• Title, Summary, Keyword: CTE (coefficient of thermal expansion)

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Evaluation of Temperature-dependency of CTE of Materials for MEMS Using ESPI (ESPI를 이용한 MEMS용 소재의 열팽창 계수 온도 의존성 평가)

  • Kim, Dong-Won;Kim, Hong-Jae;Lee, Nak-Kyu;Choi, Tae-Hoon;Na, Kyoung-Hoan;Kwon, Dong-Il
    • Proceedings of the KSME Conference
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    • pp.1315-1320
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    • 2003
  • The thermal expansion coefficient, which causes the micro failure at the interfacial state of thin films is necessary to consider for proper designing MEMS. The effect of temperature on the coefficient of thermal expansion(CTE) of $SiO_2$ and $Si_3N_4$ film was investigated. Thermal strain induced by mismatch of CTE between substrate and thin film continuously measured with resolution-improved electronic speckle pattern interferometry(ESPI). The thermal stress induced by mismatch of CTE derivate through thermal strain. The thermal expansion coefficients of thin film were calculated with the general equation of CTE and thermal stress in thin films, and it confirmed that CTE of $SiO_2$changed from $0.25{\times}10^{-6}/^{\circ}C$ to $1.4{\times}10^{-6}/^{\circ}C$ with temperature increasing from 50 to $600^{\circ}C$

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Effects of Magnetic Characteristics on Coefficient of Thermal Expansion in Fe-Ni-Co-C Invar Alloy for Transmission Line (송전선 강심용 Fe-Ni-Co-C 합금의 열팽창계수에 미치는 자기적 특석의 영향)

  • Kim, Bong-Seo;Kim, Byung-Geol;Lee, Hee-Woong
    • Proceedings of the KIEE Conference
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    • pp.1346-1348
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    • 2001
  • Generally, Invar alloy shows very low thermal expansion characteristics, lower than $2{\times}10^{-6}$/K approximately. To apply Fe-Ni-Co-C Invar alloy as a core material for large ampacity transmission line we studied the effects of magnetic properties on coefficient of thermal expansion. The coefficient of thermal expansion(CTE) suddenly decreases with addition of a little carbon(0.08%), increases with the increasing carbon and has a constant value at the composition over than 1.0%C. The trend of Curie temperature change with carbon is similar with that of CTE. Therefore, the CTE has a linear relationship with Curie temperature. However, the CTE linearly decreases with the ratio of saturation magnetization and Curie temperature(${\sigma}_s/T_c$).

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The effect of cetyltrimethylammonium bromide on the coefficient of thermal expansion and optical transmittance of poly(ether sulfone) film

  • Vo, Nhat Tri;Kim, Dukjoon
    • Korean Journal of Chemical Engineering
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    • v.34 no.9
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    • pp.2536-2540
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    • 2017
  • Cetyltrimethylammonium bromide (CTAB) was used as a stabilizing agent for PES films, and its effect on the coefficient of thermal expansion (CTE) and optical transmittance (OT) of PES films was investigated. The CTE of PES film decreased with increasing CTAB concentration up to 0.5 wt%, because of the improved intermolecular interaction between polymer chains via CTAB molecules. When 0.5 wt% of CTAB was added to the PES film, the CTE of polymer film decreased from 66 to $50ppm/^{\circ}C$ without noticeable reduction in OT. At such a low CTAB concentration range (<0.5 wt%), the glass transition temperature ($T_g$) and tensile strength increased with CTAB. At high CTAB concentration above 0.5 wt%, however, it had a negative effect on the properties of PES film - CTE increased but $T_g$ and tensile strength decreased with it.

