• Title, Summary, Keyword: Thermal Expansion Coefficient (TEC)

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Effects of Mn, Co Additions and Microporosities on the Thermal Expansion Coefficient of powder Rolled Fe-36Ni Invar Strip (분말압연에 의해 제조된 인바(Fe-36Ni)판재의 열팽창 계수에 미치는 미세 기공 및 합금 원소 첨가 효과)

  • 이동원
    • Journal of Korean Powder Metallurgy Institute
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    • v.2 no.3
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    • pp.223-230
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    • 1995
  • The effects of Mn and Co additions up to 0.6 and 2.0 wt% respectively and the amount of cold-rolled reduction on the thermal expansion coefficient (TEC) of powder rolled Fe-Ni Invar strips were investigated. The compacted strips were sintered, homogenized and cold-rolled to the final thickness of 0.8 mm, 0.65 mm and 0.4 mm. All the strips reached full density except the case of 0.8 mm sample which has a very few porosities. The interstitials which are well known to increase TEC were minimized to the level of 10 rpm C,5 and N,0 by the processing. TEC was found to decrease by increasing the cold reduction. The Mn content had little effect on the TEC. But in Fe-Ni-Co system, TEC decreased with Co content up to 0.4 wt% and then increased, yielding the minimum value of $0.2 {\times} 10-6/^{\circ}C$ at 0.4 wt% Co. This value is much lower than that of commercial Invar product. Such effect of Co is considered to be related with the maxiumum spontaneous- magnetostriction effect.

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Interfacial Evaluation and Damage Sensing of Carbon Fiber/Epoxy-AT-PEI Composite using Electro-Micromechanical Techniques (Electro-micromechanical 시험법을 이용한 탄소섬유 강화 Epoxy-AT PEI 복합재료의 손상 감지능 및 계면물성 평가)

  • Kim, Dae-Sik;Kong, Jin-Woo;Park, Joung-Man;Kim, Minyoung;Kim, Wonho;Ahn, Byung-Hyun;Park, Jin-Ho
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.212-215
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    • 2002
  • Interfacial evaluation and damage sensing of the carbon fiber/epoxy-amine terminated (AT)-polyetherimide (PEI) composites were performed using micromechanical test and electrical resistance measurement. As AT-PEI content increased, the fracture toughness of epoxy-AT-PEI matrix increased, and thus their interfacial shear strength (IFSS) was improved due to the improved toughness. After curing process, the changes in electrical resistance (ΔR) with increasing AT-PEI contents increased gradually because of the changes in thermal expansion coefficient (TEC) and thermal shrinkage of matrix. Matrix fracture toughness was correlated to the IFSS, residual stress and electrical resistance. The results obtained from the electrical resistance measurement during curing process, reversible stress/strain, and durability test were consistent with modified matrix toughness properties.

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Cathode Properties of Sm-Sr-(Co,Fe,Ni)-O System with Perovskite and Spinel Structures for Solid Oxide Fuel Cell (고체산화물 연료전지의 페로브스카이트와 스피넬 구조를 갖는 Sm-Sr-(Co,Fe,Ni)-O 시스템의 공기극 특성)

  • Baek, Seung-Wook;Kim, Jung-Hyun;Baek, Seung-Whan;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.133-136
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    • 2007
  • Perovskite-structured samarium strontium cobaltite (SSC), which is mixed ionic electronic conductor (MIEC), is considered as a promising cathode material for intermediate temperature-operating solid oxide fuel cell (SOFC) due to its high electrocatalytic property. Cathode material containing cobalt (Co) is unstable at high temperature and has a relatively high thermal expansion property. In this paper, Sm-Sr-(Co,Fe,Ni)-O system with perovskite and spinel structures was investigated in terms of electrochemical property and thermal expansion property, respectively. Area specific resistance (ASR) was measured by ac impedance spectroscopy to investigate the electrochemical property of cathode, and thermal expansion coefficient (TEC) was measured by using dilatometer. Micro structure of cathode was observed by scanning electron microscopy. Perovskite-structured $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ showed the ASR of $0.87{\Omega}/cm^{2}$, and $Sm_{0.5}Sr_{0.5}NiO_{3-\delta}$, which actually has a spinel structure, showed the lowest TEC value of $13.3{\times}10^{-6}/K$.

