Présentation PowerPoint - IRAMIS

Review: chemical compatibility of SiC/SiC composites with the GFR environment C. Cabet Laboratoire of Non Aqueous Corrosion, CEA Saclay, FRANCE DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Aqueuse 1 February 2 4, 2020 GFR and SiC/SiC composites Fuel assembly 850C Heat eXchanger Helium DEN/DANS/DPC/SCCME

Laboratoire dEtude de la Corrosion Non Aqueuse Introduction 2 Concepts of fuel assembly composite SiC-SiCfibers Needle concept Fission gas Actinide compound : UPuC or UPuN (56%vol of fuel) diffusion barrier refractory metal : We, Mo, Cr, Plate concept DEN/DANS/DPC/SCCME

Laboratoire dEtude de la Corrosion Non Aqueuse Introduction 3 Requirements on material for fuel assembly Containment of fuel and FP Refractory behaviour Resistance to normal operating temperatures (about 900-1200C) on extended lifetimes Confining of FP during a transient incident up to 1600C Mechanical integrity after a major accident up to 2000C High thermal conductivity (>10 W/m.K) Transparency to fast neutrons Mechanical strength and creep resistance Ability to dissolve in nitric acid Workability and assemblage Resistance to corrosion/ oxidation Best candidate material : SiCf/SiCm DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Introduction

4 GFR environment High temperature: 900-1200C + short term transitory up to 1600C (confining) and accident up to 2000C (integrity) Long in-core times No inspection, no repair Cooling gas: impure helium secondary circuit cooler H2 ? Helium + traces air, H2O Helium air, H2O refueling maintenance DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse

air, H2O, CO, CH4 ? degassing Introduction 5 SiCf/SiCm usual applications Turbines Rocket engines High temperature Oxidative atmospheres Inspection and repair Short term Aircraft engines DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Introduction

6 SiCf/SiCm compatibility with GFR physico-chemical conditions over long term ? Lifetime prediction Thermal stability Oxidation resistance Consequences of thermal aging and oxidation on the mechanical (and confining) properties Improvement strategies DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Introduction 7 Content Introduction on the GFR application SiCf/SiCm structure and fabrication

Thermal stability Oxidation propertis Composite resistance R&D needs to qualify SiC/SiC for GFR applications DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 8 SiCf/SiCm structure SiC-based matrix SiC-based fibre ~10m crack interphase (C) ~0.1m Fibres in bundle UD or 1D 2D 3D

DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse SiCf/SiCm structure and fabrication 9 SiC based matrix (SiC + Si) CVI Chemical Vapor Impregnation porosity PIP Polymer Impregnation and Porolysis preceramic pyrolysis Carbon coated fibre tows Pre-forming Polymer infiltration Pyrolysis

RMI Reative Melt Infiltration SI-HPS Slurry Infiltration and High Pressure Sintering DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse additives 10 SiC-based fibres: fabrication spinning curing Weak fibres Dense fibres PCS 1st generation cure in oxygen at T~1200C Si-C-O: 2nm SiC + C + SiCxOy

2nd generation cure by electron beam in inert atm at T~1400C Si-C + C (+ 0.5% O) 3rd generation or nearly stoichoimetric cure at 1800-2000C + optimization thin C layer on the surface DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse SiCf/SiCm structure and fabrication 11 SiC-based fibres: 3 generations Exemple of the development of the Nicalon fibres by Nipon Carbon DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 12 Interphase Compliant material Thin layer ~100nm

leaf structure pyrocarbon hex-BN Multilayer DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 13 Content Introduction on the GFR application SiCf/SiCm structure and fabrication Thermal stability Monolithic SiC Matrix Fibres Oxidation properties Composite resistance R&D needs to qualify SiC/SiC for GFR applications DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 14

SiC phase diagram Stoichoimetric no other intermediate compound SiC 2540C (SiC)(l) + C DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 15 Thermal stablity of SiC in vacuum or inert atmopshere Thermodynamic calculation SiC C + Si(g)

