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

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 Si 2 Ti intermetalic cmpound while the dark regions represent pure Si SEM micrograph of the Si-Ti eutectic alloy

Manufacture of the SiC/SiCf junctions The junctions were heated at a rate of 10 0 C/min at 20 0 C above the eutectic temperature, kept at this temperature for 5 min and than cooled down to room temperature at a rate of 20 0 C/min SEM cross section of the junction brazed with Si-Ti alloy High magnification cross section 3 µm fibre Si Si 2 Ti SiC matrix

Si 2 Ti Si 3 µm SiC matrix Si 5 nm High resolution microscopy of the junction cross-section The interface between SiC-Si is atomically smooth No amorphous layer was observed Interface characterization

Nanochemistry of the junctions Si-L 23 edge C-K edge Ti-L 23 edge 50 nm SiC Si 2 Ti SiC Si 2 Ti interface SiC+Si 2 T i a) c) b) 103 eV105 eV No interdiffusion was observed

Mechanical testing Mechanical testing Behaviour at shearing test

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) Conclusions

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): , Publications 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, , Part A AUG 1, 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) 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 B. Riccardi, C. A. Nanneti. T. Petrisor, M. Sacheti, A. Orsini, Italian Patent AN: RM2001A (2001).