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Mixing Rules of Young's Modulus, Thermal Expansion Coefficient and Thermal Conductivity of Solid Material with Particulate Inclusion

  • Hirata, Yoshihiro;Shimonosono, Taro
    • Journal of the Korean Ceramic Society
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    • v.53 no.1
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    • pp.43-49
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    • 2016
  • This analyzed a Young's modulus (E), a thermal expansion coefficient (TEC, ${\beta}$) and a thermal conductivity (${\kappa}$) of the material with simple cubic particulate inclusion using two model structures: a parallel structure and a series structure of laminated layers. The derived ${\beta}$ equations were applied to calculate the ${\beta}$ value of the W-MgO system. The accuracy was higher for the series model structure than for the parallel model structure. Young's moduli ($E_c$) of sintered porous alumina compacts were theoretically related to the development of neck growth of grain boundary between sintered two particles and expressed as a function of porosity. The series structure model with cubic pores explained well the increased tendency of $E_c$ with neck growth rather than the parallel structure model. The thermal conductivity of the three phase system of alumina-mullite-pore was calculated by a theoretical equation developed in this research group, and compared with the experimental results. The pores in the sintered composite were treated as one phase. The measured thermal conductivity of the composite with 0.5-25% porosity (open and closed pores) was in accordance with the theoretical prediction based on the parallel structure model.

Performance degradation of SOFC caused by increase of polarization resistance for the cathode during long-term test (공기극 분극 저항 증가에 따른 SOFC 단전지 성능 감소에 관한 연구)

  • Park, Kwang-Jin;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.349-352
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    • 2009
  • In this study, the relation between the performance degradation of SOFC single cell and the increase of polarization resistance for the cathode is investigated. $Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_3$(PSCF3737, $19.4{\times}10^{-6}K^{-1}$) and $Gd_{0.1}Ce_{0.9}O_2$ (CGO91, $12{\times}10^{-6}K^{-1}$) are used as a cathode and an electrolyte, respectively. The polarization resistance of cathode is increased due to the delamination caused by thermal expansion coefficient difference. The voltage drop with 10%/1000h decline rate occurs during long-term, when the interface between the cathode and the electrolyte is delaminated due to TEC difference.

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Nondestructive Damage Sensing and Cure Monitoring of Carbon Fiber/Epoxyacrylate Composite with UV and Thermal Curing using Electro-Micromechanical Technique (Electro-Micromechanical 시험법을 이용한 탄소섬유 강화 Epoxyacrylate 복합재료의 UV 및 열경화에 따른 비파괴적 손상 감지능 및 경화 Monitoring)

  • Kong, Jin-Woo;Kim, Dae-Sik;Park, Joung-Man;Lee, Jae-Rock
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.261-264
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    • 2002
  • Interfacial evaluation, damage sensing and cure monitoring of single carbon fiber/thermosetting composite with different curing processes was investigated using electro-micromechanical test. After curing, residual stress was monitored by measurement of electrical resistance (ER) and then it was compared to correlate with various curing processes. In thermal curing, curing shrinkage appeared significantly by matrix shrinkage and residual stress due to the difference in thermal expansion coefficient (TEC). The change in electrical resistance (ΔR) on thermal curing was higher than that on ultraviolet (UV) curing. For thermal curing, apparent modulus was the highest and reaching time until same strain was faster. So far thermal curing shows strong durability on the IFSS after boiling test.

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Study of Pr0.3Sr0.7CoxMn(1-x)O3 as the Cathode Materials for Intermediate Temperature SOFC (중.저온형 고체 산화물 연료전지의 공기극 물질로 사용되는 Pr0.3Sr0.7CoxMn(1-x)O3 (x=0, 0.3, 0.5, 0.7, 1)에 관한 연구)

  • Park, Kwang-Jin;Kim, Jung-Hyun;Bae, Joong-Myeon
    • Journal of the Korean Ceramic Society
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    • v.44 no.4
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    • pp.214-218
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    • 2007
  • The decrease of polarization resistance in cathode is the key point for operating at intermediate temperature SOFC (solid oxide fuel cell). In this study, the influence of Co substitution in B-site at complex perovskite on the electronic conductivity of PSCM ($Pr_{0.3}Sr_{0.7}Co_xMn_{(1-x)}$) was investigated. The PSCM series exhibits excellent MIEC (mixed ionic electronic conductor) properties. The ASR (area specific resistance) of PSCM3773 was $0.174{\Omega}{\cdot}cm^2\;at\;700^{\circ}C$. The activation energy of PSCM3773 was also lower than other compositions of PSCM. The TEC(thermal expansion coefficient) was decreased by addition of Mn. The ASR values were increased gradually during the thermal cycling test of PSCM37773 due to the delamination between electrolyte and cathode materials. The delamination was caused by the difference of TEC.

