Jang, Byung-Koog

Kim, Hyung-Tae

Kim, Seongwon

Kwon, Chang-Sup

Lee, Sung-Min

Oh, Yoon-Suk

English

Engineering Conferences International

Engineering Conferences InternationalECI Digital ArchivesUltra-High Temperature Ceramics: Materials ForExtreme Environmental Applications II ProceedingsSpring 5-17-2012Microstructures and thermal conductivities of hot-pressed ZrB2-SiC ceramics with a variety of SiCsourcesSeongwon KimEngineering Ceramic Center, Korea Institute of Ceramic Engineering and TechnologyChang-Sup KwonEngineering Ceramic Center, Korea Institute of Ceramic Engineering and TechnologySung-Min LeeEngineering Ceramic Center, Korea Institute of Ceramic Engineering and TechnologyYoon-Suk OhEngineering Ceramic Center, Korea Institute of Ceramic Engineering and TechnologyHyung-Tae KimEngineering Ceramic Center, Korea Institute of Ceramic Engineering and TechnologySee next page for additional authorsFollow this and additional works at: http://dc.engconfintl.org/uhtcPart of the Materials Science and Engineering CommonsThis Conference Proceeding is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion inUltra-High Temperature Ceramics: Materials For Extreme Environmental Applications II by an authorized administrator of ECI Digital Archives. Formore information, please contact franco@bepress.com.Recommended CitationSeongwon Kim, Chang-Sup Kwon, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, and Byung-Koog Jang, "Microstructures andthermal conductivities of hot-pressed ZrB2-SiC ceramics with a variety of SiC sources" in "Ultra-High Temperature Ceramics:Materials For Extreme Environmental Applications II", W. Fahrenholtz, Missouri Univ. of Science & Technology; W. Lee, ImperialCollege London; E.J. Wuchina, Naval Service Warfare Center; Y. Zhou, Aerospace Research Institute Eds, ECI Symposium Series,(2013). http://dc.engconfintl.org/uhtc/19AuthorsSeongwon Kim, Chang-Sup Kwon, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, and Byung-Koog JangThis conference proceeding is available at ECI Digital Archives: http://dc.engconfintl.org/uhtc/19Microstructures and Thermal Conductivities  of Hot-pressed ZrB2-SiC Ceramics  with a Variety of SiC Sources 2012. 05. 17. Seongwon KIM1, Chang-Sup KWON1, Sung-Min LEE1,  Yoon-Suk OH1, Hyung-Tae KIM1, Byung-Koog JANG2 1Engineering Ceramic Center, Korea Institute of Ceramic Engineering and Technology, Korea 2High Temperature Materials Unit, NIMS, Japan UHTCs II Contents   Introduction   Objective and Experimental    Results and Discussion   Summary and Further Work   Activities on UHTCs in Korea and KICET 2 UHTCs II Examples of UHTCs * W.G. Fahrenholtz et al., J. Am. Ceram. Soc., 90 [5] (2007) 1347 Borides, carbides, nitrides of transition metals 3 UHTCs II Oxidation Behavior of UHTCs * M. M. Opeka et al., JECerS,19 (1999) 2405                      * W. G. Fahrenholtz et al., JACerS, 90 [5] (2007) 1347  Excellent oxidation resistance compared to carbides (nitrides)     B2O3 passivation layer up to 1200oC  Deterioration  of oxidation resistance over 1200oC          Addition of SiC 4 UHTCs II Mechanical Properties of ZrB2-UHTCs * W .G. Fahrenholtz et al., J. Am. Ceram. Soc., 90 [5] (2007) 1347.  Flexural strength of ZrB2-based UHTCs increases                                   with SiC addition or decrease in grain size.  5 with SiC addition with grain size UHTCs II Zener Effect : Grain Growth Inhibition 6 * S.