+ recrystalisation SiC + Si 104/T (K) Kinetic factors: SiC stable up to ~1600C DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 16 Thermal Stability of the matrix in vacuum or inert atmopsheres SiC and SiC/C matrixes are stable up to about 1600C DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 17

Thermal Stability of fibres Fibres of the 1st generation: Si-C-O Basically instable T>1200C (SiC, C, SiC2xO1-x) w SiC + x C + y CO(g) + z SiO(g) Porous C/SiC (large grains) Mass loss Decrease the creep strength 1300C 1200C Creep curves for Nicalon fibres tested in pure Ar under 0.7 GPa Mass loss for Nicalon fibres tested in pure Ar [Bodet et al. J Amer Ceram Soc 79 (1996) 2673] DEN/DANS/DPC/SCCME

Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 18 Thermal Stability of fibres Fibres of the 2nd generation: Si-C(0.5% O) Stable up to 1350C (SiC, C) + Otrace(g,s) SiC + CO(g) +C Large grains Mass loss = r Si-C-O Nicalon NL202 and Si-C Hi-Nicalon Tensile strength at (as-received and and heatYoungs treated) modulus fibres under RT of Si-C

after annealing under 100kPa Ar Hi-Nicalon (heating rate: 10C/min) [Chollon 100kPa Ar forSci tp=1hrs exept333] *tp=10hrs) et al., J Mater 32 (1997) [Chollon et al., J Mater Sci 32 (1997) 333] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 19 Thermal Stability of fibres

Nearly stoichiometric fibres Stable up to very high temperatures 1800-2000C Some SiC grain growth Good mechanical properties up to 1400-1500C Strengh as a function of temperature for 3rd gen fibres with a 250mm gauge length [Bunsell and Piant, J Mater Sci 41 (2006) 835] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Thermal stability 20 Content Introduction on the GFR application SiCf/SiCm structure and fabrication Thermal stability Oxidation properties Monolithic SiC passive oxidation

active oxidation Matrix Fibres Interphase Composite resistance R&D needs to qualify SiC/SiC for GFR applications DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 21 Oxidation of SiC at high Po2: passive oxidation Same mechanism that the oxidation of Si and other ceramics SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g) SiC(s) + 2 O2(g) = SiO2(s) + CO2(g) Very protective T>800C Monolithic SiC Linear-parabolic kinetics KP KL

( t ) 2 x x Parabolic rate constant Scale thickness linear rate constant -SiC in 1 atm air [Costello & Tressler, J Am Ceram Soc 64 (1981) 327] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC 22 Oxidation of SiC at high Po2: mechanism Ea K p B. exp

RT T>800C Monolithic SiC Growth rate = oxygen transport through the SiO2 scale T>1400C Ea 150-300 kJ/mole atomic diffusion cristobalite T<1400C Ea 300 kJ/mole molecular diffusion amorphous SiO2 90m MEB image of sintered -SiC 6hrs at 1400C in 1 atm air [Costello & Tressler, J Am Ceram Soc 64 (1981) 327] KP for the oxidation of single-crystal SiC under 0.001 atm O2 [Zheng, J Electrochem Soc 137 (1990) 854]

DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC 23 Oxidation at high Po2: polycrystalline SiC Ea K p B. exp RT Determining factors for Kp Polytype Porosity (fabrication process) Additives and impurities Formation of a silicate with a lower viscosity ( transport of O ) Modify the crystallisation HP SiC with different %Al2O3 at 1370C in 1 atm O2

[Opila & literature Jacobson,for in Materials and technology Kp from the different science type of SiC Vol.et 19, RW. Cahn et al.Soc Ed.72 (2000)] [Narushima al., J Am Ceram (1989) 1386] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC

24 Oxidation at high Po2: effect of water vapour Passive oxidation by water vapour SiC + 2 H2O(g) SiC + 3 H2O(g) T<1400C SiO2 + CH4(g) T>1400C SiO2 + CO2(g) + 3 H2(g) Higher Some water vapour increases the oxidation oxidation rate in pure water vapour rate