Characterization of PSCF3737 for intermediate temperature solid oxide fuel cell (IT-SOFC) (중.저온형 고체 산화물 연료전지의 공기극으로 사용되는 PSCF3737 물질의 특성에 관한 연구)

  • Park, Kwang-Jin;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.61-64
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    • 2008
  • $Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_{3-\delta}$ (PSCF3737) was prepared and characterized as a cathode material for intermediate temperature-operating solid oxide fuel cell (IT-SOFC). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and electrical property measurement were carried out to study cathode performance of the material. XPS and EXAFS results proved that oxygen vacancy concentration was decreased and lattice constants of the perovskite structure material were increased by doping Fe up to 70 mol% at B-site of the crystal structure, which also extended the distance between oxygen and neighbor atoms. Thermal expansion coefficient (TEC) of PSCF3737 is smaller than that of $Pr_{0.3}Sr_{0.7}CoO_{3-\delta}$(PSC37) due to lower oxygen vacancy concentration. PSCF3737 showed better cathode performance than PSC37. It might be due good adhesion by a smaller difference of TEC between $Gd_{0.1}Ce_{0.9}O_2$ (CGO91) and electrode. Composite material PSCF3737-CGO91 showed better compatibility of TEC than PSCF3737. However, PSCF3737-CGO91 did not represent higher electrochemical property than PSCF3737 due to decreased reaction sites by CGO91.

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Structural analysis and thermal expansion property of Cu doped LSM for SOFCs (Cu가 도핑된 LSM의 구조분석과 열팽창특성 연구)

  • Noh, Tai-Min;Ryu, Ji-Seung;Kim, Jin-Seong;Jeong, Cheol-Weon;Lee, Hee-Soo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.21 no.4
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    • pp.175-180
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    • 2011
  • The doping effect of Cu in the Sr-doped lanthan manganites (LSM) has been investigated in terms of structural analysis and thermal expansion coefficient (TEC). The $La_{0.8}Sr_{0.2}Mn_{1-x}Cu_xO_3$ ($0{\leq}x{\leq}0.3$) were prepared by solid state reaction method and their crystal structure and TEC were measured. A decrease in the lattice parameters and the TEC were observed with increase eu content, whereas they were decreased for x = 0.3. For $0{\leq}x{\leq}0.2$, the decrease of the lattice parameter and the TEC with increase Cu content were attributed to the reduction of ionic radius of Cu ions due to the presence of $Cu^{3+}$ ions. For x = 0.3, however, the increase was originated from the formation of oxygen vacancies due 10 the presence of $Cu^{2+}$ and $Mn^{4+}$.

Development of Cobalt-free $La_xSr_{4-x}Fe_6O_{13}$ ($0{\leq}x{\leq}2$) Intergrowth Cathode Material for Solid Oxide Fuel Cells

  • Lee, Seung-Jun;Yong, Seok-Min;Kim, Dong-Seok;Kim, Do-Gyeong
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.45.1-45.1
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    • 2011
  • Cobalt-free $La_xSr_{4-x}Fe_6O_{13}$ ($0{\leq}x{\leq}2$) oxide have been synthesized and investigated as a potential cathode material for solid oxide fuel cells (SOFCs). $Sr_4Fe_6O_{13}$ consists of alternating perovskite layers ($Sr_4Fe_2O_8$) containing iron cations in octahedral oxygen coordination and $Fe_4O_5$ layers where iron cations have 5-fold coordination of two types-square pyramids and trigonal bipyramids. Our preliminary electrochemical testes of pristine $Sr_4Fe_6O_{13}$ show a rather high area specific resistance ($0.47{\Omega}cm^2$ at $700^{\circ}C$) for ~20 ${\mu}m$ thick layers with CGO electrolyte. The electrochemical performances are improved by La addition up to x=1 ($La_1Sr_3Fe_6O_{13}$, $0.06{\Omega}cm^2$ at $700^{\circ}C$). In addition, thermal expansion coefficient (TEC) values of $La_1Sr_3Fe_6O_{13}$ specimen demonstrated $15.1{\times}10^{-6}\;^{\circ}C^{-1}$ in the range of 25-900$^{\circ}C$, which provides good thermal expansion compatibility with the CGO electrolyte. An electrolyte supported (300-${\mu}m$-thick) single-cell configuration of $La_1Sr_3Fe_6O_{13}$/CGO/Ni-CGO delivered a maximum power density of 584 $mWcm^{-2}$ at $700^{\circ}C$. In addition, an anode supported single cell by YSZ electrolyte (10-${\mu}m$-thick) with a porous CGO interlayer between the cathode and the electrolyte to avoid undesired interfacial reactions exhibited 1,517 $mWcm^{-2}$ at $800^{\circ}C$. The unique composition of $La_1Sr_3Fe_6O_{13}$ with low thermal expansion coefficient and higher electrochemical properties could be a good cathode candidate for intermediate temperature SOFCs with CGO and YSZ electrolyte.

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