The development of brazing technology for SiC/SiCf composites for the fusion reactor applications

1. The development of brazing technology for SiC/SiCf composites for the fusion reactor applications Collaboration: ENEA Frascati, Italy Max Planck Institute of Microstructure Physics, Halle, Germany

2. Preparation of eutectic alloys: The Si-Ti and Si-Cr eutectic alloys were prepared in an Ar plasma furnace The as obtained alloys were remelted several times in an high preasure e-beam to obtained a fine eutectic microstructure Microstructure of eutectic alloys Light regions represent the Si2Ti intermetalic cmpound while the dark regions represent pure Si SEM micrograph of the Si-Ti eutectic alloy

3. 3 µm fibre Si SiC matrix Si2Ti Manufacture of the SiC/SiCf junctions The junctions were heated at a rate of 10 0C/min at 20 0C above the eutectic temperature, kept at this temperature for 5 min and than cooled down to room temperature at a rate of 20 0C/min SEM cross section of the junction brazed with Si-Ti alloy High magnification cross section

4. Si SiC matrix 5 nm Interface characterization High resolution microscopy of the junction cross-section Si Si2Ti SiC matrix 3 µm • The interface between SiC-Si is atomically smooth • No amorphous layer was observed

5. Si-L23 edge SiC 50 nm C-K edge Ti-L23 edge Si2Ti b) a) 103 eV 105 eV Si2Ti interface SiC+Si2Ti SiC c) Nanochemistry of the junctions • No interdiffusion was observed

6. Mechanical testing Behaviour at shearing test

7. Conclusions • eutectic Si-16Ti and Si-18Cr alloys are suitable for joining SiC/SiCf composites • the joints investigated did not show any defects in the brazing layer • no interdiffusion or formation of additional phases was observed • both Si-16Ti and Si-18Cr joints led to the conclusion that direct chemical bonds • are responsible for the adhesion with the SiC/SiCf composites • the shear tests of the joints of SiCf/SiC composites exhibit remarkable values • of the bonding strength up to 140 MPa)

8. Publications B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor. “High temperature brazing for SiC and SiCf/SiC Ceramic Matrix Composites”. Advanced SiC/SiC Ceramic Composites: development and Applications in Energy Systems, A.Kohyama, M.Singh, H-T.Lin and Y.Katoh eds, Ceramic Transactions Vol 144, The American Ceramic Society, Westerville (OH), 2002, pp 311-322. B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor.”Brazing of SiC and SiCf/SiC composites performed with 84Si-16Ti eutectic alloy:microstructure and strength”. Journal of Material Science 37 (2002) 5029-5039. B.Riccardi, C.A.Nannetti ,T.Petrisor, J.Woltersdorf, E.Pippel S.Libera L.Pilloni, “Issues of Low Activation Brazing of SiCf/SiC Composites by Using Alloys Without Free Silicon” Journal of Nuclear Materials, 329-33, 562-566 Part A AUG 1, 2004. B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor, ”Joining of SiC based ceramics and composites with Si-16Ti and Si-18Cr eutectic alloys”. International Journal of Materials and Product Technology 20 (5-6): 440-451, 2004. B. Riccardi, C. A. Nanneti. T. Petrisor, M. Sacheti, A. Orsini, Italian Patent AN: RM2001A000101 (2001).