SiO2(s) + H2O(g) = SiO(OH)2(g) SiO2(s) + 2 H2O(g) = Si(OH)4(g) CVD-SiC at 1200C in pure CO2, pure O2 and 50%H2O/50%O2 [Opila & Nguyen., J Am Ceram Soc 81 (1998) 1949] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC 25 Oxidation of SiC at low Po2: active oxidation Same mechanism that the oxidation of Si and other ceramics SiC + O2(g) = SiO (g) + CO(g) Mass Change Volatilization ka CVD-SiC in 0.1 MPa at 1600C Po2 in Ar

Corresponding rate constant for active oxidation at two gas flow rates from 0 to 160Pa [Goto et al., Corrosion in advanced ceramics, KG Nickel Ed. (1993) 165] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC 26 Oxidation of SiC at low Po2: active oxidation Transition point between active and passive oxidation The o Th eo ry (V o lat

ilit yd iag ry ( Wa gne .) DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse r) Determining factors for transition Temperature Po2 SiC purity Vgas Total pressure

Active to passive transitions from the literature for different types of SiC [Opila & Jacobson, in Materials science and technology Vol. 19, RW. Cahn et al. Ed. (2000)] Oxidation - SiC 27 Oxidation at low Po2: effect of water vapour Active oxidation by water vapour SiC + 2 H2O(g) = SiO(g) + CO(g) + 2 H2(g) Corrosion rate active Active to passive transition Flexural strength at RT passive 1400C

PLS -SiC at 1300 and 1400C 10min in H2 with different P(H2O) [Opila & Nguyen., J Am Ceram Soc 81 (1998) 1949] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - SiC 28 Oxidation of SiC-based matrixes at high Po2 Under oxidizing atmosphere CVD-SiC (representative of CVI-SiC: Passive oxidation Thickness of the SiO2 scale Crystallisation Amorphous SiO2 CVD-SiC representative of CVI-SiC at 1000C and 100 kPa [Naslain et al. J Mater Sci 39 (2004) 7303] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - matrix

29 Oxidation of fibres: passive mode at high Po2 Growth of silica around the fibre surface SiO2 (2nd and 3rd generation fibres) Flexural strength Mass change at 1300C Mass change in Ar-25%O2 Hi-Nicalon S Hi-Nicalon Nicalon Hi-Nicalon fibres (SiC-C) in Ar-O2 at 1300C [Shimoo et al. J Mater Sci 35 (2000) 3301)] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation in Ar-O2 at 1500C [Shimoo et al., J Ceram Soc Japan 108

(2000) 1096)] Hi-Nicalon fibres (SiC-C) in Ar-25%O2 Oxidation - fibres 30 Oxidation of fibres: active mode at low Po2 Volatilization of SiO(g) SiC(s) + O2(g) = SiO(g) + CO(g) RT tensile strength + recrystallisation of SiC SiO2 Mass change at 1500C Passive oxidation Active oxidation Lox M fibres in Ar-O2 at 1500C [Shimoo et al. J Mater Sci 37 (2002) 4361)]

DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse RT tensile strength for fibres heated for SiC 20hrs in Ar-O2 at 1500C Oxidation - fibres 31 Oxidation of fibres: case of 1st generation Mass change Passive oxidation with SiO2 growth SiC + 3/2O2(g) = SiO2 + CO(g) No thermal decomposition of Si-C-O Thermal decomposition of Si-C-O SiCO = SiO(g) + CO(g) + SiC + C + recrystallisation of SiC Active oxidation SiC + O2(g) = SiO(g) + CO(g) + recrystallisation of SiC Nicalon CG fibres in Ar-O2 at 1500C

[Shimoo et al. J Amer Ceram Soc 83 (2000) 3049] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - fibres 32 Oxidation of fibres: active to passive transition As for pure SiC, there is an active to passive transition Mass change Fibres heated 72 ks in Ar-O2 at 1500C [Shimoo et al. J Mater Sci 37 (2002) 1793] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Active to passive transition Po2 for active to passive transition Oxidation - fibres 33 Oxidation of fibres: effect of water vapor at high Po 2

