• Title/Summary/Keyword: Coefficient of thermal expansion

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Construction and Application of Experimental Formula for Nonlinear Behavior of Ferroelectric Ceramics Switched by Electric Field at Room Temperature during Temperature Rise

  • Ji, Dae Won;Kim, Sang-Joo
    • Journal of the Korean Ceramic Society
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    • v.55 no.1
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    • pp.67-73
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    • 2018
  • A poled lead zirconate titanate (PZT) cube specimen that is switched by an electric field at room temperature is subject to temperature increase. Changes in polarization and thermal expansion coefficients are measured during temperature rise. The measured data are analyzed to obtain changes in pyroelectric coefficient and strain during temperature change. Empirical formulae are developed using linear or quadratic curve fitting to the data. The nonlinear behavior of the materials during temperature increase is predicted using the developed formulae. It is shown that the calculation results can be compared successfully with the measured values, which proves the accuracy and reliability of the developed formulae for the nonlinear behavior of the materials during temperature changes.

Compositional Effects on Thermal and Electrical Properties of Dielectric Glass Paste

  • Kim, Teock-Nam;Lee, Jea-Yeol;Kim, Hyung-Sun;Hu, Jeung-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2000.01a
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    • pp.95-96
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    • 2000
  • The effect of $Al_2O_3$ on the dielectric constant and the coefficient of thermal expansion of lead borosilicate glasses for the application of PDP glass paste was investigated. Measurements were made theoretically by using empirical equations on the composition of the of glasses in which the $PbO/Al_2O_3$, $B_2O_3/Al_2O_3$ and $SiO_2/Al_2O_3$ ratios were systematically varied. As a result, with increasing $PbO/Al_2O_3$ the thermal expansion coefficient and the dielectric constant noticeably increased, while the change of $B_2O_3/Al_2O_3$ and $SiO_2/Al_2O_3$ ratios did not affect those properties of the glasses.

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Studies on AlF3-(Mg+Sr+Ba)F2-P2O5 Glasses I. Glass Forming Ranges of Fluorophosphate System and Its Various Properties (AlF3-(Mg+Sr+Ba)F2-P2O5계 유리에 관한 연구 I. 유리화 범위와 특성)

  • 김정은;이종근
    • Journal of the Korean Ceramic Society
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    • v.24 no.2
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    • pp.117-122
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    • 1987
  • Glass forming ranges in the AlF3-(Mg+Sr+Ba)F2-P2O5 system are studied and ultraviolet transmission, infrared transmission, coefficient of refractive index, thermal expansion coefficient, density and chemical durability of the glasses are determined. Glass forming range is restricted MgF2 0-10wt%, SrF2 10-50wt%, BaF2 10-40wt% in this system. While BaF2 is substituted by SrF2, density and refractive index are decreased, micro hardness and thermal expansion coefficient are increased according to the increasing of SrF2 at fixed MgF2 contents. These samples represent high transmittance(93%) from 400nm to 3800nm and chemical durability of these samples show less than 0.3mg/$\textrm{cm}^2$$.$hy by weightloss.

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Thermo-Mechanical Reliability of TSV based 3D-IC (TSV 기반 3차원 소자의 열적-기계적 신뢰성)

  • Yoon, Taeshik;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.1
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    • pp.35-43
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    • 2017
  • The three-dimensional integrated circuit (3D-IC) is a general trend for the miniaturized and high-performance electronic devices. The through-silicon-via (TSV) is the advanced interconnection method to achieve 3D integration, which uses vertical metal via through silicon substrate. However, the TSV based 3D-IC undergoes severe thermo-mechanical stress due to the CTE (coefficient of thermal expansion) mismatch between via and silicon. The thermo-mechanical stress induces mechanical failure on silicon and silicon-via interface, which reduces the device reliability. In this paper, the thermo-mechanical reliability of TSV based 3D-IC is reviewed in terms of mechanical fracture, heat conduction, and material characteristic. Furthermore, the state of the art via-level and package-level design techniques are introduced to improve the reliability of TSV based 3D-IC.

Nondestructive Interfacial Evaluation and Cure Monitoring of Carbon Fiber/Epoxyacrylate Composite with UV and Thermal Curing Using Electro-Micromechanical Technique (Electro-Micromechanical 시험법을 이용한 탄소 섬유 강화 에폭시아크릴레이트 복합재료의 자외선과 열경화에 따른 경화 모니터링 및 비파괴적 계면 평가)

  • 박종만;공진우;김대식;이재락
    • Polymer(Korea)
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    • v.27 no.3
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    • pp.189-194
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    • 2003
  • Interfacial evaluation, damage sensing and cure monitoring of single carbon fiber/thermo setting composite with different curing processes were investigated using electro-micromechanical test. After curing, the residual stress was monitored by measurement of electrical resistance and then compared to various curing processes. In thermal curing case, matrix tensile strength, modulus and interfacial shear strength were higher than those of ultraviolet curing case. The shrinkage measured during thermal curing occurred significantly by matrix shrinkage and residual stress due to the difference in thermal expansion coefficient. The apparent modulus measured in the thermal curing indicated that mechanical and interfacial properties were highly improved. The reaching time to the same stress of thermal curing was faster than that of UV curing case.

