• Title, Summary, Keyword: Thermally Grown Oxide

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Numerical Simulation for Residual Stress Distributions of Thermal Barrier Coatings by High Temperature Creep in Thermally Grown Oxide (Thermally Grown Oxide의 고온 크리프에 따른 열차폐 코팅의 잔류응력 분포에 관한 유한요소해석)

  • Jang, Jung-Chel;Choi, Sung-Churl
    • Journal of the Korean Ceramic Society
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    • v.43 no.8
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    • pp.479-485
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    • 2006
  • The residual stress changes on thermo-mechanical loading in the interface region of the Thermal Barrier Coating (TBC)/Thermally Grown Oxide (TGO)/Bond Coat (BC) were calculated on the TBC-coated superalloys using a Finite Element Method (FEM). It was found that the residual stress of the interface boundary was dependent upon mainly the oxide formation and the swelling rate of the oxide by creep relaxation. During an oxide swelling, the relaxation of residual stress which is due to creep deformation increased the TBC's life. In the case of the fine grain size of TGO scale, the TBC stresses piled up by oxide swelling could be relaxed by diffusional creep effect of TGO.

Deformation of Thermally Grown Oxide Due to Thermal Cycling (고온생성 산화막의 열피로에 의한 변형)

  • Lee, Sang-Shin;Sun, Shin-Kyu;Kang, Ki-Ju
    • Proceedings of the KSME Conference
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    • pp.415-419
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    • 2004
  • Thermal barrier systems are susceptible to instability of the thermally grown oxide(TGO) at the interface between the bond coat(BC) and the thermal barrier coating(TBC). The instabilities have been linked to thermal cycling and initial geometrical imperfections, as well as to misfit strains due to oxide growth and expansion misfit. In this work, deformation of TGO near a surface groove due to thermal cycling has been observed at high temperatures, $1100^{circ}C$, $1150^{circ}C$, $1200^{circ}C$. The effect of peak temperature and the thickness of substrate are presented.

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Low temperature electron mobility property in Si/$Si_{1-x}Ge_{x}$ modulation doped quantum well structure with thermally grown oxide

  • Kim, Jin-Young
    • Journal of Korean Vacuum Science & Technology
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    • v.4 no.1
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    • pp.11-17
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    • 2000
  • The low temperature electron mobilities were investigated in Si/$Si_{1-x}Ge_{x}$ modulation Doped (MOD) quantum well structure with thermally grown oxide. N-type Si/$Si_{1-x}Ge_{x}$ structures were fabricated by a gas source MBE. Thermal oxidation was carried out in a dry $O_2$ atmosphere at $700^{\circ}C$ for 7 hours. Electron mobilities were measured by a Hall effect and a magnetoresistant effect at low temperatures down to 0.4 K. Pronounced Shubnikov-de Haas (SdH) oscillations were observed at a low temperature showing two dimensional electron gases (2 DEG) in a tensile strained Si quantum well. The electron sheet density ($n_{s}$) of 1.5${\times}$$10^{12}$[$cm^{-2}$] and corresponding electron mobility of 14200 [$cm^2$$V^{-1}$$s^{-1}$] were obtained at low temperature of 0.4 K from Si/$Si_{1-x}Ge_{x}$ MOD quantum well structure with thermally grown oxide.

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Numerical Simulation of Effects of TGO Growth and Asperity Ratio on Residual Stress Distributions in TC-BC-TGO Interface Region for Thermal Barrier Coatings (열차폐 코팅의 TGO 성장과 형상비에 따른 TC-BC-TGO 계면에서의 잔류응력 변화에 대한 유한요소해석)

  • Jang, Jung-Chel;Choi, Sung-Churl
    • Journal of the Korean Ceramic Society
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    • v.43 no.7
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    • pp.415-420
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    • 2006
  • The residual stresses in the interface region of the Thermal Barrier Coating (TBC)/Thermally Grown Oxide (TGO)/Bond Coat (BC) were calculated on the TBC-coated superalloy samples using a Finite Element Method (FEM). It was found that the stress distribution of the interface boundary was dependent upon mainly the geometrical shape or its aspect ratio and the thickness of TGO layer, which was formed by growth and swelling behavior of oxide layer. Maximum compressive residual stress in the TBC/TGO interface is higher than that of the TGO/bond coat interface, and the tensile stress had nothing to do with change of an aspect ratio. The compressive residual stresses in the TBC/TGO and TGO/bond coat interface region increased gradually with the TGO growth.

Creep & Tensile Properties of Thermally Grown Alumina Films (열 생성 알루미나 박막의 크리프 및 인장 특성)

  • Ko, Gyoung-Dek;Sun, Shin-Kyu;Kang, Ki-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.6
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    • pp.665-670
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    • 2007
  • Alpha-phase alumina TGO(Thermally Grown Oxide) forms on the interface between zirconia top coat and bond coat of thermal barrier coating system for superalloys during exposure to high temperature over $1000^{\circ}C$. It is known to provide a good protection against hot corrosion and to cause surface failure such as rumpling and cracking due to difference in thermal expansion coefficient from the substrate metal and the lateral growth. Consequently, mechanical properties of the alumina TGO at the high temperature are the key parameters determining the integrity of TBC system. In this work, by using Fecralloy foils as the alumina forming substrate, creep tests and tensile tests have been performed with various TGO thicknesses$(h=0{\sim}4{\mu}m)$ and yttrium contents(0, 200ppm) at $1200^{\circ}C$. Displacement-time curves and load-displacement curves for each TGO thickness(h=1,2,..) were measured from the creep and tensile tests, respectively, and compared with the curves without TGO thickness(h=0). As the result, the intrinsic tensile and creep properties of TGO itself were determined.