Ln (K p) (h-1 ) As for pure SiC, H2O increases the oxidation rate Kp for Hi-Nicalon fibres tested in N2/O2/ H2O under 100 kPa and Po2=20 kPa [Naslain et al. J Mater Sci 39 (2004) 7303] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Tensile strength of SiC fibres after 10h at 1400C in dry or wet (2%H2O) air [Takeda et al. J Nucl Mater 258-263 (1998)1594] Oxidation - fibres 34 Oxidation of the interphase at any Po2 Carbon is highly oxidizable at T>600C C + O2(g) = CO2(g) C + O2(g) = CO(g) C + 2 H2O(g) = CO2(g) + 2 H2(g)

C + H2O(g) = CO(g) + H2(g) Oxidation rate is dertermined by Temperature Po2 Total pressure Gas flow rate DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Oxidation - interphase 35 Content Introduction on the GFR application SiCf/SiCm structure and fabrication Thermal stability Oxidation properties Composite resistance Thermal aging Oxidation Improvement of the HT oxidation resistance R&D needs to qualify SiC/SiC for GFR applications

DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse 36 Thermal aging of UD SiCf/SiC (inert gas) UD-SiCf/C/PIP-SiCm Nicalon CG - 1st generation SiCO : thermal decomposition Hi-Nicalon - 2nd generation SiC-C (0.5% O) : stable up to 1350C Hi-Nicalon S - 3rd generation: nearly stoichiometric Mass change Residual oxygen Fracture strength UD SiCf/C/PIP-SiCm 3.6ks in vacuum [Araki et al. J Nucl mater 258-263 (1998) 1540] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite thermal aging 37 Thermal aging of 2D SiCf/SiC (inert gas)

2D Nicalon CG/C/CVI-SiC 1st generation SiCO : thermal decomposition SiCO = SiO(g) + CO(g) + SiC + C Interaction with the interphase Tensile strength SiO(g) + 2 C = SiC + CO(g) coarse SiC Interfacial decohesion (weakening of the fibre-matrix bounding) Partial consumption of the interphase with formation of coarse surface SiCgrains (weakening of the fibres) Total consumption of the interphase with decomposition/crystallisation (fully brittle) Stress-strain curves of 2D Nicalon/C/SiC composite at RT after thermal aging in vacuum under various conditions [Labrugre et al. J Eur Ceram Soc 17 (1997) 623] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite thermal aging 38 Passive oxidation of model SiCf/SiCm (high Po2)

Passive oxidation of fibres and matrix SiC + 3/2 O2(g) = SiO2 + CO(g) SiC + 2 O2(g) = SiO2 + CO2(g) Oxidation of the interphase C + O2(g) = CO2(g) C + O2(g) = CO(g) [Filipuzzi et al. J Amer Ceram Soc 77 (1994) 459] Model UD Nicalon/C/CVI-SiC no coating on the back and front surfaces gas phase diffusion of O2 and CO in the pore reaction of O2 with the C interphase diffusion of O2 in SiO2 and reaction with SiCf diffusion of O2 in SiO2 and reaction with Sim DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite oxidation 39 Passive oxidation of 2D SiCf/C/SiCm (high Po2) Oxidation of the interphase C+O CO2(g)

Sealing of2(g) the= pore C + oxidation O2(g) = CO(g) Passive of the matrix Passive of fibres matrix SiCoxidation + 3/2 O2(g) = SiO2and + CO(g) SiC O2(g) (g) = = SiO SiO2 ++ CO(g) SiC++3/2 2O CO2(g) 2 2 SiC + 2 O2(g) = SiO2 + CO2(g)

Mass change Residual Youngs modulus 2D Nicalon / C (=0.1 Em)/ CVI-SiC without an anti-oxidation coating heated for 35hrs in air at different temparatures [Huger et al. J Amer Ceram Soc 77 (1994) 2554] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite oxidation 40 Active oxidation of 2D SiCf/C/SiCm (low Po2) SiC-based fibers are basically instable SiC + O2(g) = SiO(g) + CO(g) + recrystallisation of SiC Strong impact on the fibre strength that provides the mechanical properties of the composite Surface flaws cracks Fully brittle no test RT tensile strength of fibres heated for