-J. L. Kang, Sintering; Densification, grain growth and microstructure (2005). • Grain growth Inhibition by second-phase particle  Drag force of a particle    against the grain boundary movement     Fd=gbsinq x 2prcosq=prgbsin2q SiC nano-particle  L. C. Stearns, et al, J. Euro. Ceram. Soc., 10 (1992) 473. Al2O3-SiC 'Nanocomposites' UHTCs II Thermal Conductivities of UHTCs * Handbook of Ceramic Composites, Springer (2006) * Gasch et al., J. Am. Ceram. Soc., 91 (2008) 1423. * A. Paul et al, Am. Ceram. Soc. Bull., 91, (2012)  22. UHTCs II Percolation : Transport Properties Volume fraction Conductivity Percolation threshold KZrB2 : 60~80 W/mK KSiC  : 120~200 W/mK UHTCs II  Objective    : To examine the effect of SiC size        on the microstructures and thermal properties        of ZrB2-SiC ceramics   Experimental  Composition : ZrB2-x v/o SiC (x= 0, 10, 20, 30)   Powder : ZrB2 (1.88㎛, Japan New Metals Co. Ltd., Japan)                 SiC (0.5㎛, SIKA Tech., Germany)                 Nano-SiC (<100㎚, SIGMA-ALDRICH, Germany)                       PCS (Polycarbosilane, TBM tech, Korea)  Mixing : Ball mill with SiC-ball for 24hrs  Sintering : hot pressing (1900oC/2hrs) Objective and Experimental 9 UHTCs II κ(T) = ρCp(T)λ(T)  ρ : Apparent density Cp : Specific heat capacity λ  : Thermal diffusivity 10 a = 0.1388 × d2/t0.5   a : Temperature diffusivity (cm2/s) d : Thickness of the test piece(mm) T1/2 : Time 50% of the temperature increase,         measured a t the rear of the test piece (s)       Thermal diffusivity ppTEC Laser flash analysis 341effectivetruekk Specific heat capacity  Density T0.5 Thermal Conductivity Measurement △Tmax 1/2△Tmax a = 0.1388 × d2/t0.5 UHTCs II Microstructure : Hot-pressed (1900℃/2h) 11 ZrB2-10 v/o SiC ZrB2 66% TD ZrB2-20 v/o SiC ZrB2-30 v/o SiC 1st Set UHTCs II Specific Heat Capacities 12 0 200 400 600 800 1000 12000.10.20.30.40.50.60.70.80.91.0 30SiC 20SiC 10SiC ZrB2 Temperature(OC )Cp(J/gK )0 200 400 600 800 1000 1200  Temperature(OC )LFA measured NIST-JANAF 1st Set SiC ↑ UHTCs II Thermal Diffusivities 13 0 200 400 600 800 1000 1200510152025303540Thermal Diffusivity(mm2/s)  30SiC 20SiC 10SiC ZrB2 Temperature(OC )SiC ↑ 1st Set UHTCs II Thermal Conductivities 14 0 200 400 600 800 1000 120020406080Thermal Conductivity(W/mK) 30SiC 20SiC 10SiC ZrB2 Temperature(OC )1st Set UHTCs II Microstructure : Hot-Pressed (1900℃/2hrs) 15 c. ZrB2-20 v/o PCS  ZrB2-20 v/o SiC ZrB2-20 v/o nano SiC ZrB2 (1.88㎛) SiC (0.5㎛), nano-SiC(<100㎚) polycarbosilane  1900oC/2hrs hot pressing dSiC = 1.8 ㎛  dZrB2 = 3.3 ㎛  dSiC  = 1.2 ㎛ dZrB2 = 2.3 ㎛  dSiC  = 0.5 ㎛ 2nd Set UHTCs II Microstructure : ZrB2-20 v/o PCS  16 Hot-pressed (1900℃/2hrs) (direct HP with holding at 1400℃/1hr) 2nd Set UHTCs II TEM Microstructure : ZrB2-PCS, Hot-pressed 17 SiC ZrB2 ZrB2 2nd Set SiC ZrB2 UHTCs II Thermal Diffusivities 18 2nd Set 0 200 400 600 800 1000 1200101520253035Thermal Diffusivity(mm2/s) Temperature(OC ) +SiC +nano-SiC +PCSUHTCs II Thermal Conductivities 19 2nd Set 0 200 400 600 800 1000 120020406080100Thermal Conductivity(W/mK) Temperature(OC ) +SiC +nano-SiC +PCSUHTCs II Percolation Threshold 20 * D.He and N. N. Ekere, J. Phys. D: Appl. Phys. 37 (2004) 1848. ciddparticle size ratio of the insulating to conductive powder λ = 3 n = 1500 nc = 1312 p = 0.205 λ = 1 n = 1000 nc = 288 p = 0.288 particle size ratio ↑  percolation threshold UHTCs II Summary and Further Work  The effect of SiC size on the microstructures and thermal conductivities of ZrB2-SiC ceramics were examined.   Nano-SiC or PCS addition inhibited grain growth of ZrB2.    ZrB2-SiC ceramics with growth-inhibited grains showed enhanced thermal conductivities.    Optimization of SiC dispersion needs further investigation. 21 UHTCs II Thank you 22 

Microstructures and thermal conductivities of hot-pressed ZrB2-SiC ceramics with a variety of SiC sources

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Microstructures and thermal conductivities of hot-pressed ZrB2-SiC ceramics with a variety of SiC sources

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