GD ASM2004

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ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC PREPARATION AND ANALYTICAL ELECTRON MICROSCOPY OF SiC CONTINUOUS-FIBER REINFORCED SiC-BASED MATRIX COMPOSITE Goran Drazic, Sasa Novak, Nina Daneu, and Katja Mejak Department for Nanostructured Materials Jozef Stefan Institute, Ljubljana, Slovenia fusion future energy production JET ITER DEMO 1983 2015 2040 hydrogen → helium @ 10 M˙C

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tokamak fusion Fusion compared to other E sources: Almost limitless fuel supply (D in water, T from Li).  No greenhouse gas emissions. Suitable for the large-scale electricity production  Waste from fusion will not be a long-term burden  The transport of radioactive materials is not required  The system has inherent safety aspects. Very low risk of radioactive emissions to the environment toroidalnaya kamera magnitnaya The Joint European Torus (JET) (Culham, UK) Sakharov & Tamm 1950 ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC plasma @ 100 M°C

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ITER (latin: the way) ITER fusion reactor www.iter.org Fusion Energy Research for the duration of FP6 is EUR 750 million ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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first reactor wall aims CVI SiCf/SiC Eurofer Ti-alloys SiC(f)/SiC SiCf/SiC :  Low activation after fast-neutron irradiation Acceptable mechanical properties at high temperatures  Insufficient thermal conductivity (high porosity after CVI)  Insufficient gas-impermeability (high porosity or cracking)  Current technology (CVI) requires very long processing time (weeks) and is extremely expensive Improve the existing SiCf/SiC composite Impermeability: coating & impregnation SiC(f)/SiC High thermal conductivity: reduced porosity, purity, grain boundary phases High mechanical strength: high density; appropriate microstructure; nano-sized particles Short-living descendants: suitable sintering additives (LPS) Easy (low-cost) preparation: wet-ceramic processes (dispersed suspensions..) 200 um 500 um 2 mm ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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material tailoring SiC material preparation SiC – AlN – Y2O3 SiC is a highly covalent bonded compound  difficult densification Sintering: - Solid-state sintering: B, C - Liquid-phase sintering (LPS): MeO SiC-Al2O3-Y2O3 Al2O3 + SiC  Al2O(g) + SiC(g) + CO(g) SiC-AlN-Y2O3 2AlN  2Al(l) + N2(g) X-based liquid phase (ceramic-glass composite) Low-temperature densifed SiC for the specific application Grain Boundaries, secondary phase 100 nm GB sec. phase Coating techniques: adapted dip-coating (DIP) Infiltration techniques: vacuum slip infiltration (VSI) electrophoretic deposition (EPD) Suspensions: wetting, packing density, rheology ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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chemical composition fast neutron activation half-life of Pu: 24,000 years 5 half-lives are needed for 99% decay calculated gamma dose for various ITER related materials (The European Activation System: EASY-2001 Code, R. A. Forrest, UKEA-Fus-449, 2001, courtesy by Dr. George Vekinis, Institute of Materials Science, NCSR Demokritos, Athens, Greece) fission: ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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SEM SiC – AlN – Y2O3 Y2O3 amount plays an important role SEM of the SiCf/SiC interface ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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TEM SiC – AlN – Y2O3 Y2O3 rich secondary phase is crystalline intergranular phase is amorphous SEM of the SiCf/SiC interface C c-p A Si C Si C Al Y ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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STEM - HAADF SiC – AlN – Y2O3 Y2O3 rich secondary phase is uniformly distributed STEM - DF STEM - HAADF 10 nm 10 nm SiC: Zav. = 10 AlN: Zav. = 10 AlN SiC ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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liquid phase sintering simulation of SAED patterns TEM comparison of experimental and simulated SAED patterns ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC SiC – SiO2 ceramic - glass (controllable atmosphere) glass redistribution solid phase rearrangement viscous flow of glass phase

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phase composition simulation of SAED patterns TEM comparison of experimental and simulated SAED patterns ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC SiC – SiO2 ceramic - glass (controllable atmosphere)

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adapted dip coating SiC – SiO2 ceramic - glass (controllable atmosphere) adapted dip coating SEM 200 nm TEM of SiCf/SiC / matrix interface 100 mm SiCf/SiCCVI TEM ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC SiC – SiO2 SiC fiber

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ceramic – glass composite SiC (nano) – (P2O5) – Al2O3 reactive glassy phase HRTEM phase diagrams – low T liquid phase ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC 50 nm

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vacuum slip infiltration SiC (nano) – (P2O5) – Al2O3 high amount of glassy phase SEM 10 nm TEM of SiCf/SiC matrix interface ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC

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ITER starts ~ 2015 DEMO reactor ~ 2040 ? acknowledgement The work has been financed by projects: Novel processing of SiC/SiC by slip infiltration of SiC fiber pre-forms with SiC under vacuum (SINF) EURATOM, FP6, FU06-CT-2003-00323, 2004 Gas impermeable coatings for SiCf/SiC (SICOAT) EURATOM, FP6, FU06-CT-2003-00322, 2004 conclusions Vacuum-slip infiltration (VSI) is a promising alternative to chemical vapor infiltration (CVI) Limitations are given by matrix material: SiC-AlN-Y2O3 can be sintered @ 2000°C to a high density SiC-SiO2 system: volume fraction of glassy phase can be controlled with sintering atmosphere SiC-P205 can be sintered < 1500°C to a pore-free material Analysis of the SiCf/SiC matrix composite: - high-temperature mechanical properties - thermal conductivity - gas permeability Sintering: - additives for SiC (no Y, Al; nano-powders) - no shrinkage To Do list: ASM 2004 Columbus, OH USA October 18 – 21, 2004 Goran Drazic – AEM of SiCf/SiC