• Title/Summary/Keyword: CTE

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Optical Properties according to BaO Addition for BaO-GeO2-La2O3-ZnO System (BaO-GeO2-La2O3-ZnO 계에 있어서 BaO 첨가량 변화에 따른 광학 특성)

  • Cho, Jaeyoung;Kim, Jinho;Kim, Sae-Hoon;Lee, Mijai
    • Korean Journal of Materials Research
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    • v.32 no.9
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    • pp.379-383
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    • 2022
  • In this study, Barium Germanium glasses were prepared with a composition of xBaO-(72-x)GeO2-8La2O3-20ZnO where x = 16.0, 18.0, 20.0, 22.0 and 24.0 mol% respectively. Their physical and optical properties, such as refractiveness index, glass transition temperature (Tg), softening temperature (Ts), transmittance and Knoop hardness were studied. The results showed that refractive index, Tg, Ts and coefficient of thermal expansion (CTE) increased with increasing BaO concentration. The refractive index of all the prepared samples was observed between 1.7811 to 1.7881. The Abbe number was calculated by formula using nd (589.3 nm), nf (656.3 nm) and nc (486.1 nm) and observed to be between 38 to 40. The Abbe number of the prepared sample was similar to that of BaO and GeO2. The transmittance of the prepared glasses was observed to be between 80 ~ 82 % throughout the range from 200 nm to 800 nm. Knoop hardness divided into seven steps were measured 5 class (≥ 450 ~ < 550) of all prepared samples.

Development of a Thermoplastic Composite Parabolic Antenna Reflector using Automated Fiber Placement Method (자동섬유적층법을 이용한 열가소성 복합재료 접시형 안테나 반사판 개발)

  • Kim, Jin-Bong;Kim, Tae-Wook
    • Composites Research
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    • v.19 no.1
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    • pp.15-21
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    • 2006
  • It is very difficult to make complex 3 dimensional curved-shape composite laminates using the advanced unidirectional composite prepregs. This study shows development process of subscale composite parabolic antenna reflector using unidirectional AS4/PEEK prepreg tapes. The AS4/PEEK thermoplastic composite materials are known to have good thermal and chemical stabilities in addition to their high specific strength and modulus. Various lamination methods were investigated through finite element analyses to make up the laminate design of the reflector. The automated fiber placement method was used to fabricate the reflector. The thermal expansion test using full-bridge strain gage circuits was done to verity the performance of the composite product.

Effect of CNTs on Electrical Properties and Thermal Expansion of Semi-conductive Compounds for EHV Power Cables

  • Jae-Gyu Han;Jae-Shik Lee;Dong-Hak Kim
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.6
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    • pp.603-608
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    • 2023
  • Carbon black with high purity and excellent conductivity is used as a conductive filler in the semiconductive compound for EHV (Extra High Voltage) power cables of 345 kV or higher. When carbon black and CNT (carbon nanotube) are applied together as a conductive filler of a semiconductive compound, stable electrical properties of the semiconductive compound can be maintained even though the amount of conductive filler is significantly reduced. In EHV power cables, since the semi-conductive layer is close to the conductor, stable electrical characteristics are required even under high-temperature conditions caused by heat generated from the conductor. In this study, the theoretical principle that a semiconductive compound applied with carbon black and CNT can maintain excellent electrical properties even under high-temperature conditions was studied. Basically, the conductive fillers dispersed in the matrix form an electrical network. The base polymer and the matrix of the composite, expands by heat under high temperature conditions. Because of this, the electrical network connected by the conductive fillers is weakened. In particular, since the conductive filler has high thermal conductivity, the semiconductive compound causes more thermal expansion. Therefore, the effect of CNT as a conductive filler on the thermal conductivity, thermal expansion coefficient, and volume resistivity of the semiconductive compound was studied. From this result, thermal expansion and composition of the electrical network under high temperature conditions are explained.

A Study on the Thermo-mechanical Characteristics and Adhesion Reliability of Anisotropic Conductive Films Depend on the Curing Methods of Epoxy Resins (에폭시 레진의 경화방법에 따른 이방성 전도필름의 접합신뢰성 및 열적기계적 특성 변화)

  • Gil, Man-Seok;Seo, Kyoung-Won;Kim, Jae-Han;Lee, Jong-Won;Jang, Eun-Hee;Jeong, Do-Yeon;Kim, Su-Ja;Kim, Jeong-Soo
    • Polymer(Korea)
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    • v.34 no.3
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    • pp.191-197
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    • 2010
  • To improve the curing method of anisotropic conductive film (ACF) at low temperature, it was studied to replace the thermal latent curing agent of imidazole compounds by the curing agent of cationically initiating type. Thermo-mechanical properties such as glass transition temperature, storage modulus, and coefficient of thermal expansion were investigated for the analysis of curing behavior. The reliability of ACF were observed in thermal cycle and high temperature-high humidity test. ACF using cationic initiator showed faster curing, lower CTE, and higher $T_g$ than the case of using imidazole curing agent, which is important for the high temperature stability. Furthermore, ACF using cationic initiator maintained a stable contact resistance in reliability test, although it was cured at low temperature and fast rate. With these results, it was confirmed that the curing method of epoxy had great effect on thermo-mechanical properties and reliability of ACF.