Effect of Nano Grain Growth on Coefficient of Thermal Expansion in Electroplated Fe-Ni Invar Alloy (Fe-Ni Invar 합금에서 나노 결정립 성장이 열팽창계수에 미치는 영향)

  • Yim, Tai Hong;Choe, Byung Hak;Jeong, Hyo Tae
    • Korean Journal of Materials Research
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    • v.24 no.10
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    • pp.515-519
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    • 2014
  • The aim of this paper is to consider the effect of annealing on the coefficient of thermal expansion (CTE) of electroplated Invar Fe-Ni alloy. The CTE of the as-electroplated alloy is lower than those of alloys annealed at $400^{\circ}C$ and $800^{\circ}C$. XRD peaks become sharper as the as-electroplated alloy is annealed, which means the grain growth. The average grain sizes of as-electroplated and as-annealed alloys at $400^{\circ}C$ and $800^{\circ}C$ are 10 nm, 70 nm, and $2{\mu}m$, respectively, as determined by TEM and EBSD analyses. The CTE variation for the various grain sizes after annealing may come from the magnetostriction effect, which generates strain due to changes in the magnetization state of the alloys. The thermal expansion coefficient is considered to be affected by nano grain size in electroplated Fe-Ni Invar alloys. As grain size decreases, ferromagnetic forces might change to paramagnetic forces. The effect of lattice vibration damping of nano grain boundaries could lead to the decrease of CTE.

The Effect of Grain Size and Film Thickness on the Thermal Expansion Coefficient of Copper and Silver Thin Films (구리와 은 박막의 열팽창계수에 미치는 결정립 크기와 박막 두께의 영향)

  • Hwang, Seulgi;Kim, Youngman
    • Korean Journal of Metals and Materials
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    • v.48 no.12
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    • pp.1064-1069
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    • 2010
  • Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

Establishment of CTE Measurement Procedure for PPLP at 77 K for HTS Power Cables using Double Extensometers

  • Dedicatoria, Marlon J.;Dizon, John Ryan C.;Shin, Hyung-Seop;Sim, Ki-Duk
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.4
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    • pp.24-27
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    • 2012
  • The measurement of the coefficient of thermal expansion (CTE) of polypropylene laminated paper (PPLP) as electric insulating material is important for its practical superconducting device application. The thermal strain induced to HTS tapes and its insulating material during cooling from room temperature might largely affect the critical current ($I_c$) of HTS tapes. In this study, the thermal contraction of PPLP material was measured during cooling from 300 K to 77 K using double extensometers. Initially, the CTE of a brass tape was measured and it was compared with a reference data. It was found that the measured thermal expansion data of the brass material approaches that of the reference one. Based on the results, it was then confirmed that the measurement technique could be applied to thin and flexible samples. Therefore, the same measurement procedure was applied to PPLP material using double extensometers. As a result, the linear CTE of the PPLP at 77 K has been measured to be ${\sim}15.3{\times}10^{-6}/K$. Also, it was found that the thermal contraction characteristics of PPLP was dominated by polypropylene on the cross direction (higher thermal contraction) while it was dominated by Kraft paper on the machine direction (lower thermal contraction). Overall, this measurement procedure could be adopted for the determination of CTE of flexible materials such as PPLP.

A Change of Thermal Expansion Coefficient according to Li2O-added Porcelain for Dental Zirconia (치과용 지르코니아 도재의 Li2O 첨가에 따른 열팽창계수 변화)

  • Yoon, Han-Sok
    • Journal of Technologic Dentistry
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    • v.31 no.4
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    • pp.25-30
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    • 2009
  • Zirconia($ZrO_2$) has attracted much attention in science and technology because of its high refractive index, high melting temperature, hardness, low thermal conductivity and corrosion barrier properties. And it is widely used as the dental restoration material because of its esthetic appearance. In this research, we analyzed the particle size and composition of the imported dental porcelain for zirconia. And the glass frit was produced. To decrease the glass transition temperature and softening temperature of the glass frit, $Li_2O$ was added into it and the effect of $Li_2O$ on the firing temperature was researched. Then the glass which contains leucite crystal with a high coefficient of thermal expansion(CTE) was manufactured and it was mixed with the glass frit to control the CTE. The phase composition were analyzed using the X-ray diffraction. The morphologies of the samples were observed by the scanning electron microscope. The 4wt% $Li_2O$-added glass frit has the optimal glass transition temperature and softening temperature. And 6 wt% leucite crystal was mixed with the glass frit to control the CTE. From the experimental results of crystallization, the crystal phase was found only leucite crystal.

