwang Gill;Kweon, HaeYong
    • International Journal of Industrial Entomology
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    • v.37 no.1
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    • pp.29-32
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    • 2018
  • Silkworm powder's thermal property is an important factor for its storage and marketing. This study examined the effect of edible enzyme on the thermal property of silkworm powder using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Results of the TGA showed that regardless of the enzyme treatment, the weight loss patterns of silkworm powders exhibited 3 step thermal property deterioration at approximately $80^{\circ}C$, $280^{\circ}C$, and $480^{\circ}C$ due to water evaporation and thermal degradation. This is similar with the DSC which also resulted in all samples two endothermic peaks attributed also to water evaporation and thermal degradation. These results indicated that the use of enzyme such as protease and cellulase might not affect significantly the thermal properties of silkworm powder.

The simultaneous measurement for thermal properties of liquids using transient probe method (과도탐침법을 이용한 액체의 열물성 동시측정)

  • Bae, Sin-Cheol;Kim, Myeong-Yun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.2
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    • pp.303-315
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    • 1997
  • The theoretical model for the transient probe method is the modified Jaeger model which is used perfect line source theory. The transient probe technique has been developed for the simultaneous determination of thermal conductivity, diffusivity and volumetric heat capacity of liquids. The Levenberg-Marquardt iteration method is adapted to obtain thermal property within nonlinear range. Experimental results of liquids were found to agree well with recommended thermal property data.

Mechanical Property, Thermal Conductivity, Rebound Resilience and Thermal Property of Chloro Isobutylene Isoprene Rubber/Ethylene Propylene Diene Monomer Blend

  • Hwang, Young-Bea;Lee, Won-Ki;Park, Chan Young
    • Elastomers and Composites
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    • v.53 no.2
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    • pp.80-85
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    • 2018
  • Chloro isobutylene isoprene rubber (CIIR) and ethylene propylene diene monomer (EPDM) compounded with other formulation chemicals, depending on the polymer blend, were prepared by mechanical mixing. After manufacturing the rubber vulcanizate by compression molding with a hot press, the mechanical and thermal properties including thermal conductivity, rebound resilience of the CIIR/EPDM blends were measured. As the EPDM rubber content increased, hardness and tension set showed a tendency to increase. Pure CIIR exhibited the lowest tensile strength; however, tensile strength increased with loading of EPDM rubber. On the other hand, in CIIR rubber, which is usually a low-rebound elastomer owing to a high damping effect, rebound resilience exhibited an increasing trend as the content of EPDM rubber increased. As the EPDM rubber content increased, thermal stability was improved due to reduction of decomposition rate in the rubber region of the blend vulcanizate.

Effect of Welding Thermal Cycle on Microstructure and Pitting Corrosion Property of Multi-pass Weldment of Super-duplex Stainless Steel (슈퍼 듀플렉스 스테인리스강 다층용접부의 미세조직 및 공식(Pitting Corrosion)에 미치는 용접열사이클의 영향)

  • Nam, Seong-Kil;Park, Se-Jin;Na, Hye-Sung;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.28 no.4
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    • pp.18-25
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    • 2010
  • Super-duplex stainless steels (SDSS) have a good balance of mechanical property and corrosion resistance when they consist of approximately equal amount of austenite and ferrite. The SDSS needs to avoid the detrimental phases such as sigma(${\sigma}$), chi(${\chi}$), secondary austenite(${\gamma}2$), chromium carbide & nitride and to maintain the ratio of ferrite & austenite phase as well known. However, the effects of the subsequent weld thermal cycle were seldom experimentally studied on the micro-structural variation of weldment & pitting corrosion property. Therefore, the present study investigated the effect of the subsequent thermal cycle on the change of weld microstructure and pitting corrosion property at $40^{\circ}C$. The thermal history of root side was measured experimentally and the change of microstructure of weld root & the weight loss by pitting corrosion test were observed as a function of the thermal cycle of each weld layer. The ferrite contents of root weld were reduced with the subsequent weld thermal cycles. The pitting corrosion was occurred in the weld root region in case of the all pitted specimen & in the middle weld layer in some cases. And the weight loss by pitting corrosion was increased in proportional to the time exposed at high temperature of the root weld and also by the decrease of ferrite content. The subsequent weld thermal cycles destroy the phase balance of ferrite & austenite at the root weld. Conclusively, It is thought that as the more subsequent welds were added, the more the phase balance of ferrite & austenite was deviated from equality, therefore the pitting corrosion property was deteriorated by galvanic effect of the two phases and the increase of 2nd phases & grain boundary energy.

Effect of Electron Beam Irradiation on the Interfacial and Thermal Properties of Henequen/Phenolic Biocomposites

  • Pang, Yansong;Yoon, Sung Bong;Seo, Jeong Min;Han, Seong Ok;Cho, Donghwan
    • Journal of Adhesion and Interface
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    • v.6 no.4
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    • pp.12-17
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    • 2005
  • Natural fiber/phenolic biocomposites with chopped henequen fibers treated at various levels of electron beam irradiation (EBI) were made by means of a matched-die compression molding method. The interfacial property was explored in terms of interfacial shear strength measured by a single fiber microbonding test. The thermal properties were studied in terms of storage modulus, tan ${\delta}$, thermal expansion and thermal stability measured by dynamic mechanical analysis, thermomechanical analysis and thermogravimetric analysis, respectively. The result showed that the interfacial and thermal properties depend on the treatment level of EBI done to the henequen fiber surfaces. The present result also demonstrates that 10 kGy EBI is most preferable to physically modify the henequen fiber surfaces and then to improve the interfacial property of the biocomposite, supporting earlier results studied with henequen/poly (butylene succinate) and henequen/unsaturated polyester biocomposites.

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