SIC FIBERS MECHANICAL AND MICROSTRUCTURAL BEHAVIOR UNDER ION IRRADIATION TUTORS: J.M. COSTANTINI / A. JANKOWIAK / S. MIRO Juan HUGUET-GARCIA 1rst year PhD. Student (11/2012)

06/09/2012| PAGE 2 SiC f /SiC composites under nuclear environments & Third Generation SiC fibers

1.SIC/SIC COMPOSITES IN NUCLEAR ENVIRONMENTS SiC/SiC composites: Potential candidates for fission and fusion structural applications Neutron transparency High operating temperature Mechanical Behavior 06/09/2012 | PAGE 3 Fiber influence in SiC/SiC The evolution of the fiber under irradiation play a major role in the mechanical behavior First and second generation fibers have an undesirable behavior which induces the degradation of the composite properties Third generation fibers improved behavior allow the use of SiC/SiC composites under irradiation

2. THIRD GENERATION SIC FIBERS 06/09/2012 | PAGE 4 Hi-Nicalon type S (HNS) Stoichiometry (C/Si≈1) + free Carbon at Grain Boundaries High crystallinity level (3C-SiC) Tyranno-SA3 (TSA3) Grain size  200 nm ρ= 3.1 g×cm -3 Ø~7,5  m Grain size  nm ρ= 3.0 g×cm -3 Ø~15  m Nanophased SiC microstructures are exclusive for fibers!

06/09/2012| PAGE 5 Irradiation Conditions

3.1 IRRADIATION CONDITIONS 06/09/2012 | PAGE 6 Au 3+ 4MeV Room Temperature + Dif. Doses Dif. Temperatures + 2x10 15 ion×cm -2 (~5 dpa) MiniMecaSiC: Tensile tests Real time tracking of the TSA3 fiber strain under irradiation at different temperatures and ions! No ion implantation : Damage profiles fairly homogeneous Electronic stopping power regime Low amorphization probability C irradiations  Macroscopic increase of Temperature Xe irradiations  Low heating Ex-situ  Jannus Saclay Tyranno SA3   TSA3 <R p (Xe,C) In-situ  Jannus Saclay & Ganil 6H-SiC/TSA3/HNS

3.2 IRRADIATION CONDITIONS 06/09/2012 | PAGE 7 Irradiation Conditions Au 3+ 4 MeVXe MeV C MeV Elastic Regime Inelastic Regime (SRIM 2008: Kinchin-Pease stimation E d (C)= 20 eV E d (Si)= 35 eV)

06/09/2012| PAGE 8 Ion-Irradiation effects: amorphization (Post-mortem)

4. ION-IRRADIATION EFFECTS: AMORPHIZATION & SWELLING 06/09/2012 | PAGE 9 Irradiation at low temperature: Induces SiC amorphization Induces SIC swelling Around 1000°C swelling reaches its minimum Extracted from (Snead et al, 1998)Extracted from (Snead et al, 2012)

5. IRRADIATION BEHAVIOR OF MODEL MATERIAL:  RS 06/09/2012 | PAGE 10 Caractéristiques : - Laser Nd/Yag, 532 nm, 100 mW - Spectral Resolution: ≤ 1cm -1 Raman In Via Renishaw (JANNUS-Saclay) Raman  -spectrometry permits to identify the different nuclear bonds in the sample and thus the chemical disorder  SiC dissociation and Si-Si,C-C apparition Si-C C-CSi-Si Model Material: 6H-SiC single crystal Irradiation: Au 3+ 4 MeV at RT (Ballistic damage) f D =1-A/A ref

10 13 cm cm -2 2x10 15 cm Virgin Raman Shift (cm -1 ) 6.1. ION-IRRADIATION EFFECTS: AMORPHIZATION 06/09/2012 | PAGE 11 Normalized Raman Spectra for ion-irradiated SiC (Au 4 MeV-RT) Critical amorphization dose: 6H/Tyranno SA3/Hi-Nicalon S 1x10 14 < Φ < 2x10 15 C-C bonds (graphite ) 6H-SiC Tyranno-SA3 Hi-Nicalon S