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Through-thickness CTE and Void Content of Carbon Fabric Phenolic Composites with Respect to Compaction (압착에 따른 탄소직물 페놀 복합재의 두께방향 열팽창계수와 기공분율)

  • Kim, Jong-Woon;Kim, Hyong-Geun;Lee, Dai-Gil
    • Proceedings of the KSME Conference
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    • pp.192-197
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    • 2004
  • The anisotropy in coefficient of thermal expansion (CTE) between the in-plane and out-of-plane of 3-dimensional thick composite structures induces residual stresses and the large void content due to insufficient compaction of fabric composites, which results in low interlaminar strengths. In order to reduce the through thickness CTE and the void content, in this work, carbon fabric phenolic laminates were compacted by pressure generated by autoclave and a compressive jig, from which the through-thickness CTEs and the void contents were measured. From the measurement, it was found that the through-thickness CTE and the void content had different characteristics from ordinary composites due to gas produced during the cure reaction of phenolic resin.

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Effect of Chain Orientation on the Characteristics of PEN Flexible Substrate (사슬 배향이 폴리(에틸렌 나프탈레이트) 유연기판 특성에 미치는 영향)

  • Kim, Jongwha;Kang, Ho-Jong
    • Polymer(Korea)
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    • v.37 no.6
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    • pp.711-716
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    • 2013
  • The effect of chain orientation and relaxation on the characteristics of poly(ethylene naphthalate) (PEN) flexible substrate has been studied. It was found that the coefficient of thermal expansion (CTE) of PEN under $100^{\circ}C$ decreased as low as $20ppm/^{\circ}C$ due to the lowering of chain mobility by chain orientation. The thermal shrinkage was found to appear near glass transition temperature because of chain relaxation. It could be minimized by thermal annealing but CTE increased again up to $70ppm/^{\circ}C$ which was 65% of intrinsic CTE of PEN. Unstrained thermal annealing made possible to avoid the thermal shrinkage with maintaining low CTE obtained by chain orientation. Chain orientation did not affect the optical transmittance; however, thermal annealing caused the decrease of optical transmittance up to 5%. This was understood by the minor crystallization due to the thermal annealing near glass transition temperature.

Empirical Study for the Effects of Filler Shape on the Thermal Expansion Coefficient of PP Composites (충전제 함량 및 형태에 따른 PP복합체의 열팽창계수 변화에 대한 실증적 연구)

  • Hwang, Hyo-Yeon;Jeoung, Sun-Kyoung;Shim, Je-Hyeon;Kim, Jae-Min;Lee, Kee-Yoon
    • Polymer(Korea)
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    • v.34 no.4
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    • pp.352-356
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    • 2010
  • The effects of the filler shapes and contents on the coefficient of thermal expansion (CTE) for polypropylene (PP) composites which included three dimensional ellipsoids ($a_1>a_2>a_3$), as determined by two aspect ratios (${\rho}_\alpha=a_1/a_3$ and ${\rho}_\beta=a_1/a_2$) were analyzed by the theoretical approach proposed by Lee and Paul and compared with the experimental results. The shapes of fillers in the composites were various, such as spherical, fiber, disc, and ellipsoid, using barium sulfate, glass fiber, and mica. The longitudinal CTE of barium sulfate whose shape was sphere ($\rho_\alpha=\rho_\beta=1$) decreased. For the glass fiber, primary aspect ratio decreased with the filler content, and longitudinal CTE decreased as filler contents increased. Normal CTE initially increased in the lower filler content. For the mica, longitudinal and transverse CTE decreased but normal CTE increased in the lower filler content like predicted values.