The Analysis of N Component in Thin Oxide Film Thermally Grown by $NH_3$ Oxidation

  • Kim, Young-Cho-;Kim, Chul-Ju-
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.165-166
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    • 1994
  • The depth profiles of the as-grown and the annealed NH$_3$ oxide film in NH$_3$(7.5%)/$N_2$ ambient at 45$0^{\circ}C$ are analized . This annealing in the ambient of mixed gases removes the small quantities of N component from the NH$_3$ oxide film. In AES analysis, the NH$_3$ oxidation shows the exact stoichiometry of SiO$_2$ and a sharp slop at SiO$_2$/Si interface.

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Suppression of Macrosteps Formation on SiC Wafer Using an Oxide Layer (산화막을 이용한 SiC 기판의 macrostep 형성 억제)

  • Bahng, Wook;Kim, Nam-Kyun;Kim, Sang-Cheol;Song, Geun-Ho;Kim, Eun-Dong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.539-542
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    • 2001
  • In SiC semiconductor device processing, it needs high temperature anneal for activation of ion implanted dopants. The macrosteps, 7~8nm in height, are formed on the surface of SiC substrates during activation anneal. We have investigated the effect of thermally-grown SiO$_2$layer on the suppression of macrostep formation during high temperature anneal. The cap oxide layer was found to be efficient for suppression of macrostep formation even though the annealing temperature is as high as the melting point of SiO$_2$. The thin cap oxide layer (10nm) was evaporated during anneal then the macrosteps were formed on SiC substrate. On the other hand the thicker cap oxide layer (50nm) remains until the anneal process ends. In that case, the surface was smoother and the macrosteps were rarely formed. The thermally-grown oxide layer is found to be a good material for the suppression of macrostep formation because of its feasibility of growing and processing. Moreover, we can choose a proper oxide thickness considering the evaporate rate of SiO$_2$at the given temperature.

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Characteristics of High Temperature Oxide Thin Film Using Dichlorosilane Gas (Dichlorosilane Gas를 이용한 High Temperature Oxide Thin Film의 특성)

  • 이승석;이석희;김종철;박헌섭;오계환
    • Journal of the Korean Vacuum Society
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    • v.1 no.1
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    • pp.190-197
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    • 1992
  • In this study we have investigated physical and electrical properties of high temperature oxide (HTO) thin film using dichlorosilane (DCS) gas. This film had low etch rate and excellent step coverage, and its characteristics of Si-O bond were similar to those of thermal oxide. I-V curves also showed similar electrical properties to those of thermally grown oxide (SiO2) while time dependent dielectric breakdown (TDDB) results revealed 1/4 value of thermal oxide. However, defect density was measured to be much lower value than that of thermal oxide.

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Growth Behavior of Thermally Grown Oxide Layer with Bond Coat Species in Thermal Barrier Coatings

  • Jung, Sung Hoon;Jeon, Soo Hyeok;Park, Hyeon-Myeong;Jung, Yeon Gil;Myoung, Sang Won;Yang, Byung Il
    • Journal of the Korean Ceramic Society
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    • v.55 no.4
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    • pp.344-351
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    • 2018
  • The effects of bond coat species on the growth behavior of thermally grown oxide (TGO) layer in thermal barrier coatings (TBCs) was investigated through furnace cyclic test (FCT). Two types of feedstock powder with different particle sizes and distributions, AMDRY 962 and AMDRY 386-4, were used to prepare the bond coat, and were formed using air plasma spray (APS) process. The top coat was prepared by APS process using zirconia based powder containing 8 wt% yttria. The thicknesses of the top and bond coats were designed and controlled at 800 and $200{\mu}m$, respectively. Phase analysis was conducted for TBC specimens with and without heat treatment. FCTs were performed for TBC specimens at $1121^{\circ}C$ with a dwell time of 25 h, followed by natural air cooling for 1 h at room temperature. TBC specimens with and without heat treatment showed sound conditions for the AMDRY 962 bond coat and AMDRY 386-4 bond coat in FCTs, respectively. The growth behavior of TGO layer followed a parabolic mode as the time increased in FCTs, independent of bond coat species. The influences of bond coat species and heat treatment on the microstructural evolution, interfacial stability, and TGO growth behavior in TBCs are discussed.

Durability Evaluation of Thermal Barrier Coating (TBC) According to Growth of Thermally Grown Oxide (TGO) (TGO 성장을 고려한 열차폐코팅의 내구성평가)

  • Song, Hyun Woo;Moon, Byung Woo;Choi, Jae Gu;Choi, Won Suk;Song, Dongju;Koo, Jae-Mean;Seok, Chang-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.12
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    • pp.1431-1434
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    • 2014
  • The thermal barrier coating (TBC) applied to a gas turbine can be damaged by repeated thermal fatigue during operation, so an evaluation of its durability is needed. Thermally grown oxide (TGO) is generated inside the TBC in a high-temperature environment. The growth of TGO is known to be the main cause of damage to the TBC. Therefore, the durability of TBC should be evaluated according to the growth of TGO. In this research, Kim et al.'s work on the growth of TGO with aging was used as a basis for finite element analysis. The relationship between stress and aging was derived from the finite element analysis results. The durability of the TBC with aging was evaluated through a comparison between the results of the finite element analysis and a bond strength test.