Particle Size-Dependent Failure Analysis of Particle-Reinforced Metal Matrix Composites using Dislocation Punched Zone Modeling (전위 펀치 영역 모델링에 의한 입자 강화 금속지지 복합재의 입자 크기 의존 파손 해석)

  • Suh, Yeong Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.3
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    • pp.275-282
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    • 2014
  • Particle-reinforced metal matrix composites exhibit a strengthening effect due to the particle size-dependent length scale that arises from the strain gradient, and thus from the geometrically necessary dislocations between the particles and matrix that result from their CTE(Coefficient of Thermal Expansion) and elastic-plastic mismatches. In this study, the influence of the size-dependent length scale on the particle-matrix interface failure and ductile failure in the matrix was examined using finite-element punch zone modeling whereby an augmented strength was assigned around the particle. The failure behavior was observed by a parametric study, while varying the interface failure properties such as the interface strength and debonding energy with different particle sizes and volume fractions. It is shown that the two failure modes (interface failure and ductile failure in the matrix) interact with each other and are closely related to the particle size-dependent length scale; in other words, the composite with the smaller particles, which is surrounded by a denser dislocation than that with the larger particles, retards the initiation and growth of the interface and matrix failures, and also leads to a smaller amount of decrease in the flow stress during failure.

Numerical Analysis of Thermo-mechanical Stress and Cu Protrusion of Through-Silicon Via Structure (수치해석에 의한 TSV 구조의 열응력 및 구리 Protrusion 연구)

  • Jung, Hoon Sun;Lee, Mi Kyoung;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.20 no.2
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    • pp.65-74
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    • 2013
  • The through-silicon via (TSV) technology is essential for 3-dimensional integrated packaging. TSV technology, however, is still facing several reliability issues including interfacial delamination, crack generation and Cu protrusion. These reliability issues are attributed to themo-mechanical stress mainly caused by a large CTE mismatch between Cu via and surrounding Si. In this study, the thermo-mechanical reliability of copper TSV technology is investigated using numerical analysis. Finite element analysis (FEA) was conducted to analyze three dimensional distribution of the thermal stress and strain near the TSV and the silicon wafer. Several parametric studies were conducted, including the effect of via diameter, via-to-via spacing, and via density on TSV stress. In addition, effects of annealing temperature and via size on Cu protrusion were analyzed. To improve the reliability of the Cu TSV, small diameter via and less via density with proper via-to-via spacing were desirable. To reduce Cu protrusion, smaller via and lower fabrication temperature were recommended. These simulation results will help to understand the thermo-mechanical reliability issues, and provide the design guideline of TSV structure.

Hierarchical Finite-Element Modeling of SiCp/Al2124-T4 Composites with Dislocation Plasticity and Size-Dependent Failure (전위 소성과 크기 종속 파손을 고려한 SiCp/Al2124-T4 복합재의 계층적 유한요소 모델링)

  • Suh, Yeong-Sung;Kim, Yong-Bae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.2
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    • pp.187-194
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    • 2012
  • The strength of particle-reinforced metal matrix composites is, in general, known to be increased by the geometrically necessary dislocations punched around a particle that form during cooling after consolidation because of coefficient of thermal expansion (CTE) mismatch between the particle and the matrix. An additional strength increase may also be observed, since another type of geometrically necessary dislocation can be formed during extensive deformation as a result of the strain gradient plasticity due to the elastic-plastic mismatch between the particle and the matrix. In this paper, the magnitudes of these two types of dislocations are calculated based on the dislocation plasticity. The dislocations are then converted to the respective strengths and allocated hierarchically to the matrix around the particle in the axisymmetric finite-element unit cell model. The proposed method is shown to be very effective by performing finite-element strength analysis of $SiC_p$/Al2124-T4 composites that included ductile failure in the matrix and particlematrix decohesion. The predicted results for different particle sizes and volume fractions show that the length scale effect of the particle size obviously affects the strength and failure behavior of the particle-reinforced metal matrix composites.

An Analysis of the Landscape Character in Environment Friendly Cultivated Land Based on Rural Amenity (어메니티에 기초한 친환경농업 경작지의 경관특성요소 분석)

