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권창섭,이성민,오윤석,김형태,장병국,김성원,Kwon, Chang-Sup,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae,Jang, Byung-Koog,Kim, Seongwon 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.6
Lanthanum/gadolinium zirconate coatings are deposited via suspension plasma spray with suspensions fabricated by a planetary mill and compared with hot-pressed samples via solid-state reaction. With increase in processing time of the planetary mill, the mean size and BET surface area change rapidly in the case of lanthanum oxide powder. By using suspensions of planetary-milled mixture between lanthanum or gadolinium oxide and nano zirconia, dense thick coatings with fully-developed pyrochlore phases are obtained. The possibilities of these SPS-prepared coatings for TBC application are also discussed.
열차폐코팅용 La<sub>2</sub>(Zr<sub>1-x</sub>Hf<sub>x</sub>)<sub>2</sub>O<sub>7</sub> 산화물의 상형성과 열물성
김성원,이성민,오윤석,김형태,장병국,Kim, Seong-Won,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae,Jang, Byung-Koog 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.6
As operating temperatures of engines or turbines continually increase for higher efficiency, significant amounts of researches have been focused on finding new materials, which would be alternatives to conventional yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs). In this study, phase evolution and thermo-physical properties of $La_2(Zr_{1-x}Hf_x)_2O_7$ pyrochlore systems are investigated for TBC applications. $La_2(Zr_{1-x}Hf_x)_2O_7$ systems are comprised by selecting $La^{3+}$ as A-site ions and $Zr^{4+}/Hf^{4+}$ as B-site ions in $A_2B_2O_7$ pyrochlore structures. For the developed phases in $La_2(Zr_{1-x}Hf_x)_2O_7$ compositions, thermo-physical properties such as thermal conductivity, thermal expansion coefficient are examined. The potential of these $La_2(Zr_{1-x}Hf_x)_2O_7$ compositions for TBC application is also discussed.
심병철,곽길호,이성민,오윤석,김형태,장병국,김성원,Shim, Byung-Chul,Kwak, Kil-Ho,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae,Jang, Byung-Koog,Kim, Seong-Won 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
Thermal barrier systems have been widely investigated over the past decades, in order to enhance reliability and efficiency of gas turbines at higher temperatures. Yttria-stabilized zirconia (YSZ) is one of the most leading materials as the thermal barriers due to its low thermal conductivity, thermodynamic stability, and thermal compatibility with metal substrates. In this work, rare-earth oxides with pyrochlore phases for thermal barrier systems were investigated. Pyrochlore phases were successfully formed via solid-state reactions started from rare-earth oxide powders. For the heat-treated samples, thermo-physical properties were examined. These rare-oxide oxides showed thermal expansion of $9{\sim}12{\times}10^{-6}/K$ and thermal conductivity of 1.2~2.4 W/mK, which is comparable with the thermal properties of YSZ.
희토류 저감형 란타눔 지르코네이트(La<sub>2</sub>O<sub>2</sub>-ZrO<sub>2</sub>계) 세라믹스와 열차폐코팅의 제조 및 특성평가
권창섭,이수진,이성민,오윤석,김형태,장병국,김성원,Kwon, Chang-Sup,Lee, Sujin,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae,Jang, Byung-Koog,Kim, Seongwon 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.6
Lanthanum zirconate, $La_2Zr_2O_7$, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a $La_2Zr_2O_7-4YSZ$ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.
서스펜션 플라즈마 용사로 제조된 란타눔/가돌리늄 지르코네이트 열차폐코팅의 구조와 열전도도 특성
권창섭(Chang-Sup Kwon),이성민(Sung-Min Lee),오윤석(Yoon-Suk Oh),김형태(Hyung-Tae Kim),장병국(Byung-Koog Jang),김성원(Seongwon Kim) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.6
With increase in demand for higher operating temperatures of gas turbines, extensive research efforts have been carried out to enhance the performance of thermal barrier coatings (TBCs) in the field of coating processing as well as materials. In this study, thermal barrier coatings in lanthanum/gadolinium zirconate system, which is one of the most promising candidates for replacing yttira-stabilized zirconia (YSZ) in thermal barrier coating applications, are fabricated via suspension plasma spray. Dense, 300 ~ 400 μm thick coatings of fluoritephase zirconate with modest amount of segmented microstructures are obtained by using suspension plasma spray with suspensions of planetary-milled mixture between lanthanum and/or gadolinium oxide and nano zirconia. These coatings exhibit thermal conductivities of 1.6 ~ 1.7 W/mK at 1000oC, which is relatively lower than that of YSZ.
서스펜션 플라즈마 용사법을 이용한 La₂Zr₂O<SUB>7</SUB>/YSZ 2층세라믹 열차폐코팅의 제조와 특성평가
권창섭(Chang-Sup Kwon),이수진(Sujin Lee),이성민(Sung-Min Lee),오윤석(Yoon-Suk Oh),김형태(Hyung-Tae Kim),장병국(Byung-Koog Jang),김성원(Seongwon Kim) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.6
Rare-earth zirconates, such as La₂Zr₂O7 and Gd₂Zr₂O7, have been investigated as one of the candidates for replacing conventional yttria-stabilized zirconia (YSZ) for thermal barrier coating (TBC) applications at higher turbine inlet temperatures. In this study, double-ceramic-layer (DCL) TBCs of YSZ 1st layer and La₂Zr₂O7 top coat layer are fabricated by suspension plasma spray with serial liquid feeders. Microstructures, hardness profiles, and thermal durability of DCL-TBCs are also characterized. Fabricated DCL-TBCs of YSZ/La₂Zr₂O7 exhibit excellent properties, such as adhesion strength (>25 MPa) and electrical thermal fatigue (~1429 cycles), which are comparable with TBCs fabricated by atmospheric plasma spray.
김선주(Sun-Joo Kim),이성민(Sung-Min Lee),오윤석(Yoon-Suk Oh),김형태(Hyung-Tae Kim),장병국(Byung-Koog Jang),김성원(Seongwon Kim) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.6
In order to comply with demand for high efficient gas turbines operating at higher temperatures, considerable amounts of research efforts have been performed with searching for the next-generation thermal barrier coatings (TBCs) with respect to coating materials as well as processing methods. In this study, thermal barrier coatings in the (La1-xGdx)₂Zr₂O7 system, which is one of the most versatile materials replacing yttria-stabilized zirconia (YSZ), are fabricated by suspension plasma spray with suspension made of synthesized powders via solid-state reaction. Dense, 100~400 ㎛ thick coatings of fluorite-phase zirconate with moderate amount of segmented microstructures are obtained by using suspension plasma spray. Phase formation and thermal diffusivity are characterized with coating compositions. The feasibility of (La1-xGdx)₂Zr₂O7 coatings for TBC applications is also discussed.