3.6ks in Ar-O2 at 1500C [Shimoo et al. J Mater Sci 37 (2002) 4361)] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite oxidation 41 Oxidation of composites under load Even for coated specimens At >0-100MPa matrix cracking At 500-1000C Jones et al. proposed a Po2/T map SiO2 on the fibres Interphase removal Fibre creep only [Jones et al. J Amer Ceram Soc 83 (2000) 1999] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse Crack velocity for model composite with

Nicalon fibres at 1100C [Jones et al. Mater Sci Eng A198 (1995) 103] composite oxidation 42 Improvement of the oxidation resistance: EBC Environmental Barrier Coating SiO22 SiC CVD SiC B-based phase Si or SiC bound coat 2B + O2 B2O3 r (MPa) Boron forms an oxide with a low melting point [Tf(B2O3)=450C] RT2BN flexural

of a 2D-Nicalon/ + Ostrength 2 B2O3 + N2(g) C/CVI-SiC with and without a CVDB4seal C + coat 4 O2after 2oxidation B2O3 + CO (g)at SiC in 2air 1000C SiB6 + 11/2 O2 3 B2O3 - SiO2 [Lowden, in Designing Ceramic Fusible boron oxide or boron silicate Interfaces II, Peteves Ed. (1993) 157] seal the porosity and the crack tips Time at 1000C in air (h) DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse

composite oxidation 43 Improvement of the oxidation resistance: self-healing matrixes Matrix with dispersed particles Applied stress Boron-based particles: B4C, BN, SiB6 Forms a healing oxide Matrix fabricated by PIP Multilayer matrix Low melting Nicalon fibresphase X: B, B4C, Si-B-C Compliant material Y: PyC, C(B), hex-BN Matrix fabricated by P-CVI: (X-Y-X-Y)n 2D-Nicalon/C/ SiC+C-B

2D-Nicalon/C/SiC Fatigue life (tensile) at 900C in air [Steyer et al., J Amer Ceram Soc 81 (1998) 2140] [Lamouroux et al., Composites Sci Technol 59(199) 1073] Time (h) DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite oxidation 44 Improvement of the oxidation resistance: alternative interphases B-based interphases: hex-BN or C(B) 2BN + O2 B2O3 + N2(g) 2B + O2 B2O3 Forms a healing oxide Multilayer interphase Oxidation resistant material: SiC, TiC

Compliant material Y: PyC, hex-BN Deposition by P-CVI: (X-Y-X-Y)n Fatigue life (4-point bending) of 2D-Nicalon/PyC or BN/CVISiC in air at 600 and 950C [Lin et al., Mater Sci Eng A321 (1997) 143)] DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse composite oxidation 45 Content Introduction on the GFR application SiCf/SiCm structure and fabrication Thermal stability Oxidation Composite resistance R&D needs to qualify SiC/SiC for GFR applications DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse

46 R&D needs for qualifing SiC/SiC composite for GFR Corpus of data on the thermal aging and oxidation behaviour of composites All studies are on a very short term! For monolithic SiC: wide ranges of temperature and P(O2) were covered Widespread results (strong dependence to SiC purity and nature) Few data on the effect of water in relevant ranges For components: some domains of temperature and P(O2) were investigated Strong influence of chemistry, structure and fabrication processes Pre-selection of candidate technologies and systematic study For whole composites: some particular studies at high P(O2) DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse conclusion

Helium +O2, H2O 900-1200C Very long times + Short time at 1600C (even 2000C) 47 R&D needs for qualifing SiC/SiC composite for GFR Choice of best state of the art materials Helium +O2, H2O Control of the environment Stoichiometric fibres Control of the Po2 (lower and upper limit) Low-porosity matrix

(+dispersed particles) or multilayer matrix Environmental Barrier Coating Multilayer interphase Control of the PH2O (upper limit) 900-1200C Very long times Limit on the temperature Design Acceptability of additives and B ? DEN/DANS/DPC/SCCME Laboratoire dEtude de la Corrosion Non Aqueuse conclusion 48

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