  • Kim Hye-Min;Kang Bang-Hun
    • The Korean Journal of Community Living Science
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    • v.17 no.1
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    • pp.11-21
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    • 2006
  • This research is focused on not only cultivated land as an important factor which represented the agricultural district, but also details of the research in the landscape of cultivated land. Moreover, we also focused on the cultivated land operating environmental friendly agriculture which took a lot of interest among the landscape of the cultivated land. The reason is, we judged environmental friendly agriculture is not only the simple purpose only for manufacturing food but also the key role for preserving their environment and landscape, and making sustainable agriculture. For this reason, our research treats the analysis that operating environmental friendly landscape has what kinds of different factors in landscape characteristic compare with other general agricultural methods. Plus we selected evaluating both the degree of citizen's presence and the degree of rural residents's importance in those factors as a mainly research matter. We drew out the landscape of cultivated land and concerning factors by analyzing policies(ESA, CSS, CTE, MFSP, ACL, etc) concerned with overseas agricultural landscape to deduct landscape Character factors in internal cultivated land. Based on eleven items of landscape factors in cultivated land deducted by documents research, we started to conduct field studies during MAY. 7th. 2004 $\sim$ JUL. 8th, DEC. 1th $\sim$ 3th reaching 32 villages and concerned institutes to deduct the factors in landscape characteristic in agricultural cultivated land in detail. We analyzed degrees of importance and preference in citizen and rural residents classified by 5 province of the whole country to evaluate the landscape Character factors in environmental friendly agriculture deducted by field research and 21 documents including extra items such as a scene of duck grazing by the duck techniques which is very popular way among internal environmental friendly agriculture, gardening space composed around farm and furrow on slope ground formed by unique topology in hilly country. The research period was progressed for 20 days from MAY. 28th. 2005 $\sim$ JUN. 17th. This research is the result that cultivated land landscape as a detail item holding agricultural environment especially, it is also meaningful result in environmental friendly agriculture as a basic research, because it is not only a value of simple food producing but also very effective role in both landscape and environmental parts.

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Human Health Risk Assessment of Benzene from Industrial Complexes of Chungcheong and Jeonla Province (충청·전라지역 산업단지 주변지역에서의 벤젠 인체 위해성 평가)

  • Jang, Yong-Chul;Lee, Sungwoo;Shin, YongSeung;Kim, Heekap;Lee, Jonghyun
    • Journal of Environmental Impact Assessment
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    • v.20 no.4
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    • pp.497-507
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    • 2011
  • This research studied human health risk assessment of benzene from industrial complexes of Chungcheong Province (Seosan industrial complex) and Jeonla Province (Iksan industrial complex and Yeosoo industrial complex). The residents near the industrial complexes areas can be often exposed to volatile organic compounds (e.g., benzene, toluene, xylenes) through a number of exposure pathways, including inhalation of the organic pollutant via various environmental matrices (air, water and soil), contaminated water, and soil intake. Benzene is well known to be a common carcinogenic and toxic compound that is produced from industrial and oil refinery complexes. In this study, a number of samples from water, air, and soil were taken from the residential settings and public school zones located near the industrial complex sites. Based on the carcinogenic risk assessment, the risk estimates were slightly above $10{\times}10^{-6}$ at all three industrial sites. According to deterministic risk assessment, inhalation was the most important route. The distribution of benzene in the environment would be dependent on vapor pressure, and the physical property influencing the extent of the potential risks. Non-carcinogenic risk assessment of benzene shows that the values of Hazard Index(HI) were much lower than 1.0 at all industrial complexes. Therefore, benzene was not a cause of concern in terms of non-carcinogenic risk posed to the residents near the sites. When compared to probabilistic risk assessment, the CTE(central tendency exposure) cancer risk values of deterministic risk assessment were close to the mean values predicted by the probabilistic risk assessment. The RME(reasonable maximum exposure) values fell within the range of 95% to 99.9% estimated by the probabilistic risk assessment. Since the values of carcinogenic risk assessment were higher than $10{\times}10^{-6}$, further detailed monitoring and refined risk assessment for benzene may be warranted to estimate more reliable and potential inhalation risks to receptors near the industrial complexes.

Synthesis and Film Properties of Cross-linked Polysulfone with Imide Side Chain (이미드 곁가지로 가교되는 폴리설폰의 합성 및 필름 특성)

  • Lee Eun-Sang;Hong Sung-Kwon;Kim Yong-Seok;Lee Jae-Heung;Kim In-Sun;Won Jong-Chan
    • Polymer(Korea)
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    • v.30 no.2
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    • pp.140-145
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    • 2006
  • The mort commonly available substrate material is glass in the display fibrication process. However, glass is not desirable due to its heaviness and fragility. Recently, plastics such polysulfone (PSF), polyethesulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET) and cyclic olefin polymers (COP) have been investigated to replace glass as a substrate material for display fibrication. Plastic substrates are advantageous in that they are lightweight, huh impart resistance, flexibility, and ability for roll to roll manufacturing process. But many plastics have poor chemical resistance in organic solvent. The chemica resistance is also lequired because they are exposed to solvents for various chemical treatments din the manufacturing process. So, we have an interest in the chemical modification of PSF to improve chemical resistance. We introduced crosslinkable imide moieties using chloromethylation method for the modification of PSF which could be overcome above shortcomings for display substrate based on plastic film. We prepared the cross-linked polysulfone films which were represented chemical resistance in HeOH, THF, DMSO and NMP. The thermal properties were measured by TGA, DSC and TMA. As the results, we have confirmed to enhance of the thermal property. They had low coefficient of thermal expansion (CTE) which decreased to 15% and had increased $T_g\;from\;180^{\circ}C\;to\;252^{\circ}C$. Cross-linked polysulfone films with imide side-chain had good optical properties and chemical resistance so that they could be used as flexible display substrate.