6.2. ION-IRRADIATION EFFECTS: AMORPHIZATION 06/09/2012 | PAGE 12 Critical amorphization temperature (T c ): 6H 100< Tc < 200°C Tyranno SA3 100< T c < 200°C Hi-Nicalon S 200< T c < 300°C C-C bonds (graphite) Normalized Raman Spectra for ion-irradiated SiC (Au 4 MeV-2x10 15 cm -2 )

6.3. ION-IRRADIATION EFFECTS: AMORPHIZATION 06/09/2012 | PAGE 13  Similar amorphization kinetics at RT  Tc(HNS)>Tc(TSA3,6H-SiC)  Amorphous SiC independent of its initial microstructure Role of the fiber microstructure! Carbon role? Grain Bondaries density role? Under Ballistic Regime Irradiation: (extracted from Gosset et at., 2012)

06/09/2012| PAGE 14 TSA3 Tensile tests: Irr. Temp. Dependence & flux dependence (In-situ)

7.1 TENSILE TESTS: IRRADIATION TEMPERATURE DEPENDENCE 06/09/2012 | PAGE 15 Irradiation Enhanced Creep coupled to Swelling  stress induced anisotropy (Katoh, 2013) 1000° C: SiC swelling minimum!  Creep Tests! 270°C 1000°C Unirradiated-1000°C S res =0.08% S res =0.2% S res =0.015%

7.2. CREEP TESTS: FLUX DEPENDENCE 06/09/2012 | PAGE 16 GANIL: Xe MeV  = 2,64×10 14 ions·cm °C 300 MPa Threshold Flux+Creep rate increasing with increasing ion flux

7.3 CREEP RATE AND FLUX DEPENDENCE 06/09/2012 | PAGE 17 TSA3 Fiber B 0 =1,12·10 -5 MPa -1 dpa -1 FiberT(°C)MethodDose(dpa)Particles B 0 (MPa -1 dpa -1 ) SCS-6600Torsion0.04Protons 3,00·10 -6 Sylramic600BSR0.04Protons 4,7·10 -6  C-SiC 800BSR7.7Neutrons 0,4·10 -6 Extracted from (Scholz,2000) Post-irradiation measures

7.4. IRRADIATION ENHANCEED CREEP MODELIZATION IN CERAMICS 06/09/2012 | PAGE 18 Modified Linear visco-elastic creep model: Limited studies of the IEC in ceramics  Graphite under neutron irradiation (elastic energy loss regime)  Post-mortem evalutation

7.5. IEC VISCO-ELASTIC MODEL | PAGE 19 +/-1.20E+13(7.39E+10%) +/ (12.91%) +/ (5.35%) +/ (0.56%) Assymptotic Standard Error Does Not Take in Consideration the Energy Loss Regime of the Incident particle

IRRADIATION ENHANCED CREEP MECHANISM? | PAGE 20 Irradiation Enhanced Creep mechanism? Enhanced defect mobility by electronic excitement? Excesive creep  Sub-critical crack growth  Life-Limiting condition! Dynamic annealing effect of the electronic stopping regime of swift heavy ions Thermal Spike Model Extracted from (L.Thome et al.,2013) Experimentaly (RBS/C) Extracted from (M. Backman et al.,2013) 900 keV I 900 keV I + 36 MeV W

06/09/2012| PAGE 21 Conclusions & Perspectives

CONCLUSIONS 06/09/2012 | PAGE 22 Same amorphization kinetics but different temperature dependence in comparison to the model material Amorphous SiC independent of its initial microstructure Swelling Coupled Irradiation Creep at low temperatures Creep Rate linearly dependent with the flux Threshold flux for IEC Multi Step Visco-elastic creep model for high temperature Irradiation Enhanced Creep Hints of the Influence of the damage generation nature (ratio elec/nuc) Ion-Irradiation (Energy Loss in a Ballistic regime) Ion-Irradiation (Energy Loss in an Electronic regime)

PERSPECTIVES 06/09/2012 | PAGE 23 For further irradiation campaigns, an energy degradator is devised to obtain an homogeneous damage profile within the fiber in a ballistic regime and assess the effect of the electronic/nuclear ratio in the irradiation enhanced creep. Microstructural characterization of SHI irradiation effects in SiC fibers: Raman,SEM,TEM

Thanks for your attention! Remarks? Questions? Suggestions?

Thanks to the support of JANNUS and GANIL Irradiation Facilities and its research teams which have permitted to carry out the irradiations and the Raman spectrometry