Fabrication and Characteristics of Bioceramics for Artificial Dental Crowns (II) Mechanical Characteristics, Color and Color difference (인공치용 바이오 세라믹스의 제조 및 특성(II) 기계적 특성과 색도 및 색차변화)

  • 고영호;한복섭;이준희
    • Journal of the Korean Ceramic Society
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    • v.32 no.10
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    • pp.1203-1211
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    • 1995
  • The tests of three point bending and vickers hardness have been carried out to investigate mechanical characteristics of bioceramics for artificial dental crowns. And color and color difference test has been performed to study chromaticity changes after sintering specimens composited with glass and leucite powders. In addition, thermal dilation test has been carried out to examine bonding relations between dental porcelain and metal frame (Ni-Cr alloy). The result of three point bending test showed a maximum strength of about 68 MPa. Thermal expansion coefficient changed from 8.3$\times$10-6/$^{\circ}C$ to 13.5$\times$10-6/$^{\circ}C$ with increasing leucite content (0~30wt.%) in glass matrix. Bonding between porcelain (25% leucite-75% glass) and Ni-Cr alloy was excellent.

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Grain Boundary Microcracking in ZrTiO4-Al2TiO5 Ceramics Induced by Thermal Expansion Anisotropy

  • Kim, Ik-Jin;Kim, Hyung-Chul;Lee, Kee-Sung;Han, In-Sub
    • Journal of the Korean Ceramic Society
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    • v.40 no.2
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    • pp.109-112
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    • 2003
  • The grain-boundary microcracking materials in the system $Al_2$TiO$_{5}$ -ZrTiO$_4$(ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3~1.3$\times$10$^{-6}$ K loin compared to 8.29$\times$10$^{6}$ K of pure ZrTiO$_4$and 0.68$\times$10$^{6}$ K of polycrystalline $Al_2$TiO$_{5}$ , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of $Al_2$TiO$_{5}$ , 9.70$\times$10$^{6}$ K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal a ies of the $Al_2$TiO$_{5}$ phase.

Erratum to: "Grain Boundary Microcracking in ZrTiO4-Al2TiO5 Ceramics Induced by Thermal Expansion Anisotropy"

  • Kim, Ik-Jin;Kim, Hyung-Chul;Lee, Kee-Sung;Han, In-Sub
    • Journal of the Korean Ceramic Society
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    • v.40 no.3
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    • pp.317-321
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    • 2003
  • The grain-boundary microcracking materials in the system A1$_2$Ti $O_{5}$ -ZrTi $O_4$(ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3~1.3$\times$10$^{-6}$K compared to 8.29$\times$10$^{-6}$K of pure ZrTi $O_4$and 0.68$\times$10$^{-6}$K of polycrystalline A1$_2$Ti $O_{5}$ , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of A1$_2$Ti $O_{5}$ , 9.70$\times$10$^{-6}$K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal axes of the A1$_2$Ti $O_{5}$ phase.

Selection of Optimal Sensor Locations for Thermal Error Model of Machine tools (공작기계 열오차 모델의 최적 센서위치 선정)

  • 안중용
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1999.10a
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    • pp.345-350
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    • 1999
  • The effectiveness of software error compensation for thermally induced machine tool errors relies on the prediction accuracy of the pre-established thermal error models. The selection of optimal sensor locations is the most important in establishing these empirical models. In this paper, a methodology for the selection of optimal sensor locations is proposed to establish a robust linear model which is not subjected to collinearity. Correlation coefficient and time delay are used as thermal parameters for optimal sensor location. Firstly, thermal deformation and temperatures are measured with machine tools being excited by sinusoidal heat input. And then, after correlation coefficient and time delays are calculated from the measured data, the optimal sensor location is selected through hard c-means clustering and sequential selection method. The validity of the proposed methodology is verified through the estimation of thermal expansion along Z-axis by spindle rotation.

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Prediction of the Equivalent Coefficient of Thermal Expansion of Fiber Reinforced Plastic Lamina and Thermal Pointing Error Analysis of Satellites (섬유강화 복합재료 등가열팽창계수 예측 및 인공위성 열지향오차 해석)

  • You, Won Young;Lim, Jae Hyuk;Kim, Sun Won;Kim, Chang-Ho;Kim, Sung-Ho
    • Aerospace Engineering and Technology
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    • v.13 no.1
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    • pp.76-85
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    • 2014
  • In this paper, the equivalent coefficient of thermal expansion (CTE) of fiber reinforced plastic composite material is investigated with various CTE prediction schemes. Although there are several methods for predicting the equivalent CTEs, most of them have some limitations of are not much accurate when comparing prediction results with test results. In the framework of computational homogenization, a representative volume element is taken from the predefined fiber-volume ratio, and modelled with finite element mesh. Finally, the equivalent CTEs are obtained by applying periodic boundary condition. To verify the performance of the proposed method, the results obtained are compared with those by the existing methods and test results. Additionally, the thermal pointing error analysis for star tracker support structure is conducted and its accuracy is estimated according to CTE prediction schemes.